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DALTON J. Chem. Soc., Dalton Trans., 1997, Pages 181–192 181 Synthesis and reactivity of [OsH{C6H4(CH] CHH)}(CO)(PPri 3)2] and the formato compounds [Os{(E)-CH] CHPh}(Á2-O2CH)- (CO)(PPri 3)2] and [OsH(Á2-O2CH)(CO)(PPri 3)2]* María J. Albéniz,a Miguel A. Esteruelas,a Agustí Lledós,b Feliu Maseras,b Enrique Oñate,a Luis A. Oro,a Eduardo Sola a and Bernd Zeier a a Departamento de Química Inorgánica, Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza, CSIC, 50009 Zaragoza, Spain b Departament de Química, Universitat Autónoma de Barcelona, 08193 Bellaterra, Barcelona, Spain The complex [OsH{C6H4(CH]] CHH)}(CO)(PPri 3)2] has been prepared by reaction of the five-co-ordinate [Os{(E)-CH]] CHPh}Cl(CO)(PPri 3)2] with LiBun in hexane.It reacts with P(OMe)3 and CO to give [OsH{(E)- CH]] CHPh}(CO){P(OMe)3}(PPri 3)2] and [OsH{(E)-CH]] CHPh}(CO)2(PPri 3)2], while under a CO2 atmosphere the formato derivative [Os{(E)-CH]] CHPh}(h2-O2CH)(CO)(PPri 3)2] is obtained.Carbonylation of the latter leads to the monodentate formato complex [Os{(E)-CH]] CHPh}{h1-OC(O)H}(CO)2(PPri 3)2] and under a hydrogen atmosphere it affords styrene and [OsH(h2-O2CH)(CO)(PPri 3)2], which can be also prepared by reaction of [OsH2(h2-CH2]] CHEt)(CO)(PPri 3)2] with CO2. The complex [OsH(h2-O2CH)(CO)(PPri 3)2] reacts with CO, P(OMe)3 and MeO2CC]] ] CCO2Me to give [OsH{h1-OC(O)H}(CO)L(PPri 3)2] [L = CO, P(OMe)3 or MeO2CC]] ] CCO2Me]; the carbon atom of its formate ligand is attacked by NEt2H leading to the carbamato compound [OsH(h2-O2CNEt2)(CO)(PPri 3)2] and molecular hydrogen.Similarly treatment of [Os{(E)-CH]] CHPh}- (h2-O2CH)(CO)(PPri 3)2] with NEt2H afforded [Os{(E)-CH]] CHPh}(h2-O2CNEt2)(CO)(PPri 3)2]. The former complex also reacts with HBF4?OEt2, giving two different derivatives depending upon the conditions: in diethyl ether as solvent and in the presence of acetonitrile the vinyl complex [Os{(E)-CH]] CHPh}(CO)(MeCN)2- (PPri 3)2]BF4 is formed, while the carbene derivative [Os(h2-O2CH)(]] CHCH2Ph)(CO)(PPri 3)2]BF4 is obtained in chloroform.The products formed by reaction of [OsH(h2-O2CH)(CO)(PPri 3)2] with HBF4?OEt2 also depend upon the reaction conditions: in diethyl ether and in the presence of MeCN the hydrido compound [OsH(CO)- (MeCN)2(PPri 3)2]BF4 is obtained; however a mixture of products, mainly dihydrogen derivatives, is formed in CDCl3. On the basis of theoretical calculations and T1 measurements, the nature and structure of these dihydrogen compounds are discussed. In the search for homogeneous transition-metal systems effective in the synthesis of functionalized organic molecules from basic hydrocarbons, we have recently observed that treatment of the alkenylosmium(II) complexes [Os{(E)-CH]] CHR}- Cl(CO)(PPri 3)2] (R = H or Ph) with main-group organometallic compounds leads to osmium(0) species containing olefin ligands.As shown in Scheme 1 for LiMe, these transformations involve replacement of the Cl2 anion by the organic fragments of the main-group organometallic compounds, and subsequent reductive carbon–carbon coupling of the h1-carbon ligands.†,1,2 For butadiene and phenylbutadiene the osmium(0) species are stable, and do not undergo subsequent transformation.1 However, for trans-stilbene and trans-methylstyrene, the metallic centre is capable of activating a C]H bond of the substituents of the co-ordinated olefin to afford hydridoosmium(II) derivatives.2 The C]H activation products depend upon the substituents present at the alkene ligand, and can be rationalized in the light of thermodynamic and kinetic considerations. Thus, when the alkene ligand is trans-methylstyrene, the activation of an ortho position of the phenyl ring is kinetically favoured.The product of this activation, which shows an agostic interaction between the osmium centre and one of the olefinic C]H bonds, evolves to the more favoured thermo- † Non-SI unit employed: cal = 4.184 J.dynamic product [OsH(h3-CH2CHCHPh)(CO)(PPri 3)2] (Scheme 1).2 Products from the oxidative addition of the olefinic C]H bonds of trans-methylstyrene were not observed. This does not necessarily imply that the olefinic C]H activation in [Os(h2-MeCH]] CHPh)(CO)(PPri 3)2] is kinetically disfavoured with regard to C]H activation of the phenyl ring. At first glance, low activation barriers should be expected for all the possible intramolecular C]H activations in osmium(0) intermediates like [Os(h2-MeCH]] CHPh)(CO)(PPri 3)2], in view of the mild isomerization conditions and the values of the activation enthalpies reported for this kind of reaction.3 So, the non-observation of hydridoalkenyl complexes could probably be a consequence of their lower thermodynamic stability compared to the hydridophenyl derivative [OsH{C6H4[(E)-CH]] CHMe]-2}(CO)(PPri 3)2].As a continuation of our work in this field, and with the idea of casting some light on olefinic C]H activation compared to C]H activation of the ortho position of the phenyl ring in osmium(0)–phenyl–olefin species, we have now studied the reaction of [Os{(E)-CH]] CHPh}Cl(CO)(PPri 3)2] with LiBun.In this paper, we also report the synthesis and characterization of [OsH{C6H4(CH]] CHH)}(CO)(PPri 3)2], [Os{(E)-CH]] CHPh}- (h2-O2CH)(CO)(PPri 3)2] and [OsH(h2-O2CH)(CO)(PPri 3)2], and the reactivity of the formato compounds towards CO, P(OMe)3, H2, NEt2H, alkynes and HBF4.On the basis of182 J. Chem. Soc., Dalton Trans., 1997, Pages 181–192 spectroscopic data and theoretical calculations, the nature of the compounds formed by addition of HBF4 to [OsH(h2-O2- CH)(CO)(PPri 3)2] is also discussed. Results and Discussion Reaction of [Os{(E)-CH]] CHPh}Cl(CO)(PPri 3)2] with LiBun Reaction of the five-co-ordinate alkenyl complex [Os{(E)- CH]] CHPh}Cl(CO)(PPri 3)2] 1 with LiBun in hexane at room temperature gives a yellow solution from which the hydridoaryl derivative [OsH{C6H4(CH]] CHH)}(CO)(PPri 3)2] 2 (Scheme 2) was isolated as a colourless oil in quantitative yield.In the presence of a trace of water this compound evolves into the previously reported [OsH2(h2-CH2]] CHPh)(CO)(PPri 3)2].4 Scheme 1 (i ) LiMe Scheme 2 The 1H NMR spectrum in C6D6 shows in the hydrido region a triplet at d 28.01 with a P]H coupling constant of 27.3 Hz. The low-field region contains the expected resonances for the 2- vinylphenyl ligand. The PhCH]] proton appears at d 4.95 as a doublet of doublets with H]H coupling constants of 9.0 and 7.7 Hz.The olefinic proton disposed cis to this appears at d 2.74 as a doublet while that disposed trans, consistent with the agostic interaction, displays a doublet of triplets with a P]H coupling constant of 5.7 Hz. In the 13C-{1H} NMR spectrum the olefinic carbon atoms gave rise to two broad signals at d 50.5 and 46.3.The aryl carbon atom linked to the metal is observed at d 138.6 as a triplet with a P]C coupling constant of 10.0 Hz. The 31P-{1H} NMR spectrum has a singlet at d 16.7 indicating that both phosphine ligands are equivalent and mutually trans disposed. These spectroscopic data agree well with those previously reported for the related complexes [OsH{C6H4[(E)-CH]] CHR]-2}(CO)(PPri 3)2] where a Os? ? ?H agostic interaction has been confirmed by X-ray diffraction.2 Complex 2 reacts with trimethyl phosphite and carbon monoxide in hexane at room temperature to give the six-co-ordinate hydridostyryl derivatives [OsH{(E)-CH]] CHPh}(CO)L(PPri 3)2] [L = P(OMe)3 3 or CO 4] (Scheme 3) which were isolated as white solids in good yields [85 (3), 72% (4)].The IR spectrum of 3 in Nujol shows two absorptions at 2050 and 1910 cm21, which were assigned to the n(Os]H) and n(CO) vibrations, respectively. The 31P-{1H} NMR spectrum contains a triplet at d 102.4 [P(OMe)3] and a doublet at d 17.5 (PPri 3) with a P]P coupling constant of 18.6 Hz, consistent with two equivalent PPri 3 ligands both cis disposed to the trimethyl phosphite group. The relative trans position of the hydride and phosphite ligands was inferred from the hydrido signal in the 1H NMR spectrum, which appears as a doublet (JP]H = 134.4 Hz) of triplets (JP]H = 24.5 Hz) of doublets (JH]H = 1.6 Hz) at d 28.94. In the low-field region the most noticeable resonances are those corresponding to the vinyl protons of the styryl ligand, which appear at d 8.78 (OsCH]] ) and 7.03 (]] CHPh).The trans stereochemistry of the two hydrogen atoms at the C]] C double bond is supported by the value of the H]H coupling constant (18.3 Hz), which is typical for this arrangement.5 In the 13C-{1H} NMR spectrum the Ca carbon atom of the styryl ligand appears at d 143.3 as a virtual quartet with a P]C coupling constant of 13.4 Hz, while the Cb carbon atom displays at d 144.4 a doublet of triplets with P]C coupling constants of 10.1 and 4.2 Hz.The spectroscopic data obtained for complex 4 also support the structure proposed in Scheme 3. The cis relative position of the carbonyl ligands was inferred from the IR spectrum in Nujol, which shows, together with the n(Os]H) band at 1990 cm21, two strong n(CO) absorptions at 1945 and 1865 cm21, typical for mononuclear cis-dicarbonyl complexes. The Scheme 3J. Chem. Soc., Dalton Trans., 1997, Pages 181–192 183 13C-{1H} NMR spectrum also supports this proposal, showing two triplets at d 190.4 (JP]C = 5.5) and 185.5 (JP]C = 7.8 Hz) attributable to the carbonyl ligands.It also contains the expected resonances for the vinylic carbon atoms of the styryl ligand, which appear at d 142.5 (Cb) and 135.2 (Ca) as triplets with P]C coupling constants of 3.7 and 12.9 Hz, respectively. The CH groups of the phosphine ligands give a virtual triplet at d 26.2 (N = 27.6 Hz), which is characteristic of the two equivalent phosphine ligands in a trans relative position.This is consistent with the singlet at d 19.0 found in the 31P-{1H} NMR spectrum. The 1H NMR spectrum shows the hydrido resonance at d 27.13 as a triplet (JP]H = 22.0 Hz) of doublets (JH]H = 5.0 Hz). The vinylic protons of the styryl ligand appear at d 8.34 (OsCH]] ) and 7.20 (]] CHPh). The value of the Ha]Hb coupling constant (16.1 Hz) is also in agreement with the proposed E stereochemistry at the C]] C double bond.On the basis of our previous reports1,2,6 the reactions shown in Schemes 2 and 3 can be rationalized according to Scheme 4. The reaction of 1 with LiBun to give 2 most probably involves replacement of the Cl2 anion by a butyl group to afford the intermediate 5, which by subsequent hydrogen b elimination could give 6. In this context, it should be mentioned that the reaction of the five-co-ordinate complex [OsH(Cl)(CO)- (PPri 3)2] with LiBun affords [OsH2(h2-CH2]] CHEt)(CO)- (PPri 3)2].6 The reductive elimination of styrene from 6 followed by the C]H activation of the o-aryl proton should lead to 2 via the styreneosmium(0) intermediate 7.In spite of the fact that 2 is the only species detected in solution, the formation of 3 and 4 from 2 (Scheme 3) suggests that in solution complex 2 is in equilibrium with no detectable concentrations of 6. This implies that 7 is easily accessible and can give rise to activation reactions at both the olefinic and the ortho phenyl C]H bonds of the co-ordinated styrene.Although 2 is more stable than 6, the latter is more substitution labile. In addition, it should be pointed out that the olefinic C]H activation is selective, thus Scheme 4 (i ) LiBun; (ii) P(OMe)3 only the C]H bond disposed trans to the phenyl group is activated. Consistent with the high selectivity observed for the olefinic C]H activation, the reaction of the deuteriated complex [Os{(E)-CH]] CDPh}Cl(CO)(PPri 3)2] 1a with LiBun leads to [OsH{C6H4(CD]] CHH)}(CO)(PPri 3)2] 2a, and the addition of trimethyl phosphite to 2a affords [OsH{(E)-CH]] CDPh}- (CO){P(OMe)3}(PPri 3)2] 3a containing the deuterium atom at the Cb carbon atom of the styryl ligand (Scheme 5).The position of the deuterium atoms in these compounds was inferred from the 2H NMR spectra, which contain resonances at d 5.03 (2a) and 7.01 (3a). The reaction of the Ca-deuteriated complex [Os{(E)-CD]] CHPh}Cl(CO)(PPri 3)2] (1b) with LiBun, in contrast to that of Cbdeuteriated 1a, produces a mixture of four deuteriated derivatives in approximately 1 : 1 : 1 : 1 molar ratio, as shown by the 2H NMR spectrum which contains four resonances with the same intensity at d 6.52, 3.68, 2.65 and 28.02.According to the 1H NMR spectrum of 2, these resonances were respectively assigned to the complexes 2b, 2c, 2d and 2e of Scheme 6. The presence of 2b, 2d and 2e in the mixture suggests that in 2 the terminal olefinic carbon atom interacts with the hydride ligand, thus the migration of the hydride onto the olefinic terminal carbon atom and subsequent hydrogen extraction from the resulting methyl group could explain the deuterium distribution.Direct migration of the hydride from the osmium atom onto the terminal olefinic carbon atom does not seem likely in view of the mutually trans disposition of the hydride and the agostic interaction. Hence it could be proposed that the exchange process proceeds by a five-co-cordinate aryl intermediate, resulting from cleavage of the agostic interaction.Although this intermediate has not been detected by NMR spectroscopy, even at 280 8C, one should assume it, giving that at high temperatures important amounts of the relative five-co-ordinate aryl derivatives [OsH{C6H4(CH]] CHR)}(CO)- (PPri 3)2] are in equilibrium with the six-co-ordinate complexes [OsH{C6H4(CH]] CHR)}(CO)(PPri 3)2] (R = Me or Ph).2 The 2H NMR spectrum of the solution formed by addition of ca. 1 equivalent of trimethyl phosphite to the mixture of Scheme 5 (i ) LiBun; (ii) P(OMe)3184 J. Chem. Soc., Dalton Trans., 1997, Pages 181–192 Scheme 6 (i ) LiBun; (ii) P(OMe)3 complexes 2b–2e in benzene shows two broad singlets at d 8.81 and 7.46 and a doublet at d 28.88, with a P]D coupling constant of 20.2 Hz. According to the 1H NMR spectrum of 3, the singlets correspond to complexes 3b and 3c of Scheme 6, respectively, while the doublet is due to the derivative 3d.The formation of these compounds is new evidence in favour of the equilibrium between 2 and 6 (Scheme 4). Thus complex 3b is the product of the reaction of 2c with P(OMe)3, 3c is formed from 2b and 2e in the presence of the phosphite, while 3d is a result of the addition of the ligand to 2d. Synthesis and reactivity of [Os{(E)-CH]] CHPh}(Á2-O2CH)- (CO)(PPri 3)2] and [OsH(Á2-O2CH)(CO)(PPri 3)2] Passing a slow stream of carbon dioxide through a hexane solution of complex 2 affords the formato complex [Os{(E)-CH]] CHPh}(h2-O2CH)(CO)(PPri 3)2] 8 (Scheme 7).This compound was isolated at 278 8C as a microcrystalline solid in 75% yield. The formation of 8 from the reaction of 2 with CO2 is consistent with the proposal that in solution 2 is in equilibrium with no detectable concentrations of 6 (Scheme 4). Thus, the reaction Scheme 7 can be easily rationalized as the transfer of the hydride ligand from 6 to the carbon atom of the CO2 molecule.The h2 co-ordination mode of the formate ligand in complex 8 is indicated by the IR spectrum in Nujol, which contains bands at 1300 and 1560 cm21 assignable to the symmetric and asymmetric (OCO) stretching frequencies, respectively.7 The value of the asymmetric n(OCO) stretching is very similar to that of 1565 cm21 for [RuH(h2-O2CH)(PPh3)3], which contains a chelating formate ligand as confirmed by X-ray diffraction.8 This value is also in agreement with those previously reported for the complexes [MoH(h2-O2CH)(dppe)2] (dppe = Ph2PCH2CH2PPh2; 1550 cm21) 9 and [RuH(h2-O2CH){PhP[CH2CH2- CH2P(C6H11)2]2}] (1575 cm21).10 Other characteristic bands are observed at 1900 and 1540 cm21 and were assigned to the n(CO) and n(C]] C) stretchings, respectively.The 1H NMR spectrum in C6D6 shows resonances due to the triisopropylphosphine ligands and the phenyl group, along with a doublet at d 9.09 (JH]H = 15.6 Hz), a triplet at d 8.63 (JP]H = 1.9 Hz) and a doublet of triplets at d 6.46 (JH]H = 15.6, JP]H < 1 Hz), which were assigned to the Os]CH]] , O2CH and ]] CHPh protons, respectively.The most noticeable signals in the 13C-{1H} NMR spectrum are three triplets at d 174.4 (JP]C = 1.4), 137.0 (JP]C = 9.7 Hz) and 132.8 (JP]C = 2.7 Hz). The triplet at d 174.4 was assigned to the carbon atom of the formato group by comparison of this spectrum with that previously reported for the complex [Re(h2- O2CH)(dppe)2] (d 171.9).11 The other two triplets were assigned to the Ca and Cb carbon atoms of the vinyl ligand.The 31P-{1H} NMR spectrum has a singlet at d 15.6, indicating that the two phosphine ligands are equivalent and are mutually trans disposed. Carbonylation of the bidentate formato complex 8 leads to formation of the monodentate formato derivative 9 (Scheme 8). The reaction was carried out in hexane, and complex 9 was isolated as a white solid in 83% yield.In agreement with the mutually cis disposition of the two carbonyl ligands, the IR spectrum in Nujol shows two n(CO) absorptions at 2020 and 1940 cm21. Furthermore, the carboxylato region reflects the conversion of the formato group from bi- to mono-dentate. Thus the symmetric and asymmetric n(OCO) stretchings appear at 1295 and 1625 cm21 in agreement with those of other monodentate formato species.12 In the 1H NMR spectrum theJ. Chem. Soc., Dalton Trans., 1997, Pages 181–192 185 formato proton gives a singlet at d 8.11.The a-vinyl proton appears at d 8.68 as a doublet of triplets with a H]H coupling constant of 17.0 Hz and a P]H coupling constant <1 Hz, whereas the proton in b position is masked by the C6D6 signal. In the 13C-{1H} NMR spectrum the carbon atom of the formate ligand appears at d 168.4 as a singlet, while the Cb and Ca carbon atoms of the styryl ligand display triplets, at d 143.2 (JP]C = 2.3) and 140.0 (JP]C = 4.6 Hz), respectively.The 31P-{1H} NMR spectrum shows a singlet at d 9.3. Under a hydrogen atmosphere complex 8 quantitatively yields styrene and the hydridoformato complex [OsH(h2-O2- CH)(CO)(PPri 3)2] 10,13 which can be also prepared in 82% yield by bubbling carbon dioxide through a hexane solution of the dihydrido complex [OsH2(h2-CH2]] CHEt)(CO)(PPri 3)2] 11 (Scheme 9). As for 8, the bidentate formate ligand of 10 is converted into a monodentate group by carbonylation. Thus, the reaction of 10 with carbon monoxide affords [OsH{h1-OC- (O)H}(CO)2(PPri 3)2] 12.Similarly, the addition of a stoichiometric amount of P(OMe)3 to a hexane solution of 10 yields [OsH{h1-OC(O)H}(CO)}(CO){P(OMe)3}(PPri 3)2] 13 (Scheme 10). The behaviour of 10 towards carbon monoxide contrasts to that previously reported for the related ruthenium compound [RuH(h2-O2CH)(PPh3)3], which reacts with CO to give [RuH2- (CO)(PPh3)3] and CO2.8 Complex 12 was isolated as a white solid in 82% yield.The monohapto nature of the formate ligand is supported by the values of the symmetric and asymmetric n(OCO) stretchings, in the IR spectrum in Nujol, which appear at 1370 and 1643 cm21 respectively. In the 2000 cm21 region the spectrum shows three Scheme 8 Scheme 9 bands, at 2050, 1975 and 1915 cm21. The first band was assigned to the n(Os]H) absorption, and the other two to n(CO) absorptions, in agreement with a cis arrangement of these ligands. In the 1H NMR spectrum in C6D6 the hydride ligand appears at d 24.29 as a triplet with a P]H coupling constant of 21.0 Hz. The chemical shift of this signal is very close to that previously reported for the hydride ligand disposed trans to a carbonyl group in the complex [OsH(Cl)(CO)2- (PPri 3)2] (d 24.70).14 The proton of the formato group gives rise to a singlet at d 7.88.The 31P-{1H} NMR spectrum shows a singlet at d 29.1. Complex 13 was isolated as a white solid in 80% yield. The IR spectrum in Nujol shows the symmetric and asymmetric n(OCO) stretchings at 1380 and 1650 cm21. The 31P-{1H} NMR contains a triplet at d 102.9 [P(OMe)3] and a doublet at d 20.8 (PPri 3).The value of the P]P coupling constant is 17.9 Hz. The proposed trans disposition of hydride and phosphite ligands is supported by the 1H NMR spectrum in C6D6, which contains a doublet of triplets at d 26.30, with P]H coupling constants of 149.0 and 23.8 Hz. The proton of the formato group appears at d 8.37 as a singlet.Attempts to prepare complex 8 by reaction of 10 with phenylacetylene were unsuccessful. Complex 10 is not only inert towards phenylacetylene but also towards cyclohexylacetylene and methyl propiolate. However, addition of the stoichiometric amount of methyl acetylenedicarboxylate to a hexane suspension of 10 leads to a white solid in 80% yield, which was characterized as the p-alkyne compound [OsH{h1-OC(O)H}(h2- MeO2CC]] ] CCO2Me)(CO)(PPri 3)2] 14. The p co-ordination of the alkyne is strongly supported by the IR spectrum of 14 in Nujol which shows a strong absorption at 1880 cm21, characteristic of a n(C]] ] C) vibration.15 Furthermore, the spectrum contains bands at 2040, 1955 and 1710 cm21, which were assigned to v(Os]H), n(CO) (carbonyl ligand) and n(CO) (CO2Me groups of the alkyne), along with the asymmetric and symmetric n(OCO) vibrations of the monodentate formate ligand, at 1620 and 1375 cm21 respectively.According to the 1H, 13C-{1H} and 31P-{1H} NMR spectra of complex 14, in solution, this compound partially dissociates the alkyne (Scheme 11). At room temperature in C6D6 the 14 : 10 molar ratio is 1 : 1.Characteristic signals for 14 in the 1H NMR spectrum are two singlets at d 7.63 and 3.74, and a triplet with a P]H coupling constant of 28.3 Hz at d 22.28. The singlets were assigned to the O2CH and CO2CH3 protons, respectively, and the triplet to the hydride ligand. The chemical shift of this ligand agrees well with that previously reported for the complex [OsH(Cl)(h2-MeO2CC]] ] CCO2Me)(CO)(PPri 3)2] (d 22.80), where a trans disposition of the hydride and p-alkyne ligands has also been proposed.16 In contrast to the behaviour of the related chloro-derivative, insertion of the alkyne into the osmium–hydride bond of 14 is not observed. In the 13C-{1H} Scheme 10186 J.Chem. Soc., Dalton Trans., 1997, Pages 181–192 NMR spectrum the acetylenic carbon atoms appear at d 107.3 as a triplet with a P]C coupling constant of 3.3 Hz.The resonance due to the carbon atom of the formato group is observed at d 166.2, as a triplet with a P]C coupling constant of 5.3 Hz. A singlet at d 30.8 in the 31P-{1H} NMR spectrum is also characteristic of 14. The carbon atom of the formate ligand of complex 10 is an electrophilic centre susceptible to attack by nucleophiles. Addition of 1 equivalent of diethylamine to a NMR tube containing a C6D6 solution of 10 yields, after 1 h at 60 8C, the carbamato derivative [OsH(h2-O2CNEt2)(CO)(PPri 3)2] 15 in quantitative yield, (Scheme 12).The 1H NMR spectrum of 15 exhibits two quartets at d 3.14 and 3.02 and two triplets at d 0.95 and 0.91, corresponding to two inequivalent ethyl groups. The inequivalence of the ethyl groups of the carbamate ligand indicates that the molecule has no mirror plane of symmetry containing the P]Os]P unit, in agreement with the structure shown. The hydride ligand appears at d 220.37 as a triplet with a P]H coupling constant of 16.2 Hz.In the 13C-{1H} NMR spectrum the ethyl groups display four singlets, two for the CH2 carbon atom at d 39.3 and 39.0 and two for the CH3 carbon atoms at d 14.2 and 14.2. The central carbon atom of the carbamato group appears at d 165.4. The chemical shift of this resonance compares well with those previously reported for related compounds (d 170–160).17 The 31P-{1H} NMR spectrum shows a singlet at d 38.4.The 1H, 13C-{1H} and 31P-{1H} NMR spectra of the solution formed by addition of ca. 1 equivalent of diethylamine to complex 8 in C6D6 show, after 3 h at room temperature, the presence of styrene and resonances that were assigned to the complexes 8(41), 10(10), 15(12) and the styrylcarbamato derivative [Os{(E)-CH]] CHPh}(h2-O2CNEt2)(CO)(PPri 3)2] 16 (37%), by comparison of these spectra with those recorded for 8, 10 Scheme 11 Scheme 12 and 15. After 24 h at room temperature the composition consists of only 15(60) and 16(40%).Bubbling molecular hydrogen through this solution does not affect the 15 : 16 molar ratio, even after 6 h. These results can be rationalized according to schemes 9, 12 and 13. As for 10, the carbon atom of the formate ligand of 8 is susceptible to attack by nucleophiles. Thus, the reaction of this complex with diethylamine leads to the styrylcarbamato derivative 16 (Scheme 13). The molecular hydrogen generated from the nucleophilic substitution reacts with 8 to give 10 and styrene (Scheme 9).Complex 10 then reacts further with the amine to afford 15 and molecular hydrogen (Scheme 12). In the 1H NMR spectrum the most noticeable signals for complex 16 are those corresponding to the styryl and carbamate ligands. The vinyl protons of the styryl ligand display a doublet at d 9.37 with a H]H coupling constants of 15.6 Hz, and a doublet of triplets at d 6.57 with a P]H coupling constant < 1 Hz, assigned to the a- and b-proton respectively.Similarly to 15, the ethyl protons of the carbamate ligand appear as two quartets at d 3.14 and 3.04 and two triplets at d 0.93 and 0.91. In the 13C-{1H} NMR spectrum the central carbon atom of the carbamato group appears as a singlet at d 165.0, the a-carbon atom of the styryl ligand appears at d 138.7 as a triplet with a P]C coupling constant of 7.7 Hz, and the b-carbon atom gives rise to a broad singlet at d 132.3. A singlet at d 16.1 in the 31P-{1H} NMR spectrum is also characteristic of 16.Protonation of complexes 8 and 10 Complex 8 also reacts with HBF4?OEt2, leading to different derivatives depending upon the conditions. In diethyl ether as solvent one of the two oxygen atoms of the formate ligand undergoes electrophilic attack of the proton of the acid to give the unsaturated [Os{(E)-CH]] CHPh}(CO)(PPri 3)2]+ fragment, which can be trapped as [Os{(E)-CH]] CHPh}(CO)(MeCN)2- (PPri 3)2]BF4 17 in the presence of acetonitrile.While, in chloroform as solvent, electrophilic attack of the proton takes place at the b-carbon atom of the styryl ligand. In this case the compound formed is the carbene derivative [Os(h2-O2CH)- (]] CHCH2Ph)(CO)(PPri 3)2]BF4 18 (Scheme 14). Complex 17 was isolated as a white solid in 80% yield. The IR spectrum in Nujol shows the absorption due to the [BF4]2 anion with Td symmetry, at about 1100 cm21 indicating that this anion is not co-ordinated to the metal.Consistent with the mutually cis disposition of the acetonitrile ligands, the 1H NMR spectrum shows two singlets for their protons, at d 2.68 and 2.57. The a-vinylic proton of the styryl group appears at d 8.28 as a doublet with a H]H coupling constant of 17.3 Hz, while the b-vinylic proton appears at d 6.42 as a doublet of triplets with a P]H coupling constant 1 Hz. In the 13C-{1H} NMR spectrum the acetonitrile ligands also give rise to two singlets at d 126.0 and 125.5.The Ca and Cb atoms of the vinyl Scheme 13J. Chem. Soc., Dalton Trans., 1997, Pages 181–192 187 ligand display triplets at d 132.7 and 136.2, with P]C coupling constants of 8.9 and 3.0 Hz, respectively. The 31P-{1H} NMR spectrum contains a singlet at d 3.1. Complex 18 was isolated as a green oil in quantitative yield, and was characterized in solution by IR, 1H, 13C-{1H} and 31P-{1H} NMR spectroscopy. The IR spectrum in dichloromethane shows two bands at 1560 and 1355 cm21, supporting the bidentate co-ordination of the formato group.The presence of a carbene ligand was inferred from the 1H and 13C-{1H} NMR spectra in CDCl3. The 1H NMR spectrum contains at d 17.63 a triplet with a H]H coupling constant of 6.1, and at d 3.52 a doublet with the same H]H coupling constant. These resonances were assigned to the Os]] CH and CH2Ph protons, respectively. The proton of the formato group appears at d 9.19, as a singlet. In the 13C-{1H} spectrum the Ca carbon atom of the carbene ligand appears at d 290.8 as a broad signal.The carbon atom of the formato group gives rise to a singlet at d 168.7. The 31P-{1H} NMR spectrum contains a singlet at d 38.3. The reaction of complex 10 with HBF4?OEt2 also leads to different derivatives depending upon the conditions. Similarly to 8, in diethyl ether as solvent, the reaction produces a very unsaturated [OsH(CO)(PPri 3)2]+ fragment, which can be trapped with acetonitrile to afford the previously reported compound [OsH(CO)(MeCN)2(PPri 3)2]BF4 19.18 However, in CDCl3 the electrophilic attack of the proton occurs at the Scheme 14 (i) HBF4, MeCN, Et2O; (ii) HBF4, CHCl3 Fig. 1 Proton NMR spectrum (CDCl3) of the mixture resulting from the reaction of [OsH(h2-O2CH)(CO)(PPri 3)2] 10 with HBF4?OEt2 in the hydrido region, at different reaction times hydride ligand and/or at the metal to give a mixture of products. Fig. 1 shows the high-field region of the 1H NMR spectrum at different reaction times.After 5 min the spectrum mainly contains four signals A–D. After 45 min signal D disappears, and the B:A intensity ratio increases. A variabletemperature 300 MHz T1 study of the peaks A–C gave T1(min) values of 17, 21 and 260 ms, respectively, suggesting that A and B correspond to dihydrogen compounds, while C is due to a dihydrido derivative. The correlation of the spectra shown in Fig. 1 with the 31P-{1H} NMR spectra registered at the same reaction times (5, 20 and 45 min) indicates that the signals A and B are related with singlets at d 25.6 and 41.8, respectively, while the D may be related with a broad resonance centred at d 35.6.The signal C could not be clearly correlated. In order to cast light on the nature and structure of the products of the reaction of complex 10 with HBF4?OEt2 in CDCl3, ab initio theoretical calculations have been carried out. They were performed at the Møller–Plesset Perturbatia (MP)2 and 4 levels using PH3 in place of the triisopropylphosphine ligand.The geometry optimizations were carried out at the MP2 level. Fig. 2 shows a plot of the optimized structure for the complex [OsH(h2-O2CH)(CO)(PH3)2] 10a. The most significant parameters are included in Table 1. As expected the co- Fig. 2 The MP2 optimized geometry of the reactant species [OsH(h2-O2CH)(CO)(PH3)2] 10a. Hydrogen atoms of phosphine ligands are omitted for clarity Table 1 Selected geometrical parameters (Å and 8) of the MP2 optimized structures.The atom numbering is that defined in Figs. 2 and 3; X corresponds to a point at the centre of the straight line between H(10) and H(11) Structure 10a 20a 21a 22a 23a Os(1)]P(2) 2.404 2.460 2.482 2.484 2.489 Os(1)]P(3) 2.404 2.460 2.476 2.502 2.495 Os(1)]C(4) 1.837 1.876 1.839 1.936 1.889 Os(1)]O(6) 2.419 2.156 1.979 1.987 2.000 Os(1)]O(8) 2.253 2.244 3.390 3.463 3.460 Os(1)]H(10) 1.588 1.688 1.728 1.594 1.603 Os(1)]H(11) — 1.688 1.729 1.594 1.592 Os(1)]X — 1.623 1.669 0.810 1.400 H(10)]H(11) — 0.930 0.894 2.745 1.534 P(2)]Os(1)]P(3) 172.4 169.3 170.1 170.3 165.2 P(2)]Os(1)]C(4) 93.6 93.0 90.8 103.6 98.2 P(2)]Os(1)]O(6) 89.9 84.9 89.9 93.9 90.6 P(2)]Os(1)]X — 94.5 93.8 53.3 96.7 C(4)]Os(1)]O(6) 114.1 104.8 110.6 162.5 150.9 C(4)]Os(1)]X — 94.5 93.8 53.3 96.7 C(4)]Os(1)]O(6) 114.1 104.8 110.6 162.5 150.9 C(4)]Os(1)]X — 89.0 88.2 50.3 81.9 O(6)]Os(1)]X — 166.2 160.8 147.2 127.0 H(10)]Os(1)]H(11) — 32.0 30.0 118.9 57.4188 J.Chem. Soc., Dalton Trans., 1997, Pages 181–192 ordination geometry around the metal is distorted octahedral. The distortion is due to the small angle of the bidentate formato group [O(6)]Os(1)]O(8) 57.98]. Since protonation of complex 10 leads a mixture of products containing dihydrogen and dihydride ligands, all the reasonable dihydrogen and dihydrido structures containing the formate ligand co-ordinated in mono- or di-hapto manner, and with the phosphine ligands mutually trans disposed, were considered.* The MP2 optimizations lead to the species 20a–23a, presented in Fig. 3. The most significant geometrical parameters are collected in Table 1, with MP2 and MP4 relative energies in Table 2. The theoretical calculations suggest that two dihydrogen and two dihydrido derivatives are possible. Thermodynamically, the most stable complex is the six-co-ordinated h2-formato (dihydrogen) 20a, where the two hydrogen atoms of the dihydrogen ligand are separated by 0.930 Å. Its stability is in agreement with its nature as a d6 ML6 complex.According to Fig. 1, the most stable species displays signal B, which shows a T1(min) value of 21 ms at 300 MHz. This value corresponds to a hydrogen–hydrogen distance of 0.94 Å (fast spinning).† So we propose that signal B is characteristic of the h2-formato (dihydrogen) cation [Os(h2-O2CH)(h2-H2)(CO)(PPri 3)2]+ 20. Signal A is also characteristic of a dihydrogen derivative, its T1(min) value (17 ms at 300 MHz) corresponding to a hydrogen– hydrogen distance of 0.90 Å (fast spinning).Species 21a has a square-pyramidal structure (Fig. 3) with a larger distortion corresponding to the C(4)]Os(1)]O(6) angle (110.68, Table 1). It is a dihydrogen complex [H(10)]H(11) 0.894 Å], and its nature as a monodentate formate compound is indisputable [Os(1) ? ? ? O(8) 3.390 Å]. Thus, at first glance, one could propose that signal A corresponds to a five-co-ordinate h1-formato (dihydrogen) derivative with the carbonyl group in the apical position.However, it should be noted that (i) 20a is 15.91 kcal mol21 more stable than 21a and (ii) a high kinetic barrier would not be expected for the h1-formato æÆ h2-formato transformation. Hence, we believe that this signal corresponds to a six-coordinate h1-formato (dihydrogen) species, stabilized by coordination of a diethyl ether molecule (21), originating from the HBF4?OEt2 solution used in the reaction.The co-ordination of the ether molecule cis to the dihydrogen ligand should increase the kinetic barrier for the h1-formato æÆ h2-formato transformation without affecting the metal–dihydrogen interaction and, therefore, the hydrogen–hydrogen separation. Signal C is characteristic of a dihydrido derivative containing non-equivalent phosphine ligands. The T1(min) value for this signal is 260 ms at 300 MHz. Complex 22a is not octahedral [H(10)]Os(1)]H(11) 118.98] but a bicapped tetrahedron, a coordination polyhedron characteristic for d4 ML6 complexes.21,22 The bicapped tetrahedron 22a contains non-equivalent phosphine ligands [Os(1)]P(2) 2.484, Os(1)]P(3) 2.502 Å], and they Table 2 The MP2 and MP4 relative energies (kcal mol21) of different isomers of [OsH2(O2CH)(CO)(PH3)2]+. Geometries are optimized at the MP2 level Geometry 20a 21a 22a 23a MP2 0.00 15.97 12.00 11.87 MP4 0.00 15.91 12.42 12.36 * The mutually trans disposition for the phosphine ligands is a reasonable assumption in the view of the steric demands of the PPri 3 ligand.Trigonal-bipyramidal geometries were not considered because they are not likely in d6 ML5 species like this one.19 † At the temperature of minimum T1, t = 0.62/2pn, and the equation for dipolar relaxation simplifies to rH]H = 4.611 (T1min/n)1-6 for rapid rotation (n/MHz, T1/s).20 cannot be interconverted through reorientation of the formate ligand. The hydrogen–hydrogen separation in 22a is 2.745 Å.For this distance a T1(min) value of 224 ms at 300 MHz‡ is expected. The experimental properties of signal C seem well suited to that inferred for 22a from the theoretical calculations. So, we correlate it to the derivative [OsH2{h1-OC(O)- Fig. 3 The MP2 optimized geometries of the dihydrogen complexes [Os(h2-O2CH)(h2-H2)(CO)(PH3)2]+ 20a and [Os{h1-OC(O)H}(h2-H2)- (CO)(PH3)2]+ 21a and of the dihydrido complexes [OsH2{h1-OC(O)H}- (CO)(PH3)2]+ 22a and 23a.Hydrogen atoms of phosphine ligands are omitted for clarity ‡ It has been recently shown that, for polyhydrido complexes, T1(min) can be calculated by using internuclear distances obtained from neutron, X-ray diffraction 23a and theoretical studies.23bJ. Chem. Soc., Dalton Trans., 1997, Pages 181–192 189 H}(CO)(PPri 3)2]+ 22, which may have the structure shown in Fig. 3. Signal D rapidly disappears, and it cannot be studied. It may be assigned to species 23a.The reactions of complex 10 with HBF4?OEt2 to give 19, and 20, and 21, as well as the protonations of 8 to afford 17 and 18, can be rationalized via the intermediates 24 and 25. The electrophilic attack of the proton could initially take place at one of the two oxygen atoms of the formate ligands of both 10 and 8. Thus, in the presence of acetonitrile the displacement of the resulting formic acid by the nitrogen-donor ligand should yield 19 and 17, while in the absence of this ligand the transfer of the proton from the oxygen atom to the hydride and vinyl ligands could afford the thermodynamically more stable compounds 21 and 18.Conclusion This study has shown that the reaction of the five-co-ordinate compound [Os{(E)-CH]] CHPh}Cl(CO)(PPri 3)2] 1 with LiBun leads to [OsH{C6H4(CH]] CHH)}(CO)(PPri 3)2] 2 in equilibrium with the co-ordinatively unsaturated complex [OsH{(E)-CH]] CHPh}(CO)(PPri 3)2] 6. Complexes 2 and 6 are connected by the osmium(0) intermediate [Os(h2-CH2]] CHPh)(CO)(PPri 3)2] 7, which gives rise to C]H activation reactions in the terminal olefinic and the ortho-phenyl C]H bonds of the co-ordinated styrene.Complex 6 cannot be detected in solution, most probably due to the higher stability of its 18-electron isomer 2. However, the reactivity of 2 can easily be understood as a result of the reactions of the more labile isomer 6. Thus, the formato complex [Os{(E)-CH]] CHPh}(h2-O2CH)(CO)(PPri 3)2] 8, formed by passing a slow stream of carbon dioxide through a hexane solution of 2, can be rationalized from the insertion of the CO2 molecule into the Os–H bond of 6.Hydrogenation of 8 gives styrene and the hydrido complex [OsH(h2-O2CH)(CO)- (PPri 3)2] 10. The reactivity of complexes 8 and 10 towards CO, NEt2H and HBF4 has been also studied. By carbonylation, the bidentate formate ligand of these compounds becomes monodentate. In the presence of diethylamine, the central carbon atoms of the bidentate formato groups undergo nucleophilic attack affording the carbamato derivatives [OsR(h2-O2CNEt2)(CO)- (PPri 3)2] (R = H 15 or CH]] CHPh 16).The reactions of 8 and 10 with HBF4 lead to different derivatives depending upon the conditions. In diethyl ether as solvent the formato groups of both compounds undergo electrophilic attack by protons to give fragments of the type [OsR(CO)(PPri 3)2]+ (R = H or CH]] CHPh), which can be trapped in the presence of acetonitrile.In chloroform, complex 8 leads to the carbene [Os(h2-O2CH)(]] CHCH2Ph)(CO)(PPri 3)2]+ 18, and 10 gives a mixture of products, mainly dihydrogen derivatives. On the basis of theoretical calculations and T1 measurements, we propose that these derivatives could be the cations [Os(h2-O2- CH)(h2-H2)(CO)(PPri 3)2]+ 20 and [Os{h1-OC(O)H}(h2-H2)- (Et2O)(CO)(PPri 3)2]+ 21. Experimental All reactions were carried out with rigorous exclusion of air by using Schlenk-tube techniques.Solvents were dried by known procedures and distilled under argon prior to use. Physical measurements Infrared spectra were recorded as Nujol mulls on polyethylene sheets or NaCl cell windows using a Perkin-Elmer 883 or a Nicolet 550 spectrometer, NMR spectra on a Varian UNITY 300 or Brucker 300 AXR spectrometer. Proton and 13C-{1H} chemical shifts were measured relative to partially deuteriated solvent peaks but are reported relative to tetramethylsilane, 31P-{1H} chemical shifts relative to external 85% H3PO4.Coupling constants J and N []] J(PH) + J(P9H) for 1H, J(PC) + J(P9C) for 13C] are given in Hz. The C, H and N analyses were carried out in a Perkin-Elmer 2400 CHNS/O analyser. The starting materials [Os{(E)-CH]] CHPh}Cl(CO)(PPri 3)2] 1 and [OsH2(h2-CH2]] CHEt)(CO)(PPri 3)2] 11 were prepared by published methods.5,6 The deuteriated complexes [Os{(E)-CH]] CDPh}Cl(CO)(PPri 3)2] 1a and [Os{(E)-CD]] CHPh}Cl(CO)- (PPri 3)2] 1b were prepared by reaction of [OsD(Cl)(CO)(PPri 3)2] with PhC]] ] CH and [OsH(Cl)(CO)(PPri 3)2] with PhC]] ] CD, respectively.Preparations [OsH{C6H4(CH]] CHH)}(CO)(PPri 3)2] 2. A solution of [Os{(E)-CH]] CHPh}Cl(CO)(PPri 3)2] 1 (100 mg, 0.15 mmol) in hexane (5 cm3) was treated with LiBun (0.01 cm3, 1.6 mol dm23 solution in hexane) and stirred during ca. 5 min at room temperature. The mixture changed from dark blue to pale yellow. The resulting suspension was filtered through Kieselguhr and the filtrate was dried in vacuo to give a colourless oil.NMR (C6D6, 20 8C): 1H, d 7.26 (d, JH]H = 7.1, 1 H, HPh), 7.03 (t, JH]H = 7.1, 1 H, HPh), 6.90 (t, JH]H = 7.1, 1 H, HPh), 6.56 (d, JH]H = 7.1, 1 H, HPh), 4.95 (dd, JH]H = 9.0, J 7.7, 1 H, CH]] ), 3.71 (dt, JH]H = 9.0, JP]H = 5.7, 1 H, ]] CH2), 2.74 (d, JH]H = 7.7, 1 H, ]] CH2), 2.15 (m, 6 H, PCHCH3), 1.05 (dvt, N = 13.5, JH]H = 6.3, 36 H, PCHCH3) and 28.01 (t, JP]H = 27.3, 1 H, OsH); 13C- {1H}, d 187.9 (t, JP]C = 8.0, CO), 152.2 (t, JP]C = 2.0, CPh), 138.6 (t, JP]C = 10.0, CPh), 135.8 (br, CHPh), 126.1 (br, CHPh), 122.9 (br, CHPh), 121.0 (br, CHPh), 50.5 (br, CH]] ), 46.3 (br, ]] CH2), 26.6 (vt, N = 26.4 Hz, PCHCH3), 20.1 (s, PCHCH3) and 20.0 (s, PCHCH3); 31P-{1H}, d 16.7 (s).[OsH{(E)-CH]] CHPh}(CO){P(OMe)3}(PPri 3)2] 3. A solution of complex 1 (100 mg, 0.15 mmol) in hexane (5 cm3) was treated with LiBun (0.01 cm3, 1.6 mol dm23 solution in hexane) and stirred during ca. 5 min at room temperature.The resulting suspension was filtered through Kieselguhr and treated with P(OMe)3 (17 ml, 0.15 mmol). After 30 min of reaction a white solid was formed, decanted, washed with hexane and dried in vacuo. Yield 95.7 mg (85%) (Found: C, 47.5; H, 8.2. Calc. for C30H59O4OsP3: C, 47.0; H, 7.75%). IR (Nujol, cm21): n(Os]H) 2050s, n(CO) 1910s, n(C]] C) 1540m. NMR (C6D6, 20 8C): 1H, d 8.78 (tq, JH]H = 18.3, JP]H = 18.3, JH]H 1.6 Hz, JH]H = 1.6, 1 H, OsCH]] CHPh), 7.46 (d, JH]H = 7.3, 2 H, o-H of Ph), 7.23 (t, JH]H = 7.3, 2 H, m-H of Ph), 7.03 (dt, JH]H = 18.3, JP]H = 2.5, 1 H, OsCH]] CHPh), 6.96 (t, JH]H = 7.3, 1 H, p-H of Ph, 3.39 (d, JP]H = 10.1, 9 H, POMe), 2.47 (m, 6 H, PCHCH3), 1.27 (dvt, N = 14.0, JH]H = 7.1 18 H, PCHCH3), 1.20 (dvt, N = 11.9,190 J.Chem. Soc., Dalton Trans., 1997, Pages 181–192 JH]H = 7.1 18 H, PCHCH3) and 28.94 (dtd, JP]H = 134.4, JP]H = 24.5, JH]H = 1.6, 1 H, OsH); 13C-{1H}, d 190.8 (vq, JP]C = 8.3 CO), 145.3 (t, JP]C = 2.3 ipso-C of Ph), 144.4 (dt, JP]C = 10.1, 4.2, OsCH]] CHPh), 143.3 (vq, JP]C = 13.4, OsCH]] CHPh), 128.6 (s, o-CH of Ph), 124.4 (s, m-CH of Ph), 124.0 (s, p-CH of Ph), 51.6 (d, JP]C = 8.8 POMe), 26.0 (vtd, N = 26.8, JP]C = 2.3, PCHCH3), 20.8 (s, PCHCH3) and 18.7 (s, PCHCH3); 31P-{1H}, d 102.4 (t, JP]P = 18.6 POMe) and 17.5 (d, JP]P = 18.6 Hz, PPri 3).[OsH{(E)-CH]] CHPh}(CO)2(PPri 3)2] 4. A solution of complex 1 (100 mg, 0.15 mmol) in hexane (5 cm3) was treated with LiBun (0.01 cm3, 1.6 mol dm23 solution in hexane) and stirred during ca. 5 min at room temperature. The resulting suspension was filtered through Kieselguhr and a slow stream of carbon monoxide was bubbled through it. After 30 min of reaction a white solid was formed, decanted, washed with hexane and dried in vacuo. Yield 74 mg (72%) (Found: C, 50.6; H, 8.4. Calc. for C28H50O2OsP2: C, 50.15; H, 7.55%). IR (Nujol, cm21): n(OsH) 1990s, n(CO) 1945s, 1865s, 1570m, n(C]] C). NMR (C6D6, 20 8C): 1H, d 8.34 (br d, JH]H = 16.1, 1 H, OsCH]] CHPh), 7.41 (d, JH]H = 7.3, 2 H, o-H of Ph), 7.23, (t, JH]H = 7.3, 2 H, m-H of Ph), 7.20 (d, JH]H = 16.1, 1 H, OsCH]] CHPh), 6.98 (t, JH]H = 7.3, 1 H, p-H of Ph), 2.24 (m, 6 H, PCHCH3), 1.16 (dvt, N = 13.5, JH]H = 6.9, 32 H, PCHCH3) and 27.13 (td, JP]H = 22.0, JH]H = 5.0, 1 H, OsH); 13C-{1H}, d 190.4 (t, JP]C = 5.5, CO), 185.5 (t, JP]C = 7.8, CO), 144.5 (t, JP]C = 1.9, ipso-C of Ph), 142.5 (t, JP]C = 3.7, OsCH]] CHPh), 135.2 (t, JP]C = 12.9, OsCH- ]] CHPh), 128.8 (s, o-C of Ph), 124.9 (s, m-C of Ph), 124.5 (s, p-C of Ph), 26.2 (vt, N = 27.6, JP]C = 2.3 Hz, PCHCH3) and 19.0 (s, PCHCH3); 31P-{1H}, d 19.0 (s).[OsH{C6H4(CD]] CHH)}(CO)(PPri 3)2] 2a. The complex was prepared using the procedure described for 2 (100 mg, 0.15 mmol), starting for [Os{(E)-CH]] CDPh}Cl(CO)(PPri 3)2]. NMR: 1H (C6D6, 20 8C), d 7.26 (d, JH]H = 7.1, 1 H, HPh), 7.03 (t, JH]H = 7.1, 1 H, HPh), 6.90 (t, JH]H = 7.1, 1 H, HPh), 6.56 (d, JH]H = 7.1, 1 H, HPh), 3.71 (t, JP]H = 5.7, 1 H, ]] CH2), 2.74 (s, ]] CH2), 2.15 (m, 6 H, PCHCH3), 1.05 (dvt, N = 13.5, JH]H = 6.3, 36 H, PCHCH3) and 28.01 (t, JP]H = 27.3 Hz, 1 H, OsH); 2H (C6H6, 20 8C), d 5.03 (s, CD]] ); 31P-{1H} (C6D6, 20 8C), d 17.1 (s).[OsH{(E)-CH]] CDPh}(CO){P(OMe)3}(PPri 3)2] 3a. The complex was prepared using the procedure described for 3 (100 mg, 0.15 mmol), starting for [Os{(E)-CH]] CDPh}Cl(CO)- (PPri 3)2]. NMR: 1H (C6D6, 20 8C), d 8.78 (d, JP]H = 18.3, 1 H, OsCH]] CHPh), 7.46 (d, JH]H = 7.3, 2 H, o-H of Ph), 7.23 (t, JH]H = 7.3, 2 H, m-H of Ph), 6.96 (t, JH]H = 7.3, 1 H, p-H of Ph), 3.39 (d, JP]H = 10.1, 9 H, POMe), 2.47 (m, 6 H, PCHCH3), 1.27 (dvt, N = 14.0, JH]H = 7.1, 18 H, PCHCH3), 1.20 (dvt, N = 11.9, JH]H = 7.1, 18 H, PCHCH3) and 28.94 (dt, JP]H = 134.4, 24.5, 1 H, OsH); 2H (C6H6, 20 8C), d 7.01 (s, OsCH]] CDPh); 31P-{1H} (C6D6, 20 8C), d 103.0 (t, JP]P = 18.6 POMe), 17.5 (d, JP]P = 18.6 Hz, PPri 3).[OsH{C6H3D(CH]] CHH)}(CO)(PPri 3)2] 2b, [OsH{C6H4(CH]] CDH)}(CO)(PPri 3)2] 2c, [OsH{C6H4(CH]] CHD)}(CO)(PPri 3)2] 2d and [OsD{C6H4(CH]] CHH)}(CO)(PPri 3)2] 2e.The complexes were prepared using the procedure described for 2 (100 mg, 0.15 mmol), starting from [Os{(E)-CD]] CHPh}Cl(CO)(PPri 3)2]. NMR: 1H (C6D6, 20 8C), d 7.26 (d, JH]H = 7.1, 1 H, HPh), 7.03 (t, JH]H = 7.1, 1 H, HPh), 6.90 (t, JH]H = 7.1, 1 H, HPh), 6.56 (d, JH]H = 7.1, HPh), 4.95 (br dd, JH]H = 9.0, J = 7.7, CH]] ), 3.71 (br dt, JH]H = 9.0, JP]H = 5.7, ]] CH2), 2.74 (br d, JH]H = 7.7, 1 H, ]] CH2), 2.15 (m, 6 H, PCHCH3), 1.05 (dvt, N = 13.5, JH]H = 6.3, 36 H, PCHCH3) and 28.01 (br t, JP]H = 27.3 Hz, 1 H, OsH); 2H (C6H6, 20 8C), d 6.52 (s, DPh), 3.68 (s, ]] CHD), 2.65 (s, ]] CHD) and 28.02 (s, OsD); 31P-{1H} (C6D6, 20 8C), d 17.1 (s). [OsH{(E)-CD]] CHPh}(CO){P(OMe)3}(PPri 3)2] 3b, [OsH- {(E)-CH]] CHC6H4D}(CO){P(OMe)3}(PPri 3)2] 3c and [OsD- {(E)-CH]] CHPh}(CO){P(OMe)3}(PPri 3)2 3d.The complexes were prepared using the procedure described for 3 (100 mg, 0.15 mmol), starting from [Os{(E)-CD]] CHPh}Cl(CO)(PPri 3)2].NMR: 1H (C6D6, 20 8C), d 8.78 (t, JH]H = 18.3, JP]H = 18.3, OsCH]] CHPh), 7.46 (d, JH]H = 7.3, o-H of Ph), 7.23 (t, JH]H = 7.3, 2 H, m-H of Ph), 7.03 (br d, JH]H = 18.3, OsCH]] CHPh), 6.96 (t, JH]H = 7.3, 1 H, p-H of Ph), 3.39 (d, JP]H = 10.1, 9 H, POMe), 2.47 (m, 6 H, PCHCH3), 1.27 (dvt, N = 14.0, JH]H = 7.1, 18 H, PCHCH3), 1.20 (dvt, N = 11.9, JH]H = 7.1, 18 H, PCHCH3) and 28.94 (dt, JP]H = 134.4, J 24.5, OsH); 2H (C6H6, 20 8C), d 8.81 (s, OsCD]] CHPh), 7.46 (s, o-D of Ph) and 28.88 (d, JP]D = 20.2, OsD); 31P-{1H} (C6D6, 20 8C), d 103.0 (dt, JP]D = 20.2, JP]P = 18.6, POMe) and 17.5 (d, JP]P = 18.6 Hz, PPri 3).[Os{(E)-CH]] CHPh}(Á2-O2CH)(CO)(PPri 3)2] 8. A solution of complex 1 (100 mg, 0.15 mmol) in hexane (5 cm3) was treated with LiBun (0.01 cm3, 1.6 mol dm23 solution in hexane) and stirred during ca. 5 min at room temperature.The resulting pale yellow suspension was filtered through Kieselguhr and a slow stream of carbon dioxide was bubbled through it for ca. 30 min. The solution was cooled at 278 8C, resulting in crystallization of a yellow solid. This was decanted and dried in vacuo. Yield 77.3 mg (75%) (Found: C, 48.89; H, 7.2. Calc. for C28H50O3OsP2: C, 48.95; H, 7.35%). IR (Nujol, cm21): n(CO) 1900s, nasym(OCO) 1560s, n(C]] C) 1540m, nsym(OCO) 1300s. NMR (C6D6, 20 8C): 1H, d 9.09 (d, JH]H = 15.6, 1 H, OsCH- ]] CHPh), 8.63 (t, JP]H = 1.9, 1 H, O2CH), 7.38 (d, JH]H = 7.4 Hz, 2 H, o-H of Ph), 7.24 (t, JH]H = 7.4, 2 H, m-H of Ph), 6.93 (t, JH]H = 7.4, 1 H, p-H of Ph), 6.46 (dt, JH]H = 15.6, JP]H < 1, 1 H, OsCH]] CHPh), 2.44 (m, 6 H, PCHCH3), 1.24 (dvt, N = 13.5, JH]H = 7.1, 18 H, PCHCH3) and 1.17 (dvt, N = 13.2, JH]H = 7.1, 18 H, PCHCH3). 13C-{1H}, d 185.9 (t, JP]C = 9.2, CO), 174.4 (t, JP]C = 1.4, O2CH), 142.6 (t, JP]C = 1.2, ipso-C of Ph), 137.0 (t, JP]C = 9.7, OsCH]] CHPh), 132.8 (t, JP]C = 2.7, OsCH]] CHPh), 128.8 (s, o-CH of Ph), 124.1 (s, m-CH of Ph), 123.7 (s, p-CH of Ph), 24.8 (vt, N = 24.0 Hz, PCHCH3), 19.7 (s, PCHCH3) and 19.6 (s, PCHCH3); 31P-{1H}, d 15.6 (s).[Os{(E)-CH]] CHPh}{Á1-OC(O)H}(CO)2(PPri 3)2] 9. A slow stream of carbon monoxide was bubbled through a hexane solution of complex 8 (100 mg, 0.15 mmol) during 5 min. The white solid obtained was decanted, washed with hexane and dried in vacuo. Yield 89.0 mg (83%) (Found: C, 48.75; H, 6.95.Calc. for C29H50O4OsP2: C, 48.75; H, 7.0%). IR (Nujol, cm21): n(CO) 2020s, 1940s, nasym(OCO) 1625s, n(C]] C) 1590m, nsym- (OCO) 1295s. NMR (C6D6, 20 8C): d 1H, 8.68 (dt, JH]H = 17.0, JP]H < 1, 1 H, OsCH]] CHPh), 8.11 [s, 1 H, OC(O)H)], 7.44 (d, JH]H = 7.7, 2 H, o-H of Ph), 7.44 (t, JH]H = 7.7, 2 H, m-H of Ph) (the OsCH]] CHPh signal is masked by the C6D6 signal), 6.69 (t, JH]H = 7.7, 1 H, p-H of Ph), 2.38 (m, 6 H, PCHCH3), 1.08 (dvt, N = 12.9, JH]H = 6.7, 18 H, PCHCH3) and 1.04 (dvt, N = 12.1, JH]H = 6.9, 18 H, PCHCH3); 13C-{1H}, d 186.8 (t, JP]C = 6.9, CO), 184.4 (t, JP]C = 7.8, CO), 168.4 [s, OC(O)H], 149.1 (t, JP]C = 12.9, ipso-C of Ph), 143.2 (t, JP]C = 2.3, OsCH]] CHPh), 140.0 (t, JP]C = 4.6, OsCH]] CHPh), 128.9 (s, CHo of Ph), 125.4 (s, CHm of Ph), 124.8 (s, p-CH of Ph), 25.3 (vt, N = 25.3 Hz, PCHCH3), 19.6 (s, PCHCH3) and 19.4 (s, PCHCH3); 31P-{1H}, d 9.3 (s).[OsH(Á2-O2CH)(CO)(PPri 3)2] 10. A slow stream of carbon dioxide was bubbled through a solution of [OsH2(h2-CH2]] CHEt)(CO)(PPri 3)2] 11 (93 mg, 0.16 mmol) in hexane (5 cm3) at room temperature. After ca. 20 min a yellow solid was formed. The solid was decanted, washed with hexane and driedJ. Chem. Soc., Dalton Trans., 1997, Pages 181–192 191 in vacuo. Yield 74.8 mg (82%) (Found: C, 41.6; H, 8.1. Calc. for C20H44O3OsP2: C, 41.1; H, 7.6%). IR (Nujol, cm21): n(Os]H) 2180m, n(CO) 1900s, nasym(OCO) 1565s, nsym(OCO) 1385m. NMR (CDCl3, 20 8C): 1H, d 8.81 (s, O2CH), 2.42 (m, 6 H, PCHCH3), 1.30 (dvt, N = 13.6, JH]H = 7.4, 18 H, PCHCH3), 1.26 (dvt, N = 13.0, JH]H = 7.2, 18 H, PCHCH3) and 221.58 (t, JP]H = 15.7, 1 H, OsH). 13C-{1H}, d 182.9 (t, JP]C = 9.1, CO), 173.3 (t, JP]C = 1.5, O2CH), 25.6 (vt, N = 24.8 Hz, PCHCH3), 20.1 (s, PCHCH3) and 19.4 (s, PCHCH3); 31P-{1H}, d 39.6 (s). Reaction of complex 8 with H2. A solution of complex 8 (25 mg, 0.04 mmol) in C6D6 placed in a NMR tube was saturated with H2 at room temperature and the tube sealed.The reaction was monitored by 1H and 31P-{1H} NMR spectroscopy. After 72 h the spectra showed signals corresponding to 10 and styrene. [OsH{Á1-OC(O)H}(CO)2(PPr3)2] 12. A slow stream of carbon monoxide was bubbled through a suspension of complex 10 (90 mg, 0.156 mmol) in dichroromethane (5 cm3) during 5 min. The solution was dried under vacuum, and the residue treated with hexane causing the precipitation of a white solid. The solid was washed with hexane and dried in vacuo.Yield 77.4 mg (82%) (Found: C, 41.15; H, 7.25. Calc. for C21H44O4OsP2: C, 40.6; H, 7.85%). IR (Nujol, cm21): n(Os]H) 2050m, n(CO) 1975s, 1915s, nasym(OCO) 1643s, nsym(OCO) 1370m. NMR (C6D6, 20 8C): 1H, d 7.88 [s, 1 H, OC(O)H], 2.10 (m, 6 H, PCHCH3), 1.14 (dvt, N = 14.1, JH]H = 7.5, 18 H, PCHCH3), 1.17 (dvt, N = 14.1, JH]H = 7.5, 18 H, PCHCH3) and 24.29 (t, JP]H = 21.0 Hz, 1 H, OsH); 31P-{1H}, d 29.1 (s). [OsH{Á1-OC(O)H}(CO){P(OMe)3}(PPri 3)2] 13. A suspension of complex 10 (65 mg, 0.11 mmol) in hexane (7 cm3) was treated with P(OMe)3 (19 ml, 0.16 mmol).After ca. 15 min at room temperature a white solid was formed. The solid was decanted, washed with hexane and dried in vacuo. Yield 60.7 mg (80%) (Found: C, 38.95; H, 7.55. Calc. for C23H53O6OsP3: C, 39.55; H, 8.45%). IR (Nujol, cm21): n(Os]H) 2030w, n(CO) 1920s, nasym(OCO) 1650s, nsym(OCO) 1380m. NMR (C6D6, 20 8C): d 1H, 8.37 [s, 1 H, OC(O)H], 3.43 (d, JP]H = 10.1, 9 H, POMe), 2.29 (m, 6 H, PCHCH3), 1.30 (dvt, N = 12.3, JH]H = 6.8, 18 H, PCHCH3), 1.10 (dvt, N = 12.3, JH]H = 6.8, 18 H, PCHCH3) and 26.30 (dt, JP]H = 149.0, 23.8, 1 H, OsH); 31P-{1H}, d 102.9 (t, JP]P = 17.9, POMe) and 20.8 (d, JP]P = 17.9 Hz, PPri 3).[OsH{Á1-OC(O)H}(Á2-MeO2CC]] ] CCO2Me)(CO)(PPri 3)2] 14. A suspension of complex 10 (65 mg, 0.11 mmol) in hexane (6 cm3) was treated with MeO2CC]] ] CCO2Me (14 ml, 0.11 mmol). After ca. 5 min at room temperature a white solid was formed.The solid was decanted, washed with hexane and dried in vacuo. Yield 60.7 mg (80%) (Found: C, 42.95; H, 6.95. Calc. for C26H50O7OsP2: C, 42.55; H, 7.2%). IR (Nujol, cm21): n(Os]H) 2040w, n(CO) 1955s, n(C]] ] C) 1880m, n(C]] O) 1710s, nasym(OCO) 1620s, nsym(OCO) 1375m. The 1H and 31P-{1H} NMR spectra of a solution of 14 (32 mg, 0.03 mmol) in C6D6 at room temperature showed signals corresponding to 14, 10 and MeO2- CC]] ] CCO2Me in ca. 1 : 1 : 1 molar ratio. Data for 14 (CDCl3, 20 8C): d 1H, 7.63 [s, 1 H, OC(O)H], 3.74 (s, 6 H, ]] ] CCO2Me), 2.64 (m, 6 H, PCHCH3), 1.27 (dvt, N = 12.7, JH]H = 6.7, 18 H, PCHCH3), 1.15 (dvt, N = 14.9, JH]H = 6.6, 18 H, PCHCH3) and 22.28 (dt, JP]H = 28.3, 1 H, OsH); 13C-{1H}, d 179.8 (t, JP]C = 9.1, CO), 167.4 (s, ]] ] CCO2Me), 166.2 [t, JP]C = 5.3, OC(O)H], 107.3 (t, JP]C = 3.3, ]] ] CCO2Me), 52.4 (s, ]] ] CCO2Me), 25.5 (vt, N = 28.0 Hz, PCHCH3), 20.8 (s, PCHCH3) and 18.8 (s, PCHCH3); 31P-{1H}, d 30.8 (s).[OsH(Á2-O2CNEt2)(CO)(PPri 3)2] 15.A solution of complex 9 (28 mg, 0.05 mmol) in C6D6 placed in a NMR tube was treated with NEt2H (5 ml, 0.05 mmol). The tube was sealed under Ar and heated at 60 8C for 1 h. Under these conditions complex 15 was the only detectable product. IR (CH2Cl2, cm21): n(CO) 1870s, n(OCO) 1525s. NMR (C6D6, 20 8C): 1H, d 3.14, 3.02 (both q, JH]H = 7.2, 2 H, NCH2), 2.37 (m, 6 H, PCHCH3), 1.38 (dvt, N = 13.5, JH]H = 6.9, 18 H, PCHCH3), 1.25 (dvt, N = 13.5, JH]H = 6.9, 18 H, PCHCH3), 0.95, 0.91 (both t, JH]H = 7.0, 3 H, NCH2CH2) and 220.37 (t, JP]H = 16.2, 1 H, Os]H); 13C-{1H}, d 184.5 (t, JP]C = 9.2, CO), 165.4 (s, O2C), 39.3, 39.0 (s, NCH2), 25.7 (vt, N = 24.8 Hz, PCHCH3), 20.4 (s, PCHCH3), 19.5 (s, PCHCH3), 14.2 (s, NCH2CH3); 31P-{1H}, d 38.4 (s).Reaction of complex 8 with NEt2H: preparation of [Os{(E)- CH]] CHPh}(Á2-O2CNEt2)(CO)(PPri 3)2] 16. A solution of complex 8 (25 mg, 0.04 mmol) in C6D6 placed in a NMR tube was treated with NEt2H (4 ml, 0.04 mmol).After 3 h at room temperature the 1H and 31P-{1H} NMR spectra of the solution showed a mixture of 8 (41), 10 (10), 15 (12) and 16 (37%). After 24 h at room temperature a mixture of complexes 15 (60) and 16 (40%) was obtained. NMR data for 16 (C6D6, 20 8C): 1H, d 9.37 (d, JH]H = 15.6, 1 H, OsCH]] CHPh), 7.43 (d, JH]H = 6.8 Hz, 2 H, o-H of Ph), 7.28 (t, JH]H = 6.8 Hz, 2 H, m-H of Ph, 7.09 (t, JH]H = 6.8 Hz, 1 H, p-H of Ph), 6.57 (dt, JH]H = 15.6 Hz, JP]H < 1 Hz, 1 H, OsCH]] CHPh), 3.14, 3.04 (q, JH]H = 7.0, 2 H, NCH2), 2.40 (m, 6 H, PCHCH3), 1.27 (dvt, N = 12.0, JH]H = 6.9, 18 H, PCHCH3), 1.17 (dvt, N = 12.0, JH]H = 6.9, 18 H, PCHCH3), 0.93, 0.91 (t, JH]H = 7.0, 3 H, NCH2CH3); 13C-{1H}, d 184.3 (t, JP]C = 9.1, CO), 165.0 (s, O2C), 143.2 (s, ipso-C of Ph), 138.7 (t, JP]C = 7.7, OsCH]] CHPh), 132.3 (br, OsCH]] CHPh), 128.6 (s, o-CH of Ph), 124.0 (s, m-CH of Ph), 123.2 (s, p-CH of Ph), 39.1, 38.7 (s, NCH2), 24.5 (vt, N = 23.7 Hz, PCHCH3), 19.8 (s, PCHCH3), 19.7 (s, PCHCH3), 16.7, 16.6 (s, NCH2CH3); 31P- {1H}, 16.1 (s).[Os{(E)-CH]] CHPh}(CO)(MeCN)2(PPri 3)2]BF4 17. A solution of complex 8 (100 mg, 0.15 mmol) was treated with HBF4?OEt2 (16 ml, 0.15 mmol) in diethyl ether. Addition of MeCN (8 ml, 0.15 mmol) caused the precipitatiion of a white solid, which was washed with ether and hexane and dried in vacuo. Yield 97.3 mg (80%) (Found: C, 45.4; H, 7.05; N, 3.15. Calc. for C31H55BF4N2OOsP2: C, 45.95; H, 6.8; N, 3.45%).IR (Nujol, cm21): n(C]] ] N) 2330w, 2300w, n(CO) 1930s, n(C]] C) 1550m, n([BF4]2) 1060 (br). NMR (CDCl3, 20 8C); 1H, d 8.28 (d, JH]H = 17.3, 1 H, OsCH]] CHPh), 7.20 (t, JH]H = 7.7, 2 H, m-H of Ph), 7.07 (d, JH]H = 7.7, 2 H, o-H of Ph), 6.99 (t, JH]H = 7.7, 1 H, p-H of Ph), 6.42 (d, JH]H = 17.3, 1 H, OsCH]] CHPh), 2.68 (s, 3 H, NCCH3), 2.58 (m, 6 H, PCHCH3), 2.57 (s, 3 H, NCCH3), 1.31 (dvt, N = 13.5, JH]H = 7.2, 18 H, PCHCH3) and 1.29 (dvt, N = 13.5, JH]H = 7.2, 18 H, PCHCH3); 13C-{1H}, d 185.0 (t, JP]C = 9.4, CO), 142.5 (br, ipso-C of Ph), 136.2 (t, JP]C = 3.0, OsCH]] CHPh), 132.7 (t, JP]C = 8.9, OsCH]] CHPh), 128.2 (br, o-CH of Ph), 126.0, 125.5 (both s, NCCH3), 124.0 (br, CHPh, m-CH of Ph), 24.4 (vt, N = 24.7 Hz, PCHCH3), 19.4 (s, PCHCH3), 19.0 (s, PCHCH3), 4.4, 3.7 (both s, NCCH3); 31P-{1H}, d 3.1 (s).[Os(Á2-O2CH)(]] CHCH2Ph)(CO)(PPri 3)2]BF4 18. A solution of complex 8 (100 mg, 0.15 mmol) in chloroform was treated with HBF4?OEt2 (16 ml, 0.15 mmol).The solution was dried in vacuo, yielding a green oil. IR (CH2Cl2, cm21): n(CO) 1980s, nasym(O2CH) 1560s, nsym(O2CH) 1355m. NMR (CDCl3, 20 8C): 1H, d 17.63 (t, JH]H = 6.1, 1 H, Os]] CH), 9.19 (s, O2CH), 7.35– 7.22 (m, 5 H, Ph), 3.52 (d, JH]H = 6.1, 2 H, ]] CHCH2Ph), 2.45 (m, 6 H, PCHCH3), 1.34 (dvt, N = 14.2, JH]H = 7.1, 18 H, PCHCH3) and 1.19 (dvt, N = 13.8, JH]H = 7.5, 18 H, PCHCH3); 13C, d 290.8 (br, Os]] C), 179.6 (t, JP]C = 8.3, CO), 168.7 (s, O2CH), 134.2 (s, ipso-C of Ph), 129.1 (s, o-CH of Ph), 127.8 (s, p-CH of Ph), 127.8 (s, m-CH of Ph), 65.3 (s, CH2Ph), 25.8 (vt, N = 25.9 Hz, PCHCH3), 19.3 (s, PCHCH3) and 19.1 (s, PCHCH3); 31P-{1H}, d 38.3 (s).192 J.Chem. Soc., Dalton Trans., 1997, Pages 181–192 [OsH(CO)(MeCN)2(PPri 3)2]BF4 19. A solution of complex 10 (65 mg, 0.11 mmol) in ether was treated with HBF4?OEt2 (11 ml, 0.11 mmol). The resulting suspension was treated with MeCN (6 ml, 0.11 mmol) causing the precipitation of a white solid.The solid was washed with ether and dried in vacuo. Yield 49.1 mg (75%) (Found: C, 39.3; H, 7.45; N, 3.8. Calc. for C23H49BF4- N2OOsP2: C, 39.0; H, 6.95; N, 3.95%). IR (Nujol, cm21): n(C]] ] N) 2330w, 2290w, n(Os]H) 2140w, n(CO) 2140s. NMR (CDCl3, 20 8C): 1H, d 2.53 (s, 3 H, NCCH3), 2.50 (s, 3 H, NCCH3), 2.40 (m, 6 H, PCHCH3), 1.30 (dvt, N = 13.5, JH]H = 7.0, 36 H, PCHCH3) and 214.87 (t, JP]H = 17.0 Hz, 1 H, OsH); 31P-{1H}, d 24.94 (s). Reaction of complex 10 with HBF4.A CDCl3 solution of complex 10 (8 mg, 0.01 mmol) placed in a NMR tube was treated with HBF4 (1.9 ml, 0.01 mmol) and the tube sealed under argon. After 5 min four products were mainly formed (Fig. 1). Significant NMR signals (CDCl3, 20 8C) are: A 1H, d 7.98 (br, 1 H, O2CH) and 26.80 (br, 2 H, h2-H2); 31P, d 25.6 (s); T1/ms [Os(h2-H2), 300 MHz, CDCl3] = 38 (293), 21 (253), 17 (233), 17 (218 K); B, 1H, d 8.14 [br, 1 H, OC(O)H] and 26.94 (br, 2 H, h2-H2); 31P, d 41.8 (s); T1/ms [Os(h2-H2), 300 MHz, CDCl3] = 36 (293), 21 (253 K); C, 1H, d 9.26 [br, 1 H, OC(O)H] and 29.04 (dd, JP]H = 28.6, 15.7 Hz, OsH); T1/ms (OsH, 300 MHz, CDCl3) = 740 (293), 305 (253), 290 (233), 260 (218 K); D, 1H, d 9.16 [br, 1 H, OC(O)H] and 29.70 (br, OsH); 31P, d 35.6 (br).Computation All calculations were performed with an ab initio molecular orbital method with introduction of correlation energy through the Møller–Plesset perturbational approach,24 excluding excitations concerning the lowest-energy electrons (frozen-core approach).Effective core potentials were used to represent the 60 innermost electrons (up to the 4d shell) of the osmium atom,25 as well as the 10-electron core of the phosphorus atoms.26 The basis set used for the osmium atom is that associated with the pseudo-potential,25 with a (541/41/111) contraction, 27 which is triple z for the 5d shell, double z for the 6s and single z for the 6p. For the phosphorus atoms a valence double z basis set 26 with a (21/21) contraction was used, while the standard 6-31G basis set was used for all the other atoms.28 Geometry optimizations were carried out at the second level of the Møller–Plesset theory (MP2). All geometrical parameters were optimized except the dihedral angle of one of the hydrogen atoms of each phosphine, which was fixed to be oriented towards the carbon of the carbonyl ligand, in order to avoid chemically meaningless rotations around the M]P axis.Single-point energy-only calculations were made at a higher computational level with the MP2 optimized geometries. This is the fourth level of the same perturbational theory (MP4), with consideration of single, double, triple and quadruple excitations. Acknowledgements We thank the Dirección General de Investigación Gentificay Técnica (Projects PB 92–0092 and PB 92–0621, Programa de Promoción General del Conocimiento) and EU (Project, Selective Processes and Catalysis Involving Small Molecules) for financial support. E.O. thanks the DGA (Diputación General de Aragón) for a grant. References 1 C. Bohanna, M. A. Esteruelas, F. J. Lahoz, E. Oñate and L. A. Oro, Organometallics, 1995, 14, 4825. 2 M. A. Esteruelas, F. J. Lahoz, E. Oñate, L. A. Oro and E. Sola, J. Am. Chem. Soc., 1996, 118, 89. 3 E. P. Wasserman, C. B. Moore and R. G. Bergman, Science, 1992, 255, 315. 4 J. Espuelas, M. A. Esteruelas, F. J. Lahoz, L. A. Oro and C. Valero, Organometallics, 1993, 12, 663. 5 H. Werner, M. A. Esteruelas and H. Otto, Organometallics, 1986, 5, 2295. 6 M. J. Albéniz, M. L. Buil, M. A. Esteruelas, A. M. López, L. A. Oro and B. Zeier, Organometallics, 1994, 13, 3746. 7 K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, 3rd edn., Wiley, New York, 1978, p. 323. 8 I. S. Kolomnikov, A. I. Gusev, G. G. Alexandrov, T. S. Lobeeva, Yu. T. Struchkov and M. E. Vol’pin, J. Organomet. Chem., 1973, 59, 349. 9 T. Ito and T. Matsubara. J. Chem. Soc., Dalton Trans., 1988, 2241. 10 G. Jia and D. W. Meek, Inorg. Chem., 1991, 30, 1953. 11 D. R. Roberts, G. L. Geoffroy and M. G. Bradley, J. Organomet. Chem., 1980, 198, C75; M. G. Bradley, D. A. Roberts and G. L. Geoffroy, J. Am. Chem. Soc., 1981, 103, 379. 12 S. A. Smith, D. M. Blake and M. Kubota, Inorg. Chem., 1972, 11, 660; D. J. Darensbourg and A. Rokicki, Organometallics, 1982, 1, 1685; K. K. Pandey, K. H. Garg and S. K. Tiwari, Polyhedron, 1992, 11, 947. 13 H. Werner, M. A. Tena, N. Mahr, K. Peters and H. G. von Schnering, Chem. Ber., 1995, 128, 41. 14 M. A. Esteruelas and H. Werner, J. Organomet. Chem., 1986, 303, 221. 15 M. A. Esteruelas, F. J. Lahoz, E. Oñate, L. A. Oro and L. Rodríguez, Organometallics, 1995, 14, 263. 16 A. Andriollo, M. A. Esteruelas, U. Meyer, L. A. Oro, R. A. Sánchez-Delgado, E. Sola, C. Valero and H. Werner, J. Am. Chem. Soc., 1989, 111, 7431. 17 M. H. Chisholm and M. W. Extine, J. Am. Chem. Soc., 1977, 99, 782; M. H. Chisholm, F. A. Cotton and M. W. Extine, Inorg. Chem., 1978, 17, 2000; F. Calderazzo, S. Ianelli, G. Pampaloni, G. Pelizzi and M. Sperrle, J. Chem. Soc., Dalton Trans., 1991, 693; T. Ishida, T. Hayashi, Y. Mizobe and M. Hidai, Inorg. Chem., 1992, 31, 4481. 18 M. A. Esteruelas, M. P. García, A. M. López, L. A. Oro, N. Ruiz, C. Schlünken, C. Valero and H. Werner, Inorg. Chem., 1992, 31, 5580. 19 A. R. Rossi and R. Hoffman, Inorg. Chem., 1975, 14, 365. 20 M. T. Bautista, E. P. Cappellani, S. D. Drowin, R. H. Morris, C. T. Schueitzer, A. Sella and J. Zubkowski, J. Am. Chem. Soc., 1991, 113, 4876. 21 P. Kubacek and R. Hoffmann, J. Am. Chem. Soc., 1981, 103, 4320. 22 I. E.-I. Radridi, O. Eisenstein and Y. Jean, New J. Chem., 1990, 14, 671. 23 (a) P. J. Desrosiers, L. Cai, Z. Lin, R. Richards and J. Halpern, J. Am. Chem. Soc., 1991, 113, 4173; (b) M. A. Esteruelas, Y. Jean, A. Lledós, L. A. Oro, N. Ruiz and F. Volatron, Inorg. Chem., 1994, 33, 3609. 24 C. Møller and M. S. Plesset, Phys. Rev., 1934, 46, 618. 25 P. J. Hay and W. R. Wadt, J. Chem. Phys., 1985, 82, 299. 26 P. J. Hay and W. R. Wadt, J. Chem. Phys., 1985, 82, 284. 27 Z. Lin and M. B. Hall, J. Am. Chem. Soc., 1992, 114, 2928. 28 W. J. Hehre and R. Ditchfield, J. Chem. Phys., 1972, 56, 2257. Received 27th June 1996; Paper 6/04486G

ISSN:1477-9226    

DOI:10.1039/a604486g

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1999, 183–190 183 5,59-Dicyano-2,29-bipyridine silver complexes: discrete units or co-ordination polymers through a chelating and/or bridging metal–ligand interaction He-Ping Wu,a Christoph Janiak,*a Gerd Rheinwald b and Heinrich Lang b a Institut für Anorganische und Analytische Chemie, Universität Freiburg, Albertstr. 21, D-79104 Freiburg, Germany. E-mail: janiak@uni-freiburg.de b Institut für Chemie, Zehrstuhl für Anorganische Chemie, Technische Universität Chemnitz, Strasse der Nationen 62, D-09111 Chemnitz, Germany Received 24th September 1998, Accepted 6th November 1998 The ambidentate ligand 5,59-dicyano-2,29-bipyridine (L) was found to function as a bi-, tri- or tetra-dentate chelate or chelate/bridging ligand in the co-ordination of silver ions.The mode of co-ordination depends on the anion and the crystallization conditions and was elucidated by single crystal X-ray diVractometry. With metal-co-ordinating anions such as NO3 2 and CF3SO3 2 a tridentate co-ordination mode of L is observed which involves the two bipyridine nitrogen donor atoms and one cyano group.The latter bridges to a neighboring silver center so that a one-dimensional co-ordination polymer results. For NO3 2 this co-ordination polymer forms a 21 helix. With less co-ordinating anions such as BF4 2 and PF6 2 monomeric bis-chelate complexes are obtained, where L assumes a bidentate co-ordination mode involving only the bipyridine nitrogen donor atoms.In the case of the PF6 2 anion a variation in the solvent of crystallization also produced a two-dimensional hexagonal co-ordination polymer where L functions as a tetradentate ligand using all four nitrogen donor atoms in chelation and bridging to the silver centers. Introduction Metal complexes of chelating 2,29-bipyridine or bridging 4,49-bipyridine or derivatives thereof are of constant and general interest in metal co-ordination chemistry.1 4,49-Bipyridine has recently gained considerable interest in the synthesis of (rectangular) two-dimensional network structures.2 The generation of such frameworks is a promising path in the search for stable microporous metal–organic networks that exhibit reversible guest exchange and possibly selective catalytic activity.3,4 Ligands containing CN-donors such as 4,49-dicyanobiphenyl, 1,3,5-tris(4-cyanophenylethynyl)benzene (TEB) and others are also excellent bridging ligands to synthesize porous N N N N CN NC NC CN CN N N CN NC co-ordination polymers.5 A highlighted example is the coordination of TEB with AgSO3CF3 in benzene that led to the isolation of the compound [Ag(CF3SO3)(TEB)]?2C6H6,6 which exhibits 15 Å channels and is porous to benzene exchange.We investigate here the co-ordination chemistry of 5,59- dicyano-2,29-bipyridine (L). This ambidentate ligand can be thought of as combining the ligating properties of the chelating 2,29-bipyridine and the bridging 4,49-dicyanobiphenyl ligand.The idea behind the use of such ambidentate ligands is to have cross-connecting blocks (tectons) for co-ordination polymers based on the endo chelation of two ligands with an appropriate metal center (1) or to supply functional donor atoms within the walls of the co-ordination polymer when the ligands are solely exo bridging (2). Our research has been concerned with the utilization of ambidentate endo-chelating/exo-bridging modified 2,29-bipyridine ligands such as 5,59-diamino-2,29-bipyridine 7 or 2,29-dimethyl- 4,49-bipyrimidine 8 and ligands of the tris(pyrazolyl)borate type for the assembly of metal co-ordination polymers.9,10 In this paper we describe the results of synthetic and structural studies of metal complexes with the ligand 5,59-dicyano-2,29- bipyridine (L) and try to elucidate the factors which lead to bridging, chelating or simultaneous bridging/chelating metal co-ordination.As a metal we have chosen silver(I) which together with copper(I) is a preferred ligand linker because of their favored tetrahedral co-ordination mode.5,11–13 In addition, silver can also assume a linear co-ordination 13 and would thus be ideal for testing the formation of cross-linkers as depicted in 1. Results and discussion The synthesis of 5,59-dicyano-2,29-bipyridine as reported in the literature is the reaction of 2,29-bipyridine-5,59-dicarboxamide with POCl3 in CHCl3 under sonication (50 kHz) to give the product in 86% yield.14 Another method is the sublimation of a mixture of 2,29-bipyridine-5,59-dicarboxamide and P4O10184 J.Chem. Soc., Dalton Trans., 1999, 183–190 under vacuum at a temperature of 300 8C.15 However, a twofold dehydration treatment and a two-fold sublimation of the crude (sublimed) product was found necessary to obtain the product in satisfactory purity. This finally gave the dicyanobipyridine in a low yield of only 29%.Furthermore, if more than 0.5 g of the dicarboxamide was used in the dehydration reaction with P4O10 this resulted in a further decrease of the yield of the product. Thus, we report here a modified method which is based on a two-times dehydration treatment of the dicarboxamide, first with a trifluoroacetic anhydride–pyridine system and then with P4O10 [eqn. (1)]. The initial dehydrated crude product N N M N N NC CN C C N N N N M M N N N N N N M M NC NC CN CN NC NC CN CN 1 2 is obtained in high yield.This crude product was then again dehydrated with P4O10 at 0.2 mbar/200 8C to give the final product in 43% yield. This method has the advantage of a higher yield (compared to the literature),15 the possibility of starting with an increased amount of the dicarboxamide, and the use of a lower sublimation temperature. The reaction routes of 5,59-dicyano-2,29-bipyridine (L) with silver metal salts are summarized in Scheme 1. The reaction of silver nitrate or silver trifluoromethane sulfonate with L in a 2 : 1 metal-to-ligand stoichiometry in ethanol or toluene, respectively, led to the formation of compounds which feature a 1 : 1 metal-to-ligand ratio (3 and 4).Both reactions were carried out by heating the mixture of reactants to 95 8C for 24 h and then slowly cooling to room temperature (RT) at a rate of 1 8C h21. Treating L with an excess of silver salts of less co-ordinating tetrafluoroborate or hexafluorophosphate anions (again with 2 : 1 metal-to-ligand stoichiometry) at room temperature gave silver complexes with a 1 : 2 (5 and 6) or a 1 : 1 metal-to-ligand ratio (7).The outcome of these latter reactions could be subtly aVected by a change in solvents. For BF4 2 as the anion an ethanol–tetrahydrofuran mixture gave the same isostructural complex composition 5 as an acetonitrile–ethanol–methylene chloride or toluene mixture as shown by X-ray powder diffractometry. For PF6 2 as anion the inclusion of acetonitrile in the solvent mixture led to a 1 : 1 metal–ligand compound 7 instead of the 1 : 2 complex 6.All compounds were obtained in yields above 50%. Characterization was mainly based on X-ray diVraction studies. The metal–ligand co-ordination modes elucidated from single-crystal structure determinations are depicted in Figs. 1, N H2N(O)C N C(O)NH2 Crude product (F3CCO)2O pyridine dioxane P4O 0.2 mbar 200 °C N NC N CN (1) Scheme 1 N N NC CN AgNO3 ethanol 95 °C to RT L 1[Ag(NO3)(µ-L)] 3 ¥ 1[Ag(CF3SO3)(µ-L)] 4 Ag(CF3SO3) toluene 95 °C to RT AgBF4 [Ag(L)2]BF4 5 ethanol/THF or CH3CN/ethanol/ CH2Cl2(toluene) AgPF6 ethanol/THF or ethanol/CH2Cl2/ toluene [Ag(L)2]PF6 6 CH3CN/ethanol/ toluene AgPF6 2[Ag(µ-L)]PF6 · 1/2 C6H5Me 7 ¥ ¥J.Chem. Soc., Dalton Trans., 1999, 183–190 185 3, 5, and 7 for the 1-D co-ordination polymers 3 and 4, the bis-chelate complexes 5 and 6, and the 2-D framework 7, respectively. The structural studies revealed that the anions Fig. 1 Section of the one-dimensional co-ordination polymer of 1 •[Ag(NO3)(m-L)] 3. NO3 2 and CF3SO3 2 in 3 and 4, respectively, still co-ordinate to a metal center with one of the oxygen atoms (Figs. 1 to 4). They serve as terminal ligands and occupy one position in the distorted tetrahedral co-ordination sphere of the silver ions. At the same time, the dicyanobipyridine ligand chelates a silver atom in 3 and 4 through the bipyridine moiety and bridges to a neighboring silver center through one of the exodentate cyano groups.Hence, the silver co-ordination sphere consists of an oxygen atom, two bipyridine nitrogen atoms and a cyano nitrogen atom. The planes of the two pyridine rings within a bipyridine ligand deviate by 9.1(1) (3) and 16.9(3)8 (4) from coplanarity. The potentially tetradentate dicyanobipyridine group functions as a tridentate ligand only; the other cyano group is not involved in metal co-ordination even though a twofold excess of metal over ligand has been oVered during the reaction.The bridging action of the ligand L gives rise to one-dimensional co-ordination polymers, • 1 [Ag(NO3)(m-L)] 3 and • 1 [Ag(CF3SO3)(m-L)] 4, whose metal–ligand arrangement is depicted in Figs. 1 and 3, respectively. While the chain in 4 is oriented rather straight with the metal and bipyridine ligands lying all in one plane, it is noteworthy that the strand for the silver nitrate complex 3 assumes a 21-helical conformation.These chain conformations together with the packing of neighboring strands are further illustrated in Figs. 2 and 4 with the help of stereoplots. The chains run parallel in the Fig. 2 (a) Stereoplot of the chain structure of 1 •[Ag(NO3)(m-L)] 3 illustrating the helical nature and the intertwining of neighboring 21 helices (view along a) and (b) schematic representation of the interdigitation of adjacent strands in 3.186 J. Chem. Soc., Dalton Trans., 1999, 183–190 case of 4.For 3 neighboring strands are of opposite helicity and interlock or interdigitate as is schematically depicted in Fig. 2(b). Bipyridine ligands from adjacent strands mutually intrude into the openings within the chain. The interdigitated bipyridine moieties form p–p stacks with an interplane distance of 3.47 Å. In the orientation of neighboring chains a weakly bridging mode of the NO3 2 and CF3SO3 2 anions may play a role. Interchain non-bonding Ag ? ? ? O contacts are 3.001 Å (to O1) in 3 and 3.370 and 3.590 Å (to O2 and O3, respectively) in 4.In addition, an interchain silver–pyridine or electrostatic Fig. 3 Metal–ligand arrangement in a segment of the one-dimensional co-ordination polymer of 1 •[Ag(CF3SO3)(m-L)] 4. cation p contact might play a small role in 3, as the Ag ? ? ?C distances are 3.497 (to C3), 3.596 (to C4), and 3.716 Å (to C5). Silver is known to have a remarkably high aYnity for some aromatic p-donor systems.16 When silver salts of only weakly co-ordinating anions such as BF4 2 and PF6 2 are employed, as in the isostructural compounds 5 and 6, respectively,8,17 the metal co-ordination Fig. 5 Molecular structures of the bis-chelate complex [AgL2]BF4 5 (shown) and of the isostructural [AgL2]PF6 6. Fig. 4 Stereoplot of the chain structure of 1 •[Ag(CF3SO3)(m-L)] 4 to show the parallel alignment of the chains in contrast to those of 3. View along a. Fig. 6 Stereoscopic partial cell plot of complex 5 to illustrate the packing of the bis-chelate complexes. The BF4 2 anion has been omitted for clarity.View approximately along b.J. Chem. Soc., Dalton Trans., 1999, 183–190 187 sphere is fully constructed from the ligand donor atoms (Figs. 5 and 6). However, only the endodentate bipyridine nitrogen atoms serve as donor atoms towards silver; the exodentate cyano groups are not involved in metal co-ordination even though a twofold molar excess of metal over ligand has again been oVered during the reaction.The results are cationic bischelate complexes of the type [AgL2]1 with BF4 2 (5) and PF6 2 (6) as the anion. The non-involvement of the cyano groups is remarkable in view of their known high aYnity towards Ag1 ions.18 The cyano nitrogen atom is perhaps a somewhat weaker donor atom when compared with a pyridine nitrogen atom. The co-ordination of the latter is definitely enhanced further through the chelate eVect of the bipyridine unit.Two chelating ligands construct a strongly distorted environment, almost halfway between tetrahedral and square planar as is evident from the graphical presentation in Figs. 5 and 6. The interplane angle between the two five-membered chelate rings formed by Ag–N1–C5–C6–N2 and their symmetry equivalent atoms is 55.34(5)8 for 5 and 56.31(5)8 for 6. The origin of this distortion is not clearly apparent as the nearest non-co-ordinating atoms are fluorine atoms, which are, however, 3.12 (5) and 3.16 Å (6) away.The two pyridine rings of the bipyridine ligand remain essentially coplanar to within 38 for 5 or 58 for 6 (based on the torsion angles N1–C5–C6–N2 and C4–C5–C6–C7). A stereoscopic cell plot of 5 in Fig. 6 serves to illustrate the packing of Fig. 7 Section of the two-dimensional framework of 2 •[Ag(m-L)]PF6? 1– 2C6H5Me 7. View along c. The toluene molecule and two of the three crystallographically diVerent PF6 2 anions are not shown for clarity (see Fig. 8 for these remaining moieties and Fig. 9 for the complete ensemble). Owing to space requirements the ligand is not fully labelled. Symmetry equivalent positions: 22 = 2y 1 1, x 2 y 2 1, z; 23 = 2x 1 y 1 1, 2x 1 1, z; 27 = 2x 1 1, 2y 1 1, 2z. Fig. 8 The toluene–PF6 layer in the crystal structure of 2 •[Ag(m-L)]- PF6?1– 2C6H5Me 7 which contains two of the three crystallographically diVerent PF6 2 sites. One of these anions P3 sits on a special position and is disordered. View along c as in Fig. 7. the ionic bis-chelate complexes through a bipyridine p–p interaction of neighboring molecules with an interplane distance of 3.76 Å. The working hypothesis that the co-ordination of the exodentate cyano nitrogen atoms would be exercized only when the simultaneous endodentate co-ordination of two chelating bipyridine moieties was not possible, was proven wrong with the structure elucidation of complex 7. In this two-dimensional co-ordination polymer of formula 2 •[Ag(m-L)]PF6?��� C6H5Me the dicyanobipyridine ligand chelates a silver ion and bridges to two other metal centers with both of the exodentate cyano groups (Fig. 7). Two types of C3-symmetrical triangular openings are thus created in this framework. In the larger ones one of the three crystallographically diVerent PF6 anions is partly immersed. The other two PF6 anion sites lie within a layer together with the toluene solvent molecules (Fig. 8). The metal– ligand layer (A, together with one PF6) and the toluene–PF6 layer (B) are stacked along the c direction in a .. . BAABAA. . . sequence as is illustrated in Fig. 9. Clearly, a silver–toluene or electrostatic cation p contact is present in 7, as rather short Ag ? ? ? C distances of 2.815 (to C18) and 2.830 Å (to C17) are encountered.16 The remaining silver–toluene contacts are 3.381 (to C16), 3.771 (to C15), 3.769 (to C14), and 3.335 Å (to C13). The two pyridine rings are strongly twisted by 21.0(1)8 in 7, more than in the other compounds 3–6.The metal environment is again almost halfway between tetrahedral and square planar. The interplane angle between the five-membered chelate ring and the plane formed by the cyano nitrogen atoms with the silver center is 25.5(2)8. Selected bond distances and angles for compounds 3–6 are summarized in Table 1. Conclusion In the ambidentate ligand 5,59-dicyano-2,29-bipyridine (L) both the bipyridine nitrogen and the exodentate cyano nitrogen atoms can function as donors towards a silver metal center.The choice of metal co-ordination was found to depend on the counter anion 8,19 or the solvent of crystallization. When a coordinating anion was present in the silver co-ordination sphere L acted as a tridentate ligand, chelating through the bipyridine moiety and bridging through one of the cyano groups. With non-co-ordinating anions the silver co-ordination sphere was solely constructed from the ligand nitrogen donors.Either the formation of bis-chelate silver complexes through bisbipyridine nitrogen co-ordination be observed with L as a bidentate ligand, or, with a slight change in the solvent mixture for crystallization, L could also become tetradentate Fig. 9 Partial cell plot of 2 •[Ag(m-L)]PF6?1– 2C6H5Me 7 viewed along the ab plane to show the . . . BAABAA. . . sequence of the metal–ligand (A) and toluene–PF6 (B) layers which were separately depicted in Figs. 7 and 8.188 J. Chem. Soc., Dalton Trans., 1999, 183–190 Table 1 Selected bond distances (Å) and angles (8) for complexes 3–7 Compound Ag1–N1bipy Ag1–N2bipy Ag1–N3CN Ag1–N4CN Ag1–O1 N3–C11 N4–C12 1 •[Ag(NO3)(m-L)] 3 2.339(2) 2.453(2) a: 2.425(3) 2.371(2) 1.143(4) 1.148(4) 1 •[Ag(CF3SO3)(m-5)] 4 2.349(6) 2.322(4) c: 2.156(5) 2.689(5) 1.139(7) 1.116(8) [AgL2]BF4 5 2.356(2) 2.312(2) 1.139(4) 1.137(4) [AgL2]PF6 6 2.325(2) 2.378(3) 1.140(5) 1.144(5) 2 •[Ag(m-L)]PF6?1– 2C6H5Me 7 2.377(6) 2.444(6) g: 2.375(7) h: 2.294(7) 1.134(10) 1.146(10) Within the anions N1–Ag1–N2 N1–Ag1–O1 N2–Ag1–O1 N1–Ag1–N4 N2–Ag1–N4 O1–Ag1–N4 C12–N4–Ag1 X–O1–Ag1 O1–N5 1.277(3) O2–N5 1.236(3) O3–N5 1.240(3) 68.42(7) 148.69(8) 129.38(8) a: 106.44(8) a: 90.32(8) a: 99.54(9) b: 148.4(2)1 X = N5; 103.0(2) O1–S1 1.438(5) O2–S1 1.438(5) O3–S1 1.430(5) 70.6(2) 105.5(2) 118.3(2) c: 129.2(2) c: 144.3(2) c: 87.3(2) d: 168.3(6) X = S1: 110.8(3) N1–Ag1–N2 N1–Ag1–N1 N2–Ag1–N2 N1–Ag1–N2 N1–Ag1–N3 N1–Ag1–N4 N2–Ag1–N3 N2–Ag1–N4 N3f–Ag1–N4g B1–F1 1.389(4) B1–F2 1.374(4) 71.12(8) e: 136.5(1) e: 165.7(1) e: 114.57(8) P1–F1 1.596(2) P1–F2 1.599(3) P1–F3 1.596(2) 70.75(9) f: 170.5(1) f: 135.3(1) f: 113.12(9) P1–F 1.539(7)–1.569(9) P2–F 1.576(10)–1.601(11) P3–F 1.40(4)–1.54(4) 68.38(19) g: 88.4(2) h: 164.6(3) g: 144.9(3) h: 101.7(3) 94.5(3) Symmetry transformations apply to the last atom in the bond or angle definition if not assigned otherwise: a = 2x 1 0.5, y 2 0.5, 2z 1 0.5; b = 2x 1 0.5, y 1 0.5, 2z 1 0.5; c = 2x 1 1, y 1 0.5, 2z 1 1.5; d = 2x 1 1, y 2 0.5, 2z 1 1.5; e = 2x, y, 2z 1 0.5; f = 2x 1 1, y, 2z 1 1.5; g = 2y 1 1, x 2 y 2 1, z = _2 in Fig. 7; h = 2x 1 y 1 1, 2x 1 1, z = _3 in Fig. 7. utilizing all four nitrogen donor atoms in chelating and bridging co-ordination between three metal centers. Pyridine p–p interactions and silver–pyridine or –toluene cation p contacts were controlling factors in the non-bonded crystal organization. Experimental The NMR spectra were collected on a Varian O-300 spectrometer (300.0 MHz for 1H, 75.4 MHz for 13C) and calibrated against the solvent signal (d8-THF: 1H, d 1.73; 13C, d 25.2), IR spectra on a Perkin-Elmer 783 spectrophotometer as KBr disks or as Nujol mulls.Elemental analyses were carried out with a Perkin-Elmer Elemental Analyzer E 240 C. X-Ray powder diVractograms were obtained with a Siemens powder diVractometer D5000 using Cu-Ka radiation. All crystallizations of the silver complexes were carried out in the dark.Preparations 2,29-Bipyridine-5,59-dicarboxamide. A mixture of 3.0 g of diethyl 2,29-bipyridine-5,59-dicarboxylate, 100 ml of ethanol and 100 ml of ethylene glycol was saturated with ammonia and heated in a sealed round bottom flask in an oil-bath at 95 8C for 48 h. The precipitate formed was collected and washed with hot ethanol and ethylene glycol. 1.9 g (79%) of 2,29-bipyridine-5,59-dicarboxamide was obtained, mp >280 8C (lit.15 >310 8C).IR: 3375s, 3170s, 1660s, 1634s, 1599s, 1548m, 1480w, 1410s, 1370m, 1285w, 1252m, 1165w, 1132m, 1118w, 1055w, 1028m, 955w, 860m, 810w, 790m, 760w, 720m, 665m, 659m, 638m, 600w and 535w cm21. 5,59-Dicyano-2,29-bipyridine (L). This compound was prepared by two methods. Literature method.15 2,29-Bipyridine-5,59-dicarboxamide (0.2 g, 0.8 mmol) and 0.5 g (1.7 mmol) of P4O10 were placed into a sublimator and kept at 0.2 mbar/300 8C until the sublimation had ceased. The crude product which easily absorbs water from the air was resublimed to obtain 0.1 g of a colorless solid.This was repurified with 0.2 g of P4O10 in a sublimator at 0.2 mbar/ 300 8C followed by resublimation to give 0.05 g of L (29% yield), mp 275.9–276.6 8C (lit. 269–271,15 284–285 8C14). IR: 3420w, 3070w, 2240s, 1985w, 1898w, 1796w, 1720s, 1597s, 1540m, 1468s, 1373s, 1292m, 1240s, 1170w, 1130w, 1053w, 1030s, 948w, 850s, 795w, 776w, 751m, 726m, 652m and 554m cm21. Modified method.Trifluoroacetic anhydride (2.5 ml, 18.4 mmol) was added dropwise to a stirred ice-cooled suspension of 2,29-bipyridine-5,59-dicarboxamide (2.0 g, 8.4 mmol) in anhydrous 1,4-dioxane (150 ml) and anhydrous pyridine (1.5 ml, 18.4 mmol). Over the period of the addition the temperature was kept below 5 8C. The reaction mixture was then allowed to warm to room temperature and stirred for 10 h. Then 100 ml of distilled water were added, the solid product was removed by filtration and washed with water to obtain 1.5 g of crude product.A 0.2 g amount of this was heated together with 0.5 g of P4O10 in a sublimator at 0.2 mbar/180 8C until sublimation had ceased. The solid was purified by resublimation to obtain 0.12 g of a colorless solid (L) (43% yield), mp 275.4–276.2 8C. The IR spectrum was identical to that of the above sample. 1H NMR (d8-THF): d 8.34 (dd, 2 H, H4, H49, J = 8.3, 2.1), 8.57 (dd, 2 H, H3, H39, J = 8.2, 0.8 Hz) and 8.9 (br, 2 H, H6, H69). 13C NMR (d8-THF): d 111.63 (C5, C59), 117.49 (CN), 122.38 (C3, C39), 142.33 (C4, C49), 153.40 (C6, C69) and 157.75 (C2, C29). (Ï-5,59-Dicyano-2,29-bipyridine)nitratosilver(I), 1 •[Ag(NO3)- (Ï-L)] 3. In a 50 ml round bottom flask an ethanolic solution (10 ml) of L (21 mg, 0.10 mmol) was added to an ethanolic solution (15 ml) of silver nitrate (34 mg, 0.20 mmol). A yellow precipitate immediately formed. The flask was sealed and heated to 95 8C for 24 h. The reaction mixture was then cooled to room temperature at a rate of 1 8C h21.Well formed yellow rod-like crystals were produced, collected by filtration, washed with water and ethanol and dried under vacuum. Yield: 28 mg (76%, based on L) (Found: C, 38.07; H, 1.56; N, 17.92. Calc. for C12H6AgN5O3: C, 38.30; H, 1.60; N, 18.60%). IR: 3440m, 3110w, 3062w, 3030w, 2240m, 1725w, 1598s, 1540w, 1478s, 1468m, 1387s, 1316m, 1240m, 1249w, 1030m, 849m, 735m, 651s and 555w cm21. (Ï-5,59-Dicyano-2,29-bipyridine)(trifluoromethanesulfonato)- silver(I), 1 •[Ag(CF3SO3)(Ï-L)] 4.In a 50 ml round bottom flask a solution of Ag(CF3SO3) (56 mg, 0.22 mmol) in 5 ml of toluene was added to 15 ml of a toluene solution of L (21 mg,J. Chem. Soc., Dalton Trans., 1999, 183–190 189 0.1 mmol). A white precipitate immediately formed. The flask was sealed and heated to 95 8C for 24 h, followed by cooling to room temperature at 1 8C h21. The well formed colorless to pale green crystals were collected by filtration, washed with ethanol and dried under vacuum.Yield 31 mg (67%) (Found: C, 33.37; H, 1.26; N, 11.86. Calc. for C13H6AgF3N4O3S: C, 33.69; H, 1.29; N, 12.10%). IR: 3440m, 3120w, 3070w, 3138w, 2270w, 2240m, 1598s, 1540m, 1480m, 1468s, 1374m, 1260s, 1240m, 1188w, 1160s, 1035s, 1030s, 945w, 850s, 705m, 650m, 634m, 580w, 555m and 520m cm21. Bis(5,59-dicyano-2,29-bipyridine)silver(I) tetrafluoroborate, [AgL2]BF4 5. A solution of AgBF4 (21 mg, 0.10 mmol) in 10 ml of ethanol was carefully overlayered in a test-tube with a solution of L (10 mg, 0.05 mmol) in 10 ml of tetrahydrofuran.After 10 d at room temperature, well formed orange crystals had appeared at the boundary between ethanol and THF. They were collected, washed with water and ethanol and dried under vacuum. Yield 8 mg (66% based on L) (Found: C, 47.40; H, 1.97; N, 18.38. Calc. for C24H12AgBF4N8: C, 47.54; H, 1.98; N, 18.48%). IR: 3440m, 3124w, 3064w, 3235w, 2239m, 1725w, 1598s, 1560w, 1540w, 1478s, 1467m, 1388s, 1376m, 1320m, 1241m, 1126m, 1088m, 1070s, 1050s, 1030s, 1000m, 946w, 938w, 869m, 850w, 735m, 670w, 650w, 560w and 522w cm21.When a solution of AgBF4 (10 mg, 0.05 mmol) in 0.5 ml of acetonitrile and 4 ml of ethanol was carefully overlayered in a test-tube with a solution of L (21 mg, 0.10 mmol) in 10 ml of dichloromethane (or toluene) orange crystals were obtained after 5 d. Yield 15 (18) mg [49% (58%)]. The crystals were identified as complex 5 based on an identical IR spectrum.Furthermore, they were shown to be isotypic from their X-ray powder diVractograms which in addition matched the calculated pattern from the single crystal data. Bis(5,59-dicyano-2,29-bipyridine)silver(I) hexafluorophosphate, [AgL2]PF6 6. A solution of AgPF6 (28 mg, 0.11 mmol) in 10 ml of ethanol was carefully overlayered in a test-tube with a solution of L (10 mg, 0.05 mmol) in 10 ml of tetrahydrofuran. After 12 d at room temperature, the well formed orange crystals were collected, washed with water and ethanol and dried under vacuum.Yield 19 mg (57% based on L) (Found: C, 42.81; H, 1.59; N, 16.51. Calc. for C24H12AgF6N8P: C, 43.31; H, 1.80; N, 16.85%). IR: 3435m, 3139w, 3064w, 3036w, 2238m, 1728w, 1600s, 1560w, 1540w, 1480s, 1466m, 1388s, 1380m, 1323m, 1250m, 1150w, 1033m, 947w, 860m, 850w, 830m, 788w, 733w, 670w, 650w and 562w cm21. Slow concentration of a mixture of solutions of AgPF6 in ethanol and of L in THF (or dichloromethane and toluene) in the mole ratio of 1 : 1 (or 2 : 1) also gave complex 6, with the yield being about 57%. The identity was based on IR spectroscopy and X-ray powder diVractometry. (Ï3-5,59-Dicyano-2,29-bipyridine)silver(I) hexafluorophosphatehemitoluene solvate, 2 •[Ag(Ï3-L)]PF6?1–2 C6H5Me 7.A solution of 27 mg (0.11 mmol) of AgPF6 in a mixture of 1 ml of acetonitrile and 2 ml of ethanol was overlayered in a test-tube with a solution of 10 mg (0.05 mmol) of L in 6 ml of toluene.After 8 d at room temperature (in the dark) pale yellow crystals had formed. Yield 16 mg (64% based on L) (Found: C, 36.66; H, 1.93; N, 11.40. Calc. for C15.5H10AgF6N4P: C, 36.8; H, 1.98; N, 11.90%). IR: 3440m, 3108w, 3070w, 2240m, 1730w, 1598s, 1550w, 1540s, 1478s, 1467s, 1374m, 1280w, 1240s, 1088s, 1054w, 1030s, 950m, 850s (br), 776m, 734m, 695m, 650m, 565s and 555m cm21. Even when stored in the dark, compound 7 slowly turned dark and appeared to be more sensitive to decomposition than the other four complexes 3–6.Structure determinations Data were collected on a Bruker Smart CCD diVractometer with Mo-Ka radiation (l = 0.71073 Å) and the use of a graphite monochromator. The crystal specimens were cooled to 173(2) K. Structure solution was performed by direct methods (SHELXL 97).20 Refinement: full-matrix least squares on F 2 (SHELXL 97); all non-hydrogen positions found and refined with anisotropic thermal parameters. The hydrogen atoms of complexes 3, 5 and 6 were found and refined, including the thermal parameter.Calculated hydrogen positions were added in the structures of 4 and 7, refined as riding atoms on the bonded carbon atom position. With respect to data quality it should be noted that the crystal of 4 was very small. The refinement of the heavily disordered fluorine atoms in the third hexafluorophosphate anion of 7 (P3, cf. Fig. 8) is a rough approximation, the electron density related to the fluorine Table 2 Crystal data for compounds 3–7 Formula M Crystal system Space group Crystal size/mm 2q range/8 h; k; l range a/Å b/Å c/Å b/8 V/Å3 Z Dc/g cm23 F(000) m/cm21 Measured reflections Unique reflections (Rint) Observed reflections [I > 2s(I )] Parameters refined Dr/e Å23 a R1; wR2 [I > 2s(I )] (all reflections) 3 C12H6AgN5O3 376.09 Monoclinic P21/n 0.4 × 0.2 × 0.1 4–62.1 210, 11; 210, 7; 229, 24 8.2230(2) 7.5328(2) 20.3896(5) 93.308(1) 1260.87(5) 4 1.981 736 16.17 9319 3703 (0.0586) 3269 214 0.537; 21.361 0.0337; 0.0796 0.0403; 0.0839 4 C13H6AgF3N4O3S 463.15 Monoclinic P21/c 0.15 × 0.1 × 0.02 4.3–57.8 211, 12; 25, 21; 29, 12 9.4946(5) 15.8010(8) 10.3381(5) 92.242(2) 1549.78(14) 4 1.985 904 14.91 5664 2813 (0.0836) 1634 226 0.616; 20.960 0.0522; 0.0874 0.1188; 0.1094 5 C24H12AgBF4N8 607.10 Monoclinic C2/c 0.3 × 0.15 × 0.1 4.0–62.3 217, 31; 210, 9; 221, 22 21.9430(3) 7.5298(1) 15.7431(2) 112.676(1) 2400.10(5) 4 1.680 1200 9.02 7335 3420 (0.0416) 2561 197 0.562; 20.808 0.0440; 0.0925 0.0693; 0.1035 6 C24H12AgF6N8P 665.26 Monoclinic C2/c 0.3 × 0.2 × 0.05 4.1–57.5 228, 25; 24, 10; 210, 10 21.8760(1) 8.2210(2) 15.8848(3) 115.277(1) 2583.24(8) 4 1.711 1312 9.17 4895 2649 (0.0298) 2286 206 0.369; 20.593 0.0384; 0.0852 0.0486; 0.0907 7 C15.5H10AgF6N4P 505.11 Hexagonal P63/m 0.4 × 0.3 × 0.3 2.6–60.4 224, 17; 28, 24; 227, 9 17.8017(3) 17.8017(1) 19.6142(1) 90 5383.0(1) 12 1.870 2964 12.80 22491 5094 (0.0538) 3491 277 1.694; 22.171 0.0753; 0.1882 0.1104; 0.2037 a Largest diVerence peak and hole.190 J.Chem. Soc., Dalton Trans., 1999, 183–190 atoms forming an almost perfect shell around P3. Crystal data are listed in Table 2. Graphics were prepared with ORTEP 3 and PLATON/PLUTON 97 for Windows.21 CCDC reference numbers 186/1235. See http://www.rsc.org/suppdata/dt/1999/183/ for crystallographic files in .cif format. Acknowledgements This work was supported by the Alexander von Humboldt Foundation (fellowship for H.-P.W.), the Fonds der Chemischen Industrie, and the Deutsche Forschungsgemeinschaft. References 1 A. E. Martell and R. D. Hancock, Metal Complexes in Aqueous Solutions, Plenum Press, New York, 1996; A. v. Zelewsky, Stereochemistry of Coordination Compounds, Wiley, Chichester, 1996; J. M. Lehn, Supramolecular Chemistry, VCH, Weinheim, 1995; E. C. Constable, Prog. Inorg. Chem., 1994, 42, 67. 2 See for example: M.-L. Tong, B.-H. Ye, J.-W.Cai, X.-M. Chen and S. W. Ng, Inorg. Chem., 1998, 37, 2645; L. R. MacGillivray, R. H. Groeneman and J. L. Atwood, J. Am. Chem. Soc., 1998, 120, 2676; A. J. Blake, S. J. Hill, P. Hubberstey and W.-S. Li, J. Chem. Soc., Dalton Trans., 1998, 909; M.-L. Tong, X.-M. Chen, X.-L. Yu and T. C. W. Mak, J. Chem. Soc., Dalton Trans., 1998, 5; K. N. Power, T. L. Hennigar and M. J. Zaworotko, New. J. Chem., 1998, 177; P. Stang and B. Olenyuk, Acc. Chem. Res., 1997, 30, 502; O. M.Yaghi, H. Li and T. L. Groy, Inorg. Chem., 1997, 36, 4292; J. Lu, T. Paliwala, S. C. Lim, C. Yu, T. Niu and A. J. Jacobson, Inorg. Chem., 1997, 36, 923; L. Carlucci, G. Ciani, D. M. Proserpio and A. Sironi, J. Chem. Soc., Dalton Trans., 1997, 1801; P. Lossier and M. J. Zaworotko, Angew. Chem., Int. Ed. Engl., 1996, 35, 2779; O. M. Yaghi and H. Li, J. Am. Chem. Soc., 1996, 118, 295; C. A. Hunter, Angew. Chem., Int. Ed. Engl., 1995, 34, 1079. 3 C. Janiak, Angew. Chem., Int. Ed.Engl., 1997, 36, 1431; O. M. Yaghi, H. Li, C. Davis, D. Richardson and T. L. Groy, Acc. Chem. Res., 1998, 31, 474. 4 P. Brunet, M. Simard and J. D. Wuest, J. Am. Chem. Soc., 1997, 119, 2737. 5 K. A. Hirsch, S. R. Wilson and J. S. Moore, Chem. Eur. J., 1997, 3, 765; Inorg. Chem., 1997, 36, 2960; D. Venkataraman, S. Lee, J. S. Moore, P. Zhang, K. A. Hirsch, G. B. Gardner, A. C. Covey and C. L. Prentice, Chem. Mater., 1996, 8, 2030. 6 G. B. Gardner, D. Venkataraman, J. S. Moore and S.Lee, Nature (London), 1995, 374, 792. 7 C. Janiak, H.-P. Wu, S. Deblon, M. J. Kolm, P. Klüfers and H. Piotrowski, Eur. J. Inorg. Chem., submitted for publication. 8 C. Janiak, L. Uehlin, H.-P. Wu, P. Klüfers, H. Piotrowski and T. G. Scharmann, Inorg. Chem., submitted for publication. 9 See for example: C. Janiak, T. G. Scharmann, J. C. Green, R. P. G. Parkin, M. J. Kolm, E. Riedel, W. Mickler, J. Elguero, R. M. Claramunt and D. Sanz, Chem. Eur. J., 1996, 2, 992; C. Janiak, T.G. Scharmann, W. Günther, F. Girgsdies, H. Hemling, W. Hinrichs and D. Lentz, Chem. Eur. J., 1995, 1, 637. 10 See for example: F.-Q. Liu and T. D. Tilley, Chem. Commun., 1998, 103; H. Li, C. E. Davis, T. L. Groy, D. G. Kelley and O. M. Yaghi, J. Am. Chem. Soc., 1998, 120, 2186; C. J. Kepert and M. J. Rosseinsky, Chem. Commun., 1998, 31; B. F. Hoskins, R. Robson and D. A. Slizys, Angew. Chem., Int. Ed. Engl., 1997, 36, 2752; R. W. Saalfrank, O. Struck, M. G. Davidson and R.Snaith, Chem. Ber., 1994, 127, 2489. 11 C. Kaes, M. W. Hosseini, C. E. F. Rickard, B. W. Skelton and A. H. White, Angew. Chem., Int. Ed. Engl., 1998, 37, 920; P. K. Bowyer, K. A. Porter, A. D. Rae, A. C. Willis and S. B. Wild, Chem. Commun., 1998, 1153; K. A. Hirsch, S. R. Wilson and J. S. Moore, Chem. Commun., 1998, 13; L. Carlucci, G. Ciani, D. W. v. Gudenberg, D. M. Proserpio and A. Sironi, Chem. Commun., 1997, 631; A. J. Blake, N. R. Champness, A. Khlobystov, D. A. Lemenovskii, W.-S. Li and M. Schröder, Chem. Commun., 1997, 2027; L. Carlucci, G. Ciani, D. M. Proserpio and A. Sironi, Chem. Commun., 1996, 1393; C. Janiak, T. G. Scharman, P. Albrecht, F. Marlow and R. Macdonald, J. Am. Chem. Soc., 1996, 118, 6307; L. Carlucci, G. Ciani, D. M. Proserpio and A. Sironi, J. Am. Chem. Soc., 1995, 117, 4562. 12 See I. M. Müller, T. Röttgers and W. S. Sheldrick, Chem. Commun., 1998, 823; Y. Suenaga, S. G. Yan, L. P. Wu, I. Ino, T. Kuroda-Sowa, M. Maekawa and M. Munakata, J. Chem. Soc., Dalton Trans., 1998, 1121; O. M. Yaghi and H. Li, J. Am. Chem. Soc., 1995, 117, 10401. 13 J. A. R. Navarro, J. M. Salas, M. A. Romero and R. Faure, J. Chem. Soc., Dalton Trans., 1998, 901; C. B. Aakeröy and A. M. Beatty, Chem. Commun., 1998, 1067. 14 P. N. W. Baxter and J. A. Connor, J. Organomet. Chem., 1988, 355, 193. 15 C. P. Whittle, J. Heterocycl. Chem., 1977, 14, 191. 16 O. Struck, L. A. J. ChrisstoVels, R. J. W. Lugtenberg, W. Verboom, G. J. van Hummel, S. Harkema and D. N. Reinhoudt, J. Org. Chem., 1997, 62, 2487; J. Gross, G. Harder, F. Vögtle, H. Stephan and K. Gloe, Angew. Chem., Int. Ed. Engl., 1995, 34, 481; A. Ikeda, H. Tsuzuki and S. Shinkai, J. Chem. Soc., Perkin Trans. 2, 1994, 2073; H. C. Kang, A. W. Hanson, B. Eaton and V. Boekelheide, J. Am. Chem. Soc., 1985, 107, 1979. 17 S. Lopez, M. Kahraman, M. Harmata and S. W. Keller, Inorg. Chem., 1997, 36, 6138. 18 Gmelin Handbook of Inorganic Chemistry, Silver, Part B6, Springer, Berlin, 1975, pp. 346–353. 19 J. A. R. Navarro, J. M. Salas, M. A. Romero and R. Faure, J. Chem. Soc., Dalton Trans., 1998, 901; M. A. Withersby, A. J. Blake, N. R. Champness, P. Hubberstey, W.-S. Li and M. Schröder, Angew. Chem., Int. Ed. Engl., 1997, 36, 2327. 20 G. M. Sheldrick, SHELXL 97, Programs for Crystal Structure Analysis, University of Göttingen, 1997. 21 ORTEP 3 for Windows, L. J. Farrugia, J. Appl. Crystallogr., 1997, 30, 565; PLATON/PLUTON 97, A. L. Spek, Acta Crystallogr., Sect. A, 1990, 46, C34. Paper 8/07450J

ISSN:1477-9226    

DOI:10.1039/a807450j

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1999, 191–199 191 Ag1 ion complexation properties of N-phenylpolythiazaalkane derivatives: synthesis, crystallography, 1H NMR spectroscopy, potentiometry and metal ion recognition properties Junichi Ishikawa,a Hidefumi Sakamoto,*b Mutsumi Nakamura,a Kunio Doi a and Hiroko Wada a a Department of Applied Chemistry, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555, Japan b Department of Applied Chemistry, Faculty of Systems Engineering, Wakayama University, 930 Sakae-dani, Wakayama-shi, 640-8510, Japan.E-mail: skmt@sys.wakayama-u.ac.jp Received 20th July 1998, Accepted 28th October 1998 A series of N-phenylpolythiazaalkane derivatives; the cyclic derivatives 4-phenyl-1-thia-4-azacyclohexane 1, 7-phenyl-1,4-dithia-7-azacyclononane 2, 10-phenyl-1,4,7-trithia-10-azacyclododecane 3 and 13-phenyl-1,4,7,10- tetrathia-13-azacyclopentadecane 4 and acyclic derivatives 6-phenyl-3,9-dithia-6-azaundecane 5 and 9-phenyl- 3,6,12,15-tetrathia-9-azaheptadecane 6, have been studied towards complexation with Ag1 ion.Single crystals of two Ag(I) complexes, [Ag(2)2][CF3SO3] and [Ag(4)][CF3SO3] were prepared and their structures were determined in the crystalline state by X-ray diVraction. In [Ag(2)2][CF3SO3], two bidentate 2 ligands, in which two sulfur atoms act as coordination sites, sandwich Ag(I) to give a four-coordinate complex in near tetrahedral geometry. In [Ag(4)], Ag(I) enters into a cavity composed of four sulfur atoms to give a distorted tetrahedral geometry.The changes of the chemical shifts in 1H NMR spectroscopy by the addition of CF3SO3Ag indicate that 1 and 2 exhibit small downfield shifts only for the protons of the thioether moiety, while 3, 4, 5 and 6 show drastic shifts for all protons. Ag1 ion complexation with N-phenylpolythiazaalkane and polythiaalkane derivatives, which were used for comparison, was studied in acetonitrile solution by potentiometry. Results show that the complex stability is governed primarily by the number of sulfur donor atoms, and the nitrogen atom of the N-phenylpolythiazaalkane derivatives scarcely contributes to the stability of the complexes.The extraction of transition metal ions with N-phenylpolythiazaalkane derivatives was examined and very high Ag1 ion selectivity was observed for most of them. The extraction equilibria of the Ag(I) complexes of N-phenylpolythiazaalkane derivatives were studied and the extraction constants of the extracted complexes determined.Results indicate that the extractability of 1 : 1 complexes depends on their stability. In liquid membrane transport, all N-phenylpolythiazaalkane derivatives exhibited Ag1 ion selective transportability and the order for the Ag1 ion transport rate was 5 > 2 ª 3 > 4 ª 6 @ 1. Crown and azacrown ethers have been studied widely as hosts to recognize specific guest ions.1–12 The functional ability of the crown compounds is generally based on the cavity size of a ring, the molecular structure, the number of donor atoms, and the nature of donor atoms.Thiacrown ethers incorporating only sulfur atoms have been widely investigated as extracting reagents 13–26 for soft metal ions. The crystal and molecular structures of some Ag(I) complexes with thiacrown ethers have been discussed using X-ray diVraction method.27–35 There were a few studies, however, concerning the metal ion complexabilities and selectivities for polythiazaalkane derivatives 36–42 containing both sulfur and nitrogen atoms as donor atoms on the crown rings.Especially, N-phenylpolythiazaalkane derivatives are important for application as coordination moieties for chromogenic reagents,43–46 prepared by combining N-phenylmonoazacrown ethers with organic dyes.47–49 In this study, we describe the correlation between Ag(I) complexation behavior and molecular structures for a series of macrocyclic N-phenylpolythiazaalkane derivatives, 1, 2, 3 and 4, and acyclic derivatives, 5 and 6 (Fig. 1) from the following points of view: (1) X-ray structural analysis for the complexes [Ag(2)2][CF3SO3] and [Ag(4)][CF3SO3]; (2) conformational analysis for Ag(I) complexes containing polythiazaalkane moieties by 1H NMR titration measurement; (3) stability constants for the Ag(I) complexes; (4) metal ion recognition properties on solvent extraction and Ag(I) extraction equilibria; (5) bulk liquid membrane transport of Ag1 ion.Results and discussion Syntheses Cyclic N-phenylpolythiazaalkane derivatives, 2 and 4, and acyclic derivatives, 5 and 6, were synthesized by methods described previously.42,44 Compound 1 was synthesized by the cyclization reaction of N,N-bis(p-tosylsulfonyloxyethyl)aniline with Na2S and was obtained in moderate yield. Compound 3 was synthesized by the cyclization reaction of 3-thiopentane-1,5-dithiol with N,N-bis(2-iodoethyl)aniline in the presence of Cs2CO3 as base in DMF.Cyclization reaction using Cs2CO3 is known to be superior in terms of the yield of macrocyclic compound to the reaction using sodium ethoxide as a base,50 although sodium ethoxide has been used as a base for synthesis of alkyl sulfides by the reaction of thiol with halides.51,52 This reaction gave 3 in good yield; no compound formed by the 2 : 2 cyclization reaction of the reactants was isolated. X-Ray structure of complexes [Ag(2)2][CF3SO3] and [Ag(4)]- [CF3SO3] A colorless crystal of complex [Ag(2)2][CF3SO3] was grown by vapor diVusion of acetonitrile from a solution containing CF3SO3Ag and 2 in a mole ratio of 1 : 2.Fig. 2 shows the structure of [Ag(2)2][CF3SO3]. Selected bond lengths and angles are listed in Table 1. The averages of Ag–S bond distances and192 J. Chem. Soc., Dalton Trans., 1999, 191–199 Fig. 1 Structural formulae of N-phenylpolythiazaalkane derivatives used here.N S N S S N S S S N S S S S Hc Hc Hc Hc Hb Ha Hb Ha Hb Ha Hb Ha H2 H1 H2 H1 H3 H2 H1 H4 H3 H4 H3 H5 H1 H2 N S S N S S S S Hc Hc Hb Ha Hb Ha H2 H1 H3 H1 H2 H4 H5 H6 H3 H4 S S S S 11 ( n = 1) 12 ( n = 2) 3 5 2 6 4 1 n 7 ( n = 0) 8 ( n = 1) 9 ( n = 2) 10 ( n = 4) n Fig. 2 Single-crystal X-ray structure of [Ag(2)2][CF3SO3] with atom numbering scheme adopted. chelating S–Ag–S angles are 2.58 Å and 84.128, respectively. The Ag–N distances are 3.863(8) and 3.884(0) Å and the nitrogen atoms are located appreciably away from Ag(I). The Ag(I) is sandwiched between two 2 ligands and coordinated in an exo–exo form by two pairs of two sulfur atoms of each ligand and the coordination geometry is close to tetrahedral.The S–Ag–S angles are similar to those found for the following complexes: 84.48 (average) for tetrahedral [Ag(8)Cl];27 82.18 for square pyramidal [Ag2L2]21 (L = 1,4,7,10,13-pentathiacyclopentadecane); 28 77.43 and 80.358 for octahedral [Ag(10)]1;29 80.98 for octahedral [Ag(8)2]1.27 The torsion angles of the N(1)– C(7) axis to all C–N–C–C bonds and the surrounding bond angles of nitrogen atoms indicate that the CAr–N(CR)2 unit has planar NC3 geometry (mean valence angle for Nsp2 > 117.58).53 Thus C(1) and C(6) lie nearly in the phenyl plane, the methylene hydrogens being located somewhat away from the phenyl Table 1 Selected bond lengths (Å) and angles (8) for [Ag(2)2][CF3SO3] Ag–S(1) Ag–S(2) Ag–S(3) S(1)–Ag–S(2) S(1)–Ag–S(3) S(1)–Ag–S(4) S(2)–Ag–S(3) S(2)–Ag–S(4) S(3)–Ag–S(4) 2.684(2) 2.500(2) 2.562(2) 83.75(6) 98.14(5) 127.12(6) 146.72(6) 120.81(6) 84.49(5) Ag–S(4) N(1)–C(1) N(2)–C(19) C(1)–N(1)–C(6) C(1)–N(1)–C(7) C(6)–N(1)–C(7) C(13)–N(2)–C(18) C(13)–N(2)–C(19) C(18)–N(2)–C(19) 2.577(2) 1.450(7) 1.400(7) 118.8(5) 118.5(5) 118.5(5) 118.2(5) 119.4(5) 119.1(5) moiety.The N(1)–C(7) and N(2)–C(19) bond lengths are slightly longer compared with planar CAr–Nsp2 (1.371 Å).53 Similarly to [Ag(2)2][CF3SO3], colorless crystals of complex [Ag(4)][CF3SO3] were obtained from a CF3SO3Ag solution containing an equimolar amount of 4.Fig. 3 shows the structure of [Ag(4)][CF3SO3] and selected bond lengths and angles are listed in Table 2. Ag(I) lies in a cavity composed of four sulfur atoms to give a four-coordinate distorted tetrahedral complex. The average S–Ag–S bond angles of three-connected five-membered ethylene rings, i.e., S(1)–Ag–S(2), S(2)–Ag–S(3) and S(3)–Ag– S(4), is 83.48.The resulting large S(1)–Ag–S(4) bond angle [136.66(7)8] makes it advantageous for Ag(I) to interact electrostatically with the nitrogen atom on the opposite side. The Ag–S(1) (2.444 Å) and Ag–S(4) (2.540 Å) bond distances are shorter than Ag–S(2) and Ag–S(3) and similar to those of Ag(I) complexes of exo and/or polymeric conformation.54–56 The Ag–N distance [3.234(4) Å] is shorter than the sum of the van Table 2 Selected bond lengths (Å) and angles (8) for [Ag(4)][CF3SO3] Ag–S(1) Ag–S(2) Ag–S(3) S(1)–Ag–S(2) S(1)–Ag–S(3) S(1)–Ag–S(4) S(2)–Ag–S(3) S(2)–Ag–S(4) 2.444(2) 2.827(2) 2.607(2) 84.54(6) 136.66(7) 137.18(7) 79.85(6) 101.98(6) Ag–S(4) N–C(11) S(3)–Ag–S(4) C(1)–N–C(10) C(1)–N–C(11) C(10)–N–C(11) 2.540(2) 1.441(9) 85.80(6) 112.0(6) 116.8(6) 111.7(6)J. Chem.Soc., Dalton Trans., 1999, 191–199 193 Fig. 3 Single-crystal X-ray structure of [Ag(4)][CF3SO3] with atom numbering scheme adopted. Fig. 4 The changes in 1H NMR chemical shifts for the typical protons of N-phenylpolythiazaalkane derivatives by titration of CF3SO3Ag in CD3CN.Each symbol in the plots refers to the assignment of the protons indicated in Fig. 1. der Waals radii (3.5 Å) 57 of the atoms. This fact indicates that there is an interaction between the Ag(I) and the nitrogen atom, as supported by 1H NMR studies (vide infra). The torsion angles of the N–C(11) axis to all C–N–C–C bonds and the surrounding bond angles of nitrogen atoms indicate that the CAr–N(CR)2 unit has tetrahedral NC3 geometry, with valence angles for Nsp3 of 108–1148.53 The N–C(10) bond makes an angle of ca. 708 relative to the phenyl plane, in which the C(10) methylene hydrogens are fairly close to the phenyl moiety owing to the tetrahedral NC3 geometry. The N–C(11) bond length is longer than those of planar CAr–Nsp2 and pyramidal CAr–Nsp3 (1.426 Å),53 but fairly short compared to CAr–N1–C3 (1.465 Å).53 Ag(I)-induced changes in 1H NMR chemical shifts Ag1 ion binding behavior was examined by 1H NMR spectroscopy in CD3CN.The 1H NMR spectral changes upon addition of CF3SO3Ag to each N-phenylpolythiazaalkane solution revealed that the formation and the dissociation of Ag(I) complexes were fast. Plots of the Ag(I)-induced 1H NMR chemical shifts of protons of N-phenylpolythiazaalkane derivatives vs. the molar ratio CF3SO3Ag: ligand (]] ] aL) for 7 × 1023 mol dm23 ligand solutions are shown in Fig. 4. The addition of CF3- SO3Ag to a solution containing 1 causes gradually and continuously downfield shifts of all the proton signals even at aL > 1 because of the low Ag1 ion complexability. The binding behavior of cyclic analog, 2, containing two sulfur atoms diVers from those of the other analogs.The plot for 2 displays two break points at aL = 0.5 and 1.0. This fact indicates that 2 forms a 1:2 [Ag(I) : ligand] complex below aL = 0.5 and then a 1 : 1 complex at aL > 0.5.For the other analogs, only one break point for each proton signal is observed clearly at aL = 1, and demonstrates that Ag1 ion forms predominantly 1 : 1 complexes under the experimental conditions. The extents of the changes in 1H NMR chemical shift (ppm)194 J. Chem. Soc., Dalton Trans., 1999, 191–199 Fig. 5 Ag1 induced changes in 1H NMR chemical shifts and assumed structures of the Ag(I) complex for N-phenylpolythiazaalkane derivatives. A plus sign (1) and a minus sign (2) denote shifts of proton signals to lower and higher magnetic fields, respectively.N S N N S S S N S S S S Hc Hc Hc Hc Hb Ha Hb Ha Hb Ha Hb Ha H2 H1 H2 H1 H4 H3 H4 H3 H5 H1 H2 N S S N S S S S Hc Hc Hb Ha Hb Ha H2 H1 H3 H1 H2 H4 H3 H4 3 5 2 6 4 1 Ag+ Ag+ H1 H2 S S H3 Ag+ Ag+ Ag+ Ag+ H6 H5 +0.03 +0.07 +0.40 +0.42 –0.28 +0.07 +0.17 –0.06 +0.07 +0.16 +0.16 –0.26 +0.41 +0.18 +0.52 +0.55 +0.20 +0.50 –0.20 +0.04 +0.21 +0.21 +0.01 +0.01 +0.01 +0.03 +0.02 +0.06 +0.14 +0.01 –0.01 +0.13 –0.03 +0.46 +0.20 +0.45 +0.09 –0.29 +0.13 induced by the addition of equimolar CF3SO3Ag are illustrated schematically in the structural formulae of Ag(I) complexes (Fig. 5). The Ag(I)-induced changes in chemical shift for the protons of N-phenylpolythiazaalkane derivatives are conveniently divided into three groups: downfield shifts for the protons of thioether moiety, downfield shifts for the phenyl protons, and upfield shifts for the protons of the dialkylamine moiety. First, when Ag1 ion interacts tightly with sulfur atom(s), the bound Ag(I) withdraws electron density from the protons on the sulfide moiety to cause downfield shifts of the chemical shifts.Secondly, the decrease in the p-electron density of the phenyl group is induced by electrostatic interaction between the nitrogen atom and the Ag(I) coordinated to sulfur atoms, resulting in downfield shifts for the phenyl protons. Thirdly, as already discussed by Alfimov et al.,58 the increase in electron density on the nitrogen atom is induced by the electrostatic interaction with Ag(I), while the electron densities of the neighboring methylene protons of the nitrogen atom are decreased by the electron withdrawing phenyl group when the ionophores bearing a benzothiazole moiety are in the free form.The ring-current eVects of the adjacent aromatic group on the methylene protons (H1), caused by conformational change due to the complexation with Ag1 ion, may also cause an up-field shift.58 For cyclic analogs, 1 and 2, with a small crown ring, changes in chemical shift are observed only for methylene protons of the sulfide moiety and the downfield shifts of the phenyl protons are slight.As mentioned above, Ag(I) coordinated to 2 in an exo–exo form is distinct from the nitrogen atom, and the electrostatic interaction between the nitrogen atom and the Ag(I) coordinated to sulfur atom(s) is very weak. Downfield shifts of phenyl protons by the addition of equimolar CF3SO3Ag were observed for ligands 3–6.This indicates that the Ag(I) coordinated to sulfur atoms interacts electrostatically with the nitrogen atom of the polythiazaalkane moiety. The extents of downfield shifts of the phenyl protons of the ligands are similar to each other. A macrochelate ring S–C–C–N–C–C–S with Ag(I) is formed as seen in the X-ray structure of [Ag(4)][CF3SO3], thus ligands 3–6 probably adopt a similar conformational arrangement. A relationship between the p-electron density in the aromatic rings and the chemical shift of the proton, Ds = 9.54Dr, was observed,59 where Ds and Dr are the changes in the shielding constant and the p-electron density, respectively, relative to benzene.The percentage decrease in electron density of the phenyl moiety upon Ag1 ion complexation are estimated to be 18, 21, 19 and 16% of an electronic charge for 3, 4, 5 and 6, respectively. The changes of the chemical shifts of phenyl protons, Ha, Hb and Hc, reveal dramatic ortho–para directing eVects when the Ag(I) complexes are formed.This result also demonstrates that the nitrogen atom also interacts with Ag(I) in solution. Potentiometry The stability constants of N-phenylpolythiazaalkane derivatives (L) with Ag1 ion were determined using acetonitrile as a solvent by potentiometric titration. The stoichiometric relationships are given by equations (1) and (2) and the succes- CAg = [Ag1] 1 [AgL1] 1 2[Ag2L21] 1 [AgL2 1] (1) CL = [L] 1 [AgL1] 1 [Ag2L21] 1 2[AgL2 1] (2) sive stability constants of the Ag(I) complexes are defined as KAgL = [AgL1]/([Ag1][L]), KAg2L = [Ag2L21]/([AgL1][Ag1]) and KAgL2 = [AgL2 1]/([AgL1][L]).Constants giving a minimum weighted sum of the squares of the deviations in pAg in equation (3) 60 where w = 1/(pAgi 1 1 2 U = Sw(pAgobs 2 pAgcal)2 (3) pAgi 2 1)2, were calculated by non-linear regression. The standard deviation in pAg units was evaluated from a titration of 25– 35 data points by the use of the following equation: sfit = (U/ Sw)1/2.The formation of higher N-phenylpolythiazaalkane complexes such as AgL3 and AgL4 or dimer complexes such as Ag2L2 was not observed under the experimental conditions used here. The stability constants of Ag(I)–polythiaalkane complexes were also determined for comparison. The results for N-phenylpolythiazaalkane complexes together with those for polythiaalkane complexes are listed in Table 3.It is seen from Table 3 that 6 forms the most stable 1 : 1 complex among N-phenylpolythiazaalkane derivatives and the order of complexability for Ag1 ion is 6 > 3 ª 4 > 2 ª 5 > 1. The value of log KAgL for 2 is about twice that for monodentate ligand 11, since 2 acts as a bidentate ligand upon complexation with Ag1 ion. The stabilities of Ag(I) complexes of polythiaalkane derivatives have a similar magnitude to those of polythiazaalkane derivatives. Logarithmic values of KAgL were plotted against the number of sulfur atoms of the ligands in Fig. 6 and illustrates that the stability of the complex is primarily dependent on the number of sulfur atoms of the complexing parts rather than the structure of the ligand. By contrast, the crystal X-ray diVraction data showed a macrochelate ring of the Ag(I) complex of 4 and the Ag(I)-induced changes wereJ. Chem. Soc., Dalton Trans., 1999, 191–199 195 observed by 1H NMR measurement. The tendency of the stability constants shows that such an interaction between complexed Ag(I) and nitrogen, however, is too weak to aVect the stability constant of the Ag(I) complex with N-phenylpolythiazaalkane derivatives.In the crystal of [Ag(4)][CF3SO3], Ag(I) is included in three linked five-membered chelate rings, in which the Ag–S(1) and Ag–S(4) distances are much shorter than Ag–S(2) and Ag–S(3). The strain of three linked chelate rings for [Ag(4)][CF3SO3] seems to be larger than that for [Ag(2)2][CF3SO3] and should be why the value of KAgL of the [Ag(4)]1 complex is smaller than that of the overall stability constant of [Ag(2)2]1 (log b2 = 6.7) without taking into account a chelate eVect.Further, the stability of [Ag(4)]1 is lower than that of [Ag(6)]1 (log KAgL = 6.47) being similar to the overall stability constant of [Ag(2)2]1. The result demonstrates that the strain of three linked chelate rings and the rigidity of the ring structure reduces the stability of the Ag(I) complex with 4.Solvent extraction behavior The distribution of N-phenylpolythiazaalkane derivatives in aqueous acidic solution–1,2-dichloroethane was examined. The distribution of N-phenylpolythiazaalkane derivatives into the aqueous phase increased gradually with an increase in the concentration of nitric acid due to the protonation of a nitrogen atom to form the cationic HL1 species. The relationship between the percentage for each N-phenylpolythiazaalkane derivative in the organic phase and log [HNO3] in the aqueous Fig. 6 Plots of log KAgL and log Kex11 vs. number of sulfur atom(s) on the polythiazaalkane moiety. Closed and open symbols in plots represent the stability and the extraction constants, respectively. Table 3 Stability constants of Ag(I) complexes in acetonitrile a Ligand 123456789 10 11 12 log KAgL 1.71 3.70 5.92 5.67 3.59 6.47 1.82 5.69 6.09 8.03 2.20 3.38 log KAg2L 1.2 2.2 1.6 1.5 0.7 log KAgL2 1.3 3.0 1.7 2.4 1.5 1.5 2.7 2.4 1.3 3.2 sfit b 0.0055(25) 0.0043(35) 0.0872(20) 0.0068(20) 0.0078(25) 0.0257(22) 0.0049(21) 0.0155(20) 0.0096(29) 0.0065(20) 0.0194(23) 0.0114(20) a [TMAP] = 0.1 mol dm23, at 25 8C.b Number of data points is given in parentheses. phase indicates that all ligands except for 1 were entirely distributed in the organic phase in the range of log [HNO3] < 0.5. The metal ion recognition properties for N-phenylpolythiazaalkane derivatives were examined by solvent extraction.The metal ion complex is extracted with a counter anion as an ion-pair complex from the aqueous phase when the N-phenylpolythiazaalkane derivative used is a neutral ligand. Therefore, nitrate ion was used as a counter anion to estimate the Ag1 ion extractability and the extraction equilibrium constants for the ion-pair complexes. The results of solvent extraction of transition metal ions with N-phenylpolythiazaalkane derivatives are summarized in Table 4. No extraction of any divalent transition metal ions, even Hg21 which is well known to have a high aYnity for thiacrown ethers,14–19 was observed for all Nphenylpolythiazaalkane derivatives under the conditions used here. It is noteworthy that N-phenylpolythiazaalkane derivatives except for 1 exhibited a remarkably high Ag1 ion selectivity.The extractabilities of macrocyclic derivatives for Ag1 ion increased with the increase of the number of sulfur atoms in the ligand, and the order of the extractabilities is 4 > 3 > 2 @ 1; 1 showed no extractability for any metal ions, even for Ag1 ion, while 4 exhibited the highest Ag1 ion extractability (>95%).For acyclic derivatives, the extractability of 6 for Ag1 ion is much higher than that of 5. The eVect of pH change on Ag1 ion extraction percentage, E(%), for each N-phenylpolythiazaalkane derivative was examined under the conditions detailed in Table 4, and no change of the value of E(%) was observed in the range pH 1–7.This fact suggests that no cationic HL1 species forms in the aqueous phase under such conditions. The extraction equilibria of the complexes were examined by changing the concentrations of nitrate ion and ligand. If the composition of the extracted species is assumed to be 1 :m: n for Ag(I) : ligand :NO3 2, the extraction equilibrium and the constant, Kex, are defined by equations (4) and (5) and the distribution ratio, DAg, of Ag1 ion Ag1 1 m (L)O 1 nNO3 2 (AgLm(NO3)n)O (4) Kex = [AgLm(NO3)n]O/[Ag1][L]O m[NO3 2]O n (5) is given by equation (6) where the subscript ‘O’ refers to con- DAg = [AgLm(NO3)n]O/([AgLm(NO3)n] 1 [AgLm 1] 1 [Ag1]) (6) centration in the organic phase.If the concentrations of AgLm(NO3)n and AgLm complexes are much lower than that of Ag1 ion in the aqueous phase, the denominator of equation (6) can be expressed by [Ag1]. If [L]O @ [AgLm(NO3)n]O, the logarithmic form of equation (5) is rewritten by the substitution of equation (6) as equation (7).log DAg = log Kex 1 m log [L]O 1 n log [NO3 2] (7) Plots of log DAg vs. log [NO3 2] gave straight lines with a slope of unity for all ligands. The plots of log DAg 2 log [NO3 2] vs. log [L]O for the N-phenylpolythiazaalkane derivatives 3–6 also give straight lines with a slope of unity as shown in Fig. 7. The results demonstrate that the ion-pair complexes AgL(NO3) can be extracted into the organic phase. On the other hand, the plot for 1 gives a straight line with a slope of two, indicating that the extractive species is AgL2(NO3).For the plot for 2, the slope of the straight line is shifted from one to two around 2log [L]O = 3. The extractive species, therefore, changes from AgL(NO3) to Ag(L)2(NO3) above log [L]O = 23. The values of the extraction equilibrium constants, Kex, are summarized in Table 5. It is clear that the order of Kex for the 1:1:1 complexes, AgL(NO3), is 6 > 4 > 3 > 2 > 5 @ 1.Both upward curves of the plots of log KAgL and log Kex11 vs. the number of sulfur atoms are similar to196 J. Chem. Soc., Dalton Trans., 1999, 191–199 Table 4 Metal ion extraction a Extraction quantity b (%) Ligand 123456 Mn(II) 000000 Fe(II) 000000 Co(II) 000000 Ni(II) 000000 Cu(II) 000000 Zn(II) 000000 Pb(II) 000000 Cd(II) 000000 Ag(I) 0 40 62 95 17 >99 Hg(II) 000000 a Organic phase: [ligand] = 2 × 1024 mol dm23 in 1,2-dichloroethane; aqueous phase: [metal ion] = 5 × 1025 mol dm23, [KNO3] = 0.1 mol dm23, pH 1.5.b Evaluated from the metal ion concentration in the aqueous phase. each other as shown in Fig. 6. Plots of log Kex11 vs. log KAgL give a straight line with a slope of unity. The result suggests that the extractability of the N-phenylpolythiazaalkane derivatives for Ag1 ion is mainly dependent on the stability of the complex. Liquid membrane transport The Ag1 ion transportabilities of N-phenylpolythiazaalkane derivatives as neutral carriers were examined in a bulk transport system using a liquid membrane.A source phase and a receiving phase were simultaneously in contact with a liquid membrane phase composed of a 1,2-dichloroethane solution of the ligand. In this study, Ag1 ion is transported as a ternary Ag(I) complex through the membrane phase. The transport system used here undergoes a symport process, the motive force being the diVusion of the Ag(I) complex through the liquid membrane. The transport behavior of Ag1 ion through the liquid membranes containing N-phenylpolythiazaalkane derivatives is shown in Fig. 8. All of the compounds exhibited transportability for Ag1 ion and the amount of Ag1 ion transported to Fig. 7 Plots of log DAg 2 log [NO3 2]O vs. log [L]. Aqueous phase: [Ag1] = 1 × 1025 mol dm23 at pH = 5.4. 1, (j); 2, (d); 3, (m); 4, (r); 5, (n); 6, (s). Table 5 Extraction constants for Ag(I) complexes a Ligand 123456 log Kex11 b 4.57 ± 0.07 4.98 ± 0.04 6.14 ± 0.03 4.04 ± 0.05 7.31 ± 0.02 log Kex12 c 3.33 ± 0.12 7.83 ± 0.08 a 1,2-Dichloroethane–water biphasic system.b Kex11 = [AgL(NO3)]O/ [Ag1][L]O[NO3 2]. c Kex12 = [AgL2(NO3)]O/[Ag1][L]O 2[NO3 2]. the receiving phase increased almost linearly for each ligand with running time. The transport rates for the ligands were calculated from Fig. 8. The transportability of Ag1 ion decreased in the order: 5(3.6 ± 0.09) > 2(1.8 ± 0.09) ª 3(2.0 ± 0.04) > 4(1.4 ± 0.10) ª 6(1.5 ± 0.04) @1(0.08 ± 0.008), where the values in parentheses are the Ag1 ion transport rates (1027 mol h21).An approximately negative correlation between the transport rates for Ag1 ion and the values of log Kex11 for the N-phenylpolythiazaalkane derivatives, except for 1, was observed as shown in Fig. 9. Compound 1 exhibited much lower Ag1 ion transportability due to the extremely low Ag1 ion extractability. In the Ag1 ion transport system, the high Ag1 ion extractability is advantageous for the extraction of Ag1 ion into the membrane phase, although it is disadvantageous for the release of Ag1 ion from the membrane phase to the receiving phase.The balance of both processes is the most important factor governing the transportability. The release process seems, especially, to Fig. 8 Time-dependent profiles of silver ion membrane transport. The source phase (15 mL): [AgNO3] = 5 × 1023 mol dm23 (15 mL) and [H2SO4] = 0.01 mol dm23; the receiving phase (15 mL): [H2SO4] = 0.01 mol dm23; liquid membrane phase (15 mL): [ligand] = 2.5 × 1024 mol dm23 in 1,2-dichloroethane. 1, (j); 2, (d); 3, (m); 4, (r); 5, (n); 6, (s). Fig. 9 Plots of transport rate vs. log Kex11. Triangle and circle symbols in plots mean cyclic and acyclic polythiazaalkane derivatives, respectively.J. Chem. Soc., Dalton Trans., 1999, 191–199 197 be the rate-determining step for the Ag1 ion transport in this system and is the reason why 5, which has much lower Ag1 ion extractability than 6, exhibited the best Ag1 ion transportability.The membrane transport values for other metal ions such as Cu21 and Hg21 were also examined under similar experimental conditions. No metal ion transport was, however, observed because these metal ions could not be extracted from the source phase to the liquid membrane. These results are compatible with those of the solvent extraction experiments of the same transition metal ions. Experimental Materials N-Phenylpolythiazaalkane derivatives 2, 4, 5 and 6 were prepared as described previously.42,44 The reagents used here were of analytical grade and the other chemicals were of guaranteedreagent grade.All of the organic solvents were purified in the usual way. Water was doubly distilled. Instrumentation Melting points were determined with a YANACO melting point apparatus and were uncorrected. Mass spectra were measured with a JEOL JMS-DX303 instrument. The routine 1H NMR measurements were carried out with a Hitachi R-90 spectrometer with CDCl3 solutions containing tetramethylsilane as an internal standard.The specific 1H NMR measurements such as CF3SO3Ag titrations were carried out with a Varian XL-200 spectrometer. The pH and pAg measurements were made at 25.0 ± 0.5 8C using a TOA pH Meter HM-30S equipped with a TOA GST-5311C glass electrode and a Ag wire electrode, respectively. Electronic spectra were obtained on a Hitachi 150-20 spectrophotometer with 1 cm quartz cells.Extractions were carried out in a thermostatted chamber (25.0 ± 0.2 8C) with a TAITEC personal-10 incubator. The concentrations of metal ions in aqueous solutions were determined by a SEIKO SAS/727 atomic absorption spectrophotometer. Synthesis 4-Phenyl-1-thia-4-azacyclohexane 1. The tosylation of N,Nbis( 2-hydroxyethyl)aniline with p-tolylsulfonyl chloride in the presence of NaOH in water–THF solution gave N,N-bis(2-ptolylsulfonyloxyethyl) aniline. An acetone–water (1 : 1) solution (300 mL) of N,N-bis(2-p-tolylsulfonyloxyethyl)aniline (24.5 g, 0.05 mol) and Na2S (12.0 g, 0.05 mol) was stirred at reflux temperature for 2 h.After reaction, the mixture was concentrated and then 100 mL of water added. The solution was then extracted with CHCl3 (100 mL × 3) and the combined extract dried over MgSO4 and the solvent evaporated in vacuo. The residue was subjected to column chromatography (silica gel; eluent, benzene–CHCl3) to give 1 as a white solid.Yield: 6.84 g (76%). Mp 31–32 8C. 1H NMR (CDCl3): d 2.68–2.80 (m, 4 H, SCH2), 3.48–3.59 (m, 4 H, NCH2) and 6.85–7.35 (m, 5 H, ArH). EI mass spectrum: m/z 179 (M1) (Found: C, 66.73; H, 7.27; N, 7.73. C10H19NS requires C, 67.00; H, 7.31; N, 7.81%). 10-Phenyl-1,4,7-trithia-10-azacyclododecane 3. Iodination of N,N-bis(2-p-tolylsulfonyloxyethyl)aniline with NaI in acetone solution gave N,N-bis(2-iodoethyl)aniline. To dry DMF (500 mL) was added Cs2CO3 (4.24 g, 0.011 mol) and the solution stirred at 60 8C under a nitrogen atmosphere then a dry DMF solution (100 mL) containing 3-thiopentane-1,5-dithiol (1.54 g, 0.01 mol) and N,N-bis(2-iodoethyl)aniline (4.00 g, 0.01 mol) was added dropwise over 24 h.After the addition was complete, the mixture was stirred at 60 8C for 24 h. After the reaction, the mixture was concentrated, and then 200 mL of water was added. The solution was extracted with CHCl3 (100 mL × 4) and the combined extract washed twice with water, a 20% Na2S2O3 aqueous solution and water.The extract was dried over MgSO4 and the CHCl3 was evaporated in vacuo. The residue was purified by column chromatography (silica gel; eluent, hexane–benzene) to give 3 as a white solid. Yield: 1.57 g (52%). Mp 176–177 8C. 1H NMR (CDCl3): d 2.73–2.90 (m, 12 H, SCH2), 3.56 (t, 4 H, NCH2), 6.70–7.25 (m, 5 H, ArH). EI mass spectrum: m/z 299 (M1) (Found: C, 55.84; H, 6.93; N, 4.75. C14H21NS3 requires C, 56.14; H, 7.07; N, 4.68%).[Ag(2)2][CF3SO3]. Compound 2 (23.9 mg, 0.1 mmol) was dissolved in 10 mL acetonitrile solution containing 0.05 mmol CF3SO3Ag. The acetonitrile solution was stored in the dark and the solvent was removed by slow diVusion at room temperature and the residue was used for X-ray structure analysis. Yield: 64.7 mg (88%). Mp 185–186 8C. 1H NMR (CD3CN): d 2.94 (s, 4 H, SCH2), 2.98–3.02 (m, 4 H, SCH2), 3.71–3.76 (m, 4 H, NCH2), 6.78–7.31 (m, 5 H, ArH) (Found: C, 40.85; H, 4.73; N, 3.78.C25H34AgF3N2O3S5 requires C, 40.81; H, 4.66; N, 3.81%). [Ag(4)][CF3SO3]. Compound 4 (35.9 mg, 0.1 mmol) was dissolved in 10 mL acetonitrile solution containing 0.1 mmol CF3SO3Ag. The acetonitrile solution was stored in the dark and the solvent was removed by slow diVusion at room temperature and the residue was used for X-ray structure analysis. Yield: 56.2 mg (91%). Mp 198–199 8C. 1H NMR (CD3CN): d 2.72– 3.05 (m, 16 H, SCH2), 3.31–3.36 (m, 4 H, NCH2), 7.14–7.42 (m, 5 H, ArH) (Found: C, 33.14; H, 4.13; N, 2.23. C17H25AgF3- NO3S5 requires C, 33.12; H, 4.09; N, 2.27%).X-Ray structure determinations Crystallographic data for complexes, [Ag(2)2][CF3SO3] and [Ag(4)][CF3SO3], are listed in Table 6. Each crystal was mounted in a glass capillary. X-Ray diVraction measurements were made at room temperature with graphite monochromated Mo-Ka radiation on an Enraf-Nonius CAD4-EXPRESS fourcircle diVractometer for [Ag(2)2][CF3SO3] and a Rigaku R-AXIS IV imaging plate areas detector for [Ag(4)][CF3SO3].Cell dimensions for both crystals were determined from the setting angle values of 25 centered reflections with the CAD 4 diVractometer. Intensity data were corrected for Lorentz and polarization eVects. All structures were solved by heavy atom methods, and refined anisotropically for non-hydrogen atoms by full-matrix least-squares calculations. Table 6 Crystal data for [Ag(2)2][CF3SO3] and [Ag(4)][CF3SO3] Compound Formula M Crystal size/mm System, space group a/Å b/Å c/Å a/8 b/8 g/8 U/Å3 Z Dc/g cm23 F(000) m(Mo-Ka)/cm21 2qmax/8 No.of reflections measured No. of variables R, Rw a [Ag(2)2][CF3SO3] AgF3N2O3S5C25H34 735.72 0.4 × 0.3 × 0.2 Triclinic, P1� 11.346(9) 12.017(2) 13.398(7) 62.71(4) 69.77(0) 78.04(2) 1520.9(1) 2 1.606 752.00 10.53 52.6 6455 352 0.051, 0.058 [Ag(4)][CF3SO3] AgF3NO3S5C17H25 616.55 0.2 × 0.2 × 0.1 Triclinic, P1� 10.991(2) 12.252(2) 9.264(1) 106.55(1) 103.30(1) 90.62(2) 1159.8(4) 2 1.765 624.00 13.60 51.4 3983 271 0.064, 0.084 a R = S Fo| 2 |Fc /S|Fo|, Rw = [Sw(|Fo| 2 |Fc|)2|/Sw|Fo|2)]� �� , w = 4Fo 2/ s2(Fo)2.198 J.Chem. Soc., Dalton Trans., 1999, 191–199 Scattering factors and anomalous dispersion terms were taken from ref. 61. All hydrogen atoms were included for refinements, in which their positions were located from diVerent Fourier maps. All calculations were performed using the teXsan crystallographic software package of Molecular Structure Corporation.62 CCDC reference number 186/1227. 1H NMR titration measurements The 1H NMR titrations were performed in CD3CN and were recorded on Varian XL-200 spectrometer. The CD3CN contained 7 × 1023 mol dm23 ligand and variable amounts of CF3SO3Ag and the resulting chemical shifts were reported relative to the signal of tetramethylsilane (TMS) at 0 ppm. Potentiometric measurements The stability constants for Ag(I) complexes of N-phenylpolythiazaalkane and polythiaalkane derivatives were determined by potentiometric titration. All measurements were performed in acetonitrile solution containing 0.1 mol dm23 tetraethylammonium perchlorate (TEAP) at 25.0 ± 0.2 8C.Two titrations were performed to determine the stability constants. First, a solution of 1–20 mmol dm23 silver perchlorate was titrated with 1–20 mmol dm23 of a N-phenylpolythiazaalkane derivative. The Ag indicator electrode was calibrated by silver perchlorate solution without addition of titrant (titration ratio = 0).Secondary titration of 1–20 mmol dm23 of a N-phenylpolythiazaalkane derivative with 1–20 mmol dm23 silver perchlorate was done on the basis of the preliminary calibration using the solutions of a known concentration of silver perchlorate. The equilibrium concentration of Ag1 ion was evaluated as the negative logarithms value, pAg, from the electromotive force of the following electrochemical cell: Pt | 0.05 mol dm23 I2 1 0.1 mol dm23 NaI || 0.1 mol dm23 TEAP (s) || sample solution | Ag A titration curve was obtained as a plot of pAg vs.titration ratio. Solvent extraction In solvent extraction using N-phenylpolythiazaalkane derivatives, equal amounts (10 mL) of water and 1,2-dichloroethane were placed in a 50 mL stoppered centrifuge tube, and shaken for 10 min at 200 strokes min21. For the measurement of the distribution ratio of N-phenylpolythiazaalkane derivative, an aqueous solution containing nitric acid was shaken with a 1,2-dichloroethane solution containing a N-phenylpolythiazaalkane derivative at a concentration of 2 × 1024 mol dm23.The ligand concentration in the organic phase was estimated by absorption spectroscopy. In solvent extraction of metal ions, nitrate ion was chosen as the counter anion for the metal complex of the N-phenylpolythiazaalkane derivative. Extraction experiments for a comparison of the metal ion extractabilities were carried out as follows: An aqueous solution containing 5 × 1025 mol dm23 metal nitrate and 0.1 mol dm23 potassium nitrate and a 1,2-dichloroethane solution containing 2 × 1024 mol dm23 N-phenylpolythiazaalkane derivative was placed in a stoppered centrifuge tube.After shaking and then allowing the mixture to stand, the Ag1 ion concentration in the aqueous phase was determined by atomic absorption spectrometry. Distribution equilibria of the complexes of Ag(I)–N-phenylpolythiazaalkane –nitrate ion were examined as follows: The ionic strength of an aqueous solution containing 1 × 1025 mol dm23 silver nitrate was adjusted to 0.1 M using potassium nitrate and sulfate.The aqueous solution was shaken with 1,2-dichloroethane solution containing a known quantity of N-phenylpolythiazaalkane derivative. The silver ion concentration in the aqueous phase was measured by atomic absorption spectrometry, and the silver ion concentration in the organic phase was calculated from the amount of silver ion in the aqueous phase.Transport through a liquid membrane An apparatus (a dual cylindrical cell) for transport experiments across a liquid membrane was described as reported previously. 45 Both the inner aqueous source phase (15 mL) containing 5 × 1023 mol dm23 metal nitrate and 1 × 1022 mol dm23 H2SO4 and the outer receiving phase (15 mL) containing 1 × 1022 mol dm23 H2SO4 were in contact with the liquid membrane phase (15 mL) of neutral ligand in 2.5 × 1024 mol dm23 in 1,2-dichloroethane.The three phases in the transport cell were agitated carefully by a stirring bar at 200 r.p.m. on the bottom of the cell at 25.0 ± 0.2 8C. An aliquot of aqueous solution was taken from both the source and the receiving phases at regular time intervals to be subjected to atomic absorption spectrometry. Acknowledgements We thank Professor Hideki Masuda for the X-ray crystallography and Dr Akihiro Yoshino for 1H NMR measurements. References 1 C. J. Pedersen, Angew.Chem., Int. Ed. Engl., 1988, 27, 1021. 2 D. J. Cram, Angew. Chem., Int. Ed. Engl., 1988, 27, 1009. 3 J.-M. Lehn, Angew. Chem., Int. Ed. Engl., 1988, 27, 89. 4 K. E. Krakowiak, J. S. Bradshaw and D. J. Zamecka-Krakowiak, Chem. Rev., 1989, 89, 929. 5 J. S. Bradshaw, K. E. Krakowiak and R. M. Izatt, Tetrahedron, 1992, 48, 4475. 6 R. M. Izatt, J. S. Bradshaw, S. A. Nielsen, J. D. Lamb, J. J. Christensen and D. Sen, Chem. Rev., 1985, 85, 271. 7 R. M. Izatt, K. Pawlak and J.S. Bradshaw, Chem. Rev., 1991, 91, 1721. 8 R. M. Izatt, J. S. Bradshaw, K. Pawlak, R. L. Bruening and B. J. Tarbet, Chem. Rev., 1992, 92, 1261. 9 D. J. Cram, Angew. Chem., Int. Ed. Engl., 1986, 25, 1039. 10 G. W. Gokel, Chem. Soc. Rev., 1992, 39. 11 H. An, J. S. Bradshaw, R. M. Izatt and Z. Yan, Chem. Rev., 1994, 94, 939. 12 E. 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Fedorov, O. A. Fedorova, S. P. Gromov, R. E. Hester, J. A. K. Howard, L. G. Kuz’mina, I. K. Lednev and J. N. Moore, J. Chem. Soc., Perkin Trans. 2, 1997, 2249. 59 H. Günther, NMR Spectroscopy, John Wiley & Sons, Chichester, 2nd edn., 1995, pp. 71–78. 60 A. E. Martell and R. J. Motekaitis, Determination and Use of Stability Constants, VCH Publishers, New York, 2nd edn., 1992, pp. 19–26. 61 J. A. Ibers and W. C. J. Hamilton, International Tables for X-Ray Crystallography, Kynoch Press, Birmingham, 1974, vol. 4. 62 teXsan, Crystal Structure Analysis Package, Molecular Structure Corporation, The Woodlands, TX, 1985 & 1992. Paper 8/05618H

ISSN:1477-9226    

DOI:10.1039/a805618h

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, Pages 193–197 193 Oxidation of [Li4{(NBut)3S}2]: a new route to sulfur triimides ‡ Roland Fleischer, Stefanie Freitag and Dietmar Stalke *,† Institut für Anorganische Chemie der Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany The oxidation reactions of [Li4{(NBut)3S}2] with oxygen and halogens (bromine and iodine) were investigated. In all these reactions a radical intermediate [Li3{(NBut)3S}2]? was observed, which was investigated by ESR spectroscopy.While the reaction with oxygen leads to the dianionic sulfur(VI) species [Li2(NBut)3SO], oxidation with halogens yields N,N9,N0-tris(tert-butyl)sulfur triimide S(NBut)3. The latter reaction provides an easy access to sulfur triimides. Some intermediates from the reaction of [Li4{(NBut)3S}2] with halogens could be isolated and characterised by X-ray structure analyses. The intermediates can be rationalised as adducts of a lithium halide and a monomeric [Li2(NBut)2S] unit to give [(thf)3Li3(m3-X){(NBut)3S}] (X = Br or I).In the presence of oxygen the oxidation reaction of [Li4{(NBut)3S}2] with iodine affords an adduct of lithium iodide and the sulfate analogue [(thf)3Li3(m3-I){(NBut)3SO}] is obtained. As revealed by X-ray structure analysis, this adduct is very similar to [(thf)3Li3(m3-I){(NBut)3S}] in the solid state. Sulfur diimides were a major focus in the chemistry of sulfur– nitrogen compounds during the past twenty years.1 Initially we were interested in S(NR)2 2 to design RS(NR)2 2 as monoanionic ligands by nucleophilic addition of alkali-metal alkyls or aryls to the S]] N double bond of sulfur diimides.3 In order to expand this initial work, a metal amide instead of a metal alkyl was used in the addition reaction, yielding a tripodal, dianionic S(NR)3 22 ligand.4 There are only a couple of examples of these dianions described in the literature.5 Although fascinating from the start, the use of such dianions as ligands in co-ordination chemistry was hampered by their confusing redox properties.Even traces of an oxidant like oxygen led to a deep blue colour of the compound, indicating the presence of radical species. Since the landmark synthesis of the first sulfur triimide S(NR)3 by Glemser and Wegener in 1970 6 another versatile building block of sulfur–nitrogen chemistry, similar to the sulfur diimides is available. Unfortunately, sulfur triimides, in contrast to sulfur diimides, have not received general attention, all the reactions starting from sulfur triimides were reported by Glemser and Mews (for recent review see ref. 7). One of the reasons might be the limited synthetic access to the sulfur triimides. Until recently only two reactions were known in which the sulfur triimide backbone was formed. These syntheses starting from NSF3 6,8 or OSF4 9 are quite hazardous and give poor yields. Transimidation reactions provide limited access to asymmetrically substituted sulfur triimides.9,10 Sulfur-containing compounds show an ample redox chemistry.Many sulfur oxy acids are known with sulfur in oxidation states from III (dithionic acid H2S2O4) to VI (sulfuric acid H2SO4).11 They, as well as their salts, are related to each other by oxidation–reduction equilibria. Similar relationships between the corresponding sulfur–nitrogen compounds are expected, but while the redox properties of the sulfur–oxygen compounds are intrinsic, those of the sulfur–nitrogen compounds are dependent on the electronic properties of the nitrogen-bonded substituents.Therefore, the redox properties of the sulfur–nitrogen compounds are adjustable by variation of the electronic properties of the substituents. However, a detailed examination was hampered by the lack of convenient synthetic access to those species. Results and Discussion Iminosulfur diamides S(NR)3 22 are extremely sensitive to oxid- † E-Mail: dstalke@chemie.uni-wuerzburg.de ‡ Non-SI unit employed: G = 1024 T.ation. Even traces of oxygen, e.g. if handled in an argon 5.0 atmosphere without additional oxygen absorption, led to a dark blue colour of the solution and the solid state, indicating the presence of radicals. These radicals 12 are as stable as the S(NR)2~2 radical anion, reported by Hunter et al.12a and can be stored for several weeks. The nature of the radicals from the reaction of [Li4{(NBut)3S}2] 1 with oxygen was investigated earlier.4 An ESR spectrum of the radical in hexane solution displayed a signal even at room temperature.The hyperfine splitting of the signal, to give a septet (a = 8 G, intensity ratio 1:3:6:7:6:3:1) confirms that the single electron interacts with three equivalent 14N nuclei (I = 1). An additional hyperfine splitting (septet with a = 0.8 G, intensity ratio 1:2:3:4:3:2:1) was tentatively assigned to an interaction with two equivalent 7Li nuclei (I = ��� ), but the resolution was not high enough to be decisive.Reinvestigation, however, gave a better resolved ESR spectrum (Fig. 1). From this spectrum the second hyperfine splitting could be assigned to an interaction of the single electron with three equivalent 7Li nuclei (I = ��� , decet with a = 0.8 G). Lineshape analysis and simulation of the spectrum confirms this assignment (Fig. 2). The structure therefore can be deduced from the ESR spectrum. In the dimer of the radical monoanion S(NBut)3~2 and the dianionic S(NBut)3 22 three lithium cations are located between the cap-shaped ligands (Scheme 1).Similar radicals can be generated with the heavier alkali metals sodium and potassium. These radicals are stable enough to be investigated by X-ray structure analysis,13 revealing Fig. 1 The ESR spectrum of oxidised complex 1 in hexane solution194 J. Chem. Soc., Dalton Trans., 1998, Pages 193–197 structures similar to that proposed for the radical lithium complex 2 shown in Scheme 1.Since the radical is not the final product of these oxidation reactions, quantitative oxidation reactions of complex 1 were carried out. Reaction of [Li4{(NBut)3S}2] with oxygen When dry oxygen is bubbled through a solution of complex 1 in hexane under otherwise inert gas conditions, the mixture instantaneously turns dark blue. Fast interruption of the oxygen gas supply and heating of the dark blue solution causes a colour change to green, then reddish brown and finally colourless again.The same sequence of colours can be initiated by continuous oxygen gas supply to the solution of 1, although it stops at the reddish brown level. Unfortunately, no defined product could be isolated and purified either by distillation, or by crystallisation. Only after hydrolysis, could O2S(ButNH)2 be isolated and characterised. Work-up of this reaction mixture is difficult because it is almost impossible to react solutions of 1 with stochiometric amounts of oxygen.These drawbacks have been overcome by employing other oxidants like the halogens bromine and iodine. A plausible tentative mechanism for the oxidation of 1 with oxygen is nevertheless formulated in Scheme 2. Although complex 3 could not be isolated in this reaction, there are hints for the existence of such a compound from other reactions as discussed later. Reactions of [Li4{(NBut)3S}2] with halogens Two products can be isolated when bromine (or iodine) is used in the oxidation of complex 1.Dependent on the stochiometry, a lithium halide adduct of monomeric [Li2(NBut)3S] and S(NBut)3 4 can be isolated in variable yields. Right after the addition of halogen to a solution of 1 in thf–hexane, the mixture instantaneously turns dark blue as in the reaction with oxygen, and a precipitate is formed. In contrast to the reaction with oxygen the radical formed in this reaction is not stable. When addition of the halogen is interrupted, the colour slowly vanishes, leaving a white suspension. Further addition of halogen causes the solution to turn blue and, subsequently, to become colourless again not until 2 equivalents are added at the end of the oxidation.It should be noted that the final product of this oxidation reaction is the N,N9,N0-tris(tert-butyl)- sulfur triimide 4. Haction of 1 with 2 equivalents Fig. 2 Simulated ESR spectrum of the [Li3{(NBut)3S}2]? radical Scheme 1 Proposed structure of [Li3{(NBut)3S}2]? 2 in solution NBut S NBut ButN S NBut NBut Li Li ButN Li of halide provides easy access to sulfur triimides [equation (1), X = Br or I].[Li4{(NBut)3S}2] 1 2 X2 S(NBut)3 1 4 LiX (1) Structures of [(thf)3Li3(Ï3-X){(NBut)3S}] (X 5 Br or I) In oxidation reactions [equation (1)] with both bromine and iodine, the intermediate lithium halide adducts [(thf)3Li3- (m3-X){(NBut)3S}] (X = Br 5 or I 6) can be isolated. Maximum yield is reached by slow addition of the halogen to the reaction mixture in a 4 : 3 (1:X2) molar ratio.Crystallisation from thf– hexane solution yields X-ray quality crystals within 12 h storage at 220 8C. Complexes 5 and 6 crystallise in the orthorhombic space group Pnma. The isotypic monomeric structures are made up of one cap-shaped S(NBut)3 22 ligand, co-ordinating three lithium cations, and a halide, which is m3 bridging the metals. The co-ordination sphere of each lithium cation is completed by co-ordination of one thf molecule (Figs. 3 and 4 and Table 1). In both structures, ideal crystallographic C3 symmetry is precluded, owing to the formation of two short [Br]Li 266.0(4), I]Li 291.2(8) pm] and one longer [Br]Li 269.3(6), I]Li 296.0(12) pm] Li]X bonds. Nevertheless, the negative charge is completely delocalised in the S(NBut)3 22 ligands, as indicated by equally long S]N bonds [5 167.2(2), 6 165.6(5) pm, average]. Even the Li]N distances [5 206.1(4), 6 204.2(9) pm, average] are not influenced by the different Li]X distances.Compared to the Li]X distances in the solid-state structures Scheme 2 Tentative mechanism for the oxidation of complex 1 with O2(g) SVI NBut O O ButN H H heat 3 1 2 [Li4{(NBut)3SIV}2] + O2 2 [Li3{(NBut)3SIV}2]• + Li2O2 2 [Li2(NBut)3SIVO + [Li4{(NBut)3SIV}2] + 3 H2O –2 LiOH –ButNH2 Fig. 3 Solid-state structure of [(thf)3Li3(m3-Br){(NBut)3S}] 5 Fig. 4 Solid-state structure of [(thf)3Li3(m3-I){(NBut)3S}] 6J.Chem. Soc., Dalton Trans., 1998, Pages 193–197 195 of LiBr [274.4(7) pm] and LiI [300.0(7) pm],14 the Li]X distances in 5 [266.0(4) and 269.3(6) pm] and 6 [291.2(8) and 296.0(12) pm] are shortened due to the decreased co-ordination number of the halogen atom (six in the solid-state structures of LiX, X = Br or I, and three in the complexes 5 and 6). One hemisphere of the halide remains unco-ordinated in the complexes described and neither intra- nor inter-molecular longrange interactions have been detected.Reaction of [Li{S(NBut)3}2] with halogens in the presence of oxygen When the oxidation reaction of complex 1 with iodine is carried out in the presence of oxygen, the lithium iodide adduct [(thf)3Li3(m3-I){(NBut)3SO}] 7 (Fig. 5) is obtained. The reaction with oxygen as well as with iodine proceed simultaneously yielding a lithium iodide adduct of the sulfate analogue 3 and the sulfur triimide 4. Complex 7 emulates the same structural features as 5 and 6, although the complex contains a sulfur(VI) centre. The S1]O1s bond length of 145.5(5) pm is similar to the distance in the sulfate anion of 149.0 pm.15 The average S]N distance of 157.8 pm is 8.5 pm shorter than the related distance in 5 and 6 (average 166.3 pm).This seems to be a surprisingly high difference, especially when taking into account that only a bond shortening of 1–2 pm due to the higher oxidation state of the sulfur atom in 7 is expected.16 Fig. 5 Solid-state structure of [(thf)3Li3(m3-I){(NBut)3SO}] 7 Table 1 Selected bond lengths (pm) and angles (8) for complexes 5, 6 and 7 X S1]N1 S1]N2 S1]N3 S1]O1s Li1]N1 Li1]N2 Li2]N1 Li1]N3 Li2]N2 Li2]N3 Li3]N1 Li3]N2 Li1]X1 Li2]X1 Li3]X1 N1]S1]N2 N1a]S1]N2 N1]S1]N1a N2]S1]N3 N3]S1]N1 5 Br 167.2(2) 166.6(2) 205.5(4) 204.9(4) 207.1(4) 266.0(4) 269.3(6) 100.37(8) 100.37(8) 100.37(12) 6 I 165.4(4) 165.9(6) 204.1(9) 203.6(9) 204.3(10) 291.2(8) 296.0(12) 100.4(2) 100.4(2) 100.5(3) 7 I 157.7(6) 157.4(7) 158.2(7) 145.5(5) 215(2) 201(2) 199.7(13) 214.5(14) 196(2) 215(2) 285(2) 285(1) 285(1) 102.9(4) 102.3(4) 103.9(4) Comparison of oxidation with oxygen and halogens Although the oxidation of complex 1 with oxygen and halogens yields a radical after the first step, both reactions differ considerably afterwards.While in the first case the radical is quite stable, in the latter it is not. Presumably the structure of the radical is the same in both reactions, i.e.a dimer of the radical monoanion S(NBut)3~2 and the dianionic S(NBut)3 22 with three lithium cations between the cap-shaped ligands, the crucial difference must be caused by the formation of another species, also present in the reaction mixture. If the dimeric structure of the radical is broken down by formation of the halide adduct 5 (6), a destabilised monomeric radical {[Li(NBut)3S]?} is left. This radical monomer, in contrast to the dimer, easily undergoes redox disproportion, to yield the sulfur triimide 4 and monomeric [Li2(NBut)3S].In the reaction of halides with 1 four steps [equations (2)–(5), X = Br or I] can be distinguished. The 2 [Li4{(NBut)3S}2] 1 X2 2 [Li3{(NBut)3S}2]? 1 2 LiX (2) 2 [Li3{(NBut)3S}2]? 1 2 LiX 2 [Li3X(NBut)3S] 1 2 [Li(NBut)3S]? (3) 2 [Li(NBut)3S]? ��� [Li4{(NBut)3S}2] 1 S(NBut)3 (4) 2 [Li3X(NBut)3S] 1 X2 2 [Li(NBut)3S]? 1 3 LiX (5) first step of the reaction is a fast one-electron oxidation of 1, to yield the dimeric radical [Li3{(NBut)3S}2]? and LiX [X = Br or I; equation (2)].In the second step, the dimeric structure of the radical is broken down by formation of the halide adduct (5 and 6) and the radical monomer {[Li(NBut)3S]?; [equation (3)]}, followed by a redox disproportionation to give 4 and ��� [Li4- {(NBut)3S}2] [equation (4)]. On further addition of halogen the halide adduct itself can undergo a similar one-electron oxidation to 1 resulting in the same radical monoanion [equation (5)].However, it is stable enough to be isolated and characterised. The reaction of 1 with oxygen is very different. Instead of breaking down the dimeric structure of the radical by formation of an adduct, Li2O2 oxidatively adds to the S]] N double bond of the radical, upon heating. The intermediate product in this oxidation is proposed in Scheme 2. Conclusion The S(NR)3 22 dianions have several very intriguing properties, which provide many further opportunities for both synthetic and co-ordination chemistry.The most important properties are: (i) variable electronic structure. Depending on the electronic requirements, different resonance forms of the ligand can be utilised, by which the charges of the co-ordinated cations are stabilised. The electronic flexibility also facilitates stabilisation of unusual electronic states such as radicals. (ii) Easy oxidisability. Metal activation in the S(NR)3 22 complexes enables facile oxidation.In all oxidation reactions of S(NBut)3 22, a stable radical intermediate is formed as shown previously, but the final products are dependent on the oxidant. In the reaction with molecular oxygen (ButN)3SO22 is probably formed, while the neutral SVI species, sulfur triimide, is formed when halogens are employed. The latter reaction is a straightforward synthesis for sulfur triimides S(NR)3 providing general access to this class of compounds. (iii) Cap-shaped geometry. The co-ordination chemistry of S(NBut)3 22 is unique among the chelating nitrogen ligands due to the two negative charges and its cap-shaped geometry.The combination of cap-shaped geometry and steric demand of the nitrogen-bonded substituents should enable homoleptic metal(II) complexes to form. (iv) Lewis-base character of the sulfur atom. Owing to its oxidation state the central sulfur atom has a stereochemically active lone pair. This196 J. Chem. Soc., Dalton Trans., 1998, Pages 193–197 Table 2 Crystal data and structure refinement for complexes 5, 6 and 7 Empirical formula M T/K Crystal system Space group a/pm b/pm c/pm b/8 U/nm3, Z Dc/Mg m23 m/mm21 F(000) Crystal size/mm q Range/8 Limiting indices Reflections collected Independent reflections R(int) Data, restraints, parameters Absorption correction Transmission (max., min.) Goodne F2 R1 [I > 2s(I)] wR2 (all data) g1, g2 Largest difference peak, hole/e nm23 5 C24H51BrLi3N3O3S 562.47 193(2) Orthorhombic Pnma 1463.43(2) 1610.63(1) 1392.04(2) 90 3.28110(7), 4 1.139 1.341 1200 0.5 × 0.4 × 0.4 2.78–28.40 0 < h < 19, 0 < k < 21, 0 < l < 18 45 785 4239 0.0339 4239, 258, 257 Semiempirical 0.715, 0.651 1.335 0.0441 0.0964 0.023, 2.14 328, 2280 6 C24H51ILi3N3O3S 609.46 193(2) Orthorhombic Pnma 1423.1(5) 1638.8(2) 1394.9(2) 90 3.2532(13), 4 1.244 1.074 1272 0.5 × 0.5 × 0.3 3.12–22.52 215 < h < 15, 0 < k < 17, 22 < l < 15 2546 2216 0.1414 2216, 249, 233 Semiempirical 0.773, 0.765 1.047 0.0497 0.1397 0.099, 0.80 978, 2934 7 C24H51ILi3N3O4S 625.46 153(2) Monoclinic P21/n 993.1(3) 2265.0(7) 1484.1(3) 99.18(2) 3.295(2), 4 1.261 1.064 1304 0.8 × 0.4 × 0.4 3.04–22.55 210 < h < 10, 224 < k < 24, 216 < l < 16 8770 4319 0.0841 4318, 786, 469 Semiempirical 0.684, 0.410 1.050 0.0680 0.1915 0.097, 5.71 1305, 21535 lone pair not only causes the pyramidal geometry, which results in the cap shape of the ligand, but also gives rise to the Lewisbase character of the sulfur atom.Hence, it should be possible to facilitate S- as well as N-co-ordination. This dianion is therefore a prime candidate to host hard as well as soft Lewis acids each in a suitable fashion. Experimental All manipulations were performed under an inert gas atmosphere of dry N2 with Schlenk techniques or in an argon glovebox. All solvents were dried over Na–K alloy and distilled prior to use. The NMR spectra were obtained on Bruker AM 250, MS 400 or DMX 300 instruments at 25 8C using SiMe4 as external standard.Melting points and decomposition temperatures were measured by differential thermoanalysis using a DuPont Thermal Analyzer TA 9000. Owing to the easy oxidisability no mass spectra were recorded and no elemental analysis is available. Syntheses S(NBut)3 4. Compound 1 was prepared according to a literature procedure.4 A solution of bromine (50 mmol, 8.0 g) in pentane 50 ml was added dropwise to a solution of complex 1 (25 mmol, 14.8 g) in pentane (50 ml) at 278 8C and additionally stirred for 1 h.The solvent was removed under vacuum and the crude product condensed in a cold trap. Crystallisation of the resulting yellow oil from tert-butylamine yielded a colourless solid: M = 245.41 g mol21; yield 6.81 g (55%), m.p. 57.5 8C. NMR: 1H (400 MHz, C6D6) d 1.31 (s, 27 H, But); 13C (100 MHz, C6D6) d 30.33 [s, C(CH3)3], 56.99 [s, C(CH3)3]. [(thf)3Li3(Ï3-Br){(NBut)3S}] 5.A solution of bromine (3 mmol, 0.48 g) in thf (10 ml) was added dropwise to a solution of complex 1 (4 mmol, 2.36 g) in hexane (10 ml) at 0 8C and stirred for 1 h at room temperature. Crystallisation from the resulting solution at 220 8C yielded colourless crystals: M = 562.44 g mol21; yield 1.10 g (63%); m.p. 115 8C. NMR: 1H (300 MHz, C6D6) d 1.27 (s, 9 H, But), 1.66 (m, 4 H, thf), 3.60 (m, 4 H, thf); 13C (75 MHz, C6D6) d 25.95 (OCH2CH2, thf), 34.60 [C(CH3)3], 53.81 [C(CH3)3], 68.30 (OCH2, thf).[(thf)3Li3(Ï3-I){(NBut)3S}] 6. A solution of iodine (3 mmol, 0.76 g) in thf (10 ml) was added dropwise to a solution of complex 1 (4 mmol, 2.36 g) in hexane (10 ml ) at 0 8C and stirred for 1 h. The reaction mixture was stored at 220 8C and after 12 h colourless crystals were obtained: M = 609.44 g mol21; yield 1.33 g (73%); m.p. 117 8C. NMR: 1H (200 MHz, C6D6) d 1.29 (s, 9 H, But), 1.68 (m, 4 H, thf), 3.62 (m, 4 H, thf); 13C (100 MHz, C6D6) d 26.35 (OCH2CH2, thf), 34.58 [C(CH3)3], 53.95 [C(CH3)3], 68.22 (OCH2, thf).Crystal data for complexes 5–7 Crystal data for the three structures are presented in Table 2. Data for all structures were collected at low temperature using oil-coated shock-cooled crystals 17 on a Stoe-Siemens AED (6 and 7) or Stoe-Huber-Siemens-Eigenbau diffractometer fitted with a Siemens CCD detector (5) using graphite-monochromated Mo-Ka radiation (l = 0.710 73 Å). Semiempirical absorption correction was applied.18,19 The structures were solved by Patterson or direct methods using SHELXS 96.20 All structures were refined by full-matrix least-squares procedures on F2, using SHELXL 96.21 All non-hydrogen atoms were refined anisotropically, and a riding model was employed in the refinement of the hydrogen atom positions.The denoted R values are defined as follows: R1 = S||Fo| 2 |Fc||/S|Fo| and wR2 = [Sw(Fo 2 2 Fc 2)2/Sw(Fo 2)2]� �� ; w = 1/{s2(Fo 2) 1 ( g1P)2 1 g2P}; P = (Fo 2 1 2Fc 2)/3.Complex 5 crystallises in the orthorhombic space group Pnma. Space group symmetry (mirror plane) was suppressed for the refinement of the tert-butyl group (C20–C23). The coordinating thf molecule (O2, C35–C38) was refined to a split occupancy of 0.57 : 0.43, suppressing the symmetry. Bond length and similarity restraints were used in the refinement of both groups. Complex 6 is isostructural with 5. The disordered tertbutyl moiety (C20–C23) was refined to a split occupancy ofJ. Chem.Soc., Dalton Trans., 1998, Pages 193–197 197 0.79 : 0.21. The space group symmetry (mirror plane) was suppressed. The co-ordinating thf molecule (O2, C35–C38) was treated likewise. Refinement of a split occupancy for the thf molecule was attempted but did not give a better model. Bond length and similarity restraints were applied. The disordered thf molecules in 7 were refined to split occupancies of 0.5 :0.5 (O1, C13–C16 and O2, C17–C20) and 0.45 : 0.55 (O3, C21–C24).Bond length and similarity restraints were used in the refinement. Selected bond lengths and angles are presented in Table 1. CCDC reference number 186/809. See http://www.rsc.org/suppdata/dt/1998/193/ for crystallographic files in .cif format. Acknowledgements Funding was kindly provided by the Deutsche Forschungsgemeinschaft, the Fonds der Chemischen Industrie, and the Stiftung Volkswagenwerk. Support by Bruker axs-Analytical X-Ray Systems, Karlsruhe, is gratefully acknowledged.References 1 Houben-Weyl, Methoden der Organischen Chemie, E11, parts 1 and 2, supplementary volume of the 4th edn., Thieme Verlag, Stuttgart, 1985. 2 M. Goehring and G. Weis, Angew. Chem., 1956, 68, 678. 3 P. Hope and L. A. Wiles, J. Chem. Soc., 1965, 5386; O. J. Scherer and R. Schmitt, J. Organomet. Chem., 1969, 16, 11; O. J. Scherer and R. Wies, Z. Naturforsch., Teil B, 1970, 25, 1486; J. Kuyper, P. C. Keijzer and K. Vrieze, J.Organomet. Chem., 1976, 116, 1; J. Kuyper and K. Vrieze, J. Chem. Soc., Chem. Commun., 1976, 64; D. Hänssgen and W. Rölle, J. Organomet. Chem., 1973, 63, 269; F. Pauer and D. Stalke, J. Organomet. Chem., 1991, 418, 127; F. Pauer, J. Rocha and D. Stalke, J. Chem. Soc., Chem. Commun., 1991, 1477; F. T. Edelmann, F. Knösel, F. Pauer, D. Stalke and W. Bauer, J. Organomet. Chem., 1992, 438, 1; S. Freitag, W. Kolodziejski, F. Pauer and D. Stalke, J. Chem. Soc., Dalton Trans., 1993, 3479. 4 R. Fleischer, S. Freitag, F. Pauer and D. Stalke, Angew. Chem., 1996, 108, 208; Angew. Chem., Int. Ed. Engl., 1996, 35, 204. 5 A. Gieren and P. Narayanan, Acta Crystallogr., Sect. A, 1975, 31, 120; H. W. Roesky, W. Schmieder and W. S. Sheldrick, J. Chem. Soc., Chem. Commun., 1981, 1013; H. W. Roesky, W. Schmieder, W. Isenberg, W. S. Sheldrick and G. M. Sheldrick, Chem. Ber., 1982, 115, 2714. 6 O. Glemser and J. Wegener, Angew. Chem., 1970, 82, 324; Angew. Chem., Int. Ed.Engl., 1970, 9, 309. 7 R. Mews, P. G. Watson and E. Lork, Coord. Chem. Rev., 1997, 158, 233. 8 O. Glemser, S. Pohl, F. M. Tesky and R. Mews, Angew. Chem., 1977, 89, 829; Angew. Chem., Int. Ed. Engl., 1977, 16, 789. 9 W. Lidy, W. Sundermeyer and W. Verbeek, Z. Anorg. Allg. Chem., 1974, 406, 228. 10 F. M. Tesky and R. Mews, Chem. Ber., 1980, 113, 2183; 2434; F. M. Tesky, R. Mews and B. Krebs, Z. Naturforsch., Teil B, 1981, 36, 1465; Angew. Chem., 1978, 90, 722; Angew. Chem., Int. Ed. Engl., 1978, 17, 677; R. Höfer and O. Glemser, Z. Naturforsch., Teil B, 1975, 30, 460; M. Schmidt and W. Siebert, Comprehensive Inorganic Chemistry, 1978, vol. 2, p. 868. 11 N. N. Greenwood andrnshaw, Chemistry of the Elements, VCH, New York, 1988, p. 926. 12 (a) J. A. Hunter, B. King, W. E. Lindsell and M. A. Neish, J. Chem. Soc., Dalton Trans., 1980, 880; (b) G. Brands and A. Golloch, Z. Naturforsch., Teil B, 1982, 37, 1137. 13 D. Ilge and D. Stalke, submitted. 14 H. Ott, Phys. Z., 1923, 24, 209. 15 B. Nyberg and P. Kierkegaard, Acta Chem. Scand., 1968, 22, 581; A. F. Wells, Structural Inorganic Chemistry, Clarendon Press, Oxford, 1984, p. 584; Cambridge Structural Database, F. H. Allen and O. Kennard, Chem. Des. Automat. News, 1993, 8, 131. 16 R. Fleischer, A. Rothenberger and D. Stalke, Angew. Chem., 1997, 109, 1140; Angew. Chem., Int. Ed. Engl., 1997, 36, 1105. 17 H. Hope, Acta Crystallogr., Sect. B, 1988, 44, 22; T. Kottke and D. Stalke, J. Appl. Crystallogr., 1993, 26, 615; T. Kottke, R. J. Lagow and D. Stalke, J. Appl. Crystallogr., 1996, 29, 465. 18 A. C. T. North, D. C. Phillips and F. S. Mathews, Acta Crystallogr., Sect. A, 1968, 24, 351. 19 G. M. Sheldrick, program for absorption correction, University of Göttingen, 1996. 20 G. M. Sheldrick, Acta Crystallogr., Sect. A, 1990, 46, 467. 21 G. M. Sheldrick, program for crystal structure refinement, University of Göttingen, 1996. Received 1st October 1997; Paper 7/07085C

ISSN:1477-9226    

DOI:10.1039/a707085c

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, Pages 199–205 199 Unsymmetrically substituted pyrazolates: nickel(II) complexes of a novel dinucleating ligand providing both N- and S-rich co-ordination spheres ‡ Matthias Konrad, Franc Meyer,*, † Katja Heinze and Laszlo Zsolnai Anorganisch-Chemisches Institut der Universität Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany An unsymmetric pyrazolate ligand with different chelating side arms in the 3 and 5 positions of the heterocycle {3-[(EtSCH2CH2)2NCH2]-5-[(Et2NCH2CH2)2NCH2]C3N2H2 (HL1)} and its symmetrical analogue {3,5-[(EtSCH2CH2)2NCH2]2C3N2H2(HL2)} have been prepared.Upon reaction with NiCl2?6H2O they afforded dinuclear complexes [Ni2L1Cl3] 2 and [Ni2L2Cl3] 1 that contain both a bridging pyrazolate and a bridging chlorine atom. While all nickel(II) ions within the N2S2 compartments of the primary ligands are six-co-ordinate, one of the amino side arms of L1 in the former complex is non-co-ordinating, leaving the respective nickel centre in a squarepyramidal environment.This dangling arm is co-ordinated to the metal ion upon treatment of 2 with NaBPh4 due to substitution of the terminal chlorine atom to form [Ni2L1Cl2][BPh4] 3. All new complexes were characterised by means of X-ray crystallography; 2 and 3 represent rare examples of dinuclear complexes exhibiting various kinds of asymmetry. The electrochemical and magnetic properties of the complexes are reported.The current interest in bi- and multi-metallic transition-metal complexes first of all arises from the fact that many active centres of metalloenzymes contain several co-operating metal ions in close proximity.1 The individual metal centres often play specific and different roles in the functioning of the enzyme and consequently most of the oligonuclear metallobiosites have turned out to be of asymmetric character.2 However, whereas many examples of bimetallic co-ordination compounds derived from symmetric dinucleating ligands have been described,3 multidentate ligand systems with differentiated co-ordination spheres, which necessarily give asymmetric dinuclear complexes, have remained rare.4 Hence the design and synthesis of new unsymmetric dinucleating ligand matrices providing distinct donor sets for each metal centre is highly desirable in order to obtain model complexes for the different types of asymmetry possibly present in such dinuclear cores, i.e.donor atom, coordination number or geometric asymmetry of either homo- or hetero-dinuclear character.4c,5 Apart from the bioinorganic motivation, distinct reactivity patterns of unsymmetric dinuclear entities towards substrate molecules can be expected, e.g. resulting from the co-operative effects of both hard and soft metal centres located in close proximity.6 The vast majority of the unsymmetric dinucleating ligands hitherto reported is based on a bridging phenoxo- or alkoxogroup. 4,5 Although the ability of diazine heterocycles like pyrazolates to span two metal centres in a bridging fashion is well established,7 relatively few studies of dinuclear complexes of pyrazolate ligands providing additional chelating substituents have been performed.8–14 In particular, only one pyrazolate ligand with different substituents in the 3 and 5 positions of the heterocycle has been described, in which however the differentiation between the two co-ordination spheres is marginal as it consists of only one additional methyl group attached to a pyridyl side arm.12 In recent work we described the synthesis of dinuclear complexes derived from a series of pyrazolate-based ligands with pendant polyamino side arms13a and demonstrated the possibility selectively to tune the range of accessible metal–metal † E-Mail: franc@sun0.urz.uni-heidelberg.de ‡ Non-SI unit employed: mB = 9.27 × 10224 J T21.separations in these systems by variation of the side arm chain length.13b The present contribution deals with a new synthetic strategy to allow access to dinucleating pyrazolate-based ligands with chemically non-equivalent environments for the two metal centres.Emphasis is placed on a distinction of the two co-ordination compartments with regard to the hardness of the donor sites, i.e. one donor set is composed of only nitrogen donors with the other donor set comprised of mixed sulfur– nitrogen atoms, and on an asymmetry regarding the coordination number of the two metal ions.Dinuclear nickel(II) complexes are prepared and characterised structurally in order to probe the co-ordination potential of the new ligand system. Furthermore a related symmetric system is synthesized and studied for comparison. Results and Discussion The synthesis of the unsymmetric pyrazolate-based ligand HL1 carrying pendant side arms with different donor sets in the 3 and 5 positions of the heterocycle is accomplished as outlined in Scheme 1.Cycloaddition of ethyl diazoacetate and prop-2- ynyl alcohol yields the unsymmetrically substituted pyrazole derivative II.15 Conversion of its hydroxymethyl group into a Scheme 1 HN Cl HN SEt 2 2 2 NaSEt I N2 OEt O OH N N OEt O HO H II N N OEt O R1 2N H III N N NR2 2 R1 2N H HL1 1 SOCl2 2 I, NEt3 1 LiNR2 2 2 LiAlH4 HN SEt 2 HN NEt2 2 HNR1 2 = HNR2 2 =200 J. Chem. Soc., Dalton Trans., 1998, Pages 199–205 chloromethyl function by means of SOCl2 followed by treatment with the appropriate secondary amine I [prepared from bis(2-chloroethyl)amine as shown in Scheme 1] in the presence of triethylamine attaches the first donor side arm III.Subsequent reaction with the lithiated amine NR2 2H and reduction of the resulting amide using LiAlH4 affords the unsymmetric potential ligand HL1 which provides both an N4 and an N2S2 co-ordination compartment. It should be noted that beyond the preparation of HL1 the reaction sequence described here opens up a more general access to various unsymmetric pyrazolatebased ligand systems with variable chelating side arms.The corresponding symmetric (N2S2)2 dinucleating ligand HL2 was synthesized following a strategy described previously for the related (N4)2 analogue,9d,13a Scheme 2. Synthesis and structural characterisation of nickel(II) complexes In order to gain some basic knowledge about the general coordination mode of the N2S2 donor compartment of these novel pyrazolate ligands, we first studied a dinickel(II) complex of the symmetric species HL2.The green neutral complex [Ni2L2Cl3] 1 is produced when the ligand HL2 is first deprotonated by means of LiBu and subsequently treated with 2 equivalents of NiCl2?6H2O. Complex 1 shows good solubility in tetrahydrofuran (thf) or CH2Cl2 and proved to be stable in air over prolonged periods. Single crystals suitable for a crystallographic analysis were obtained by vapour diffusion of Et2O into a CH2Cl2 solution of the product.The molecular structure of 1 is depicted in Fig. 1 and selected distances and angles are given in Table 1. The structure reveals a dinuclear arrangement of two nickel ions spanned by both the pyrazolate of L2 and a bridging chlorine atom. Each nickel centre is found in an N2S2Cl2 environment, slightly distorted from octahedral due to the limited dimensions of the chelate rings of the primary ligand side arms [e.g.S(1)]Ni(1)]S(1A) 166.59(8), [S(2)]Ni(2)]S(2A) 167.69(7)8]. The pyrazolate heterocycle as well as the nickel ions and the donor atoms N(3), N(4), Cl(1), Cl(2) and Cl(3) lie within a mirror plane of the dinuclear molecule that has crystallographically imposed Cs symmetry. Scheme 2 N N OH HO H N N NR1 2 R1 2N H O O 1 SOCl2 2 I, NEt3 3 LiAlH4 HL2: NR1 2 = N SEt 2 Fig. 1 View of the molecular structure of complex 1. For clarity all hydrogen atoms have been omitted Similar to the co-ordination behaviour of mononucleating tripodal tetradentate NS3 ligands,16 each co-ordination compartment of L2 obviously allows for six-co-ordination of the metal centres, as long as the sulfur atoms bear small substituents like the present ethyl groups.In contrast, complexes containing a tripodal tetradentate NN3 donor set are known to remain five-co-ordinate in the case of tertiary pendant nitrogen atoms. This is also true for the dinuclear nickel complexes of the unsymmetrical ligand HL1 studied here.Treatment of the deprotonated potential ligand with 2 equivalents of NiCl2?6H2O affords the green neutral complex [Ni2L1Cl3] 2, which crystallises upon vapour diffusion of Et2O into a thf solution of the product. A view of the molecular structure of 2 is depicted in Fig. 2; selected distances and angles are listed in Table 2. As expected, 2 consists of a dinickel framework with both a bridging pyrazolate and a bridging chlorine atom.While Ni(2) is located in a distorted octahedral co-ordination environment that is essentially identical to those observed in 1, Ni(1) is only five-co-ordinate, leaving one dangling side arm of the primary ligand non-co-ordinating. The co-ordination geometry around Ni(1) appears to be distorted square planar with N(5) in the Fig. 2 View of the molecular structure of complex 2. Details as in Fig. 1 Table 1 Selected distances (Å) and angles (8) for complex 1 Ni(1)]N(1) Ni(1)]N(4) Ni(1)]Cl(2) Ni(1)]Cl(1) Ni(1)]S(1) Ni(1)]S(1A) Ni(2)]N(2) N(1)]Ni(1)]N(4) N(1)]Ni(1)]Cl(2) N(4)]Ni(1)]Cl(2) N(1)]Ni(1)]Cl(1) N(4)]Ni(1)]Cl(1) Cl(2)]Ni(1)]Cl(1) N(1)]Ni(1)]S(1) N(4)]Ni(1)]S(1) Cl(2)]Ni(1)]S(1) Cl(1)]Ni(1)]S(1) N(1)]Ni(1)]S(1A) N(4)]Ni(1)]S(1A) Cl(2)]Ni(1)]S(1A) Cl(1)]Ni(1)]S(1A) S(1)]Ni(1)]S(1A) N(2)]Ni(2)]N(3) 1.975(6) 2.195(5) 2.367(2) 2.430(2) 2.475(2) 2.475(2) 1.991(5) 78.1(2) 174.7(2) 96.5(2) 89.3(2) 167.4(2) 96.07(7) 86.06(4) 83.89(4) 93.42(4) 95.36(4) 86.06(4) 83.89(4) 93.42(4) 95.36(4) 166.59(8) 77.4(2) Ni(2)]N(3) Ni(2)]Cl(3) Ni(2)]Cl(1) Ni(2)]S(2) Ni(2)]S(2A) Ni(1) ? ? ? Ni(2) N(2)]Ni(2)]Cl(3) N(3)]Ni(2)]Cl(3) N(2)]Ni(2)]Cl(1) N(3)]Ni(2)]Cl(1) Cl(3)]Ni(2)]Cl(1) N(2)]Ni(2)]S(2) N(3)]Ni(2)]S(2) Cl(3)]Ni(2)]S(2) Cl(1)]Ni(2)]S(2) N(2)]Ni(2)]S(2A) N(3)]Ni(2)]S(2A) Cl(3)]Ni(2)]S(2A) Cl(1)]Ni(2)]S(2A) S(2)]Ni(2)]S(2A) Ni(1)]Cl(1)]Ni(2) 2.214(6) 2.350(2) 2.422(2) 2.4886(14) 2.489(2) 3.823 174.4(2) 96.9(2) 89.3(2) 166.7(2) 96.33(7) 87.61(4) 83.95(3) 91.82(4) 95.64(3) 87.61(4) 83.95(3) 91.82(4) 95.64(3) 167.69(7) 103.99(7)J.Chem. Soc., Dalton Trans., 1998, Pages 199–205 201 apical position. Despite the inherent donor atom and coordination number asymmetry present in 2, the Ni ? ? ? Ni distances observed for 2 and the symmetric complex 1 are virtually identical [d(Ni ? ? ? Ni) = 3.823 Å]. However, both the Ni]Npyrazolate and Ni]Clbridge bond lengths are slightly smaller for the five-co-ordinate metal ion {d[Ni(1)]N(1)] = 1.952(3); d[Ni(1)]Cl(3)] = 2.392(1) Å} compared to those for the sixco- ordinate metal ions {2: d[Ni(2)]N(2)] = 1.981(3); d[Ni(2)] Cl(3)] = 2.421(1) Å; 1: d[Ni(1)]N(1)] = 1.975(6), d[Ni(2)]N(2)] = 1.991(5), d[Ni(1)]Cl(1)] = 2.430(2), d[Ni(2)]Cl(1)] = 2.422(2) Å}.Reaction of complex 2 with 1 equivalent of NaBPh4 induces co-ordination of the formerly dangling side arm to the Ni(1) centre due to substitution of the respective terminal chlorine atom. Single crystals of the resulting product [Ni2L1Cl2][BPh4] 3 formed upon vapour diffusion of Et2O into a thf solution of the complex.The molecular structure of the cation of 3 is shown in Fig. 3, selected distances and bond angles in Table 3. Atom Ni(1) is now found in a distorted trigonal-bipyramidal environment with the branching nitrogen atom N(4) and the bridging Cl(1) in axial positions. In accordance with the structural findings for a series of related symmetric dicobalt(II) complexes of pyrazolate-based polyamino ligands,13a,b coordination of all side arms of the tren-type NN3 co-ordination subunit of L1 pulls the two metal centres back and apart, thus causing a lengthening of the Ni ? ? ? Ni separation when going Fig. 3 Molecular structure of the cation of complex 3. Details as in Fig. 1 Table 2 Selected distances (Å) and angles (8) for complex 2 Ni(1)]N(1) Ni(1)]N(5) Ni(1)]N(4) Ni(1)]Cl(1) Ni(1)]Cl(3) Ni(2)]N(2) N(1)]Ni(1)]N(5) N(1)]Ni(1)]N(4) N(5)]Ni(1)]N(4) N(1)]Ni(1)]Cl(1) N(5)]Ni(1)]Cl(1) N(4)]Ni(1)]Cl(1) N(1)]Ni(1)]Cl(3) N(5)]Ni(1)]Cl(3) N(4)]Ni(1)]Cl(3) Cl(1)]Ni(1)]Cl(3) N(2)]Ni(2)]N(3) N(2)]Ni(2)]Cl(2) N(3)]Ni(2)]Cl(2) 1.952(3) 2.089(4) 2.234(4) 2.2828(12) 2.3921(12) 1.981(3) 100.71(14) 78.07(14) 86.67(14) 152.32(11) 105.48(10) 94.51(10) 88.95(10) 102.63(10) 165.32(10) 93.89(4) 78.84(13) 173.14(10) 96.93(10) Ni(2)]N(3) Ni(2)]Cl(2) Ni(2)]Cl(3) Ni(2)]S(2) Ni(2)]S(1) Ni(1) ? ? ? Ni(2) N(2)]Ni(2)]Cl(3) N(3)]Ni(2)]Cl(3) Cl(2)]Ni(2)]Cl(3) N(2)]Ni(2)]S(2) N(3)]Ni(2)]S(2) Cl(2)]Ni(2)]S(2) Cl(3)]Ni(2)]S(2) N(2)]Ni(2)]S(1) N(3)]Ni(2)]S(1) Cl(2)]Ni(2)]S(1) Cl(3)]Ni(2)]S(1) S(2)]Ni(2)]S(1) Ni(1)]Cl(3)]Ni(2) 2.166(3) 2.3518(12) 2.4210(11) 2.4462(13) 2.5054(13) 3.823 87.78(10) 166.59(10) 96.33(4) 88.43(10) 83.70(9) 96.51(5) 96.77(4) 90.34(10) 85.23(9) 83.90(4) 94.21(4) 168.89(4) 105.19(4) from 2 to 3 [d(Ni ? ? ? Ni) = 3.903 Å].Interestingly, this leads to a significantly longer Ni(2)]Clbridge bond {d[Ni(2)]Cl(3)] = 2.421(1) in 2 vs.d[Ni(2)]Cl(1)] = 2.560(1) Å in 3}, while the Ni(1)]Clbridge distance remains virtually unchanged {d[Ni(1)] Cl(3)] = 2.392(1) in 2 vs. d[Ni(1)]Cl(1)] = 2.397(1) in 3}. Complexes 2 and 3 thus represent dinuclear compounds that exhibit various kinds of asymmetry, examples of which have hitherto remained rare. Spectroscopy and electrochemistry The UV absorption spectrum of complex 1 displays three ligand-field transitions at 8730(n1), 15 550(n2) and 24 940(n3) cm21 assigned to spin-allowed transitions from 3A2g to 3T2g, 3T1g(F) and 3T1g(P), respectively, in accord with a d8 ion in a near-octahedral co-ordination sphere.17 The value Doct ª 8730 cm21 can be deduced from the n1 band, and a calculated Racah parameter B ª 880 cm21 results from consideration of an octahedral strong-field coupling scheme.Taking 15B = 15 615 cm21 for the gaseous ion Ni21 (3P),18 this leads to a nephelauxetic ratio b of 0.845. In the case of the unsymmetrical complexes 2 and 3 similar UV absorptions characteristic for a d8 ion with octahedral ligation 17 are observed at 9090, 14 290 and 24 630 cm21 2 and at 8840, 14 750 and 24 690 cm21 3.However, an additional band at 23 470 cm21 2 and a shoulder at ª23 800 cm21 3 appear, which are attributed to the presence of the second type of nickel(II) ions, i.e. the five-co-ordinate metal centres.19 All dinuclear complexes have been studied by cyclic voltammetry (CV) in the potential range 0.0 to 11.50 V vs.the saturated calomel electrode (SCE) in CH2Cl2 (Fig. 4). Complex 1 shows a reversible oxidation wave at E2� 1 = 10.87 V followed by a second oxidation with Ep ox = 11.26 V, these processes presumably corresponding to the sequential formation of NiIIINiII and NiIIINiIII species, respectively. While the second oxidation wave at the more positive potential appears to be irreversible at low scan rates (50 mV s21), it changes its shape with increasing scan rates to become quasi-reversible and yield an E2� 1 value of 11.19 V.Attempts to oxidise 1 on a preparative scale are currently underway. The cyclic voltammogram of 2 displays an oxidation process at Ep ox = 11.13 V (200 mV s21) with a shoulder at around 10.90 V, the main wave becoming quasireversible at higher scan rates to give E2� 1 = 11.06 V. In contrast, 3 shows an oxidation wave with Ep ox = 10.93 V (200 mV s21) that remains irreversible over the entire range of scan rates studied (50–1000 mV s21). Obviously the presence of the fiveco- ordinate nickel ions in the unsymmetric complexes 2 and 3 prevents the reversible generation (on the time-scale of the CV experiment) of a mixed-valence NiIIINiII species.Table 3 Selected distances (Å) and angles (8) for complex 3 Ni(1)]N(1) Ni(1)]N(5) Ni(1)]N(6) Ni(1)]N(4) Ni(1)]Cl(1) Ni(2)]N(2) N(1)]Ni(1)]N(5) N(1)]Ni(1)]N(6) N(5)]Ni(1)]N(6) N(1)]Ni(1)]N(4) N(5)]Ni(1)]N(4) N(6)]Ni(1)]N(4) N(1)]Ni(1)]Cl(1) N(5)]Ni(1)]Cl(1) N(6)]Ni(1)]Cl(1) N(4)]Ni(1)]Cl(1) N(2)]Ni(2)]N(3) N(2)]Ni(2)]Cl(2) N(3)]Ni(2)]Cl(2) 1.936(4) 2.125(4) 2.145(4) 2.156(4) 2.3972(12) 1.986(4) 102.2(2) 102.4(2) 150.6(2) 80.6(2) 84.08(14) 84.4(2) 89.67(11) 98.05(11) 97.87(11) 170.25(11) 78.8(2) 175.36(11) 96.61(12) Ni(2)]N(3) Ni(2)]Cl(2) Ni(2)]S(2) Ni(2)]S(1) Ni(2)]Cl(1) Ni(1) ? ? ? Ni(2) N(2)]Ni(2)]S()]Ni(2)]S(2) Cl(2)]Ni(2)]S(2) N(2)]Ni(2)]S(1) N(3)]Ni(2)]S(1) Cl(2)]Ni(2)]S(1) S(2)]Ni(2)]S(1) N(2)]Ni(2)]Cl(1) N(3)]Ni(2)]Cl(1) Cl(2)]Ni(2)]Cl(1) S(2)]Ni(2)]Cl(1) S(1)]Ni(2)]Cl(1) Ni(1)]Cl(1)]Ni(2) 2.185(4) 2.3242(13) 2.4756(14) 2.5029(14) 2.5600(12) 3.903 88.85(12) 84.20(14) 91.13(5) 88.75(12) 84.49(13) 90.37(5) 168.68(5) 85.61(11) 164.37(12) 99.01(5) 96.12(5) 94.72(4) 103.82(4)202 J.Chem. Soc., Dalton Trans., 1998, Pages 199–205 Magnetic properties of the complexes The magnetic properties of all new complexes have been studied in the solid state over the temperature range 5–290 K.The data obtained for the molar susceptibility and the effective magnetic moment are plotted in Fig. 5. The magnetic moment per nickel ion gradually decreases from 3.10 mB at 270 K (1), 3.12 mB at 293 K (2) and 3.25 mB at 275 K (3) to 0.43 mB at 4.7 K (1), 0.44 mB at 4.7 K (2) and 0.89 mB at 4.6 K (3), respectively, while the susceptibility curves exhibit broad maxima at around 35 (1), 40 (2) and 17 K (3), this behaviour being indicative of antiferromagnetic coupling between two nickel(II) centres in all cases.Fitting the experimental data by the theoretical expression for the isotropic spin Hamiltonian H = 22J?S1?S2 (with S1 = S2 = 1) including a molar fraction p of uncoupled paramagnetic impurity [equation (1)] 20 and neglecting the asymc = cdim(1 2 p) 1 2cmono p 1 2Na (1) metric character of the complexes yields the values listed in Table 4.§ In principle, powder measurements are not ideally suited for a thorough analysis of S = 1 dinuclear systems, however the intradimer exchange term J often proves to be the dominant term in the spin Hamiltonian 22,23 and accordingly Fig. 4 Cyclic voltammograms of complex 1 (top), 2 (middle) and 3 (bottom) in CH2Cl2 containing 0.1 M NBun 4PF6 at scan speed 200 mV s21 § Na refers to the temperature-independent paramagnetism [100 × 1026 cm3 mol21 per nickel(II) ion 21b]; all other parameters have their usual meaning. cdim = (Ng2mB 2/kT)[2exp(2J/kT) 1 10exp(6J/kT)]/[1 1 3exp- (2J/kT) 1 5exp(6J/kT)], cmono = 2Ng2mB 2/3kT.the neglect of both a zero-field splitting parameter D and interdimer interactions z9J9 results in a good-quality fit in the present case (Fig. 5). The observed exchange interaction turns out to be only slightly smaller for 1 (J = 212.0 cm21) compared to 2 (J = 213.1 cm21), but significantly smaller for 3 (J = 28.1 cm21). Magnetostructural relationships for dinuclear nickel(II) systems are not yet as elaborate as the detailed correlations noted in copper(II) chemistry.21 Furthermore, the fact that the complexes studied here differ by various structural parameters precludes the definitive deduction of any correlation between J and the structural data.However, it is interesting that a dependence of the antiferromagnetic exchange interaction on the metal–metal separation is perceptible. Thus the lengthening of the nickel–nickel distance in 3 compared to those in 1 and 2 is accompanied by a drastic decrease in the value of 2J.The difference in J for 1 and 2 might be related to a more efficient orbital overlap for the five-co-ordinate metal ion caused by the Fig. 5 Temperature dependence of the molar magnetic susceptibility (solid diamonds) and magnetic moment (solid squares) per nickel atom for complexes 1 (top), 2 (middle) and 3 (bottom). The line represents the calculated curve Table 4 Magnetic data for the complexes Compound 1 [Ni2L2Cl3] 2 [Ni2L1Cl3] 3 [Ni2L1Cl2][BPh4] J/cm21 212.0 213.1 28.1 g 2.30 2.27 2.35 p 0.04 0.03 0.07J. Chem.Soc., Dalton Trans., 1998, 199–205 203 slightly shorter Ni]Npyrazolate and Ni]Clbridge bond lengths (see above). A substantial increase of the antiferromagnetic coupling that has been reported to occur when a six-co-ordinate species transforms to a five-co-ordinate square-pyramidal species in a series of doubly phenoxide-bridged dinickel(II) complexes is not observed in the present case.23 Conclusion A synthetic strategy opening up access to unsymmetric dinucleating ligands containing a bridging pyrazolate moiety has been developed.The ligand HL1 providing non-equivalent NN3 and NNS2 co-ordination compartments affords dinuclear nickel(II) complexes 2 and 3, which exhibit both donor atom and coordination number asymmetry. The metal–metal distances are in the range 3.82–3.91 Å, thus stimulating further investigations with regard to achieving co-operative effects within complexes of this type.While the NNS2 donor set allows for six-coordination of the respective metal centre (including both terminal and bridging chloride ligands), the nickel(II) ion ligated by the NN3 subunit is restricted to five-co-ordination. The electrochemical oxidations of 2 and 3 are irreversible processes. In contrast, the symmetric complex 1 of the independently prepared (NNS2)2 ligand HL2, which contains two six-co-ordinate nickel(II) ions, displays a reversible first oxidation wave, presumably generating the mixed-valent NiIINiIII species.Studies aimed at oxidising 1 on a preparative scale are in progress. While the magnetic properties of 1 and 2 differ only slightly, 3 shows a significantly decreased value for the antiferromagnetic exchange interaction, which is rationalised on the basis of its larger metal–metal separation. These results emphasise that distinct properties can be expected from subtle changes in ligation and from the introduction of asymmetry at dinuclear metal centres.Furthermore HL1 as well as related unsymmetric dinucleating systems should prove promising candidates for a controlled synthesis of heterodinuclear complexes. Work in this regard is presently underway. Experimental All manipulations were carried out under an atmosphere of dry nitrogen by employing standard Schlenk techniques. Solvents were dried according to established procedures. The pyrazole derivative II was synthesized according to the reported method.15 Microanalyses: Mikroanalytische Laboratorien des Organisch-Chemischen Instituts der Universität Heidelberg.IR spectra: Bruker IFS 66 FTIR. Proton and 13C-{1H} NMR spectra: Bruker AC 200 at 200.13 and 50.32 MHz, respectively; solvent signal as chemical shift reference (CDCl3, dH 7.27, dC 77.0). FAB and EI mass spectra: Finnigan MAT 8230. UV/VIS/ NIR spectra: Perkin-Elmer Lambda 19. Cyclic voltammetry: PAR equipment (potentiostat/galvanostat 273), on 0.1 M NBu4PF6–CH2Cl2.Potentials in V on glassy carbon electrode, referenced to the SCE at ambient temperature. Magnetic measurements: Bruker B-E 15 C8 Magnet, B-H 15 field controller, ER4111VT variable-temperature unit, Sartorius M 25 D-S micro balance. Preparations Bis[2-(ethylsulfanyl)ethyl]amine I. A solution of bis(2- chloroethyl)amine hydrochloride (8.8 g, 50.0 mmol) in ethanol (100 cm3) was added to a solution of NaOH (6.0 g, 150.0 mmol) and ethanethiol (9.3 g, 150.0 mmol) in ethanol (150 cm3) at 0 8C.The mixture was stirred for 2 h, filtered and the filtrate evaporated to dryness. The residue was taken up in Et2O and filtered again. After evaporation of the solvent in vacuum, the product I (8.7 g, 90%) remained as a colourless semisolid (Found: C, 49.58; H, 9.79; N, 7.14. C8H19NS2 requires C, 49.69; H, 9.90; N, 7.24%); dH(CDCl3) 1.20 [6 H, t, J(HH) 7.4, CH3], 2.49 [4 H, q, J(HH) 7.4 Hz, CH2], and 2.60–2.80 (8 H, m, CH2); dC(CDCl3) 15.2 (CH3), 26.1 (CH2) 32.1 (CH2) and 48.6 (CH2); m/z 193 (M1, 35), 118 (M1 2 CH2SEt, 54) and 89 (CH2CH2- SEt1, 100%).Ethyl 5-{N,N-bis[2-(ethylsulfanyl)ethyl]aminomethyl}pyrazole- 3-carboxylate III. A solution of the pyrazole derivative II 15 (8.5 g, 50.0 mmol) in thionyl chloride (150 cm3) was stirred for 3 h at 0 8C. After evaporation of the solvent in vacuum raw ethyl 5-chloromethylpyrazole-3-carboxylate hydrochloride (10.7 g, 95%) remained as a white solid; dH[(CD3)2SO] 1.28 [3 H, t, J(HH) 7.1, CH3], 4.27 [2 H, q, J(HH) 7.1 Hz, CH2], 4.76 (2 H, s, CH2) and 6.82 (1 H, s, CH); dC(Me2SO) 15.0 (CH3), 37.7 (CH2), 61.4 (CH2Cl), 109.0 (pz C4), 139.4, 145.9 (pz C3/5) and 161.1 (C]] O); m/z 188 (M1 2 Cl, 37), 153 (M 2 2 Cl, 100) and 107 (M 2 2 Cl 2 OEt, 28%).This compound (2.6 g, 10.0 mmol) was dissolved in thf (100 cm3) and treated with a solution of I (1.9 g, 10.0 mmol) and triethylamine (5 cm3) in thf (30 cm3). The mixture was stirred for 2 h at room temperature.The triethylamine hydrochloride was then filtered off and the filtrate evaporated to dryness. The residue was taken up in Et2O and filtered again. Evaporation of the solvent in vacuum afforded III (3.1 g, 89%) as a yellow oil (Found: C, 51.49; H, 7.76; N, 12.36. C15H27N3O2S2 requires C, 52.14; H, 7.88; N, 12.16%); n& max/cm21 (film) 3136w (br), 2968–2927s, 1722vs, 1456s and 1227s; dH(CDCl3) 1.26 [6 H, t, J(HH) 7.4, CH3], 1.42 [3 H, t, J(HH) 7.2, CH3], 2.54 [4 H, q, J(HH) 7.4, CH2], 2.67– 2.85 (8 H, m, CH2), 3.81 (2 H, s, CH2), 4.42 [2 H, q, J(HH) 7.2 Hz CH2] and 6.70 (s, 1 H, CH); dC(CDCl3) 14.7 (CH3), 15.1 (CH3), 26.6 (SCH2), 30.1 (SCH2), 49.9 (NCH2), 54.1 (NCH2), 61.4 (OCH2), 107.1 (pz C4), 142.8, 144.8 (pz C3/5) and 162.4 (C]] O); m/z 345 (M1, 1), 270 (M1 2 CH2SEt, 75) and 89 (CH2CH2SEt1, 100%). 3-{N,N-Bis[2-(diethylamino)ethyl]aminomethyl}-5-{N,N-bis- [2-(ethylsulfanyl)ethyl]aminomethyl}pyrazole (HL1). A solution of LiBu (5.6 cm3, 2.5 M) in hexane was added to a solution of N,N,N9,N9-tetraethyldiethylenetriamine (3.0 g, 13.9 mmol) in thf (50 cm3) at 270 8C.This mixture was slowly added to a solution of compound III (2.4 g, 6.9 mmol) in thf (100 cm3) at 270 8C. After warming to room temperature, the solution was left stirring overnight, then quenched with a saturated aqueous NH4Cl solution and extracted several times with Et2O. The combined organic phases were dried over MgSO4 and filtered. After evaporation of the solvent in vacuum, 3-[N,N-bis[2- (diethylamino)ethyl]carbamoyl-5-{N,N-bis[2-(ethylsulfanyl)- ethyl]aminoethyl}pyrazole (3.0, 84%) remained as a yellow oil; dH(CDCl3) 1.12 [12 H, t, J(HH) 7.1, CH3], 1.27 [6 H, t, J(HH) 7.4 Hz, CH3], 2.50–2.77 (24 H, m, CH2), 3.51 (2 H, br t, CONCH2), 3.75 (2 H, br s, CONCH2), 3.80 (2 H, s, CH2) and 6.68 (1 H, s, CH); dC(CDCl3) 11.0 (CH3), 14.6 (CH3), 25.8 (CH2), 29.1 (CH2), 47.1 (CH2), 49.7 (CH2), 51.2 (CH2), 53.1 (CH2), 53.6 (CH2), 101.9 (pz C4), 143.4 and 148.5 (pz C3/5), C]] O not observed.A solution of this compound (3.0 g, 5.8 mmol) in thf (50 cm3) was added dropwise to a suspension of LiAlH4 (0.22 g, 5.8 mmol) in thf (100 cm3) at room temperature. The mixture was left stirring overnight, then heated to reflux for 30 min, cooled to 0 8C and finally hydrolysed by the dropwise addition of water (2 cm3). The precipitate was filtered off and washed several times with thf. The combined organic phases were dried over MgSO4, filtered and evaporated to dryness to yield HL1 (1.8 g, 62%) as a yellow oil (Found: C, 59.43; H, 10.29; N, 15.81.C25H52N6S2 requires C, 59.95; H, 10.47; N, 16.78%); n& max/cm21 (film) 2966–2811vs, 1453s, 1374s, 1294w, 1102s, 1069s and 801w; dH(CDCl3) 1.08 [12 H, t, J(HH) 7.1, CH3], 1.27 [6 H, t, J(HH) 7.4 Hz, CH3], 2.50–2.76 (28 H, m, CH2), 3.75 (2 H, s, CH2), 3.78 (2 H, s, CH2) and 5.99 (1 H, s, CH); dC(CDCl3) 11.3 (CH3), 15.1 (CH3), 25.6 (SCH2), 29.2 (SCH2), 47.0–53.7 (NCH2), 103.2 (pz C4) and 142.8, 149.5 (pz C3/5); m/z 501 (M1 1 1, 100) and 414 (M1 2 CH2CH2SEt, 53%).204 J.Chem. Soc., Dalton Trans., 1998, Pages 199–205 Table 5 Crystal data and refinement details for complexes 1–3 Formula Mr Crystal size/mm Crystal system Space group a/Å b/Å c/Å a/8 b/8 g/8 U/Å3 Dc/g cm23 ZF (000) m (Mo-Ka) mm21 Scan mode hkl Ranges 2q Range/8 Measured reflections Observed reflections [I > 2s(I)] Refined parameters Residual electron density e Å23 Rl wR2 Goodness of fit 1 C21H41Cl3N4Ni2S4?CH2Cl2 786.51 0.3 × 0.3 × 0.3 Orthorhombic Pnma 15.570(3) 12.286(3) 17.346(2) 3318.2(11) 1.574 4 1632 1.810 w 217 to 19, 28 to 15, 215 to 21 3.5–52 4306 3429 222 0.747, 21.313 0.052 0.177 1.771 2 C25H51Cl3N6Ni2S2 723.61 0.20 × 0.30 × 0.30 Monoclinic C2/c 42.712(9) 10.960(2) 14.176(2) 89.46(1) 6635.8 1.449 8 3056 1.528 w 26 to 51, ±13, ±17 3.8–51 6271 6185 357 0.536, 20.370 0.046 0.096 1.028 3 C49H52Cl2N6Ni2S2?0.5C4H10O?0.3C4H8O 1058.60 0.04 × 0.3 × 0.3 Triclinic P1� 14.884(2) 15.205(2) 15.675(2) 70.82(1) 65.93(1) 62.85(1) 2837.5(6) 1.239 2 1119 0.871 w 0 to 18, 16 to 18, 217 to 19 3.8–52 11 574 11 121 654 0.888, 20.403 0.054 0.177 1.065 3,5-Bis{N,N-bis[2-(ethylsulfanyl)ethyl]aminoethyl}pyrazole (HL2).Pyrazole-3,5-dicarboxylic acid monohydrate (1.7 g, 10.0 mmol) was converted into 3,5-bis(chloroformyl)pyrazole by the usual reaction with thionyl chloride (100 cm3). This was taken up in thf (100 cm3) and treated dropwise with a solution of compound I (3.9 g, 20.0 mmol) and triethylamine (5 cm3) in thf (50 cm3).After 2 h the triethylamine hydrochloride was filtered off and the filtrate evaporated to dryness. The residue was taken up in Et2O and filtered again. After evaporation of the solvent in vacuum, 3,5-bis{N,N-bis[2-(ethylsulfanyl)ethyl]carbamoyl}- pyrazole (4.7 g, 93%) remained as a yellow oil; dH(CDCl3) 1.25 (12 H, m, CH3), 2.59 [8 H, q, J(HH) 7.4, SCH2], 2.83 [8 H, t, J(HH) 7.3 Hz, SCH2], 3.71 (4 H, br s, CONCH2), 3.95 (4 H, br s, CONCH2) and 7.07 (1 H, s, CH); dC(CDCl3) 14.6 (CH3), 25.8 (SCH2), 28.6 (CH2), 30.2 (CH2), 47.7 (CH2), 49.3 (CH2), 109.2 (pz C4), 141.1 (pz C3/5) and 161.2 (C]] O); m/z 507 (M1 1 1, 20), 445 (M1 2 SEt, 23) and 89 (CH2CH2SEt, 100%).A solution of this compound (4.7 g, 9.3 mmol) in thf (50 cm3) was added to a suspension of LiAlH4 (0.7 g, 18.6 mmol) in thf (150 cm3). The mixture was left stirring overnight, heated to reflux for 30 min, then cooled to 0 8C and finally hydrolysed by dropwise addition of water (4 cm3).The precipitate was filtered off and washed several times with thf. The combined organic phases were dried over MgSO4, filtered and evaporated to dryness to yield HL2 (3.6 g, 80%) as a yellow oil (Found: C, 52.26; H, 9.03; N, 11.31. C21H42N4S4 requires C, 52.67; H, 8.84; N, 11.70%); n& max/cm21 (film) 3191s, 2945–2823vs, 1466vs, 1369s, 1263s, 1105s, 993w and 783w; dH(CDCl3) 1.24 [12 H, t, J(HH) 7.4, CH3], 2.30 [8 H, q, J(HH) 7.4 Hz, SCH2], 2.63–2.85 (16 H, m, CH2), 3.69 (4 H, s, CH2) and 6.03 (1 H, s, CH); dC(CDCl3) 15.3 (CH3), 26.6 (SCH2), 30.1 (SCH2), 54.2 (NCH2) and 103.7 (pz C4), pz C3/5 not observed; m/z 479 (M1 1 1, 6), 403 (M1 2 CH2SEt, 22) and 89 (CH2CH2SEt1, 100%).[Ni2L2Cl3] 1. A solution of LiBu (0.4 cm3, 2.5 M) in hexane and a solution of [Ni(H2O)6]Cl2 (0.48 g, 2.0 mmol) in ethanol (20 cm3) were added stepwise to a solution of HL2 (0.48 g, 1.0 mmol) in thf (50 cm3).The green reaction mixture was evaporated to dryness and the resulting green powder (0.67 g, 85%) washed several times with small portions of ethanol. Vapour diffusion of Et2O into a solution of the product in CH2Cl2 gave blue-green crystals of [Ni2L2Cl3] 1 (0.33 g, 47%) (Found: C, 35.55; H, 5.95; N, 7.94. C21H41Cl3N4Ni2S4 requires C, 35.95; H, 5.89; N, 7.99%); n& max/cm21 (KBr) 2960–2841vs, 1473s, 1457s, 1416s, 1266w, 1100s, 775w and 756w; m/z 664 (M1 2 Cl, 100) and 600 (M1 2 Cl 2 EtCl, 18%); lmax/nm (e/dm3 mol21 cm21) (CH2Cl2) 401 (131), 643 (27) and 1145 (49). [Ni2L1Cl3] 2.Starting from HL1 (0.50 g, 1.0 mmol) the preparation was carried out analogously to that for 1 to yield the raw product (0.66 g, 91%). Vapour diffusion of Et2O into a solution of the product in thf gave green crystals of [Ni2L1Cl3] 2 (0.25 g, 35%) (Found: C, 40.23; H, 7.04; N, 11.17. C25H51Cl3N6Ni2S2 requires C, 41.50; H, 7.10; N, 11.61%); n& max/cm21 (KBr) 2965–2844vs, 1471s, 1463s, 1381w, 1277w, 1098s, 1055s, 777w and 754w; m/z 687 (M 2 Cl, 100) and 623 (M 2 Cl 2 EtCl, 12%); lmax/nm (e/dm3 mol21 cm21) (CH2Cl2) 406 (70), 426 (72), 700 (23) and 1100 (37).[Ni2L1Cl2][BPh4] 3. A solution of NaBPh4 (0.34 g, 1.0 mmol) in ethanol (25 cm3) was added to a solution of complex 2 (0.72 g, 1.0 mmol) in thf (50 cm3) and stirred for 3 h at room temperature. After removal of all volatile material under vacuum the residue was taken up in thf and filtered.Evaporation of the solvent afforded the raw product as a green powder (0.90 g, 89%). Vapour diffusion of Et2O into a solution of the productn thf gave green crystals of [Ni2L1Cl2][BPh4] 3 (0.52 g, 52%) (Found: C, 58.45; H, 7.19; N, 8.35. C49H71BCl2N6Ni2S2 requires C, 58.42; H, 7.10; N, 8.34%); n& max/cm21 (KBr) 3053–2928vs, 1578w, 1478s, 1456s, 1315w, 1266w, 1103s, 735vs, 705vs and 611s; m/z 686 (L1Ni2Cl2, 100) and 651 (L1Ni2Cl, 12%); lmax/nm (e/dm3 mol21 cm21) (CH2Cl2) 405 (120), 678 (45) and 1130 (55).Crystallography The measurements were carried out at 200 K on a Siemens P4 (Nicolet Syntex) R3m/v four-circle diffractometer with graphite-monochromated Mo-Ka radiation (l 0.710 73 Å). All calculations were performed with a micro-vax computer using the SHELXTL PLUS software package.24 Structures were solved by direct methods with SHELXS 86 and refined with the SHELXL 93 programs.24 An absorption correction (y scan, Dy = 108) was applied to all data.Atomic coordinates and anisotropic thermal parameters of the non-hydrogen atomsJ. Chem. Soc., Dalton Trans., 1998, Pages 199–205 205 were refined by full-matrix least-squares calculation. The hydrogen atoms were placed at calculated positions and allowed to ride on the atoms to which they were attached. Table 5 compiles the data for the structure determinations. CCDC reference number 186/782. See http://www.rsc.org/suppdata/dt/1998/199/ for crystallographic files in .cif format.Acknowledgements We are grateful to Professor Dr. G. Huttner for his generous and continuous support of our work as well as to the Deutsche Forschungsgemeinschaft (Habilitandenstipendium for F. M.) and the Fonds der Chemischen Industrie. References 1 K. D. Karlin, Science, 1993, 261, 701; R. H. Holm, Pure Appl. Chem., 1995, 67, 217; N. Sträter, W. N. Lipscomb, T. Klabunde and B. Krebs, Angew. Chem., 1996, 108, 2158; Angew.Chem., Int. Ed. Engl., 1996, 35, 2024. 2 W. Kaim and B. Schwederski, Bioanorganische Chemie, Teubner, Stuttgart, 1991. 3 See, for example, S. R. Collinson and D. E. Fenton, Coord. Chem. Rev., 1996, 148, 19; H. Okawa and H. Sakiyama, Pure Appl. Chem., 1995, 67, 273; L. Que, jun. and Y. Dong, Acc. Chem. Res., 1996, 29, 190. 4 (a) D. Volkmer, B. Hommerich, K. Griesar, W. Haase and B. Krebs, Inorg. Chem., 1996, 35, 3792; (b) M. Rapta, P. Kamaras and G.B. Jameson, Polyhedron, 1996, 15, 1943; (c) D. E. Fenton and H. Okawa, Chem. Ber./Recueil, 1997, 130, 433. 5 J. H. Satcher, jun., M. W. Droege, T. J. R. Weakley and R. T. Taylor, Inorg. Chem., 1995, 34, 3317. 6 H. Steinhagen and G. Helmchen, Angew. Chem., Int. Ed. Engl., 1996, 35, 2339. 7 P. J. Steel, Coord. Chem. Rev., 1990, 106, 227; A. P. Sadimenko and S. S. Basson, ibid., 1996, 147, 247. 8 T. G. Schenck, J. M. Downes, C. R. C. Milne, P. B. Mackenzie, H. Boucher, J. Whelan and B.Bosnich, Inorg. Chem., 1985, 24, 2334. 9 (a) T. Kamiusuki, H. Okawa, E. Kitaura, M. Koikawa, N. Matsumoto, S. Kida and H. Oshio, J. Chem. Soc., Dalton Trans., 1989, 2077; (b) T. Kamiusuki, H. Okawa, N. Matsumoto and S. Kida, J. Chem. Soc., Dalton Trans., 1990, 195; (c) T. Kamiusuki, H. Okawa, K. Inoue, N. Matsumoto, M. Kodera and S. Kida, J. Coord. Chem., 1991, 23, 201; (d ) M. Itoh, K. Motoda, K. Shindo, T. Kamiusuki, H. Sakiyama, N. Matsumoto and H. Okawa, J. Chem.Soc., Dalton Trans., 1995, 3635. 10 B. Mernari, F. Abraham, M. Lagrenne, M. Drillon and P. Legoll, J. Chem. Soc., Dalton Trans., 1993, 1707. 11 L. Behle, M. Neuburger, M. Zehnder and T. A. Kaden, Helv. Chim. Acta, 1995, 78, 693. 12 J. Pons, X. López, E. Benet, J. Casabó, F. Teixidor and F. J. Sánchez, Polyhedron, 1990, 9, 2835; J. Pons, F. J. Sánchez, A. Labarta, J. Casabó, F. Teixidor and A. Caubet, Inorg. Chim. Acta, 1993, 208, 167. 13 (a) F. Meyer, S. Beyreuther, K. Heinze and L. Zsolnai, Chem. Ber./ Recueil, 1997, 130, 605; (b) F. Meyer, K. Heinze, B. Nuber and L. Zsolnai, J. Chem. Soc., Dalton Trans., following paper; (c) F. Meyer, A. Jacobi and L. Zsolnai, Chem. Ber./Recueil, 1997, 130, 1441. 14 See, for example, (a) V. P. Hanot, T. D. Robert, J. Kolnaar, J. G. Haasnoot, J. Reedijk, H. Kooijman and A. L. Spek, J. Chem. Soc., Dalton Trans., 1996, 4275; (b) P. L. Jones, J. C. Jeffery, J. A. McCleverty and M. D. Ward, Polyhedron, 1997, 16, 1567; (c) J. C. Jeffery, P. L. Jones, K. L. V. Mann, E. Psillakis, J. A. McCleverty, M. D. Ward and C. M. White, Chem. Commun., 1997, 175. 15 E. Mugnaini and P. Grünanger, Atti. Accad. Naz. Lincei, Cl. Sci. Fis. Mat. Nat., Rend., 1953, 14, 958. 16 G. Fallani, R. Morassi and F. Zanobini, Inorg. Chim. Acta, 1975, 12, 147; P. Stavropoulos, M. C. Muetterties, M. Carrié and R. H. Holm, J. Am. Chem. Soc., 1991, 113, 8485. 17 D. Nicholls, in Comprehensive Inorganic Chemistry, eds. J. C. Bailar, H. J. Eméleus, Sir R. Nyholm and A. F. Trotman-Dickenson, 1st edn., Pergamon, Oxford, 1973, vol. 3, p. 1152 ff. 18 J. Huheey, E. Keiter and R. Keiter, Anorganische Chemie, 2nd edn., Walter de Gruyter, Berlin, 1995, p. 517. 19 M. Ciampolini, N. Nardi and G. P. Speroni, Coord. Chem. Rev., 1966, 1, 222; C. Furlani, Coord. Chem. Rev., 1968, 3, 141. 20 C. J. O’Connor, Prog. Inorg. Chem., 1982, 29, 203. 21 (a) V. M. Crawford, M. W. Richardson, J. R. Wasson, D. J. Hodgson and W. E. Hatfield, Inorg. Chem., 1976, 15, 2107; (b) O. Kahn, Molecular Magnetism, VCH, Weinheim, 1993. 22 P. Chauduri, H.-J. Küppers, K. Wieghardt, S. Gehring, W. Haase, B. Nuber and J. Weiss, J. Chem. Soc., Dalton Trans., 1988, 1367. 23 K. K. Nanda, R. Das, L. K. Thompson, K. Venkatsubramanian, P. Paul and K. Nag, Inorg. Chem., 1994, 33, 1188; K. K. Nanda, L. K. Thompson, J. N. Bridson and K. Nag, J. Chem. Soc., Chem. Commun., 1994, 1337. 24 G. M. Sheldrick, SHELXTL PLUS, Program Package for Structure Solution and Refinement, Siemens Analytical Instruments, Madison, WI, 1990; SHELXL 93, Program for Crystal Structure Refinement, Universität Göttingen, 1993; SHELXS 86, Program for Crystal Structure Solution, Universität Göttingen, 1986. Received 31st July 1997; Paper 7/05543I

ISSN:1477-9226    

DOI:10.1039/a705543i

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1999, 201–207 201 Preparation and structural characterisation of isocyanide gold(I) nitrates, [Au(NO3)(CNR)] (R 5 Et, But or C6H3Me2-2,6); new auriophilic motifs† Trevor J. Mathieson,a Alan G. Langdon,a Neil B. Milestone b and Brian K. Nicholson *a a Department of Chemistry, University of Waikato, Private Bag 3105, Hamilton, New Zealand. E-mail: b.nicholson@waikato.ac.nz b Industrial Research Ltd, Box 31-310, Lower Hutt, New Zealand Received 13th August 1998, Accepted 16th November 1998 The first examples of isocyanide gold(I) nitrates, [Au(NO3)(CNR)] (R = Et, But or C6H3Me2-2,6) have been prepared from the corresponding chlorides and AgNO3.Full characterisation included crystal structure determinations for each example. The structures of the analogous compounds [AuCl(CNR)] (R = Et or C6H3Me2- 2,6) were also determined for comparison. All species show Au ? ? ?Au interactions in the solid state, but with diVerent modes of aggregation; [AuCl(CNEt)] and [Au(NO3)(CNBut)] have infinite zigzag chains, [AuCl- (CNC6H3Me2-2,6)] has a ‘broken’ chain of tetrameric units, [Au(NO3)(CNEt)] has a linked chain of tetrameric units, while [Au(NO3)(CNC6H3Me2-2,6)] has a highly compressed chain.In each instance the Au ? ? ?Au interactions for [Au(NO3)(CNR)] are shorter than for the analogous [AuCl(CNR)], suggesting NO3 2 enhances these secondary bonds. This is in direct contrast to previous theoretical predictions.The structure of the solvated ionic compound [Au(CNC6H3Me2-2,6)2]NO3 has also been determined. Introduction Linear two-co-ordinate complexes are ubiquitous in gold(I) chemistry, and complexes of the type [AuX(L)] formed through the combination of a neutral ligand L and an anionic ligand X have been long known.1 More recently, it has been recognised that the packing of these molecules in the solid state is often influenced by secondary Au ? ? ?Au interactions (of similar energy to hydrogen-bonding forces) unless they are precluded for steric reasons.2,3 This phenomenon has been termed4 ‘auriophilicity’.Several theoretical studies have examined the origin of these interactions which occur between AuI and other closed-shell d10 metal ions, and have attributed them to correlation eVects enhanced by relativistic eVects.5–7 The phenomenon is now suYciently well established to be used in the design of specific solid state polymers.8 Gold(I) co-ordination chemistry is characterised by a strong preference for polarisable (soft) donor atoms,2,3 so that for species [AuX(L)] the anion X is predominantly Cl2, Br2, I2, CN2 or SR2.Compounds with AuI–O bonds are relatively rare, and all the examples structurally characterised 9 have also incorporated stabilising phosphine ligands, usually PPh3. Haruta et al.10 have shown that metallic gold particles supported on transition metal oxides, prepared from coprecipitated precursors, are very active catalysts for the oxidation of CO to CO2 under ambient conditions.This is a process of significant technological interest. We are developing similar catalysts by deposition of organometallic precursors on metal oxide supports so needed gold complexes which would be readily absorbed onto surfaces and which could subsequently be thermally decomposed to Au0 at moderate temperatures. Absence of halide or sulfide was also essential since these act as catalyst poisons.10 We therefore explored the chemistry of previously unknown complexes of the general type [Au(NO3)- (CNR)] which appeared to fulfil our criteria, encouraged by † Dedicated to Professor Warren Roper on the occasion of his 60th birthday.parallel reports of the use of [Au(NO3)(PPh3)] for similar purposes. 11 The successful use of the new complexes for catalyst formation will be discussed in a future paper; herein we report the preparation and crystal structures of the novel compounds [Au(NO3)(CNR)] [R = Et, But or xylyl (2,6-dimethylphenyl)], together with the structures of [AuCl(CNR)] (R = Et or xylyl) for comparison of the auriophilic interactions in the solid state.The ionic species [Au(CNC6H3Me2-2,6)2]NO3 is also described. Aspects of this work have been communicated.12 Experimental Preparations of gold nitrate complexes were carried out under an atmosphere of dry argon, in dried glassware which was wrapped in foil to minimise exposure to light.Solvents were routinely distilled under an inert atmosphere before use. Light petroleum spirit refers to a bp 60–80 8C fraction. The NMR spectra were recorded under standard conditions on a Bruker DRX400 spectrometer in CDCl3 solutions, IR spectra as KBr discs on a Perkin-Elmer Model 1600 FTIR spectrometer. DiVerential thermal analysis was carried out on a Perkin- Elmer DSC6 diVerential scanning calorimeter, with a scan rate of 15 8C min21. Microanalyses were carried out at the Campbell Laboratory, University of Otago.The isocyanides RNC (R = Et, But or xylyl) were prepared following literature methods,13 and the corresponding [AuCl(CNR)] compounds formed by displacement of tetrahydrothiophene from [AuCl(SC4H8)] in the standard manner,14,15 and showed satisfactory microanalytical data. Melting points were [AuCl- (CNEt)] 115 8C and [AuCl(CNC6H3Me2-2,6)] 140 8C. Syntheses [Au(NO3)(CNBut)]. A solution of AgNO3 (0.30 g, 1.8 mmol) in MeOH (30 mL) was cooled to 245 8C.To this was added [AuCl(CNBut)] (0.45 g, 1.4 mmol) in CH2Cl2 (10 mL), maintaining the temperature at 245 8C. After stirring for 30 min the solvent was evaporated under vacuum and the solid residue immediately extracted with cold CH2Cl2 (5 mL). Light petrol-202 J. Chem. Soc., Dalton Trans., 1999, 201–207 eum was added to the filtered extract to precipitate the product as white microcrystals of [Au(NO3)(CNBut)] (0.32 g, 65%) (Found: C, 17.76; H, 2.47; N, 8.30.Calc. for C5H9AuN2O3: C, 17.55; H, 2.65; N, 8.19%). CAUTION: decomposes explosively without melting at 118 8C. IR (cm21): 2258 (CN), 1512, 1272, 977 (NO3 2). NMR: 1H, d 1.60 (CH3); 13C, d 29.7 (CH3), 60.1 [(CH3)3CN] and 122.2 (N]] ] C). [Au(NO3)(CNEt)]. This complex was prepared in a directly analogous fashion from [AuCl(CNEt)] (0.103 g, 0.36 mmol) and AgNO3 (0.076 g, 0.45 mmol) in mixed MeOH–CH2Cl2 solvent at 245 8C. Work-up as before gave [Au(NO3)(CNEt)] (0.076 g, 67%) (Found: C, 11.79; H, 1.59; N, 8.82.Calc. for C3H5AuN2O3: C, 11.47; H, 1.60; N, 8.92%). Decomposes without melting at 106 8C. IR (cm21): 2267, 1514, 1274 and 978. NMR: 1H, d 1.53 (CH3), 3.75 (CH2); 13C, d 13.9 (CH3), 39.8 (CH2) and 128.4 (N]] ] C). [Au(NO3)(CNC6H3Me2-2,6)]. Similarly from [AuCl(CNC6H3- Me2-2,6)] (0.137 g, 0.41 mmol) and AgNO3 (0.075 g, 0.44 mmol) in mixed MeOH–CH2Cl2 solvent. Work-up as before gave [Au(NO3)(CNC6H3Me2-2,6)] (0.114 g, 76%) (Found: C, 27.69; H, 2.04; N, 7.30.Calc. for C9H9AuN2O3: C, 27.71; H, 2.33; N, 7.17%). Decomposes without melting at 125 8C. IR (cm21): 2215, 1529, 1274 and 958. NMR: 1H, d 2.47 (CH3), 7.19 (meta CH) and 7.37 (para CH); 13C, d 18.7 (CH3), 124.1 (ipso- C), 128.6 (meta-C), 131.5 (para-C), 136.5 (ortho-C) and 134.9 (N]] ] C). X-Ray crystallography Single crystals were obtained from slow diVusion of pentane into a CH2Cl2 solution of [AuCl(CNR)] (R = Et or xylyl) at 20 8C, of [Au(NO3)(CNR)] (R = Et or But) at 4 8C and of [Au(NO3)(CNC6H3Me2-2,6)] at 220 8C.The crystal of [Au- (CNC6H3Me2-2,6)2]NO3 used was formed during one recrystallisation of [Au(NO3)(CNC6H3Me2-2,6)]. Unit cell dimensions and intensity data were obtained on a Siemens SMART CCD diVractometer, operating at 203 K, with monochromatic Mo-Ka radiation, l 0.71073 Å. The data collection nominally covered over a hemisphere of reciprocal space, by a combination of three sets of exposures; each set had a diVerent f angle for the crystal and each exposure covered 0.38 in w.The crystal to detector distance was 5.0 cm. The data sets were corrected using SADABS.16 For some of the structures this led to physically improbable values of Tmax,min, but nevertheless gave what appeared to be the best data sets, based on Rint values and refinement behaviour. The values of T are therefore not strictly transmission factors in an absolute sense, rather they are correction factors for all of the anisotropic eVects, and for variations during data collection.The SHELX 97 programs were used for all other calculations.17 The five structure determinations for [AuCl(CNR)] (R = Et, or xylyl) and [Au(NO3)(CNR)] (R = Et, But or xylyl) were routine, solved by automatic interpretation of Patterson maps and developed normally. In the final cycles of least-squares refinement based on F 2 against all data all non-hydrogen atoms were treated anisotropically and hydrogen atoms included in their calculated positions.For the structure of [Au(CNC6H3Me2-2,6)2]NO3 the data were consistent with the space groups C2, Cm or C2/m, with the latter being chosen for refinement. The gold atom was located on a site of 2/m symmetry, and a subsequent diVerence map located the remaining atoms of the cation. The remaining electron density was assigned as follows: a CH2Cl2 of crystallisation was found with site occupancy ca. 0.5, the two Cl atoms being well defined but the C atom was disordered over two symmetry equivalent sites.The nitrate anion was also disordered over two equivalent sites on a mirror plane, and appeared to be superimposed on a fragment which was consistent with a molecule of MeOH. It was assumed that this site of the crystal lattice was occupied equally by NO3 2 and MeOH (note that charge neutrality means that each of the sites can only contain half a NO3 2 ion). This model refined sensibly in C2/m. It was possible to refine the structure with non-disordered NO3 2 in the lower space groups, but there were clearly pseudo-symmetry problems and the refinement did not give significantly better agreement factors, so the disordered structure in the higher symmetry space group was preferred. For this structure H atoms were not included in the refinement.Details concerning the crystal structures are given in Table 2, and selected structural parameters in Table 3. CCDC reference number 186/1250.See http://www.rsc.org/suppdata/dt/1999/201/ for crystallographic files in .cif format. Results and discussion Synthesis The isocyanide gold(I) nitrate complexes were prepared in reasonable yields according to eqn. (1). The reactions were best [AuCl(CNR)] 1 AgNO3 æÆ [Au(NO3)(CNR)] 1 AgCl (1) carried out in a mixed MeOH–CH2Cl2 solution at 245 8C with exclusion of light. Straightforward work-up gave the pure complexes, the first examples of C,O-bonded gold(I) species.Samples can be stored indefinitely at 220 8C, and deteriorate only slowly at room temperature in the absence of light, so stability is reasonable. However on attempting to record melting points it was noted that [Au(NO3)(CNBut)] in particular reproducibly decomposed violently without melting. DiVerential thermal analysis of the [Au(NO3)(CNR)] complexes showed that all of them exhibited exothermic decomposition peaks centred around 139 (R = Et), 106 (R = But) or 125 8C (R = xylyl).The novel compounds were characterised by microanalysis and by IR spectra which showed bands readily assigned to C]] ] N and monodentate NO3 2 group vibrations.18 The NMR data were also consistent with the proposed formulae, and need little discussion, except perhaps for the 13C signals for the ligated isocyanide carbon atom which have not been previously reported for C,O-bonded gold(I) complexes. The data are listed in Table 1 for the ‘free’ ligands and for the chloro and nitrate complexes.There is a consistent shift to higher field of about 20 ppm going from the ‘free’ ligand to the [AuCl(CNR)] complexes, and a further shift of 6–10 ppm for the [Au(NO3)(CNR)] complexes. This presumably reflects the higher electronegativity of the trans ligand for nitrate compared with softer chloride. Structure determinations (i) Molecular structures. The structures of the two chloro complexes [AuCl(CNR)] (R = Et or xylyl) were determined for comparison with the corresponding nitrates, and to add to the recent series with R = Me, But, Ph, Mes (2,4,6-trimethylphenyl) and CH2C(O)OMe reported by Schmidbaur and co-workers,14 following an earlier report for the R = But example.19 Individual Table 1 The 13C NMR shifts for the N]] ] C carbon atom of isocyanide gold complexes d R Et But C6H3Me2-2,6 CNR 155.0 152.8 167.9 [AuCl(CNR)] 134.0 132.2 144.9 [Au(NO3)(CNR)] 128.4 122.2 134.9J.Chem. Soc., Dalton Trans., 1999, 201–207 203 Table 2 Details for the X-ray crystallography determinations Formula Mr Crystal system Space group a/Å b/Å c/Å b/8 V/Å3 Z Dc/g cm23 m(Mo-Ka)/mm21 Tmax,min F(000) Crystal size/mm q Range/8 Total data Unique data Rint R1 [2s(I) data] (all data) wR2 Goodness of fit Final De/e Å23 [AuCl(EtCN)] C3H5AuClN 287.50 Monoclinic P21/m 4.4626(5) 6.3014(7) 10.0629(11) 96.100(2) 281.37(5) 2 3.393 26.5 0.912, 0.058 252 0.18 × 0.15 × 0.05 2 to 28 1742 680 0.051 0.0549 0.0562 0.1385 1.055 4.26, 24.26 [AuCl(CNC6H3Me2-2,6)] C9H9AuClN 363.59 Monoclinic P21/n 10.6513(3) 17.3099(4) 11.0902(2) 97.846(1) 2025.59(8) 8 2.385 14.7 0.367, 0.174 1328 0.60 × 0.11 × 0.10 2 to 28 11807 4511 0.040 0.0402 0.0610 0.0970 1.013 3.37, 21.48 [Au(NO3)(CNEt)] C3H5AuN2O3 314.06 Monoclinic P21/n 8.1005(1) 7.8684(1) 20.3639(1) 96.987(1) 1288.31(3) 8 3.238 22.7 0.041, 0.003 1120 0.45 × 0.39 × 0.29 2 to 25 7434 2267 0.048 0.0470 0.0544 0.1370 1.036 2.29, 23.56 [Au(NO3)(CNBut)] C5H9AuN2O3 342.11 Monoclinic P21/n 6.2642(1) 13.5595(3) 10.6118(1) 102.18 881.07(3) 4 2.579 16.7 0.102, 0.023 624 0.43 × 0.34 × 0.23 3 to 28 4105 1921 0.055 0.0536 0.0631 0.1443 1.012 2.32, 23.12 [Au(NO3)(CNC6H3Me2-2,6)] C9H9AuN2O3 390.15 Monoclinic P21/n 15.1075(6) 3.7802(2) 8.0762(6) 103.76(1) 1002.69(7) 4 2.584 14.7 0.527, 0.047 720 0.54 × 0.11 × 0.05 2 to 25 5881 1774 0.058 0.0649 0.0762 0.1652 1.005 7.12, 24.28 [Au(CNC6H3Me2-2,6)2]NO3? MeOH?0.5CH2Cl2 C19.5H22.5AuClN3O4 595.32 Monoclinic C2/m 20.7234(7) 6.7276(1) 8.3385(3) 107.925(2) 1106.11(5) 2 1.781 6.8 0.618, 0.407 577 0.22 × 0.11 × 0.05 2 to 26 6203 1237 0.023 0.0420 0.0499 0.1165 1.035 0.892, 21.737204 J.Chem. Soc., Dalton Trans., 1999, 201–207 Table 3 Selected structural parameters (bond lengths in Å, angles in 8) for isolated molecules [AuX(CNR)] a Au–Cl Au–C(1) C(1)]] ] N Au–O(1) O(1)–N(1) O(2/3)–N(1) Cl–Au–C(1) O(1)–Au–C(1) Au–O(1)–N(1) [AuCl(CNEt)] 2.277(5) 1.90(2) 1.20(2) 177.9(6) [AuCl(CNC6H3Me2-2,6)] b 2.257(2) 1.94(1) 1.14(1) 177.8(3) [Au(NO3)(CNEt)] b 1.93(2) 1.12(2) 2.033(11) 1.32(2) 1.21(2) 177.0(5) 115.0(7) [Au(NO3)(CNBut)] 1.92(1) 1.13(2) 2.062(9) 1.31(1) 1.22(1) 176.3(4) 113.1(7) [Au(NO3)(CNC6H3Me2-2,6)] 1.905(16) 1.15(2) 2.033(10) 1.33(2) 1.20(2) 174.8(5) 110.7(8) a Details of the auriophilic intermolecular interactions are given in the captions to the figures showing the structures.b Averaged for the two independent molecules. molecules are shown in Fig. 1, and require little discussion. For each, the co-ordination about the Au(1) atom is essentially linear (1788 in each case). The bond distances within the molecules do not diVer significantly from corresponding ones in related structures reported previously, although small variations would not be readily detected because of the diYculty in locating lighter atoms accurately in the presence of gold atoms. The crystal packing and auriophilic interactions are discussed later. Individual molecules of the three [Au(NO3)(CNR)] examples determined are shown in Fig. 2. They all consist of essentially linear (174–1778) AuI co-ordinated to both the C of a normal isocyanide ligand and to one oxygen atom of a monodentate nitrate group. The Au–C distance does not diVer significantly from those in the analogous chlorides, while the Au–O bond Fig. 1 The structures of isolated molecules of (a) [AuCl(CNEt)] and (b) [AuCl(CNC6H3Me2-2,6)] showing atom numbering. Fig. 2 The structures of individual molecules of (a) [Au(NO3)- (CNEt)], (b) [Au(NO3)(CNBut)] and (c) [Au(NO3)(CNC6H3Me2-2,6)]. lengths of 2.03–2.06 Å appear to be slightly shorter than that in [Au(NO3)(PPh3)] of 2.074(8) Å, the only other gold(I) nitrate to have been structurally characterised.20 As expected, the average N–O distance for the ligated oxygen atoms (1.32 Å) is longer than for the non-co-ordinated ones (1.21 Å).The Au–O–N angles are similar for all three examples in the range 111–1158.(ii) Crystal structures. The crystal packing of [AuCl(CNEt)] is shown in Fig. 3(a), and exhibits a zigzag chain of antiparallel molecules linked via Au ? ? ?Au interactions (3.554 Å). Similar chains have been described 19 for [AuCl(CNBut)] where the Au ? ? ?Au distance is 3.695 Å, and for [AuCl(CNMe)] 14 with a Au ? ? ?Au length of 3.637 Å. While the longer distance in the But example is expected for a bulkier ligand, the reason for the longer distance in the Me compound is less obvious.The stereoview of the packing for [AuCl(CNEt)] [Fig. 3(b)] shows the chain units stack so that the Au atoms of one layer lie between the C]] ] N groups of the neighbouring one. For [AuCl(CNC6H3Me2-2,6)] a unique “broken chain” packing was found. There are two independent molecules in the asymmetric unit, and these link across an inversion centre to give a tetrameric unit (Fig 4). The outer Au(1) ? ? ?Au(2) interaction (3.355 Å) is of the crossed-dimer type, while the central one, Au(1) ? ? ?Au(19), 3.654 Å, is an antiparallel one.These distances follow the established pattern that distances are shorter between neighbouring molecules that lie orthogonal to each other, than between parallel or antiparallel ones. The closest Au ? ? ?Au distance between separate tetrameric units is 4.071 Å, too long to be considered significant and is the “break” in the chain. This structure lies between those of the homologous species [AuCl(CNPh)] and [AuCl(CNMes)],14 the former having an antiparallel chain structure (of the type described above for [AuCl(CNEt)]) with Au ? ? ?Au 3.463 Å, and the latter forming separated dimer units with Au ? ? ?Au 3.336 Å.An isolated tetrameric unit was also found for [Au(C]] ] CSiMe3)(CNBut)] with a very short Au ? ? ?Au distance of 3.124 Å, but this involved three molecular units aggregating about a single central one.21 The complex [Au(NO3)(CNBut)] has the most straightforward supramolecular structure of the three nitrate complexes analysed.As shown in Fig. 5 it exhibits an antiparallel chain structure directly analogous to those of three other [AuX(CNBut)] complexes,13 though the average Au ? ? ?Au distance (3.31 Å) is markedly shorter than those of the X = CN (3.57 Å),22 Cl (3.70 Å) 19 or Br (3.69 Å) 14 examples; this is not consistent with theoretical predictions that Au ? ? ?Au interactions in [AuX(L)] should be enhanced as the softness of X increases.5 However Pyykkö’s calculations 5 were based on perpendicular dimers, where the electrostatic dipole–dipole interactions vanish.The nitrate group can orientate itself to provide a smaller steric interaction with adjacent groups compared with chloride, for example. In the common antiparallel stacking arrangement the X group is directly opposite the electron-richJ. Chem. Soc., Dalton Trans., 1999, 201–207 205 Fig. 3 (a) The packing of [AuCl(CNEt)] in the crystal showing the infinite zigzag chain [Au ? ? ?Au 3.5536(6) Å; Au ? ? ? Au ? ? ?Au 124.90(1)8].(b) A stereoview showing the packing of the chain units in the crystal. C]] ] N of the isocyanide, which may lengthen the Au ? ? ? Au distance by repulsion between the ligands when X is also electron-rich. For [Au(NO3)(CNEt)] the packing consists of a concertina’d chain, which gives tetrameric units linked together as shown in Fig. 6. Each Au is connected to three others but even so the Au ? ? ?Au interactions are relatively short, with Au(1) ? ? ? Au(19) 3.194, Au(19) ? ? ?Au(2) 3.193, Au(2) ? ? ?Au(1) 3.357 and Au(2) ? ? ?Au(29) 3.286 Å.The shorter distances are between Fig. 4 The “broken chain” packing of the tetrameric units of [AuCl(CNC6H3Me2-2,6)] in the crystal [Au(1) ? ? ?Au(2) 3.3555(5); Au(1) ? ? ?Au(19) 3.6545(6) Å; Au(19) ? ? ?Au(1) ? ? ?Au(2) 97.60(1)8]. Fig. 5 The chain structure of [Au(NO3)(CNBut)] in the crystal [Au(1) ? ? ?Au(19) 3.2963(8); Au(1) ? ? ?Au(10) 3.3232(8) Å; Au(19) ? ? ? Au(1) ? ? ?Au(10) 142.28(5)8]. antiparallel monomers, while the longest distance is between head-to-head neighbours.If the Au(1) ? ? ?Au(2) and Au(19) ? ? ? Au(29) links in each tetrameric unit were stretched then a zigzag chain would result, providing a relationship between [Au(NO3)- (CNEt)] and the chain of [Au(NO3)(CNBut)]. Averaging the four independent Au ? ? ?Au distances for [Au(NO3)(CNEt)] gives 3.25 Å, slightly shorter than the value for [Au(NO3)(CNFig. 6 The concertina’d chain structure for [Au(NO3)(CNEt)] [Au(19) ? ? ?Au(2) 3.1932(7); Au(1) ? ? ?Au(19) 3.1941(10); Au(2) ? ? ? Au(29) 3.2856(11); Au(2) ? ? ?Au(1) 3.3575(7) Å]. Fig. 7 The compressed chain structure of [Au(NO3)(CNC6H3Me2- 2,6)] [Au(1) ? ? ?Au(19) 3.245(1); Au(19) ? ? ?Au(10) 3.780(1) Å].206 J. Chem. Soc., Dalton Trans., 1999, 201–207 But)] (3.30 Å), presumably a steric eVect. More significantly the average Au ? ? ?Au distance is markedly shorter than that in [AuCl(CNEt)], indicating again that the nitrate group enhances auriophilic bonding compared to Cl in analogous compounds.The tetrameric units in this structure have some similarity to those in the ionic compound {[Au(Ph2C]] NH)2][AuCl2]}2, which however are not further linked.23 The complex [Au(pip)- Cl] (pip = piperidine) has square Au4 units in the crystal, again not further linked.24 The crystal packing for [Au(NO3)(CNC6H3Me2-2,6)] is different again, as shown in Fig. 7.It can be described as a compressed zigzag chain with primary Au ? ? ?Au distances of 3.245 Å. There are additional, longer Au ? ? ?Au interactions of 3.780 Å between every second gold atom. This leads to an acute Au ? ? ? Au ? ? ?Au angle of 718, which compares with equivalent angles of 125–1408 in the other chain structures discussed above. While the longer distance is at the outer limit of what is considered an auriophilic interaction, it is less than some of the Au ? ? ?Au linkages found for [AuI- (CNPh)] (>3.80 Å).14 The reason for the compressed packing Fig. 8 An alternative view of the crystal packing for [Au(NO3)(CNC6H3Me2-2,6)], showing the p stacking of the arene rings. Fig. 9 (a) The arrangement of the ions and solvent molecules in the crystal of [Au(CNC6H3Me2-2,6)2]NO3?MeOH?0.5CH2Cl2. Only one orientation of the disordered CH2Cl2 is shown, while the anion site contains superimposed NO3 2 and MeOH species, with a 1 : 1 occupancy (see text).(b) A stereoview of the [Au(CNC6H3Me2-2,6)2]1 cations only, showing the p stacking interactions.J. Chem. Soc., Dalton Trans., 1999, 201–207 207 may lie in the p stacking of the xylyl rings, Fig. 8, which are 3.780 Å apart; these could reinforce the additional Au ? ? ? Au interactions. (iii) The structure of [Au(CNC6H3Me2-2,6)2]NO3. In the initial attempt to determine the structure of [Au(NO3)(CNC6H3Me2- 2,6)] the crystal selected turned out to be a solvated ionic species [Au(CNC6H3Me2-2,6)2]NO3?MeOH?0.5CH2Cl2. This structure consisted of separated [Au(CNC6H3Me2-2,6)2]1 cations and NO3 2 anions, the former occupying a site of 2/m symmetry and the latter one of m symmetry.Charge neutrality requires that only half of the anion sites are occupied by NO3 2 ions, and it appears the otherwise empty sites have incorporated MeOH molecules. There are no auriophilic interactions in this crystal, the packing appearing to be determined by infinite p stacking of the xylyl groups of the cations in an interleaving fashion.The distance between the adjacent arene rings is 3.36 Å, essentially the same as between the layers of graphite (3.35 Å). In [Au(CCPh)(CNC6H3Me2-2,6)] there are isolated dimers held together by both Au ? ? ?Au and p–p interactions of 3.33 Å.25 The packing in [Au(CNC6H3Me2-2,6)2]NO3 leaves space between adjacent gold centres for the gold cations to be linked together by weak Au ? ? ? ClCH2Cl ? ? ?Au interactions (Au ? ? ? Cl 2.99 Å) involving dichloromethane molecules in the lattice (Fig. 9).The structure can be compared with those of other [Au(CNR)2]1 salts (R = Ph or Mes) which have been described by Schmidbaur et al.26 These, however, show neither Au ? ? ? Au nor p-stacking interactions. Conclusion Isocyanide gold nitrates are less stable than other [AuX(CNR)] and [Au(NO3)(PR3)] species but are nevertheless readily synthesized. The combination of a sterically undemanding CNR ligand and a flat NO3 2 anion appears to favour short Au ? ? ? Au auriophilic interactions in crystals, invariably more pronounced than in corresponding [AuCl(CNR)] compounds.Whether this should be attributed to the non-polarisable NO3 2 ion encouraging stronger Au ? ? ?Au forces per se, which is contrary to expectations based on theoretical calculations,5 or to lesser repulsion between adjacent ligands cannot be decided from the present examples.What is clear, however, is that the full range of structural motifs arising from secondary Au ? ? ?Au interactions is still to be developed. Acknowledgements We are grateful to Associate Professor CliV Rickard and Allen Oliver, University of Auckland, for X-ray data sets, and to the University of Waikato for financial support. Helpful discussions with Associate Professor Graham Bowmaker, University of Auckland, are acknowledged with thanks. References 1 R. J. Puddephatt, The Chemistry of Gold, Elsevier, Amsterdam, 1978; Comprehensive Organometallic Chemistry, eds.G. Wilkinson, F. G. A. Stone and E. W. Abel, Pergamon, Oxford, 1982, ch. 15; A. Grohmann and H. Schmidbaur, Comprehensive Organometallic Chemistry II, eds. G. Wilkinson, F. G. A. Stone and E. W. Abel, Pergamon, Oxford, 1995. 2 H. Schmidbaur, Chem. Soc. Rev., 1995, 24, 383. 3 D. M. P. Mingos, J. Chem. Soc., Dalton Trans., 1996, 561. 4 H. Schmidbaur, Gold Bull., 1990, 23, 11. 5 P. Pyykkö and Y.Zhao, Angew. Chem., Int. Ed. Engl., 1991, 30, 604; P. Pyykkö, Chem. Rev., 1997, 97, 597; P. Pyykkö, N. Runeberg and F. Mendizabal, Chem. Eur. J., 1997, 3, 1451; P. Pyykkö and F. Mendizabal, Chem. Eur. J., 1997, 3, 1458. 6 K. Angermaier, G. A. Bowmaker, E. N. de Silva, P. C. Healy, B. E. Jones and H. Schmidbaur, J. Chem. Soc., Dalton Trans., 1996, 3121. 7 L. F. Veiros and M. J. Calhorda, J. Organomet. Chem., 1996, 510, 71. 8 R. J. Puddephatt, Chem. Commun., 1998, 1055. 9 Cambridge Structural Database, April 1998 release. 10 M. Haruta, N. Yamada, T. Kobayashi and S. Iijima, J. Catal., 1989, 115, 301; M. Haruta, S. Tsubota, T. Kobayashi, H. Kageyama, M. J. Genet and B. Delmon, J. Catal., 1993, 144, 175. 11 Y. Yuan, A. P. Kozlova, K. Asakura, H. Wan, K. Tsai and Y. Iwasawa, J. Catal., 1997, 170, 191; Y. Yuan, K. Asakura, H. Wan, K. Tsai and Y. Iwasawa, Chem. Lett., 1996, 755. 12 T. J. Mathieson, A. G. Langdon, N. B. Milestone and B. K. Nicholson, Chem. Commun., 1998, 371. 13 G. W. Gokel, R. P. Widera and W. P. Weber, Org. Synth., 1976, 55, 96. 14 W. Schneider, K. Angermaier, A. Sladek and H. Schmidbaur, Z. Naturforsch., Teil B, 1996, 51, 790. 15 G. E. Coates, C. Kowala and J. M. Swan, Aust. J. Chem., 1966, 19, 539; C. Kowala and J. M. Swan, Aust. J. Chem., 1966, 19, 547; F. Bonati and G. Minghetti, Gazz. Chim. Ital., 1973, 103, 373. 16 R. H. Blessing, Acta Crystallogr., Sect. A, 1995, 51, 33. 17 G. M. Sheldrick, SHELX 97, Programs for X-ray crystallography, University of Göttingen, 1997. 18 K. Nakamoto, Infrared and Raman spectra of inorganic and coordination compounds, Wiley, New York, 3rd edn., 1977. 19 D. S. Eggleston, D. F. Chodosh, R. Lee Webb and L. L. Davis, Acta Crystallogr., Sect. C, 1986, 42, 36. 20 P. F. Barron, L. M. Engelhardt, P. C. Healy, J. Oddy and A. H. White, Aust. J. Chem., 1987, 40, 1545; J.-C. Wang, M. N. I. Khan and J. P. Fackler, Acta Crystallogr., Sect. C, 1989, 45, 1008. 21 J. Vicente, M.-T. Chicote, M.-D. Abrisqueta and P. G. Jones, Organometallics, 1997, 16, 5628. 22 C.-M. Che, H.-K. Yip, W.-T. Wong and T.-F. Lai, Inorg. Chim. Acta, 1992, 197, 177. 23 W. Schneider, A. Bauer and H. Schmidbaur, J. Chem. Soc., Dalton Trans. 1997, 415. 24 J. J. Guy, P. G. Jones, M. J. Mays and G. M. Sheldrick, J. Chem. Soc., Dalton Trans., 1977, 8. 25 H. Xiao, K.-K. Cheung and C.-M. Che, J. Chem. Soc., Dalton Trans., 1996, 3699. 26 A. Bauer, W. Schneider and H. Schmidbaur, Inorg. Chem., 1997, 36, 2225; W. Schneider, A. Sladek, A. Bauer, K. Angermaier and H. Schmidbaur, Z. Naturforsch., Teil B, 1997, 52, 53. Paper 8/06399K

ISSN:1477-9226    

DOI:10.1039/a806399k

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

DALTON J. Chem. Soc., Dalton Trans., 1997, Pages 205–211 205 Reactions of [Mn(CO)3{Á5-C5H4[(Á5-C6H6)Mn(CO)3]}] and [WMe(CO)3{Á5-C5H4[(Á5-C6H6)Mn(CO)3]}] with aryllithium reagents Ronghua Li, Jiabi Chen,* Yong Yu and Jie Sun Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032, China The reactions of [Mn(CO)3{h5-C5H4[(h5-C6H6)Mn(CO)3]}] 1 and [WMe(CO)3{h5-C5H4[(h5-C6H6)Mn(CO)3]}] 2 with aryllithium reagents, LiR (R = o-, m-, p-MeC6H4, Ph, p-MeOC6H4 or p-CF3C6H4), in diethyl ether at low temperature afforded acylmetalate intermediates, which on alkylation with Et3OBF4 in aqueous solution at 0 8C gave alkoxycarbene complexes [Mn(CO)3{h5-C5H4[(h5-C6H6)(OC)2Mn]] C(OEt)R]}] and [WMe(CO)3{h5- C5H4[(h5-C6H6)(OC)2Mn]] C(OEt)R]}].The structure of [Mn(CO)3{h5-C5H4[(h5-C6H6)(OC)2Mn]] C(OEt)C6H4- Me-o]}], established by X-ray diffraction, shows that the carbene ligand is attached to the manganese atom co-ordinated to the h5-cyclohexadienyl moiety.Olefin-co-ordinated transition-metal carbene complexes and/or their isomerized products have been examined extensively in our laboratory.1–17 Earlier we demonstrated 1–12 several novel isomerizations of olefin ligands, and a series of isomerized carbene complexes with novel structure were isolated by the reactions of olefin-ligated metal carbonyl compounds with nucleophiles. The isomerizations and reaction products depend not only on the olefin ligands but also on the central metals.3–5,8,12–15 For instance, tricarbonyl(cycloheptatriene)iron and tricarbonyl(norbornadiene)iron reacted with aryllithium reagents, and subsequent alkylation with Et3OBF4 gave novel ring-opened isomerized complexes (Scheme 1).3,4 However, the reactions of tricarbonyl(cycloheptatriene)-molybdenum and -chromium14 and tetracarbonyl(norbornadiene)-chromium, -molybdenum and -tungsten 13,14 with aryllithium reagents under the same conditions gave normal olefin-co-ordinated carbene complexes in which the diene ligand and carbene ligand coexist stably (Scheme 2).In our previous research the central metals were usually the Group VIIIB metals (d8) and Group VIB metals (d6). Continuing our interest in olefin-co-ordinated metal carbene and carbyne complexes, we turned our attention to olefinligated carbonyl compounds of Group VIIB metal (d7), such as tricarbonyl(exo-cyclopentadienyl-h5-cyclohexadienyl)manganese, 18 which gave a series of normal olefin-co-ordinated manganese carbene complexes in this reaction (Scheme 3).17 In order further to investigate the effect of different metal centre, on the isomerization of the olefin ligand and the reaction Scheme 1 (i) (a) LiC6H4Me-o, (b) Et3OBF4; (ii) (a) LiR (R = C6H4Meo, C6H4Me-p or C6H4CF3-p), (b) Et3OBF4 Fe CO OC CO Fe OC CO (i ) Me C OEt Fe(CO)2 OEt R Fe COCO D6/04436K/A1 (ii ) CO products, we chose [Mn(CO)3{h5-C5H4[(h5-C6H6)Mn(CO)3]}] 1 and [WMe(CO)3{h5-C5H4[(h5-C6H6)Mn(CO)3]}] 2, in which the two metal centres are not directly bonded to each other, as starting materials in reactions with aryllithium reagents.This paper describes a detailed study of these reactions and the structural characterization of the resulting products. Experimental All the procedures were performed under a dry, oxygen-free nitrogen atmosphere using standard Schlenk techniques. The solvents were reagent grade, dried by refluxing over appropriate drying agents and stored over 4 Å molecular sieves under a nitrogen atmosphere.Tetrahydrofuran (thf) and diethyl ether were distilled from sodium–benzophenone, light petroleum (b.p. 30–60 8C) from CaH2, and CH2Cl2 from P2O5. The neutral Scheme 2 (i) (a) LiR (R = Ph, C6H4Me-o, C6H4Me-p or C6H4CF3-p), (b) Et3OBF4: (ii) (a) LiR (R = Ph, C6H4Me-o, C6H4Me-m, C6H4Me-p, C6H4OMe-p or C6H4CF3-p), (b) Et3OBF4 M CO OC CO M CO OC C OEt R M OC CO OC OC M CO OC CO C OEt R D6/04436K/A2 M = Cr or Mo (i ) (ii ) M = Cr, Mo or W Scheme 3 (i) (a) LiR (R = Ph, C6H4Me-o, C6H4Me-m, C6H4Me-p, C6H4OMe-p or C6H4CF3-p), (b) Et3OBF4 Mn CO OC CO Mn CO OC C OEt R D6/04436K/A3 Mn CO OC CO or (i)206 J.Chem. Soc., Dalton Trans., 1997, Pages 205–211 alumina used for chromatography was deoxygenated at room temperature under high vacuum for 16 h, deactivated with 5% w/w N2-saturated water, and stored under N2. Compounds 1,18 2,18 and 15,18 Et3OBF4,19 and aryllithium reagents 20–24 were prepared by literature methods.The IR spectra were measured on a Shimadzu IR-440 spectrophotometer, 1H NMR spectra on a Bruker AM-300 spectrometer at ambient temperature in (CD3)2CO solution with SiMe4 as the internal reference and electron ionization (EI) mass spectra on a Hewlett-Packard 5989A spectrometer. Melting points obtained on samples in sealed nitrogen-filled capillaries are uncorrected. Preparation [Mn(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4Me-o]}] 3.To a solution of compound 1 (70 mg, 0.16 mmol) in diethyl ether (30 cm3) at 278 8C was added dropwise LiC6H4Me-o20 (0.38 mmol) in diethyl ether (10 cm3) with stirring. The light yellow solution was stirred initially at 278 to 265 8C for 0.5 h and then at 260 to 245 8C for 4 h, during which time it turned yellow to orange-red. The resulting solution was evaporated to dryness under vacuum at 250 to 240 8C. To the orange solid residue obtained was added Et3OBF4 (ca. 3 g). This solid mixture was dissolved in N2-saturated water (20 cm3) at 0 8C with vigorous stirring and the mixture covered with light petroleum. Immediately afterward, Et3OBF4 (ca. 8 g) was added portionwise with vigorous stirring to the aqueous solution until it became acidic. The aqueous solution was extracted with light petroleum. The combined extract was evaporated in vacuo, and the residue chromatographed on an alumina column (neutral, 100–200 mesh, 1.6 × 10–15 cm) at 220 8C with light petroleum followed by light petroleum–Et2O (10 : 1) as the eluent.The orange-yellow band was eluted and collected. Removal of the solvent under vacuum and recrystallization of the crude product from light petroleum–CH2Cl2 solution at 280 8C gave 64 mg (71%, based on 1) of orange-red crystals of compound 3, m.p. 118–119 8C (decomp.). Mass spectrum: m/z 540 (M+), 484 (M+ 2 2CO), 440 (M+ 2 2CO 2 OC2H4), 412 (M+ 2 3CO 2 OC2H4), 400 (M+ 2 5CO), 384 (M+ 2 4CO 2 OC2H4), 356 (M+ 2 5CO 2 OC2H4), 344 [M+ 2 Mn(CO)3 2 2CO], 300 (C5H4C6H5MnCHC6H4CH3)+, 251 (MnC5H4C6H6Mn)+, 204 [MnCH(OC2H5)C6H4CH3]+ and 149 [(CH3C6H4)CH(OC2H5)]+ (Found: C, 57.9; H, 4.2. Calc.for C26H22Mn2O6: C, 57.8; H, 4.1%). [Mn(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4Mem]}] 4. Similarly, compound 1 (200 mg, 0.48 mmol) dissolved in ether (50 cm3) was reacted with LiC6H4Me-m20 (1.06 mmol) at 265 to 245 8C for 4 h. Subsequent alkylation and further treatment as describved above gave 165 mg (64%, based on 1) of orange-red crystals of 4, m.p. 90–92 8C (decomp). Mass spectrum: m/z 540 (M+), 484 (M+ 2 2CO), 440 (M+ 2 2CO 2 OC2H4), 412 (M+ 2 3CO 2 OC2H4), 400 (M+ 2 5CO), 384 (M+ 2 4CO 2 OC2H4), 356 (M+ 2 5CO 2 OC2H4), 344 [M+ 2 Mn(CO)3 2 2CO], 300 (C5H4C6H5MnCHC6H4CH3)+, 251 (MnC5H4C6H6Mn)+, 204 [MnCH(OC2H5)C6H4CH3]+ and 149 [(CH3C6H4)CH(OC2H5)]+ (Found: C, 57.7; H, 3.9. Calc. for C26H22Mn2O6: C, 57.8; H, 4.1%). [Mn(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4Mep]}] 5.Similarly, compound 1 (150 mg, 0.36 mmol) was allowed to react with LiC6H4Me-p20 (0.80 mmol) at 265 to 245 8C for 4 h. Subsequent alkylation and further treatment as described above afforded 134 mg (70%, based on 1) of 5 as orange-red crystals, m.p. 58–60 8C (decomp.). Mass spectrum: m/z 540 (M+), 484 (M+ 2 2CO), 440 (M+ 2 2CO 2 OC2H4), 412 (M+ 2 3CO 2 OC2H4), 400 (M+ 2 5CO), 384 (M+ 2 4CO 2 OC2H4), 356 (M+ 2 5CO 2 OC2H4), 344 [M+ 2 Mn- (CO)3 2 2CO], 300 (C5H4C6H5MnCHC6H4CH3)+, 251 (Mn- C5H4C6H6Mn)+, 204 [MnCH(OC2H5)C6H4CH3]+ and 149 [(CH3C6H4)CH(OC2H5)]+ (Found: C, 57.9; H, 3.55.Calc. for C26H22Mn2O6: C, 57.8; H, 4.1%). [Mn(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)Ph]}] 6. The reaction of compound 1 (200 mg, 0.48 mmol) with LiPh21 (1.10 mmol) was carried out at 260 to 240 8C for 4 h. Subsequent alkylation and further treatment as described above yielded 150 mg (60%, based on 1) of 6 as orange-red crystals, m.p. 100– 102 8C (decomp.).Mas spectrum: m/z 526 (M+), 502 (M+ 2 CO), 470 (M+ 2 2CO), 426 (M+ 2 2CO 2 OC2H4), 398 (M+ 2 3CO 2 OC2H4), 386 (M+ 2 5CO), 370 (M+ 2 4CO 2 OC2H5), 342 (M+ 2 5CO 2 OC2H4), 330 [M+ 2 Mn(CO)3 2 2CO], 251 (MnC5H4C6H6Mn)+, 190 [MnCH(OC2H5)C6H5]+ and 135 [(C6H5)CH(OC2H5)]+ (Found: C, 56.95; H, 3.8. Calc. for C25H20Mn2O6: C, 57.05; H, 3.85%). [Mn(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4OMep]}] 7. A solution of p-MeOC6H4Br (80 mg, 0.34 mmol) in ether (20 cm3) was mixed with LiBun 22 (0.34 mmol).After 30 min of stirring at room temperature, the resulting ether solution of LiC6H4OMe-p 23 was allowed to react, as described above, with compound 1 (70 mg, 0.17 mmol) at 260 to 240 8C for 4 h, followed by alkylation; further treatment gave 65 mg (70%, based on 1) of orange-red crystalline 7 which is a viscous oil at room temperature. Mass spectrum: m/z 556 (M+), 500 (M+ 2 2CO), 456 (M+ 2 2CO 2 OC2H4), 428 (M+ 2 3CO 2 OC2H4), 416 (M+ 2 5CO), 400 (M+ 2 4CO 2 OC2H4), 372 (M+ 2 5CO 2 OC2H5), 360 [M+ 2 Mn(CO)3 2 2CO], 251 (MnC5H4C6H6Mn)+, 220 [MnCH(OC2H5)C6H4OCH3]+ and 165 [(CH3OC6H4)CH(OC2H5)]+ (Found: C, 53.2; H, 3.6.Calc. for C26H22Mn2O7?0.5CH2Cl2: C, 53.15; H, 3.85%). [Mn(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4CF3- p]}] 8. A solution of LiBun (0.38 mmol) in ether (10 cm3) was added dropwise to a solution of p-CF3C6H4Br (86 mg, 0.38 mmol) in ether (20 cm3). After 30 min of stirring at room temperature the resulting ether solution of LiC6H4CF3-p 24 was treated with compound 1 (80 mg, 0.19 mmol) in ether (40 cm3) at 260 to 240 8C for 4 h.Subsequent alkylation as above afforded 60 mg (53%, based on 1) of orange-red crystalline 8 which is a viscous oil at room temperature. Mass spectrum: m/z 594 (M+), 538 (M+ 2 2CO), 494 (M+ 2 2CO 2 OC2H4), 466 (M+ 2 3CO 2 OC2H4), 454 (M+ 2 5CO), 438 (M+ 2 4CO 2 OC2H4), 410 (M+ 2 5CO 2 OC2H5), 398 [M+ 2 Mn- (CO)3 ] 2CO], 258 [MnCH(OC2H5)C6H4CF3]+, 251 (MnC5H4- C6H6Mn)+ and 203 [(CF3C6H4)CH(OC2H5)]+ (Found: C, 52.8; H, 2.65.Calc. for C26H19F3Mn2O6: C, 52.55; H, 3.2%). [WMe(CO)3[Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4Meo]}] 9. To a solution of compound 2 (200 mg, 0.36 mmol) in ether (50 cm3) at 270 8C was added dropwise LiC6H4Me-o (0.78 mmol) in ether (10 cm3) with stirring. The orange-yellow solution was stirred initially at 270 to 265 8C for 0.5 h and then at 265 to 250 8C for 4 h, during which time it turned orange-red to red.The resulting solution was evaporated under vacuum at 250 to 240 8C to dryness. Subsequent alkylation of the residue obtained with Et3OBF4 and further treatment as described above gave 65 mg (26%, based on 2) of orange-yellow crystals of 9 which is a viscous oil at room temperature. Mass spectrum: m/z 628 (M+ 2 2CO), 584 (M+ 2 3CO 2 CH3 2 H), 556 (M+ 2 4CO 2 CH3 2 H), 528 (M+ 2 5CO 2 CH3 2 H), 480 [CH3(OC)3WC5H4C6H6Mn]+, 464 [(OC)3WC5H4C6H5Mn]+, 380 (WC5H4C6H5Mn)+, 204 [MnCH(OC2H5)C6H4CH3]+, 196 (C5H4C6H5Mn)+ and [(CH3C6H4)CH(OC2H5)]+ (Found: C, 43.7; H, 3.33.Calc. for C27H25MnO6W?CH2Cl2: C, 43.7; H, 3.55%). [WMe(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4Mem]}] 10. Similarly, compound 2 (100 mg, 0.18 mmol) wasJ. Chem. Soc., Dalton Trans., 1997, Pages 205–211 207 allowed to react with LiC6H4Me-m (0.39 mmol) at 265 to 250 8C for 4 h. Subsequent alkylation and further treatment as above afforded 35 mg (29%, based on 2) of 10 as orange-red crystals, m.p. 127–128 8C (decomp.). Mass spectrum: m/z 656 (M+ 2 CO), 600 (M+ 2 3CO), 480 [CH3(OC)3WC5H4C6H6- Mn]+, 464 [(OC)3WC5H4C6H5Mn]+, 380 (WC5H4C6H5Mn)+, 204 [MnCH(OC2H5)C6H4CH3]+, 196 (C5H4C6H5Mn)+ and 149 [(CH3C6H4)CH(OC2H5)]+. [WMe(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4Mep]}] 11. Similarly, compound 2 (200 mg, 0.36 mmol) dissolved in ether (50 cm3) was treated with LiC6H4Me-p (0.76 mmol) at 265 to 250 8C for 4 h, followed by alkylation; further treatment as described above yielded 70 mg (29%, based on 2) of orange-red crystalline 11 which is a red viscous oil at room temperature.Mass spectrum: m/z 628 (M+ 2 2CO), 584 (M+ 2 3CO 2 CH3 2 H), 556 (M+ 2 4CO 2 CH3 2 H), 528 (M+ 2 5CO 2 CH3 2 H), 480 [CH3(OC)3WC5H4C6H6Mn]+, 464 [(OC)3WC5H4C6H5Mn]+, 380 (WC5H4C6H5Mn)+, 204 [Mn- CH(OC2H5)C6H4CH3]+, 196 (C5H4C6H5Mn)+, 149 [(CH3C6H4)- CH(OC2H5)]+ (Found: C, 45.6; H, 3.15. Calc. for C27H25Mn- O6W?0.5CH2Cl2: C, 45.45; H, 3.15%). [WMe(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)Ph]}] 12.The reaction of compound 2 (100 mg, 0.18 mmol) with LiPh (0.39 mmol) was carried out as described above at 265 to 250 8C for 4 h. After evaporation of the solvent in vacuo, further treatment of the resulting residue as described above gave 48 mg (40%, based on 2) of orange-red crystals of 12, m.p. 81– 83 8C (decomp.). Mass spectrum: m/z 614 (M+ 2 2CO), 570 (M+ 2 3CO 2 CH3 2 H), 480 [CH3(OC)3WC5H4C6H6Mn]+, 464 [(OC)3WC5H4C6H5Mn]+, 380 (WC5H4C6H5Mn)+, 196 (C5H4C6H5Mn)+, 190 [MnCH(OC2H5)C6H5]+ and 135 [(C6H5)- CH(OC2H5)]+ (Found: C, 46.25; H, 3.6.Calc. for C26H23- MnO6W: C, 46.6; H, 3.45%). [WMe(CO)3{Á5-C5H4[Á5-C6H6)(OC)2Mn]] C(OEt)C6H4OMep]}] 13. Compound 2 (120 mg, 0.22 mmol) was treated as described above, with fresh LiC6H4OMe-p prepared by the reaction of p-MeOC6H4Br (90 mg, 0.48 mmol) with LiBun (0.48 mmol), in ether solution (50 cm3) at 265 to 250 8C for 4 h. Subsequent alkylation and further treatment yielded 44 mg (30%, based on 2) of orange-red crystals of 13 which is a viscous oil at room temperature.Mass spectrum: m/z 644 (M+ 2 2CO), 602 (M+ 2 3CO 2 CH3 2 H), 572 (M+ 2 4CO 2 CH3 2 H), 544 (M+ 2 5CO 2 CH3 2 H), 480 [CH3(OC)3- WC5H4C6H6Mn]+, 464 [(OC)3WC5H4C6H5Mn]+, 380 (WC5H4- C6H5Mn)+, 220 [MnCH(OC2H5)C6H4OCH3]+, 196 (C5H4C6H5- Mn)+ and [(CH3OC6H4)CH(OC2H5)]+ (Found: C, 46.8; H, 3.4. Calc. for C27H25MnO7W: C, 46.3; H, 3.6%). [WMe(CO)3{Á5-C5H4[(Á5-C6H6)(OC)2Mn]] C(OEt)C6H4CF3- p]}] 14.Similarly compound 2 (100 mg, 0.18 mmol) was treated with fresh LiC6H4CF3-p prepared by the reaction of p-CF3C6H4Br (90 mg, 0.40 mmol) with LiBun (0.40 mmol) in ether solution (50 cm3) at 265 to 250 8C for 4 h. Subsequent alkylation and further treatment as described above yielded 65 mg (45%, based on 2) of 14 as orange-red crystals, m.p. 70– 72 8C (decomp.). Mass spectrum: m/z 682 (M+ 2 2CO), 638 (M+ 2 3CO 2 CH3 2 H), 480 [CH3(OC)3WC5H4C6H6Mn]+, 464 [(OC)3WC5H4C6H5Mn]+, 380 (WC5H4C6H5Mn)+, 258 [MnCH(OC2H5)C6H4CF3]+, 203 [(CF3C6H4)CH(OC2H5)]+ and 196 (C5H4C6H5Mn)+ (Found: C, 41.1; H, 2.75.Calc. for C27H22F3MnO6W?CH2Cl2: C, 40.85; H, 2.95%). [(OC)3Mn{(Á5-C6H6)(Á5-C5H4)Fe(Á5-C5H4)(Á5-C6H6)}Mn- (CO)2{]] C(OEt)C6H4Me-o}] 16. The compound [(OC)3Mn{(h5- C6H6)(h5-C5H4)Fe(h5-C5H4)(h5-C6H6)}Mn(CO)3] 15 18 (100 mg, 0.16 mmol) was dissolved in ether (30 cm3) at 270 8C. To this solution was added dropwise LiC6H4Me-o (0.33 mmol) with stirring. The light yellow solution was stirred initially at 270 to 255 8C for 0.5 h and then at 255 to 235 8C for 4 h, during which time it turned yellow and a yellow precipitate separated.After evaporation of the solution to dryness in vacuo, the residue was subsequently alkylated with Et3OBF4 and further treated as described above to give 50 mg (44%, based on 15) of yellow crystals of 16, m.p. 42–44 8C (decomp.). Mass spectrum: m/z 682 (M+ 2 2CO), 626 (M+ 2 4CO), 618 (M+ 2 C2H5 2 CH3C6H4), 534 (M+ 2 3CO 2 C2H5 2 CH3C6H4), 450 [(MnC6- H6C5H4)2Fe]+, 395 [Mn(C6H6C5H4)2Fe]+, 338 [(C6H5C5H4)2Fe]+, 196 (MnC6H5C5H4)+ and 149 [(CH3C6H4)CH(OC2H5)]+ (Found: C, 59.75; H, 4.3.Calc. for C37H32FeMn2O: C, 60.2; H, 4.35%). [(OC)3Mn{(Á5-C6H6)(Á5-C5H4)Fe(Á5-C5H4)(Á5-C6H6)}Mn- (CO)2{=C(OEt)C6H4Me-p}] 17. Similarly, compound 15 (200 mg, 0.32 mmol) dissolved in ether (40 cm3) was treated with LiC6H4Me-p (0.65 mmol) at 255 to 235 8C for 4 h. Subsequent alkylation and further treatment as described above afforded 70 mg (31%, based on 15) of orange crystalline 17, m.p. 68–70 8C (decomp.). Mass spectrum: m/z 682 (M+ 2 2CO), 638 (M+ 2 2CO 2 OC2H4), 626 (M+ 2 4CO), 618 (M+ 2 C2H5 2 CH3C6H4), 588 (M+ 2 COC2H5 2 CH3C6H4 2 2H), 534 (M+ 2 3CO 2 C2H5 2 CH3C6H4), 450 [(MnC6H6C5H4)2Fe]+, 395 [Mn- (C6H6C5H4)2Fe]+, 338 [(C6H5C5H4)2Fe]+, 252 [MnC6H5C5- H4Fe]+, 196 (MnC6H5C5H4)+ and 149 [(CH3C6H4)CH- (OC2H5)]+ (Found: C, 60.35; H, 4.25. Calc. for C37H32FeMn2- O6: C, 60.2; H, 4.35%).Crystallography Single crystals of complex 3 suitable for X-ray diffraction study were obtained by recrystallization from light petroleum– CH2Cl2 solution at 280 8C. A crystal of approximate dimensions 0.20 × 0.20 × 0.40 mm was sealed in a capillary under a nitrogen atmosphere. Intensity data for 4152 independent reflections, of which 2516 had I > 3s(I), were collected with a Rigaku AFC7R diffractometer at 20 8C using Mo-Ka radiation (l 0.710 69 Å) with w–2q scan mode in the range 5 < 2q < 508.The intensity data were corrected for Lorentz-polarization effects and an empirical absorption correction based on azimuthal scans of several reflections was applied which resulted in transmission factors ranging from 0.636 to 1.000. The structure was solved and expanded by Fourier techniques. The non-hydrogen atoms were refined anisotropically. The hydrogen atoms were included but not refined. The final cycle of full-matrix least-squares refinement was based on 2516 observed reflections and 308 variable parameters and converged (largest parameter was 0.06 times its e.s.d.).The standard deviation of an observation of unit weight was 1.74. The weighting scheme was based on counting statistics and included a factor (p = 0.030) to downweight the intense reflections. The maximum and minimum peaks on the final Fourier-difference map corresponded to 0.45 and 20.53 e Å23, respectively. All calculations were performed using the TEXSAN crystallographic software package.25 Details of the crystallographic data and the procedures used for data collection and reduction are given in Table 3.Atomic coordinates, thermal parameters, and bond lengths and angles have been deposited at the Cambridge Crystallographic Data Centre (CCDC). See Instructions for Authors, J. Chem. Soc., Dalton Trans., 1997, Issue 1. Any request to the CCDC for this material should quote the full literature citation and the reference number 186/288. Results and Discussion Compound 1 was treated with 2 molar equivalents of aryllithium reagents LiR (R = o-, m-, p-MeC6H4, Ph, p-MeOC6H4 or p-CF3C6H4) in ether at 265 to 245 8C for 4 h.The acylmetalate intermediates formed were subsequently alkylated208 J. Chem. Soc., Dalton Trans., 1997, Pages 205–211 with Et3OBF4 in aqueous solution at 0 8C. After removal of the solvent under high vacuum at low temperature, chromatography of the solid residue on an alumina column at 220 8C, and recrystallization from light petroleum–CH2Cl2 solution at 280 8C, orange-red crystalline complexes 3–8 were obtained with the composition [(OC)3Mn{h5-C5H4[(h5-C6H6)(OC)2- Mn]] C(OEt)R]}] (Scheme 4) in 53–71% yields. The complexes are soluble in polar organic solvents but only slightly soluble in non-polar solvents.They are sensitive to air and temperature in solution but fairly stable in the crystalline state. They are formulated as cyclohexadienyl-co-ordinated manganese carbene complexes on the basis of their elemental analyses and spectroscopic studies and a single-crystal X-ray diffraction study of 3.There are two olefin-co-ordinated Mn(CO)3 units in complex 1. However, neither dicarbene complexes nor cyclopentadienylco- ordinated carbene complexes were obtained in the reactions, only products 3–8, even though more than 2 molar equivalents of aryllithium reagents were used. This might be ascribed to the different carbonyls of the two kinds of Mn(CO)3 in 1.To compare the reactivity, we treated [Mn(h5-C5H5)(CO)3] 26 with aryllithium reagents at 0–5 8C to afford the same manganese carbene complexes as reported.27 It was also reported by Sheridan et al.28 that tricarbonyl(h5-cyclohexadienyl)manganese reacted with aryllithium at 250 8C to produce the manganese carbene complex. The difference between the temperatures at which tricarbonyl(h5-cyclopentadienyl)- and Scheme 4 (i) 2LiR, Et2O, 265 to 245 8C; (ii) Et3OBF4, water, 0 8C Mn CO OC CO M CO OC n C O–Li+ R 1 D6/04436K/A4 (OC)3Mn (OC)3Mn M CO OC (ii ) (i ) (OC)3Mn n C OEt R a b c d e f f e b c 3 o –MeC6H4 4 m–MeC6H4 5 p –MeC6H4 6 Ph 7 p –MeOC6H4 8 p –CF3C6H4 R Table 1 Infrared specta of complexes 1–17 in hexane in the n(CO) region Complex n& (CO)/cm21 1 18 2 18 3456789 10 11 12 13 14 15 18 16 17 2020s, 1960s, 1954s 2020s, 1994w, 1966s, 1958s, 1940w, 1935s 2000s, 1961s, 1947s, 1908m 2000s, 1957s, 1943s, 1900m 2002s, 1960s, 1948s, 1900m 2001s. 1958s, 1950s, 1902m 2002s, 1961s, 1952s, 1900m 2000s, 1960s, 1945s, 1910m 2010s, 1964s, 1953m, 1932vs, 1910w 2000s, 1960s, 1953s, 1931vs, 1900w 2000s, 1960s, 1953s, 1932vs, 1900w 2000s, 1960s, 1956m, 1934vs, 1905s 2000s, 1960s, 1955s, 1932vs, 1900m 2000s, 1962s, 1954s, 1933vs, 1911w 2000s, 1950vs 2025s, 1959vs, 1950s, 1905m 2020s, 1957vs, 1950s, 1898m tricarbonyl(h5-cyclohexadienyl)-manganese react with the aryllithiums shows that the reactivities of the two kinds of olefinco- ordinated Mn(CO)3 in 1 are different.However, when 1 was treated with aryllithium reagents either at 0–5 8C or while the temperature was allowed to rise slowly from 265 to 0–5 8C only cyclohexadienyl-co-ordinated products 3–8 were obtained, not the expected cyclopentadienyl-co-ordinated manganese carbene complexes. The carbene formation at the less-electron-rich centre is predictable because cyclopentadienyl is a better donor than cyclohexadienyl. The IR spectra (Table 1) and the solution 1H NMR spectra (Table 2), as well as the mass spectra, of complexes 3–8 are consistent with the proposed structure. In the 1H NMR spectra resonances at d 5.20–3.30 and 1.60–1.40 are attributed to the ethoxy group and at d 7.80–6.80 to the aryl group, in addition to the expected proton signals of the cyclopentadienyl and cyclohexadienyl groups. As compared with the starting material 1, the chemical shift of Ha moved upfield and that of Hd changed a little, while use of Hb and Hc remained almost constant in 3–8, indicating that the extent of back donation of d electrons from Mn to the p* orbital of the co-ordinated cyclohexadienyl increased only a little, upon formation of the carbene ligand.The difference between the chemical shifts of the cyclohexadienyl protons might be ascribed to the different distant shielding from the p electrons of the Ha, Hb, Hc and Hd protons, as shown for tricarbonyl(h5-cyclohexadienyl)- manganese by Winkhaus et al.29 The structural data for 3 show that Ha lies in the shielding area of the aryl ring.So we prefer to consider that the greatest influence on d(Ha) comes from the shielding of the aryl ring. In contrast to the singlet signal of complex 1, all of the signals of the cyclopentadienyl protons in 3–8 split into doublet and triplet or multiplet peaks, indicating that the carbene ligand not only influences the extent of donation of d electrons from Mn to the cyclohexadienyl moiety but also changes the chemical environment of the C5H4 ring.The mass spectra of complexes 3–8 (Experimental section) showed, besides their molecular ions, the principal fragments produced by successive loss of CO ligands and peaks generated by further cleavage of these principal fragments. The most important is [C5H4C6H5Mn]] CHR]+, which is characteristic of the combination of carbene ligands with manganese. The molecular structure of complex 3 is shown in Fig. 1. The X-ray study confirmed the assigned structure and has many common features with previously determined carbene complex structures.17,30 The Mn(1)]C(12) distance is 1.885(6) Å, which signifies a high double-bond character, and is the same within experimental error as that in the analogous carbene complexes [Mn(h5-C5H5)(h5-C6H6)(CO)2{]] C(OEt)Ph}] [1.89(1) Å] 17 and [Mn(h5-C5H5)(h5-C6H6)(CO)2{]] C(OEt)C6H4Me-o}] [1.881(4) Å],17 but slightly longer than that in [Mn(h5-C5H5)(CO)2- {C(OEt)Ph}] [1.865(4) Å].30 The C(12)]O(1) bond length of 1.354(7) Å is the same within experimental error as that of the corresponding C]O bond in [Mn(h5-C5H5)(CO)2{C(OEt)Ph}] [1.356(17) Å] 30 and comparable with that in [Mn(h5-C5H5)(h5- C6H6)(CO)2{]] C(OEt)Ph}] [1.34(1) Å] 17 and [Mn(h5-C5H5)(h5- C6H6)(CO)2{]] C(OEt)C6H4Me-o}] [1.337(4) Å].17 Unusual features are the O(1)]C(20) [1.484(9) Å] and the C(20)]C(21) [1.44(1) Å] bond lengths of the OEt group; the former is much longer than that of a normal C]O distance and the latter is between normal C]C and C]] C distances, both of them being obviously different from that of OEt in analogous carbene complexes.For example, the corresponding O]C and C]C distances are 1.46(1) and 1.54(2) Å in [Mn(h5-C5H5)(h5-C6H6)- (CO)2{]] C(OEt)Ph}], and 1.471(17) and 1.507(21) Å in [Mn(h5- C5H5)(CO)2{C(OEt)Ph}]. It is proposed that the fairly strong electron donation from O(1) to the carbene carbon weakens the bonding between O(1) and C(20), leading to a lengthening of the bond distance and a lowering of the electron density around C(20).To compensate, part of the electron cloud around C(21)J. Chem. Soc., Dalton Trans., 1997, Pages 205–211 209 Table 2 Proton NMR spectra of complexes 1–17 in (CD3)2CO at 20 8C* Complex d(C5H4C6H6) d(aryl) d(OEt) d(Me) 1 18 2 18 3 4 5 6 7 8 9 10 11 12 13 14 15 18 16 17 6.07 (t, 1 H), 5.20 (t, 2 H), 4.75 (s, 4 H), 3.51 (t, 2 H), 3.38 (t, 1 H) 6.07 (t, 1 H), 5.45 (t, 2 H), 5.30 (t, 2 H), 5.21 (t, 2 H), 3.45 (m, 3 H) 5.68 (t, 1 H), 5.20 (t, 2 H), 4.68 (m, 4 H), 3.21 (m, 3 H) 5.65 (t, 1 H), 5.19 (t, 2 H), 4.75 (t, 2 H), 4.69 (d, 2 H), 3.50 (t, 2 H), 3.30 (t, 1 H) 5.65 (t, 1 H), 5.20 (t, 2 H), 4.76 (t, 2 H), 4.70 (d, 2 H), 3.52 (t, 2 H), 3.34 (m, 1 H) 5.68 (t, 1 H), 5.20 (t, 2 H), 4.76 (t, 2 H), 4.69 (q, 2 H), 3.51 (t, 2 H), 3.33 (t, 1 H) 5.67 (t, 1 H), 5.20 (t, 2 H), 4.76 (t, 2 H), 4.70 (d, 2 H), 3.53 (t, 2 H), 3.12 (t, 1 H) 5.74 (t, 1 H), 5.19 (t, 2 H), 4.83 (t, 2 H), 4.74 (d, 2 H), 3.51 (t, 2 H), 3.25 (t, 1 H) 5.68 (t, 1 H), 5.45 (d, 1 H), 5.40 (d, 1 H), 5.30 (d, 2 H), 5.24 (d, 2 H), 3.45 (m, 3 H) 5.67–5.61 (m, 1 H), 5.45 (t, 1 H), 5.40 (t, 1 H), 5.30 (t, 2 H), 5.21 (m, 2 H), 3.45 (t, 2 H), 3.37 (t, 1 H) 5.67 (t, 1 H), 5.45 (t, 1 H), 5.40 (t, 1 H), 5.30 (t, 1 H), 5.24 (t, 1 H), 5.20 (d, 2 H), 3.46 (t, 2 H), 3.39 (t, 1 H) 5.68 (t, 1 H), 5.45 (d, 1 H), 5.39 (d, 1 H), 5.30 (t, 1 H), 5.23 (d, 1 H), 5.21 (d, 2 H), 3.45 (t, 2 H), 3.38 (t, 1 H) 5.69 (t, 1 H), 5.46 (t, 1 H), 5.40 (t, 1 H), 5.30 (t, 2 H), 5.22 (m, 2 H), 3.46 (m, 2 H), 3.08 (t, 1 H) 5.72 (t, 1 H), 5.43 (t, 1 H), 5.39 (t, 1 H), 5.28 (t, 1 H), 5.23 (t, 1 H), 5.18 (d, 2 H), 3.43 (t, 2 H), 3.36 (t, 1 H) 5.74 (t, 2 H), 4.85 (t, 4 H), 3.94 (t, 4 H), 3.75 (t, 4 H), 3.33 (m, 6 H) 5.99 (m, 1 H), 5.60 (t, 1 H), 5.08 (m, 2 H), 4.56 (m, 2 H), 4.02 (t, 2 H), 3.95 (t, 2 H), 3.89 (t, 2 H), 3.83 (t, 2 H), 3.40 (q, 3 H), 3.19 (t, 3 H) 5.97 (t, 1 H), 5.57 (t, 1 H), 5.09 (m, 2 H), 4.65 (t, 2 H), 4.02 (t, 2 H), 3.95 (t, 2 H), 3.89 (t, 2 H), 3.83 (q, 2 H), 3.41 (t, 3 H), 3.23 (t, 3 H) 7.18 (m, 3 H), 6.84 (m, 1 H), 3.30 (s, 3 H) 7.36–7.09 (m, 4 H), 2.34 (s, 3 H) 7.36 (m, 2 H), 7.16 (m, 2 H), 2.33 (s, 3 H) 7.36 (m, 5 H) 7.70 (d, 2 H), 6.93 (d, 2 H), 3.84 (s, 3 H) 7.71 (d, 2 H), 7.40 (d, 2 H) 7.25–7.13 (m, 3 H), 6.84 (m, 1 H), 3.28 (s, 3 H) 7.26–7.09 (m, 4 H), 2.36 (s, 3 H) 7.36 (m, 2 H), 7.19 (m, 2 H), 2.35 (s, 3 H) 7.34 (m, 5 H) 7.69 (d, 2 H), 6.92 (d, 2 H), 3.86 (s, 3 H) 7.69 (d, 2 H), 7.38 (d, 2 H) 7.36–7.12 (m, 3 H), 6.86 (m, 1 H), 2.32 (s, 3 H) 7.36 (m, 2 H), 7.19 (m, 2 H), 2.36 (s, 3 H) 4.53 (q, 2 H), 1.43 (t, 3 H) 5.03 (q, 2 H), 1.53 (t, 3 H) 5.13 (q, 2 H), 1.56 (t, 3 H) 5.08 (q, 2 H), 1.57 (t, 3 H) 3.37 (q, 3 H), 1.60 (t, 3 H) 5.08 (q, 2 H), 1.57 (t, 3 H) 4.52 (q, 2 H), 1.43 (t, 3 H) 5.04 (q, 2 H), 1.55 (t, 3 H) 5.12 (q, 2 H), 1.58 (t, 3 H) 5.07 (q, 2 H), 1.57 (t, 3 H) 4.78 (q, 2 H), 1.60 (t, 3 H) 5.05 (q, 2 H), 1.55 (t, 3 H) 3.60 (q, 2 H), 1.44 (t, 3 H) 3.60 (q, 2 H), 1.58 (t, 3 H) 0.36 (s, 3 H) 0.33 (s, 3 H) 0.36 (s, 3 H) 0.34 (d, 3 H) 0.34 (d, 3 H) 0.35 (d, 3 H) 0.33 (d, 3 H) * Internal reference SiMe4.moves toward C(20) to form a partial double bond, C(20)] C(21). The carbene carbon C(12) lies essentially in the benzene ring plane (±0.0068 Å). The C5H4 ring plane is oriented at an angle Table 3 Crystal data and experimental details for complex 3 Empirical formula M Crystal symmetry Space group a/Å b/Å c/Å a/8 b/8 g/8 U/Å3 Z D/g cm23 m(Mo-Ka)/cm21 Orientation reflections, 2q range/8 Data collection range, 2q/8 No.unique data, total with I > 3.00s(I), No No. of parameters refined, Np Ra R9 b Goodness of fit c Maximum shift/error in final cycle C26H22Mn2O6 540.33 Triclinic P1� (no. 2) 12.018(4) 12.415(3) 8.758(2) 106.71(2) 102.15(2) 71.56(2) 1177.0(6) 2 1.525 11.12 14, 23.5–26.4 2–50.0 4152 2516 308 0.047 0.054 1.74 0.06 a R = S||Fo| 2 |Fc||/S|Fo|.b R9 = [Sw(|Fo| 2 |Fc|)2/Sw|Fo|2]� �� ; w = 1/s2(|Fo|). c [Sw(|Fo| 2 |Fc|)2/(No 2 Np)]� �� . of 84.878 with respect to the h5-dienyl plane, thus the C5H4 ring and h5-dienyl ring planes are almost perpendicular to each other. The angle between the benzene ring and the C5H4 ring planes is 80.098, thus these planes are also nearly perpendicular to each other. The angle between the benzene ring and the h5- dienyl C(7)–C(11) plane of 10.548 shows that the benzene ring plane is nearly parallel to the h5-dienyl ring plane.The preparation of complexes 9–14 is similar to that of 3–8. Compound 2 was treated with 2 molar equivalents of aryllithium reagents. LiR (R = o-, m-, p-MeC6H4, Ph, p-MeOC6H4 or p-CF3C6H4) in ether at 265 to 250 8C for 4 h. After work-up the orange-red crystalline complexes 9–14 with compositions [WMe(CO)3{h5-C5H4[(h5-C6H6)(OC)2Mn]] C(OEt)R}] (Scheme 5) were isolated in 26–45% yields.The complexes have similar properties to those of 3–8. They are formulated as cyclohexadienyl- co-ordinated manganese carbene complexes on the basis of their elemental analyses and spectroscopic studies. There are two different M(CO)3 units in 2, however no manganese–tungsten dicarbene complexes or cyclopentadienylco- ordinated tungsten carbene complexes were obtained even though more than 2 molar equivalents of aryllithiums were used.The complexes 9–14 showed 1H NMR spectral data consistent with the assigned structures (see Table 2). Compared with 2, the cyclohexadienyl signals had greatly changed. The chemical shift of Ha moved upfield and the signal of Hb split into two triplet bands. Whereas a multiplet occurred for 2, the signals of Hc and Hd were two triplets for 9–14. As for the C5H4 ring, there is not much difference in the signals from 2 and 9–14. In210 J. Chem. Soc., Dalton Trans., 1997, Pages 205–211 Table 4 Bond distances (Å) and angles (8) for complex 3 * Mn(1)]C(7) Mn(1)]C(9) Mn(1)]C(11) Mn(1)]C(22) Mn(2)]C(1) Mn(2)]C(3) Mn(2)]C(5) Mn(2)]C(25) O(1)]C(12) O(2)]C(22) O(4)]C(24) 2.231(6) 2.152(6) 2.244(5) 1.792(7) 2.142(6) 2.134(6) 2.147(5) 1.803(7) 1.354(7) 1.152(7) 1.148(8) Mn(1)]C(8) Mn(1)]C(10) Mn(1)]C(12) Mn(1)]C(23) Mn(2)]C(2) Mn(2)]C(4) Mn(2)]C(24) Mn(2)]C(26) O(1)]C(20) O(3)]C(23) O(5)]C(25) 2.158(6) 2.147(6) 1.885(6) 1.803(7) 2.139(6) 2.153(5) 1.779(9) 1.798(7) 1.484(9) 1.140(7) 1.134(7) O(6)]C(26) C(1)]C(5) C(3)]C(4) C(4)]C(6) C(6)]C(11) C(8)]C(9) C(10)]C(11) C(13)]C(14) C(14)]C(15) C(16)]C(17) C(18)]C(19) 1.145(7) 1.411(8) 1.407(7) 1.522(7) 1.520(8) 1.399(9) 1.380(8) 1.401(8) 1.387(9) 1.358(10) 1.494(9) C(1)]C(2) C(2)]C(3) C(4)]C(5) C(6)]C(7) C(7)]C(8) C(9)]C(10) C(12)]C(13) C(13)]C(18) C(15)]C(16) C(17)]C(18) C(20)]C(21) 1.418(9) 1.409(9) 1.417(8) 1.517(7) 1.409(8) 1.412(9) 1.501(8) 1.392(8) 1.395(10) 1.392(9) 1.44(1) C(4)]Mn(2)]C(25) C(5)]Mn(2)]C(24) C(5)]Mn(2)]C(26) C(24)]Mn(2)]C(26) C(12)]O(1)]C(20) C(1)]C(2)]C(3) C(3)]C(4)]C(6) CC(4)]C(6)]C(11) C(6)]C(7)]C(8) C(8)]C(9)]C(10) C(6)]C(11)]C(10) Mn(1)]C(12)]C(13) C(7)]Mn(1)]C(12) C(7)]Mn(1)]C(23) C(8)]Mn(1)]C(12) C(8)]Mn(1)]C(23) C(9)]Mn(1)]C(22) 152.1(3) 153.0(3) 97.1(3) 90.2(3) 122.8(5) 107.2(5) 124.2(5) 107.8(5) 111.3(5) 120.0(5) 116.8(5) 119.7(5) 123.8(4) 109.8(2) 86.0(3) 91.6(2) 122.3(3) 106.6(3) C(4)]Mn(2)]C(26) C(5)]Mn(2)]C(25) C(24)]Mn(2)]C(25) C(25)]Mn(2)]C(26) C(2)]C(1)]C(5) C(2)]C(3)]C(4) C(3)]C(4)]C(5) C(5)]C(4)]C(6) C(4)]C(6)]C(7) C(7)]C(6)]C(11) C(7)]C(8)]C(9) C(9)]C(10)]C(11) Mn(1)]C(12)]O(1) O(1)]C(12)]C(13) C(7)]Mn(1)]C(22) C(8)]Mn(1)]C(22) C(9)]Mn(1)]C(12) C(9)]Mn(1)]C(23) 95.8(2) 113.9(3) 91.5(3) 92.1(3) 108.4(6) 108.9(6) 107.7(5) 128.0(5) 117.0(5) 102.7(4) 120.3(5) 121.9(6) 132.5(4) 103.2(5) 166.2(2) 142.1(3) 102.0(2) 148.8(3) C(10)]Mn(1)]C(22) C(11)]Mn(1)]C(12) C(11)]Mn(1)]C(23) C(12)]Mn(1)]C(23) C(1)]Mn(2)]C(24) C(1)]Mn(2)]C(26) C(2)]Mn(2)]C(24) C(2)]Mn(2)]C(26) C(3)]Mn(2)]C(25) C(3)]Mn(2)]C(26) C(12)]C(13)]C(14) C(14)]C(13)]C(18) C(14)]C(15)]C(16) C(16)]C(17)]C(18) C(13)]C(18)]C(19) O(1)]C(20)]C(21) Mn(1)]C(23)]O(3) Mn(2)]C(25)]O(5) 90.1(2) 169.0(2) 86.7(2) 102.4(3) 139.7(3) 129.9(3) 102.3(3) 159.8(3) 140.9(3) 127.0(3) 118.4(5) 120.4(5) 119.0(6) 122.1(7) 121.3(6) 107.8(8) 173.8(6) 179.2(6) C(10)]Mn(1)]C(12) C(10)]Mn(1)]C(23) C(11)]Mn(1)]C(22) C(12)]Mn(1)]C(22) C(22)]Mn(1)]C(23) C(1)]Mn(2)]C(25) C(2)]Mn(2)]C(25) C(3)]Mn(2)]C(4) C(3)]Mn(2)]C(24) C(4)]Mn(2)]C(24) C(12)]C(13)]C(18) C(13)]C(14)]C(15) C(15)]C(16)]C(17) C(13)]C(18)]C(17) C(17)]C(18)]C(19) Mn(1)]C(22)]O(2) Mn(2)]C(24)]O(4) Mn(2)]C(26)]O(6) 135.3(2) 122.3(3) 102.3(2) 83.4(3) 95.3(3) 90.3(3) 103.3(3) 38.3(2) 90.5(3) 115.1(3) 121.0(5) 120.2(6) 120.3(6) 117.9(6) 120.7(6) 178.1(6) 178.1(7) 179.8(6) * Estimated standard deviations in the least significant figure are given in parentheses.addition, the chemical shift of the methyl protons attached to the W(CO)3 moiety is almost unchanged.It seems that the carbene ligand has much more influence on the chemical environment of the cyclohexadienyl than that of the cyclopentadienyl moiety, which suggests that the carbene ligand is attached to Mn instead of W. The mass spectra of complexes 9–14 showed no molecular ion peaks due to the difficulty of vaporization, but showed principal fragments produced by loss of CO and carbene ligands and peaks such as [MnCH(OEt)R]+ and [CH(OEt)R]+, which are characteristic of the carbene ligands.Fig. 1 Molecular structure of complex 3 showing the atom-labelling scheme and probability ellipsoids As mentioned above, the starting materials, 1 and 2, both have two different M(CO)3 (M = Mn or W) units co-ordinated to the different olefin ligands. Owing to the different reactivities of the carbonyls, only one kind of manganese carbene complex was obtained when treating 1 and 2 with aryllithium reagents.Thus, we chose [(OC)3Mn{(h5-C6H6)(h5-C5H4)Fe(h5- C5H4)(h5-C6H6)}Mn(CO)3] 15, in which the two Mn(CO)3 units have the same chemical environment, as starting material for the reaction under the same conditions. However, we did still not obtain the expected dicarbene complex. When compound 15 was treated with 2 molar equivalents of LiR (R = o- or p- MeC6H4) in ether at 255 to 235 8C for 4 h, followed by alkylation with Et3OBF4 in aqueous solution at 0 8C, work-up afforded orange-red crystalline complexes 16 and 17 (Scheme 6) in 44 and 31% yields.These complexes have properties similar Scheme 5 (i) 2LiR, Et2O, 265 to 250 8C; (ii) Et3OBF4, water, 0 8C Mn CO OC CO M CO OC n C O–Li+ R 2 D6/04436K/A6 (OC)3MeW (OC)3MeW M CO OC (ii ) (i ) (OC)3MeW n C OEt R a b c d e f f e b c 9 o –MeC6H4 10 m–MeC6H4 11 p –MeC6H4 12 Ph 13 p –MeOC6H4 14 p –CF3C6H4 RJ. Chem. Soc., Dalton Trans., 1997, Pages 205–211 211 to those of 3–8. They are formulated as cyclohexadienylco- ordinated manganese carbene complexes with only one carbene on the basis of their elemental analyses and spectroscopic studies.Similarly, even increasing the amount of the aryllithium reagents used gave no dicarbene manganese complexes. In the 1H NMR spectra of complexes 16 and 17, resonances at d 3.60 and 1.58–1.44 attributed to the ethoxy group and at d 7.36–6.86 assigned to the aryl group, in addition to the expected proton signals of the cyclopentadienyl and cyclohexadienyl groups, were observed. As compared with 15, the proton signals of the cyclohexadienyl ring of 16 and 17 changed greatly.In 15, Ha and Ha9 and Hb and Hb9 shared the same triplet signals, and the signals of Hc, Hc9 and Hd, Hd9 appeared as a multiplet. On the other hand, for 16 and 17, the signals of Ha, Ha9 and Hb, Hb9 all split into two multiplet or triplet bands, and the signals of Hc, Hc9 and Hd, Hd9 also appeared as a triplet or a quartet.As for the C5H4 rings, the proton signals appeared as two triplet bands for 15 but as four triplets for 16 and 17. The 1H NMR spectra showed that the chemical environments of the two cyclohexadienyl ligands in both complexes 16 and 17 are very different from that of 15, being characteristic of a complex with only one carbene ligand. The mass spectra of complexes 16 and 17 showed no molecular ions but the principal fragments produced by successive loss of CO ligands and peaks such as [Mn(C6H6C5H4)2Fe]+, [C6H5C5H4Fe]+, [MnC6H5C5H4]+ and [RCH(OC2H5)]+, all of which provided useful structure information.Scheme 6 (i) Et2O, 255 to 235 8C; (ii) Et3OBF4, water, 0 8C Mn CO OC CO Fe Mn CO OC CO Mn CO OC CO Fe M CO OC + n C 2LiR (i ) OEt R (ii ) D6/04436K/A7 a b c d e f f e b c a¢ b¢ c¢ d¢ e¢ f¢ f¢ e¢ b¢ c¢ 15 16 o –MeC6H4 17 p –MeC6H4 R Acknowledgements Financial support from the National Natural Science Foundation of China and the Science Foundation of the Chinese Academy of Sciences is gratefully acknowledged.References 1 J.-B. Chen, G.-X. Lei, W.-H. Xu, X.-L. Jin, M.-C. Shao and Y.-Q. Tang, J. Organomet. Chem., 1985, 286, 55. 2 J.-B. Chen, G.-X. Lei, W.-H. Xu, Z.-H. Pan, S.-W. Zhang, Z.-Y. Zhang, X.-L. Jin, M.-C. Shao and Y.-Q. Tang, Organmetallics, 1987, 6, 2461. 3 J.-B. Chen, G.-X. Lei, Z.-H. Pan, Z.-Y. Zhang and Y.-Q. Tang, J. Chem. Soc., Chem. Commun., 1987, 1273. 4 J.-B.Chen, G.-X. Lei, M.-C. Shao, X.-J. Xu and Z.-Y. Zhang, J. Chem. Soc., Chem. Commun., 1988, 1296. 5 J.-B. Chen, J.-G. Yin, Z.-C. Fan and W.-H. Xu, J. Chem. Soc., Dalton Trans., 1988, 2083. 6 J.-B. Chen, J.-G. Yin, G.-X. Lei, W.-H. Xu, M.-C. Shao, Z.-Y. Zhang and Y.-Q. Tang, J. Organomet. Chem., 1987, 329, 69. 7 J.-B. Chen, J.-G. Yin, G.-X. Lei, Y. Y. Wang and G.-D. Lin, J. Chem. Soc., Dalton Trans., 1989, 635. 8 J.-B. Chen, J.-G. Yin, W.-H. Xu, L.-H. Lai, Z.-Y. Zhang and M.-C. Shao, Organometallics, 1987, 6, 2607. 9 J.-G. Yin, J.-B. Chen, W.-H. Xu, Z.-Y. Zhang and Y.-Q. Tang, Organometallics, 1988, 7, 21. 10 J.-B. Chen, G.-X. Lei, Z.-S. Jin, L.-H. Hu and G.-C. Wei, Organometallics, 1988, 7, 1652. 11 J.-B. Chen, G.-X. Lei, Z.-Y. Zhang and Y.-Q. Tang, Sci. China, Ser. B, 1989, 32, 129. 12 Y. Yu, J.-B. Chen, J. Chen and P.-J. Zheng, Organometallics, 1993, 12, 4731. 13 J.-B. Chen, D.-S. Li, Y. Yu, Z.-S. Jin, Q.-L. Zhou and G.-C. Wei, Organometallics, 1993, 12, 3885. 14 J.-B. Chen and B.-H. Wang, J. 0rganomet. Chem., 1992, 440, 67. 15 J.-B. Chen, Y. Yu, L.-H. Hu and Z.-S. Jin, J. Organomet. Chem., 1993, 447, 113. 16 J.-B. Chen, D.-S. Li, Y. Yu and C.-G. Chen, Organometallics, 1994, 13, 3581. 17 Y. Yu, J.-B. Chen, X.-Y. Wang, Q.-J. Wu and Q.-T. Liu, J. Organomet. Chem., 1996, 516, 81. 18 T.-M. Chung and Y.-K. Chung, Organometallics, 1992, 11, 2822. 19 H. Meerwein, G. Hinze, P. Hofmann, E. Kroniny and E. Pfeil, J. Prakt. Chem., 1937, 147, 257. 20 H. Gilman, E. A. Zoellner and W. M. Selby, J. Am. Chem. Soc., 1933, 55, 1252. 21 G. Wittig, Angew. Chem., 1940, 53, 243. 22 R. G. Jones and H. Gilman, Org. React., 1951, 6, 352. 23 E. O. Fischer, C. G. Kreiter, H. J. Kollmeier, J. Muller and R. D. Fischer, J. Organomet. Chem., 1971, 28, 237. 24 E. O. Fischer, J.-B. Chen and U. Schubert, Z. Naturforsch., Teil B, 1982, 37, 1284. 25 TEXSAN, Structure Analysis Package, Molecular Structure Corporation, Houston, TX, 1985. 26 T. S. Piper, F. A. Cotton and G. Wilkinson, J. Inorg. Nucl. Chem., 1955, 1, 165. 27 E. O. Fischer, E. W. Meineke and F. R. Kreissel, Chem. Ber., 1977, 110, 1140. 28 J. B. Sheridan, R. S. Padda, K. Chaffee, C. J. Wang, Y. Z. Huang and R. Lalancette, J. Chem. Soc., Dalton Trans., 1992, 1539. 29 G. Winkhaus, L. Partt and G. Wilkinson, J. Chem. Soc., 1961, 3807. 30 U. Schubert, Organometallics, 1982, 1, 1085. Received 25th June 1996; Paper 6/04436K

ISSN:1477-9226    

DOI:10.1039/a604436k

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, Pages 207–213 207 Tuning the metal–metal separation in pyrazolate-based dinuclear complexes by the length of chelating side arms‡ Franc Meyer,*,† Katja Heinze, Bernhard Nuber and Laszlo Zsolnai Anorganisch-Chemisches Institut der Universität Heidelberg, Im Neuenheimer Feld 270, D-69120 Heidelberg, Germany Six dinuclear cobalt(II) complexes of pyrazolate ligands with multidentate chelating side arms {3,5-(R2NCH2)2C3N2H2; R2N = [Me2N(CH2)3]2N (HL1) or (Et2NCH2CH2)2N (HL2)} have been prepared and characterised.The reaction of L1 and L2 with 2 equivalents of [Co(MeCN)6][BF4]2 and NaBPh4 proceeds via the isolable compounds [Co2L1(BF4)][BPh4]2 1a and [Co2L2(BF4)][BPh4]2 2a finally to afford the dinuclear complexes [Co2L1F][BPh4]2 1b and [Co2L2(F)(H2O)][BPh4]2 2b, respectively, where a fluoride has been abstracted from the BF4 2 starting material in both cases. While the longer side arms in 1b allow for an exogenous bridging position of the fluoride, an additional water molecule is incorporated in 2b to form an FHO(H) moiety with an unusually short F]H]O bridge between the two cobalt centres.Evidence is reported for the reversible extrusion of the water molecule from 2b. Treatment of 2b with KBr or NaN3 yielded the respective bromide- and azide-bridged complexes 3 and 4, where in the latter case the azide adopts a m-1,3-bridging mode. The magnetic properties of 3 and 4 have been studied in the temperature range 8–200 K.Complexes 1b, 2b, 3 and 4 were also characterised by means of X-ray crystallography. Stimulated by the occurrence of bi- and multi-metallic centres in the active sites of various metalloenzymes, there is considerable current interest in transition-metal complexes containing several metal ions in close proximity.1 In order to control possible co-operative phenomena between the two metal centres the design of appropriate ligand cores providing co-ordination sites with well defined metal–metal separations is highly desirable. 2 Many of the dinucleating ligand systems reported are derived from bridging phenoxide or alkoxide moieties containing additional chelating donors, in which a single oxygen centre spans the two metal ions in a dinuclear arrangement.3 These monoatomic bridges generally support metal–metal separations in the range 2.5–3.8 Å. Larger separations are accessible by using diatomic bridges and should be adjustable by means of additional chelating side arms connected with the bridging framework.The ability of the 1,2-diazole unit of pyrazolates to bridge two metal ions is well documented.4 However, relatively few studies of dinuclear complexes of pyrazolate-based ligands possessing additional chelating substituents in the 3 and 5 positions of the heterocycle have been reported until now.5–9 Recently we reported a series of dinuclear cobalt(II) complexes A of pyrazolate ligands providing multidentate nitrogen donors within side arms of varying chain lengths.9a Force-field calculations showed that the two tran-type co-ordination subunits [tran = tris(aminoalkyl)- amine] of these bimetallic systems are largely decoupled with respect to their accessible conformational space, which should allow the adaptation to different secondary bridges X.However, those complexes studied previously all contain chloride ions as secondary bridging ligands,9a which thus determined the effective Co ? ? ? Co distances and caused the latter to be very similar irrespective of the chain lengths of the substituents at the pyrazolate.Based on the same basic structural motif the present work describes the adjustment of different metal–metal separations and hence the preference for matching secondary anions X in this type of system, induced by the different lengths of the donor side arms. † E-Mail: franc@sun0.urz.uni-heidelberg.de ‡ Non-SI units employed: bar = 105 Pa, mB ª 9.27 × 10224 J T21.Results and Discussion In an attempt to introduce a weakly co-ordinating anion as the secondary bridge X in complexes of type A, the deprotonated pyrazolate derivative L1 was treated with 2 equivalents of [Co(MeCN)6][BF4]2 in acetonitrile, immediately yielding a deep purple solution. Anion exchange with 2 equivalents of NaBPh4 and subsequent addition of diethyl ether caused precipitation of a purple solid, which after its isolation gave analytical data in accord with the sought composition [Co2L1(BF4)][BPh4]2 1a.Attempts to crystallise 1a by vapour diffusion of diethyl ether into an acetonitrile solution over a period of several days resulted in the formation of purple crystals, which however gave rise to IR and analytical data different from those of the initially formed complex 1a, in particular not showing any IR absorption typical for BF4 2 ions. The X-ray crystal analysis of the new complex 1b, the structure of which is given in Fig. 1, revealed that a fluoride ion was abstracted from the BF4 2 and incorporated in the bridging position between the two cobalt atoms. Ample precedent is indeed reported for such a process, as fluorinated counter ions of the type BF4 2 or PF6 2 have long been known to be potentially reactive sources of fluoride.10,11 The molecular structure of the cation of complex 1b shows a m-pyrazolato-m-fluoro-dicobalt(II) core with the co-ordination geometry around each cobalt centre being intermediate between distorted trigonal bipyramidal [the bridging fluoride and the branching nitrogen N(3) and N(6) in axial positions] and distorted square pyramidal [N(5) and N(8) occupying the apical positions].The central atoms Co(1), F, Co(2), N(2) and N(1) form a cyclic array (planar within 0.013 Å) that is nearly coplanar with the plane of the pyrazolate heterocycle (intersect-208 J. Chem. Soc., Dalton Trans., 1998, Pages 207–213 ing angle 2.98).The structure of the cation of 1b thus is very similar to those of the Cl-bridged analogue reported previously, 9a however the smaller fluoride bridge results in a much shorter Co ? ? ? Co separation of 3.577 Å (Table 1) in the present case as compared to 3.909 Å for the chloro-compound. The readily occurring abstraction of fluoride from the original BF4 2 counter anion and its insertion between the two cobalt atoms in complex 1b is probably enhanced by the strong tendency of pyrazolate-based dinuclear entities to incorporate additional secondary bridges.We thus assumed that the use of a primary dinucleating ligand with shorter chelating side arms, which can be shown from simple molecular models to pull the two metal centres further back and apart and create a bimetallic pocket not suited to fit a small anion like fluoride or hydroxide in a bridging fashion, might stabilise an intact BF4 2 counter anion in the bridging position.It should be noted in this context that we recently observed a F,F9-bridging BF4 2 ion in the solid state structure of a bis(m-pyrazolato)-bridged dinuclear copper(II) complex.9b Treatment of the deprotonated ligand L2 with 2 equivalents of [Co(MeCN)6][BF4]2 yields a purple solution, from which after anion exchange the light purple complex 2a could be isolated. Its analytical data were in accord with the composition [Co2L2(BF4)][BPh4]2, however all attempts to obtain single crystals of 2a suitable for X-ray analysis unfortunately failed.When however a solution of 2a in acetonitrile was treated with a small amount of water a spontaneous decolorisation took place and a pale grey complex formed. Single crystals of this compound 2b were obtained by vapour diffusion of diethyl ether into an acetonitrile solution of the material. The IR spectrum of 2b revealed broad bands at 3471 and 2612 cm21 attributed to a hydrogen bridged OH group, and the overall structure of the complex was elucidated by a crystallographic study.Fig. 1 View of the molecular structure of the cation of complex 1b (30% probability ellipsoids). For clarity all hydrogen atoms have been omitted Table 1 Selected atom distances (Å) and angles (8) for complex 1b Co(1)]N(1) Co(1)]N(3) Co(1)]N(4) Co(1)]N(5) Co(1)]F Co(2)]N(2) N(1)]Co(1)]N(3) N(1)]Co(1)]N(4) N(1)]Co(1)]N(5) N(1)]Co(1)]F N(3)]Co(1)]N(4) N(3)]Co(1)]N(5) N(3)]Co(1)]F N(4)]Co(1)]N(5) N(4)]Co(1)]F N(5)]Co(1)]F N(2)]Co(2)]N(6) N(2)]Co(2)]N(7) 1.944(1) 2.403(4) 2.085(5) 2.073(5) 2.077(3) 1.945(4) 74.0(2) 130.4(2) 111.5(2) 85.9(2) 91.4(2) 89.1(2) 157.4(2) 115.4(2) 93.9(2) 108.1(2) 75.0(2) 130.1(2) Co(2)]N(6) Co(2)]N(7) Co(2)]N(8) Co(2)]F N(1)]N(2) Co(1) ? ? ? Co(2) N(2)]Co(2)]N(8) N(2)]Co(2)]F N(6)]Co(2)]N(7) N(6)]Co(2)]N(8) N(6)]Co(2)]F N(7)]Co(2)]N(8) N(7)]Co(2)]F N(8)]Co(2)]F Co(1)]N(1)]N(2) Co(2)]N(2)]N(1) Co(1)]F]Co(2) 2.350(5) 2.074(5) 2.090(5) 2.077(3) 1.365(6) 3.577 114.0(2) 85.8(2) 92.7(2) 90.4(2) 159.4(2) 114.3(2) 94.1(2) 104.3(2) 124.6(3) 124.8(3) 118.9(2) Complex 2b crystallises in space group P1� with three acetonitrile solvent molecules per formula unit.The molecular structure of the cation is depicted in Fig. 2. It shows two Co atoms bridged by the pyrazolate moiety and with each cobalt centre being co-ordinated by a tren-type co-ordination subunit of the ligand L2. As in the case of 1b a fluoride ion has been abstracted from the BF4 2 starting material, however in the present compound 2b the shorter chain lengths of the ligand side arms do not favour the formation of sufficiently short Co ? ? ? Co separations suitable to support the small fluoride anion in a bridging position.Consequently the fluoride ligand is bound only to Co(2) and an additional water molecule is incorporated in order to complete the co-ordination sphere around Co(1). The Co-bound oxygen and fluorine atoms are linked by a strong O]H]F bridge [d(O ? ? ? F) = 2.437 Å, Table 2], while the other H atom of the water molecule forms a hydrogen bond to the N atom of one of the acetonitrile solvent molecules included in the crystal lattice [d(O ? ? ? N) = 2.957 Å].It should be noted that the intramolecular hydrogen bond encountered in 2b is among the shortest O]H]F bridges characterised structurally, which mostly exhibit O ? ? ? F distances larger than 2.5 Å.11,12 Each cobalt centre of the dinuclear cation of 2b is in a slightly distorted trigonal-bipyramidal environment Fig. 2 View of the molecular structure of the cation of complex 2b. Details as in Fig. 1 Table 2 Selected atom distances (Å) and angles (8) for complex 2b Co(1)]N(1) Co(1)]N(3) Co(1)]N(4) Co(1)]N(5) Co(1)]O(1) Co(2)]N(2) Co(2)]N(6) Co(2)]N(7) Co(2)]N(8) N(1)]Co(1)]N(3) N(1)]Co(1)]N(4) N(1)]Co(1)]N(5) N(1)]Co(1)]O(1) N(3)]Co(1)]N(4) N(3)]Co(1)]N(5) N(3)]Co(1)]O(1) N(4)]Co(1)]N(5) N(4)]Co(1)]O(1) N(5)]Co(1)]O(1) N(2)]Co(2)]N(6) N(2)]Co(2)]N(7) 2.042(4) 2.204(4) 2.141(5) 2.157(4) 2.032(4) 2.040(4) 2.201(4) 2.136(5) 2.172(5) 78.2(2) 123.9(2) 108.9(2) 102.1(2) 81.0(2) 83.0(2) 174.6(2) 119.5(2) 94.4(2) 101.9(2) 79.1(2) 113.0(2) Co(2)]F N(1)]N(2) Co(1) ? ? ? Co(2) O(1)]H(10) O(1)]H(20) F]H(10) F ? ? ? O(1) O(1) ? ? ? N(37) N(2)]Co(2)]N(8) N(2)]Co(2)]F N(6)]Co(2)]N(7) N(6)]Co(2)]N(8) N(6)]Co(2)]F N(7)]Co(2)]N(8) N(7)]Co(2)]F N(8)]Co(2)]F Co(1)]N(1)]N(2) Co(2)]N(2)]N(1) O(1)]H(10)]F H(10)]O(1)]H(20) 1.932(3) 1.378(5) 4.282 1.24(6) 0.80(3) 1.23(6) 2.437 2.957 118.2(2) 102.0(2) 81.4(2) 82.0(2) 177.4(2) 121.4(2) 100.2(2) 95.4(2) 135.0(3) 134.8(3) 163(5) 104(5)J.Chem. Soc., Dalton Trans., 1998, Pages 207–213 209 with the branching N atoms [N(3) and N(6)] and the O and F atoms, respectively, in the axial positions [N(3)]Co(1)]O(1) 174.6(2), N(6)]Co(2)]F 177.4(2)8]. The angles between the bridgehead amine nitrogen atom [N(3) and N(6)], the respective Co atom and the equatorial nitrogen atoms [N(1), N(4), N(5) and N(2), N(7), N(8), respectively] lie in the range 78.2(2) to 83.0(2)8, thus deviating from the ideal co-ordination angle of 908.This distortion is due to the limited dimensions of each tren-type co-ordination subunit of the dinucleating ligand framework. Analogous co-ordination geometries of the metal centres have been observed for related mononuclear compounds.11,13 The distance Co(2)]F [1.932(3) Å] in complex 2b is signifi- cantly shorter than the corresponding ones in 1b [Co(1)]F and Co(2)]F 2.077(3) Å], as are the bond lengths Co(1)]N(3) and Co(2)]N(6) [2.403(4)/2.350(5) Å in 1b vs. 2.204(4)/2.201(4) Å in 2b]. This indicates that even for the longer side arms in 1b the dinuclear framework has to be stretched in order to accommodate the small fluoride ion in a bridging position. However, treatment of a solution of 1b in acetonitrile with small amounts of water, i.e. the conditions used to generate 2b, did not lead to any observable reaction.If a sample of the crystalline compound 2b is kept under dynamic vacuum (<1022 mbar) for prolonged periods of time or heated to above 80 8C a change from greenish grey to purple is observed. This process is reversible, causing the material to turn grey again upon exposure to air. A combined TGA/DSC experiment on 2b revealed that a series of endothermic events takes place in the temperature range 80–100 8C, which are accompanied by a loss of weight of around 2% (melting or further decomposition processes only occur well above 200 8C).The IR spectrum of the purple material 2c differs from those of 2b by the lack of the broad bands attributed to O]H vibrations (see above). Considering the given evidence, we assume that the incorporated water molecule in 2b is reversibly extruded upon conversion into 2c. However, no definite information about the constitution of the latter compound is yet available. The large metal–metal separation imposed by the chelating ligand framework of L2, which obviously renders the small fluoride ion in complex 2b unsuited to span both Co atoms, should bring about a distinct size selectivity for secondary anions in this type of complex.Therefore we expected a facile displacement of the FHO(H) unit in 2b by larger moieties capable of locking into the co-ordination pocket created by the two cobalt centres. Treatment of a solution of 2b with 1 equivalent of KBr caused a spontaneous colour change of the reaction mixture to deep purple, and large purple crystals of the expected product [Co2L2Br][BPh4]2 3 formed upon slow diffusion of Et2O into the acetonitrile solution.For comparison, we independently synthesized 3 starting from HL2 and CoBr2?dme (dme = 1,2-dimethoxyethane) following the general strategy described for the analogous chloro complex.9a The molecular structure of the cation of 3, which crystallises in space group P1� , is depicted in Fig. 3. It is similar to the crystal structure of the analogous Cl-bridged complex.9a Although the comparatively larger bromide ion allows for a slightly longer Co ? ? ? Co distance (3.935 vs. 3.833 Å, Table 3) and a smaller bonding angle at the bridging halide in the present case [Co]X]Co 99.3(1)8 for X = Br vs. 103.9(1)8 for X = Cl], the co-ordination geometries around the cobalt centres do not show any signifi- cant difference for the two related compounds [compare e.g.Nax]Co]X 167.3(2)/166.2(3) (X = Br) vs. 166.2(2)/165.9(2)8 (X = Cl)]. As a further point of interest we examined whether the geometrical constraints of the dinucleating ligand L2, which creates a large cavity between the two juxtaposed cobalt atoms, determines the co-ordination mode of a flexidentate ligand like the azide anion. The latter anion is known to be able to connect two metal centres either as a m-1,3-N3 bridge or via a single nitrogen atom, i.e. in the m-1,1-N3 mode.14,15 While in the absence of a primary bridging ligand the role of the azide is largely left to chance, control of the dinuclear centre dimensions and hence control over the azide bridging mode recently gained particular interest with regard to a study of the geometry-dependent magnetic superexchange propagated by the azide bridge.15,16 In the present case the large metal–metal separation imposed by the ligand framework L2 was supposed to prevent a m-1,1-N3 bridge and to force the azide to adopt the m-1,3-N3 mode.Similar to the above-mentioned replacement of the bridging FHO(H) moiety in complex 2b by bromide ions, addition of 1 equivalent of NaN3 to a solution of 2b in acetonitrile caused a change to deep purple, and crystals of the expected azidebridged complex2L2(N3)][BPh4]2 4 were obtained by slow diffusion of Et2O into an acetone solution of the product. Complex 4 had been prepared previously by Okawa and coworkers, 6c however no definite structural information could be obtained.The IR spectrum of 4 shows a strong absorption at 2064 cm21 attributed to the N3 stretching vibration, this value being similar to the band position previously observed for a m-1,3-azide in a bridging position between two cobalt centres.17 The molecular structure of the cation of 4, which crystallises in the monoclinic space group P21/n, is depicted in Fig. 4. In accord with the IR data the azide bridge spans the two cobalt centres by the terminal nitrogen atoms N(9) and N(11), thereby stretching the Co ? ? ? Co distance to 4.415 Å (Table 4).The N3 moiety is almost linear [N(9)]N(10)]N(11) 176(1)8] with angles Co]N]N of 116.8(6) and 118.4(5)8. The co-ordination geom- Fig. 3 View of the molecular structure of the cation of complex 3. Details as in Fig. 1 Table 3 Selected atom distances (Å) and angles (8) for complex 3 Co(1)]N(2) Co(1)]N(3) Co(1)]N(4) Co(1)]N(7) Co(1)]Br Co(2)]N(1) N(2)]Co(1)]N(3) N(2)]Co(1)]N(4) N(2)]Co(1)]N(7) N(2)]Co(1)]Br N(3)]Co(1)]N(4) N(3)]Co(1)]N(7) N(3)]Co(1)]Br N(4)]Co(1)]N(7) N(4)]Co(1)]Br N(7)]Co(1)]Br N(1)]Co(2)]N(5) N(1)]Co(2)]N(6) 1.971(7) 2.225(6) 2.124(8) 2.095(7) 2.563(2) 1.981(8) 77.8(3) 116.5(3) 114.1(3) 89.9(2) 83.2(3) 82.2(3) 167.3(2) 122.3(3) 99.9(2) 106.0(2) 77.3(3) 117.1(4) Co(2)]N(5) Co(2)]N(6) Co(2)]N(8) Co(2)]Br N(1)]N(2) Co(1) ? ? ? Co(2) N(1)]Co(2)]N(8) N(1)]Co(2)]Br N(5)]Co(2)]N(6) N(5)]Co(2)]N(8) N(5)]Co(2)]Br N(6)]Co(2)]N(8) N(6)]Co(2)]Br N(8)]Co(2)]Br Co(1)]Br]Co(2) Co(1)]N(2)]N(1) Co(2)]N(1)]N(2) 2.230(8) 2.11(1) 2.140(9) 2.601(2) 1.34(1) 3.935 114.8(3) 88.9(2) 82.4(4) 82.7(3) 166.2(3) 120.7(4) 104.7(2) 103.1(2) 99.3(1) 130.6(5) 130.9(5)210 J.Chem. Soc., Dalton Trans., 1998, Pages 207–213 etry around the cobalt centres is similar to those in the starting material 2b, i.e. distorted trigonal bipyramidal with the branching nitrogen atoms of the side arms of L2 [N(3) and N(5)] and the co-ordinating outer nitrogen atoms of the secondary azide ligand [N(9) and N(11)] in the axial positions.The two cobalt atoms are 0.33 Å above and below the plane defined by the pyrazolate heterocycle, respectively. With the middle N atom of the azide being situated roughly within this plane (distance 0.07 Å), the bond axis N(9)]N(10)]N(11) intersects the plane defined by the pyrazolate by an angle of around 258. Thus the framework of linked tren-type co-ordination subunits in the pyrazolate-based dinuclear complexes described here proves flexible enough to adapt to various secondary bridges of sufficiently large size, while small monoatomic bridges can be prevented by the use of appropriate short side arms. Thereby the co-ordination geometry around the metal ions remains within the variable types of five-co-ordination, i.e.between square pyramidal and trigonal bipyramidal. Five-coordination of the cobalt(II) centres in solution is corroborated by the UV/VIS spectra for all complexes studied (Table 5).18 Magnetic properties of complexes 3 and 4 The magnetic properties of complexes 3 and 4 were studied over the temperature range 8–290 K.Magnetic susceptibility data Fig. 4 View of the molecular structure of the cation of complex 4. Details as in Fig. 1 Table 4 Selected atom distances (Å) and angles (8) for complex 4 Co(1)]N(2) Co(1)]N(3) Co(1)]N(4) Co(1)]N(7) Co(1)]N(9) Co(2)]N(1) Co(2)]N(5) N(2)]Co(1)]N(3) N(2)]Co(1)]N(4) N(2)]Co(1)]N(7) N(2)]Co(1)]N(9) N(3)]Co(1)]N(4) N(3)]Co(1)]N(7) N(3)]Co(1)]N(9) N(4)]Co(1)]N(7) N(4)]Co(1)]N(9) N(7)]Co(1)]N(9) N(1)]Co(2)]N(5) N(1)]Co(2)]N(6) N(1)]Co(2)]N(8) 2.038(6) 2.167(5) 2.089(8) 2.07(1) 2.074(8) 2.043(5) 2.177(6) 80.9(2) 109.4(4) 100.1(4) 98.5(3) 82.5(3) 83.0(3) 174.8(4) 144.4(5) 102.5(4) 92.1(5) 80.0(2) 113.2(2) 111.6(2) Co(2)]N(6) Co(2)]N(8) Co(2)]N(11) N(1)]N(2) N(9)]N(10) N(10)]N(11) Co(1) ? ? ? Co(2) N(1)]Co(2)]N(11) N(5)]Co(2)]N(6) N(5)]Co(2)]N(8) N(5)]Co(2)]N(11) N(6)]Co(2)]N(8) N(6)]Co(2)]N(11) N(8)]Co(2)]N(11) Co(1)]N(2)]N(1) Co(2)]N(1)]N(2) Co(1)]N(9)]N(10) Co(2)]N(11)]N(10) N(9)]N(10)]N(11) 2.158(6) 2.162(6) 2.062(7) 1.384(8) 1.15(1) 1.139(9) 4.415 99.5(3) 82.0(2) 82.7(2) 175.8(3) 128.9(2) 94.4(3) 101.3(3) 138.0(4) 136.2(4) 116.8(6) 118.4(5) 176(1) for the Br-bridged compound reveal Curie–Weiss law behaviour over a wide temperature range (linear regression yields C = 4.61, q = 24.30 K) with a magnetic moment of 4.29 ± 0.04 mB per cobalt atom, this value being significantly higher than the spin-only value for a high spin S = ��� situation (3.87 mB).The observed value corresponds well to those generally reported for mononuclear trigonal-bipyramidal high spin cobalt(II) complexes with a N4Br donor set, which were shown to exhibit magnetic moments in the range 4.1–4.8 mB.19 Fitting the experimental data by the theoretical expression of the isotropic Heisenberg model (H = 22JS1S2) for the S1 = S2 = ��� spin-only situation 20 confirms a very weak antiferromagnetic coupling of 21 <J < 0 cm21.In contrast to a previous report,6c we find that the variabletemperature molar susceptibility for complex 4 (Fig. 5) goes through a broad maximum at around 30 K, indicative of antiferromagnetic coupling between the two cobalt centres. A rise of the susceptibility at very low temperatures is probably due to the presence of small amounts of uncoupled paramagnetic impurity. The effective magnetic moment per cobalt ion decreases from 3.93 mB at 290 K to 0.94 mB at 8 K.Such a Fig. 5 Temperature dependence of the magnetic susceptibility (open circles) and magnetic moment (solid squares) per cobalt atom for complexes 3 (top) and 4 (bottom). The line represents the calculated curve Table 5 The UV/VIS data of the complexes (n& /cm21, e/M21 cm21) Complex 1a 1b 2a 2b 34 12 030 (40), 17 670 (sh, 150), 18 730 (195), 19 420 (sh, 190) 12 350 (67), 18 350 (200), 19 450 (190) 14 180 (30), 18 180 (85), 20 490 (115) 13 300 (54), 16 750 (66), 20 600 (210) 13 190 (47), 17 920 (153), 19 530 (sh, 158), 20 000 (160) 13 700 (54), 16 860 (180), 19 530 (140)J.Chem. Soc., Dalton Trans., 1998, Pages 207–213 211 behaviour is indeed expected, as the superexchange propagated by the m-1,3-bridging mode of azide is assumed to be exclusively antiferromagnetic in nature.16 Attempts were made to fit the susceptibility data for 4 by the theoretical expression of the isotropic for the S1 = S2 = ��� spin only situation,20 however an acceptable fit (with J = 212.0 cm21) could only be obtained with an unreasonably low g value of 1.83.The inability satisfactorily to model the experimental data presumably arises from the neglect of unquenched orbital angular momentum and zero-field-splitting effects, which should be included for a more detailed analysis of the magnetic behaviour of 4.21 Conclusion The present work shows that the accessible range of metal– metal separations in bimetallic pyrazolate-based entities can effectively be tuned by different chelating side arms in the 3 and 5 positions of the heterocycle. Dinuclear cobalt(II) complexes of both L1 (having more flexible C3 links between the side arm donor atoms) and L2 (with shorter C2 units within the substituents) readily abstract a fluoride from BF4 2 counter anions.However, while in 1b the fluoride occupies a bridging position between the two cobalt centres that are held at a distance of 3.577 Å, the shorter chelating side arms of L2 pull the metal ions back and apart, thus preventing small moieties like fluoride from spanning both metal centres in a bridging fashion.In the present case 2b an additional water molecule is thus incorporated, forming a short intramolecular F]H]O(H) bond between the two cobalt atoms that are located at a distance of 4.282 Å. Evidence from IR and TGA/DSC measurements suggests that the water molecule can be reversibly extruded under vacuum or at elevated temperatures.Compound 2b serves as a suitable starting material for the introduction of various secondary bridges into pyrazolate-based dinuclear comution of the labile FHO(H) group. This is illustrated by treating 2b with KBr or NaN3, thereby generating the bromide- and azidebridged species 3 and 4, respectively. In the latter compound the large metal–metal separation imposed by the primary ligand framework L2 forces the azide to adopt a m-1,3 bridging mode.As expected and in contrast to a previous report,6c this mode propagates antiferromagnetic coupling between the two highspin d7 cobalt(II) centres, which underlines the importance of designed dinuclear systems in the quest to influence cooperative magnetic properties in a controlled fashion. Furthermore the adjustment of the metal–metal separation in this type of dinuclear complex should allow for the tuning of possible co-operative reactivity at the bimetallic core, e.g.the generation of a highly nucleophilic metal-bonded hydroxide (similar in size to fluoride) that is prevented from spanning both metal centres and thus might develop its nucleophilicity towards various substrate molecules. Work in this regard is presently in progress. Experimental All manipulations were carried out under an atmosphere of dry nitrogen by employing standard Schlenk techniques.Solvents were dried according to established procedures. The compounds HL1 and HL2 were synthesized according to the reported method.9a Microanalyses: Mikroanalytische Laboratorien des Organisch-Chemischen Instituts der Universität Heidelberg. IR spectra: Bruker IFS 66 FTIR. FAB and EI mass spectra: Finnigan MAT 8230. UV/VIS/NIR spectra: Perkin-Elmer Lambda 19. Magnetic measurements: Bruker B-E 15 C8 magnet, B-H 15 field controller, ER4111VT variable-temperature unit, Sartorius M 25 D-S micro balance.TGA/DSC: Mettler system TA 4000, TC 11 processor and TG 50 thermobalance. Preparations Complexes 1a and 1b. A solution of HL1 (0.25 g, 0.54 mmol) in tetrahydrofuran (thf, 25 cm3) was treated with 1 equivalent of LiBu (2.5 M in hexane) and stirred for 15 min at room temperature. All volatile material was removed under vacuum and the residue was taken up in MeCN (25 cm3). Anhydrous [Co- (MeCN)6][BF4]2 (0.52 g, 1.08 mmol) was added in one portion, the now purple reaction mixture being kept stirred for 15 min and finally NaBPh4 (0.37 g, 1.08 mmol) was added.After stirring for 15 min the volume of the solution was reduced to ª5 cm3 and Et2O (40 cm3) added, causing the formation of a purple precipitate. This was filtered off, washed twice with Et2O and dried under vacuum to yield 0.55 g (0.42 mmol, 78%). [Co2L1(BF4)][BPh4]2 1a (Found: C, 67.14; H, 7.51; N, 8.56. C73H93B3Co2F4N8 requires C, 66.99; H, 7.16; N, 8.56%); n& /cm21 3052m, 2979m, 1948w, 1881w, 1828w, 1635m, 1614m, 1579s, 1479s, 1065s (br), 802s, 747s, 734s, 705s and 612m.Vapour diffusion of Et2O into a solution of 1a in MeCN afforded purple crystals of [Co2L1F][BPh4]2 1b (0.30 g, 0.37 mmol) (Found: C, 70.40; H, 7.84; N, 9.18. C73H93B2Co2FN8 requires C, 70.65; H, 7.55; N, 9.03%); n& /cm21 3053m, 2978m, 1948, 1881, 1822w, 1579m, 1478s, 748s, 735s, 707s and 612s. Complexes 2a and 2b. A solution of HL2 (0.28 g, 0.54 mmol) in thf (25 cm3) was treated with 1 equivalent of LiBu (2.5 M in hexane) and stirred for 15 min at room temperature.All volatile material was then removed under vacuum and the residue taken up in MeCN (25 cm3). Anhydrous [Co(MeCN)6][BF4]2 (0.52 g, 1.08 mmol) was added in one portion, the now purple reaction mixture being kept stirred for 15 min and finally NaBPh4 (0.37 g, 1.08 mmol) was added. After stirring for 15 min the volume of the solution was reduced to ª5 cm3 and Et2O (40 cm3) added, causing the formation of a light violet precipitate.This was filtered off, washed twice with Et2O and dried under vacuum to yield 0.64 g (0.47 mmol, 87%) [Co2L2(BF4)][BPh4]2 2a (Found: C, 67.58; H, 7.89; N, 8.65. C77H101B3Co2F4N8 requires C, 67.75; H, 7.46; N, 8.21%); n& /cm21 3055m, 2983m, 1941w, 1888w, 1828w, 1579m, 1478s, 1077s (br), 735s, 707s and 610s. Treatment of a solution of 2a in MeCN (8 cm3) with water (0.1 cm3), followed by EtOH (20 cm3), caused decolorisation and precipitation of a pale grey solid which was filtered off and dried.Vapour diffusion of Et2O into a solution of this material in wet MeCN afforded greenish grey crystals of [Co2L2(F)- (H2O)][BPh4]2?3MeCN 2b?3MeCN (0.46 g, 0.32 mmol) (Found: C, 69.19; H, 8.12; N, 10.70. C77H103B2Co2FN8O? C6H9N3 requires C, 69.31; H, 7.85; N, 10.71%); n& /cm21 3471m (br), 3055m, 2981m, 2612m (br), 2251m, 1941, 1888, 1828w, 1579m, 1477s, 735s, 707s and 610s; m/z 735 {100, [L2Co2F(Ph)]1} and 677 {52%, [L2Co2F(H2O) 1 1]1}. Complex 3.A solution of complex 2b (0.40 g, 0.30 mmol) in MeCN (20 cm3) was treated with KBr (0.04 g, 0.34 mmol) and stirred for 30 min at room temperature, causing the reaction mixture to turn purple. All volatile material was then evaporated in vacuum, the residue taken up in MeCN (20 cm3) and filtered. Vapour diffusion of Et2O into the MeCN solution afforded purple crystals of [Co2L2Br][BPh4]2?0.25 Et2O?1.38 MeCN 3?0.25 Et2O?1.38 MeCN; (0.27 g, 0.19 mmol, 63%) (Found: C, 67.81; H, 7.58; N, 8.36.C77H101B2BrCo2N8 requires C, 68.10; H, 7.50; N, 8.25%); n& /cm21 3054m, 2981m, 1941w, 1881w, 1820w, 1579m, 1478s, 735s, 705s and 611s. Complex 3 can alternatively be prepared from HL2 and CoBr2?dme following a procedure described previously for [Co2L2(Cl)][BPh4]2.9a Complex 4. A solution of complex 2b (0.40 g, 0.30 mmol) in MeCN (20 cm3) was treated with NaN3 (0.02 g, 0.31 mmol) and stirred for 30 min at room temperature, causing the reaction mixture to turn purple.All volatile material was then evaporated in vacuum, the residue taken up in acetone (20 cm3) and filtered. Layering the acetone solution with light petroleum (b.p. 40–60 8C) afforded purple crystals of [Co2L2(N3)][BPh4]2? Me2CO 4?Me2CO (0.30 g, 0.21 mmol, 70%) (Found: C, 69.58; H, 8.00; N, 10.71. C77H101B2Co2N11?C6H3O requires C, 69.72; H,212 J. Chem. Soc., Dalton Trans., 1998, Pages 207–213 Table 6 Crystal data and refinement details for complexes 1b, 2b, 3 and 4 Formula Mr Crystal size/mm Crystal system Space group a/Å b/Å c/Å a/8 b/8 g/8 U/Å3 Dc/g cm23 ZF (000) T/K m(Mo-Ka)/mm21 Scan mode hkl Ranges 2q Range/8 Measured reflections Observed reflections [I > 2s(I)] Refined parameters Residual electron density/e Å23 R1 wR2 (refinement on F 2) Goodness of fit 1b C73H93B2Co2FN8 1241.08 0.30 × 0.30 × 0.30 Triclinic P1� 11.774(1) 14.606(2) 19.919(3) 100.02(1) 99.47(1) 101.16(1) 3239(1) 1.272 2 1320 200 0.564 w 0–13, ±16, ±23 4.1–50.0 11 941 6335 786 0.697, 20.760 0.072 0.177 1.015 2b C77H103B2Co2FN8O?3 C2H3N 1438.3 0.85 × 0.50 × 0.20 Triclinic P1� 12.445(6) 13.038(8) 24.61(1) 90.43(5) 96.31(4) 91.15(5) 3968(4) 1.204 2 1536 203 0.472 w ±15, ±16, 0–30 3.1–52.0 16 974 7787 926 0.532, 20.402 0.068 0.169 1.006 3 C77H101B2BrCo2N8?0.25 C2H10O?1.38 C2H3N 1433.0 0.30 × 0.35 × 0.30 Triclinic P1� 12.822(2) 15.234(3) 23.070(3) 72.44(1) 74.34(1) 66.65(1) 3886(1) 1.225 2 1517 200 0.989 w 0–15, 216 to 17, 226 to 27 3.0–50.1 14 385 6933 888 1.042, –1.185 0.099 0.304 1.177 4 C77H101B2Co2N11?C3H6O 1378.3 0.25 × 0.25 × 0.15 Monoclinic P21/n 12.372(2) 21.443(6) 29.265(5) — 94.65(1) — 7738(3) 1.154 4 2808 200 0.478 w 214–0, 0–20, ±34 3.4–50.0 12 521 7954 879 1.386, 20.664 0.096 0.293 1.049 7.82; N, 11.18%); n& /cm21 3053m, 2985m, 2064s, 1950w, 1881w, 1817w, 1710s, 1579m, 1474s, 735s, 706s and 611s; m/z 1000 {26, [L2Co2(N3)(BPh4)]1}, 758 {100, [L2Co2(N3)Ph]1} and 683 {50%, [L2Co2(N3) 1 1]1}.Crystallography The measurements were carried out on a Siemens P4 (Nicolet Syntex) R3m/v (complexes 1b, 3 and 4) or on a Siemens-Stoe AED2 (2b) four-circle diffractometer with graphitemonochromated Mo-Ka radiation (l 0.710 73 Å). All calculations were performed with a micro-vax computer using the SHELXTL PLUS software package.22 Structures were solved by direct methods with the SHELXS 86 and refined with the SHELXL 93 programs.22 An absorption correction (y scan, Dy = 108) was appliell data.Atomic coordinates and anisotropic thermal parameters of the non-hydrogen atoms were refined by full-matrix least-squares calculation. The hydrogen atoms were placed at calculated positions, except for the bridging hydrogen atoms H(10) and H(20) in 2b which were located in the difference Fourier map and refined. Owing to the moderate quality of the crystals and disorder problems the structure analyses of 3 and 4 could only be refined to final (poor) agreement values of R = 0.099 and 0.096, respectively. In the case of 3 the solvent molecules included in the crystal lattice showed disorder and were thus only refined isotropically.In the case of 4 the acetone solvent molecule was located at two different positions and the side arm atoms around Co(1) were severely disordered and in part only refined isotropically. Table 6 compiles the data for the structure determinations.CCDC reference number 186/781. See http://www.rsc.org/suppdata/dt/1998/207/ for crystallographic files in .cif format. Acknowledgements We are grateful to Professor Dr. G. Huttner for his generous and continuous support of our work as well as to the Deutsche Forschungsgemeinschaft (Habilitandenstipendium for F. M.) and the Fonds der Chemischen Industrie. References 1 K. D. Karlin, Science, 1993, 261, 701; J. Reedijk, Bioinorganic Catalysis, Marcel Dekker, New York, 1993; R.H. Holm, Pure Appl. Chem., 1995, 67, 217; H. Steinhagen and G. Helmchen, Angew. Chem., Int. Ed. Engl., 1996, 35, 2339; N. Sträter, W. N. Lipscomb, T. Klabunde and B. Krebs, Angew. Chem., Int. Ed. Engl., 1996, 35, 2024. 2 See, for example, S. R. Collinson and D. E. Fenton, Coord. Chem. Rev., 1996, 148, 19; H. Okawa and H. Sakiyama, Pure Appl. Chem., 1995, 67, 273; L. Que, jun. and Y. Dong, Acc. Chem. Res., 1996, 29, 190; D. E. Fenton and H. Okawa, Chem. Ber./Recueil, 1997, 130, 433. 3 See, for example, R. Robson, Inorg. Nucl. Chem. Lett., 1970, 6, 125; K. D. Karlin, J. C. Hayes, Y. Gultneh, R. W. Cruse, J. W. McKnown, J. P. Hutchinson and J. Zubieta, J. Am. Chem. Soc., 1984, 106, 2121; T. N. Sorrell, D. L. Jameson and C. J. O’Connor, Inorg. Chem., 1984, 23, 190; Y. Nishida, H. Shimo, H. Maehara and S. Kida, J. Chem. Soc., Dalton Trans., 1985, 1945; D. Volkmer, B. Hommerich, K. Griesar, W. Haase and B. Krebs, Inorg. Chem., 1996, 35, 3792. 4 P.J. Steel, Coord. Chem. Rev., 1990, 106, 227; A. P. Sadimenko and S. S. Basson, Coord. Chem. Rev., 1996, 147, 247. 5 T. G. Schenck, J. M. Downes, C. R. C. Milne, P. B. Mackenzie, H. Boucher, J. Whelan and B. Bosnich, Inorg. Chem., 1985, 24, 2334. 6 (a) T. Kamiusuki, H. Okawa, E. Kitaura, M. Koikawa, N. Matsumoto, S. Kida and H. Oshio, J. Chem. Soc., Dalton Trans., 1989, 2077; (b) T. Kamiusuki, H. Okawa, N. Matsumoto and S. Kida, J. Chem. Soc., Dalton Trans., 1990, 195; (c) T.Kamiusuki, H. Okawa, E. Kitaura, K. Inoue and S. Kida, Inorg. Chim. Acta, 1991, 179, 139; (d ) M. Itoh, K. Motoda, K. Shindo, T. Kamiusuki, H. Sakiyama, N. Matsumoto and H. Okawa, J. Chem. Soc., Dalton Trans., 1995, 3635. 7 B. Mernari, F. Abraham, M. Lagrenee, M. Drillon and P. Legoll, J. Chem. Soc., Dalton Trans., 1993, 1707. 8 L. Behle, M. Neuburger, M. Zehnder and T. A. Kaden, Helv. Chim. Acta, 1995, 78, 693. 9 (a) F. Meyer, S. Beyreuther, K. Heinze and L. Zsolnai, Chem. Ber./ Recueil, 1997, 130, 605; (b) F.Meyer, A. Jacobi and L. Zsolnai, Chem. Ber./Recueil, 1997, 130, 1441. 10 T. R. Musgrave and T. S. Lin, J. Coord. Chem., 1973, 2, 323; M. A. Guichelaar, J. A. M. van Hest and J. Reedijk, Inorg. Nucl. Chem. Lett., 1974, 10, 999; F. J. Rietmeyer, R. A. G. de Graaf and J. Reedijk, Inorg. Chem., 1984, 23, 151; S. C. Lee and R. H. Holm, Inorg. Chem., 1993, 32, 4745.J. Chem. Soc., Dalton Trans., 1998, Pages 207–213 213 11 G. J. van Driel, W. L. Driessen and J. Reedijk, Inorg. Chem., 1985, 24, 2919. 12 P. Bukovec, S. Milicev, A. Dems¡ar and L. Golic, J. Chem. Soc., Dalton Trans., 1981, 1802; A. J. Blake, M. A. Halcrow and M. Schröder, J. Chem. Soc., Dalton Trans., 1992, 2803; P. J. van Koningsbruggen, J. G. Haasnot, R. A. G. de Graaf and J. Reedijk, J. Chem. Soc., Dalton Trans., 1993, 483. 13 A. M. Dittler-Klingemann and F. E. Hahn, Inorg. Chem., 1996, 35, 1996; C. Benelli, I. Bertini, M. Di Vaira and F. Mani, Inorg. Chem., 1984, 23, 1422. 14 Z. Dori and R. F. Ziolo, Chem. Rev., 1973, 73, 247. 15 J. Ribas, M. Montfort, B. K. Gosh and X. Solans, Angew. Chem., Int. Ed. Engl., 1994, 33, 2087; J. Ribas, M. Montfort, B. K. Gosh, R. Cortes, X. Solans and M. Font-Bardia, Inorg. Chem., 1996, 35, 864. 16 O. Kahn, in Magneto Structural Correlations in Exchange Coupled Systems, eds. R. D. Willet, D. Gatteschi and O. Kahn, Reidel, Dordrecht, 1985, p. 57; L. K. Thompson and S. S. Tandon, Comments Inorg. Chem., 1996, 18, 125. 17 A. Bencini, C. A. Ghilardi, S. Midollini and A. Orlandini, Inorg. Chem., 1989, 28, 1958. 18 M. Ciampolini, N. Nardi and G. P. Speroni, Coord. Chem. Rev., 1966, 1, 222; C. Furlani, Coord. Chem. Rev., 1968, 3, 141. 19 M. Ciampolini and N. Nardi, Inorg. Chem., 1966, 5, 41; L. V. Interrante and J. L. Shafer, Inorg. Nucl. Chem. Lett., 1968, 4, 411; A. Dei and R. Morassi, J. Chem. Soc. A, 1971, 2024; L. K. Thompson, B. S. Ramaswamy and E. A. Seymour, Can. J. Chem., 1977, 55, 878. 20 C. J. O’Connor, Prog. Inorg. Chem., 1982, 29, 203. 21 M. E. Lines, J. Chem. Phys., 1971, 55, 2977. 22 G. M. Sheldrick, SHELXTL PLUS, Program Package for Structure Solution and Refinement, Siemens Analytical Instruments, Madison, WI, 1990; SHELXL 93, Program for Crystal Structure Refinement, Universität Göttingen, 1993; G. M. Sheldrick, SHELXS-86, Program for Crystal Structure Solution, Universität Göttingen, 1986. Received 31st July 1997; Paper 7/05545E

ISSN:1477-9226    

DOI:10.1039/a705545e

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1999, 209–213 209 Crystal structures of nitridotechnetium(V) complexes of amine oximes diVering in carbon chain lengths Yuko Kani, Tsutomu Takayama, Tsutomu Sekine * and Hiroshi Kudo Department of Chemistry, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan Received 7th August 1998, Accepted 12th November 1998 Structures of nitridotechnetium(V) amine oxime complexes, [TcN(pnao)(H2O)][BPh4] 1, [TcN(bnao)(H2O)][BPh4] 2 and [TcN(pentao)(H2O)][BPh4] 3 [Hpnao = HON]] CMeCMe2NH(CH2)3NHCMe2CMe]] NOH; Hbnao = HON]] CMeCMe2NH(CH2)4NHCMe2CMe]] NOH; Hpentao = HON]] CMeCMe2NH(CH2)5NHCMe2CMe]] NOH], diVering in carbon chain length of the amine oxime ligands, were characterized by X-ray crystallography.These complexes are six-co-ordinated and distorted octahedral. Four nitrogen atoms of the amine oxime ligands are in the equatorial plane and both the nitrido and H2O ligands in the apical positions.These complexes have an asymmetrical intramolecular hydrogen bond between the two oxime oxygen atoms. Their intramolecular O ? ? ? O distances are 2.720 Å in 1, 2.512 Å in 2 and 2.531 Å in 3. The longest O ? ? ? O distance in 1 is ascribed to a steric eVect of the carbon chain length between the amine nitrogens. Namely, the shorter carbon chain of the pnao ligand causes strain on the co-ordinated pnao moiety, and the O ? ? ? O distance in 1 is longer than that in 2 and 3 with longer carbon chains.Introduction A number of studies have been carried out on structures of amine oxime complexes of transition metals by X-ray and neutron diVraction crystallography.1–10 Amine oxime complexes have an intramolecular hydrogen bond between the oxime oxygens, and the structural analysis gives a clue to an understanding of the nature of the hydrogen bonds. The intramolecular hydrogen bond distance (O ? ? ? O) in amine oxime complexes depends on the size of the metal ions and the steric requirements of the amine oxime ligands in the square plane around the metal. For example, the O ? ? ? O distance in the cobalt(III) complex of pnao (3,3,9,9-tetramethyl-4,8-diazaundecane-2,10- dione dioximate) is 2.432 Å,5 while the same ligand gives a longer O ? ? ? O distance (2.474 Å) in the rhodium(III) complex.6 In amine oxime complexes of NiII with various carbon chain lengths between the amine nitrogens, the O ? ? ? O distance (2.478 Å) in the enao (3,3,8,8-tetramethyl-4,7-diazadecane-2,9- dione dioximate) complex with the shortest carbon chain 7 is longer than those in the pnao (2.409 Å) 8 and bnao (3,3,10, 10-tetramethyl-4,9-diazadodecane-2,11-dione dioximate) complexes (2.417 Å).10 However, systematic studies on the relation between the O ? ? ? O distance and the carbon chain length are limited.Although structures of the enao, pnao and bnao complexes of RhIII and CuII have been studied,6,9–11 those with enao and bnao are dinuclear, and the character of the intramolecular hydrogen bond in these complexes cannot be compared directly with that in mononuclear pnao complexes.We have recently determined the crystal structure of the pnao complex of nitridotechnetium(V), [TcN(pnao)(H2O)]- N N N (CH2) n N HO OH H H n = 2 345 Henao Hpnao Hbnao Hpentao [BPh4].12 Its O ? ? ? O distance [2.720(5) Å] of the intramolecular hydrogen bond is longer than those in pnao complexes of other transition metals.12 The [TcN(pnao)(H2O)]1 complex has a nitrido (N32) ligand at the apical position, and electronic properties of the nitrido ligand would account for a longer O ? ? ?O distance in [TcN(pnao)(H2O)]1 than that in pnao complexes without nitrido ligands.The nitrido ligand is a strong p electron donor, and weakens a bond in the trans position to itself by the trans influence.13 Lengthening of a bond between the central metal and the trans ligand is almost invariably accompanied by bending of cis ligands away from the nitrido ligand.13 In [TcN(pnao)(H2O)]1 two structural features of the trans influence are observed; the bond length between the technetium and the oxygen atom of an aqua ligand in the trans position to the nitrido ligand is fairly long (2.481 Å) and the nitrido–technetium–cis ligand angles are about 1008.12 An electron donation of the nitrido ligand and bending of the cis ligands would weaken the bond between the technetium and the cis nitrogen atoms.The weakening of technetium–cis nitrogen bonds results in a longer distance between the oxime nitrogens, and the O ? ? ? O distance in [TcN(pnao)(H2O)]1 becomes long. In addition to electronic factors, it is essential to examine a steric factor associated with the length of amine oxime ligands. In this respect, we have synthesized amine oxime complexes of nitridotechnetium(V) with longer carbon chains such as bnao and pentao. This paper reports the structures of these complexes determined by X-ray crystallography, and discusses the structural features of [TcN(pnao)(H2O)][BPh4] 1, [TcN(bnao)- (H2O)][BPh4] 2 and [TcN(pentao)(H2O)][BPh4] 3, focusing on the intramolecular hydrogen bond.Results and discussion The nitridotechnetium(V) amine oxime complexes 1–3 were synthesized by ligand exchange reaction of [TcNCl2(PPh3)2] with each amine oxime ligand. The 1H NMR results for the methyl protons of 1–3 are listed in Table 1. The two methyl groups a and b adjacent to the amine nitrogens give two singlet peaks; the peak of the methyl group a near the Tc–Nnitrido bond is downfield from that of the methyl group b.The Tc–Nnitrido210 J. Chem. Soc., Dalton Trans., 1999, 209–213 triple bond is known to generate a downfield environment,14 and the signal of the methyl group near the Tc–Nnitrido bond is more deshielded to shift downfield. The ORTEP15 drawings of the complex cations [TcN(pnao)- (H2O)]1, [TcN(bnao)(H2O)]1 and [TcN(pentao)(H2O)]1 are shown in Figs. 1–3. Selected interatomic distances and angles of these complexes are listed in Table 2. The cations in the nitridotechnetium(V) amine oxime complexes 1-3 are six-co-ordinated and distorted octahedral; i.e. four nitrogen atoms of the amine oxime ligands are in the equatorial plane and both the nitrido and H2O ligands are at the apical positions. The Tc–N(1) distances in 1–3 (ca. 1.6 Å) are comparable with the Tc]] ] N triple-bond distance in other nitridotechnetium( V) complexes (1.59–1.63 Å).16 The Tc–O(3) distance is 2.481(4) Å in 1, 2.472(3) Å in 2 and 2.390(3) Å in 3.The fairly long Tc–O(3) bond length is ascribed to the strong trans Fig. 1 An ORTEP drawing of the complex cation [TcN(pnao)- (H2O)]1 1. Fig. 2 An ORTEP drawing of the complex cation [TcN(bnao)- (H2O)]1 2. N N N (CH2) n N O O Tc N OH2 H a b c Table 1 Proton NMR data a for the methyl protons of nitridotechnetium –amine oxime complexes Complex 1 [TcN(pnao)(H2O)][BPh4] 2 [TcN(bnao)(H2O)][BPh4] 3 [TcN(pentao)(H2O)][BPh4] n b 345 a 1.648 1.606 1.602 b 1.524 1.487 1.525 c 2.150 2.153 2.158 a d in ppm, SiMe4 reference.In CD3CN. b The number of carbons between amine nitrogens. influence of the nitrido ligand. The technetium atom is not on the least-squares plane defined by the four nitrogen atoms of the amine oxime ligands. The deviation of the technetium atom from the plane toward the nitrido ligand is 0.399 Å in 1, 0.344 Å in 2 and 0.315 Å in 3.The complex with larger deviation of the Tc atom has a longer Tc–O(3) distance. The Tc–Namine and Tc–Noxime distances in complexes 1–3 are summarized in Table 3, together with those in amine oxime complexes of other transition metals. The Tc–Namine distances are in the order of 1 < 2 < 3, while the Tc–Noxime distances are nearly the same for 1–3. The Tc–Namine distance in 1 with the pnao ligand is longer than that in the analogous oxotechnetium( V) pnao complex [1.908(3) and 1.917(3) Å] 17 in which the two amine protons of the pnao ligand are lost on co-ordination to Tc.The long distance in 1 would imply a weaker interaction between the Tc and Namine than the Tc and Namide in the oxo- Fig. 3 An ORTEP drawing of the complex cation [TcN(pentao)- (H2O)]1 3. Table 2 Selected interatomic distances (Å) and angles (8) for [TcN- (pnao)(H2O)][BPh4] 1, [TcN(bnao)(H2O)][BPh4] 2 and [TcN(pentao)- (H2O)][BPh4] 3 Tc–N(1) Tc–N(2) Tc–N(3) Tc–N(4) Tc–N(5) Tc–O(3) N(2)–C(1) N(2)–O(1) N(3)–C(2) N(3)–O(2) N(4)–C(3) N(4)–C(11) N(5)–C(4) N(5)–C(12) C(1)–C(3) C(2)–C(4) O(1) ? ? ? O(2) N(1)–Tc–N(2) N(1)–Tc–N(3) N(1)–Tc–N(4) N(1)–Tc–N(5) N(2)–Tc–N(3) N(4)–Tc–N(5) Tc–N(2)–O(1) Tc–N(2)–C(1) Tc–N(3)–O(2) Tc–N(3)–C(2) Tc–N(4)–C(3) Tc–N(4)–C(11) Tc–N(5)–C(4) Tc–N(5)–C(12) 1 1.610(5) 2.055(3) 2.065(4) 2.094(4) 2.113(4) 2.481(4) 1.292(7) 1.363(5) 1.287(6) 1.390(5) 1.518(7) 1.492(6) 1.518(6) 1.496(7) 1.552(7) 1.542(6) 2.720(5) 101.9(2) 102.8(2) 98.9(2) 100.5(2) 99.4(2) 97.2(2) 120.5(3) 118.0(3) 122.0(3) 120.0(3) 111.6(3) 112.9(3) 110.9(3) 111.9(3) 2 1.604(4) 2.062(4) 2.064(4) 2.144(3) 2.146(4) 2.472(3) 1.262(5) 1.362(4) 1.269(5) 1.387(5) 1.533(5) 1.508(6) 1.511(6) 1.498(6) 1.523(6) 1.528(6) 2.512(4) 103.9(2) 100.7(2) 95.8(2) 97.7(2) 96.4(2) 105.2(1) 118.4(3) 120.6(3) 121.2(3) 121.4(3) 109.1(2) 115.2(3) 110.6(3) 115.8(3) 3 1.610(3) 2.077(3) 2.075(3) 2.182(3) 2.164(3) 2.390(3) 1.278(4) 1.382(3) 1.292(5) 1.357(4) 1.528(4) 1.512(4) 1.520(5) 1.512(5) 1.523(5) 1.518(6) 2.531(3) 100.9(1) 100.4(1) 96.8(1) 96.5(1) 95.7(1) 107.1(1) 121.5(2) 121.4(2) 119.7(2) 119.4(3) 109.8(2) 116.7(2) 109.7(2) 118.8(2)J. Chem.Soc., Dalton Trans., 1999, 209–213 211 Table 3 Selected intramolecular distances (Å) in amine oxime complexes of nitridotechnetium(V) and other transition metals without nitrido ligands Complex 1 [TcN(pnao)(H2O)][BPh4] 2 [TcN(bnao)(H2O)][BPh4] 3 [TcN(pentao)(H2O)][BPh4] [Co(pnao)(NO2)2] [Pd(pnao)]NO3 [Cu(pnao)(CN)] [Rh(pnao)Cl2] [Ni(bnao)]I [Cu(bnao)(H2O)]ClO4 M–Namine 2.10 2.15 2.17 1.98 2.04 2.04 2.06 1.92 2.04 M–Noxime 2.06 2.06 2.08 1.90 1.97 1.98 1.99 1.86 1.97 Noxime ? ? ?Noxime 3.14 3.08 3.08 2.88 2.96 2.90 3.02 2.86 2.89 O? ? ?O 2.720(5) 2.512(4) 2.531(3) 2.432(3) 2.474(5) 2.475(4) 2.474(7) 2.417(7) 2.421(5) Ref.This work This work This work 5346 10 10 technetium complex. On the other hand, the Tc–Namine and Tc– Noxime distances in 1–3 are longer than those in amine oxime complexes of other transition metals without nitrido ligands.Strong p donation of the nitrido ligand at the apical position in 1–3 would account for long Tc–Namine and Tc–Noxime distances in the nitridotechnetium complexes, because the strong Tc]] ] N bonding weakens the Tc–Namine and Tc–Noxime bonds. The complexes 1–3 have an intramolecular hydrogen bond between the two oxime oxygen atoms. The hydrogen bond O(1) ? ? ? O(2) distance is 2.720(5) Å in 1, 2.512(4) Å in 2 and 2.531(3) Å in 3.These O ? ? ? O distances are longer than those in amine oxime complexes of CoII, PdII, CuII, NiII and RhIII as seen in Table 3. The long O ? ? ? O distance in 1–3 should also be attributed to strong p donation of the nitrido ligand. Longer Tc–Noxime distances give longer Noxime ? ? ?Noxime distances, and the intramolecular O ? ? ? O distances in 1–3 become longer. When features of intramolecular hydrogen bonding are compared among the nitridotechnetium complexes 1–3, the O ? ? ?O distance in 1 with the shortest carbon chain (propylene) is the longest.This fact suggests that a steric factor arising from the carbon chain length also plays a role in determining the O ? ? ?O distance. In the complex 1 with the shortest carbon chain the N(4)–Tc–N(5) angle is the smallest of the three complexes examined here; i.e. 97.2(2)8 in 1, 105.2(1)8 in 2 and 107.1(1)8 in 3, as listed in Table 2.On the contrary, the N(2)–Tc–N(3) angle, on the opposite side of the carbon chain, is the largest in 1; i.e. 99.4(2)8 in 1, 96.4(2)8 in 2 and 95.7(1)8 in 3. Thus these angles depend on the length of the carbon chains of the ligands. The shorter the carbon chain the wider is the N(2)–Tc–N(3) angle. Thus a shorter carbon chain aVords a longer intramolecular hydrogen bond distance, O(1) ? ? ? O(2), as a result of the elongation of the N(2) ? ? ? N(3) distance. It is also instructive that deviation of the Tc atom from the least-squares plane in 1 is the largest of the three complexes and that the C–C distances in the ligand moieties are longer in 1 than in 2 and 3.These facts reveal that there should be strong strain on the pnao ligand in 1, leading to elongation of the O? ? ? O distance in 1. In 2 and 3 with longer carbon chains the strain on the ligand moieties would not be so strong as in 1. Consequently, the O(1) ? ? ? O(2) distances in 2 and 3 are shorter than that in 1.The O ? ? ? O distances in complexes 1–3 are as long as 2.51– 2.72 Å. This fact suggests that the intramolecular hydrogen bond in these complexes is asymmetrical in the crystalline state. Experiments as well as theories have shown that the O–H ? ? ?O hydrogen bonds with O ? ? ? O distances longer than 2.5 Å are asymmetrical.18 A significant diVerence between the N(2)–O(1) and N(3)–O(2) distances in 1–3 manifests the asymmetrical hydrogen bond.19 Furthermore, the position of hydrogen in the intramolecular hydrogen bond in 1–3 must be restricted by the formation of an intermolecular hydrogen bond between one of the oxime oxygen atoms and the oxygen atom in another molecule in the crystal.In fact, this hydrogen bond is formed between O(1) of the oxime and O(5) of ethanol in 1, O(1) of the oxime and O(3) of an aqua ligand in the neighboring complex cation in 2 and O(2) of the oxime and O(3) of an aqua ligand in the neighboring complex cation in 3.The electron density of this oxime oxygen should be reduced, so that the intramolecular hydrogen bond in 1–3 becomes asymmetrical. Conclusion Structures of amine oxime complexes of nitridotechnetium(V), [TcN(pnao)(H2O)][BPh4] 1, [TcN(bnao)(H2O)][BPh4] 2 and [TcN(pentao)(H2O)][BPh4] 3, were determined by X-ray crystallography. These complexes have an asymmetrical intramolecular hydrogen bond between the oxime oxygen atoms. The intramolecular O ? ? ? O distances determined are 2.720 Å in 1, 2.512 Å in 2 and 2.531 Å in 3.These distances are longer than those in pnao complexes of CoIII, CuII, PdII and RhIII (2.43– 2.48 Å) as well as in bnao complexes of NiII and CuII (ca. 2.42 Å). The presence of a nitrido ligand would contribute to the formation of a longer intramolecular hydrogen bond, because the strong p donation weakens the technetium–amine nitrogen bonding in the complexes. Of these three nitridotechnetium complexes diVering in the carbon chain length of the ligands, the pnao complex with the shortest carbon chain has the longest intramolecular O ? ? ? O distance. This is explained in terms of strain on the pnao moiety in the complex caused by the relatively short propylene chain.The strain would be rather small in the bnao and pentao complexes. Experimental Materials Potassium pertechnetate–99Tc from Radiochemical Centre Amersham was dissolved in an aqueous ammonium solution. The ligands Hpnao, Hbnao and Hpentao were prepared as reported in the literature.20,21 Physical measurements Elemental analyses for carbon, hydrogen and nitrogen were made with a Yanaco CHN CORDER MT-3 analyzer.Technetium contents were determined by radioactivity measurements with a liquid scintillation counter (Aloka LSC-5100). Infrared spectra were taken with a Shimadzu IR-470 spectrophotometer using KBr pellets, 1H and 13C NMR spectra by a JEOL GX 400 with acetonitrile-d3 solution.Preparation of complexes [TcN(pnao)(H2O)][BPh4] 1. The starting material [TcNCl2( PPh3)2] (70 mg, 0.099 mmol), prepared as described,22 was dissolved in a mixture (20 cm3) of CH2Cl2 and ethanol (3 : 1). The pink solution was gently heated to 40 8C, and then 40 mg of Hpnao (0.15 mmol) in 10 cm3 of ethanol were added. The solution was stirred for 30 min until it turned yellow, and then evaporated to dryness with a rotary evaporator. The residue was dissolved in water to remove PPh3.Addition of an aqueous NaBPh4 solution gave a yellow precipitate which was filtered212 J. Chem. Soc., Dalton Trans., 1999, 209–213 oV and washed with water and ethanol. Recrystallization from an acetone–ethanol solution gave yellow crystals of [TcN- (pnao)(H2O)][BPh4] 1 (53 mg, 74%) (Found: C, 61.6; H, 7.10; N, 9.75; Tc, 13.9. C37H49BN5O3Tc requires C, 61.6; H, 6.84; N, 9.71; Tc, 13.7%). n& max/cm21 (KBr) 2315 (OH), 1576 (C]] N) and 1061 (Tc]] ] N). dH(CD3CN) 19.6 (br, O–H ? ? ? O), 3.70 (2 H, dd, CH2), 2.967 (2 H, qd, CH2), 2.37 (2 H, m, CH2), 2.150 (6 H, s, 2CH3), 1.648 (6 H, s, 2CH3) and 1.524 (6 H, s, 2CH3).dC(CD3CN) 50.670 (CH2), 30.421 (CH2), 24.512 (CH3), 19.333 (CH3) and 12.555 (N]] C–CH3). [TcN(bnao)(H2O)][BPh4] 2. A mixture of [TcNCl2(PPh3)2] (73 mg, 0.10 mmol) and Hbnao (40 mg, 0.15 mmol) in CH2Cl2– ethanol (3 : 1) was stirred at 40 8C for 30 min until it turned yellow, then evaporated to dryness with a rotary evaporator.The residue was dissolved in water to remove PPh3. The yellow precipitate given by addition of an aqueous solution of NaBPh4 was filtered oV and washed with water and ethanol. Crystals of [TcN(bnao)(H2O)][BPh4] 2 were obtained by recrystallization from an acetone solution (59 mg, 79%) (Found: C, 62.1; H, 7.19; N, 9.37; Tc, 13.2. C38H51BN5O3Tc requires C, 62.0; H, 6.99; N, 9.52; Tc, 13.5%). n& max/cm21 (KBr) 1758 (OH), 1577 (C]] N) and 1048 (Tc]] ] N). dH(CD3CN) 19.3 (br, O–H ? ? ? O), 3.52 (4H, m, 2CH2), 2.153 (6 H, s, 2CH3), 1.71 (2 H, m, CH2), 1.606 (6 H, s, 2CH3), 1.487 (6 H, s, 2CH3) and 1.45 (2 H, m, CH2).dC(CD3CN) 50.002 (CH2), 26.854 (CH2), 23.742 (CH3), 19.439 (CH3) and 12.912 (N]] C–CH3). [TcN(pentao)(H2O)][BPh4]?(CH3)2CO 3?(CH3)2CO. A mixture of [TcNCl2(PPh3)2] (97 mg, 0.14 mmol) and Hpentao (0.21 mmol) in CH2Cl2–ethanol (3 : 1) was stirred at 40 8C for 2 h until it turned yellow, and then evaporated to dryness. The residue was dissolved in water, and the yellow solution charged on a cation exchange column (Sephadex C-25).An aqueous solution of NaBPh4 was added to the yellow fraction eluted with 0.1 mol dm23 NaCl solution. The yellow precipitate was filtered oV and washed with water and ethanol. Crystals of [TcN(pentao)- (H2O)][BPh4]?(CH3)2CO were obtained by recrystallization from an acetone solution (34 mg, 31%) (Found: C, 62.4; H, 7.36; N, 8.62; Tc, 12.5. C42H59BN5O4Tc requires C, 62.5; H, 7.36; N, 8.67; Tc, 12.3%).n& max/cm21 (KBr) 1770 (OH), 1578 (C]] N) and 1055 (Tc]] ]N). dH(CD3CN) 19.4 (br, O–H ? ? ? O), 3.581 (2 H, m, CH2), 3.367 (2 H, m, CH2), 2.158 (6 H, s, 2CH3), 1.954 (2 H, m, CH2), 1.756 (2 H, m, CH2), 1.602 (6 H, s, 2CH3), 1.57 (2 H, m, CH2) and 1.525 (6 H, s, 2CH3). dC(CD3CN) 51.770 (CH2), 30.087 (CH2), 23.636 (CH3), 19.075 (CH3), 18.908 (CH2) and 13.011 (N]] C–CH3). Table 4 Crystallographic data for [TcN(bnao)(H2O)][BPh4] 2 and [TcN(pentao)(H2O)][BPh4] 3 Formula M Crystal system Space group a/Å b/Å c/Å b/8 V/Å3 Z m/cm21 No.reflections measured No. unique data No. data used with I > ns(I ) RR 9 2 C38H51BN5O3Tc 733.66 Monoclinic P21/n 9.683(3) 24.944(6) 15.149(2) 97.39(3) 3628(1) 4 35.29 (Cu-Ka) 6397 6154 (Rint = 0.046) 4211 (n = 3) 0.046 0.042 3?(CH3)2CO C39H53BN5O3Tc?(CH3)2CO 805.77 Monoclinic P21/n 9.986(5) 30.636(2) 13.967(3) 95.24(3) 4254(2) 4 3.80 (Mo-Ka) 10499 9946 (Rint = 0.036) 5599 (n = 4) 0.034 0.036 Crystal structure determination The crystal structure determination of [TcN(pnao)(H2O)]- [BPh4]?2C2H5OH 1?2C2H5OH has been previously reported.12 [TcN(bnao)(H2O)][BPh4] and [TcN(pentao)(H2O)][BPh4]? (CH3)2CO.Single crystals of [TcN(bnao)(H2O)][BPh4] 2 and [TcN(pentao)(H2O)][BPh4]?(CH3)2CO 3?(CH3)2CO suitable for X-ray analysis were grown by slow evaporation of acetone solutions. The X-ray diVraction data were measured on a Rigaku AFC5R diVractometer with graphite-monochromated Cu-Ka radiation (l = 1.54178 Å) for 2 and Mo-Ka radiation (l = 0.71069 Å) for 3.The data were collected at 13 ± 1 8C using the w–2q scan technique to the maximum 2q values of 126.28 for 2 and 55.08 for 3. The crystallographic data are listed in Table 4. The structures of these two complexes were solved by the direct method (SIR 92) and the expanded using the Fourier technique (DIRDIF 94). The non-hydrogen atoms were refined anisotropically. Hydrogen atoms were included but not refined for 3.The neutral atom scattering factors were taken from ref. 25. Anomalous dispersion eVects were included in Fc;26 the values for Df 9 and Df 0 were those of ref. 27. All of the calculations were made using the TEXSAN28 crystallographic software package. CCDC reference number 186/1246. See http://www.rsc.org/suppdata/dt/1999/209/ for crystallographic files in .cif format. Acknowledgements We thank Dr C. Kabuto and Mr T. Kondo of Instrumental Analysis Center for Chemistry, Graduate School of Science, Tohoku University for their assistance in crystallographic analysis and NMR measurements.References 1 C. K. Fair and E. O. Schlemper, Acta Crystallogr., Sect. B, 1978, 34, 436. 2 I. B. Liss and E. O. Schlemper, Inorg. Chem., 1975, 14, 3035. 3 M. S. Hussain and E. O. Schlemper, Inorg. Chem., 1979, 18, 1116. 4 E. O. Schlemper, M. S. Hussain and R. K. Murmann, Acta Crystallogr., Sect. B, 1981, 37, 234. 5 R. K. Murmann and E. O. Schlemper, Inorg.Chem., 1973, 12, 2625. 6 S. Siripaisarnpipat and E. O. Schlemper, Inorg. Chem., 1984, 23, 330. 7 J. C. Ching and E. O. Schlemper, Inorg. Chem., 1975, 14, 2470. 8 M. S. Hussain and E. O. Schlemper, Inorg. Chem., 1979, 18, 2275. 9 S. Siripaisarnpipat and E. O. Schlemper, Inorg. Chem., 1983, 22, 282. 10 J. Pal, R. K. Murmann, E. O. Schlemper, C. K. Fair and M. S. Hussain, Inorg. Chim. Acta, 1986, 115, 153. 11 D. P. Gavel and E. O. Schlemper, Inorg. Chem., 1979, 18, 283. 12 Y.Kani, T. Takayama, S. Inomata, T. Sekine and H. Kudo, Chem. Lett., 1995, 1059. 13 W. A. Nugent and J. M. Mayer, Metal–Ligand Multiple Bonds, Wiley, New York, 1988; P. D. Lyne and D. M. P. Mingos, J. Chem. Soc., Dalton Trans., 1995, 1635. 14 A. Mahmood, W. A. Halpin, K. E. Baidoo, D. A. Sweigart and S. Z. Lever, Technetium and Rhenium in Chemistry and Nuclear Medicine, 3, eds. M. Nicolini, G. Bandoli and U. Mazzi, Cortina International, Verona, 1990, pp. 113–118. 15 C. K. Johnson, ORTEP, Report ORNL-5138, Oak Ridge National Laboratory, Oak Ridge, TN, 1976. 16 F. Tisato, F. Refosco and G. Bandoli, Coord. Chem. Rev., 1994, 135/ 136, 325 and refs. therein. 17 C. K. Fair, D. E. Troutner, E. O. Schlemper, R. K. Murmann and M. L. Hoppe, Acta Crystallogr., Sect. C, 1984, 40, 1544. 18 G. A. JeVrey, An Introduction to Hydrogen Bonding, Oxford University Press, New York, Oxford, 1997; C. L. Perrin and J. B. Nielson, J. Am. Chem. Soc., 1997, 119, 12734; P. Gilli, V. Bertolasi, V. Ferretti and G. Gilli, J. Am. Chem. Soc., 1994, 116, 909. 19 L. F. Szczepura, J. G. Muller, C. A. Bessel, R. F. See, T. S. Janik, M. R. Churchill and K. J. Takeuchi, Inorg. Chem., 1992, 31, 859; E. O. Schlemper and C. K. Fair, Acta Crystallogr., Sect. B, 1977,J. Chem. Soc., Dalton Trans., 1999, 209–213 213 33, 2482; K. Bowman, A. P. Gaughan and Z. Dori, J. Am. Chem. Soc., 1972, 94, 727. 20 J. M. Lo and K. S. Lin, Appl. Radiat. Isot., 1993, 44, 1139. 21 S. Jurisson, K. Aston, C. K. Fair, E. O. Schlemper, P. R. Sharp and D. E. Troutner, Inorg. Chem., 1987, 26, 3576. 22 J. Baldas, J. Bonnyman and G. A. Williams, Inorg. Chem., 1986, 25, 150. 23 A. Altomare, M. C. Burla, M. Camalli, M. Cascarano, C. Giacovazzo, A. Guagliardi and G. Polidori, SIR 92, J. Appl. Crystallogr., 1994, 27, 435. 24 P. T. Beurskens, G. Admiraal, G. Beurskens, W. P. Bosman, R. de Gelder, R. Israel and J. M. M. Smits, The DIRDIF-94 Program System, Technical Report of the Crystallography Laboratory, University of Nijmegen, The Netherlands, 1994. 25 International Tables for X-Ray Crystallography, Kynoch Press, Birmingham, 1974, vol. IV, Table 2.2A. 26 J. A. Ibers and W. C. Hamilton, Acta Crystallogr., 1964, 17, 781. 27 International Tables for X-Ray Crystallography, Kluwer, Boston, 1992, vol. C, Table 4.2.6.8, pp. 219–222. 28 TEXSAN, Crystal Structure Analysis Package, Molecular Structure Corporation, Houston, TX, 1985 and 1992. Paper 8/06245E

ISSN:1477-9226    

DOI:10.1039/a806245e

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

DALTON J. Chem. Soc., Dalton Trans., 1997, Pages 213–219 213 Investigation of the bonding in methyl titanium trichloride by variable-energy photoelectron spectroscopy and density functional calculations * Christian N. Field,a Jennifer C. Green,a Nikolas Kaltsoyannis,b G. Sean McGrady,a Aidan N. Moody,a Michele Siggel c and Monica De Simone a a Inorganic Chemistry Laboratory, South Parks Road, Oxford OX1 3QR, UK b Department of Chemistry, University College, London, 20 Gordon Street, London WC1H 0AJ, UK C EPSRC Daresbury Laboratory, Daresbury, Warrington WA4 4AD, UK Preparation of an authentically pure sample of [TiMeCl3] has enabled measurement of its photoelectron spectrum with photon energies varying between 20 and 50 eV.Study of the relative partial photoionisation cross-sections of the valence photoelectron bands has enabled a full assignment of the related ion states. The character of the ionising orbitals was also deduced from the cross-section variations.The titanium–carbon bond was shown to have a significant Ti 3d character. Density functional calculations at the non-local level, including estimates of the ionisation energies using Slater’s transition-state method, are in good agreement as to the ion state ordering. Fragment analysis of the one-electron eigenfunctions is fully consistent with the experimentally deduced orbital character. The past decade has witnessed intensive efforts to understand the structure and bonding in the fundamentally important compound methyl titanium trichloride, [TiMeCl3] 1.A report in 1986 concluded that the methyl group in 1 was significantly distorted as the result of an agostic interaction with the titanium centre.1 This was on the basis of a gas-phase electrondiffraction study, with supporting evidence coming from anomalies in the vibrational spectrum of the vapour and remarkable values for the solution NMR parameters d(13C) and 2J(HH). All the evidence pointed to abnormal hybridisation at the carbon atom and a flattened methyl moiety with anomalously long C]H bonds.These results appeared to tally with the crystal structure of the adduct [TiMeCl3]?dmpe 2 (dmpe = Me2PCH2CH2PMe2), which indicated a highly distorted TiMe moiety and an unusually short Ti? ? ?H distance.2 In 1988 the crystal structure of 1 showed the compound to be dimeric in the solid state with chloride bridges and highly distorted methyl groups. This geometry was also interpreted in terms of an agostic Ti? ? ?H]C interaction.3 Since this report, however, substantial reinvestigation has occurred.The gas-phase electron-diffraction pattern of 1 was redetermined, and showed the geometry to be more-or-less normal.4 Remeasurement of 2J(HH) also led to the conclusion that there was nothing anomalous about the methyl group.5 An infrared study of several isotopomers of [TiMeCl3] showed abnormally low d(CH3) and r(CH3) frequencies but the remaining vibrations of the methyl group were normal for an organometallic compound and the n(CH) and n(CD) frequencies were consistent with an unexceptional methyl geometry.6 Hartree–Fock and (MP2) second-order Moeller-Plesset perturbation calculations on 1 and the model compound [TiMeH3] led to the conclusion that the anomalies in the vibrational spectrum were caused by the nature of the Ti]C, rather than the C]H, bonding.7 An all-electron MP2 study of 1 provided a theoretical structure as well as vibrational frequencies in excellent agreement with the revised experimental data.8 The 13C NMR data were similarly reinterpreted.9 * Non-SI units employed: eV ª 1.60 × 10219 J, in = 2.54 × 1022 m.Thus the only remaining evidence for an abnormal methyl group geometry in [TiMeCl3] rests with the solid-state structures of 1 and 2. An early study of the He I and He II photoelectron spectrum of compound 1 concluded that there were ‘striking similarities between the spectra of [TiMeCl3] and TiCl4’.10 In view of our experience regarding the difficulty in obtaining 1 rigorously pure (see Experimental section), suspicions must arise about the integrity of the sample in this earlier report.We, therefore, report below the photoelectron spectrum of an authentic sample of 1. The structure and bonding of the heavy-atom skeleton is also of considerable interest with regard both to the involvement of the atomic orbitals on titanium, and to the extent of p donation from the electronegative Cl ligands to the formally eightelectron d0 titanium centre. Variable-energy photoelectron spectroscopy (PES) affords an ideal technique for assessing both of the above contributions to the bonding.The Ti 3d, Cl 3p and C 2p atomic orbitals (AOs) differ in their photoionisation cross-section variations with photon energy. Use of a synchrotron source enables PE spectral measurement with a wide range of photon energies, and consequent determination of the relative cross-sections of the PE bands enables an analysis of the AO contributions to the associated molecular orbitals (MOs).11 Experimental Initial experiments were conducted to assess the purity of compound 1 produced by the literature method using dimethylzinc as the methylating agent, according to equation (1).4 After 0.5 ZnMe2 + TiCl4 isopentane 0 8C æææÆ [TiMeCl3] (1) filtration and removal of solvent at 278 8C the IR spectrum of the sample obtained always showed the presence of significant amounts of TiCl4 impurity.We attribute this non-stoichiometry to the insolubility and/or reduced methylating capacity of the intermediate methylzinc chloride, ZnMeCl. Use of a 1 : 1 molar214 J. Chem. Soc., Dalton Trans., 1997, Pages 213–219 ratio of ZnMe2 and TiCl4 is known to produce substantial amounts of the higher product dimethyl titanium dichloride [TiMe2Cl2] 3.12 Hence it appears that the ZnMe2–TiCl4– [TiMeCl3]–[TiMe2Cl2] system is complex and nonstoichiometric.Pure compound 1 was obtained by treating TiCl4 (3.16 g, 16.6 mmol) with ZnMe2 (0.82 g, 8.6 mmol) in isopentane (ca. 50 cm3), and by sampling the mixture by gas-phase IR spectroscopy. A solution of ZnMe2 (0.60 g, 2.29 mmol) in isopentane (8.0 cm3) was added to the reaction mixture in 0.25 cm3 aliquots, and the resulting IR spectrum used to monitor the consumption of the excess of TiCl4. A total of 1.5 cm3 of this solution was required to remove the last traces of the tetrachloride, corresponding to an approximate 15% excess of that indicated by equation (1). The final sample was shown to be free from the potential impurities TiCl4 and [TiMe2Cl2] to a level of > 99% by a combination of IR and NMR spectroscopies. 6,13,14 He I and He II PE spectroscopy The He I and He II spectra of [TiMeCl3] were obtained using a PES Laboratories 0078 spectrometer, calibrated using He and Xe.The He I spectrum was fitted using eight asymmetric Gaussian curves. In the He II spectrum the positions of the two inner valence states were fixed by fitting with two symmetric Gaussian curves.Variable-photon-energy PE spectroscopy This experiment was carried out at the synchrotron radiation (SR) facility of the EPSRC Daresbury Laboratory. The SR was monochromated using a toroidal grating monochromator (TGM), at beamline 3.3. The TGM was used with fixed entrance and exit slit widths of 5.5 mm.One grating was employed covering the photon energy range 22–50 eV (710 lines per mm). The photons were introduced to the ionisation region via a glass light guide, 2 mm in diameter. The data were collected using the chemical angle resolved photoelectron spectrometer, CARPES, which is described elsewhere.15 The photoelectrons were energy analysed using the focusing action of a three-element zoom lens to accelerate or retard them followed by a hemispherical analyser of mean radius 45 mm which was operated at a pass energy of 5.355 eV for photon energies of 22–50 eV.Total instrumental energy resolution was in the range 23–35 meV. A position-sensitive multichannel detector was used consisting of a pair of chevronned multichannel plates backed by a resistive anode. Owing to partial polarisation of the incident synchrotron radiation, the lens and analyser were positioned at the ‘magic angle’ with respect to the plane of polarisation of the light so that the photoionisation crosssections, and thus intensities of the various ionisation bands, were not affected by the photoelectron asymmetry parameter, b.The sample was introduced to the ionisation region via stainless-steel tubing (outside diameter ¼ in) and the vapour pressure in the chamber controlled by a needle valve in the sample line. The sample of [TiMeCl3] was stored at 280 8C until immediately before the PES experiment. The data were recorded with the sample at 0 8C and the inlet system at room temperature.A liquid-nitrogen-cooled cold-finger was used to prevent diffusion of the compound into the turbo and rotary pumps. The decay of the electron current in the storage ring was corrected for by linking the scanning rate with the output from a photodiode positioned to intersect the photon beam after its passage through the gas cell. The sensitivity of the photodiode to different radiation energies was determined by measuring the 1s21 PE spectrum of He and the np21 PE spectra of Ar and Xe.16 Fluctuations in sample pressure were estimated and corrected for by recording a calibration spectrum of the compound at a constant photon energy (hn = 30 eV) before and after every data spectrum.These calibration spectra were integrated across the whole spectrum to give a measurement of intensity. Variations in intensities between these calibration spectra were then interpreted as a measure of the pressure fluctuation of the sample.Spectra were measured at intervals between 22 and 50 eV. We were unable to measure spectra over a greater photon-energy range as the sample had a deleterious effect on the channel plates. The results at 50 eV were of inferior quality. Data analysis As the PE spectrum of [TiMeCl3] contains many overlapping bands their areas could not be obtained by direct integration. The bands were deconvoluted by fitting with asymmetric Gaussian functions, the best fit being determined by a leastsquares refinement. To fix the values of the vertical ionisation energies (i.e.) we fitted the He I data without applying any restraint.Band labels are defined in Fig. 1 and Table 1. In fitting the spectra acquired with synchrotron radiation the width of each Gaussian curve was kept constant. These widths were chosen using, as a criterion, achievement of the mean best fit for all the photon energies employed. Band H is the broadest and least well defined in shape as its onset overlaps with band G.The choice to fit it with only one asymmetric Gaussian curve is probably the main reason for the rapid fluctuation in the branching ratios (b.r.) and relative partial photoionization cross-sections (r.p.p.i.c.s.). Though the variations of bands D and E were treated separately, they probably lie too close together for their relative intensities to be disentangled. However the variation of their combined intensities is reliable. The method of deriving b.r.and r.p.p.i.c.s. from the band intensities and the inert-gas calibrations, and the estimated errors involved, has been described elsewhere.15,16 Computations All calculations were performed using the Amsterdam density functional (ADF) program suite.17 Triple-zeta Slater-type orbital atomic basis sets were employed for all orbitals. Frozen cores were used for all elements (except H), C (1s), Cl (2p) and Ti (2p). A single polarisation function was included for all atoms except Ti.The local density functional of Vosko et al.18 was employed with the correlation correction of Stoll et al.19 and Becke’s non-local (gradient) correction 20 to the exchange part of the potential. Ionisation energies were calculated using Slater’s transitionstate method.21 Separate calculations were converged for each ionisation energy. Mulliken population analyses 22 were performed. The molecular geometry employed was that determined by electron diffraction,4 with the exception that the Cl]Ti]C]H torsion angle was set to 08 (i.e.the symmetry was idealised to C3v). Results and Discussion The He I spectrum of [TiMeCl3] is shown in Fig. 1 and the vertical i.e. are in Table 1. The spectrum differs from that obtained in the previous PE study.10 Band A was detectable in the previous spectrum, though of very low intensity, but the Cl 3p ionisation region resembled that of TiCl4. We may conclude that TiCl4 was absent from our sample as it gives (amongst others) a sharp band in the He I spectrum at 13.91 eV which is absent in our spectrum.23–26 Eight bands, A–H, one (D) being a shoulder, are clearly distinguished with ionisation energiesJ. Chem.Soc., Dalton Trans., 1997, Pages 213–219 215 Table 1 Valence molecular orbital eigenvalues, occupations, compositions and ionisation energies for [TiMeCl3] Fragment contribution (%) a Ionisation energies/eV Orbital Band label e/eV Ti Cl Me Calc.b Exptl. 6a1 7e 6e (LUMO) 5a1 (HOMO) 1a2 5e 4a1 4e 3e 3a1 2e 2a1 1e 1a1 AB C DEF GH 22.250 23.144 23.798 27.079 27.576 27.872 28.273 28.457 29.044 29.337 210.103 216.778 219.899 220.106 52 d, 9 p 68 d 81 d 26 d 1 7 d, 5 p 11 d 20 d 5 d 7 p 20 p 13 p 00 p 92 p 89 p 86 p 79 p 87 p 97 s 98 s 24 2a1 (C) 60 2a1 (C) 5 1e (CH) 91 1e (CH) 100 1a1 (CH) 10.372 10.455 10.614 11.063 11.224 11.919 12.180 13.946 20.850 22.859 23.060 10.63 11.55 11.95 12.52 12.76 13.09 13.55 13.99 18.1 22.6 22.6 a If >5%.b Transition-state method. Table 2 The r.p.p.i.c.s.s of bands A–H in the PE spectrum of [TiMeCl3]* r.p.p.i.c.s. of band hn/eV A B C D E F G H 22.00 24.00 25.00 28.00 30.00 32.00 34.00 36.00 38.00 40.00 41.00 42.00 43.00 45.00 50.00 452(9) × 102 442(7) × 102 415(8) × 102 352(6) × 102 283(5) × 102 240(5) × 102 186(4) × 102 166(3) × 102 168(3) × 102 184(3) × 102 183(4) × 102 220(3) × 102 216(3) × 102 193(4) × 102 166(4) × 102 690(10) × 102 600(8) × 102 550(9) × 102 352(7) × 102 228(5) × 102 144(4) × 102 77(2) × 102 51(2) × 102 38(1) × 102 19(1) × 102 13(1) × 102 10(1) × 102 16(1) × 102 15(1) × 102 19(1) × 102 141(1) × 103 110(1) × 103 107(1) × 103 669(9) × 102 454(7) × 102 293(6) × 102 151(3) × 102 106(3) × 102 77(2) × 102 70(2) × 102 62(2) × 102 60(2) × 102 55(2) × 102 49(2) × 102 42(2) × 102 180(2) × 103 184(1) × 103 142(1) × 103 136(1) × 103 836(7) × 102 547(6) × 102 332(4) × 102 172(3) × 102 120(2) × 102 87(2) × 102 90(3) × 102 93(2) × 102 73(2) × 102 74(2) × 102 71(3) × 102 138(1) × 103 866(10) × 102 831(10) × 102 476(8) × 102 350(7) × 102 203(6) × 102 110(5) × 102 73(3) × 102 49(2) × 102 81(2) × 102 101(53) × 102 91(2) × 102 80(2) × 102 73(2) × 102 73(3) × 102 204(2) × 103 156(1) × 103 139(1) × 103 846(10) × 102 567(7) × 102 359(6) × 102 196(4) × 102 146(3) × 102 112(2) × 102 141(3) × 102 207(4) × 102 214(3) × 102 215(3) × 102 190(4) × 102 172(4) × 102 854(10) × 102 745(9) × 102 679(10) × 102 477(8) × 102 319(6) × 102 228(5) × 102 107(3) × 102 105(3) × 102 91(2) × 102 101(3) × 102 98(3) × 102 92(2) × 102 89(2) × 102 71(2) × 102 54(2) × 102 174(2) × 103 191(1) × 103 124(1) × 103 115(1) × 103 772(8) × 102 797(9) × 102 384(5) × 102 499(6) × 102 373(4) × 102 277(4) × 102 266(4) × 102 168(3) × 102 236(4) × 102 213(4) × 102 128(3) × 102 * Errors are statistical associated with band-area measurements.below 16 eV. The He II spectrum (Fig. 2) reveals two further broad ionisation features centred around 18.1 and 22.6 eV.Fig. 3 shows spectra acquired with synchrotron radiation of energy 22, 35 and 43 eV. These reveal striking changes in the relative intensities of the bands. Bands B–E decline in relative intensity with increase in photon energy, F and G initially fall but then recover at higher photon energy, A shows a general rise in relative intensity, whereas H rises but then falls. Branching ratios for bands A–H are plotted in Fig. 4. Individual r.p.p.i.c.s. are given in Fig. 5. These data are also given Fig. 1 The He I PE spectrum of [TiMeCl3] in Tables 2 and 3. Theoretical atomic photoionisation crosssections are shown in Fig. 6.27 These are calculated for direct one-electron photoionisation and do not include allowance for any resonance processes which are frequently found for transition-metal complexes.11 For a detailed band assignment a molecular orbital scheme is required for the molecule. Fig. 7 presents a qualitative scheme based on the density functional calculations, the results of Fig. 2 The He II PE spectrum of [TiMeCl3]216 J. Chem. Soc., Dalton Trans., 1997, Pages 213–219 Table 3 Branching ratios for bands A–H of [TiMeCl3] as a function of photon energy b.r. of band hn/eV A B C D E F G H 22.00 24.00 25.00 28.00 30.00 32.00 34.00 36.00 38.00 40.00 41.00 42.00 43.00 45.00 50.00 0.043(1) 0.051(1) 0.055(1) 0.068(1) 0.081(2) 0.092(2) 0.135(2) 0.131(1) 0.168(3) 0.190(1) 0.179(9) 0.240(4) 0.220(9) 0.220(1) 0.230(2) 0.066(1) 0.069(1) 0.073(1) 0.068(1) 0.066(2) 0.055(2) 0.056(2) 0.041(2) 0.038(2) 0.020(2) 0.012(2) 0.011(2) 0.016(2) 0.017(1) 0.027(3) 0.135(2) 0.127(1) 0.141(2) 0.130(2) 0.131(2) 0.113(2) 0.109(3) 0.084(2) 0.077(2) 0.072(2) 0.061(2) 0.064(2) 0.056(2) 0.056(2) 0.058(3) 0.177(2) 0.164(2) 0.180(2) 0.162(2) 0.158(2) 0.128(2) 0.124(3) 0.094(2) 0.088(2) 0.093(3) 0.091(3) 0.078(2) 0.079(2) 0.085(3) 0.098(4) 0.133(2) 0.100(2) 0.110(2) 0.092(2) 0.101(2) 0.078(3) 0.079(3) 0.058(3) 0.050(3) 0.085(3) 0.099(4) 0.098(4) 0.081(4) 0.083(5) 0.100(6) 0.196(2) 0.180(1) 0.185(1) 0.164(1) 0.163(1) 0.138(2) 0.142(2) 0.115(3) 0.113(3) 0.146(3) 0.202(4) 0.230(4) 0.218(4) 0.215(5) 0.237(6) 0.082(1) 0.086(1) 0.090(1) 0.092(1) 0.092(2) 0.088(2) 0.077(2) 0.083(2) 0.092(2) 0.105(3) 0.096(3) 0.099(2) 0.090(2) 0.081(3) 0.074(3) 0.167(2) 0.221(2) 0.164(2) 0.222(3) 0.208(3) 0.307(3) 0.277(4) 0.394(5) 0.375(5) 0.287(5) 0.260(5) 0.181(3) 0.239(4) 0.242(5) 0.176(5) which are given in Table 1.The transition-state calculations in this case suggest the same ordering for the Kohn–Sham oneelectron energies and the associated ionisation energies. Fig. 3 The PE spectra of [TiMeCl3] acquired with photon energies of (a) 22, (b) 35 and (c) 43 eV Band B shows classic Cl 3p cross-section behaviour with a very steep initial decrease and a shallow minimum reminiscent of the t1 band of TiCl4.26 The minimum at a photon energy of 42 eV is assigned to the Cl 3p Cooper minimum28 which is predicted to occur at a PE kinetic energy of ca. 30 eV.27 Band B has an i.e. of 11.55 eV so here the kinetic energy of the minimum is 30.5 eV, in excellent agreement with the prediction. Band B may be confidently assigned to ionisation from the 1a2 level which, from symmetry considerations, must be localised on the Cl pp atomic orbitals. Band C is double the intensity of B and has a very similar cross-section profile, though it shows no Cooper minimum, rather a flat profile above 40 eV.It can be assigned to the 5e level, for which a very high halogen content can be inferred. Band A at 21 eV is the least intense band but at 50 eV it is one of the most intense bands (along with F). It shows a minimum in its cross-section around 37 eV and maximum around 42 eV. From the one-electron cross-section profiles (Fig. 6) the relative rise in intensity can be attributed to Ti 3d character in the orbital from which ionisation is occurring.However the minimum is too pronounced and in the wrong region for a Cl 3p Cooper minimum. It is most likely associated with a Ti 3p æÆ 3d resonance excitation followed by super Coster– Kronig decay resulting in ejection of electrons with 3d character. 11 A cross-section modification, with a Fano profile,29,30 is expected for this complex process in the region of the Ti 3p Fig. 4 Branching ratios for bands A–H in the PE spectrum of [TiMeCl3]J. Chem. Soc., Dalton Trans., 1997, Pages 213–219 217 Fig. 5 Relative partial photoionisation cross-sections for bands A–H in the PE spectrum of [TiMeCl3] absorption edge; Ti 3p AOs ionise at 38 (2P3-2) and 39 (2P2� 1 ) eV. In a variable photon-energy study of TiCl4 the 2t2 and 1e bands were found to have a minimum at 38 eV and a maximum at 49 eV.26 Band A is thus associated with an orbital of Ti 3d character, and negligible Cl character; it may be assigned to ionisation of the 5a1 highest occupied molecular orbital (HOMO) associated with the Ti]C bond.Bands E and F show a fall in cross-section between 20 and 35 eV very similar to that of B, demonstrating their Cl 3p character. However they also show a minimum at 38 eV and a maximum around 41 eV rather than the Cooper minimum characteristic of Cl 3p ionisations. This resonance feature parallels that of band A and indicates Ti 3d character. Thus these bands show features characteristic of both Cl 3p orbitals and Ti 3d orbitals, the former being predominant.The intensity of band F suggests assignment to the 3e ionisation. The218 J. Chem. Soc., Dalton Trans., 1997, Pages 213–219 Table 4 Gross atomic charges and Mulliken populations for atomic orbitals Ti * Cl C H Orbital Population Orbital Population Orbital Population Orbital Population s pd Charge 2.08 6.31 2.34 +1.27 s pd 1.99 5.35 0.03 20.37 s pd 1.14 2.78 0.02 +0.05 s p 0.99 0.08 20.07 * Titanium populations include the 3s and 3p core electrons.behaviour of bands G and D is intermediate between that of B and C and that of E and F. Band G is, on average, approximately half the intensity of F and is assigned to the 3a1 ionisation. Assignment of bands D and E is problematic as they overlap extensively. The fitting suggests that D is somewhat more intense than E whereas the cross-section variation gives E relatively more Ti 3d character. On balance the ionisation order suggested by the calculation is probably correct, and the fitting less than ideal, so band D is assigned to the 4a1 ionisation and E to that for the 4e level.It is worth noting that e ionisations lead to orbitally degenerate states which, if of bonding character, may well be split by Jahn–Teller distortion; no account of this is taken in the transition-state ionisation calculations. The position, shape and cross-section behaviour of band H suggest that it be assigned to the C]H 2e ionisation band. It is Fig. 6 Theoretical atomic ionisation cross-sections for Ti 3d, H 1s, C 2p and Cl 3p orbitals 27 Fig. 7 Molecular orbital scheme for [TiMeCl3] the most intense band at photon energies between 30 and 40 eV; in this region the C 2p character of the orbital dominates the cross-section variation. As noted in the Experimental section, the band width is large and the band profile difficult to determine, making the intensity data less certain. The branching ratio variation is therefore less smooth than that found for other bands.Ionisation bands of C]H localised degenerate orbitals are often found to show Jahn–Teller splitting and this may also be the case for band H though, as mentioned in the Experimental section, the poor definition of the band shape means this cannot be ascertained. Within these limitations, no metallike 3p æÆ 3d resonance enhancement of the cross-section may be detected for this band suggesting that the metal character of the ionising MO is very low. Subsequent bands at 18.1 and 22.6 eV (Fig. 2) are assigned to ionisation from the methyl 2a1 orbital and the Cl 3s-based MOs (1a1 + 1e) respectively. Comparison with theory The electronic structure of [TiMeCl3] has been studied repeatedly by a number of groups.8,31–33 Indeed it has been used as a testing ground for effective core potentials and basis sets.31 All calculations give reasonable agreement with the electrondiffraction data. However none of them includes details of oneelectron energy levels or any other method of eimating an ionisation-energy ordering or the character of the ionising MO.We, therefore, undertook a density functional study to obtain a description of the bonding and to estimate i.e. These results are shown in Table 1. Though there is good agreement between several of the experimental and theoretical i.e.s, all of the mainly Cl-localised ionisations are calculated by the transition-state method to have i.e. 1–1.5 eV lower than those observed.The i.e. ordering, however, where it is independently established from the crosssection and branching ratio data, is in good agreement with that predicted. Comparison of the experimentally determined r.p.p.i.c.s. with the MO compositions in Table 1 reveals that the atomic character of the MOs is in good agreement with the crosssection variations of the related PE bands. The 26% Ti 3d contribution to the 5a1 HOMO ties in with the p æÆ d resonant enhancement of the cross-section of the associated PE band (band A) in the region of the Ti 3p subshell ionisation potentials.Of the nine mainly Cl 3p-based MOs (3a1–1a2) only the 1a2 and 5e orbitals have less than 5% Ti 3d character. The mixed Ti 3d–Cl 3p nature of the 3a1–4a1 orbitals has been discussed above. Symmetry constraints preclude any Ti 3d contribution to the 1a2 MO, and the 5e orbital also retains the nodal characteristics of the parent 1t1 ionisation in TiCl4, resulting in unfavourable overlap with the central atom.The 2e orbital, which is C]H localised, shows no sign of any significant Ti 3d content in its cross-section behaviour, in agreement with the 4% Ti 3d contribution found in the calculation. This is consistent with the now well established lack of distortion of the methyl group. Table 4 presents the gross charges on each atom. Mulliken analyses generally do not produce the formal charges assignedJ. Chem. Soc., Dalton Trans., 1997, Pages 213–219 219 by oxidation-state criteria, but the data in Table 4 indicate an appreciable difference between the charges on Ti and C, with Ti being +1.218 with respect to C.This may be taken as evidence of significant polarity in the Ti]C bond. That there is appreciable covalency in the Ti]C bond is evidenced by the atomic overlap population, which at +0.420 electron indicates that overall Ti]C interaction is significantly bonding, as is the Ti]Cl interaction (+0.457 electron).Electronic structure and chemical reactivity It is instructive to compare the MO diagram (Fig. 7) and the ionisation energies (Table 1) we have determined for [TiMeCl3] with those reported in an earlier study of TiCl4.26 Whilst direct correlation of individual MOs is precluded on account of the different symmetries, certain comparisons are valid. For TiCl4 the Ti]Cl bonding MOs lie at energies in the range 210 to 211 eV, the corresponding Ti–Cl orbitals in [TiMeCl3] being somewhat higher at 27.5 to 29.5 eV.In each molecule the lowest unoccupied molecular orbital (LUMO) consists of antibonding Ti]Cl orbitals of mainly metal character. The relatively low energy of the LUMO, 25.7 eV in TiCl4 and 23.8 eV in [TiMe- Cl3], is responsible for the Lewis-acidic nature of the titanium( IV) centre in each case, with both TiCl4 and [TiMeCl3] readily forming adducts with mono- and bi-dentate donors such as bipyridyl, ether and Me2ECH2CH2EMe2 (E = N or P),2,34–36 in which the Ti]Cl bonds are generally observed to be longer than in the parent molecule.In the case of [TiMeCl3], however, a second type of reactivity is apparent. The relatively high energy level of the HOMO (27.1 eV) [cf. TiCl4 (29.1 eV)], which corresponds to the Ti]C bonding orbital, possibly in concert with the relatively polar nature of the TiMe moiety (Table 4), leads to a high lability of the Ti]C bond. Thus oxidation of [TiMeCl3] proceeds by insertion to give [TiCl3(OMe)]; 37 the reagents HgCl2, SnCl4 and AlCl3 all exchange the methyl ligand for chloride,38 whilst treatment with protonic species results in the ready evolution of methane.37 Rupture of the Ti]C bond with evolution of methane also appears to be the predominant decomposition pathway for [TiMeCl3].Conclusion A pure sample of [TiMeCl3] may be prepared by treating TiCl4 with ZnMe2 but careful monitoring is required to ensure that the reaction goes to completion. This required a 15% molar excess of ZnMe2.The PE spectrum shows substantial intensity changes over the photon-energy range 22–50 eV which enabled complete assignment of the ion states and the character of the associated orbitals. These were in good agreement with predictions from density functional theory. The Ti]C bond was shown to be covalent but polar. The number of primary Cl 3pbased orbitals showing Ti 3d contributions supports a model with Cl 3pp donation to the Ti 3d orbitals. Acknowledgements We thank the EPSRC for financial support, the Accademia dei Lincei di Roma for a fellowship (to M.D. S.), the Royal Society for an equipment grant (to N. K.) and Jesus College, Oxford for a Research Fellowship (to G. S. M.). References 1 A. Berry, Z. Dawoodi, A. E. Derome, J. M. Dickinson, A. J. Downs, J. C. Green, M. L. H. Green, P. M. Hare, M. P. Payne, D. W. H. Rankin and H. E. Robertson, J. Chem. Soc., Chem. Commun., 1986, 520. 2 Z. Dawoodi, M. L. H. Green, V.S. B. Mtetwa, K. Prout, A. J. Schultz, J. M. Williams and T. F. Koetzle, J. Chem. Soc., Dalton Trans., 1986, 1629. 3 M. Yu. Antipin, S. I. Troyanov, Yu. T. Struchkov and L. S. Bresler, Metalloorg. Khim., 1988, 1, 111. 4 P. Briant, J. Green, A. Haaland, H. Møllendal, K. Rypdal and J. Tremmel, J. Am. Chem. Soc., 1989, 111, 3434. 5 M. L. H. Green and A. K. Hughes, J. Chem. Soc., Chem. Commun., 1991, 1231. 6 D. C. McKean, G. P. McQuillan, I. Torto, N. C. Bednall, A. J. Downs and J.M. Dickinson, J. Mol. Struct., 1991, 247, 73. 7 R. L. Williamson and M. B. Hall, J. Am. Chem. Soc., 1988, 110, 4428. 8 R. Krömer and W. Thiel, Chem. Phys. Lett., 1992, 189, 105. 9 S. Berger, W. Bock, G. Frenking, V. Jonas and F. Muller, J. Am. Chem. Soc., 1995, 117, 3820. 10 M. Basso-Bert, P. Cassoux, F. Crasnier, D. Gervais, J.-F. Labarre and P. De Loth, J. Organomet. Chem., 1977, 136, 201. 11 J. C. Green, Acc. Chem. Res., 1994, 27, 131. 12 S. Berger, W. Bock, G. Frenking, V.Jonas and F. Müller, J. Am. Chem. Soc., 1995, 117, 3820. 13 S. G. McGrady, A. J. Downs, N. C. Bednall, D. C. McKean, W. Thiel, V. Jonas, G. Frenking and W. Scherer, unpublished work. 14 J. F. Hanlan and J. D. McCowan, Can. J. Chem., 1972, 50, 747. 15 C. N. Field, D. Phil. Thesis, University of Oxford, 1995. 16 G. Cooper, J. C. Green, M. P. Payne, B. R. Dobson and I. H. Hiller, J. Am. Chem. Soc., 1987, 109, 3836. 17 ADF·1.1.4Ò, Department of Theoretical Chemistry, Vrije Universiteit, Amsterdam, 1995. 18 S. H. Vosko, L. Wilk and M. Nusair, Can. J. Phys., 1980, 58, 1200. 19 H. Stoll, C. M. E. Pavlidou and H. Preuss, Theor. Chim. Acta, 1978, 49, 143. 20 A. Becke, Phys. Rev. A, 1988, 38, 3098. 21 J. S. Slater, The Calculation of Moleclar Orbitals, Wiley, New York, 1979. 22 R. S. Mulliken, J. Chem. Phys., 1955, 23, 1833. 23 J. C. Green, M. L. H. Green, P. J. Joachim, A. F. Orchard and D. W. Turner, Philos. Trans. R. Soc. London, Ser. A, 1970, 268, 111. 24 R. G. Egdell, A. F. Orchard, D. R. Lloyd and N. V. Richardson, J. Electron Spectrosc. Relat. Phenom., 1977, 12, 415. 25 G. M. Bancroft, E. Pellach and J. S. Tse, Inorg. Chem., 1982, 21, 2950. 26 B. E. Bursten, J. C. Green, N. Kaltsoyannis, M. A. MacDonald, K. H. Sze and J. S. Tse, Inorg. Chem., 1994, 33, 5086. 27 J. Yeh, At. Data Nucl. Data Tables, 1993. 28 J. W. Cooper, Phys. Rev. Lett., 1964, 13, 762. 29 U. Fano, Phys. Rev., 1961, 124, 1866. 30 U. Fano and J. W. Cooper, Phys. Rev. A, 1965, 137, 1364. 31 V. Jonas, G. Frenking and M. T. Reetz, J. Comput. Chem., 1992, 13, 919. 32 N. Rösch and P. Knappe, ACS Symp. Ser., 1989, 394, 37. 33 R. L. Williamson and M. B. Hall, ACS Symp. Ser., 1989, 394, 17. 34 F. A. Cotton and G. Wilkinson, Advanced Inorganic Chemistry, 5th edn., Wiley-Interscience, New York, 1988, p. 657. 35 K.-H. Thiele, Pure Appl. Chem., 1992, 30, 575. 36 R. J. H. Clarke, S. Moorhouse and D. A. Stockwell, J. Organomet. Chem. Libr., 1977, 3, 223. 37 C. Beerman and H. Bestian, Angew. Chem., 1959, 71, 618. 38 E. H. Ademan, J. Polym. Sci., Polym. Symp., 1968, 16, 3643. Received 19th August 1996; Paper 6/05753E

ISSN:1477-9226    

DOI:10.1039/a605753e

出版商:RSC    

年代:1997

数据来源: RSC