摘要:

DALTON PERSPECTIVE J. Chem. Soc., Dalton Trans., 1998, 3693–3702 3693 Silole-containing Û- and �-conjugated compounds Shigehiro Yamaguchi and Kohei Tamao* Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011, Japan. E-mail: tamao@scl.kyoto-u.ac.jp Received 15th June 1998, Accepted 28th July 1998 Synthesis, properties, and application of new s- and pelectron systems consisting of the silole rings are described. A series of 2,5- and 1,1-difunctionalized siloles have been prepared based on the intramolecular reductive cyclization of diethynylsilanes.Starting from these functionalized siloles, oligo(2,5-silole)s and oligo(1,1-silole)s have been synthesized as model compounds for poly(2,5-silole)s and poly(1,1-silole)s, respectively, which are still veiled target molecules in this field. Some silole-containing p-conjugated cooligomers and copolymers with thiophene, pyrrole, and acetylene p-electron systems have also been prepared. They all have unique photophysical properties such as longwavelength absorption in the UV/VIS absorption spectra.Some silole-based p-conjugated compounds have also been found to work as new useful materials for organic electroluminescent devices. Silole (silacyclopentadiene) is a silicon-containing fivemembered cyclic diene, that is a silicon analog of cyclopentadiene. Since the first synthesis of a silole, 1,1,2,3,4,5-hexaphenylsilole, by Braye and Hübel 1 in 1959, there have been extensive studies on the synthesis, reactivities, properties and coordination abilities of such compounds to transition metals, and the aromaticity of their anionic or cationic species.2 The last two subjects are interesting in view of the comparison with cyclopentadiene and thus continue to flourish up to date.3,4 Recently, a new aspect has been added to this silole chemistry, that is the application of the silole ring as a new building unit in material science, especially for p-conjugated polymers.5,6 In 1989, Barton and his co-workers 7 reported the synthesis of “poly(2,5-silole)”, a silole 2,5-linked homopolymer, by molybdenum or tungsten-complex catalysed or thermal polymerization of diethynylsilane.Although the structure of the polymer has later been corrected to contain a methylenesilacyclobutene skeleton instead of a silole ring,8 their attempt prompted further intensive studies from a viewpoint of theoretical calculations. So far, a number of theoretical studies on silolecontaining p-conjugated polymers have been carried out,9–12 which have predicted some unique properties such as low bandgaps, non-linear optical properties, and thermochromism.However, there had been no report on the synthesis of silolebased conjugated compounds except for 2,5-diphenyl-substituted siloles until we started this research, apparently due to the lack of eYcient synthetic methods, especially for functionalized siloles. Therefore, we have commenced the development of new silole syntheses.In this account we describe our recent results on the silole-containing s- and p-conjugated compounds, focusing on the electronic structure, developments of new synthetic methodologies, and application to organic electroluminescent (EL) devices. 1 Unique electronic structure of silole ring A notable feature of the silole ring is its high electron-accepting properties, that is its low-lying LUMO level. Atwell and his coworkers 13a and O’Brien and Breeden 13b have reported experimentally that 2,5-diphenylsilole derivatives are easily reduced by alkali metals to form the corresponding di- or tetra-anion.According to our theoretical calculations,14 silole has a quite diVerent electronic structure from that of cyclopentadiene.15 Ab initio calculations at the HF/6-31G* level of theory show that, while the HOMO of the parent silole is about 0.4 eV lower than that of the parent cyclopentadiene, the LUMO level of the silole is more than 1.2 eV lower in comparison with that of cyclopentadiene (Fig. 1). The diVerence in their LUMO levels is due to the unique orbital interaction in the silole ring, as shown in Fig. 2. When the molecular orbital of silole is constructed by orbital interaction of MOs of a silylene moiety and a butadiene moiety, the low-lying LUMO of silole arises from mixture of the s* orbital of the silylene moiety with the p* orbital of the butadiene moiety, i.e., s*–p* conjugation.It should be noted that the s* orbital on the silicon and the lobes of p* orbital on the adjacent carbons are in phase. This orbital interaction occurs eVectively due to the fixed perpendicular arrangement Shigehiro Yamaguchi was born in Mie, Japan, in 1969. He graduated from Kyoto University in 1991 and received his Dr. Eng. from Kyoto University under the direction of Professor K. Tamao in 1997. Since November 1993 he has been Assistant professor at the Institute for Chemical Research, Kyoto University.His current research interests are the developments of new p-conjugated organic materials and new chiral materials using silicon as a key element. Kohei Tamao was born in Kagawa, Japan, in 1942. He received his Dr. Eng. under the direction of Professor M. Kumada from Kyoto University in 1971. He became an Assistant professor and Associate Professor at the faculty of Engineering, Kyoto University, in 1970 and 1983, respectively, and a Full Professor in 1993 at the Institute for Chemical Research, Kyoto University. He worked with Professor J.J. Eisch, State University of New York at Binghamton, for 1 year from 1973 as a postdoctoral fellow. His current research interests are organosilicon chemistry, transition metal catalysis, and p-conjugated electronic materials. Shigehiro Yamaguchi Kohei Tamao3694 J. Chem. Soc., Dalton Trans., 1998, 3693–3702 of the plane of the silylene moiety, i.e. the plane involving two exocyclic s bonds of silole, to the plane of the butadiene moiety and to the energetically comparable s* and p* orbitals.In the case of cyclopentadiene the s*–p* conjugation in the LUMO is almost negligible because of the much higher energy level of the corresponding exocyclic s* orbital. The shape of the LUMO of silole is visualized in Fig. 3, together with that of cyclopentadiene for comparison. The high electron-accepting properties of silole is further conspicuous by comparison with those of other heterocycles. 16b,17 Fig. 4 shows the comparison of the calculated HOMO and LUMO levels of silole with those of pyrrole, furan, thiophene, and pyridine, all of which are common monomer units of the conventional p-conjugated polymers. Silole has the lowest LUMO energy level among them as well as a relatively high HOMO level. We thus anticipated that the introduction of silole as a building unit would enable us to construct new s- and p-conjugated systems having unique electronic structures.Fig. 1 Relative energy levels of the HOMO and LUMO for silole and cyclopentadiene, based on the HF/6-31G* calculations. C H H Si H H De ( HOMO ) = –0.440 eV De ( LUMO ) = –1.289 eV –8.320 eV –8.760 eV 3.929 eV 2.640 eV Fig. 2 Orbital correlation diagram for 1,1-dimethylsilole, based on the PM3 calculations. CH3 CH3 Si H CH3 CH3 Si H p* ( b1 ) 2.01 eV HOMO p ( a2 ) LUMO p* ( 2b1 ) p* ( 1b1 ) p ( a2 ) s* ( b1 ) 0.16 eV 1.47 eV 0.28 eV –9.50 eV –9.15 eV Fig. 3 The LUMO of cyclopentadiene (a) and silole (b). 2 New silole synthesis The most straightforward synthetic route to silole-based pconjugated compounds may be the transition metal-catalysed coupling reaction of 2,5-difunctionalized siloles. However, it was quite diYcult to introduce the functionalities requisite for the coupling reaction, such as Br, I, SnR3, and B(OH)2, onto the 2,5 positions by the conventional synthetic methodologies. Only one example was the synthesis of 3-boryl-2,5-distannylsiloles, reported by Wrackmeyer and co-workers,18 which involved the reaction of bis(stannylalkynyl)silanes with trialkylboranes.However, this method seemed to have little generality. Under the circumstances, we have developed a new versatile methodology for the synthesis of 2,5-difunctionalized siloles based on the intramolecular reductive cyclation of diethynylsilanes.19 The addition of di(phenylethynyl)silane 1 to an excess amount (4 mol amounts)† of lithium dihydronaphthylide (LiNaph) aVords 2,5-dilithiosilole 2, as shown in Scheme 1.The key point to attain high yield is the dropwise addition of the diethynylsilane into an “electron pool” consisting of an excess amount of reductant, and thereby both acetylene moieties are Fig. 4 Relative HOMO and LUMO levels for silole and other heterocycles, based on HF/6-31G* calculations. Scheme 1 (R = alkyl or phenyl.) Si Ph Ph Li Li R R Si Ph Ph R R Si R R Ph Ph 1 THF, rt 2 LiNaph (x 4) 3 Li Li † The term “molar amount” represents the molar ratio between reactants, regardless of the stoichiometry of the given reaction, whilst the widely used “mol equivalent” should correctly be used to represent the molar ratio based on the stoichiometry.J. Chem.Soc., Dalton Trans., 1998, 3693–3702 3695 reduced simultaneously to form a bis(anion radical) intermediate 3 that undergoes radical coupling to form the 3,4-carbon– carbon bond, leaving anions at the 2,5 positions.The phenyl group at the terminal position of acetylene is essential to obtain the dilithiosiloles. In the case of other substituents such as alkyl and silyl groups only a complex mixture is formed, probably due to cleavage of the Si–Csp bond prior to the formation of the dilithiosilole. It is noted that this reaction is conceptually new from a synthetic point of view. Metal promoted intramolecular reductive cyclization of diynes is formally classified into three types with respect to the orientations of acetylene moieties to the newly formed ring, as shown in Scheme 2.20 Whereas the exo-exo mode of reductive cyclization is well known to proceed with various transition-metal two-electron reductants such as TiII, ZrII, CoI, RhI, Ni0, Pd0,21 the exo-endo mode8,22 is rare and the endo-endo mode is unknown, to the best of our knowledge.23 The present reductive cyclization using the one-electron lithium reductant, is the first example of the last mode of reaction.This present endo-endo cyclization may also be regarded as an anion analog of the Bergman cyclization, a neutral thermal cyclization of enediynes in the endo-endo mode,24 and as an intramolecular version of intermolecular coupling of diphenylacetylene with lithium to aVord dilithiobutadiene.25 By trapping with various electrophiles, 2,5-dilithiosiloles are transformed into the corresponding 2,5-difunctionalized siloles 4–8 having a series of functional groups such as SiMe3, SnBu3, Br, I and SePh, as shown in Scheme 3.19 Furthermore, some unsymmetrical functionalized siloles 9–11 can also be prepared by selective monolithiation of dibromosilole 6 with n-BuLi followed by the treatment with the appropriate electrophiles.The present cyclization is applicable to the preparation of 1,1-difunctionalized siloles, as shown in Scheme 4.26 Thus, the reaction of the diaminodiethynylsilane 12 with LiNaph cleanly proceeds at low temperature to give the 1,1-diaminosilole 13.The conventional functional group transformation reactions from 13 aVord a series of 1,1-difunctionalized siloles 14 having OR, OH, Cl, and F functionalities on the ring silicon atom. 1-Monofunctionalized siloles are also prepared by similar procedures starting from monoaminodiethynylsilanes. A series of 2,5-diarylsiloles 15 can also be synthesized in one pot from the diethynylsilanes by the combination of the present cyclization with the Pd0-catalysed cross-coupling reaction, as shown in Scheme 5.27 Thus, the intramolecular reductive cyclization of diethynylsilanes followed by quenching with the remaining lithium dihydronaphthylide with bulky chlorosilane and transmetalation with ZnCl2?tmen aVords 2,5-dizinc siloles, which are subsequently treated with the appropriate aryl bromides in the presence of palladium catalyst to give the corresponding silole derivatives 15 in high yields.Despite the versatility, the present method has a crucial limitation, that is restriction of the 3,4 substituents only to the phenyl groups as mentioned above.In order to compensate for this, we have developed quite recently two alternative routes to Scheme 2 M M M M M endo - endo exo - exo exo - endo [ M ] [ M ] [ M ] silole derivatives, as shown in Schemes 6 and 7. One is the synthesis of 3,4-unsubstituted siloles 17 from the corresponding tellurophenes 16 via the well documented tellurium–lithium exchange reaction.28,29 A variety of 2,5-diarylsiloles including unsymmetrical ones can be prepared by this method.30 The Scheme 3 Hex = hexyl = C6H13.a, Me3SiCl (4 mol amount), rt; b, Bu3SnCl (4 mol amount), rt; c, (1) Ph3SiCl (2 mol amount), 278 8C, (2) Br2 (2 mol amount), 278 8C to rt; d, ICH2CH2I (4 mol amount), 278 8C to rt; e, PhSeCl (4 mol amount), rt; f, BunLi (1.1 mol amount), diethyl ether, 278 to 0 8C; g, water, 0 8C; h, Me3SiCl, 0 8C to rt; i, Bu3SnCl, 0 8C to rt.Si Ph Ph Li Li R R Si Ph Ph Me3Si SiMe3 Me Me Si Ph Ph Bu3Sn SnBu3 Hex Hex Si Ph Ph PhSe SePh Me Me 7 64 % Si Ph Ph Br Li Et Et Si Ph Ph Br H Et Et Si Ph Ph Br SiMe3 Et Et Si Ph Ph Br SnBu3 Et Et 2 4 86 % 5 49 % 8 73 % 9 82 % Si Ph Ph Br Br R R ( R = Me, Et, Pri, Hex ) 6 44-72% a b c g i e f h Si Ph Ph I I Hex Hex d 10 79 % 11 79 % Scheme 4 i, LiNaph (4 mol amount), THF, 278 8C; ii, Me3SiCl (4 mol amount), or (MeO)2SO2 (4 mol amount). Si Ph Ph Et2N NEt2 Si Ph Ph Et2N NEt2 13 12 R = Me3Si or Me 70-83% R R Si Ph Ph X Y R R X, Y = OR, OH, Cl, F etc. 14 i, ii3696 J. Chem. Soc., Dalton Trans., 1998, 3693–3702 other route involves the preparation of 1,4-diiodobutadienes 19 by halogenolysis of the corresponding titanacyclopentadienes 18.31,32 The transformation from the diiodobutadiene to siloles via halogen–lithium exchange is a known procedure.33,34 A variety of 3,4-dialkyl and 3,4-unsubstituted siloles can be obtained by this method.These two new methods will serve complementarily with the above intramolecular reductive cyclization to give new tailor-made siloles. 3 Oligo(2,5-silole)s as model compounds of poly(2,5- silole)s Poly(2,5-silole)s may be the most interesting target molecules in this chemistry. Poly(2,5-silole) is recognized as a siliconsubstituted polyacetylene, in which the labile trans-cisoidtransoid polyacetylene backbone is fixed by the silicon bridging. In addition to this, the ring silicon would significantly perturb the p-electronic structure of the polyacetylene backbone through the s*–p* conjugation (Fig. 5).Poly(2,5-silole), thereby, would have unique properties diVerent from those of the conventional polyacetylenes. Poly(2,5-silole)s are still veiled in spite of our several Scheme 5 i, LiNaph (4 mol amount), THF, rt; ii, Ph3SiCl (2 mol amount), 278 to 0 8C; iii, ZnCl2?tmen (2 mol amount), rt; iv, aryl bromide R9Br (2 mol amount), [PdCl2(PPh3)2] (0.05 mol amount), THF, reflux.Si Ph Ph Me Me Si Ph Ph Me Me R¢ R¢ 1 15 i, ii, iii,iv Scheme 6 Te R¢¢ R¢ R¢ Li Li R¢¢ Si R¢ R¢¢ R¢¢ R¢ Me Me Li2Te Et2O THF, R¢¢OH ButLi R2SiX2 R¢, R¢¢ = 16 17 p-CF3C6H4 p-MeOC6H4 C6H5, 2-thienyl, etc. Scheme 7 R R Ti PriO OPri R R X X R R Si MeO OMe R R Ti(OPri)4 2 PriMgCl I2 (x 2) X = Br, I or Br2 (x 2) Et2O –50 °C 1) BunLi (x 2) Et2O 2) Si(OMe)4 R= SiMe3, Ph, thienyl, etc. diyne or 1-alkynes 18 19 20 attempts using 2,5-difunctionalized siloles.In the course of our studies, however, we have succeeded in the preparation of oligo(2,5-silole)s, up to the tetramer, as models of poly(2,5- silole)s, as shown in Scheme 8.19 Thus, the dibromobisilole 21 has been prepared from the 2,5-dibromosilole 6 by selective monolithiation with n-BuLi followed by oxidative homocoupling through the so-called “higher-order cuprate”.35 The Fig. 5 Si Si Si Si Si Polyacetylene ( trans-cisoid- trans-transoid) Poly(2,5-silole) Fig. 6 Crystal structure of bisilole 21.Scheme 8 i, BunLi (1.05 mol amount), Et2O; ii, CuCN (0.5 mol amount), THF; iii, tmen (1.5 mol amount); iv, p-dinitrobenzene (5 mol amount); v, ButLi (2.1 mol amount), Et2O. Si Ph Ph Br Et Et Si Ph Ph Br Et Et Si Ph Ph Br Br Et Et Si Ph Ph Br Et Et Cu(CN)Li2 Si Ph Ph Br Et Et Si Ph Ph Et Et Si Ph Ph Br Et Et Si Ph Ph Et Et 6 2 21 77% lmax 417 nm 22 16% lmax 443 nm i, ii iii, iv v, ii, iii, ivJ. Chem. Soc., Dalton Trans., 1998, 3693–3702 3697 quatersilole 22, a silole tetramer, has also been obtained by repetition of a similar procedure from dibromobisilole 21.Crystal structure analysis of 21 revealed a highly twisted arrangement of two silole rings with a 648 torsion angle, suggesting its poor p conjugation (Fig. 6). Nevertheless, bisilole is yellow and has a characteristic band at 423 nm in the UV/VIS absorption spectrum, whilst quatersilole 22 is orange and has its absorption maximum at 443 nm. The lmax value of this bisilole is significantly long among p-conjugated compounds consisting of two cyclic diene rings.We were interested in whether this long-wavelength absorption can be ascribed to the ring silicon or not. Therefore, we have prepared the bisilole 23 and its carbon analogue, bicyclopentadiene 24, and compared their UV/VIS absorption spectra (Fig. 7).36 Bicyclopentadiene 24 is colourless and has its absorption maximum at 340 nm. The diVerence in lmax between 23 and 24 on changing the central atoms from Si to C is 58 nm.Our recent theoretical study has manifested that the long-wavelength absorption of bisilole is ascribed to the low-lying LUMO energy level, due to the s*–p* conjugation in the silole ring and to the distortion of the bisilole skeleton.14 4 Oligo(1,1-silole)s as model compounds of poly(1,1- silole)s Silicon-catenated silole polymers, poly(1,1-silole)s, are other interesting target molecules in this field. Poly(1,1-silole)s are regarded as a new class of polysilanes with s*–p* conjugation, as shown in Fig. 8. Thus, s*–p* conjugation would be expected between the s* orbital delocalized over the polysilane main chain and the p*-orbital localized on the cis-butadiene moiety in every silole ring. Indeed, high electron accepting properties of poly(1,1-silole)s due to the s*–p* conjugation have been suggested by a recent theoretical study.37 We have prepared oligo(1,1-silole)s as model compounds of poly(1,1- silole)s.Using the 1,1-dichlorosilole 25 and 1-monochlorosilole 26, the silole trimer, tersilole 27, and silole tetramer, quatersilole 28, have been synthesized, as shown in Scheme 9.38 Thus, the reduction of 25 with alkali metal gave a silole dianion 4 and bisilole dianion,4c,j,k which were trapped with 26 to aVord tersilole 27 and quatersilole 28, respectively. Both oligomers have characteristic absorptions around 280–290 nm in the UV absorption spectra, which are not observed for the silole monomer and 1,1 dimer.Recently, silole homooligomers similar to ours 39 and silole-containing polysilanes 40,41 have been prepared. Fig. 7 Comparison of UV/VIS absorption maxima between the bisilole 23 and bicyclopentadiene 24. C Ph Ph H Me Me C Ph Ph H Me Me Si Ph Ph H i-Pr i-Pr Si Ph Ph H i-Pr i-Pr 23 340 (3.43) lmax /nm log e Dlmax = 58 nm 398 (3.71) vs. 24 Fig. 8 Poly(1,1-silole) and schematic representation of s*–p* conjugation in the LUMO. Si Si Si Si 5 Combination of siloles with other �-electron systems We next describe the p-electron systems consisting of silole rings and other p-conjugated rings.We are particularly interested in the combination of the electron accepting silole ring with p-electron excessive heterocycles such as thiophene and pyrrole. Introduction of the electron accepting silole rings into an electron rich polythiophene or polypyrrole p-conjugated chain would produce new p-electron systems having unique electronic structures.So far, we have prepared a series of silole–thiophene cooligomers and copolymers.16 Representative examples are listed in Table 1 together with their UV/VIS absorption spectral data. As anticipated, silole–thiophene p-electron systems show unique photophysical properties. For example, the thiophene– silole–thiophene compound, 29 has its absorption maximum at 416 nm, which is more than 60 nm longer than that of the thiophene trimer, terthiophene (lmax 353 nm).42 X-Ray structural analysis of 29 revealed high coplanarity of the three rings (torsion angles, 7.0 and 10.28), as shown in Fig. 9(a). Furthermore, the silole–thiophene 1 : 2 copolymer 32 is ink-blue in solution and has an intense broad absorption band around 600 nm, which is more than 150 nm red shifted compared with thiophene homopolymers [e.g. poly(3-hexylthiophene), lmax 442 nm Scheme 9 Si Ph Ph Me Si Ph Ph Si Ph Ph Me Si Ph Ph Cl Cl Si Ph Ph Me Me Me Cl Si Ph Ph Na Si Ph Ph Na Si Ph Ph Na Na 26 (x 1.5) 25 + + 27 8 % 28 20 % Me Me Me Me Me Me Me Me Me Me Me Me Me Me Na (x 3) THF Si Ph Ph Si Ph Ph Me Me Me Me Me Si Ph Ph Si Ph Ph Me Me Me Me Me3698 J.Chem. Soc., Dalton Trans., 1998, 3693–3702 in solution].43 In a series of silole–thiophene copolymers 32–34 having various silole : thiophene ratios, the absorption maxima tend to shift to longer wavelengths as the contents of silole increase. Ab initio calculation on 2,5-dithienylsilole has revealed that both the HOMO and LUMO are delocalized over the three rings.16b This result suggests that the long-wavelength absorption observed for silole–thiophene p-electron systems might be ascribed to the decrease in bandgaps by the introduction of the silole rings having a relatively high-lying HOMO as well as the considerably low-lying LUMO.Cooligomers of silole with the more p-electron excessive pyrrole have also been prepared, their absorption maxima being listed in Table 2.17 In contrast to the coplanar conformation of three rings in 2,5-dithienylsilole, the 2,5-dipyrrolylsilole 35 has a highly twisted conformation of the three rings (torsion angles 51.7 and 55.78) due to steric repulsion, as shown in Fig. 9(b), suggesting poorer p conjugation over the pyrrole–silole–pyrrole main chain.Nevertheless, the absorption maxima of 35 is almost same as that of 29 and about 130 nm longer than that of the pyrrole trimer N,N9,N0-trimethyl-2,29;59,20-terpyrrole (lmax 271 nm),44 showing a quite unique p-electronic structure created by the combination of silole and pyrrole.Calculation on 2,5- dipyrrolylsilole revealed a high-lying HOMO delocalized over the three rings and a low-lying LUMO mostly localized on the silole ring. The extended p-conjugated systems 36 and 37, the dimer and trimer of 35, however, show only moderate red-shifts of absorption maxima, probably due to the highly twisted conformation of the main chain.Silole–pyrrole copolymers free from steric hindrance are thus future target molecules to be challenged. Although acetylene-containing p-conjugated polymers generally have relatively large bandgaps,45 polymers consisting of silole and acetylene p-electron systems have been found to have rather narrow bandgaps.46,47 We have prepared two such types of polymers, silole–diethynylthiophene and silole–diethynylbenzene copolymers, 38 and 39, as shown in Fig. 10. Both Fig. 9 Crystal structures of the 2,5-dithienylsilole 29 (a) and 2,5- dipyrrolylsilole compounds 35 (R = Pri) (b).Fig. 10 lmax 505, 527 nm lmax 576, 605 (sh) nm 38 n 39 Si Ph Ph C6H13 C6H13 S C6H13 C6H13 Si Ph Ph C6H13 C6H13 n polymers have absorption bands at long wavelengths in the UV/ VIS absorption spectra. The absorption maximum of 38 is the longest one among poly(aryleneethynylene) type polymers reported so far. The bandgaps of 38 and 39 estimated from their absorption edges are 1.77 and 2.07 eV, respectively. 6 Application to organic electroluminescent devices As one application of silole-based p-conjugated compounds we have recently shown their possibilities as new materials for organic electroluminescent (EL) devices. Since the break- Table 1 The UV/VIS absorption spectral data for silole–thiophene cooligomers and copolymersa Compoundb Si Ph Ph TBSO OTBS S S Si Ph Ph TBSO OTBS S S S Si S TBSO OTBS Me Me S Si S TBSO OTBS Me Me S S Si S TBSO OTBS Me Me S S H H Si Ph Ph TBSO OTBS S S H H n n n 29 30 31 32 ( n » 24) 33 ( n » 27) 34 ( n » 41) 2 3 lmax/nm og e) 416 (4.27) 505 (4.86) 549 (4.96) 576 (4.49) c 618 (4.44) c 546 (4.51) c 549 (4.70) c a In chloroform.b TBS = tert-Butyldimethylsilyl. c Per monomer unit.J. Chem. Soc., Dalton Trans., 1998, 3693–3702 3699 through achieved by Tang and VanSlyke in 1987,48 who introduced a thin multilayer configuration for organic EL devices, this field has been rapidly growing because of the possible application as next-generation displays.One of the current problems in this field is a lack of eYcient electron transporting (ET) materials.49 High electron aYnity may be the first requisite for the design of new ET materials. We anticipated that the high electron accepting silole ring would work as a core component of new eYcient ET materials. We have evaluated this possibility using 2,5-diarylsiloles 15 as silole derivatives.27 Among several 2,5-diarylsiloles examined, 2,5-di(2-pyridyl)- silole PYSPY has been found to show a quite high performance as an ET material in our device having ITO/TPD/Alq/PYSPY/ Fig. 11 Organic EL device using PYSPY, Alq, and TPD as electrontransporting, emissive, and hole-transporting materials, respectively.Table 2 The UV/VIS absorption spectral data for silole–pyrrole cooligomers * Compound Si Ph Ph R R N Me N Me Si Ph Ph Et Et N Me N Me H H Si Ph Ph Et Et N Me N Me H H 35 ( R = Et ) 36 37 2 3 lmax/nm (log e) 406 (3.93) 436 (4.24) 447 (4.53) * In chloroform. Mg:Ag configuration, where triphenylamine dimer (TPD) and tris(quinolin-8-olato)aluminum (Alq) are employed as holetransporting and emissive materials, respectively, and indium tin oxide (ITO) and Mg : Ag (10 : 1) alloy are used as anode and cathode, respectively, as shown in Fig. 11. The device emits a greenish yellow light from the Alq layer. The threshold applied voltage is about 3 V and the maximum luminance reached 12 000 cd m22 at 10 V.The luminous eYciency at 100 cd m22 is 1.9 lm W21. The performance of PYSPY as an ET material exceeds that of Alq, which is one of the best ET materials reported so far. 2,5-Diarylsiloles can also be applied as eYcient emissive materials and the wavelengths of their luminescence are widely tunable by changing the 2,5-aryl groups, as shown in Fig. 12. Thus, in the devices having ITO/TPD/2,5-diarylsilole/Mg :Ag configuration, three types of silole derivatives PSP, SiTSTSi, and TTSTT work as emissive ET materials, emitting greenish blue, yellowish green, and reddish orange light, respectively.It should be noted here that about a 100 nm bathochromic shift of the emission wavelength is attained by merely changing the 2,5-aryl groups from 2-methylphenyl to bithienyl. These results suggest an easy access to various colors of light, blue to red required for application to full-color displays, by modification of only the 2,5-aryl groups on the silole ring.Advantageously, these structural modifications could readily be achieved by our one-pot synthesis shown in Scheme 5.27 7 Structure–photophysical properties relationships In view of the application of the silole p-electron systems, control of the photophysical properties and electronic structures by structural modification is relevant to further molecular design. To obtain a deeper insight into the structure–properties relationships, we have studied the eVects of the nature of the 2,5-aryl groups, 3,4 and 1,1 substituents on the properties of 2,5-diarylsiloles.A series of 2,5-diarylsiloles 40 having various p-monosubstituted phenyl groups have been prepared by the method described above.50 Their absorption and emission maximum Fig. 12 Emission wavelengths of organic EL devices using 2,5- diarylsiloles as emissive electron-transporting materials. Cell configuration: ITO/TPD(500 Å)/2,5-diarylsilole(500 Å)/Mg :Ag. Si Me Me Me Me Si Me Me S S Si Si But Ph Ph Ph Ph But Si Me Me S S S S lem / nm 488 greenish-blue yellowish-green 551 585, 602(sh) reddish-orange TTSTT SiTSTSi PSP3700 J.Chem. Soc., Dalton Trans., 1998, 3693–3702 wavenumbers in the UV/VIS absorption and fluorescence spectra are plotted as a function of the Hammett sp values of the p substituents, as shown in Fig. 13. Bell shaped lines are obtained both for absorption and emission maxima. The conjugative substituents such as NMe2 and NO2 induce significant red shifts.Worthy of note is that the absorption maxima and emission wavelengths of the 2,5-diarylsiloles can be tuned in the range of 360–420 and 470–530 nm, respectively. In Table 3 a series of 2,5-dithienylsiloles having various 3,4 substituents are listed with their maximum wavelengths in the UV/VIS absorption and fluorescence spectra.30 Comparing the 3,4-diphenylsilole 41 or bicyclic 3,4-dialkylsilole 42 with the 3,4-unsubstituted silole 43, the phenyl and alkyl substitutions induce red and blue shifts, respectively, both in the absorption and fluorescence spectra.It is also noted that the phenyl groups on the 3,4 positions reduce the quantum yield significantly. In comparison with the eVects of the 2,5-aryl groups and 3,4 substituents, the eVects of the 1,1 substituents on the optical properties are relatively small, as shown in Fig. 14.51 In a series of 2,5-disilylsiloles 44 having various groups on the ring silicon atom the absorption maxima become longer as the 1,1-substituents become more electronegative, although the changes are moderate.Considering the peculiar contribution of the central silicon atom to the p-electronic structure of silole derivatives through s*–p* conjugation, other Group 14 metalloles are also interesting. To elucidate the eVects of the central Group 14 elements, we have prepared a series of 2,5-dithienyl-substituted Group 14 metalloles from cyclopentadiene 45 to stannole 47, and their photophysical data are compared in Table 4.52 While significant diVerences exist between the cyclopentadiene and silole derivatives, the metalloles from silole to stannole show comparable absorption maxima and emission wavelengths. Theoretical calculations have revealed that the Group 14 metalloles from silole to stannole have essentially the same electronic structures and the central Group 14 elements, Si, Ge, and Sn, aVect the Table 3 EVects of 3,4 substituents on the optical properties of 2,5-dithienylsiloles UV/VISa Fluorescence a Si S S Me Me Si S S Me Me Si S S H H Me Me 42 41 43 lmax/nm (log e) 418 (4.28) 409 (4.38) 415 (4.22) lmax/nm (Ff × 102)b 515 (0.14) 492 (5.44) 505 (3.90) a In chloroform.b Quantum yields relative to quinine sulfate (0.55). LUMO energy levels to almost the same extent through s*–p* conjugation. 8 Conclusion In 1994 we developed a new synthetic method for the synthesis of 2,5-difunctionalized siloles based on the intramolecular reductive cyclization of diethynylsilanes. On the basis of this, we have succeeded in the preparation of several types of silolecontaining p- and s-electron systems, including oligo(2,5- silole)s and oligo(1,1-silole)s as models of poly(2,5-silole)s and poly(1,1-silole)s, respectively.All the new p-conjugated systems prepared show unique photophysical properties due to the unique electronic structure, especially the low-lying LUMO, of the silole ring.The s*–p* conjugation in the ring is the origin of the high electron aYnity of the silole ring. Based on this feature, a family of silole-based p-conjugated systems, 2,5- diarylsiloles, are new eYcient materials for organic electroluminescent devices. High electron aYnity may be realized in heterocyclopentadienes having electropositive atoms as the central elements, such as boron and aluminium, besides silicon.53 In view of the application as new electronic materials, however, only siloles Fig. 13 Plots of UV/VIS absorption and fluorescence maximum wavenumbers of 2,5-diarylsiloles 40 as a function of Hammett sp constants of the p substituents. Fig. 14 X = Y = H X = Y = i-Pr X = Y = Ph X = Y = OMe X = F, Y = OH X = Y = F Si Me Me X Y Me3Si SiMe3 305 (3.63) 308 (3.73) 314 (3.73) 315 (3.69) 316 (3.66) 318 (3.56) lmax / nm (log e) in CHCl3 44J. Chem. Soc., Dalton Trans., 1998, 3693–3702 3701 will be utilized due to the stability problem. Substituted siloles can be handled without any special care in the air.Further developments of new silole p-conjugated systems practically applicable are now in progress in our laboratory. 9 Acknowledgements The studies on the application to organic EL devices were carried out with Chisso Corporation. We greatly acknowledge financial support from Grant-in-Aids from the Ministry of Education, Science, Sports and Culture, Japan, Nagese Science and Technology Foundation, Ciba-Geigy Foundation (Japan) for the Promotion of Science, and the Japan High Polymer Center. 10 References 1 E. H. Braye and W. Hübel, Chem. Ind. (London), 1959, 1250; E. H. Braye, W. Hübel and I. Caplier, J. Am. Chem. Soc., 1961, 83, 4406. 2 Recent reviews: J. Dubac, A. Laporterie and G. Manuel, Chem. Rev., 1990, 90, 215; E. Colomer, R. J. P. Corriu and M. Lheureux, Chem. Rev., 1990, 90, 265; J. Dubac, C. Guerin and P. Meunier, The Chemistry of Organic Silicon Compounds, eds. Z. Rappoport and Y.Apeloig, Wiley, New York, 1998, vol. 2, in the press. Table 4 The UV/VIS absorption and fluorescence spectral data for 2,5-dithienyl metalloles a UV/VIS Fluorescence a Compound Ge S S Et Et Sn S S Me Me Si S S Ph Ph Me Me C S S Ph Ph Me Me Si S S Me Me 45 41 46 47 42 lmax/nm (log e) 368 (4.10) 418 (4.28) 409 (4.38) 405 (4.37) 428 (4.24) 406 (4.36) 430 (4.24) lmax/nm (Ff × 102)b 461 (0.996) 515 (0.141) 492 (5.44) 479 (8.72) 479 (0.495) a In chloroform. b Quantum yields relative to quinine sulfate (0.55). 3 W. P. Freeman, T. D. Tilley and A. L. Rheingold, J. Am. Chem. Soc., 1994, 116, 8428 and refs. therein. 4 (a) W.-C. Joo, J.-H. Hong, S.-B. Choi, H.-E. Son and C. H. Kim, J. Organomet. Chem., 1990, 391, 27; (b) J.-H. Hong and P. Boudjouk, J. Am. Chem. Soc., 1993, 115, 5883; (c) J.-H. Hong, P. Boudjouk and S. Castellino, Organometallics, 1994, 13, 3387; (d ) S.-B. Choi, P. Boudjouk and P. Wei, J. Am. Chem. Soc., 1998, 120, 5814; (e) B. Goldfuss and P. v. R.Schleyer, Organometallics, 1995, 14, 1553; ( f ) B. Goldfuss, P. v. R. Schleyer and F. Hampel, Organometallics, 1996, 15, 1755; (g) B. Goldfuss and P. v. R. Schleyer, Organometallics, 1997, 16, 1543; (h) R. West, H. Sohn, U. Bankwitz, C. Joseph, Y. Apeloig and T. Mueller, J. Am. Chem. Soc., 1995, 117, 11608; (i) H. Sohn, D. R. Powell, R. West, J.-W. Hong and W.-C. Joo, Organometallics, 1997, 16, 2770; ( j) W. P. Freeman, T. D. Tilley, G. P. A. Yap and A. L. Rheingold, Angew.Chem., Int. Ed. Engl., 1996, 35, 882; (k) W. P. Freeman, T. D. Tilley, L. M. Liable-Sands and A. L. Rheingold, J. Am. Chem. Soc., 1996, 118, 10457; (l) T. Wakahara and W. Ando, Chem. Lett., 1997, 1179. 5 K. Tamao and S. Yamaguchi, Pure Appl. Chem., 1996, 68, 139; S. Yamaguchi and K. Tamao, J. Synth. Org. Chem. Jpn., 1998, 56, 500. 6 Other types of silole-containing polymers: (a) R. J. P. Corriu, W. E. Douglas and Z.-X. Yang, J. Organomet. Chem., 1993, 456, 35 and refs. therein; (b) E.Toyoda, A. Kunai and M. Ishikawa, Organometallics, 1995, 14, 1089. 7 J. Shinar, S. Ijadi-Maghsoodi, Q.-X. Ni, Y. Pang and T. J. Barton, Synth. Met., 1989, 28, C593. 8 T. J. Barton, S. Ijadi-Maghsoodi and Y. Pang, Macromolecules, 1991, 24, 1257. 9 S. Grigoras, G. C. Lie, T. J. Barton, S. Ijadi-Maghsoodi, Y. Pang, J. Shinar, Z. V. Vardeny, K. S. Wong and S. G. Han, Synth. Met., 1992, 49–50, 293. 10 G. Frapper and M. Kertész, Organometallics, 1992, 11, 3178; Synth. Met., 1993, 55–57, 4255; J.Kürti, P. R. Surján, M. Kertész and G. Frapper, Synth. Met., 1993, 55–57, 4338. 11 Y. Yamaguchi and J. Shioya, Mol. Eng., 1993, 2, 339; Y. Yamaguchi, Mol. Eng., 1994, 3, 311; Y. Yamaguchi and T. Yamabe, Int. J. Quantum Chem., 1996, 57, 73; Y. Matsuzaki, M. Nakano, K. Yamaguchi, K. Tanaka and T. Yamabe, Chem. Phys. Lett., 1996, 263, 119. 12 S. Y. Hong and D. S. Marynick, Macromolecules, 1995, 28, 4991; S. Y. Hong, S. J. Kwon and S. C. Kim, J. Chem. Phys., 1995, 103, 1871; S.Y. Hong, Bull. Korean Chem. Soc., 1995, 16, 845; S. Y. Hong, S. J. Kwon, S. C. Kim and D. S. Marynick, Synth. Met., 1995, 69, 701; S. Y. Hong, S. J. Kwon and S. C. Kim, J. Chem. Phys., 1996, 104, 1140; S. Y. Hong and J. M. Song, Synth. Met., 1997, 85, 1113; Chem. Mater., 1997, 9, 297. 13 (a) E. G. Janzen, J. B. Pickett and W. H. Atwell, J. Organomet. Chem., 1967, 10, P6; (b) D. H. O’Brien and D. L. Breeden, J. Am. Chem. Soc., 1981, 103, 3237. 14 S. Yamaguchi and K.Tamao, Bull. Chem. Soc. Jpn., 1996, 69, 2327. 15 Calculations on silole rings: V. Niessen, W. P. Kraemer and L. S. Cederbaum, Chem. Phys., 1975, 11, 385; M. S. Gordon, P. Boudjouk and F. Anwari, J. Am. Chem. Soc., 1983, 105, 4972; C. Guimon, G. Pfister-Guillouzo, J. Dubac, A. Laporterie, G. Manuel and H. Iloughmane, Organometallics, 1985, 4, 636; J. R. Damewood, jun., J. Org. Chem., 1986, 51, 5028; V. N. Khabashesku, S. E. Balaji, V. Boganov, O. M. Nefedov and J.Michl, J. Am. Chem. Soc., 1994, 116, 320. See also refs. 4(e)–4(g). 16 (a) K. Tamao, S. Yamaguchi, M. Shiozaki, Y. Nakagawa and Y. Ito, J. Am. Chem. Soc., 1992, 114, 5867; (b) K. Tamao, S. Yamaguchi, Y. Ito, Y. Matsuzaki, T. Yamabe, M. Fukushima and S. Mori, Macromolecules, 1995, 28, 8668. 17 K. Tamao, S. Ohno and S. Yamaguchi, Chem. Commun., 1996, 1873. 18 B. Wrackmeyer, J. Chem. Soc., Chem. Commun., 1986, 397; J. Organomet. Chem., 1986, 310, 151; R. Köster, G. Seidel, J. Süß and B.Wrackmeyer, Chem. Ber., 1993, 126, 1107; B. Wrackmeyer, G. Kehr and J. Süß, Chem. Ber., 1993, 126, 2221. 19 K. Tamao, S. Yamaguchi and M. Shiro, J. Am. Chem. Soc., 1994, 116, 11715. 20 A recent review on acetylene oligomerization: R. Gleiter and D. Kratz, Angew. Chem., Int. Ed. Engl., 1993, 32, 842. 21 For example, N. E. Schore, in Comprehensive Organic Synthesis, eds. B. M. Trost and I. Fleming, Pergamon, Oxford, 1991, vol. 5, p. 1129; E. Negishi, in Comprehensive Organic Synthesis, eds.B. M. Trost and I. Fleming, Pergamon, Oxford, 1991, vol. 5, p. 1163. 22 H. W. Gibson, F. C. Bailey, A. J. Epstein, H. Rommelmann, S. Kaplan, J. Harbour, X.-Q. Yang, D. B. Tanner and J. M. Pochan, J. Am. Chem. Soc., 1983, 105, 4417; T. Kusumoto and T. Hiyama, Chem. Lett., 1988, 1149.3702 J. Chem. Soc., Dalton Trans., 1998, 3693–3702 23 Quite recently a titanium(III) complex promoted endo-endo mode cyclization has been reported: S. Ogoshi and J. M. Stryker, J.Am. Chem. Soc., 1998, 120, 3514. 24 R. G. Bergman, Acc. Chem. Res., 1973, 6, 25; K. N. Bharncha, R. M. Marsh, R. E. Minto and R. G. Bergman, J. Am. Chem. Soc., 1993, 115, 3120. 25 L. I. Smith and H. H. Hoehn, J. Am. Chem. Soc., 1941, 63, 1184. 26 S. Yamaguchi, R.-Z. Jin, K. Tamao and M. Shiro, Organometallics, 1997, 16, 2230. 27 K. Tamao, M. Uchida, T. Izumizawa, K. Furukawa and S. Yamaguchi, J. Am. Chem. Soc., 1996, 118, 11974. 28 T. Hiiro, N. Kambe, A. Ogawa, N. Miyoshi, S.Murai and N. Sonoda, Angew. Chem., Int. Ed. Engl., 1987, 26, 1187. 29 W. Mack, Angew. Chem., Int. Ed. Engl., 1966, 5, 896; E. Luppold, E. Müller and W. Winter, Z. Naturforsch., Teil B: Anorg. Chem., Org. Chem., 1976, 31, 1654; A. Maercker, H. Bodenstedt and L. Brandsma, Angew. Chem., Int. Ed. Engl., 1992, 31, 1339. 30 M. Katkevics, S. Yamaguchi, A. Toshimitsu and K. Tamao, submitted for publication. 31 S. Yamaguchi, R.-Z. Jin, K. Tamao and F. Sato, submitted for publication. 32 Preparation of 1,4-diiodobutadiene by the halogenolysis of zirconacyclopentadienes: E. Negishi, F. E. Cederbaum and T. Takahashi, Tetrahedron Lett., 1986, 27, 2829; E. Negishi, S. J. Holmes, J. M. Tour, J. A. Miller, F. E. Cederbaum, D. R. Swanson and T. Takahashi, J. Am. Chem. Soc., 1989, 111, 3336; S. L. Buchwald and R. B. Nielson, J. Am. Chem. Soc., 1989, 111, 2870; H. Ubayama, Z. Xi and T. Takahashi, Chem. Lett., 1998, 517. 33 A. J. Ashe III, J. W. Kampf and S. M. Al-Taweel, J.Am. Chem. Soc., 1992, 114, 372; A. J. Ashe III, S. Al-Ahmad, S. Pilotek, D. B. Puranik, C. Elschenbroich and A. Behrendt, Organometallics, 1995, 14, 2689 and refs. therein. 34 U. Bankwitz, H. Sohn, D. R. Powell and R. West, J. Organomet. Chem., 1995, 499, C7; W. P. Freeman, T. D. Tilley, L. M. Liable- Sands and A. L. Rheingold, J. Am. Chem. Soc., 1996, 118, 10457; C. Xi, S. Huo, T. H. Afifi, R. Hara and T. Takahashi, Tetrahedron Lett., 1997, 38, 4099. 35 B. H. Lipshutz, K. Siegmann, E. Garcia and F. Kayser, J. Am. Chem. Soc., 1993, 115, 9276. 36 S. Yamaguchi and K. Tamao, Tetrahedron Lett., 1996, 37, 2983. 37 Y. Yamaguchi, Synth. Met., 1996, 82, 149. 38 S. Yamaguchi, R.-Z. Jin, K. Tamao and M. Shiro, Organometallics, 1997, 16, 2486. 39 K. Kanno, M. Ichinohe, C. Kabuto and M. Kira, Chem. Lett., 1998, 99. 40 B. P. S. Chauhan, T. Shimizu and M. Tanaka, Chem. Lett., 1997, 785. 41 T. Sanji, T. Sakai, C. Kabuto and H. Sakurai, J. Am. Chem. Soc., 1998, 120, 4552. 42 J. W. Sease and L. Zechmeister, J. Am. Chem. Soc., 1947, 69, 270. 43 R. D. McCullough, R. D. Lowe, M. Jayaraman and D. L. Anderson, J. Org. Chem., 1993, 58, 904. 44 T. KauVmann and L. Hexy, Chem. Ber., 1981, 114, 3674. 45 T. Yamamoto, W. Yamada, M. Takagi, K. Kizu, T. Maruyama, N. Ooba, S. Tomaru, T. Kurihara, T. Kaino and K. Kubota, Macromolecules, 1994, 27, 6620; M. Moroni, J. L. Moigne and S. Luzzati, Macromolecules, 1994, 27, 562; M. Moroni, J. L. Moigne, T. A. Pham and J.-Y. Bigot, Macromolecules, 1997, 30, 1964. 46 S. Yamaguchi, K. Iimura and K. Tamao, Chem. Lett., 1998, 89. 47 Similar polymers have also been prepared recently: W. Chen, S. Ijadi-Maghsoodi and T. J. Barton, Polym. Prepr. (Am. Chem. Soc., Div. Polym. Chem.), 1997, 38, 189. 48 C. W. Tang and S. A. VanSlyke, Appl. Phys. Lett., 1987, 51, 913; C. W. Tang, S. A. VanSlyke and C. H. Chen, J. Appl. Phys., 1989, 65, 3610. 49 M. Strukelj, F. Papadimitrakopoulos, T. M. Miller and L. J. Rothberg, Science, 1995, 267, 1969; M. Strukelj, T. M. Miller, F. Papadimitrakopoulos and S. Son, J. Am. Chem. Soc., 1995, 117, 11976. 50 S. Yamaguchi, T. Endo, K. Tamao, M. Uchida, T. Izumizawa and K. Furukawa, 74th Annual Meeting of the Chemical Society of Japan, Kyoto, March 1997, Abstract 4A211. 51 S. Yamaguchi, R.-Z. Jin, K Tamao and M. Shiro, J. Organomet. Chem., 1998, 559, 73. 52 S. Yamaguchi, Y. Itami and K. Tamao, Organometallics, in the press. 53 A. HinchliVe and H. J. Soscun, J. Mol. Struct. (Theochem), 1995, 331, 109. Paper 8/04491K

ISSN:1477-9226    

DOI:10.1039/a804491k

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1998, 3703–3704 3703 Synthesis of a base-stabilized alumoxane: preferential hydrolysis of an aluminium–amido over an aluminium–alkyl C. Niamh McMahon and Andrew R. Barron * Department of Chemistry, Rice University, Houston, Texas 77005, USA. E-mail: arb@ruf.rice.edu; http://pchem1.rice.edu/~arb/Barron.html Received 18th August 1998, Accepted 6th October 1998 The preferential hydrolytic cleavage of an Al–N versus an Al–C bond allows for the isolation of the base stabilized alkylalumoxane, [(tBu)2Al{NH(Me)CH2CH2NMe2}]2(Ï-O), from the hydrolysis of the intra-molecularly stabilized amino–amide compound, (tBu)2Al[N(Me)CH2CH2NMe2], providing a possible general route to alkylalumoxanes.Conceptually, but not experimentally, the simplest route to alkylalumoxanes (compounds of the general formulae [(R)Al(O)]n and [R2Al–O–AlR2]n) involves the reaction of water with a trialkylaluminium compound.1 Reacting water (or ice) 2 with an aromatic or aliphatic hydrocarbon solution of a trialkylaluminium will yield an alkylalumoxane, however, it is important to control the temperature of this highly exothermic reaction both as a safety precaution 3 and in order to maximize the yield and ensure the solubility of the products.4 In an eVort to control the rate at which the water reacts with the trialkylaluminium, several researchers have employed hydrated salts, such as Al2(SO4)3?14H2O or CuSO4?5H2O, as “indirect hydrolysis” sources,5 since the water of crystallization in a hydrated salt reacts at a vastly decreased rate as compared to dissolved “free” water.While a number of alternative routes have also been investigated,6 none is of generic application and the hydrolysis of trialkylaluminium compounds remains the method of preference. It would be desirable, however, to develop a more general approach to alkylalumoxanes in order to study their structure and reactivity.We have previously observed that in the presence of a heteroatom donor ligand (e.g., alkoxide, aryloxide, amide, etc.) the basicity (reactivity) of an aluminium alkyl group is significantly reduced.7 For example, reaction of [Me2Al(m-NH2)]3 with HOAr (Ar = C6H2- But 2-2,6-Me-4) results in the formation of Me2Al(OAr)(NH3).8 Based on these results it is reasonable to propose that alkylalumoxanes may be prepared through the hydrolysis of alkylaluminium amides, alkoxides, etc. The intra-molecularly stabilized amino–amide compound (tBu)2Al[N(Me)CH2CH2NMe2] I 9 is a stable non-pyrophoric solid which undergoes slow hydrolysis resulting in the essentially stoichiometric formation of [(tBu)2Al{NH(Me)CH2CH2- NMe2}]2(m-O).† The molecular structure of [(tBu)2Al{NH- (Me)CH2CH2NMe2}]2(m-O) has been confirmed by X-ray crystallography,‡ and may be described as a base stabilized tetraalkylalumoxane. Pasynkiewicz and co-workers have reported that the partial hydrolysis of AlMe3 in the presence of N,N,N9,N9-tetramethylethylenediamine (TMEDA) gave a base stabilized tetramethylalumoxane II in low yield, however, no structural information was obtained.10 Subsequently, we have reported a similar synthesis for the first example of a structurally characterized tetraalkylalumoxane, [(tBu)2Al(py)]2(m-O) III.11 The molecular structure of [(tBu)2Al{NH(Me)CH2CH2- NMe2}]2(m-O) is shown in Fig. 1. The molecule exists as a dimer consisting of two (tBu)2Al{NH(Me)CH2CH2NMe2} moieties linked by a single oxygen atom bridge, such that the amine ligands are in a staggered anti conformation, see Fig. 2. Although not constrained by crystal symmetry, as was observed for [(tBu)2Al(py)]2(m-O),11 the Al(1)–O(1)–Al(2) angle in [(tBu)2- Al{NH(Me)CH2CH2NMe2}]2(m-O) is close to linear [173.0(4)8], precluding its assignment as a bridging hydroxide or water. The Al–O distances [1.690(7) and 1.714(7) Å] are comparable to those found for [(tBu)2Al(py)]2(m-O) [1.710(1) Å].11 It is worth noting that these Al–O distances are within the range observed for oxo-bridged complexes that contain two five-coordinate aluminium atoms [1.679(2)–1.713(5) Å] in which the Al–O–Al angle varies between 152.0(3)8 and 1808.12 The infrared spectrum of [(tBu)2Al{NH(Me)CH2CH2NMe2}]2(m-O) shows a strong asymmetric Al–O–Al stretch at 1035 cm21.This is consistent with a linear Al2O linkage by comparison to the stretches observed for structurally characterized compounds [L2Al]2(m-O), L = 2-methyl-8-quinolinolato (997 cm21), L2 = phthalocyanato (1051 cm21), or N,N9-ethylenebis(salicylideneiminato) (1067 cm21).12 The diamine ligands in [(tBu)2Al{NH(Me)CH2CH2NMe2}]2- (m-O) adopt a configuration that allow hydrogen bonding between the secondary amine’s hydrogen atom and the tertiary amine nitrogen.A similar configuration was observed in (tBu)3- Al[NH(Me)CH2CH2NMe2] and (tBu)3Al[NH(Me)CH2CH2- CH2NMe2].13 The N ? ? ? N distances [2.87, 2.94 Å] and N– H? ? ? N angles [110, 1148] in [(tBu)2Al{NH(Me)CH2CH2- NMe2}]2(m-O) are similar to those in (tBu)3Al[NH(Me)CH2- CH2NMe2] and (tBu)3Al[NH(Me)CH2CH2CH2NMe2].13 The hydrolytic protonation of the amide nitrogen, rather than one of the tert-butyl groups, follows our previous observ-3704 J.Chem. Soc., Dalton Trans., 1998, 3703–3704 ations that the presence of a heteroatom donor ligand (e.g., alkoxide, aryloxide, amide, etc.) significantly reduces the basicity of the aluminium alkyl group.14 Thus, the reaction of a Brönsted acid occurs via protonation of the hetero-atom [eqn.(1)] and not the alkyl group [eqn. (2)].15 [R2Al(X)]n 1 n– 2 H2O æÆ n– 2 [R2Al–O–AlR2]n 1 n HX (1) [R2Al(X)]n 1 n– 2 H2O æÆ n– 2 [R(X)Al–O–Al(X)R]n 1 n RH (2) Although alkylalumoxanes are ordinarily formed via the hydrolysis of trialkylaluminium compounds, with the concomitant liberation of the corresponding alkane, hydrolysis of readily prepared dialkylaluminium amides (and alkoxides) oVers an alternative and milder synthesis to a variety of alkylalumoxane structures.We are presently using this method to obtain additional information into the structure of alkylalumoxanes. Fig. 1 Molecular structure of [(tBu)2Al{NH(Me)CH2CH2NMe2}]2- (m-O). Thermal ellipsoids shown at the 30% level, and only the amine hydrogens are shown for clarity. Selected bond lengths (Å) and angles (8): Al(1)–O(1) 1.690(7), Al(2)–O(1) 1.714(7), Al(1)–N(11) 2.053(8), Al(2)–N(21) 2.047(9), Al–C 2.00(1)–2.02(1); Al(1)–O(1)–Al(2) 173.0(4), O(1)–Al(1)–N(11) 100.8(3), O(1)–Al(2)–N(21) 101.6(4), O(1)–Al–C 112.6(4)–114.2(4).Fig. 2 The aluminium coordination sphere in [(tBu)2Al{NH(Me)- CH2CH2NMe2}]2(m-O) viewed along the Al(1)–Al(2) vector. The N(11)–Al(1)–Al(2)–N(21) torsion angle = 1608. Thermal ellipsoids shown at the 30% level, and hydrogen atoms are omitted for clarity. Acknowledgements Financial support for this work is provided by the Robert A.Welch Foundation. A. R. B. is indebted to the Alexander Von Humboldt Foundation for a Senior Scientist Award and to Professor H. W. Roesky for his hospitality. Notes and references † A solution of (tBu)2Al[N(Me)CH2CH2NMe2] was dissolved in hexane and exposed to moist air. Colorless crystals (ca. 1.0 g) resulted upon cooling to 223 8C. Yield: ª90%. IR (Nujol mull, KBr plates, cm21): 3329w, 2695m, 1613w, 1589w, 1570w, 1359s, 1383s, 1261s, 1188s, 1035s, 931m, 889m, 806m, 759m. 1H NMR (Bruker AM-250, C6D6): d 3.25 (4 H, m, NCH2), 2.35 [6 H, d, J(H–H) = 6.2 Hz, N(CH3)], 2.14 (4 H, m, NCH2), 1.89 [12 H, s, N(CH3)2], 1.37 [18 H, s, C(CH3)3], 1.33 [18 H, s, C(CH3)3]. ‡ Crystal data for [(tBu)2Al{NH(Me)CH2CH2NMe2}]2(m-O): C26H64- Al2N4O, M = 502.8, monoclinic, space group P21/n, a = 15.096(3), b = 14.919(3), c = 15.337(3) Å, b = 91.41(3)8, U = 3453(1) Å3, Z = 4, Dc = 0.967 g cm23, T = 298 K, m(Mo-Ka) = 13.29 cm21, F(000) = 1128, R = 0.0489, Rw = 0.0504 for 1177 independent observed reflections [|Fo| > 6.0s|Fo|, 4.0 £ 2q £ 40.08] and 298 parameters, largest residual = 0.18 e Å23.CCDC reference number 186/1190. 1 A. R. Barron, in Properties & Technology of Metallocene-Based Polyolefins, ed. W. Kaminsky and J. Scheirs, Wiley, Chichester, 1998. 2 H. Winter, W. Schnuchel and H. Sinn, Macromol. Symp., 1995, 97, 119. 3 G. B. Sakharovskaya, N. N. Korneev, A. F. Popov, Yu. V. Kissin, S. M. Mezhkovskii and E. Kristalanyi, Zh.Obshch. Khim., 1969, 39, 788. 4 C. J. Harlan, M. R. Mason and A. R. Barron, Organometallics, 1994, 13, 2957. 5 G. A. Razuvaev, Yu. A. Sangalov, Yu. Ya. Nel’kenbaum and K. S. Minsker, Izv. Akad. Nauk SSSR, Ser. Khim., 1975, 2547. 6 K. Ziegler, Angew. Chem., 1956, 68, 721; M. Boleslawski, S. Pasynkiewicz, K. Jaworski and A. Sadownik, J. Organomet. Chem., 1975, 97, 15; R. J. Wehmschulte and P. P. Power, J. Am. Chem. Soc., 1997, 119, 8387; W. Uhl, M. Koch, W. Hiller and M. Heckel, Angew.Chem., Int. Ed. Engl., 1995, 34, 989; N. Ishihara, D.Phil. Thesis, Oxford University, 1990; J. Storre, C. Schnitter, H. W. Roesky, H.-G. Schmidt, M. Noltemeyer, R. Fleischer and D. Stalke, J. Am. Chem. Soc., 1997, 119, 7505. 7 M. D. Healy, M. B. Power and A. R. Barron, Coord. Chem. Rev., 1994, 130, 63. 8 M. D. Healy, J. T. Leman and A. R. Barron, J. Am. Chem. Soc., 1991, 113, 2776. 9 C. N. McMahon, J. A. Francis, S. G. Bott and A. R. Barron, in the press. 10 A. Sadownik, S. Pasynkiewicz, M. Boleslawski and H. Szachnowska, J. Organomet. Chem., 1978, 152, C49. 11 M. R. Mason, J. M. Smith, S. G. Bott and A. R. Barron, J. Am. Chem. Soc., 1993, 115, 4971. 12 Y. Kushi and Q. Fernando, Chem. Commun., 1969, 555; K. J. Wynne, Inorg. Chem., 1985, 24, 1339; P. L. Gurian, L. K. Cheatham, J. W. Ziller and A. R. Barron, J. Chem. Soc., Dalton Trans., 1991, 1449; D. Rutherford and D. A. Atwood, Organometallics, 1996, 15, 4417. 13 C. N. McMahon, S. G. Bott and A. R. Barron, J. Chem. Soc., Dalton Trans., 1997, 3129. 14 M. D. Healy, M. B. Power and A. R. Barron, Coord. Chem. Rev., 1994, 130, 63. 15 M. D. Healy, J. T. Leman and A. R. Barron, J. Am. Chem. Soc., 1991, 113, 2776. Communication 8/06502K

ISSN:1477-9226    

DOI:10.1039/a806502k

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1998, 3705–3706 3705 Structure and magnetic properties of MnII[N(CN)2]2(pyrazine). An antiferromagnet with an interpenetrating 3-D network structure Jamie L. Manson,a Christopher D. Incarvito,b Arnold L. Rheingold b and Joel S. Miller *a a Department of Chemistry, University of Utah, 315 S. 1400 E. RM Dock, Salt Lake City, UT 84112-0850, USA. E-mail: jsmiller@chemistry.utah.edu b Department of Chemistry, University of Delaware, Newark, DE 19716, USA Received 6th October 1998, Accepted 7th October 1998 Mn[N(CN)2]2(pyz) (pyz 5 pyrazine) orders antiferromagnetically at low temperature and possesses intralayer Ï-NCNCN and interlayer Ï-pyz ligands that form a pseudo-ReO3 interpenetrating network structure.The synthesis of multidimensional network structures is at the forefront of modern research due to their ability to design as well as control a wide range of architectures.1 Likewise, the study of molecule-based magnets due to their potential for exhibiting cooperative magnetic behavior is being widely investigated.2 Polydentate cyanocarbons have been utilized extensively to assemble transition metals into 1-, 2- and 3-D arrays.3 Tetracyanoethylene, TCNE, has been used to link Mn(porphyrin) into 1-D chains 4 and when reacted with V(C6H6)2 yields a 3-D polymeric ferrimagnet with a critical temperature far exceeding room temperature.5 Work has focused on diamagnetic [N(CN)2]2 due to its ability to bond to multiple transition metal sites.6 Tricoordinate dicyanamide forms rutile-structured ferromagnets with CoII and NiII with Tc’s ranging from 9 K (Co) to 21 K (Ni) while isostructural MnII orders antiferromagnetically below 16 K.7,8 In addition to M[N(CN)2]2 complexes, octahedral complexes of M[N(CN)2]2- L2 (L = Lewis base) stoichiometry can be prepared.Owing to the polydentate character of [N(CN)2]2 numerous structural motifs can be constructed. Herein we report the single crystal structure and magnetic properties of MnII[N(CN)2]2(pyz) (pyz = pyrazine). Reaction of MnCl2, Na[N(CN)2], and pyrazine in H2O– EtOH results in the formation of small pale yellow crystals of MnII[N(CN)2]2(pyz)† whose structure was solved by X-ray diVraction.‡ The structure consists of infinite MNCNCNMlinked Mn[N(CN)2]2 layers bridged by pyrazine aVording pseudo-cubic frameworks, Fig. 1, similar to ReO3. Furthermore, owing to the combination of the large separation between Mn atoms and the small ligand sizes, large cavities are formed which can accommodate a second interpenetrating lattice.Each octahedral MnII is bonded to four diVerent [N(CN)2]2 ligands in the ab-plane and two diVerent pyrazine bridges along c. Each [N(CN)2]2 is m-bonded to two MnII’s through the terminal CN’s. The MnII octahedron is tetragonally elongated from Oh symmetry with Mn–N distances ranging from 2.173(7) Å (dicyanamide N’s) to 2.299(9) Å (pyrazine N’s) and average 2.236 Å while cis-N–Mn–N9 bond angles range from 83.5(3) to 92.3(6)8.The dicyanamide ligand displays nearly ideal C2v symmetry with C]] ] N bond distances averaging 1.145 Å typical for this ligand.9 The C]] ] N–Mn bond angles deviate appreciably from linearity and range from 142.6(9) to 164.9(13)8. The intranetwork Mn ? ? ? Mn separations are 7.351 (through the pyrazine bridge), 8.678, and 8.803 Å, which exceed the shortest Mn? ? ? Mn internetwork separation of 6.282 Å.For comparison, Zn[N(CN)2]2 features a 2-D layered structure with only m-N]] ] C linkages similar to Mn[N(CN)2]2(pyz), however due to the tetrahedral ZnII centers, the layers are markedly buckled and pack in a staggered fashion.10 The pyrazine ligands reside in noncoplanar orientations with a dihedral angle of 43.18 relative to the “cube” faces. Thermogravimetric analysis reveals a sharp weight loss at ª230 8C corresponding to the loss of one pyrazine per formula unit (Calc. 30.0; obs. 29.9). To the best of our knowledge this is the only structurally characterized unsubstituted pyrazine MnII complex. Several 2-D materials such as Co(pyz)2(NCS)2 feature m-pyz ligands that organize paramagnetic metal centers into square grids.11 Interestingly, the only example of a 3-D network solid consisting of pyz bridges is diamagnetic [Ag(pyz)3][SbF6] which also possesses a ReO3-like structure.12 The 2 to 300 K temperature dependence of the magnetic susceptibility, c, of Mn[N(CN)2]2(pyz) was measured and fit by the Curie–Weiss expression, c µ (T 2 q)21, with g = 2.01 and q = 23.6 K indicative of finite antiferromagnetic coupling between the MnII metal sites, Fig. 2. At 300 K the eVective moment is 5.90 mB, in excellent agreement with the expected value (5.92 mB) for isolated S = 5/2 MnII ions and due to antiferromagnetic coupling decreases at lower temperature. A similar material, Mn[N(CN)2]2(py)2, also has m-NCNCN bridges and weaker antiferromagnetic coupling is observed (q = 21.8 K) suggesting enhanced spin coupling via the pyrazine linkages. 13 To elucidate the exchange coupling through the NCNCN and pyz linkages, c was also fit to a 2-D (c2D) antiferromagnet model derived by Rushbrooke and Wood14a with g = 2.01 and J/kB = 20.18(1) K.14b To account for the residual 3-D interactions an additional mean-field correction (cMF) 14c,d was included, eqn. (2), also with g = 2.01 and J9/kB = 20.21(1) K. Fig. 1 Stereoview of the crystal structure of MnII[N(CN)2]2(pyz) illustrating the interpenetrating pseudo-ReO3 frameworks.3706 J.Chem. Soc., Dalton Trans., 1998, 3705–3706 c2D = 2.91Ng2mB 2 kBT [1 1 C1x 1 C2x2 1 C3x3 1 C4x4 1 C5x5 1 C6x6] (1) cMF = c2D [1 2 c2D(2zJ9/Ng2mB 2)] (2) J is assigned to coupling within the layers via the NCNCN bridges and J9 is assigned to coupling between the layers via the pyrazine bridges. The zero field splitting is typically negligible for high spin MnII 15 and is ignored.Evidence of long-range antiferromagnetic ordering is demonstrated by a cusp in M(T) at 2.7 K, Fig. 3. The actual magnetic ordering temperature occurs just below the maximum and can be determined from a plot of dcT(T)/dT, Fig. 3 inset.16 Additionally, zero-field and field-cooled magnetization experiments carried out in small applied magnetic fields (H < 50 G) fail to show bifurcation unlike a-Mn[N(CN)2]2.8 Field-dependent magnetization measurements performed at 2 K to 5 T demonstrate behavior typical of an ordered antiferromagnet.The magnetization rises nearly linearly to approximately 19 000 emu Oe mol21 (at 3 T) and then decreases reaching a final value of 26 600 emu Oe mol21 (at 5 T). This value is only slightly less than the expected value of 27 925 emu Oe mol21 expected for S = 5/2 MnII. Acknowledgements The authors gratefully acknowledge the ACS-PRF (Grant Fig. 2 Temperature dependence of and eVective magnetic moment (meff) and the reciprocal molar magnetic susceptibility (c21) for MnII- [N(CN)2]2(pyz).The data was fit to the expression derived by Rushbrooke and Wood14a for a 2-D antiferromagnet (——) with S = 5/2, g = 2.01 and J/kB = 20.18 K. Interlayer exchange was determined to be J9/kB = 20.21 K. A low temperature comparison to the Curie–Weiss law (×) with g = 2.01 and q = 23.6 K is also shown (inset). Fig. 3 Zero-field and field-cooled magnetization as a function of temperature for MnII[N(CN)2]2(pyz) taken in a 50 Oe applied dc magnetic field on warming.TN = 2.5 K as determined from the plot of dcT(T)/dT, inset. #30722-AC5) and the U. S. Department of Energy (Grant #DEFG03- 93ER45504) for support of this work. Notes and references † A 5 mL aqueous solution of MnCl2?4H2O (1.7 mmol, 0.3373 g) was mixed with a 1 : 1 H2O–EtOH solvent mixture (10 mL) containing Na[N(CN)2] (3.4 mmol, 0.3034 g) and pyrazine (1.7 mmol, 0.1360 g) aVording immediate precipitation of a pale yellow powder (90%).Small crystals suitable for X-ray diVraction were grown from the filtrate solution upon standing at room temperature for 2 weeks. nCN (Nujol): 2170s, 2180s, 2193s (sh), 2236m, 2248m, 2311m, 2325m and 2357w cm21. ‡ Crystal data for C8H4MnN8: M = 267.13, monoclinic, P21/n, a = 7.3514(11), b = 16.865(2), c = 8.8033(12) Å, b = 90.057(2)8, U = 1091.4(3) Å3, Z = 4, Dc = 1.626 Mg m23, m(Mo-Ka) = 1.199 cm21, T = 198(2) 8C. Of 4518 data (4 < 2q < 578), 1556 were independent (Rint = 0.0928), and 1019 were observed [I > 2s(I)].Two nitrogen atoms in two diVerent cyano groups were positionally disordered 70 : 30 and 60 :40. CCDC reference number 186/1201. See http://www.rsc.org/ suppdata/dt/1998/3705/ for crystallographic files in .cif format. 1 T. Soma, H. Yuge and T. Iwamoto, Angew. Chem., Int. Ed. Engl., 1994, 33, 1665; L. Carlucci, G. Ciani, D. M. Proserpio and A. Sironi, Chem. Commun., 1996, 1393; T. Otieno, S. J.Rettig, R. C. Thompson and J. Trotter, Inorg. Chem., 1993, 32, 1607; K. A. Hirsch, D. Venkataraman, S. R. Wilson, J. S. Moore and S. Lee, J. Chem. Soc., Chem. Commun., 1995, 2199; B. F. Hoskins and R. Robson, J. Am. Chem. Soc. 1990, 112, 1546. 2 C. Mathonière, C. J. Nuttall, S. G. Carling and P. Day, Inorg. Chem., 1996, 35, 1201; S. Ferlay, T. Mallah, R. Ouahes, P. Veillet and M. Verdaguer, Nature (London), 1995, 378, 701; K. Inoue, T. Hayamizu, H. Iwamura, D. Hashizume and Y.Ohashi, J. Am. Chem. Soc., 1996, 118, 1803; H. Stumpf, L. Ouahab, Y. Pei, D. Grandjean and O. Kahn, Science, 1993, 261, 447; F. Lloret, M. Julve, R. Ruiz, Y. Journaux, K. Nakatani, O. Kahn and J. Sletten, Inorg. Chem., 1993, 32, 27. 3 J. L. Manson, C. Campana and J. S. Miller, J. Chem. Soc., Chem. Commun., 1998, 251; O. Ermer, Adv. Mater., 1991, 3, 608; X. Ouyang, C. Campana and K. R. Dunbar, Inorg. Chem., 1996, 35, 7188. 4 A. Böhm, C. Vazquez, R. S. McLean, J. C. Calabrese, S.E. Kalm, J. L. Manson, A. J. Epstein and J. S. Miller, Inorg. Chem., 1996, 35, 3083. 5 J. M. Manriquez, G. T. Yee, R. S. McLean, A. J. Epstein and J. S. Miller, Science, 1991, 252, 1415. 6 H. Köhler, A. Kolbe and G. Lux, Z. Anorg. Allg. Chem., 1977, 428, 103; J. Mrozinski, M. Hvastijova and J. Kohout, Polyhedron, 1992, 11, 2867. 7 J. L. Manson, C. Kmety, Q. Huang, J. Lynn, G. Bendele, S. Pagola, P. W. Stephens, A. J. Epstein and J. S. Miller, Chem. Mater., 1998, 10, 2552. 8 J. L. Manson, C. Kmety, Q. Huang, J. Lynn, A. J. Epstein and J. S. Miller, unpublished work. 9 Y. M. Chow, Inorg. Chem., 1971, 10, 1938; D. Britton and Y. M. Chow, Acta Crystallogr., Sect. B, 1977, 33, 607; D. Britton, Acta Crystallogr., Sect. B, 1990, 46, 2297; Y. M. Chow and D. Britton, Acta Crystallogr., Sect. B, 1975, 31, 1934; I. Potocnak, M. Dunaj- Jurco, D. Miklos and J. Jager, Acta Crystallogr., Sect. C, 1996, 52, 1653; I. Potocnak, M. Dunaj-Jurco, D. Miklos, M. Kabesova and J. Jager, Acta Crystallogr., Sect. C, 1995, 51, 600. 10 J. L. Manson, D. W. Lee, A. L. Rheingold and J. S. Miller, submitted. 11 F. Lloret, G. De Munno, M. Julve, J. Cano, R. Ruiz and A. Caneschi, Angew. Chem., Int. Ed. Engl., 1998, 37, 135. 12 L. Carlucci, G. Ciani, D. M. Proserpio and A. Sironi, Angew. Chem., Int. Ed. Engl., 1995, 34, 1895. 13 J. L. Manson, A. M. Arif, L. Liable-Sands, C. D. Incarvito, A. L. Rheingold and J. S. Miller, unpublished work. 14 (a) G. S. Rushbrooke and P. J. Wood, J. Mol. Phys., 1963, 6, 409; (b) x = J/(kBT), N = Avogadro’s number, mB = Bohr Magneton, g = Lande g value, C1 = 23.33, C2 = 147.78, C3 = 405.45, C4 = 8171.3, C5 = 64968 and C6 = 15811; (c) B. E. Myers, L. Berger and S. A. Friedberg, J. Appl. Phys., 1968, 40, 1149; (d ) z = number of nearest neighbors. 15 R. L. Carlin, Magnetochemistry, Springer-Verlag, New York, 1986, p. 64. 16 M. E. Fisher, Am. J. Phys., 1964, 32, 343. Communication 8/07788F

ISSN:1477-9226    

DOI:10.1039/a807788f

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1998, 3707–3709 3707 Solid state coordination chemistry: two-dimensional oxides constructed from polyoxomolybdate clusters and copper–organoamine subunits Douglas Hagrman,a Claudio Sangregorio,b Charles J. O’Connor b and Jon Zubieta *a a Department of Chemistry, Syracuse University, Syracuse, NY 13244, USA b Department of Chemistry, University of New Orleans, New Orleans, LA 70148, USA Received 7th August 1998, Accepted 7th October 1998 Copper–organodiamine substructures are effective bridging groups for polyoxomolybdate anions in the construction of two-dimensional mixed metal networks, of which [{Cu(bpe)}4(·-Mo8O26)]?2H2O and [{Cu(pyrd)}4(„-H4Mo8- O26)] are representative [bpe 5 1,2-bis(4-pyridyl)ethylene; pyrd 5 pyridazine]. The structural influence of organic molecules on inorganic oxide microstructures has been demonstrated in four families of materials: zeolites,1,2 mesoporous phases of the MCM-41 class,3 biomineralized materials 4 and transition metal–oxide–phosphate compounds or TMPO’s.5,6 We have recently extended this concept to the molybdenum oxides by introducing the organic component as part of a transition metal complex subunit, complex cation or complex coordination polymer.7–9 A structural characteristic common to several of these organic–inorganic composite materials is the presence of octamolybdate [Mo8- O26]42 clusters as fundamental building blocks of one-, two- or three-dimensional covalently linked solids.Since the heterometal –organoamine substructure serves to link the molybdate clusters through {Mo–O–M9} bridges, the overall structure of the oxide phase reflects the coordination preferences of the heterometal and the geometry of the ligand, as manifested both by donor group orientation and spacer length and topology. As part of our continuing program in the synthesis and structural characterization of organic–inorganic oxide composite materials, we are exploring the influences of ligand geometries on the inorganic microstructures. In a previous communication, 7 structures incorporating the rigid rodlike ligand 4,49- bipyridine (4,49-bpy) were reported.The donor group distance may be readily lengthened by inserting a spacer between pyridine donors, as in 1,2-bis(4-pyridyl)ethylene (bpe), or may be diminished by incorporating the nitrogen donors into the same ring, as in pyridazine (pyrd). This expedient provides two new members of this family of molybdenum oxides, [{Cu(bpe)}4- (Mo8O26)]?4H2O 1 and [{Cu(pyrd)}4(H4Mo8O26) 2.The hydrothermal reaction of Cu(NO3)2?2.5H2O, MoO3, bpe, and water in the mole ratio 1 : 1.39 : 1.72 : 2470 at 200 8C for 25.5 h produced small orange crystals of 1 in 40% yield. Similarly, the reaction of CuSO4?5H2O, MoO3, pyridazine and water in the mole ratio 1:1:1.26 :1690 at 200 8C for 48 h yielded black rhombs of 2 in 85% yield. The infrared spectrum of 1 displayed features at 813 and 840 cm21 attributed to n(Mo– O–Mo) and strong bands at 910 and 922 cm21 associated with n(Mo]] O).In contrast, the infrared spectrum of 2 exhibited a complex pattern of ten bands in the 670–940 cm21 range, including strong bands at 945, 939, 897 and 888 cm21 attributed to n(Mo]] O) for the presence of both Mo(V) and Mo(VI) centers. The structure of 1,† illustrated in Fig. 1, consists of a-[Mo8O26]42 clusters 10 linked by {Cu(bpe)}n n1 chains into a two-dimensional sheet.Each cluster employs the terminal oxogroups of the two capping tetrahedral {MoO4}units to bridge to the {Cu(bpe)}n n1 chains. Each of these oxo-groups bridges two copper sites, one from each of two parallel polymeric chains propagating between pairs of clusters. This arrangement results in a {Cu2O2} rhomb linking pairs of clusters. The interlamellar region between the [{Cu(bpe)}2(Mo8- O26)]n 2n2 sheets is occupied by space filling and chargecompensating {Cu(bpe)}1 chains, running parallel to the chains of the layer networks.The result is the common pattern of alternating oxide anion layers and “organic” cation layers.11 Fig 1 (a) A view of the {a-Mo8O26}42 unit linked to four adjacent {Cu(bpe)}1 chains in 1. Copper atoms are large dark spheres; molybdenum atoms are large lighter spheres. (b) A view of the [{Cu(bpe)}2- (Mo8O26)]22 sheets. Molybdenum polyhedra are shown in yellow; copper are large blue spheres; nitrogen atoms are small green spheres; oxygen atoms are red spheres.Selected bond lengths (Å): Cu1–N, 1.88(1) and 1.90(1); Cu2–N, 1.920(9) and 1.93(1); Cu2–O, 2.442(8) and 2.461(8); tetrahedral Mo-site Mo–O, 1.77(1) (average); octahedral Mo-sites Mo–O, 1.70(1) (average) × 2, 1.91(1) (average) × 2, 2.44 (average) × 2, (H4Mo8O26).3708 J. Chem. Soc., Dalton Trans., 1998, 3707–3709 The structure contrasts dramatically with that of the analogous 4,49-bpy solid, [{Cu(4,49-bpy)}4(Mo8O26)].7 This latter material displays d-[Mo8O26]42 clusters entrained in a matrix of {Cu(4,49-bpy)}n n1 polymer chains, disposed in layers of parallel chains with perpendicular chains intervening between layers and molybdate clusters.The incorporation of pyridazine in place of bpe has dramatic Fig. 2 (a) A view of the [{Cu(pyrd)}4(H4Mo8O26)] unit of 2. Copper atoms are large dark spheres; molybdenum atoms are large lighter spheres. (b) The packing of chains in the ac plane, color coded as for Fig. 1(b). Selected bond lengths (Å): Cu(1)–N, 1.990(7) and 2.002(6); Cu(1)–O, 2.146(6) and 2.171(6); Cu(2)–N, 1.989(7) and 1.968(7); Cu(2)–O, 2.056(6) and 2.268(6); octahedral Mo-sites: Mo1–O1, 1.697(8); Mo1–O2, 1.758(5); Mo1–O9, 1.957(5); Mo1–O5, 1.962(8); Mo–O10, 2.141(5) and 2.404(5); Mo2–O7, 1.700(6); Mo2–O12, 1.718(8); Mo2–O8, 1.904(5); Mo2–O5, 2.025(5); Mo2–O10, 2.277(5); Mo2–O9, 2.411(5); Mo(3)–O3, 1.713(6); Mo3–O13, 1.729(5); Mo3–O6, 1.912(8); Mo3–O9, 1.996(5); Mo3–O5, 2.325(5); Mo3–O10, 2.354; Mo4–O11, 1.751(5); Mo4–O1, 1.709(6); Mo4–O8, 1.923(6); Mo4–O6, 1.928(8); Mo4–O2, 2.225(5). The average valence sum for the Mo-sites is ca. 5.5, while those for the g-Mo8O26 42 cluster of ref. 13 are 16.0. consequences on both the inorganic microstructure and the properties of the material [{Cu(pyrd)}4(H4Mo8O26)] 2 shown in Fig. 2.‡ In this instance, the clusters adopt the g-molybdate structure with six six-coordinate and two five-coordinate Mo sites.Each molybdate cluster bonds to four {Cu2(pyrd)2} units, which are present in the form of tetranuclear {Cu4O6(pyrd)4} clusters. The copper clusters consist of pairs of oxo-bridged copper tetrahedra which are linked through four pyridazine ligands, in such a fashion as to generate a Cu4 box of dimensions 3.25 × 3.02 Å with p-stacked pyridazine rings. Each {Cu4O6- (pyrd)4} cluster links a molybdate cluster to three neighboring molybdate units. The resultant two-dimensional structure may be described in terms of the corner-sharing of polyhedra from two distinct cluster types.The crystals of 2 are black, indicative of mixed valence. Valence sum calculations 12 confirm that the average oxidation state of the Mo sites is 15.5, rather than 16 for the fully oxidized form.13 Similarly, valence sum calculations on the Cu sites provide an average oxidation state of 11.0, suggesting that the components of 2 may be described as [Cu4(pyrd)4]41 and [H4Mo8O26]42. Charge compensation is achieved by protonation of the triply-bridging and quadruply-bridging oxogroups, which exhibit valence sums of 1.00 to 1.50 in the absence of protonation.The occurrence of a reduced form for any isomeric type of an octamolybdate cluster is unexpected since reduced clusters are observed exclusively for “naked” polyanion aggregates which are constructed from polyhedra with one terminal oxo-group, classified as type I.14 While the “naked” g-{Mo8O26}n2 cluster is a type II polyanion, and consequently exhibits irreversible reduction, the molybdenum oxide component of solid phase 2 exhibits covalent bonding to the copper sites through six terminal oxo-groups, rendering the cluster, in a sense, type I.Alternatively, the reduced form of the cluster may be considered to be stabilized by covalent linkage to the cationic copper–pyridazine clusters which provide charge delocalization. It is also noteworthy that the valence sum calculations indicate that the four additional cluster electrons of the {H4Mo8O26}42 units are not localized on specific sites but rather delocalized throughout the cluster.Magnetic susceptibility studies of 2 indicate that the material is eVectively diamagnetic at room temperature, with a transition below 14 K to a ferromagnetic or canted antiferromagnetic state. The isolation of the title compounds demonstrates that discrete clusters may be exploited as building blocks in the synthesis of two-dimensional networks.15 The exploitation of hydrothermal conditions requires a shift in paradigm from the thermodynamic to the kinetic, such that equilibrium phases are replaced by structurally more complex metastable phases.16 The structure-directing role of the organic component is manifest in the copper coordination complex cationic components which interact with the anionic molybdate clusters in a geometric correspondence which produces the architecture of the network.While it may be premature to classify such synthesis as “designed”, it should be noted that preformed clusters or conditions favoring cluster aggregation are required for the preparation of such materials. Acknowledgements The research was supported by NSF Grant CHE 9617232. Notes and references † Crystal data for C24H24Cu2Mo4N4O15 (1): M = 1758.05, triclinic, P1� , a = 10.5793(1), b = 13.1590(2), c = 13.5431(3) Å, a = 106.86(2), b = 100.885(1) g = 96.035(1)8, U = 1639.25(5) Å3, Z = 2, Dc = 2.268 g cm23, T = 293(2) K, m = 4.812 mm21; structure solution and refinement based on 7038 reflections converged at R1 = 0.0722, wR2 = 0.1294. ‡ Crystal data for C16H20Cu4Mo8N8O26 (2): M = 1119.31, triclinic, P1� , a = 9.8995(4), b = 9.9102(3), c = 10.6930(4) Å, a = 89.093(1), b = 72.909(1), g = 72.650(1)8, U = 954.13(6) Å3, Z = 1, Dc = 3.060 g cm23, T = 293(2) K, m = 2.833 mm21; structure solution and refinement based on 4237 reflections converged at R1 = 0.0579, wR2 = 0.1517.CCDC reference number 186/1200.J. Chem. Soc., Dalton Trans., 1998, 3707–3709 3709 1 J. V. Smith, Chem. Rev., 1988, 88, 149. 2 M. L. Occelli and H. C. Robson, Zeolite Synthesis, American Chemical Society, Washington, DC, 1989. 3 C. T. Kresge, M. E. Leonowicz, W. J. Roth, J. C. Vartuli and J. S. Beck, Nature (London), 1992, 359, 710. 4 S. Mann, Nature (London), 1993, 365, 499; S. Mann. S. L. Burkett, S. A. Davis, C. E. Fowler, N.H. Mendelson, S. D. Sims, D. Walsh and N. T. Whilton, Chem. Mater., 1997, 9, 2300. 5 R. C. Haushalter and L. A. Mundi, Chem. Mater., 1992, 4, 31. 6 M. I. Khan, L. M. Meyer, R. C. Haushalter, C. L. Schweitzer, J. Zubieta and J. L. Dye, Chem. Mater., 1996, 8, 43. 7 D. Hagrman, C. Zubieta, D. J. Rose, J. Zubieta and R. C. Haushalter, Angew. Chem., Int. Ed. Engl., 1997, 36, 873. 8 P. J. Zapf, C. J. Warren, R. C. Haushalter and J. Zubieta, Chem. Commun., 1997, 1543. 9 D. Hagrman, R.C. Haushalter and J. Zubieta, Chem. Mater., 1998, 10, 361. 10 M. T. Pope, Heteropoly and Isopoly Oxometalates, Springer, New York, 1983. 11 G. Huan, A. J. Jacobson, J. W. Johnson and E. W. Corcoran, Jr., Chem. Mater., 1990, 2, 91. 12 I. D. Brown and K. K. Wu, Acta Crystallogr., Sect. B., 1976, 32, 1957. 13 M. L. Niven, J. J. Cruywagen and B. B. Heyns, J. Chem. Soc., Dalton Trans., 1991, 2007. The valence sums for the Mo sites of this fully oxidized cluster, using the same parameters as those for 2 given in ref. 12, result in an average Mo oxidation state of 16.0. 14 M. T. Pope, Inorg. Chem., 1972, 11, 1973. 15 For other examples of cluster linkage into extended arrays see E. V. Anokhine, M. W. Essig and A. Lachgar, Angew. Chem., Int. Ed. Engl., 1998, 37, 522; A. Kitamura, T. Ozeki and A. Yagasaki, Inorg. Chem., 1997, 36, 4275; I. Loose, M. Bösing, R. Klein, B. Krebs, R. P. Schulz and B. Scharbert, Inorg. Chim. Acta, 1997, 263, 99 and refs. therein; J. R. D. DeBord, R. C. Haushalter, L. M. Meyer, D. J. Rose, P. J. Zapf and J. Zubieta, Inorg. Chim. Acta, 1997, 256, 165; J. R. Gálan-Mascaios, C. Giménez-Saig, S. Triki, C. J. Gómez-Garcia, E. Coronado and L. Ouahab, Angew. Chem., Int. Ed. Engl., 1995, 34, 1460. 16 J. Gopalakrishnan, Chem. Mater., 1995, 7, 1265. Communication 8/06

ISSN:1477-9226    

DOI:10.1039/a806234j

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1998, 3711–3713 3711 A gadolinium cryptate with two coordinated water molecules S. W. Annie Bligh,*a Michael G. B. Drew,*b Noreen Martin,c Beatrice Maubert cd and Jane Nelson cd a School of Biological and Applied Sciences, University of North London, Holloway Rd, UK N7 8DB b Chemistry Dept., Reading University, Whiteknights, Reading, UK RG6 2AD c School of Chemistry, Queens University, Belfast, UK BT9 5AG d Chemistry Dept., Open University, Milton Keynes, UK MK7 6AA Received 27th July 1998, Accepted 12th October 1998 An X-ray crystallographic structure determination of the nitrate salt of the gadolinium imBT cryptate shows coordination of two water molecules; NMRD relaxometry of this cryptate reveals a relaxivity of 5.8 mM21 s21 (at 10 MHz, 298 K and pH 6), which is pH sensitive over the range 4–9. Complexes of lanthanide cations are in general characterised by high lability in aqueous solution; therefore specially designed hosts are needed to achieve the kinetic stability required for biomedical applications.Polydentate chelates such as diethylenetriaminepentaacetic acid (DTPAH5) 1 and 1,4,7,10- tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTAH4) 2 have proved valuable in preventing the release of toxic gadolinium( III) aqua ions under physiological conditions when used as hosts for gadolinium as contrast agents in magnetic resonance imaging (MRI).3 Magneto-pharmaceutical products developed for MRI so far are mostly anionic or neutral Gd(III) complexes e.g.Gd(DTPA)22, trade-named MAGNEVIST; Gd(DOTA)2, DOTAREM; or the related compounds Gd(DTPA-BMA) {DTPA-BMA = HO2CCH2N[(CH2)2N(CH2CO2H)(CH2CONHMe)] 2}, OMNISCAN; and Gd(HPDO3A) [HPDO3A = 10-(2- hydroxypropyl)-1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid], PROHANCE. Cationic complexes exist which are known to have relaxivity greater than [Gd(H2O)9]31 (10 MHz, 298 K); these are macrocyclic complexes such as 4–6 [Gd(porphyrin)]1, [Gd(texaphyrin)]21, and [Gd(N6-tetraimine)]31.In these cases, the Gd31 ion is above the macrocyclic cavity and exposed to coordination with either water molecules or anions. In cryptates, however, the metal ion is present within the cavity and the water exchange process will diVer from that in macrocyclic or chelate complexes. Given the significance of symmetry in relation to the mechanism of electronic relaxation 7 it is important to examine the relaxivity of any gadolinium cryptates which can be synthesised.To date the strategy of using the cryptate effect 8 to achieve the desired kinetic stability for biomedical applications of lanthanides has been barely exploited. Lehn’s polyether cryptand hosts have insuYcient coordinating power to compete with solvent O-donors, and while N-donors prove unexpectedly good donors for lanthanide cations,9 many existing azacryptand ligands lack the appropriate geometry to eYciently coordinate these relatively large cations.However, the [2 1 3] SchiV-base condensation route to azacryptands 10,11 oVers a range of new hosts including some with good potential for coordination of lanthanide cations. The small iminocryptand generated by this method 10 using tris(2-aminoethyl)amine and the 2-carbon dialdehyde, glyoxal, (imBT) provides a suYciently large cavity to ensure good fit of the heavier main group12 or lanthanide cations. In earlier studies of the hexaimino cryptand imBT we observed unusual kinetic stability 12,13 for transition and main group ions encapsulated in mononuclear fashion within the hexaimine cage; this appears to protect both cation and ligand in that the ligand also seems to be stabilised against the metal-assisted hydrolysis of C]] N bonds which normally aVects SchiV-base complexes of Lewis-acid cations.Complexation of lanthanide cations is easily achieved by treating a solution of the ligand, imBT, with the metal salt,† under anhydrous conditions. As for other imBT cryptates so far isolated, apart from disilver 14 or dicopper salts,15 the lanthanide cryptates are obtained as monuclear complexes. The lanthanide cryptates La[imBT][ClO4]3 1 and [Gd- (imBT)(H2O)2][NO3]3?MeCN 2 need to be made in dried MeCN.Once formed, however, they do not appear to be susceptible to hydrolysis, as they can be recrystallised without deterioration, and treatment with basic aqueous solution (ª1 M NaOH) fails to cause precipitation on standing over a period of weeks, as does the addition of phosphate, even at acidic pH (4.5).Such chemically robust behaviour can, like the observation of satellites in the NMR spectra of the heavy metal cryptates,12 be attributed to kinetic stability against decomplexation, an unusual and potentially valuable property in Gd(III) complexes.16 The structure of a single crystal of [Gd(imBT)(H2O)2][NO3]3? 2H2O 29 obtained by recrystallisation from MeCN–MeOH‡ has been solved by X-ray crystallography, and is seen to consist of discrete cations (Fig. 1), nitrate anions and two solvent water molecules. The metal ion is bonded to six nitrogen atoms of the macrobicycle and two water molecules; the nitrate counter ions are uncoordinated. The Gd–Nimino distances are somewhat longer (2.60 vs. 2.57 Å) on the strands adjacent to coordinated waters. The Gd–Owater distances lie toward the short end of the normal range;11,17 Fig. 2 illustrates the siting of the water ligands within the cryptand host. The distances from the metal to the bridgehead nitrogens are too long to represent more than very weak interactions. The demonstrated 8-coordination of the gadolinium(III) cation might be expected to ensure an associative 18 water-exchange process, more rapid than the dissociative exchange normally encountered. In comparison with the free ligand system where axial and equatorial signals are frozen out in the methylene 1H NMR spectrum at ambient temperatures and below, that of La[imBT]31 in CD3CN indicates a fully mobile conformation consisting of a pair of triplets illustrating equivalence of the HB/HC and HD/HE pairs due to rapid interconversion of con- figurations on the 1H NMR time scale throughout the fluid range of the deuteroacetonitrile solvent.The gadolinium cryptate 2 fails, as expected, to exhibit any ligand spectrum; the only signals to be seen are those of solvate molecules.Preliminary investigation of relaxivity of gadolinium cryptates 19 at 500 He Hd Hc Hb Ha imBT N N N N N N N N3712 J. Chem. Soc., Dalton Trans., 1998, 3711–3713 MHz indicates that it is faster than 2 mM s21 at this frequency. In order to quantify relaxivity at the low frequencies normally quoted, we have examined the relaxation rates of the water solvent molecules by an NMRD study § over the frequency range 0.1–100 MHz. At 10 MHz, pH 6 and 298 K, the proton relaxivity of 2 obtained from a plot of relaxation rate against complex concentration, is 5.8 mM21 s21.The relaxivity is sensitive to pH change and it reduces to 3.5 at pH 9. The magnetic field dependence of the proton relaxivities (Fig. 3) was fitted to the modified Solomon–Bloemergen–Morgan (SBM) theory20 by assuming that parameters established in our X-ray study apply in solution: i.e., hydration number, q = 2, and distance of the metal from first coordination sphere protons, r = 3 Å.By extrapolation, the closest distance to the water protons in the second Fig. 1 Crystal structure of the cation in 29 together with atomic numbering scheme; ellipsoids at 30% probability. Selected distances (Å) Gd–N(6C,3A,3C) 2.563(8)–2.569(9); Gd–N(6A,6B,3B) 2.600(11)– 2.608(8); Gd–O 2.434(6), 2.466(7) Å, Gd ? ? ? N(100), Gd ? ? ? N(200) 2.973(9), 2.982(8). Fig. 2 Space-filling model of 2 illustrating siting of coordinated water: colours; gadolinium light blue, nitrogen blue, oxygen red, carbon green, hydrogen yellow.coordination sphere was estimated as d = 4 Å, and this, along with the parameters tv (correlation time for electron relaxation) set at 18 ps, diVusion coeYcient, Ddiff, of 2.5 × 1025 cm2 s21, and static zero field splitting D(ZFS) = 0, was fitted in the final fitting procedure. The values of D (the average quadratic transient zero field splitting), tm (chemical exchange time) and tr (rotational correlation time) obtained from the NMRD profile are 0.033 cm21, 4.18 ms and 71 ps respectively and they are typical values of low molecular mass Gd(III) complexes.The rate of water exchange obtained from the SBM fitting calls for comment. As the inner-sphere exchange mechanism is generally considered to dominate the relaxation process, it might be expected that the presence of two coordinated water molecules would give rise to enhanced relaxivity. However, the value of 4.18 ms obtained for the rate of water exchange is slower than for comparable negatively charged or neutral complexes; a trend noted earlier 21 by Parker and co-workers. It seems likely that as in this earlier case,21 exchange of coordinated water molecules is not the major relaxation mechanism; instead, prototropic exchange arising from the relatively high acidity of water coordinated to the Gd(III) cation is the dominant mechanism.Potentiometric titration shows22 a pKa of around 8, associated with deprotonation of the coordinated water.Above this pH, the complex is in the hydroxo form where inner-sphere water exchange is no longer possible; the fall oV in relaxivity with increasing pH supports this hypothesis. We plan to carry out variable temperature 17O NMR transverse relaxation measurements as a function of pH to further investigate this behaviour. Although the tendency of positively charged gadolinium complexes to localise in negatively charged e.g. bone or membrane tissue 23 means that they are rarely utilised as contrast agents, the relaxivities reported here are promising.Together with the unusually high kinetic stability deriving from the cryptate eVect, they warrant a full investigation of the relaxation behaviour of these cryptates to allow comparison with other gadolinium complexes currently in use as contrast agents. The possibilities for substitution on the cryptand skeleton to generate e.g. charge-neutral derivatives or biological conjugates makes these systems additionally attractive.Acknowledgements Thanks to University of Reading and EPSRC for funds for the Image Plate system and access to FAB-MS service at Swansea; to OURC for support (BM); to Mr A. Johans (University of Reading) for assistance with crystallography; to European Union, TMR-LSF contract No. ERBFMGECT950033 for financial support (S. W. A. B.). Notes and references † The lanthanide cryptates 1, 2 were prepared as follows: to a solution of 1 mmole of imBT prepared as described 24,25 elsewhere in 20 cm3 of Fig. 3 NMRD profiles, experimental and theoretically fitted, of the [Gd(imBT)(H2O)2]31 complex at 298 K (j) and at 310 K (d); calculated outer-sphere contribution to the NMRD profile at 298 (- - - - - - -).J. Chem. Soc., Dalton Trans., 1998, 3711–3713 3713 dry acetonitrile and enough CHCl3 to aid dissolution of the ligand, was added 1.2 mmole of the appropriate lanthanide salt in 20 cm3 dry CH3CN under N2 atmosphere.Upon removal of the solvent (rotary evaporation or standing in air) a white microcrystalline solid was obtained. This could be recrystallised from acetonitrile–methanol; crystals of 29 used for crystal structure determination, were obtained in this way. 1 FAB-MS: m/z 695(100); 596(65); % C,H,N (calc. values in parentheses): 27.2(27.9); 3.8(3.8); 13.7(14.1). 2 FAB-MS: m/z 640(14); 658(5); 577(46); 595(35); % C,H,N (calc. values in parentheses): 30.8(30.8); 4.8(4.8); 21.6(21.6).Yields of recrystallised samples: 1, 20%; 29, 30%. Safety note: although all perchlorates must be treated as potentially explosive, and the quantities indicated in the syntheses described should not be exceeded, we experienced no problems in working with complex 1 in the manner described. ‡ Crystal data: C18H38GdN11O13, M = 773.84, orthorhomic, space group Pn21a; a = 15.798(12), b = 14.100(12), c = 13.736(12) Å; U = 3060(4) Å, Z = 4, Dm = 1.680 Mg m23, F(000) = 1564, m = 2.244 mm21, T = 293 K, largest diVerential peak and hole 2.131, 21.582 e Å23 situated close to the Gd atom.Data were collected on a Marresearch Image Plate system using Mo-Ka radiation. 95 frames were collected using 2 min per frame and 8254 reflections were collected up to 2q of 508 of which 4545 were unique, Rint = 0.0372. The structure was refined to an R1 of 0.0422, wR2 = 0.1299 for 3911 data with I > 2s(I). All calculations were carried out on a Silicon Graphics R4000 Workstation at the University of Reading.CCDC reference number 186/1198. See http:// www.rsc.org/suppdata/dt/1998/3711/ for crystallographic files in .cif format. § Relaxation measurements of 2 were carried out on samples in the concentration range 0–25 mM at pH 6, 298 K. pH studies were carried out in tris(hydroxymethyl)aminoethane (0.3 M) solution and titrated with aqueous HCl (6 M). All NMRD profiles were accquired on the Stelar FFC relaxometer from 0.00024 to 0.36 T (0.01–15 MHz). The profiles are theoretically fitted using a computer program which calculates the paramagnetic enhancements due to inner and outer sphere contributions, and takes into account both dipolar and contact relaxation, as well as zero-field splitting, g anisotropies and hyperfine coupling, if any.26 The paramagnetic contribution of the water relaxivity of the Gd(III) cryptate has been calculated by subtracting the values of water proton relaxation rates, 0.38 mM21 s21. 1 M. Mangerstadt, M. V. Brechbiel and O. A. Gansow, Magn. Reson. Med., 1986, 3, 808. 2 M. F. Lonchin, J. F. Desreux and E. Merciny, Inorg. Chem., 1986, 25, 2646; S. H. Koenig, G. Baglin and R. D. Brown III, Magn. Reson. Med., 1984, 1, 496. 3 L. Vanderelst, Y. Vanhaverbeke, J. F. Goudemant and R. N. Muller, Magn. Reson. Med., 1994, 31, 437. 4 R. B. LauVer, Chem. Rev., 1987, 87, 901; V. Alexander, Chem. Rev., 1995, 95, 273. 5 C. F. G. C. Geraldes, A. D. Sherry, P. Vallet, F. Maton, R.N. Muller, T. D. Moody, G. Hemmi and J. L. Seessler, Magn. Reson. Imaging, 1995, 5, 725. 6 S. W. A. Bligh, N. Choi, W. J. Cummins, E. G. Evagoru, J. D. Kelly and M. McPartlin, J. Chem. Soc., Dalton Trans., 1994, 3369. 7 J. A. Peters, J. Huskens and D. J. Raber, Prog. Nucl. Magn. Reson. Spectrosc., 1996, 28, 283. 8 J.-M. Lehn and J.-P. Sauvage, J. Am. Chem. Soc., 1975, 97, 6700. 9 D. E. Fenton, U. Castellato, R. A. Vigato and M. Vidali, Inorg. Chim. Acta, 1984, 95, 187. 10 J. Nelson, V. McKee and G. Morgan, Prog. Inorg. Chem., 1997, 47, 169. 11 M. G. B. Drew, O. W. Howarth, C. J. Harding, N. Martin and J. Nelson, J. Chem. Soc., Chem. Commun., 1995, 903. 12 D. Apperley, J. Coyle, B. Maubert, N. Martin, V. McKee, J. Nelson, S. Coles and W. Clegg, J. Chem. Soc., Dalton Trans., in the press. 13 J. Hunter, J. Nelson, C. J. Harding and M. McCann, J. Chem. Soc., Chem. Commun., 1990, 1148. 14 J. L. Coyle, V. McKee and J. Nelson, Chem. Commun., 1998, 709. 15 C. J. Harding, V. McKee and J. Nelson, J. Am. Chem. Soc., 1991, 113, 9684. 16 S. H. Koenig and R. D. Brown III, Prog. Nucl. Magn. Reson. Spectrosc., 1991, 22, 487. 17 C. Allen Chang, H. G. Brittain, J. Telser and M. F. Tweedle, Inorg. Chem., 1990, 29, 4468; C. K. Schauer and O. O. Anderson, J. Chem. Soc., Dalton Trans., 1989, 185. 18 J. Xu, S. J. Franklin, D. W. Whisenhunt and K. N. Raymond, J. Am. Chem. Soc., 1995, 117, 7245. 19 S. W. A. Bligh, N. Martin, B. Maubert and J. Nelson, unpublished work. 20 I. Solomon, Phys. Rev., 1955, 99, 559; N. Bloembergen, J. Chem. Phys., 1957, 27, 572; N. Bloembergen and L. O. Morgan, J. Chem. Phys., 1961, 34, 842. 21 S. Aime, A. Barge, M. Botta, D. Parker and A. S. de Sousa, J. Am. Chem. Soc., 1997, 119, 4767; J. Hall, R. Hamer, S. Aime, M. Botta, S. Faulkner, D. Parker and A. S. de Sousa, New. J. Chem., 1998, 22, 627. 22 R. M. Town and B. Maubert, unpublished work. 23 W. D. Kim, G. E. Kiefer, F. Maton, K. McMillan, R. N. Muller and A. D. Sherry, Inorg. Chem., 1995, 34, 2233. 24 J. L. Coyle, PhD Thesis, Open University, 1998. 25 G. Baranovich, J. L. Coyle, C. Coates, A. alObaidi, V. McKee, J. J. McGarvey and J. Nelson, Inorg. Chem., 1998, 37, 3567. 26 I. Bertini, O. Galas, C. Luchinat and G. Parigi, J. Magn. Reson., Ser. A, 1995, 113, 151. Communication 8/05859H

ISSN:1477-9226    

DOI:10.1039/a805859h

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, 3715–3720 3715 EVects of anions on the solid state structures of linear gold(I) complexes of the type (o-xylyl isocyanide)gold(I) (monoanion) Holger Ecken,a Marilyn M. Olmstead,a Bruce C. Noll,b Saeed Attar,a Bruce Schlyer a and Alan L. Balch *a a Department of Chemistry, University of California, Davis, California 95616, USA. E-mail: albalch@chem.ucdavis.edu b Department of Chemistry, University of Colorado, Boulder, Colorado 80309, USA Received 2nd July 1998, Accepted 21st September 1998 The preparation, spectroscopic, and structural characterization of four gold(I) complexes, (o-xylylNC)AuX with X as I, Br, Cl or CN, are reported.Each crystallizes in a unique, solvent-free form with varying aurophilic interactions between the linear, two-coordinate molecules. Thus, (o-xylylNC)AuCl forms a simple dimer, while the bromo and iodo analogs form slightly kinked chains with extended Au ? ? ? Au ? ? ? Au ? ? ? units.The bromo complex diVers from the iodo complex due to the fact that an independent, non-interacting (o-xylylNC)AuBr unit lies oV to the side of the linear chain. The structure of (o-xylylNC)AuCN consists of a complex grid which involves kinked chains of gold atoms cross linked by another aurophilically connected triad of gold centers. The complexes are all luminescent at room temperature in solution and in the solid state. Introduction Recent revelations concerning the luminescence properties of gold(I) complexes 1 and 2, which undergo supramolecular aggregation via attractive intermolecular AuI ? ? ? AuI interactions, suggest that the gold compounds capable of forming extended linear aggregates deserve further attention.1,2 Specifically, complex 1, which forms trigonal prismatic columns through Au ? ? ?Au interactions, displays solvoluminescence.1 The colorless complex, after irradiation with near UV light, produces a yellow luminescence when brought into contact with organic solvents.Complex 2 is known to crystallize in colorless and orange forms.2 The orange form contains linear arrays of the dimeric complex and displays luminescence at ca. 630 nm. Exposure of the colorless, solvate free crystals to organic vapors produces marked changes in both the absorption and emission spectra. Both phenomena, solvoluminescence and solvochromism, have potential for use as chemical sensors. Two-coordinate Au(I) complexes with Au ? ? ?Au separations less than 3.6 Å in the solid state are considered to experience attractive aurophilic interactions.3–6 Theoretical work has revealed that this weakly bonding interaction is the result of correlation eVects which are enhanced by relativistic eVects.7–10 The strength of this attractive interaction has been experimentally determined, on the basis of barriers to free rotation, to be ca. 7–11 kcal mol21.11,12 Such aurophilic interactions have been shown to be suYciently strong to persist in solution and to play a role in guiding a chemical reaction.13 Theoretical studies by Pyykkö and co-workers 7,8 predicted an increase in the strength of this aurophilic interaction for the H3PAuX system in the series of anions (X) with F < CH3 < H < Cl < CN <Br < I < SCH3.In our laboratory this trend has been confirmed in C Au N C N Au C Au N Me O OMe O Me S Au S C S Au S C R2 N NR 2 Me Me Me 1 2 the compounds (Me2PhP)AuX (X = Cl, Br, I) where the Au(I) ? ? ? Au(I) contacts decrease in the order Cl > Br > I.14 A similar trend has been seen for the pair of complexes LAuX (L = 1,3,5-triaza-7-phosphaadamantane, X = Cl, Br).15 However, with phosphine ligands, bulky substituents on the phosphorus atoms can restrict association of molecules of the type (R3P)AuX, but with smaller phosphines dimers, trimers and extended chains can form.14,16,17 Polymeric chains and networks of such dimers can form when diphosphines are used as ligands.18,19 Here we report on the structural and spectroscopic properties of gold complexes of the type (o-xylylNC)AuX.The relatively flat nature of the isocyanide ligand was expected to provide an environment that would not inhibit self association of the complex, yet was a relatively easily handled and stored ligand. Moreover, isocyanides are precursors to 1 and analogous compounds, 20 and knowledge of the structural chemistry in this area is significant for further exploration of the chemistry of these trinuclear complexes.Earlier studies of (RNC)AuCl and related complexes revealed some tendency of these to associate through Au ? ? ?Au contacts, but in many cases the separations between the gold centers were longer than 3.6 Å.21–23 On the basis of our previous studies,14 we felt that the aurophilic attractions could be enhanced by alteration of the anions. Results Synthetic and spectroscopic studies Treatment of a chloroform solution of (Ph3As)AuCl with one equivalent of o-xylyl isocyanide results in the formation of (o-xylylNC)AuCl which has been obtained as a white crystalline solid.Colorless crystals of (o-xylylNC)AuBr and pale yellow crystals of (o-xylylNC)AuI were prepared similarly. Addition of o-xylyl isocyanide to a suspension of gold(I) cyanide in chloroform results in the formation of (o-xylylNC)AuCN also as white crystals. These complexes have good solubility in dichloromethane and chloroform but are insoluble in diethyl ether and methanol.Attempts to prepare two-coordinate complexes of the type [(o-xylylNC)2Au]1 or three-coordinate complexes of the types (o-xylylNC)2AuX and [(o-xylylNC)3Au]1 by treatment of (Ph3As)AuX with up to a ten-fold excess of o-xylyl isocyanide3716 J. Chem. Soc., Dalton Trans., 1998, 3715–3720 Table 1 Spectroscopic data 1H NMRb Compound (o-xylylNC) (o-xylylNC)AuI (o-xylylNC)AuBr (o-xylylNC)AuCl (o-xylylNC)AuCN Infrared a n(N]] ] C)/cm21 2117.5 2198.4 2204.2 2215.8 2156.0 (2223.5) d d (ppm) C–H 7.12d, 7.19t 7.18d, 7.37t 7.19d, 7.37t 7.20d, 7.32t 7.21d, 7.39t d (ppm) Me 2.41s 2.44s 2.44s 2.44s 2.44s Luminescence c lmax/nm 415 420, 500 420, 500 420, 510 430, 500 a Taken as Fluorolube mulls between NaCl plates.b Taken in chloroform-d solutions with SiMe4 as reference. c Solid state at 23 8C. d Vibration of the coordinated cyanide anion. were unsuccessful. Only the neutral, two-coordinate complexes (o-xylylNC)AuX were isolated from the reaction medium.Spectroscopic data for the new compounds are given in Table 1. The 1H NMR spectra naturally resemble those of the parent free ligand, but in the complexes the doublet and triplet which are due to the m- and p-phenyl protons, respectively, are more widely separated in chemical shift. The infrared spectra of the complexes as Fluorolube mulls show that the isocyanide stretching frequencies decrease in energy in the order Cl > Br > I > CN in accord with expectations from backbonding.For (o-xylylNC)AuCN the band at 2156.0 cm21 is assigned to the isocyanide stretch while that at 2223.5 cm21 is assigned to the coordinated cyanide ion. The electronic spectra of the four complexes and of o-xylyl isocyanide itself are shown in Fig. 1. Significant absorption is seen for the complexes only in the region of ligand absorption. This is not surprising, since spectroscopic studies of complexes such as (EtNC)AuCN and [Au(CN)2]1 have shown that metalto- ligand charge transfer transitions appear at shorter wavelengths, generally below 250 nm.24–26 Coordination of the ligand by gold produces a marked perturbation of the ligand spectrum.Each of the complexes is luminescent at room temperature, both in solution and in the solid state. Fig. 2 shows represent- Fig. 1 The electronic absorption spectra of dichloromethane solutions of (o-xylylNC)AuX and o-xylyl isocyanide.Fig. 2 The emission and excitation spectra for a dichloromethane solution of (o-xylylNC)AuCl and the emission spectrum of solid (o-xylylNC)AuCl. ative data for (o-xylylNC)AuCl. In solution a broad emission is seen with a maximum at 430 nm. The excitation profile for this emission parallels the absorption spectrum. For the solid, the emission spectrum also shows a strong emission at 430 nm along with new, weaker features at 520 and 540 nm. It is likely that the emission features arise from phenyl-localized pp* states.The free ligand itself is luminescent in dichloromethane solution where it shows a structureless emission with a maximum at 300 nm. Similar luminescence phenomena have been characterized in detail for gold complexes of phosphines with phenyl substituents.27 The luminescence behavior of the other complexes is similar, as might be expected for processes that are localized on the o-xylyl isocyanide ligand. No unusual solvent eVects on the luminescence behavior of these complexes in solution or in the solid state have been observed.Crystallographic studies Molecular structures. The molecular structures of all four complexes, (o-xylylNC)AuX where X is I, Br, Cl, or CN, are quite similar. The molecular structure of (o-xylylNC)AuI, which is representative of the group, is shown in Fig. 3. Structural parameters for the group are set out in Table 2 where bond lengths and distances can be compared. All complexes possess two-coordinate, nearly linear structures about gold and nearly linear Au–C–N portions.Thus, the C–Au–X angles fall in the narrow range from 175.5 to 1808 and the Au–C–N angles fall in the range from 175.0(8) to 1808. Bond distances within each complex fall within normal ranges. Despite the similarities in molecular structures, there are considerable variations in the intermolecular organization in the solid state. In particular, no two complexes in this group of four form isomorphic crystals.In view of the solvate dependent properties of 2, it is significant to note that none of the complexes reported here crystallizes with solvent molecules incorporated into the solid. Solid state molecular organization. Data regarding the intermolecular organization of the four new solids are given in Fig. 3 The molecular structure of (o-xylylNC)AuI with 50% thermal contours.J. Chem. Soc., Dalton Trans., 1998, 3715–3720 3717 Table 2 Selected bond distances (Å) and angles (8) within molecules Au(1)–C Au(2)–C Au(3)–C Au(1)–X Au(2)–X Au(3)–X C–Au(1)–X C–Au(2)–X C–Au(3)–X Au(1)–C–N Au(2)–C–N Au(3)–C–N (o-xylylNC)AuI 1.947(9) 2.5288(6) 179.9(2) 178.5(7) (o-xylylNC)AuBr 1.930(13) 1.919(14) 1.936(13) 2.395(2) 2.3480(5) 2.369(2) 175.7(4) 178.8(4) 175.5(5) 176.6(12) 178.1(13) 176.9(14) (o-xylylNC)AuCl 1.933(13) 1.928(13) 2.258(3) 2.256(3) 178.3(4) 176.5(4) 179.1(11) 177.2(10) (o-xylylNC)AuCN 2.001(10) 1.945(10) 1.940(13) 1.984(12) 2.012(8) 2.009(18) 179.0(4) 178.4(5) 180 177.2(10) 175.0(8) 180 Table 3 while Figs. 4–9 show relevant drawings of the solid state structures. 1. (o-xylylNC)AuCl. There are two complete molecules of the molecular complex in the asymmetric unit and these form a dimer through a single close Au ? ? ?Au contact of 3.3570(11) Å. A view of the dimer is shown in Fig. 4. These dimers are organized into loose chains as shown in Fig. 5. Within these chains of dimers, the additional contacts between gold centers exceed the distance where specific attractive interactions are present.The Au(2) ? ? ?Au(29) separation is 3.6095(12) Å, while the Au(1) ? ? ?Au(10) separation is even longer, 4.0225(12) Å. 2. (o-xylylNC)AuI. Although there is only one molecule in Fig. 4 A view of the dimer of (o-xylylNC)AuCl with 50% thermal contours. Fig. 5 A view of the organization of dimers of (o-xylylNC)AuCl into loose chains. the asymmetric unit, the individual molecules are organized into chains through aurophilic interactions.A view of the chain is shown in Fig. 6. The Au ? ? ? Au9 distance within the chain is 3.4602(3) Å. The Au9 ? ? ? Au ? ? ? Au0 angle along the chain is 164.73(2)8, so the chain is slightly kinked. 3. (o-xylylNC)AuBr. There are three independent molecules within the asymmetric unit. The molecules involving Au(1) and Au(2) form slightly kinked chains through aurophilic interactions. These chains are shown in Fig. 7. They resemble the chains seen for (o-xylylNC)AuI, and the Au(1) ? ? ?Au(2) distance within the chain is also similar, 3.3480(5) Å.The chains Fig. 6 A view of the molecular organization of chains within (o-xylylNC)AuI. Fig. 7 A view of the molecular organization in (o-xylylNC)AuBr.3718 J. Chem. Soc., Dalton Trans., 1998, 3715–3720 are slightly kinked with the Au(1) ? ? ?Au(2) ? ? ?Au(19) and Au(2) ? ? ?Au(1) ? ? ?Au(20) angles both being 170.29(2)8. The third molecule of (o-xylylNC)AuBr is set oV to the side of Au(1) along the chain as seen in Fig. 7. The Au(3) ? ? ?Au(1) distance is 3.7071(10) Å which is considerably longer than the Au(1) ? ? ?Au(2) distance. Thus it is concluded that there is no aurophilic attraction between the chain and the isolated molecule that contains Au(3). 4. (o-xylylNC)AuCN. This structure also contains three independent molecules in the asymmetric unit, but unlike the case of the bromo complex, all three molecules are involved in aurophilic interactions.These interactions produce a complex grid that is shown in Fig. 8. Fig. 9 shows how the individual molecules interact within a portion of the grid. This grid lies in the ac plane and consists of chains comprised of alternating molecules containing Au(1) and Au(2). Along these chains there are two diVerent Au ? ? ?Au distances. The Au(1) ? ? ?Au(2) Table 3 Intramolecular interactions (bond lengths in Å, angles in 8) in gold complexes (o-xylylNC)AuCl Aurophilic interactions Au(1) ? ? ?Au(2) distance 3.3570(11) Cl(1)–Au(1) ? ? ?Au(2)–Cl(2) dihedral angle 124.42(12) Cl(1)–Au(1) ? ? ?Au(2)–C(10) dihedral angle 125.2(5) Neighboring interactions Au(2) ? ? ?Au(29) separation 3.6095(12) Cl(2)–Au(2) ? ? ?Au(29)–Cl(2) dihedral angle 180 C(10)–Au(2) ? ? ?Au(29)–C(10) dihedral angle 180 Au(1) ? ? ?Au(2) ? ? ?Au(29) angle 97.67(3) Au(2) ? ? ?Au(1) ? ? ?Au(10) angle 123.45(2) Au(1) ? ? ?Au(10) separation 4.0225(12) Cl(1)–Au(1) ? ? ?Au(10)–Cl(10) dihedral angle 180 C(1)–Au(1) ? ? ?Au(10)–C(10) dihedral angle 180 symmetry code: 9 = 2x, 2y, 2z; 0 = 2x, 2y, 1 2 z (o-xylylNC)AuI Aurophilic interactions Au ? ? ? Au9 distance 3.4602(3) Au9 ? ? ? Au ? ? ? Au0 angle 164.73(2) I–Au ? ? ? Au9–I9 dihedral angle 114.81(4) C(1)–Au ? ? ? Au9–C(19) dihedral angle 114.5(5) symmetry code: 9 = x 2 0.5, y, 1.5 2 z (o-xylylNC)AuBr Aurophilic interactions Au(1) ? ? ?Au(2) distance 3.3480(5) Au(1) ? ? ?Au(2) ? ? ?Au(19) angle 170.29(2) Au(2) ? ? ?Au(1) ? ? ?Au(20) angle 170.29(2) Br(1)–Au(1) ? ? ?Au(2)–Br(2) dihedral angle 123.42(6) C(1)–Au(1) ? ? ?Au(2)–C(10) dihedral angle 129.00(6) Neighboring interactions Au(1) ? ? ?Au(3) distance 3.7071(10) Br(1)–Au(1) ? ? ?Au(3)–Br(3) dihedral angle 180 C(1)–Au(1) ? ? ?Au(3)–C(19) dihedral angle 180 symmetry code: 9 = x, 1 1 y, z; 0 = x, y 2 1, z (o-xylylNC)AuCN Aurophilic interactions Au(1) ? ? ?Au(2) distance 3.4220(6) Au(1) ? ? ?Au(20) distance 3.4615(6) Au(1) ? ? ?Au(2) ? ? ?Au(1*) angle 166.59(1) Au(2) ? ? ?Au(1) ? ? ?Au(20) angle 169.66(2) C(1)–Au(1) ? ? ?Au(2)–C(11) dihedral angle 160.6(4) C(0)–Au(1) ? ? ?Au(2)–C(20) dihedral angle 158.9(4) Au(2) ? ? ?Au(3) distance 3.1706(4) Au(3) ? ? ?Au(2) ? ? ?Au(1) angle 92.38(2) Au(3) ? ? ?Au(2) ? ? ?Au(19) angle 99.07(2) Au(2) ? ? ?Au(3) ? ? ?Au(29) angle 164.97(3) C(11)–Au(2) ? ? ?Au(3)–C(21) dihedral angle 90.1(4) C(20)–Au(2) ? ? ?Au(3)–C(27) dihedral angle 88.6(4) symmetry code: 9 = 2x, 1 2 y, z; 0 = 0.5 2 x, y, z 2 0.5, * = 0.5 2 x, y, 0.5 1 z distance is 3.4220(6) Å while the Au(1) ? ? ?Au(20) distance is 3.4615(6) Å.These chains are slightly kinked with Au(1) ? ? ? Au(2) ? ? ?Au(1*) and Au(2) ? ? ?Au(1) ? ? ?Au(20) angles of 166.59(1) and 169.66(2)8, respectively. The chains of alternating molecules that involve Au(1) and Au(2) are connected by links through molecules that contain Au(3). Thus each Au(3) center interacts with two Au(2) centers. The Au(3) ? ? ?Au(2) distance is 3.1706(4) Å and the Au(2) ? ? ?Au(3) ? ? ?Au(29) angle is 164.97(3)8. Thus within this solid, the gold centers, Au(1) and Au(2) are involved with aurophilic interactions with two other gold neighbors, while Au(3) is involved with aurophilic interactions with three neighboring gold centers.Discussion The results described here demonstrate that the solid state structures of the four gold(I) complexes display a marked variation in their intramolecular organization. The structures change with each anion, yet no remarkable feature in anionic environment is apparent within the structures, and there does not appear to be any evidence for secondary coordination of the anions to more than one gold center.The anions appear to be exerting an electronic eVect on the gold centers to which they are bonded and thereby alter the ability of the gold centers to participate in aurophilic interactions. The general disparity among the four structures makes it diYcult to compare the Fig. 8 A view of the grid of Au ? ? ?Au interactions in (o-xylylNC)- Au(CN). Only the positions of the gold atoms are shown. This grid lies in the crystallographic ac plane. Fig. 9 A view of the structure of (o-xylylNC)Au(CN) which shows how the individual molecules interact.J. Chem. Soc., Dalton Trans., 1998, 3715–3720 3719 Table 4 Crystal data and data collection parameters Empirical formula M Color, habit Crystal system Space group a/Å b/Å c/Å b/8 U/Å3 ZT /K r/g cm23 m/mm21 R1 a (obsd data) wR2 b (o-xylylNC)AuI C9H9AuIN 455.04 Pale yellow, needles Orthorhombic Cmca 6.8591(6) 20.3967(17) 15.5101(13) 2169.9(3) 8 169(2) 2.786 16.354 0.034 0.069 (o-xylylNC)AuBr C9H9AuBrN 408.05 Colorless, needles Orthorhombic Pnma 15.521(4) 6.6720(13) 29.135(6) 3017.1(11) 12 140(2) 2.695 18.546 0.042 0.096 (o-xylylNC)AuCl C9H9AuClN 363.59 Colorless, prism Monoclinic P21/n 10.614(3) 17.216(4) 11.011(3) 97.93(2) 1992.8(9) 8 130(2) 2.424 14.977 0.070 0.051 (o-xylylNC)AuCN C10H9AuN2 354.16 Colorless, block Orthorhombic Aba2 13.9609(2) 26.62590(10) 13.63710(10) 5069.20(8) 20 156(2) 2.320 14.464 0.040 0.134 a R1 = S||Fo 2 Fc||/S|Fo|.b wR2 = [S[w(Fo 2 2 Fc 2)2]/S[w(Fo 2)2]]� �� . eVects of the variation in the nature of the anions. Thus for example the Au ? ? ?Au distances in (o-xylylNC)AuX decrease in the order I > Br > Cl, which diVers from what is seen for the (Me2PhP)AuX series of dimers 14 or that predicted theoretically 7 for such dimers.However, only (o-xylylNC)AuCl forms a simple dimer through Au ? ? ?Au interactions, while (o-xylyl- NC)AuBr and (o-xylylNC)AuI form extended chains in which each gold atom participates in two rather than just one aurophilic interaction. Further work is needed to elucidate the structural eVects of multiple aurophilic interactions. The aurophilic interactions seen in the four complexes reported here are shorter and more extended than seen previously for most other complexes of the type (RNC)AuX.The compounds, (MeNC)AuCl, (t-BuNC)AuCl, (t-BuNC)AuBr, and (PhNC)AuBr, crystallize with the molecules arranged into zigzag chains with anti-parallel orientations of individual molecules.21,28 This anti-parallel orientation is that expected by simple consideration of dipolar eVects. (In contrast, molecules that display strong aurophilic attraction have the individual molecules arranged in a staggered fashion with X–Au ? ? ?Au–X dihedral angles that are close to 908.5,9,10) The distance between gold centers in these chains falls in the range 3.6–3.7 Å, and attractive aurophilic interactions within these chains are expected to be weak.For (PhNC)AuCl a similar structure is formed, but the Au ? ? ?Au distance is shorter, 3.463(1) Å, and significant aurophilic attractions may be present.21 (Mesityl- NC)AuCl forms a discrete dimer through an aurophilic attraction (Au ? ? ?Au distance, 3.336(1) Å) that closely resembles that seen here for (o-xylylNC)AuCl.21 The complex (t-BuNC)- Au(NO3) also forms a kinked chain with Au ? ? ?Au distances of 3.2955(8) and 3.3243(8) Å,22 and (t-BuNC)Au(CN) forms a chain with an Au ? ? ?Au distance of 3.695 Å.29 (MeOC( O)CH2NC)AuX where X is Cl or Br forms a corrugated sheet structure that is somewhat related to that reported here for (o-xylylNC)Au(CN) but with longer distances between the gold centers.21 While the four new complexes reported here are luminescent in solution and in the solid state, it is likely that the emission comes from xylyl based, pp* states.The structural variation seen in the four complexes is not evident in the luminescence behavior. Experimental The precursor, (Ph3As)AuCl, was prepared as described previously, 30 and the analogous bromo and iodo complexes were obtained by metathesis with sodium bromide or sodium iodide via the procedure described earlier for the preparation of (Ph3As)Au(SCN).30 Syntheses (o-xylylNC)AuCl. A 256 mg (1.95 mmol) portion of o-xylyl isocyanide was added to a solution of 1 g (1.86 mmol) of (Ph3As)AuCl in 20 mL of chloroform.The solution was stirred for 30 min. Diethyl ether (20 mL) was added, and the resulting solution was partially evaporated under reduced pressure until the white product crystallized. The product was collected by filtration, washed with diethyl ether, and dried under vacuum; yield 409 mg, 60%. (o-xylylNC)AuBr.This was obtained as colorless crystals in 65% yield by the procedure described above but utilizing (Ph3As)AuBr as starting material. (o-xylylNC)AuI. This was obtained in 56% yield as pale yellow crystals by the procedure described above with (Ph3As)- AuI as starting material. (o-xylylNC)AuCN. A 67 mg (0.51 mmol) portion of o-xylyl isocyanide was added to a stirred suspension of 109 mg (0.49 mmol) of gold(I) cyanide in 20 mL of chloroform. The solution was stirred for 1 h during which the solid dissolved.The solution was filtered and a 50 mL portion of diethyl ether was added to the filtrate. The solution was partially evaporated under reduced pressure to produce the product as white crystals. These were collected by filtration, washed with diethyl ether, and dried under vacuum; yield, 141 mg, 82%. Crystallography X-Ray data collection. Crystals of all four complexes were obtained by direct diVusion of diethyl ether into a saturated solution of the complex in dichloromethane.All crystals were coated with a light hydrocarbon oil and mounted on a glass fiber in the cold dinitrogen stream of the diVractometer. Data for (o-xylylNC)AuBr and (o-xylylNC)AuCl were collected on a Siemens R3m/V diVractometer with graphite monochromated Mo-Ka (l = 0.71073 Å) radiation, while data for (o-xylylNC)- AuI and (o-xylylNC)AuCN were collected on a Siemens SMART CCD with graphite-monochromated Mo-Ka radiation. Lorentz and polarization corrections were applied.Check reflections were stable throughout data collection except for (o-xylylNC)AuCl which showed a 9.2% increase in intensity due to detector noise. This factor was corrected. Crystal data are given in Table 4. Solution and structure refinement. Calculations for the structures were performed using SHELXS-97 and SHELXL-97. Tables of neutral atom scattering factors, f 9 and f 0, and absorp-3720 J. Chem. Soc., Dalton Trans., 1998, 3715–3720 tion coeYcients are from a standard source.31 The structures were all solved via direct methods.All atoms except hydrogen atoms were refined anisotropically. Hydrogen atoms were included through the use of a riding model. Three hydrogen atoms were aYxed on each of the methyl carbon atoms to provide tetrahedral geometry about these carbon atoms. The positions of the hydrogen atoms were not refined since the structure is dominated by scattering from gold and other heavy atoms.For (o-xylylNC)AuBr and (o-xylylNC)AuCl an empirical absorption correction was used,32 while for (o-xylylNC)AuI and (o-xylylNC)AuCN a semi-empirical method utilizing equivalents was employed.33 CCDC reference number 186/1170. See http://www.rsc.org/suppdata/dt/1998/3715/ for crystallographic files in .cif format. Acknowledgements We thank the US National Science Foundation (Grant CHE 9610507) for support and Johnsohey for a loan of chloroauric acid. References 1 J.C. Vickery, M. M. Olmstead, E. Y. Fung and A. L. Balch, Angew. Chem., Int. Ed. Engl., 1997, 36, 1179; E. Y. Fung, M. M. Olmstead, J. C. Vickery and A. L. Balch, Coord. Chem. Rev., 1998, 171, 151. 2 M. A. Mansour, W. B. Connick, R. J. Lachicotte, H. J. Gysling and R. Eisenberg, J. Am. Chem. Soc., 1998, 120, 1329. 3 P. G. Jones, Gold Bull., 1981, 14, 102. 4 H. Schmidbaur, Interdiscip. Sci. Rev., 1992, 17, 213. 5 S. S. Pathaneni and G. R. Desiraju, J. Chem. Soc., Dalton Trans., 1993, 319. 6 H. Schmidbaur, Chem. Soc. Rev., 1995, 391. 7 P. Pyykkö, J. Li and N. Runeberg, Chem. Phys. Lett., 1994, 218, 133. 8 P. Pyykkö, Chem. Rev., 1997, 97, 597. 9 P. Pyykkö, N. Runeberg and F. Mendizabal, Chem. Eur. J., 1997, 3, 1451. 10 P. Pyykkö and F. Mendizabal, Chem. Eur. J., 1997, 3, 1458. 11 H. Schmidbaur, W. Graf and G. Müller, Angew. Chem., Int. Ed. Engl., 1988, 27, 417. 12 D. E. Harwell, M. D. Mortimer, C. B. Knobler, F. A. L. Anet and M. F. Hawthorne, J. Am. Chem.Soc., 1996, 118, 2679. 13 A. L. Balch, E. Y. Fung and M. M. Olmstead, J. Am. Chem. Soc., 1990, 112, 5181. 14 D. V. Toronto, B. Weissbart, D. S. Tinti and A. L. Balch, Inorg. Chem., 1996, 35, 2484; B.Weissbart, D. V. Toronto, A. L. Balch and D. S. Tinti, Inorg. Chem., 1996, 35, 2490. 15 Z. Assefa, B. G. McBurnett, R. J. Staples, J. P. Fackler, Jr., B. Assmann, K. Angermaier and H. Schmidbaur, Inorg. Chem., 1995, 34, 75. 16 H. Schmidbaur, G. Weidenhiller, O. Steigelman and G. Müller, Z. Naturforsch., Teil B, 1990, 45, 747. 17 K. Angermaier, A. Sladek and H. Schmidbaur, Z. Naturforsch., Teil B, 1996, 51, 1671. 18 P. M. Van Calcar, M. M. Olmstead and A. L. Balch, Inorg. Chem., 1997, 36, 5231; P. M. Van Calcar, M. M. Olmstead and A. L. Balch, J. Chem. Soc., Chem. Commun., 1995, 1773. 19 For a review on other gold-based polymers see: R. J. Puddephatt, Chem. Commun., 1998, 1055. 20 J. E. Parks and A. L. Balch, J. Organomet. Chem., 1974, 71, 453. 21 W. Schneider, K. Angermaier, A. Sladek and H. Schmidbaur, Z. Naturforsch., Teil B, 1996, 51, 790. 22 T. J. Mathieson, A. G. Langdon, N. B. Milestone and B. K. Nicholson, Chem. Commun., 1998, 371. 23 W. Schneider, A. Sladek, A. Bauer, K. Angermaier and H. Schmidbaur, Z. Naturforsch., Teil B, 1997, 52, 53. 24 S. K. Chastain and W. R. Mason, Inorg. Chem., 1982, 21, 3717. 25 W. R. Mason, J. Am. Chem. Soc., 1976, 98, 5182. 26 N. Nagasundaram, G. Roper, J. Biscoe, J. W. Chai, H. H. Patterson, N. Blom and A. Ludi, Inorg. Chem., 1986, 25, 2947. 27 L. J. Larson, E. M. McCauley, B. Weissbart and D. S. Tinti, J. Phys. Chem., 1995, 99, 7218. 28 D. S. Eggleton, D. F. Chodosh, R. L. Webb and L. L. Davis, Acta Crystallogr., Sect. C, 1986, 42, 36. 29 C. M. Che, H. K. Yip, W. T. Wong and T. F. Lai, Inorg. Chim. Acta, 1992, 197, 177. 30 N. J. DeStafuno and J. L. Burmeister, Inorg. Chem., 1971, 10, 998. 31 International Tables for Crystallography,, ed. A. J. C. Wilson, Kluwer Academic Publishers, Dordrecht, 1992, vol. C. 32 S. Parkin, B. Moezzi and H. Hope, J. Appl. Crystallogr., 1995, 28, 53. 33 R. H. Blessing, Acta Crystallogr., Sect. A, 1995, 51, 33. Paper 8/05086D

ISSN:1477-9226    

DOI:10.1039/a805086d

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, 3721–3726 3721 Nucleophilic behaviour of the neutral complexes [M(CŸP)- (S2CNMe2)] [M 5 Pd, Pt; CŸP 5 CH2C6H4P(C6H4Me-o)2-Í-C,P] towards Ag(I) and Au(I) compounds. Synthesis (M 5 Pd, Pt) and molecular structures (M 5 Pt) of polynuclear complexes containing M–Ag and M–S bonds J. Forniés,a A. Martín,b R. Navarro,a V. Sicilia,a P. Villarroya a and A. G. Orpen b a Departamento de Química Inorgánica, Instituto de Ciencia de Materiales de Aragón, Universidad de Zaragoza-C.S.I.C., 50009 Zaragoza, Spain b School of Chemistry, University of Bristol, Bristol, UK BS8 ITS Received 2nd July 1998, Accepted 16th September 1998 The reactions between [M{CH2C6H4P(C6H4Me-o)2}(S2CNMe2)] (M = Pt A, Pd B) and [M9(OClO3)(PPh3)] (M9 = Ag, Au) in 1 : 1 ratio yielded [M{CH2C6H4P(C6H4Me-o)2}(S2CNMe2)M9(PPh3)]ClO4 (M9 = Ag, M = Pt 1, Pd 2; M9 = Au, M = Pt 3, Pd 4).The molecular structure of 1 indicates that the Ag and Pt atoms are bridged by one S atom of the S2CNMe2 ligand and show a weak interaction between them [Pt–Ag 2.875 (1) Å].Complexes A and B also react with AgClO4 in 1 : 1 molar ratio to give [M2{CH2C6H4P(C6H4Me-o)2}2(S2CNMe2)2Ag{Ag(OClO3)}]ClO4 (M = Pt 5, Pd 6). The X-ray study of 5 revealed that this compound crystallized as a mixture of [Pt2{CH2C6H4P(C6H4Me-o)2}2- (S2CNMe2)2Ag{Ag(OClO3)}]ClO4 and [Pt2{CH2C6H4P(C6H4Me-o)2}2(S2CNMe2 )2{Ag(OH2)}{Ag(OClO3)}]ClO4 in 1 : 1 molar ratio. In the two diVerent cations only one Ag atom is bonded to Pt, with the Pt–Ag lengths being 2.671 (3) Å for [ Pt2{CH2C6H4P(C6H4Me-o)2}2(S2CNMe2)2Ag{Ag(OClO3)}]1 and 2.752(3) Å for [Pt2{CH2C6H4P- (C6H4Me-o)2}2(S2CNMe2)2{Ag(OH2)}{Ag(OClO3)}]1, both in the range found in other compounds with Pt–Ag bonds.Compounds 5 and 6 react with PPh3 in 1 : 2 molar ratio to give compounds 1 and 2 respectively. Introduction Anionic organometallic complexes of Pt(II) with perhalophenyl ligands are known to react with a variety of Ag1 derivatives to aVord heteronuclear compounds displaying donor–acceptor PtII æÆ AgI bonds,1 in many cases unsupported by any covalent bridging ligand.In contrast, neutral perhalophenyl derivatives do not yield similar Pt–Ag complexes. As far as we know, only a small number of Pt–Ag complexes involving neutral Pt(II) fragments have been described,2–8 and structurally characterized.4–8 In the latter complexes there are ligands bridging between the Pt and Ag atoms.Recently we have described the synthesis of the neutral complexes [M{CH2C6H4P(C6H4Me-o)2}(S2CZ)] (M = Pt, Pd; Z = NMe2, OEt) 9 and we have demonstrated their ability to form donor–acceptor M–Hg bonds, unsupported by any covalent bridging ligands, when they are reacted with HgX2 (X = Br, I).9b This indicates that in these complexes the metal centre, M, must have an excess of available electron density to act as a Lewis base toward suitable Lewis acids. For this reason we have decided to explore the reactivity of the compounds [M{CH2C6H4P(C6H4Me-o)2}(S2CZ)] (M = Pt, Pd; Z = NMe2, OEt) towards other Lewis acids such as [M9(OClO3)(PPh3)] (M9 = Ag, Au) and AgClO4 in order to prepare heteropolynuclear complexes, to study their structures and to establish the influence of the sulfur containing ligands in the formation of the Pt–M9 bonds. While [M{CH2C6H4P(C6H4- Me-o)2}(S2COEt)] (M = Pt, Pd) react with AgClO4 and [M9(OClO3)(PPh3)] (M9 = Ag, Au) with decomposition, [M- {CH2C6H4P(C6H4Me-o)2}(S2CNMe2)] (M = Pt A, Pd B) aVord new complexes which are the subject of this paper. Results and discussion Reactivity of complexes [M{CH2C6H4P(C6H4Me-o)2}- (S2CNMe2)] (M 5 Pt A, Pd B) with [Ag(OClO3)(PPh3)], [Au(OClO3)(PPh3)] and AgClO4 The reactions carried out are collected in Scheme 1.As is to be expected, the reactions of [M{CH2C6H4P(C6H4- Me-o)2}(S2CNMe2)] (M = Pt A, Pd B) with [Ag(OClO3)(PPh3)] in 1 : 1 molar ratio in the dark gave [M{CH2C6H4P(C6H4- Me-o)2}(S2CNMe2)Ag(PPh3)]ClO4 (M = Pt 1, Pd 2), which could be isolated as stable solids in good yield [Scheme 1(a)].Scheme 1 [M(C^P)(S2CNMe2)] M= Pt A, Pd B AgClO4 M= Pt 5, Pd 6 (c) [M2(C^P)2(S2CNMe2)2Ag{Ag(OClO3)}]ClO4 [M(C^P)(S2CNMe2)AgPPh3] ClO4 [Ag(OClO3)PPh3] M= Pt 1, Pd 2 (a) [M(C^P)(S2CNMe2)AuPPh3] ClO4 M= Pt 3, Pd 4 (d) PPh3 (b) [Au(OClO3)PPh3]3722 J. Chem. Soc., Dalton Trans., 1998, 3721–3726 Table 1 Crystal data and structure refinement for 1?1.5CHCl3 and 5?0.5H2O?0.5CHCl3?0.125C6H14 a Empirical formula Ma /Å b/Å c/Å a/8 b/8 g/8 U/Å3 Dc/Mg m23 m/mm21 F(000) Crystal size/mm q range for data collection/8 Index ranges Reflections collected Independent reflections (Rint) Data, restraints, parameters Goodness-of-fit b on F2 Final R indices b [I > 2s(I)]: R1, wR2 R indices (all data):bR1, wR2 Largest diVerence peak, hole/e Å23 g(w) b 1?1.5CHCl3 C42H41AgClNO4P2PtS2?1.5CHCl3 1267.28 13.312(4) 14.145(5) 14.793(5) 112.19(3) 99.97(3) 101.18(3) 2435.3(14) 1.728 3.765 1246 0.50 × 0.30 × 0.30 1.54–25.00 0 < h < 15, 216 < k < 16, 217 < l < 17 9042 8584 (0.0220) 8583, 6, 632 1.239 0.0451, 0.1263 0.0568, 0.1340 2.702, 21.972 0.0800 5?0.5CHCl3?0.125C6H14 C48H52Ag2Cl2N2O8P2Pt2S4?0.5H2O?0.5CHCl3?0.125C6H14 1731.38 13.1745(25) 14.3883(25) 17.6371(27) 84.071(12) 85.845(12) 83.872(12) 3300.0(10) 1.742 5.173 1672 0.55 × 0.45 × 0.35 1.56–23.27 214 < h < 10, 215 < k < 15, 219 < l < 19 14032 9203 (0.0291) 9200, 36, 707 1.837 0.0512, 0.1517 0.0626, 0.1635 1.354, 20.901 0.0600 a Details in common: triclinic, space group P1� , T = 293(2) K, Z = 2, l = 0.71073 Å; full matrix least-squares refinement on F 2.b R1 = S Fo| 2 |Fc /S|Fo|; wR2 = {S[w(Fo 2 2 Fc 2)2/S[w(Fo 2)2]}� �� ; w = [sc 2(Fo 2) 1 (gP)2]21, where P = [Max(Fo 2, 0) 1 2Fc 2]/3; goodness of fit = [w(Fo 2 2 Fc 2)2/(N 2 P)]� �� , where N, P are the numbers of observations and parameters, respectively.The gold(I) derivatives [M{CH2C6H4P(C6H4Me-o)2}- (S2CNMe2)Au(PPh3)]ClO4 (M = Pt 3, Pd 4) were obtained by reaction of complexes [M{CH2C6H4P(C6H4Me-o)2}(S2CNMe2)] (M = Pt A, Pd B) with [Au(OClO3)(PPh3)] in 1 : 1 molar ratio [Scheme 1(b)]. The [Au(OClO3)(PPh3)] species was generated in situ from [AuCl(PPh3)] and AgClO4. The structure of [Pt{CH2C6H4P(C6H4Me-o)2}(S2CNMe2)- Ag(PPh3)]ClO4 1 was established by a single crystal X-ray study. The structure of the cation is shown in Fig. 1. General crystallographic information is collected in Table 1. Selected bond distances and angles are given in Table 2. As can be seen, the Pt atom displays a distorted squarepyramidal environment with the Pt, the C and P atoms of the CŸP group and both S atoms of the S2CNMe2 located in the basal plane and the Ag atom of the [Ag(PPh3)]1 fragment in the apical position. The angle between the Pt–Ag vector and the perpendicular to the basal plane [Pt, P(1), C(1), S(1), S(2)] is 29.58.10 Distances and angles around the Pt center in the basal plane are similar to those observed in the starting complex [Pt- {CH2C6H4P(C6H4Me-o)2}(S2CNMe2)] 9a or in [Pt{CH2C6H4P- (C6H4Me-o)2}(S2CNMe2)HgI(m-I)]2.9b As in these cases, the angles between cis ligands around the platinum center are rather diVerent from 908 due to the small bite angles of both chelate ligands present in the complex. The metallocycle defined by the Pt, P(1), C(1), C(2), C(3) atoms is planar and coplanar with the C-bonded o-tolyl ring.10 The other two o-tolyl rings are also planar, and they are oriented forming a dihedral Table 2 Selected bond lengths (Å) and angles (8) for [Pt(CŸP)(S2CNMe2) Ag(PPh3)]ClO4 1 Pt–C(1) Pt–P(1) Pt–S(1) Pt–S(2) C(1)–Pt–P(1) P(1)–Pt–S(2) Pt–S(1)–Ag P(2)–Ag–Pt 2.062(7) 2.240(2) 2.369(2) 2.405(2) 85.0(2) 107.7(1) 70.6(1) 131.5(1) Pt–Ag Ag–P(2) Ag–S(1) C(1)–Pt–S(1) S(1)–Pt–S(2) S(1)–Ag–P(2) S(1)–Ag–Pt 2.875(1) 2.383(2) 2.594(2) 93.4(2) 74.1(1) 165.0(1) 51.0(1) angle of dash;C(14)] and 89.798 [C(15)–C(21)] respectively with the metallocycle plane [Pt, P(1), C(1), C(2), C(3)]. The platinum and silver fragments, [Pt{CH2C6H4P(C6H4- Me-o)2}(S2CNMe2)] and [Ag(PPh3)], share one sulfur atom of the dithiocarbamate group, leading to a very acute Pt–S(1)–Ag angle [70.6 (1)8] probably as a consequence of the interaction between the metal centers.The Ag atom is also coordinated by the PPh3 ligand and more weakly by the Pt atom [Pt–Ag 2.875(1) Å].The coordination environment and the angles around the Ag atom in 1 are similar to those in [(PPh3)- (C6Cl5)ClPt(m-Cl)Ag(PPh3)] 11 and NBu4[PtAgCl2(C6Cl5)2- (PPh3)] 12 in which the Pt and Ag centers are bridged by a Cl atom. The Ag–P11–13 and Ag–S5,8 bond distances, 2.383(2) and 2.594(2) Å respectively, are in the range found for other Pt–Ag complexes containing these kind of ligands. The Pt–Ag distance [2.875(1) Å] is shorter than that corresponding to the sum of the van der Waals radii 14 for Pt and Ag and is in the range found in other complexes which exhibit Fig. 1 Molecular structure and atomic numbering scheme of the cation in 1.J. Chem. Soc., Dalton Trans., 1998, 3721–3726 3723 Table 3 31P{1H} NMR data for complexes 1–6 a CŸP PPh3 Complex [Pt(CŸP)(S2CNMe2)] A [Pd(CŸP)(S2CNMe2)] B [Pt(CŸP)(S2CNMe2)Ag(PPh3)]ClO4 1 b [Pd(CŸP)(S2CNMe2)Ag(PPh3)]ClO4 2 c [Pt(CŸP)(S2CNMe2)Au(PPh3)]ClO4 3 [Pd(CŸP)(S2CNMe2)Au(PPh3)]ClO4 4 [Pt2(CŸP)2(S2CNMe2)2Ag{Ag(OClO3)}]ClO4 5 [Pd2(CŸP)2(S2CNMe2)2Ag{Ag(OClO3)}]ClO4 6 c d(31P) 24.70 (s) 35.58 (s) 25.20 (s) 37.07 (s) 24.52 (s) 35.54 (s) 24.93 (s) 41.07 (s) JPtP/Hz 3969.4 4011.4 4156.8 3911.8 d(31P) 9.1 (d) 13.46 (2d) 32.83 (s) 33.49 (s) JAgP/Hz 109Ag–P 714.36 107Ag–P 618.78 a CŸP = CH2C6H4P(C6H4Me-o)2; spectra recorded in CDCl3 at room temperature unless otherwise stated; s = singlet.b T = 193 K, CD2Cl2. c T = 218 K, CDCl3. Table 4 1H NMR data for complexes 1–6a CŸP and PPh3 Complex [Pt(CŸP)(S2CNMe2)] A [Pd(CŸP)(S2CNMe2)] B [Pt(CŸP)(S2CNMe2)Ag(PPh3)]ClO4 1 [Pd(CŸP)(S2CNMe2)Ag(PPh3)]ClO4 2 [Pt(CŸP)(S2CNMe2)Au(PPh3)]ClO4 3 [Pd(CŸP)(S2CNMe2)Au(PPh3)]ClO4 4 [Pt2(CŸP)2(S2CNMe2)2Ag{Ag(OClO3)}]ClO4 5 [Pd2(CŸP)2(S2CNMe2)2Ag{Ag(OClO3)}]ClO4 6 b d(CH3) 2.42 (s) 2.78 (s) 2.44 (s) 2.74 (s) 2.30 (s) 2.64 (s) 2.32 (s) 2.63 (s) 2.31 (s) 2.62 (s) 2.39 (s) 2.69 (s) 2.28 (s) 2.63 (s) 2.12 (s) 2.65 (s) d(CH2) (J/Hz) 3.38 (s, 1H, 2JPtH = 85.7) 3.44 (s, 1H, 2JPtH = 94.3) 3.38 (s, 2H) 3.31 (2H, 2JPtH = 89) 3.33 (s, 2H) —c 2.91 (s, 1H) 3.16 (s, 1H) 3.08 (s, 1H) 3.21 (s, 1H) 3.08 (d, 1H, 2JHH = 11.13) 3.37 (d, 1H) d (aromatic) 6.9–7.3 6.7–7.4 6.8–7.5 6.8–7.6 6.8–7.7 6.7–7.7 6.7–7.7 6.5–7.7 d(2S2CNMe2) 3.23 (s) 3.24 (s) 3.29 (s) 3.34 (s) 3.36 (s) 3.39 (s) 3.44 (s) 3.52 (s) 3.45 (s) 3.49 (s) 3.27 (s) 3.31 (s) 3.34 (s) 3.40 (s) 3.49 (s) 3.54 (s) a CŸP = CH2C6H4P(C6H4Me-o)2; spectra recorded in CDCl3 at room temperature unless otherwise stated; s = singlet, d = doublet.b 218 K. c CH signal obscured by Me2NCS2 signal. Pt–Ag bonds. As example can be mentioned the compounds [Pt3(S2CNPri 2)6Ag2]BF4 4 and [Pt3(S2CNBun 2)6Ag2]ClO4 4 in which the Pt–Ag distances range from 3.061 to 2.825 Å and the interaction between both metal centers is indicated by the coupling of the nuclear spins observed in their 195Pt NMR spectra. Unfortunately, our complexes are not soluble enough to measure the 195Pt NMR spectra.These compounds seem to retain their structure in solution, because their mass spectra (FAB1) show in all cases the molecular peak for the corresponding cation [M{CH2C6H4P(C6H4Meo) 2}(S2CNMe2)M9(PPh3)]1 [988 (1), 900 (2), 1077 (3), 988 (4)]. The 31P NMR spectra of 1 and 2 were measured at low temperature but this was not necessary for complexes 3 and 4. According to their structure, compounds 1–4 show two signals due to the CŸP and the PPh3 groups (Table 3).The CŸP give a singlet, which appears flanked by the corresponding 195Pt satellites for complexes 1 and 3 [JPtP = 4011.4 Hz (1), 4156.8 Hz (3)]. The signal due to M9PPh3 appears as a singlet when M9 = Au (complexes 3 and 4) or as two doublets when M9 = Ag (complexes 1 and 2), because of the presence of two isotopes, 107Ag and 109Ag, each having spin I = 1/2. For complex 2 the two Ag–P coupling constants could be calculated as 218 K, with J107AgP and J109AgP = 618.78 and 714.36 Hz respectively.Similar values for JAgP have been observed in other complexes containing the fragment ‘Ag(PPh3)’ in e.g. [PtMe2(bpy){Ag- (PPh3)}]BF4.2 For complex 1, JAgP could not be observed, even when the 31P NMR spectrum was measured at 193 K in CD2Cl2. The 1H NMR spectra of compounds 1–4 also show the signals due to the CŸP and the PPh3 groups in agreement with their structure (Table 4). Complexes 1–4 show similar IR and NMR spectra and, on these bases, similar structures can be proposed.However, since it is well known that the Pd centres exhibit a lower tendency to involve in PdÆM bonds,9b,15 it is possible that in complexes 2 and 4 the Pd and M9 fragments are only joined by the sulfur centers. Complexes [M{CH2C6H4P(C6H4Me-o)2}(S2CNMe2)] (M = Pt A, Pd B) react also with AgClO4 in 1 : 1 molar ratio in the dark to yield the heteronuclear complexes of stoichiometry [M2{CH2C6H4P(C6H4Me-o)2}2(S2CNMe2)2Ag2(ClO4)2] (M = Pt 5, Pd 6) according to Scheme 1(c).Compounds 5 and 6 are airstable and can be stored in the dark for extended periods. The IR spectra of 5 and 6 show in both cases absorptions due to the CŸP and the S2CNMe2 216 ligands together with the corresponding ones to the ClO4 2 anion.17 However, no absorptions assignable to the O3ClO2 ligand can be observed. The X-ray study of 5 [Fig. 2(a), (b)] revealed that, in the solid, only one ClO4 2 group is ionic whereas the other is bonded to one of the silver atoms, and also, that in 50% of the molecules, the second silver atom is bonded to one molecule of water [Fig. 2(b)]. This indicates that the crystallized compound is a mixture of [Pt2{CH2C6H4P(C6H4Me-o)2}2(S2CNMe2)2- Ag{Ag(OClO3}]ClO4 and [Pt2{CH2C6H4(C6H4Me-o)2}2(S2CNMe2) 2{Ag(OH2)}{Ag(OClO3)}]ClO4 in 1: 1 molar ratio. However, it should be noted that the IR spectra of 5 and 6 show that no water is present in the non-crystalline solids. Also, the3724 J. Chem. Soc., Dalton Trans., 1998, 3721–3726 FAB1 spectra show the molecular peaks corresponding to [M2{CH2C6H4P(C6H4Me-o)2}2(S2CNMe2)2Ag{Ag(OClO3)}]1 cations (5, 1553; 6, 1376).These facts lead us to formulate compounds 5 and 6 as [M2{CH2C6H4P(C6H4Me-o)2}2- (S2CNMe2)2Ag{Ag(OClO3)}]ClO4 (M = Pt 5, Pd 6) and to consider that the coordination of water to one Ag atom of one half of the molecules took place during the crystallization process. The molecular structure of the two diVerent images of the cation observed in the crystal of 5 are shown in Fig. 2 together with the atomic numbering schemes.The only diVerence between them is the coordination mode of Ag(2) [Fig. 2(a)] or Ag(29) [Fig. 2(b)]. General crystallographic information is collected in Table 1. Bond distances and angles are summarized in Table 5. First, we will describe the structure of the cationic complex [Pt2(CŸP)2(S2CNMe2)2Ag{Ag(OClO3)}]1 [CŸP = CH2C6H4P- (C6H4Me-o)2] [Fig. 2(a)]. As can be seen, the complex cation can be regarded as two Pt(CŸP)(S2CNMe2) sub-units connected by two silver atoms.The platinum atoms show diVerent coordination environments. Atom Pt(1) is located in a square pyramidal environment with Ag(2) sited in the apical position and the donor atoms of the CŸP and S2CNMe2 chelating ligands in the basal plane. The Pt(1)–Ag(2) distance [2.671(3) Å] is at the low end of the range of distances found for other complexes with Pt–Ag bonds.1 In addition, the angle between the Pt(1)–Ag(2) vector and the perpendicular to the Pt(1) coordination plane [Pt(1), C(1), P(1), S(1), S(2)] is only 7.68.10 Both facts indicate a Pt(1)–Ag(2) bond which is not supported by covalent bridging ligands.On the other hand, atom P(2) shows a distorted square-planar environment formed by the donor atoms of the two chelate ligands bonded to it [C(25), P(2), S(3), S(4)]. Bond distances and angles around the platinum center in both Pt(CŸP)(S2- Fig. 2 Molecular structures and atomic numbering schemes of two views of the cation in 5.CNMe2) sub-units are in the range usually found for related compounds.9,18–21 The dihedral angle between the square planes is 23.28.10 The two silver atoms present in the cation show also diVerent environments. Atom Ag(2) is bonded to Pt(1) [Pt(1)–Ag(2) 2.671(3) Å] and to one S [S(3)] atom of the Pt(2) sub-unit [Ag(2)–S(3) 2.300(5) Å] showing essentially a linear coordination mode [Pt(1)–Ag(2)–S(3) 167.1 (2)8]. The Ag(2) atom is located at 2.998(3) Å from the Pt(2), however the angle formed by the Pt(2)–Ag(2) vector and the perpendicular to the Pt(2) coordination plane is 43.98, indicating that there is no Pt(2)– Ag(2) bond.Atom Ag(1) is bonded to one S atom of each Pt sub-unit, [Ag(1)–S(1) 2.485(3) and Ag(1)–S(4) 2.660(3) Å], with the S(1)–Ag(1)–S(4) angle being 174.6(1)8. Ag(1) is also bonded to one oxygen atom of a perchlorate group [Ag(1)–O(1) 2.564(11) Å] showing a T-shaped coordination geometry.The Ag(1)– O(1) distance is shorter than those observed in other complexes with ClO4 coordinated in monodentate [Ag2(napy)2]- (ClO4)2 [Ag–O 2.62(2) Å], (napy = 1,8-naphthyridine),22 chelate [AgL(ClO4)] {L = 2,11-bis[(diphenylphosphino)methyl]benzo- [c]phenanthrene} [Ag–O 2.75(1) and 2.81(1) Å] 23 or bridge [Ag2(m-dpph)2(m-ClO4)2] (dpph = 1,6-bis(diphenylphosphino)- hexane) [Ag–O 2.639(4) and 2.712(6) Å] 24 fashion, indicating that the Ag(1)–O(1) bond is relatively strong.Atom Ag(1) is located 2.907(1) Å away from the Pt(2) centre and is not close to the perpendicular to the Pt(2) coordination plane [Pt, C(25), P(2), S(3), S(4)], the angle between them being 52.48.10 These features suggest that no bond exists between the metal centers. As we have already mentioned, half of the cations have the stoichiometry [Pt2{CH2C6H4P(C6H4Me-o)2}2(S2CNMe2)2{Ag- (OH2)}{Ag(OClO3)}]1 and their molecular structure is represented in Fig. 2(b). The structural data for this cation are not too diVerent from those for [Pt2{CH2C6H4P(C6H4Me-o)2}2- (S2CNMe2)2Ag{Ag(OClO3)}]1 [Fig. 2(a)] except those concerning the Ag(29) and Ag(2) environments. As is Ag(2), atom Ag(29) is bonded to Pt(1) [Pt(1)–Ag(29) 2.752(3) Å] and to one S atom from the Pt(2) sub-unit [Ag(29)– S(3) 2.694(5) Å], but in contrast to Ag(2), atom Ag(29) is also bonded to the oxygen atom of a water molecule [Ag(29)–O(9) 2.23 (3) Å] showing a distorted triangular planar coordination environment instead of the linear arrangement displayed by Ag(2).The Pt(1)–Ag(29) distance [2.752(3) Å], is longer than Pt(1)– Ag(2) [2.671(3) Å], and this is in keeping with the following: (a) the angle between the perpendicular to the Pt(1) coordination plane and the Pt(1)–Ag(29) vector (22.98) is larger than the one formed with the Pt–Ag(2) vector (7.68), indicating a poorer Table 5 Selected bond lengths (Å) and angles (8) for complex 5 Pt(1)–C(1) Pt(1)–P(1) Pt(1)–S(1) Pt(1)–S(2) Pt(1)–Ag(2) Pt(2)–Ag(2) Ag(2)–S(3) Ag(1)–S(1) Ag(1)–O(1) Ag(1)–S(4) Ag(1)–Ag(2) C(1)–Pt(1)–P(1) C(1)–Pt(1)–S(1) P(1)–Pt(1)–S(2) S(1)–Pt(1)–S(2) C(25)–Pt(2)–P(2) C(25)–Pt(2)–S(3) P(2)–Pt(2)–S(4) S(3)–Pt(2)–S(4) 2.056(11) 2.235(3) 2.355(3) 2.408(3) 2.671(3) 2.998(3) 2.300(5) 2.485(3) 2.564(11) 2.660(3) 2.905(3) 85.1(3) 92.4(3) 108.1(1) 74.5(1) 85.5(4) 93.4(4) 106.7(1) 74.4(1) Pt(2)–C(25) Pt(2)–P(2) Pt(2)–S(3) Pt(2)–S(4) Pt(2)–Ag(1) Pt(1)–Ag(29) Ag(29)–S(3) Ag(29)–O(9) Ag(29)–S(2) Ag(1)–Ag(29) S(1)–Ag(1)–O(1) O(1)–Ag(1)–S(4) S(1)–Ag(1)–S(4) S(3)–Ag(2)–Pt(1) O(9)–Ag(29)–Pt(1) S(3)–Ag(29)–Pt(1) O(9)–Ag(29)–S(3) 2.071(12) 2.228(3) 2.369(3) 2.409(3) 2.907(1) 2.752(3) 2.694(5) 2.231(29) 2.941(5) 2.856(3) 95.6(3) 86.4(3) 174.6(1) 167.1(2) 136.9(7) 130.2(2) 92.9(7)J. Chem.Soc., Dalton Trans., 1998, 3721–3726 3725 overlap between the orbitals involved in the Pt(1)–Ag(29) bond than the corresponding one to the Pt(1)–Ag(2) bond; (b) Ag(29) is three-coordinate and because of this is less acidic than Ag(2), so that the Pt(1)–Ag(29) bond should be weaker.The Ag(29)– O(9) bond length [2.23(3) Å] is shorter than those observed in other silver–aquo complexes such as, e.g. [Ag2(C9H8NO3)2- (H2O)2]?2H2O [Ag–O 2.518(4) Å] 25a and cis-[(NH3)2Pt(1- MeU)(1-MeC)Ag(OH2)](NO3)2?Ag(NO3)?2.5 H2O (1 MeU = 1-methyluracilate, 1-MeC = 1-methylcytosine) [Ag–O 2.396(13) Å].25b Finally, although the Ag(29) atom is located fairly close to the sulfur atoms of the Pt(1) sub-unit [Ag(29)–S(2) 2.941(5) Å] any direct interaction, if present, is very weak. It is noteworthy that in each view of the cation [Fig. 2(a) and (b)] the two Ag atoms are in close proximity [Ag(1)–Ag(2) 2.905(3), Ag(1)–Ag(29) 2.856(3) Å]. These lengths are similar to the Ag–Ag distance in metallic silver (2.8894 Å) 26 and fall in the range of distances observed in complexes with silver–silver interactions.27,28 The 31P NMR spectrum of 5 shows only one singlet with the corresponding 195Pt satellites (see Table 3).Looking at the structure of 5 [Fig. 2(a)] this may be due to the fact that either 5 adopts a symmetrical molecular structure in solution or that dissociative processes take place on the NMR time scale [eqn. (1), M = Pd, Pt]. In the latter case, the observed signal will be [M2{CH2C6H4P(C6H4Me-o)2}2(S2CNMe2)2Ag{Ag(OClO3)}]- ClO4 2 [M{CH2C6H4P(C6H4Me-o)2}(S2CNMe2)] 1 2 AgClO4 (1) the average of the corresponding signals for [Pt{CH2C6H4P- (C6H4Me-o)2}(S2CNMe2)] A and [Pt2{CH2C6H4P(C6H4Meo) 2}2(S2CNMe2)2Ag{Ag(OClO3)}]ClO4 5. 31P NMR spectra of diVerent mixtures of such compounds (5 and A) were shown to give only one singlet at d(31P) values between those corresponding to pure 5 (d 24.93) and A (d 24.7) and as the amount of A in the mixture was increased, the d(31P) values move closer to the d(31P) value for pure A. This observation indicates that the equilibrium represented by eqn.(1) is, in all likelihood, responsible for the observation of only one singlet in the 31P NMR spectrum of 5. In light of this equilibrium, AgClO4 was added to a NMR sample of 5 with a view to obtaining its 31P NMR signal, but a yellow solid precipitated in the NMR tube preventing a successful experiment. The signals observed in the 1H NMR spectrum of 5 are in agreement with the equilibrium represented in eqn. (1) (Table 4). The solution behaviour of compound 6 is similar to that observed for 5 (Tables 3 and 4).As is to be expected, complexes 5 and 6 react with PPh3 (in 1 : 2 molar ratio) in CH2Cl2 yielding the complexes [M- {CH2C6H4P(C6H4Me-o)2-C,P}(S2CNMe2)AgPPh3]ClO4 (M = Pt 1, Pd 2) [Scheme 1(d)]. Conclusion [M{CH2C6H4P(C6H4Me-o)2}(S2CNMe2)] (M = Pt, Pd) act as Lewis bases towards [Ag(OClO3)(PPh3)], [Au(OClO3)(PPh3)] or AgClO4 [M9] and the resulting polynuclear complexes contain not only Pt–M9 interactions but also S–M9 bonds. However, the way in which the platinum and [M9] fragments are connected is dependent on the [M9] moiety used.These results are in sharp contrast with the behaviour of [Pt{CH2C6H4P(C6H4Me-o)2}- (S2CZ)] (Z = NMe2, OEt) towards HgX2 (X = Br, I) which results in the formation of the 1 : 1 adducts [{Pt{CH2C6- H4P(C6H4Me-o)2}(S2CZ)HgX(m-X)}2] (Z = NMe2, OEt; X = Br, I) in which the platinum fragments were connected to mercury through unsupported PtÆHg donor–acceptor bonds.9b Finally, it should be noted that given that palladium complexes are not so prone to form Pd–Ag bonds, the structure of the analogous Pd–Ag derivatives and the way in which the palladium substrates are connected to the silver fragment could be rather diVerent to that of the platinum complexes described above and should be established by X-ray diVraction study.15 Experimental General procedures and materials Elemental analyses were determined using a Perkin-Elmer 240- B microanalyzer.IR spectra were recorded on a Perkin-Elmer 599 spectrophotometer (Nujol mulls between polyethylene plates in the range 4000–200 cm21).NMR spectra were recorded on either a Varian XL-200 or a Varian Unity 300 NMR spectrometer using the standard references. [Pt{CH2C6- H4P(C6H4Me-o)2}(S2CNMe2)],9a [Pd{CH2C6H4P(C6H4Me-o)2}- (S2CNMe2)],9b [Ag(OClO3)(PPh3)] 13a and [AuCl(PPh3)] 29 were prepared by literature methods. All the reactions were carried out with exclusion of light. CAUTION Perchlorate salts are potentially explosive.Only small amounts of material should be prepared and these should be handled with great caution. [M{CH2C6H4P(C6H4Me-o)2-C,P}(S2CNMe2)AgPPh3]ClO4 (M 5 Pt 1, Pd 2) M 5 Pt (1). Method (a). [Ag(OClO3)(PPh3)] (0.1796 g, 0.38 mmol) was added to a solution of [Pt{CH2C6H4P(C6H4Me-o)2- C,P}(S2CNMe2)] A (0.2366 g, 0.38 mmol) in CH2Cl2 (30 mL) and immediately the solution turned bright yellow. After 10 min stirring in the dark the solution was evaporated almost to dryness and n-pentane added to the residue, giving 1 as a white solid (0.31 g, 75%).Method (b). To a yellow solution of [Pt2{CH2C6H4P- (C6H4Me-o)2}2(S2CNMe2)2Ag{Ag(OClO3)}]ClO4 5 (0.1525 g, 0.0923 mol) in CH2Cl2 (15 mL) was added PPh3 (0.0484 g, 0.1846 mmol). The mixture was stirred for 20 min and then the solution evaporated almost to dryness. Addition of n-pentane to the residue aVorded 1 (0.14 g, 70%) (Found: C, 46.44; H, 4.06; N, 1.41. AgC42ClH41NO4P2PtS2 requires C, 46.35; H, 3.80; N, 1.29%).(n�/cm21): 460m, 476s, 488m, 506s, 522s, 563m, 585m, 694vs, 747vs (CŸP and PPh3), 958m, 1568vs (Me2NCS2 2), 622s, 1097vs (ClO4 2). M 5 Pd (2). Method (a). [Ag(OClO3)(PPh3)] (0.1176 g, 0.2505 mmol) was added to a solution of [Pd{CH2C6H4- P(C6H4Me-o)2-C,P}(S2CNMe2)] B (0.1328 g, 0.2505 mmol) in CH2Cl2 (20 mL). The mixture was stirred in the dark for 30 min and then filtered through Celite to remove the small amount of suspended solid.Evaporation of the resulting solution to dryness and addition of Et2O to the residue aVorded 2 as a bright yellow solid (0.18 g, 72%). Method (b). To a yellow solution of [Pd2{CH2C6H4P- (C6H4Me-o)2}2(S2CNMe2)2Ag{Ag(OClO3)}]ClO4 6 (0.0761 g, 0.0516 mmol) in CH2Cl2 (25 mL) was added PPh3 (0.027 g, 0.1032 mmol) and the mixture was stirred in the dark for 45 min. Evaporation of the solution almost to dryness and addition of Et2O to the residue yielded 2 (0.0488 g, 47%) (Found: C, 50.70; H, 4.30; N, 1.30.AgC42ClH41NO4P2PdS2 requires C, 50.47; H, 4.13; N, 1.40%). (n�/cm21): 460m, 470s, 480m, 505s, 521s, 560m, 581m, 695vs, 750s (CŸP and PPh3), 963m, 1543vs (Me2NCS2 2) 623s, 1091vs (ClO4 2). [M{CH2C6H4P(C6H4Me-o)2-C,P}(S2CNMe2)Au(PPh3)]ClO4 (M 5Pt 3, Pd 4) M 5 Pt (3). A solution of [AuCl(PPh3)] (0.1979 g, 0.4 mmol) in CH2Cl2–OEt2 (30 :10 mL) was reacted with AgClO4 (0.083 g, 0.4 mmol) for 45 min and the precipitated AgCl was filtered oV. The resulting solution containing the [Au(OClO3)(PPh3)] species (0.40 mmol) was treated with [Pt{CH2C6H4P(C6H4Meo) 2-C,P}(S2CNMe2)] (0.247 g, 0.40 mmol) and the solution turned yellow immediately.After 10 min stirring at room3726 J. Chem. Soc., Dalton Trans., 1998, 3721–3726 temperature, the solution was evaporated almost to dryness and subsequent addition of OEt2 (20 mL) rendered 3 as a white solid (0.21 g, 44%) (Found: C, 43.62; H, 3.53; N, 1.23. AuC42ClH41NO4P2PtS2 requires C, 42.85; H, 3.51; N, 1.19%). (n�/cm21): 464w, 476m, 485w, 510s, 539vs, 563m, 585m, 693vs, 753vs (CŸP and PPh3), 1563vs (Me2NCS2 2), 623s, 1100vs (ClO4 2).M 5 Pd (4). Compound 4 prepared in a similar manner: [AuCl(PPh3)] (0.1139 g, 0.2302 mmol), AgClO4 (0.0477 g, 0.2302 mmol); [Pd{CH2C6H4P(C6H4Me-o)2-C,P}(S2CNMe2)] (0.122 g, 0.2302 mmol). Yield: 0.169 g, 67% (Found: C, 45.98; H, 3.62; N, 1.22. AuC42ClH41NO4P2PdS2 requires C, 46.33; H, 3.80; N, 1.28%). (n�/cm21): 461w, 469s, 510s, 536s, 559m, 579m, 693s, 753s, 761s (CŸP and PPh3), 1532vs (Me2NCS2 2), 623s, 1098vs (ClO4 2).[Pt2{CH2C6H4P(C6H4Me-o)2}2(S2CNMe2)2Ag{Ag(OClO3)}]- ClO4 5 AgClO4 (0.057 g, 0.275 mmol) was added to a solution of [Pt{CH2C6H4P(C6H4Me-o)2-C,P}(S2CNMe2)] (0.170 g, 0.275 mmol) in CH2Cl2 (25 mL) and the mixture was stirred for 8 h at room temperature. After filtration of the solid impurities, the solution was evaporated to dryness and n-pentane added to the residue giving rise to a solid which was identified as 5 (0.202 g, 89%) (Found: C, 34.84; H, 2.72; N, 1.76.Ag2C48Cl2H52- N2O8P2Pt2S4 requires C, 34.90; H, 3.17; N, 1.69%) (n�/cm21): 459m, 475m, 504w, 528w, 562m, 586m, 756s, 770s (CŸP), 950w, 1582vs (Me2NCS2 2), 623s, 1095vs (ClO4 2). Small crystals of 5?0.5CHCl3?0.125C6H14 were grown by slow diVusion of n-hexane into a CHCl3 solution of compound 5 at 5 8C. [Pd2{CH2C6H4P(C6H4Me-o)2}2(S2CNMe2)2Ag{Ag(OClO3)}]- ClO4 6 Equimolar amounts of [Pd{CH2C6H4P(C6H4Me-o)2}(S2CNMe2)] (0.139 g, 0.262 mmol) and AgClO4 (0.0543 g, 0.262 mmol) were dissolved in CH2Cl2–OEt2 (15 : 7 mL) and reacted for 4 h in the dark.The precipitated solid, 6, was filtered oV (0.1017 g, 53%) (Found: C, 38.39; H, 3.89; N, 1.84. Ag2C48Cl2- H52N2O8P2Pd2S4 requires C, 39.10; H, 3.55; N, 1.90%). (n�/cm21): 454m, 470m, 478m, 498w, 517m, 524m, 558m, 583m, 756s (CŸP), 947m, 1580vs (Me2NCS2 2), 622s, 1094vs (ClO4 2). Crystallographic studies Table 1 reports details of the structure analyses for 1?1.5CHCl3 and 5?0.5H2O?0.5CHCl3?0.125C6H14. In 1?1.5CHCl3 two rings of the PPh3 ligand show disorder in some of their carbon atoms over two sets of positions which were refined with 0.5 occupancy.Some restraints in the bond angles and thermal parameters have been applied on one of the CHCl3 solvent molecules. The largest final diVerence electron density map show two peaks (2.70, 1.08 e Å23) within 1.1 Å of the heavy atoms. In 5?0.5H2O?0.5CHCl3?0.125C6H14 all non-hydrogen atoms, except for some belonging to the solvent molecules, were assigned anisotropic displacement parameters.The second silver atom site [Ag(2)/Ag(29)] is disordered as a result of the coordination of water to one of them Ag(29) in half of the molecules. The oxygen atoms of one of the ClO4 anions are also disordered over two positions whose occupancies have been refined to 0.53(3) and 0.47(3). Finally, the CHCl3 solvent molecule is also disordered showing two orientations that share two Cl atoms.The occupancy of the non-shared atoms was set to 0.3 and 0.2. The largest final diVerence electron density features are close to the disordered CHCl3 molecule. CCDC reference number 186/1166. Acknowledgements We thank the Dirección General de Enseñanza Superior (Spain) for financial support (Project PB95-0003-C02-01). One of us (A. M.) thanks the Spanish Ministerio de Educación y Ciencia for a F.P.U. (Becas en el extranjero) grant.References 1 R. Usón and J. Forniés, Inorg. Chim. Acta, 1992, 198, 165 and references therein; R. Usón, J. Forniés, M. Tomás and I. Ara, Inorg. Chem., 1994, 33, 4023. 2 G. J. Arsenault, C. M. Anderson and R. J. Puddephatt, Organometallics, 1988, 7, 2094. 3 A. F. M. J. van der Ploeg, G. van Koten and K. Vrieze, Inorg. Chem., 1982, 21, 2026. 4 M. Ebihara, K. Tokoro, K. Imaeda, K. Sakurai, H. Masuda and K. Kawamura, J. Chem. Soc., Chem. Commun., 1992, 1592. 5 M. Ebihara, K. Tokoro, M.Maeda, M. Ogami, K. Imaeda, K. Sakurai, K. Masuda and T. Kawamura, J. Chem. Soc., Dalton Trans., 1994, 3621. 6 A. Albinati, S. Chaloupka, F. Demartin, T. F. Koetzle, H. Rüegger, L. M. Venanzi and M. K. Wolfer, J. Am. Chem. Soc., 1993, 115, 169. 7 D. Holthenrich, M. Krumm, E. Zangrando, F. Pichierri, L. Randaccio and B. Lippert, J. Chem. Soc., Dalton Trans., 1995 W. W. Yam, P. K. Y. Yeung and K. K. Cheung, Angew. Chem., Int. Ed. Engl., 1996, 35, 739. 9 (a) J.Forniés, A. Martín, R. Navarro, V. Sicilia and P. Villarroya, Organometallics, 1996, 15, 1826; (b) L. R. Falvello, J. Forniés, A. Martín, R. Navarro, V. Sicilia and P. Villarroya, Inorg. Chem., 1997, 36, 6166. 10 M. Nardelli, Comput. Chem., 1983, 7, 95. 11 R. Usón, J. Forniés, M. Tomás, I. Ara and J. M. Casas, Inorg. Chem., 1989, 28, 2388. 12 R. Usón, J. Forniés, M. Tomás, J. M. Casas, F. A. Cotton and L. R. Falvello, Inorg. Chem., 1986, 25, 4519. 13 (a) F. A. Cotton, L. R. Falvello, R. Usón, J Forniés, J. M. Tomás, J. M. Casas and I. Ara, Inorg. Chem., 1987, 26, 1366; (b) R. Usón, J. Forniés, M. Tomás, I. Ara, J. M. Casas and A. Martín, J. Chem. Soc., Dalton Trans., 1991, 2253. 14 J. E. Huheey, Inorganic Chemistry, Principles of Structure and Reactivity, Harper & Row, New York, 3rd edn., 1983. 15 J. Forniés, R. Navarro, M. Tomás and E. P. Urriolabeitia, Organometallics, 1993, 12, 940; J. Forniés, F. Martínez, R. Navarro and E. P. Urriolabeitia, Organometallics, 1966, 15, 1813. 16 D. Coucouvanis, Prog. Inorg. Chem., 1979, 26, 424. 17 B. J. Hathaway and A. E. Underhill, J. Chem. Soc., 1961, 3091. 18 A. J. Cheney and B. L. Shaw, J. Chem. Soc., Dalton Trans., 1972, 754, 860. 19 G. J. Gainsford and R. Mason, J. Organomet. Chem., 1974, 80, 395. 20 A. J. Cheney, W. S. McDonald, K. O’Flynn, B. L. Shaw and B. L. Turtle, J. Chem. Soc., Chem. Commun., 1973, 128. 21 A. L. Rheingold and W. C. Fultz, Organometallics, 1984, 3, 1414; W. A. Herrmann, C. Brossmer, K. Öfele, C.-P. Reisinger, T. Priermeier, M. Beller and H. Fischer, Angew. Chem., Int. Ed. Engl., 1995, 34, 1844. 22 M. Munakata, M. Maekawa, S. Kitagawa, M. Adachi and H. Masuda, Inorg. Chim. Acta, 1990, 167, 181. 23 M. Barrow, H.-B. Buergi, M. Camalli, F. Caruso, E. Fischer, L. M. Venanzi and L. Zambonelli, Inorg. Chem., 1983, 22, 2356. 24 S. Kitagawa, M. Kondo, S. Kawata, S. Wada, M. Maekawa and M. Munakata, Inorg. Chem., 1995, 34, 1455. 25 (a) G. Smith, A. N. Reddy, K. A. Byriel and C. H. L. Kennard, Polyhedron, 1994, 15, 2425; (b) H. Schöllhorn, U. Thewalt and B. Lippert, Inorg. Chim. Acta, 1987, 135, 155. 26 CRC Handbook of Chemistry and Physics, Chemical Rubber Publishing Co., Cleveland, 61st edn., 1980, F219. 27 R. Usón, J. Forniés, B. Menjón, F. A. Cotton, L. R. Falvello and M. Tomás, Inorg. Chem., 1985, 24, 4651. 28 C. E. Housecroft, Coord. Chem. Rev., 1992, 115, 141. 29 R. Usón and A. Laguna, Organomet. Synth., 1985, 3, 325. Paper 8/05099F

ISSN:1477-9226    

DOI:10.1039/a805099f

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, 3727–3730 3727 Resolution of a cyclopalladated ferrocenylketimine Yang Jie Wu,* Xiu Ling Cui, Chen Xia Du, Wen Ling Wang, Rui Yun Guo and Rong Feng Chen Department of Chemistry, Zhengzhou University, Zhengzhou 450052, P.R. China. E-mail: wyj@mail.zzu.edu.cn Received 19th May 1998, Accepted 23rd September 1998 The cyclopalladated ferrocenylketimine, [{Pd[(h5-C5H5)Fe{h5-C5H3C(CH3)]] N(C6H4CH3-4)}](m-Cl)}2] 1 was resolved into optically active diastereomers by using (S)-leucine as chiral auxiliary. The new optically active (S)-leucinato complexes of PdII containing ferrocenylketimine could be converted into optically active dimers with the same absolute configurations in the ferrocene moiety.The structure of the chiral dimer (Rp,Rp)-1 was determined by X-ray diVraction, on the basis of which the absolute configurations of all the optically active compounds studied were ascertained. Introduction Cyclometallated compounds are important intermediates for synthesizing ortho-disubstituted aromatic compounds as well as heterocycles.1 Chiral cyclopalladated compounds are valuable reagents for asymmetric reaction, resolution, the determination of enantiomeric excess and absolute configuration of chiral substrates.2 On the other hand, optically active ferrocene derivatives are of increasing importance in the synthesis of chiral ligands used in asymmetric catalysis and asymmetric synthesis.3 Therefore much eVort has gone into developing practical methodologies for asymmetric synthesis and resolution of cyclopalladated ferrocene derivatives, such as: (a) enantiopure ferrocenes were mainly obtained by resolution methods with a chiral amino acid;4 (b) Sokolov et al.5 have developed useful methods to aVord the planar chiral cyclopalladated ferrocene derivatives in the presence of the salts of optically active amino acids as nucleophilic catalysts.However most of the documented researches involving optically active cyclopalladated ferrocene derivatives have focused on 1-ferrocenyl- N,N-dimethylethylamine and its analogues; there have been few reports on other ligands.6 Although the cyclopalladation reaction of ferrocenylimines has been extensively studied,7 the cyclopalladated ferrocenylimines have not been resolved.In this paper will be reported the resolution and structure of a cyclopalladated ferrocenylketimine. Results and discussion A useful candidate for this study was the complex 1 prepared by the published method.7a Reaction of complex 1 with Na2CO3 and (S)-leucine gave the (S)-leucinato complex of PdII containing ferrocenylketimine as a solid in 84% yield (Scheme 1).The diastereomers 2 shown in Scheme 1 were assumed to be the trans-N, N form, similar to ortho-palladated complexes.4,8 It was found that diastereomers 2 could be resolved both by chromatography and fractional crystallization techniques and the former was a most eYcient method.Their isolation was easily achieved by chromatography of the reaction mixture on a silica gel plate developed with CH2Cl2–CH3COCH3 (1 : 1), since the diastereomer (1)-2 exhibited a higher Rf value than that of the diastereomer (2)-2. Both of the compounds were characterized by elemental analysis, IR and 1H NMR spectra. The infrared spectra of the imine showed a band at 1561 cm21. Other IR bands were found at ca. 1000 and 1100 cm21, which indicated an unsubstituted cyclopentadienyl ring.7a The IR features of the pair of diastereomers 2 were very similar.The 1H NMR spectrum of (1)-2 showed signals of H-3 at d 4.66 (d), H-4 at d 4.37 (t) and that of H-5 at d 4.60 (d), while the other (2)-2, showed peaks at d 4.72 (d), 4.38 (t) and 4.61 (d), respectively. The signal of H-3 was used as an indication of complete separation of the diastereomers. The complex (1)-[Pd{C5H5FeC5H3C(CH3)]] N(C6H4CH3- 4)}(S-LeuO)] (1)-2 was mixed with LiCl in acetic acid and stirred at room temperature for 10 min, giving (1)-1 (Scheme 2) with the same absolute configuration of the ferrocene moiety, which was confirmed by CD spectra. The CD spectra of the pair of diastereomers 2 are shown in Fig. 1 together with the CD spectrum of (1)-1. The CD spectra of the diastereomers 2 were nearly enantiomeric to each other and the CD spectrum of (1)-1 was similar to that of (1)-2, which indicated that compound (1)-1 had the same absolute configuration in the ferrocene moiety as that of (1)-2.The chiral dimer (1)-1 was air stable, soluble in dicholoromethane, acetone, and other common organic solvents. Moreover, it underwent a bridgesplitting reaction with PPh3 to produce quantitatively the Scheme 13728 J. Chem. Soc., Dalton Trans., 1998, 3727–3730 Scheme 2 Scheme 3 monomeric triphenylphosphine derivative (1)-3, a typical reaction of chloride-bridged binuclear complexes of palladium 9 (Scheme 3). The CD spectrum of (1)-3 is compared with that of (1)-1 in Fig. 2. The results also showed that the absolute configuration of the ferrocene moiety in (1)-3 was same as that in (1)-1, consistent with the addition of triphenylphosphine leading only to cleavage of the di-m-chloro bridges without breaking of Pd–C and Pd–N bonds. As has been previously described, the (S)-leucinato complexes of cyclopalladated ferrocenylimines can be successfully Fig. 1 The CD spectra of methanol solutions of (a) complexes (Rp,Rp)- 1, (b) (Rp,Sc)-2 and (c) (Sp,Sc)-2. Fig. 2 The CD spectra of methanol solutions of complexes (a) (Rp,Rp)-1 and (b) (Rp)-3. converted into dimers with the same configuration in the ferrocene moiety, but their single crystals are diYcult to obtain. Therefore, the optically active dimer (1)-1 was chosen to determine the absolute configuration by X-ray diVraction. The structure is shown in Fig. 3. Selected bond lengths and angles are listed in Tables 1 and 2, respectively.The structure shows clearly that (1)-1 is a binuclear complex of palladium, and that both the palladium atoms are linked to ortho positions of the substituted ferrocenyl rings resulting in two five membered metallocycles. The two metallocycles, which are nearly planar, form a dihedral angle of 62.708 with each other. The plane Table 1 Selected bond distances (Å) for complex (Rp,Rp)-1 Pd(1)–Cl(1) Pd(1)–N(1) Pd(2)–Cl(1) Pd(2)–N(2) Fe(1)–C(1) Fe(1)–C(3) Fe(1)–C(5) Fe(1)–C(7) Fe(1)–C(9) Fe(2)–C(20) Fe(2)–C(22) Fe(2)–C(24) Fe(2)–C(26) Fe(2)–C(28) N(1)–C(11) N(2)–C(30) C(1)–C(2) C(2)–C(3) C(3)–C(4) C(6)–C(7) C(7)–C(8) C(9)–C(10) C(20)–C(24) C(21)–C(30) C(23)–C(24) C(25)–C(29) C(27)–C(28) 2.328(3) 2.071(8) 2.490(3) 2.091(9) 2.04(1) 2.06(1) 2.06(1) 2.04(1) 2.08(1) 2.02(1) 2.05(1) 2.04(1) 2.09(1) 2.08(1) 1.30(1) 1.30(1) 1.40(2) 1.42(2) 1.44(2) 1.34(2) 1.36(2) 1.48(3) 1.42(2) 1.44(2) 1.38(2) 1.43(3) 1.42(3) Pd(1)–Cl(2) Pd(1)–C(1) Pd(2)–Cl(2) Pd(2)–C(20) Fe(1)–C(2) Fe(1)–C(4) Fe(1)–C(6) Fe(1)–C(8) Fe(1)–C(10) Fe(2)–C(21) Fe(2)–C(23) Fe(2)–C(25) Fe(2)–C(27) Fe(2)–C(29) N(1)–C(13) N(2)–C(32) C(1)–C(5) C(2)–C(11) C(4)–C(5) C(6)–C(10) C(8)–C(9) C(20)–C(21) C(21)–C(22) C(22)–C(23) C(25)–C(26) C(26)–C(27) C(28)–C(29) 2.470(3) 1.969(9) 2.321(3) 1.96(1) 2.02(1) 2.04(1) 2.04(1) 2.04(1) 2.03(2) 2.06(1) 2.03(1) 2.06(2) 2.04(2) 2.05(2) 1.43(1) 1.42(1) 1.43(1) 1.48(2) 1.42(1) 1.41(3) 1.38(3) 1.40(2) 1.44(2) 1.44(2) 1.38(3) 1.43(2) 1.41(3)J.Chem. Soc., Dalton Trans., 1998, 3727–3730 3729 Fig. 3 Molecular structure of complex (Rp,Rp)-1. Pd(1)Cl(2)Pd(2) forms a dihedral angle of 129.678 with plane Pd(2)Cl(1)Pd(1). Owing to the co-ordination between the palladium atoms and the nitrogen atoms, the angles Pd(1)– C(1)–C(2), C(1)–C(2)–C(11), Pd(2)–C(20)–C(21) and C(20)– C(21)–C(30) are decreased to 113.5, 116.8, 114.1 and 116.78, respectively, compared with the normal value of 1268.7a The Pd(1)–N(1) and Pd(2)–N(2) distances are 2.071(8) and 2.091(9) Å, respectively, suggesting the formation of Pd–N bonds.The two halves of the molecule are in a cis arrangement and exhibit Table 2 Selected bond angles (8) for complex (Rp,Rp)-1 Cl(1)–Pd(1)–Cl(2) Cl(1)–Pd(1)–C(1) Cl(2)–Pd(1)–C(1) Cl(1)–Pd(2)–Cl(2) Cl(1)–Pd(2)–C(20) Cl(2)–Pd(2)–C(20) Pd(1)–Cl(1)–Pd(2) Pd(1)–N(1)–C(11) C(11)–N(1)–C(13) Pd(2)–N(2)–C(32) Pd(1)–C(1)–Fe(1) Pd(1)–C(1)–C(5) C(1)–C(2)–C(11) N(1)–C(11)–C(2) C(2)–C(11)–C(12) N(1)–C(13)–C(15) Pd(2)–C(20)–C(21) C(22)–C(21)–C(30) N(2)–C(30)–C(31) N(2)–C(32)–C(33) 87.0(1) 92.5(3) 177.2(3) 86.6(1) 179.2(4) 93.4(4) 81.96(9) 116.4(7) 120.9(9) 121.4(7) 119.9(5) 138.7(9) 116.8(10) 112.3(9) 118.9(10) 121.9(10) 114.1(9) 133(1) 125(1) 120(1) Cl(1)–Pd(1)–N(1) Cl(2)–Pd(1)–N(1) N(1)–Pd(1)–C(1) Cl(1)–Pd(2)–N(2) Cl(2)–Pd(2)–N(2) N(2)–Pd(2)–C(20) Pd(1)–Cl(2)–Pd(2) Pd(1)–N(1)–C(13) Pd(2)–N(2)–C(30) C(30)–N(2)–C(32) Pd(1)–C(1)–C(2) C(3)–C(2)–C(11) N(1)–C(11)–C(12) N(1)–C(13)–C(14) Pd(2)–C(20)–Fe(2) Pd(2)–C(20)–C(24) C(20)–C(21)–C(30) N(2)–C(30)–C(21) C(21)–C(30)–C(31) N(2)–C(32)–C(34) 168.7(3) 100.6(2) 80.4(4) 100.5(3) 169.7(2) 79.5(5) 82.55(9) 122.2(7) 115.6(8) 122(1) 113.5(7) 133(1) 128(1) 119.2(10) 124.1(6) 138(1) 116.7(10) 113(1) 120(1) 121(1) identical planar chirality (R configuration).10 So the compound (1)-2 had the same absolute R configuration in the ferrocene moiety, and (2)-2 had the S configuration, and (1)-2, (2)-2, (1)-1 and (1)-3 were assigned as (Rp,Sc)-2, (Sp,Sc)-2, (Rp,Rp)-1 and Rp-3, respectively.Experimental General Melting points were measured on a WC-1 apparatus and are uncorrected. Elemental analyses were determined with a Carlo Erba 1160 elemental analyzer. Proton NMR spectra were recorded on a Bruker DPX 400 spectrometer using Me2SO as the solvent and SiMe4 as an internal standard, IR spectra on a Perkin-Elmer FTIR 1750 spectrophotometer. Preparative TLC was performed on dry silica gel plates developed with dichloromethane–acetone (1 : 1).Optical rotations at 5890 Å were determined by a Perkin-Elmer 341 polarimeter at 20 8C. The CD spectra were recorded on GJASCO J-20C automatic recording spectropolarimeter at 20 8C. Syntheses [Pd{C5H5FeC5H3C(CH3)]] N(C6H4CH3-4)}(S-LeuO)] 2. To a methanol suspension (10 ml) of complex 1 (1.0 g, 1.1 mmol) was added a slight excess of (S)-leucine (0.16 g, 1.2 mmol) and Na2CO3 (0.13 g, 1.2 mmol) and stirred for 6 h at room temperature until the solution became clear.After evaporation of the solvent in vacuo the crude residue was treated with CH2Cl2 in order to remove the unchanged amino acid. Further evapor-3730 J. Chem. Soc., Dalton Trans., 1998, 3727–3730 ation of the CH2Cl2 and treatment of the residue with CH2Cl2– light petroleum (bp 60–90 8C) (1 : 3) aVorded a 1 : 1 mixture of diastereomers 2 in 84% yield. Their separation was easily achieved by TLC of the mixture on a silica gel plate developed with dichloromethane–acetone (1: 1); the first band was (Rp,Sc)-2, the second (Sp,Sc)-2.(Rp,Sc)-(1)-[Pd{C5H5FeC5H3C(CH3)]] N(C6H4CH3-4)}(SLeuO)] (Rp,Sc)-2: red crystals, mp >250 8C (decomp.), [a]D 20 12209.3 deg cm3 g21 dm21 (c 0.0086 g per 100 ml in CH3OH), Rf 0.68 (Found: C, 54.32; H, 5.48; N, 5.15. Calc. for C25H30- FeN2O2Pd: C, 54.32; H, 5.47; N, 5.07%). IR(KBr): 3287, 3091, 2955, 2867, 1619, 1561, 1508, 1474, 1106, 1001, 817, 722 and 669 cm21. 1H NMR: d 4.66 (d, 1 H, J = 2.0, H-3), 4.60 (d, 1 H, J = 2.4, H-5), 4.37 (t, 1 H, J = 2.2, H-4), 4.32 (s, 5 H, H-19), 7.17 (d, 2 H, J = 8.0, NC6H4), 7.00 (d, 2 H, J = 8.0, NC6H4), 2.05 (s, 3 H, CH3); 2.31 (s, 3 H, CH3), 1.53 [m, 1 H, CH(CH3)2], 1.66 (m), 1.85 (m, 2 H, CH2), 3.20 (m, 1 H, NH2CH), 0.88, 0.86 [d, 6 H, J = 6.6 Hz, (CH3)2CH]. (Sp,Sc)-(2)-[Pd{C5H5FeC5H3C(CH3)]] N(C6H4CH3-4)}(SLeuO)] (Sp,Sc)-2: red crystals, mp >250 8C (decomp.), [a]D 20 22344.8 deg cm3 g21 dm21 (c 0.0116 g per 100 ml in CH3OH), Rf 0.58 (Found: C, 54.32; H, 5.42; N, 5.12.Calc. for C25H30- FeN2O2Pd: C, 54.32; H, 5.47; N, 5.07%). IR(KBr): 3290, 3092, 2954, 2868, 1618, 1561, 1508, 1471, 1106, 1001, 815, 720 and 669 cm21. 1H NMR: d 4.72 (d, 1 H, J = 2.0, H-3), 4.61 (d, 1 H, J = 2.4, H-5), 4.38 (t, 1 H, J = 2.2, H-4), 4.32 (s, 5 H, H-19), 7.18 (d, 2 H, J = 8.0, NC6H4), 6.98 (d, 2 H, J = 8.0, NC6H4), 2.06 (s, 3 H, CH3), 2.32 (s, 3 H, CH3), 1.68 [m, 1 H, CH(CH3)2], 1.92, 1.78 (m, 2 H, CH2), 3.17 (m, 1 H, NH2CH), 0.95, 0.99 [2d, 6 H, J = 6.4 Hz, (CH3)2CH].Rp,Rp-(1)-[{PdCl[C5H5FeC5H3C(CH3)]] N(C6H4CH3-4)]}2] (Rp,Rp)-1. A methanol solution (1 ml) of 0.1 g of complex (Rp,Sc)- 2 and 2 mol of LiCl was mixed with acetic acid (6 ml). The mixture was stirred at room temperature for about 10 min, then filtered, and washed with light petroleum three times. The solid obtained was recrystallized from CH2Cl2–light petroleum (bp 60–90 8C) to produce compound (Rp,Rp)-1.Red crystals, yield 92.4%, mp >210 8C (decomp.), [a]D 20 13212.5 deg cm3 g21 dm21 (c 0.0080 g per 100 ml in CHCl3) (Found: C, 49.92; H, 3.91; N, 2.93. Calc. for C19H18ClFeNPd: C, 49.82; H, 3.96; N, 3.06%). IR(KBr): 3090, 2920, 1551, 1508, 1474, 1105, 999, 817, 721 and 693 cm21. 1H NMR: d 5.14 (2 H, H-3), 4.73 (2 H, H-5), 4.48 (2 H, H-4), 4.38 (s, 10 H, H-19), 2.01 (s, 6 H, CH3), 2.31 (s, 6 H, CH3), 7.14 (d, 4 H, J = 8.0, NC6H4) and 6.94 (d, 4 H, J = 6.8 Hz, NC6H4).Compound (Rp)-3. This was prepared by the published method.7a Red crystals, yield 79.2%. mp >220 8C (decomp.). [a]D 20 11704.5 deg cm3 g21 dm21 (c 0.0088 g per 100 ml in CHCl3) (Found: C, 61.48; H, 4.67; N, 1.93. Calc. for C37H33ClFeNPPd: C, 61.72; H, 4.62; N, 1.94%). IR(KBr): 3067, 3049, 2921, 1569, 1507, 1480, 1094, 998, 817, 758 and 700 cm21. 1H NMR: d 3.15 (1 H, H-3), 4.65 (1 H, H-5), 4.17 (1 H, H-4), 3.30 (s, 5 H, H-19), 2.05 (s, 3 H, CH3); 2.31 (s, 3 H, CH3), 7.15 (d, 2 H, J = 7.6, NC6H4), 6.89 (d, 2 H, J = 7.6 Hz, NC6H4), 7.48 m, 7.70 m (15 H, PPh3).Crystal structure determination of complex (Rp,Rp)-1 Crystal data. C38H36Cl2N2Fe2Pd2, M = 916.12, red prismatic, crystal size 2.70 × 0.10 × 1.00 mm, monoclinic, space group P21 (no. 4), a = 11.64(1), b = 12.083(2), c = 13.004(2) Å, b = 94.445(3)8, Z = 2, V = 1824.1 Å3, Dc = 1.668 g cm23, F(000) = 912, m(Mo-Ka) = 19.25 cm21. Data collection. All measurements were made on a Rigaku RAXIS-IV imaging plate area detector with graphite monochromated Mo-Ka radiation (l = 0.71070 Å).The data were collected at 15 ± 1 8C to a maximum 2q value of 55.08. A total of 45 images of 4.008 oscillation were collected, each being exposed for 16.0 min. The crystal-to-detector distance was 110.00 mm with the detector at the zero swing position. The data were corrected for Lorentz-polarization eVects. The structure was solved by direct methods 11 and expanded using Fourier techniques.The non-hydrogen atoms were refined anisotropically. Hydrogen atoms were included but not refined. The final cycle of full-matrix least-squares refinement was based on 3374 observed reflections [I > 3.00s(I)] and 416 variable parameters. The function minimized was Sw(|Fo| 2 |Fc|)2. The maximum and minimum peaks on the final Fourierdi Verence map corresponded to 1.89 and 21.45 e Å23, respectively. The absolute configuration of complex (Rp,Rp)-1 was confirmed by the significance of the diVerence between the two sigma weighted R factors, as judged by the Hamilton test.12 The final R factors were 0.042 (R9 = 0.062) and 0.043 (0.063) for the R and S configuration in the ferrocene moiety, respectively.All calculations were performed using the TEXSAN crystallographic software package.13 CCDC reference number 186/1177. See http://www.rsc.org/suppdata/dt/1998/3727/ for crystallographic files in .cif format. Acknowledgements We are grateful to the National Science Foundation of China (Project 29592066) and the Natural Science Foundation of Henan Province for financial support.We thank Professors V. I. Sokolov, Weiwei Huang and Hongwen Hu for valuable dicussion. References 1 M. I. Bruce, Angew. Chem., Int. Ed. Engl., 1977, 16, 73; C. H. Chao, D. W. Hast, R. Bau and R. F. Heck, J. Organomet. Chem., 1979, 179, 301; N. Beydoun and M. PfeVer, Synthesis, 1990, 729; M. PfeVer, J. P. Sutter, A. Decian and J. Fischer, Organometallics, 1993, 12, 1167. 2 S. Y. M. Chooi, P. H. Leung, C. C. Lim, K. F. Mok, G. H. Quek, K. Y. Sim and M. K. Tam, Tetrahedron: Asymmetry, 1992, 3, 529; S. Y. M. Chooi, S. Y. Siah, P. H. Leung and K. F. Mok, Inorg. Chem., 1993, 32, 4812; J. L. Bookham and W. Mcfarlane, J. Chem. Soc., Chem. Commun., 1993, 1352; D. G. Allen, G. M. Mclaughlin, G. B. Robertson, W. L. SteVen, G. Salem and S. B. Wild, Inorg. Chem., 1982, 21, 1007; R. T Aplin, H. Doucet, M. W. Hooper and J. M. Brown, Chem.Commun., 1997, 2097. 3 V. I. Sokolov, L. L. Troitskaya and O. A. Reatov, J. Organomet. Chem., 1979, 182, 537; T. Hayashi and M. Kumada, Asymmetric Synthesis, Academic Press, Inc., Orlando, FL, 1985, vol. 5, p. 147; A. Togni and T. Hayashi, Ferrocenes: Homogeneous Catalysis, Organic Synthesis and Materials Science, VCH, Weinheim, 1995, p. 105 and refs. therein; K. H. Ahn, C. W. Cho, H. H. Baek, J. Park and S. Lee, J. Org. Chem., 1995, 61, 4937. 4 T. Komatsu, M. Nonoyama and J. Fujita, Bull. Chem. Soc. Jpn., 1981, 54, 184. 5 V. I. Sokolov, L. L. Troitskaya and O. A. Reatov, J. Organomet. Chem., 1977, 133, C28. 6 A. Patti, D. Lambusta, M. Piattelli and G. Nicolosi, Tetrahedron, 1997, 53, 1361. 7 (a) S. Q. Huo, Y. J. Wu, C. X. Du, H. Z. Yuan and X. A. Mao, J. Organomet. Chem., 1994, 483, 139; (b) Y. J. Wu, Y. H. Liu, H. Z. Yuan and X. A. Mao, Polyhedron, 1996, 15, 3315; (c) C. López, J. Sales, X. Solans and R. Zquiak, J. Chem. Soc., Dalton Trans., 1992, 2321. 8 R. Navarro, J. Garcia, E. P. Urriolabeitia, C. Catviela and M. D. Diaz-de-Villegas, J. Organomet. Chem., 1995, 490, 35. 9 J. C. Gaunt and B. L. Shaw, J. Organomet. Chem., 1975, 102, 511; A. Kasahara, T. Izumi and M. Maemura, Bull. Chem. Soc. Jpn., 1977, 50, 1878. 10 K. Schlögl, M. Fried and H. Falk, Monatsh. Chem., 1964, 95, 576. 11 SIR 92, A. Altomare, M. C. Burla, M. Camalli, M. Cascarano, C. Giacovazzo, A. Guagliardi and G. Polidori, J. Appl. Crystallogr., 1994, 27, 435. 12 W. C. Hamilton, Acta Crystallogr., 1965, 18, 502. 13 TEXSAN, Crystal Structure Analysis Package, Molecular Structure Corporation, Houston, TX, 1985 and 1992. Paper 8/03739F

ISSN:1477-9226    

DOI:10.1039/a803739f

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, 3731–3736 3731 Synthesis, X-ray crystal structure and spectroscopic characterization of the new dithiolene [Pd(Et2timdt)2] and of its adduct with molecular diiodine [Pd(Et2timdt)2]?I2?CHCl3 (Et2timdt 5 monoanion of 1,3-diethylimidazolidine-2,4,5-trithione) Massimiliano Arca,a Francesco Demartin,b Francesco A. Devillanova,*a Alessandra Garau,a Francesco Isaia,a Francesco Lelj,c Vito Lippolis,a Samuele Pedraglio b and Gaetano Verani a a Dipartimento di Chimica e Tecnologie Inorganiche e Metallorganiche, Via Ospedale 72, 09124 Cagliari, Italy.E-mail: devilla@vaxca1.unica.it b Dipartimento di Chimica Strutturale e Stereochimica Inorganica e Centro CNR, Via G. Venezian 21, 20133 Milano, Italy c Dipartimento di Chimica, Via N. Sauro 85, 85100 Potenza, Italy Received 15th July 1998, Accepted 14th September 1998 The first Pd dithiolene [Pd(Et2timdt)2] 4a belonging to the new class of metal dithiolenes deriving from the R1 2timdt (R1 2timdt = monoanion of 1,3-dialkylimidazolidine-2,4,5-trithione) ligand has been characterised by X-ray crystal structure determination on a single crystal [monoclinic, space group P21/n, a = 9.545(2), b = 5.417(2), c = 20.093(4) Å, b = 93.40(2)8, Z = 2], UV–VIS–NIR, diVuse solid state reflectance, FTIR, FT-Raman spectroscopies, solid state 13C NMR and cyclic voltammetry and the results have been comparatively discussed with those obtained for the analogous [Ni(Et2timdt)2] 4b.The UV–VIS–NIR spectrum of 4a is dominated by a very intense absorption band at 1010 nm (e = 70 000 dm3 mol21 cm21). The NIR features of 4a and 4b have been examined on the basis of the electronic structure of their ground-state configurations, investigated by DFT calculations. The co-crystallisation of 4a with I2 yielded the [Pd(Et2timdt)2]?I2?CHCl3 6 adduct [monoclinic, space group C2/m, a = 21.724(9), b = 12.901(4), c = 11.004(6) Å, b = 102.83(4)8, Z = 4].No short metal–metal interaction was observed in both 4a and 6 (Pd ? ? ? Pd 5.42 Å in 4a and 5.25 Å in 6), since each palladium ion is almost ‘sandwiched’ between two imidazolidine rings of parallel adjacent molecules. In coordination chemistry metal dithiolenes represent a very interesting class of complexes. Because of their large p delocalization they exhibit uncommon properties, such as intense VISNIR absorption, high thermal and spectrochemical stability, and electrical conductivity.1–3 In addition they can exist in well defined oxidation states, neutral, mono- and di-anionic.4 Since the p electron delocalization involves the organic ligand atoms as well as the metal centre, these molecules have to be considered highly aromatic.In particular the frequency of the intense VIS–NIR absorption is assigned to a p æÆ p* transition between HOMO and LUMO5 and depends on the nature of the substituents R1 on the carbon atoms of the [S2C2R1 2]22 moiety.It has been shown that accepting substituents shift this absorption to lower energies 5 compared with the value found for the so-called parent dithiolene [Ni(S2C2H2)2] (720 nm, e = 14 000 dm3 mol21 cm21) 6,7 where R1 = H. Recently, some neutral Ni complexes belonging to the new class of metal dithiolenes [M(R1 2timdt)2] (R1 2timdt = monoanion of 1,3-dialkylimidazolidine- 2,4,5-trithione; R1 = Et, Pri, Bu) have been reported.8 These complexes are characterized by a very strong absorption at 1000 nm with absorption coeYcient values up to 80 000 dm3 mol21 cm21 for [Ni(Pri 2timdt)2] (R1 = Pri, 4c),9 the highest values ever observed in similar compounds.The closeness of this frequency to that of the Nd-YAG laser (excitation wavelength 1064 nm) makes these complexes very good candidates for technological applications, such as Q-switching 10 for NIR-lasers or NIR dyes.5 With the aim to prepare complexes of this class having the NIR absorption as close as possible to the laser excitation energy, we first tried metal substitution as a synthetic tool.In this paper [Pd(Et2timdt)2] 4a, the first Pd complex belonging to this new class of dithiolenes is fully characterized together with its analogue [Ni(Et2timdt)2] 4b. In order to obtain mixed-valence compounds of 4a, which might have interesting conducting properties, we have reacted it with diiodine in several molar ratios, according to the same method successfully used for some Ni dithiolenes of the same class.9 Among the products, only [Pd(Et2timdt)2]?I2?CHCl3 6 has been characterized by X-ray diVraction and it is discussed in this paper.Experimental All solvents and reagents were of the best Aldrich quality and were used as purchased. All operations were carried out under dry nitrogen atmosphere. Infrared spectra were recorded on a Bruker IFS55 spectrometer at room temperature. Polythene pellets with a Mylar beam-splitter and polythene windows (500–50 cm21, resolution 2 cm21) and KBr pellets with a KBr beam-splitter and KBr windows (4000–400 cm21, resolution 4 cm21) were used.FT-Raman spectra (resolution 4 cm21) were recorded on a Bruker RFS100 FT-Raman spectrometer, fitted with an In–Ga–As detector (room temperature) operating with a Nd-YAG laser (excitation wavelength 1064 nm) with a 1808 scattering geometry. Electronic spectra (CHCl3 solution; 20 8C ) were recorded on a Cary 5 spectrophotometer. DiVuse reflectance measurements were recorded as KBr pellets.CP MAS solid state 13C NMR spectra were recorded on a Varian Unity Inova 400 MHz instrument operating at 100.5 MHz with samples packed into a zirconium oxide rotor. The 13C chemical shifts were calibrated indirectly through the adamantane peaks (d 38.3, 29.2) related to SiMe4. Cyclic voltammograms were recorded using an EG&G Model 273 at 25 8C in a Metrohm voltammetric cell with a combined working and counter platinum electrode and a standard Ag/AgCl (in 3.5 M KCl)3732 J.Chem. Soc., Dalton Trans., 1998, 3731–3736 reference electrode (anhydrous CH2Cl2; sample concentration 1 × 1024 mol dm23; supporting electrolyte tetrabutylammonium tetrafluoroborate 1 × 1022 mol dm23). Cyclic voltammograms were recorded at scan rates ranging from 0.02 to 0.7 V s21. Density functional calculations 11–13 were performed using the hybrid B3LYP functional 14,15 with the Gaussian 94 package 16 and the Shafer et al.17 VDZ basis set.The SCF procedure was performed on an optimized geometry starting from structural data, regularized in order to satisfy the D2h symmetry. Calculations were performed on an IBM Risc 6000 550H, DECServer 4000 and on a SEH Pentium 133 MHz computer. Synthesis The synthesis of 4a and 4b can be accomplished either by metal halides or by metal powder (Scheme 1) as previously described.8,9 [Pd(Et2timdt)2] 4a. Method (a). A mixture of 1,3-diethylimidazolidine- 2-thione-4,5-dione 18 (1, R = Et; 1 g, 5.38 mmol), an equivalent amount of Lawesson’s reagent (2) and a little excess of Pd powder was refluxed in anhydrous toluene (100 mL) for 8 h.The concentrated suspension was poured in about 100 mL of MeOH, from which, after 3 h at 4 8C, the solid was filtered, dried and extracted for 2 days with CHCl3 in a Soxhlet apparatus (0.274 g, 18% yield). Method (b). A stirred suspension of 1,3-diethylimidazolidine- 2-thione-4,5-dione (1, R = Et; 0.50 g, 2.68 mmol), stoichiometric amounts of Lawesson’s reagent (2), and PdCl2 in 40 mL of toluene was refluxed for 30 min, concentrated under a nitrogen stream and poured in 40 mL of EtOH. The crystalline precipitate was separated (0.44 g, 61% yield).Needle-shaped dark crystals suitable for X-ray diVraction analysis were grown from a CHCl3–Me3CN (2: 1 v/v ratio) solution. Mp > 290 8C [Found (Calc. for C14H20N4PdS6): C, 31.0 (31.0); H, 3.8 (3.7); N, 10.2 (10.3); S, 35.2 (35.4)%].Electronic spectrum in CHCl3: l (e) 274(60 600), 336(55 500), 510(11 440), 534(11 600), 654(4530), 746(4790), 1012nm (69 600 dm3 mol21 cm21). Solid state FTIR: n/cm21 2973w, 2932w, 2869vw, 1444w, 1413vs, 1389vs, 1375vs, 1351vs, 1294vs, 1258vs, 1177m, 1152m, 1104s, 1081s, 976w, 954m, 807m, 752w, 567w, 428s, 410vw, 392m. Scheme 1 Reagents and conditions: i, Metal powder or metal halide, toluene, heat; ii, R2OH after concentration. N N R1 R1 S O O 1 MeO P S P S S S OMe 2 S S S S N N N N S S R1 R1 R1 R1 + i,ii Toluene heat 3 N N S M S S S N N S S R1 R1 R1 R1 4a M = Pd, R1 = Et 4b M = Ni, R1 = Et 4c M = Ni, R1 = Pri + 3 + MeO P S R2O S M S P S OMe OR2 5 Raman spectrum (in the range 500–100 cm21; relative intensities in parentheses, strongest = 10): n/cm21 431(10), 341(7.2).Solid state 13C NMR (atom labelling according to Fig. 1): d 14.9 [C(12), C(129), C(32), C(329)], 41.2 [C(11), C(119), C(31), C(319)], 166.6 [C(4), C(49), C(5), C(59)], 172.5 [C(2), C(29)].[Ni(Et2timdt)2] 4b. This olive-green compound can be prepared from nickel powder (yield 20%) as previously reported.8,9 Mp 270 8C (decomp.) [Found (Calc. for C14H20N4NiS6): C, 33.6 (33.9); H, 4.1 (4.1); N, 11.1 (11.3); S, 38.8 (38.8)%]. Electronic spectrum in CHCl3: l (e) 262(17 800), 300(31 300), 340(42 110), 434(8660), 462(9165), 996 nm (76 500 dm3 mol21 cm21). Solid state FTIR: n/cm21 2972w, 2961vw, 2932w, 2869vw, 1416s, 1391vs, 1376vs, 1350vs, 1288vs, 1255vs, 1180m, 1105s, 1081s, 977w, 953m, 809vw, 795w, 661w, 568w, 435s, 404vw, 390w, 378m.FT-Raman spectrum (in the range 500–100 cm21; relative intensities in parentheses, strongest = 10): n/cm21 435(6.1), 327(10), 139(3). Solid state 13C NMR (atom labelling analogue to that used for 4a in Fig. 1): d 14.8, 14.0 [C(12), C(129), C(32), C(329)], 41.8 [C(11), C(119), C(31), C(319)], 162.5 [C(4), C(49), C(5), C(59)], 169.8 [C(2), C(29)]. [Pd(Et2timdt)2]?I2?CHCl3 6. A solution of 4a (14 mg, 2.58 × 1025 mol) and I2 (19 mg, 7.48 × 1025 mol) in CHCl3 (40 mL) was slowly air evaporated.After a few days, dark needle-shaped crystals were separated and washed with light petroleum (bp 60–80 8C). Mp 260 8C (decomp.) [Found (Calc. for C15H21- Cl3I2N4PdS6): C, 20.1 (19.7); H, 2.2 (2.3); N, 5.9 (6.1); S, 20.8 (21.0)%]. The spectroscopic features resemble those of 4a. Crystallography A summary of the crystallographic data is given in Table 1. Data collections were performed on an Enraf-Nonius Cad-4 diVractometer. Lorentz, polarization and empirical absorption corrections 19 were applied to the data.A linear correction for a slight decay, due to the loss of solvent molecules during data collection was also applied for 6. All the hydrogen atoms, with the exception of that of the CHCl3 molecule were introduced in the structure model and not refined. Scattering factors were taken from Cromer and Waber.20 Anomalous dispersion eVects were included in Fc; the values for df 9 and df 0 were those of Cromer.21 All calculations were performed on a 80486/33 computer using Personal SDP software.22 CCDC reference number 186/1161. See http://www.rsc.org/suppdata/dt/1998/3731/ for crystallographic files in .cif format.Results and discussion It has already been shown that cyclic pentaatomic vicinal dithiones are not isolable,23,24 therefore any conventional method of synthesis starting from them is not suitable for the preparation of [M(R1 2timdt)2] dithiolenes.To overcome this obstacle, we have developed a one-step route leading to the complex 4 based on the sulfuration of 1,3-dialkylimidazolidine- 2-thione-4,5-diones 25 (1) with Lawesson’s reagent 26 (2) in the presence of a metal halide or metal powder (Scheme 1).8,9 However, the yields of these reactions are generally low owing to the formation of several by-products, among which the tetrathiocino derivatives 27 (3) and the trans-bis[O-alkyl (4-methoxyphenyl) phosphonodithioate 28 (5) have been identified.In the synthesis of Ni dithiolenes, the use of Ni powder leads to higher yields 9 compared to NiCl2 (yield for 4b: 20% from Ni; 10% from NiCl2). Surprisingly, in the synthesis of 4a a very high yield is obtained using PdCl2 as a starting material (yield 18% from Pd; 61% from PdCl2). Description of the structures of 4a and 6. Selected interatomic distances and angles for 4a and its adduct with diiodine 6 areJ.Chem. Soc., Dalton Trans., 1998, 3731–3736 3733 Table 1 Crystallographic data for compounds 4a and 6 Compound Formula M Crystal system Space group a/Å b/Å c/Å b/8 V/Å3 ZT /K Dc/g cm23 m(MoKa)/cm21 Data/parameters ratio Final R and Rw indices a Min./max. height in final Dr map/e Å23 4a C14H20N4PdS6 543.13 Monoclinic P21/n (no. 14) 9.545(2) 5.417(2) 20.093(4) 93.40(2) 1037.1(6) 2 293(1) 1.74 14.7 1031/115 0.042, 0.043 20.43(11)/0.61(11) 6 C15H21Cl3I2N4PdS6 916.31 Monoclinic C2/m (no.12) 21.724(9) 12.901(4) 11.004(6) 102.83(4) 3007(2) 4 293(1) 2.02 33.3 1272/154 0.053, 0.064 20.65(13)/1.31(13) a R = [S(Fo 2 k|Fc|)/SFo], Rw = [Sw(Fo 2 k|Fc|)2/SwFo 2]� �� .given in Table 2. The molecular structure of 4a is shown in Fig. 1. The molecule, which has an idealised C2h symmetry, is located about a crystallographic inversion centre. The Pd atom displays a square planar coordination, which involves the two vicinal sulfur atoms of each of the two chelating ligands.The interatomic distances of the ring, compared with those previously reported for 4c,9 are almost unaVected by the change of the metal. DiVerently from some other Pd and Pt dithiolenes, such as [Pd(S2C2H2)2] and [Pt(S2C2H2)2],29,30 where short metal– metal distances are found,31 no interaction is observed here Table 2 Selected interatomic distances (Å) and angles (8) for compounds 4a and 6 4a Pd–S(1) S(1)–C(4) S(3)–C(2) N(3)–C(4) N(1)–C(2) N(1)–C(11) S(1)–Pd–S(2) Pd–S(1)–C(4) S(1)–C(4)–C(5) C(5)–N(1)–C(2) N(1)–C(5)–C(4) S(3)–C(2)–N(1) N(1)–C(2)–N(3) 2.295(2) 1.692(8) 1.648(8) 1.372(9) 1.378(9) 1.448(9) 92.49(7) 98.9(3) 125.0(6) 110.7(6) 107.1(7) 127.1(6) 105.3(6) Pd–S(2) S(2)–C(5) C(4)–C(5) N(1)–C(5) N(3)–C(2) N(3)–C(31) S(1)–Pd–S(29) Pd–S(2)–C(5) S(2)–C(5)–C(4) C(4)–N(3)–C(2) N(3)–C(4)–C(5) S(3)–C(2)–N(3) 2.294(2) 1.687(8) 1.397(9) 1.367(8) 1.394(9) 1.466(9) 87.51(7) 99.4(3) 124.2(6) 109.8(6) 107.2(7) 127.6(6) Symmetry code: 9 2x, 2y, 2z. 6 I(1)–I(2) Pd–S(1a) S(1a)–C(1a) S(2a)–C(2a) N(1a)–C(1a) N(1a)–C(2a) C(1a)–C(1a9) S(2b) ? ? ? I(20) S(1a)–Pd–S(1a9) S(1a)–Pd–S(1b) Pd–S(1a)–C(1a) S(1a)–C(1a)–C(1a9) N(1a)–C(1a)–C(1a9) C(1a)–N(1a)–C(2a) N(1a)–C(2a)–N(1a9) S(2a)–C(2a)–N(1a) I(1)–I(2)–S(2a) I(20) ? ? ? S(2b)–C(2b) I(1-) ? ? ? I(1)–I(2) 2.811(2) 2.287(3) 1.697(9) 1.740(15) 1.382(10) 1.327(10) 1.343(19) 4.004(4) 93.0(1) 87.4(1) 97.9(3) 125.6(3) 107.5(5) 107.5(9) 109.9(12) 125.0(6) 179.6(1) 174.6(5) 178.50(8) I(2)–S(2a) Pd–S(1b) S(1b)–C(1b) S(2b)–C(2b) N(1b)–C(1b) N(1b)–C(2b) C(1b)–C(1b9) I(1) ? ? ? I(1-) S(1b)–Pd–S(1b9) S(1a)–Pd–S(1b9) Pd–S(1b)–C(1b) S(1b)–C(1b)–C(1b9) N(1b)–C(1b)–C(1b9) C(1b)–N(1b)–C(2b) N(1b)–C(2b)–N(1b9) S(2b)–C(2b)–N(1b) I(2)–S(2a)–C(2a) I(10)–I(20) ? ? ? S(2b) 2.875(5) 2.286(3) 1.689(9) 1.626(12) 1.339(10) 1.388(9) 1.403(18) 3.978(3) 92.1(1) 179.4(1) 99.9(3) 124.0(3) 106.9(6) 111.3(9) 103.6(10) 128.1(5) 98.3(5) 88.3(1) Symmetry codes: 9 x, 2y, z; 0 1 2 x, 2y, 2z; - 2 2 x, 2y, 1 2 z.(Pd ? ? ? Pd 5.42 Å), but each Pd atom is almost ‘sandwiched’ between two imidazolidine rings of parallel adjacent molecules, with a metal–ring distance corresponding to an interplanar spacing of about 3.6 Å. The adduct 6 (shown in Fig. 2) has crystallographic Cs symmetry, with the Pd, C(2a), C(2b), S(2a), S(2b) and the diiodine atoms lying on the mirror plane. With the exception of the ethyl groups, the Pd complex is essentially planar; the Pd atom is only 0.008(1) Å out of its coordination plane, whereas the two pentaatomic metallacycles and the imidazolidine rings are exactly planar.The ethyl substituents in 6 are ed in the same way as for 4a. The complex molecule interacts with diiodine through the exocyclic sulfur atom S(2a) with an S(2a)–I(2) distance of 2.875(5) Å and induces a lengthening of 0.16 Å in the I–I bond with respect to solid I2. This is a value similar to those found in the charge-transfer complexes of thiones with diiodine.In fact, the d[S(2a)– I(2)] and d[I(2)–I(1)] bond distances fit the correlation found for many charge-transfer complexes between sulfur donors and diiodine.32 The S(2b) atom, instead, is only involved in a soft Fig. 1 Molecular structure of complex 4a. Fig. 2 View of compound 6 showing the soft interaction with the iodine of another adduct. The chloroform molecule has been omitted.3734 J. Chem. Soc., Dalton Trans., 1998, 3731–3736 interaction with the iodine of another adjacent adduct [S(2b) ? ? ? I(20) 4.004(4) Å].As a result of the asymmetric interactions, the two imidazolidine moieties are significantly diVerent. In particular C(2a)–S(2a) is about 0.1 Å elongated with respect to C(2b)–S(2b), and the two pentaatomic rings show diVerences both in the bond distances and in the angles, indicating a charge redistribution in the p system. In fact, the interatomic distances found in ligand (a) resemble those found in the adduct [Ni(Pri 2timdt)2]?2.5I2 7 9 [C(1a)–S(1a) 1.697(9) vs. 1.71(2) Å; C(1a)–C(1a9) 1.34(2) vs. 1.33(4) Å; C(2a)–N(1a) 1.33(1) vs. 1.34(3) Å; S(2a)–I(2) 2.875(5) vs. 2.825(6) Å], in which both the terminal thioketonic sulfurs strongly interact with two diVerent diiodine molecules, whereas the interatomic distances of the ligand (b) are close to those observed in 4a (Table 2). The [Pd(Et2timdt)2]?I2 adduct molecules are located about the crystallographic mirrors passing at y = 0, y = 1, etc., to form molecular layers stacked along [010].Between these layers, there are clathrated chloroform molecules lying on the crystallographic mirror at y = 0.5. The pattern of the adduct molecules within each layer can be seen in Fig. 3: the complex molecules are arranged on parallel planes, with an interplanar distance of about 3.6 Å. The diiodine molecules are almost normal to these planes. The adduct molecules form rows running along [001], interconnected by I(1) ? ? ? I(1) interactions of 3.978(3) Å.As for 4a, the Pd atoms are ‘sandwiched’ between two imidazolidine rings of parallel adjacent molecules and again no short interaction is found between the Pd atoms (Pd ? ? ? Pd 5.25 Å). The CP MAS 13C NMR spectra recorded for 4a and 4b show the same features, the only diVerence being the slight splitting of the peaks assigned to the aliphatic carbons of 4b. Unfortunately we have not been able to obtain structural data for 4b, but this splitting may indicate a diVerent orientation of ethyl groups compared to 4a.UV–VIS–NIR spectroscopy and DFT calculations The most striking property observed in Ni dithiolenes deriving from the R1 2timdt ligands is their very intense NIR-absorption. In chloroform solution, 4b shows a very strong peak at 996 nm (e = 76 500 dm3 mol21 cm21), whereas the peak of 4a is shifted in the desired direction at slightly but appreciably higher wavelengths (1010 nm, e = 70 000 dm3 mol21 cm21, Fig. 4). A remarkable diVerence appears in the visible region, due to the diVerent position of the d–d bands. As a consequence, while Ni dithiolenes are olive-green, the new Pd dithiolene is purple. The position of the NIR band is unchanged in the solid state, as shown by diVuse reflectance measurement, and the spectral properties of compound 6 in the solid state are the same as for 4a. The characteristic VIS–NIR band has been the subject of many studies 4,33,34 in related simpler compounds and has been generally assigned to a p–p* transition.In view of a better understanding of the nature of the absorption, a DFT approach using a hybrid functional has been used. Hybrid- DFT computations have been shown to work nicely with transition metals 35 both in the ground state and in the excited state.36 To understand the eVect of the R1 2timdt bulky ligand, the calculations have been performed both on the parent [Ni(S2C2H2)2] Fig. 3 Crystal packing of compound 6 seen along [010].and the hypothetical [Ni(H2timdt)2] (R1 = H) dithiolenes. The calculation of the electronic structure and energy of the parent [Ni(S2C2H2)2] dithiolene describes the ground state as 1Ag. The HOMO (b1u) is a p orbital built by the four pz sulfur AOs (assuming the molecule is disposed in the xy plane) and the four pz carbon AOs taken with opposite phases. As obvious in a B1u irreducible representation, the d orbitals of the metal do not give any contribution to the HOMO; besides metal participates in this MO with its virtual 4pz orbital.The LUMO (b2g) p* orbital, instead, is fully delocalized on the whole set of atoms of the molecule and involves the nickel atom through the 3dxz orbital. The Ni atom bears a slight positive Mulliken charge (10.017 e), opposite in sign even though not very diVerent from the previous simple HF result (20.07 e).37 These results confirm the trend previously obtained 35 by the semi-empirical INDO 38 method.In [Ni(H2timdt)2], the HOMO and LUMO in the ground state (1Ag) belong to the same b1u and b2g representations, as found in the parent dithiolene. While the pz orbitals of the exocyclic sulfurs are involved both in the HOMO and in the LUMO, those of the nitrogen atoms participate only in the HOMO. Again, the metal contributes to the LUMO only with its 3dxz orbital. As in the case of the parent compounds, our calculations confirm the attribution of the intense NIR band to a p–p* transition.According to a Mulliken population, a positive charge is concentrated on the metal atom (10.101 e) and on the carbon atoms [10.022 e for those of the dithiolene system and 10.072 e for the carbon (2)]. The donor sulfur atoms are negatively charged (20.058 e) as well as the thioketonic terminal sulfurs (20.205 e). The nitrogen atoms bring a 20.067 e negative charge. As far as the energies involved in the NIR transition are concerned, since Koopman’s theorem is not valid for DFT calculations, the Kohn–Sham orbital energies cannot be used as in the case of HF calculations.Nevertheless, the energy diVerence, DE, between HOMO and LUMO orbitals can be used as a significant parameter. Thus, it can be noted that, according to the experimentally observed trend, the DE value decreases from 15 500 cm21 in the parent dithiolene to 9100 cm21 in 4b. The very close value found for 4a is easily explained when one observes that the metal contribution to the orbitals involved in the transition is indeed very small.However, the substitution of Ni by Pd has shifted the band 14 cm21 in the desired direction. Vibrational spectroscopy Neglecting the possible conformations of the arms in the [M(R1 2timdt)2] unit, the molecule belongs to the D2h point group, where the stretching normal modes of the MS4 unit belong to the Ag, B1g, B2u and B3u and the bending normal modes to 2B1g, B3u and B2u representations. In Table 3 the most important Fig. 4 UV–VIS–NIR spectra of compounds 4a (1) and 4b (——) measured in chloroform at 20 8C.J. Chem. Soc., Dalton Trans., 1998, 3731–3736 3735 Table 3 Experimental vibrational frequencies (500–50 cm21) for compounds 4a and 4b compared with those calculated for [Ni(H2timdt)2] Calculated Experimental frequencies/cm21 Raman active modes FIR active modes Mode ag stretching ag bending b1g bending b3u stretching b2u stretching b3u bending frequencies/cm21 317 446 �Ô ½ Ô� 442 366 � Ô ½ Ô � 373 435 4a 341 431 392 428 4b 327 435 378 435 calculated and experimental vibrations are summarized.The even modes are Raman active and are resonance enhanced by the NIR absorption both for 4a and 4b,9 as these compounds strongly absorb in the region of the Nd-YAG laser source. The FT-Raman spectra of 4a and 4b are dominated by two peaks both in solution and in the solid state,h spectra of better quality are obtainable in solution (341 and 431 cm21 for 4a, 327, 435 cm21 for 4b).While the first peak can be assigned to the ag stretching mode, calculated at 317 cm21 for [Ni(H2- timdt)2], the second one might be assigned to ag or to the b1g bending modes, calculated at 446 and 442 cm21 respectively. The lower frequency band shifts on passing from 4a to 4b as observed for [Pd(mnt)2]22 and [Ni(mnt)2]22 [mnt = C2S2(CN)2] (349 and 335 cm21 respectively),39 probably as a consequence of the increased metal-d/ligand-p orbital overlap, which overcomes the expected mass eVect.37 In the FIR region the bands having the highest calculated intensities in the Ni model compound fall at 435 (bending b3u), 373 (stretching b2u) and 366 cm21 (stretching b3u) with calculated relative intensities of 236, 11 and 10 respectively.In the experimental FIR spectrum of 4b two bands are present at 435vs and 378m cm21. These bands shift to 428vs and 392m cm21 in 4a. In the MIR region the spectra of 4a and 4b are almost indistinguishable, all the observed bands being related to the same organic framework.Electrochemistry Cyclic voltammograms in CH2Cl2 have already been reported for 4b and 4c.8,9 Analogously, 4a is characterized under the same experimental conditions by two reversible monoelectronic reductions (E1/2 1 = 10.05 and E1/2 2 = 20.31 V vs. Ag/AgCl in 3.5 M KCl) and a two electron oxidation. This process is more reversible than in the case of 4b and 4c and in this case the cathodic peak is visible and well defined (Epa 3 = 10.88 V, DE = 0.26, scan rate = 100 mV s21). The cyclic voltammetric curves of 4a and 4b are shown in Fig. 5. It should be noted that the reduction potentials of the Pd derivative are higher than those of the Ni complex, while the oxidation anodic peak occurs at about the same potential. On the basis of previous observations the reduction processes can be assigned to the formation of the two anionic forms of the dithiolene 4a, namely [Pd(Et2timdt)2]2 and [Pd(Et2timdt)2]22, while the oxidation process is probably related to the oxidation of the ligand, as previously pointed out for 4c for which a mixed-valence compound containing the oxidized [Ni(Pri 2timdt)2I2] unit was identified by X-ray crystal structure determination.9 DFT calculations, indicating that the metal contributes to the LUMO through its ndxz orbital and to the HOMO only through its virtual (n 1 1)pz orbitals, account for the almost identical oxidation potentials and for the shifts in the reduction processes for 4a and 4b.It is interesting to compare the redox properties of this new class of complexes with those of the dithiolenes deriving from the dmit ligand (dmit = 4,5-dimercapto-1,3-dithiole-2- thionate, C3S5 22) 40 in which two sulfur atoms are present instead of the NR1 groups. In the case of the nickel derivative the reduction in MeCN from the neutral to the monoanionic form is irreversible and is observed at a value of 10.22 V vs.Ag/AgCl, determined by diVerential pulse polarography, extrapolating to a scan rate of 0 mV s21.41 The reduction to the bianionic form is reversible (E1/2 = 20.13 V vs. Ag/AgCl),41 and the diVerence in the potential between the two processes is almost the same as observed for 4b. These features account for the diVerent stabilities of the neutral forms of [M(R1 2timdt)2] and [M(dmit)2]. The cyclic voltammogram of [Pd(dmit)2]2 dithiolene in MeCN is similar to that of the Ni analogue, with the anodic peaks merging into a single broader peak.42 No oxidation process to a cationic form is observed in the Ni and Pd dmit derivatives 40 whereas an irreversible oxidation similar to Fig. 5 Cyclic voltammetric response recorded at a platinum electrode on an anhydrous CH2Cl2 solution of complexes 4a (1) and 4b (——) (reference Ag/AgCl in 3.5 M KCl; supporting electrolyte NBun 4BF4; scan rate 0.100 V s21).3736 J. Chem. Soc., Dalton Trans., 1998, 3731–3736 that observed in 4a, 4b and 4c was previously found for other dithiolenes, such as [Ni(ddds)2] (ddds = 5,6-dihydro-1,4-dithiin- 2,3-diselenolate, C4H4S2Se2) and [Ni(dddt)2] (dddt = 5,6- dihydro-1,4-dithiin-2,3-dithiolate, C4H4S4), Epa = 10.71 and 10.99 V respectively vs.Ag/AgCl in PhCN.43 Conclusions In view of obtaining new materials for Q-switching laser applications, spectrochemically stable molecules having an intense absorption near to the laser excitation energy are needed.5 The new class of dithiolenes [M(R1 2timdt)2] is therefore very promising, respecting those requirements.With respect to the previously reported Ni-dithiolenes,8 the new [Pd(Et2timdt)2] complex (4a) shows a slight shift of the p–p* transition towards lower energy. Therefore the position of the NIR band of this compound (1010 nm, e = 70000 dm3 mol21 cm21) makes it more suitable for applications with the Nd-YAG laser (1064 nm). As previously pointed out, this type of dithiolenes might be also interesting conducting materials if mixed-valence compounds would be synthesized.Therefore we have attempted the reaction of 4a with I2, but so far only the 1 : 1 adduct 6 has been structurally characterized. Both in the crystal structure of 4a and 6, the dithiolene units are stacked in a tilted orientation with each palladium ion almost ‘sandwiched’ between two planar imidazolidine rings of the parallel adjacent molecules. In the adduct structure each Pd dithiolene molecule interacts with a diiodine molecule through the thioketonic sulfur of one side, the corresponding sulfur of the other ring being involved only in a soft interaction with the iodine of another adduct.The spectroscopic properties of 4a and of its Ni analogue 4b are very similar, as proved by UV–VIS–NIR (both in the solid state and in solution), FTIR, FT-Raman and CP MAS 13C NMR spectroscopies. Electrochemical measurements demonstrate that for 4a oxidation over the neutral state is achievable and quasireversible, diVerentiating it both from the Ni analogue 4b, where this oxidation is irreversible and from [Ni(dmit)2] 40 in which no oxidation process is detected.References 1 J. R. Ferraro and J. M. Williams, Introduction to Synthetic Electrical Conductors, Academic Press, New York, 1987; T. Nakamura, A. E. Underhill, A. T. Coomber, R. H. Friend, H. Tajima, A. Kobayashi and H. Kobayashi, Inorg. Chem., 1995, 34, 870. 2 J.A. McCleverty, Prog. Inorg. Chem., 1968, 10, 49; A. Sato, H. Kobayashi, T. Naito, F. Sakai and A. Kobayashi, Inorg. Chem., 1997, 36, 5262; A. E. Pullen, S. Zeltner, R. M. Olk, E. Hoyer, K. A. Abboud and J. R. Reynolds, Inorg. Chem., 1997, 36, 4163 and refs. therein. 3 U. T. Mueller-WesterhoV, B. Vance and D. I. Yoon, Tetrahedron, 1991, 47, 909; M. Bousseau, L. Valade, J. P. Legros, P. Cassoux, M. Garbauskas and L. V. Interrante, J. Am. Chem. Soc., 1986, 108, 1908; A. Kobayashi, H. Kim, Y.Sasaki, K. Murata, R. Kato and H. Kobayashi, J. Chem. Soc., Faraday Trans., 1990, 86, 361. 4 R. Williams, E. Billig, J. H. Waters and H. B. Gray, J. Am. Chem. Soc., 1966, 88, 43. 5 U. T. Mueller-WesterhoV and B. Vance, Comp. Coord. Chem., 1987, 2, 595; D. I. Yoon, PhD Thesis, University of Connecticut, 1988. 6 K. W. Browall and L. V. Interrante, J. Coord. Chem., 1973, 3, 27. 7 G. N. Schrauzer and V. P. Mayweg, J. Am. Chem. Soc, 1965, 87, 3585. 8 F. Bigoli, P. Deplano, F.A. Devillanova, V. Lippolis, P. J. Lukes, M. L. Mercuri, M. A. Pellinghelli and E. F. Trogu, J. Chem. Soc., Chem. Commun., 1995, 371. 9 F. Bigoli, P. Deplano, F. A. Devillanova, J. R. Ferraro, V. Lippolis, P. J. Lukes, M. L. Mercuri, M. A. Pellinghelli and E. F. Trogu, Inorg. Chem., 1997, 36, 1218. 10 K. H. Drexage and U. T. Mueller-WesterhoV, IEEE J. Quantum Electron, 1972, QE-8, 759; US Pat., 3 743 964, 1973; P. N. Prasad and D. J. Williams, Introduction to Non-linear Optical Effects in Molecules and Polymers, Wiley, New York, 1991, p. 222. 11 J. Labanowsky and J. Andzelm, Density Functional Methods in Chemistry, Springer-Verlag, New York, 1991. 12 T. Ziegler, Chem. Rev., 1991, 91, 651 and refs. therein. 13 A. C. Scheiner, J. Baker and J. W. Andzelm, J. Comput. Chem., 1997, 18, 775. 14 A. D. Becke, J. Chem. Phys., 1993, 98, 1372; 5648. 15 C. Lee, W. Yang and R. G. Parr, Phys. Rev. B, 1988, 37, 785. 16 Gaussian 94 (Revision D.1 & E.1), M. J.Frisch, G. W. Trucks, H. B. Schlegel, P. M. W. Gill, B. G. Johnson, M. A. Robb, J. R. Cheeseman, T. A. Keith, G. A. Petersson, J. A. Montgomery, K. Raghavachari, M. A. Al-Laham, V. G. Zakrzewski, J. V. Ortiz, J. B. Foresman, C. Y. Peng, P. Y. Ayala, M. W. Wong, J. L. Andres, E. S. Replogle, R. Gomperts, R. L. Martin, D. J. Fox, J. S. Binkley, D. J. Defrees, J. Baker, J. P. Stewart, M. Head-Gordon, C. Gonzalez and J. A. Pople, Gaussian, Inc., Pittsburgh PA, 1995. 17 A. Schafer, H.Horn and R. Ahlrichs, J. Chem. Phys., 1992, 97, 2571. 18 P. J. StoVel, J. Org. Chem., 1964, 29, 2794. 19 A. C. North, D. C. Phillips and F. S. Mathews, Acta Crystallogr., Sect. A, 1968, 24, 351. 20 D. T. Cromer and J. T. Waber, International Tables for X-Ray Crystallography, The Kynoch Press, Birmingham, 1974, vol. IV, Table 2.2B. 21 D. T. Cromer, International Tables for X-Ray Crystallography, The Kynoch Press, Birmingham, 1974, vol. IV, Table 2.3.1. 22 B. Frenz, Comp.Phys., 1988, 2, 42; Crystallographic Computing, Oxford University Press, 1991, p. 126. 23 H. W. Roesky, H. Hofman, W. Clegg, M. Noltemeyer and G. M. Sheldrick, Inorg. Chem., 1982, 21, 3798. 24 R. Isaksson, T. Liljefors and J. Sandstrom, J. Chem. Res. (S ), 1981, 43. 25 P. J. StoVel, J. Org. Chem., 1964, 29, 2794. 26 S. Sheibe, B. J. Pedersen and S.-O. Lawesson, Bull. Soc. Chim. Belg., 1978, 87, 229. 27 F. Bigoli, M. A. Pellinghelli, D. Atzei, P. Deplano and E. F. Trogu, Phosphorus Sulfur, 1987, 37, 189. 28 M. Arca, A. Cornia, F. A. Devillanova, A. C. Fabretti, F. Isaia, V. Lippolis and G. Verani, Inorg. Chim. Acta, 1997, 262, 81. 29 S. Alvarez, R. Vicente and R. HoVmann, J. Am. Chem. Soc., 1985, 107, 6253. 30 K. W. Browall and L. V. Interrante, J. Coord. Chem., 1973, 3, 27. 31 K. W. Browall, L. V. Interrante and J. S. Kasper, Inorg. Chem., 1972, 11, 1800. 32 P. Deplano, F. A. Devillanova, J. R. Ferraro, F. Isaia, V. Lippolis and M. L. Mercuri, Appl. Spectrosc., 1992, 46, 1625 and refs. therein. 33 S. I. Shupack, I. Billig, R. J. H. Clark, R. Williams and H. B. Gray, J. Am. Chem. Soc., 1964, 86, 4594. 34 Z. S. Herman, R. F. Kirchner, G. H. Loew, U. T. Mueller- WesterhoV, A. Nazzal and M. C. Zerner, Inorg. Chem., 1982, 21, 46. 35 C. Adamo and F. Lelj, J. Chem. Phys., 1995, 103, 10605; F. Lelj, C. Adamo and V. Barone, Chem. Phys. Lett., 1994, 230, 189. 36 C. Daul, Int. J. Quantum Chem., 1994, 52, 867. 37 I. Fischer-Hjalmars and A. Henriksson-Enflo, Int. J. Quantum. Chem., 1980, 18, 409; D. Demoulin, I. Fischer-Hjalmars, A. Henriksson Enflo, J. A. Pappas and M. Sandbom, Int. J. Quantum. Chem., 1977, 12 (Suppl. 1), 351. 38 J. A. Pople, D. Beveridge and P. Dobosh, J. Chem. Phys., 1967, 47, 2026. 39 R. J. H. Clark and P. C. Turtle, J. Chem. Soc., Dalton Trans., 1977, 2142. 40 G. Steimecke, H. J. Sieler, R. Kirmse and E. Hoyer, Phosphorus Sulfur, 1979, 7, 49. 41 R. Kato, H. Kobayashi, A. Kobayashi and Y. Sasaki, Bull. Chem. Soc. Jpn., 1986, 59, 627. 42 B. Pomarède, B. Garreau, I. Malfant, L. Valade, P. Cassoux, J. P. Legros, A. Audouard, L. Brossard, J. P. Ulmet, M. L. Doublet and E. Canadell, Inorg. Chem., 1994, 33, 3401. 43 H. Fujiwara, E. Arai and H. Kobayashi, Chem. Commun., 1997, 837. Paper 8/05494K

ISSN:1477-9226    

DOI:10.1039/a805494k

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, 3737–3743 3737 New functionalized bis(pyrazol-1-yl)methane ligands. Synthesis, spectroscopic characterization of early and late transition metal complexes containing a functionalized N,N or P,P-chelate bis(5- diphenylphosphinopyrazol-1-yl)methane ligand Antonio Antiñolo, Fernando Carrillo-Hermosilla, Enrique Díez-Barra, Juan Fernández-Baeza, Maria Fernández-López, Agustin Lara-Sánchez, Andrés Moreno, Antonio Otero,* Ana Maria Rodriguez and Juan Tejeda Departamento de Química Inorgánica, Orgánica y Bioquímica, Facultad de Ciencias Químicas, Universidad de Castilla-La Mancha, Campus Universitario, 13071-Cuidad Real, Spain Received 21st July 1998, Accepted 15th September 1998 The multistep syntheses of the novel functionalized bis(pyrazol-1-yl)methane ligands, bis(5-diphenylphosphinopyrazol- 1-yl)methane (bppzm) 1, bis(5-diphenylphosphinopyrazol-1-yl)trimethylsilylmethane (bppztm) 2 and bis- (2-diphenylphosphinoimidazol-1-yl)methane (bpizm) 3, have been studied.The coordinative capacity of the bppzm ligand towards a variety of early and late metal fragments was evaluated and seven metallacycles were isolated. The complex [{NbCl3(dme)}n] (dme = 1,2-dimethoxyethane) reacted with an excess of bppzm to give the binuclear complex [{NbCl3(bppzm)}2] 4, and in the same way the reaction of the mononuclear species [NbCl3(dme)(RC]] ] CR9)] with 1 gave the appropriate [NbCl3(bppzm)(RC]] ] CR9)] complexes (R = R9 = Ph 5; R = R9 = SiMe3 6; R = Ph, R9 = Me 7; R = Ph, R9 = SiMe3 8).In all these niobium complexes, 1 behaves as an N,N chelate ligand. Compound 1 reacts with [MCl2(PhCN)2] (M = Pd, Pt) to yield the complexes [MCl2(bppzm)] (M = Pd 9, Pt 10), where a P,P chelate behaviour for 1 was observed. A dynamic conformation of the six- and eight-membered metallacycles formed in the complexes was observed and variable-temperature NMR studies were carried out. Finally, the molecular structure of complex 10 was determined crystallographically and a distorted square-planar geometry was found in which a proton (Hendo) of the bridging methylene is in close proximity to the metal centre in the boat–boat conformation of the metallacycle.Introduction The use of polyfunctional ligands has increasingly attracted attention in the field of coordination chemistry because it has often been shown that in complexes based on such ligands the functional group(s) may be helpful for controlling or enhancing the reactivity of the metal centre.1 Several studies on phosphines with functional group substituents have been carried out in the field of transition metal chemistry 2 since bidentate biphosphine compounds in particular are excellent ligands in coordination and organometallic chemistry.3 Furthermore, the polydentate N-donors poly(pyrazol-1-yl)alkanes 4 are interesting ligands because they are easily modified so as to modulate electronic and steric eVects, and they also exhibit interesting conformational and fluxional behaviour that is not possible for planar ligands. With these precedents in mind we have previously explored the preparation of several families of poly(pyrazol-1-yl)methane-containing complexes of early (Nb5) and late (Ru6 and Pd7) transition metals.We are now interested in the preparation of new poly(pyrazol-1-yl)methanes containing phosphine groups on the pyrazole rings in order to test their coordinate potential, N,N versus P,P coordination modes towards diVerent early and late metal centres.The aim of this report is to present a synthetic route to new functionalized bis(pyrazol-1-yl)methanes as well as the preparation and spectroscopic characterization of complexes of niobium, palladium and platinum with bis(5-diphenylphosphinopyrazol- 1-yl)methane. Results and discussion The syntheses of the new ligands are outlined in Scheme 1. The diVerent steps involve classic methodologies for the preparation of the intermediates leading to the diVerent polyfunctionalized diphosphine ligands.Specific reference to the methods applied, along with a detailed synthetic procedure for each intermediate, is reported in the Experimental section. The compounds were isolated as air-stable colourless solids in good yields (see Experimental section) and were spectroscopically characterized. The 1H NMR spectra of 1 and 2 show two doublets assigned to H3 and H4, with the more shielded signal corresponding to H4.The signals that correspond to both CH2 and CH groups in 1 and 2, respectively, appear as triplets due to coupling with the two phosphorus atoms. Homonuclear NOE Scheme 1 Summary of reactions leading to the preparation of compounds 1–3. Reagents and conditions: (i) 2 BunLi, thf, 270 8C, 30 min; (ii) 2 Ph2PCl, thf, r.t., 12 h; (iii) BunLi, thf, 270 8C, 1 h; (iv) Me3SiCl, thf, r.t., 12 h. N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N N Ph2P 1 PPh2 CH2 Li 2 3 4 Li 4 5 CH2 1 2 5 3 CH2 PPh2 CH Ph2P SiMe3 PPh2 1 Ph2P 2 4 5 5 CH2 Li CH2 PPh2 Ph2P CH 1, bppzm Ph2P 2, bppztm PPh2 CH2 3 4 3 2 1 3, bpizm Li Li CH2 " " " " " " ( iii) ( i) ( ii) ( iv) ( i) ( ii)3738 J.Chem. Soc., Dalton Trans., 1998, 3737–3743 (nuclear Overhauser enhancement) diVerence spectroscopy was also applied to compound 2 in order to confirm the assignment of the signal for the CH group.Irradiation of the SiMe3 signal produces an enhancement of the signal at d 7.06 which corresponds to the CH group. The 13C{1H} NMR spectra exhibit only one signal each for C3, C4 and C5 as would be expected for the two equivalent pyrazol-1-yl groups in the molecule. The C5 signal was assigned in the corresponding 13C NMR spectra and the resonances of the C3 and C4 carbon atoms by means of two-dimensional heteronuclear chemical shift correlation (HETCOR) experiments. In addition, at higher field values a triplet due to coupling with the two phosphorus atoms was observed for the methylene carbon atoms in 1.The 13C NMR spectra also confirm the presence of the methinic carbon of compound 2. The aromatic carbon atoms were assigned on the basis of the values of JPC coupling constants. In compound 2 two resonances were observed due to the aromatic carbons, indicating that the two phenyl rings are non-equivalent. This could be due to the substantial steric hindrance present.The 31P{1H} NMR spectra show a singlet for the two phosphorus atoms at d 231.37 for 1 and d 237.85 for 2, indicating that both phosphorus atoms are equivalent. The 1H NMR spectrum of 3 exhibits two doublets for H4 and H5, which were assigned through an NOE experiment, and a triplet is also observed for the CH2 group due to coupling with the two phosphorus atoms. The 13C{1H} NMR spectrum also exhibits one signal each for C2, C4 and C5, which were assigned by both the 13C NMR spectrum and an 1H–13C heteronuclear correlation (HETCOR) experiment.Finally, the 31P{1H} NMR spectrum exhibits a singlet at d 234.51 for both equivalent phosphorus atoms. Compound 1 was used in the complexation of some metal fragments in order to test its coordinative capacity as a chelating agent. First, we considered its reactivity towards some niobium-containing complexes, namely [{NbCl3(dme)}n] (dme = 1,2-dimethoxyethane) and [NbCl3(dme)(RC]] ] CR9)].Compound 1 reacts at room temperature with a slight excess of a THF suspension of [{NbCl3(dme)}n] [eqn. (1)] to give, l/n[NbCl3(dme)]n 1 bppzm 1/2[NbCl3(bppzm)]2 1 dme (1) 4 after stirring for 20 h, a suspension from which the complex [{NbCl3(bppzm)}2] 4 [bppzm = bis(5-diphenylphosphinopyrazol- 1-yl)methane] was isolated as a deep brown solid after the appropriate work-up. The diVerent THF solutions of the [NbCl3(dme)(RC]] ] CR9)] species also react with 1 at room temperature, in an 1 : 1 molar ratio [eqn.(2)], to aVord orange, NbCl3(dme)(RCCR9) 1 bppzm NbCl3(bppzm)(RCCR9) 1 dme (2) R = R9 = Ph 5 R = R9 = SiMe3 6 R = Ph, R9 = Me 7 R = Ph, R9 = SiMe3 8 blue and brown solutions from which air-sensitive solid samples of the complexes [NbCl3(bppzm)(RC]] ] CR9)] (R = R9 = Ph 5; R = R9 = SiMe3 6; R = Ph, R9 = Me 7; R = Ph, R9 = SiMe3 8), were isolated after the appropriate work-up (see Experimental section). The diVerent complexes were characterized spectroscopically. The mass spectrum of 4 indicates a binuclear formulation and its IR spectrum shows a strong band at 320 cm21, which has been assigned to the n(Nb–Cl) terminal group for a D2h binuclear disposition with the terminal chloride ligands trans in an octahedral environment for each niobium atom (see Fig. 1).This is the structural geometry that has been described 5,8 as the most propitious in analogous binuclear complexes with terminal and bridging halide ligands.NMR spectroscopy has proved a useful tool for the characterization of the diVerent bppzm-containing niobium complexes. The 1H NMR spectrum of 4 shows a set of resonances for H3, H4 and CH2 indicating that both pyrazole rings are equivalent. In the same way, the 13C{1H} NMR spectrum exhibits the corresponding signals for C3, C4, C5 and CH2, and all the resonances are shifted to lower field in comparison with the free ligand (see Experimental section). An especially interesting result concerns the 31P{1H} NMR spectrum, where a singlet for the two equivalent phosphorus atoms appears at d 234.19.This value is close to the value of d 231.37 found in the free ligand, indicating that a quaternization of both phosphorus atoms by a possible coordination to the niobium centres does not take place and hence that the ligand behaves in this complex as an N,N-donor ligand (Fig. 1). The IR spectra of the alkynecontaining complexes 5–8 show a characteristic band located between 1690 and 1710 cm21, which corresponds to the n(C]] ] C) mode of the bound alkynes.The 1H NMR spectra of these complexes exhibit two resonances for the H3 and H4 pyrazole protons, which appear as doublets of doublets indicating that the two pyrazole rings from the bppzm ligand are nonequivalent. The assignment of the H3 and H4 signals for each pyrazole ring was carried out by means of the appropriate selective decoupling (INDOR) experiments. These results agree with a proposed octahedral structural disposition where the two pyrazole rings are located in cis and trans positions with respect to the alkyne ligand (Fig. 2). NOE experiments were carried out in order to confirm this proposed structure. For example, the irradiation in complex 6 of the SiMe3 alkyne group enhances only one of the H3 signals, clearly that of the cis pyrazole ring which has a closer spatial proximity to the alkyne ligand. In addition, the 13C{1H} NMR spectra of complexes 5–8 exhibit two resonances for the diVerent pyrazole carbon atoms, C3, C4, C5 and their assignments were carried out through the 1H–13C HMQC correlation experiments. The 31P{1H} NMR spectra show two signals, which correspond to an AB spin system for the two non-equivalent phosphorus atoms, with JAB values between 33.6 and 35.7 Hz (see Experimental section), in accordance with the proposed structural geometry (Fig. 2). The chemical shifts are close to the values for the free ligand, indicating that, as was the case for complex 4, a quaternization of both phosphorus atoms by coordination on the metal centre does not take place. 1H–31P HMQC correlation experiments have allowed the assignment of the phosphorus resonances that correspond to each pyrazole ring.In the 1H and 1H{31P} NMR spectra of 5–8 recorded at room temperature, the CH2 resonance appears as a triplet or singlet respectively, indicating that a dynamic behaviour in solution takes place involving a boat-to-boat inversion in the six-membered Fig. 1 Proposed structure for complex 4.N N Nb Cl Cl Cl C N N H H Ph2P Ph2P N N Nb Cl Cl Cl C N N H H PPh2 PPh2 Fig. 2 Proposed structure for complexes 5–8. N N H4' H3' Nb C Ph2P' N N H4 H3 Ph2P H H Cl Cl Cl R' RJ. Chem. Soc., Dalton Trans., 1998, 3737–3743 3739 metallacycle (Scheme 2). A mechanism for this has been proposed for several complexes containing poly(pyrazol-1-yl)- alkane ligands.4 In order to elucidate the dynamic behaviour of complexes 5–8 in solution, and to obtain NMR parameters for the static structure at the slow-exchange limit, variabletemperature NMR studies were carried out.In the diVerent examples the presence of the PPh2 moieties in the pyrazole rings creates steric hindrance that makes the boat-to-boat inversion more diYcult and hence a static structure at moderately low temperature values was found. Complexes 5 and 6 (with symmetrical alkynes) and 7 and 8 (with unsymmetrical alkynes) will be discussed separately.In the case of complex 5, when the temperature was lowered to 203 K two doublets corresponding to the AB system (JAB = 7.6 Hz) of the CH2 group was observed in the 1H{31P} NMR spectrum; however, in the 1H NMR spectrum two triplets from an ABXX9 system, JAX = JBX9 = 7.8 Hz; JAX9 = JBX = 0 Hz, where each proton is coupled with a phosphorus atom, was observed. Similar behaviour was observed for complex 6 (JAB = 14.2 Hz) in the 1H{31P} NMR spectrum at 213 K, but in the 1H NMR spectrum an ABXX9 system, JAx = JAx9 = 4.7 Hz; JBX = JBX9 = 0 Hz, where only one proton is coupled to both phosphorus atoms was observed, giving rise to two triplets (relative intensities 2 : 1) for HA and two singlets (relative intensities 2 : 1) for HB.The coalescence temperatures were 258 and 265 K, respectively, for 5 and 6. From these studies free activation energy values, DG‡, of 12.82 and 13.12 kcal mol21 for 5 and 6, respectively, were calculated (1 cal = 4.184 J).9 The results agree with the presence of the aforementioned boat-to-boat inversion in the six-membered metallacycle. At low temperature the process can be frozen, giving rise to two enantiomers, which are represented in Scheme 3.These two enantiomers cannot be distinguished by means of NMR spectroscopy. As yet we do not have any conclusive explanation as to why the ABXX9 systems of both complexes are diVerent, although we believe that a possible torsion of the boat could be responsible for the diVerent couplings in 6 of HA and HB with the two phosphorus atoms.Modelling studies in order to clarify this point are in progress. In the case of complex 7, when the temperature was lowered to 193 K two AB systems (JAB = 7.1 and 14.1 Hz) for the CH2 group were observed in the 1H{31P} NMR spectrum, but two diVerent ABXX9 systems, JAX = JBX9 = 7.8 Hz; JAX9 = JBX = 0 Hz and JAX = JAX9 = 5.1 Hz; JBX = JBX9 = 0 Hz, were found in the 1H NMR spectrum.Similar behaviour was found in the variable-temperature NMR study for 8 (at 230 K JAB = 6.6 and 14.3 Hz; JAX = JBX9 = 7.8 Hz; JAX9 = JBX = 0 Hz and JAX = JAX9 = 4.8 Hz; JBX = JBX9 = 0 Hz). The coalescence temperatures were 243 K (DG‡ = 11.91 kcal mol21) and 253 K (DG‡ = 12.55 kcal mol21), respectively. Computer simulation studies of the all spin systems described were also carried out, and the spectra obtained agree very well with the corresponding experimental spectra.The next question Scheme 2 Boat-to-boat inversion. N N N N N N N N C C H HA B H HB A M M Scheme 3 Proposed structures for the two enantiomers of complexes 5 and 6. N N N N N N N N Ph2P Ph2P Ph2P Ph2P Nb C H HB A Nb C H HA B Cl Cl Cl Cl Cl Cl R R R R that must be considered is, how can we explain the presence of two spin systems for the CH2 group when the temperature is lowered? As discussed for complexes 5 and 6, at low temperature the boat-to-boat inversion can be frozen in and now, as a consequence of the presence of unsymmetrical alkyne ligand, four stereoisomers, i.e.those with the most stable acetylene, are present in solution (Scheme 4) and there are two diastereoisomers that give rise to a diVerent response in the NMR spectra and are responsible for the two spin systems. We have confirmed the presence at low temperature of the proposed four stereoisomers by means of an experiment carried out on complex 7.The addition of a chiral shift reagent, namely (R)- (2)-(9-anthryl)-2,2,2-trifluoroethanol, to a solution of 7 gives rise to the appearance in the 1H{31P} NMR spectrum at 193 K of four AB spin systems that correspond to the four diastereoisomers from the corresponding four stereoisomers. The 13C NMR resonances for the carbon atoms of the alkyne ligands appear at d ca. 250, indicating that the alkyne ligand behaves as a four-electron donor (see Experimental section). An empirical correlation between the alkyne p donation and 13C chemical shift for the bound alkyne carbons has been observed.10 The NMR spectroscopic data of complexes 5–8 indicate that the alkyne ligand is fluxional, as was previously observed for other alkyne-containing niobium complexes.5 In order to study this behaviour, variable-temperature 1H-NMR studies were carried out for these complexes.We assume that a six-coordinate description of the complexes (see Fig. 2) in which the alkyne occupies a single site is preferable to the alternative seven-coordinate model in which each alkyne carbon is considered to occupy a separate coordination position.Based on this assumption we propose a simple rotation of the alkyne ligand around the bisector of the metal–alkyne isosceles triangle to explain the observed fluxional behaviour. Several examples have been described, mainly for d4 alkyne complexes of MoII or WII, where a fluxional behaviour by rotation of the alkyne ligand has been considered.10 From these studies free energy values, DG‡, of 9.72, 10.04 and 9.15 kcal mol21 for 5, 6 and 8, respectively, were calculated 9 at the respective coalescence temperatures of 198, 210 and 193 K.It was not possible to calculate DG‡ for complex 7, in which the coalescence temperature was 178 K. The values allow us to establish a relationship between the steric demand of the alkyne and the rotation phenomenon. In fact, it can be seen that the higher DG‡ and coalescence temperature values were found in the cases of the bulkier alkyne substituents.On the basis of these data we propose that steric eVects may be implicated in the fluxional behaviour of the alkyne ligand in this class of complex. A good example of this behaviour is provided by the variable- Scheme 4 Proposed structures for the four stereoisomers of complexes 7 and 8.3740 J. Chem. Soc., Dalton Trans., 1998, 3737–3743 temperature NMR study of 6.In Fig. 3 we can observe that in the variable-temperature 1H NMR spectrum, when the temperature was lowered to below 168 K, distinct chemical shifts were observed for the SiMe3 alkyne groups. In the complexes containing unsymmetrical acetylenes (7 and 8) two signals are observed for each of the substituents of the alkyne. This con- firms the point discussed above in that there are four stereoisomers and two diastereoisomers present (Scheme 4). Finally, we investigated the behaviour of the bppzm ligand towards late-metal centres, namely [MCl2(PhCN)2] (M = Pd, Pt).A solution of [MCl2(PhCN)2] in CH2Cl2 reacted with the bppzm ligand (in a 1 : 1 molar ratio) at room temperature to give, after 5 h of stirring, a solution from which the new compounds [MCl2(bppzm)] (M = Pd 9, Pt 10), were isolated after the appropriate work-up [eqn. (3)]. The complexes were isolated MCl2(PhCN)2 1 bppzm MCl2(bppzm) 1 2PhCN (3) M = Pd 9, Pt 10 as crystalline air-stable solids in good yields (see Experimental section) and were characterized spectroscopically.The H4 resonance in the 1H NMR spectrum appears only as doublet of doublets due to coupling with H3 and P atoms in complex 9, whereas a broad signal is observed for the corresponding proton in complex 10, and H3 exhibits one resonance as a doublet due to coupling with H4 in complex 9 and a broad signal in complex 10. These results indicate that both pyrazole rings of the bppzm are equivalent in both complexes.In addition, a broad signal, which corresponds to an unresolved triplet due to coupling with the phosphorus atoms, is observed in the spectrum of both complexes for the CH2 group, indicating that a fluxional behaviour in solution of the eightmembered metallacycle occurs (see below). The 13C{1H} NMR spectra exhibit the signal for the methylene carbon atom as a triplet in 9, due to coupling with the two phosphorus atoms (JPC = 3.5 Hz), and as a singlet in 10.In addition, two triplets and multiplets (probably due to the fact that the chemical shifts are close) are observed for C3 and C4 in 10 and 9, respectively. The 31P{1H} NMR spectra show signals at d 4.66 for 9 and d 211.30 for 10, indicating that both phosphine atoms are equivalent. It is noteworthy that both resonances appear at significantly lower fields than the corresponding signals in the free ligand and this behaviour is in contrast to that previously found in the niobium complexes described above, suggesting that in complexes 9 and 10 a coordination of the ligand through the phosphorus atoms takes place.Based on a square-planar geometry (see Fig. 4) the IR spectroscopic data allow us to propose a cis-geometry (C2v) because two bands at ca. 330 and 300 cm21, which correspond to the n(M–Cl) (M = Pd, Pt) are present.11 The dynamic behaviour in solution of complexes 9 and 10, involving a boat-to-boat inversion of the eight-membered metallacycle in a similar way to that shown Fig. 3 Variable-temperature 1H NMR spectra in the region of the SiMe3 alkyne groups of the complex [NbCl3(bppzm)(Me3SiC]] ] CSiMe3)] 6. in Scheme 2 for the six-membered metallacycle niobium complexes, was studied by means of variable-temperature NMR. From these studies we calculated the free activation energy values, DG‡ of 10.82 and 10.12 kcal mol21 for 9 and 10, respectively, at the respective coalescence temperatures, 233 and 223 K. This behaviour contrasts with that observed in several MCl2– diphosphine metallacycles (M = Pd, Pt) containing a bidentate phosphorus ligand, where a rigid boat–boat conformation in solution is found.12 In order to confirm the proposed structure for 9 and 10 we have carried out a crystal structure analysis of complex 10.A perspective view of the complex is shown in Fig. 5, and bond lengths and angles are listed in Table 1. The platinum complex exhibits a distorted square planar geometry.The distortion is reflected by the tetrahedral displacements of the following atoms from the mean coordination plane: Cl(2), 20.133(2); Cl(3), 0.123(2); P(4), 20.089(2) and P(5), 0.089(2) Å. The chelating behaviour of the bppzm ligand results in an eight-membered chelation ring, which presents a distorted boat–boat conformation as shown in Fig. 6. The torsion angles are C(3)–N(6)–C(4)–N(8) and P(4)–Pt(1)– P(5)–C(7) of 111.9(8) and 90.5(3)8, which should be equal to zero in a non-distorted boat–boat conformation.The conformation of the metallacycle is such that H4B, the Hendo hydrogen atom of the methylene group, is oriented almost perpendicular to the coordination plane [P(1) ? ? ? H4B, 2.750(1) Å], and the angle between the Pt(1) ? ? ? H4B and the normal to the plane is 27.98. Fig. 4 Proposed structures for complexes 9 and 10. N N H4 H3 Ph2P N N H4 H3 PPh2 H2 C Cl M Cl Fig. 5 ORTEP drawing of complex 10. Table 1 Selected bond lengths (Å) and angles (8) for 10 Pt(1)–P(4) Pt(1)–P(5) Pt(1)–Cl(2) Pt(1)–Cl(3) P(4)–C(3) P(5)–C(7) N(6)–N(7) N(6)–C(3) N(6)–C(4) P(4)–Pt(1)–P(5) P(4)–Pt(1)–Cl(2) P(5)–Pt(1)–Cl(2) P(4)–Pt(1)–Cl(3) P(5)–Pt(1)–Cl(3) 2.252(2) 2.269(5) 2.332(2) 2.337(5) 1.811(7) 1.795(7) 1.343(8) 1.365(9) 1.465(9) 98.85(10) 170.84(7) 88.82(10) 86.66(10) 172.39(7) N(7)–C(1) N(8)–C(7) N(8)–N(9) N(8)–C(4) N(9)–C(5) C(1)–C(2) C(2)–C(3) C(5)–C(6) C(6)–C(7) Cl(2)–Pt(1)–Cl(3) C(3)–P(4)–Pt(1) C(7)–P(5)–Pt(1) N(8)–C(4)–N(6) 1.336(11) 1.355(9) 1.377(8) 1.432(9) 1.330(11) 1.364(12) 1.376(9) 1.401(13) 1.372(10) 86.19(10) 113.4(2) 112.9(2) 111.8(5)J. Chem.Soc., Dalton Trans., 1998, 3737–3743 3741 In conclusion, the preparation of new functionalized phosphorus-containing bis(pyrazol-1-yl)methane compounds has been carried out by means of a simple multistep synthesis. The coordination behaviour of one of the compounds synthesized, bis(5-diphenylphosphinopyrazol-1-yl)methane (bppzm), was considered towards metal centres of niobium, palladium and platinum.In the first case, new binuclear and mononuclear niobium species with an N,N-six-membered metallacycle were isolated. However, for the starting complexes [MCl2(PhCN)2] (M = Pd, Pt), square-planar species with a P,P-eight-membered metallacycle were found. In both classes of complexes a dynamic behaviour in solution, which corresponds to a boat-to-boat inversion of the corresponding metallacycle, was considered to be present by variable-temperature NMR studies.Experimental All reactions were performed using standard Schlenk-tube techniques under an atmosphere of dry nitrogen. Solvents were distilled from appropriate drying agents and degassed before use. Microanalyses were carried out with a Perkin-Elmer 2400 CHN analyzer. Mass spectra were recorded on a VG Autospec instrument using the FAB technique and nitrobenzyl alcohol as matrix. Infrared spectra were obtained in the region 4000–200 cm21, using a Perkin-Elmer 883 spectrophotometer. 1H, 13C and 31P NMR spectra were recorded on a Varian Unity FT-300 spectrometer and referenced to the residual deuterated solvent. The NOE diVerence spectra were recorded with the following acquisition parameters: spectra width 5000 Hz, acquisition time 3.27 s, pulse width 908, relaxation delay 4 s, irradiation power 5–10 dB, number of scans 120. Two-dimensional NMR and simulated spectra were acquired using standard VARIAN-FT software, and processed using an IPC-Sun computer.The NMR probe temperatures were varied using an Oxford Instruments VTC 4 unit, measured by a thermocouple and calibrated with CD3OD. The complexes [{NbCl3(dme)}n], [NbCl3(dme)- (RC]] ] CR9)] and [MCl2(PhCN)2] (M = Pd, Pt) and the compounds bis(pyrazol-1-yl)methane (bpzm) and bis(imidazol- 1-yl)methane (bizm) were prepared as reported previously.13–15 Preparations Bis(5-diphenylphosphinopyrazol-1-yl)methane (bppzm) 1. In a 250 cm3 Schlenk tube, bpzm (3 g, 20 mmol) was dissolved in dry tetrahydrofuran (THF) (150 cm3) and cooled to 270 8C.A 1.6 M solution of BunLi (26.9 cm3, 43 mmol) in hexane was added and the solution was stirred for 30 min. Ph2PCl (7.27 Fig. 6 Drawing showing the conformation of the chelation ring in complex 10. cm3, 41 mmol) was added and the reaction mixture was allowed to slowly reach room temperature. After 12 h the reaction was quenched with NH4Cl (2.16 g, 41 mmol). The suspension was filtered and the solvent removed under vacuum. The orange oil obtained was washed with hexane and the residue was extracted with CH2Cl2.The solvent was removed and the orange oil obtained was washed with EtO. A colourless solid was obtained that was crystallized from CH2Cl2–Et2O. Yield 63% (Found: C, 71.80; H, 5.09; N, 10.53. C31H26N4P2 requires C, 72.08; H, 5.07; N, 10.85%). 1H NMR (CDCl3, 295 K), d 6.59 (t, 2 H, 4JHP = 1.5, CH2), 7.42 (d, 2 H, 3JHH = 1.8, H3), 5.91 (d, 2 H, 3JHH = 1.8 Hz, H4), 7.29–7.17 (m, 20 H, Ph). 13C-{1H} NMR (CDCl3), d 62.27 (t, 3JCP = 10.4, CH2), 140.17 (d, 3JCP = 6.1, C3), 114.54 (d, 2JCP = 10.6, C4), 140.56 (s, C5), 133.35 (d, 2JCP = 10.4, Co), 128.43 (d, 3JCP = 3.6 Hz, Cm), 128.99 (s, Cp), 135.30 (s, Cipso). 31P-{1H} NMR (CDCl3, H3PO4 as reference), d 231.37 (s, PPh2). Bis(5-diphenylphosphinopyrazol-1-yl)trimethylsilylmethane (bppztm) 2. In a 250 cm3 Schlenk tube, bppzm (1 g, 1.94 mmol) was dissolved in dry tetrahydrofuran (THF) (100 ml) and cooled to 279 8C.A 1.6 M solution of BunLi (2.03 cm3, 3.25 mmol) in hexane was added and the solution was stirred for 1 h. SiMe3Cl (0.27 cm3, 2.13 mmol) was added and the reaction mixture was allowed to slowly reach room temperature. After 12 h the reaction was quenched with NH4Cl (104 mg, 1.94 mmol). The suspension was filtered and the solvent removed under vacuum to give a colourless solid. Yield 58% (Found: C, 69.02; H, 5.48; N, 9.87. C34H34N4P2Si requires C, 69.38; H, 5.82; N, 9.51%). 1H NMR (CDCl3, 295 K), d 7.06 (t, 1 H, 4JHP = 5.1, CH), 7.60 (d, 2 H, 3JHH = 1.9, H3), 6.04 (d, 2 H, 3JHH = 2.0 Hz, H4), 0.02 (s, 9 H, SiMe3), 7.39–7.18 (m, 20 H, Ph). 13C-{1H} NMR (CDCl3), d 67.37 (t, 3JCP = 9.8, CH), 139.82 (d, 3JCP = 6.1, C3), 114.06 (d, 2JCP = 10.6, C4), 140.23 (s, C5), 133.96, 132.97 (2d, 2JCP = 10.8, 10.1, Co), 128.49, 128.09 (2d, 3JCP = 3.6, 3.3 Hz, Cm), 129.14, 128.31 (2s, Cp), 136.35, 136.03 (s, Cipso). 31P-{1H} NMR (CDCl3, H3PO4 as reference), d 237.85 (s, PPh2).Bis(2-diphenylphosphinoimidazol-1-yl)methane (bpizm) 3. The synthetic procedure was the same as for complex 1, using bizm (3 g, 20 mmol), BunLi (1.6 M, 26.50 cm3, 43 mmol) and Ph2PCl (7.27 cm3, 41 mmol) to give compound 3 as a colourless solid. Yield 65% (Found: C, 71.97; H, 5.16; N, 10.64. C31H26N4P2 requires C, 72.08; H, 5.07; N, 10.85%). 1H NMR (CDCl3, 295 K), d 6.58 (t, 2 H, 4JHP = 3,3, CH2), 7.17 (d, 2 H, 3JHH = 1.3, H4), 7.05 (d, 2 H, 3JHH = 1.3 Hz, H5), 7.48–7.32 (m, 20 H, Ph). 13C-{1H} NMR (CDCl3), d 55.49 (t, 3JCP = 17.1, CH2), 146.05 (d, 1JCP = 4.5, C2), 132.28 (s, C4), 121.94 (d, 3JCP = 3.0, C5), 133.78 (d, 2JCP = 20.6, Co), 128.66 (d, 3JCP = 4.0, Cm), 129.43 (s, Cp), 133.94 (s, 1JCP = 23.6 Hz, Cipso). 31P-{1H} NMR (CDCl3, H3PO4 as reference), d 234.51 (s, PPh2). [{NbCl3(bppzm)}2] 4. To a THF (50 cm3) suspension of [{NbCl3(dme)}n] (0.250 g, 0.86 mmol) was added an equimolar quantity of bppzm (0.446 g, 0.86 mmol).The suspension was stirred for 20 h at room temperature. The solvent was removed in vacuo and a brown solid was obtained. Yield 77% (Found: C, 52.41; H, 3.37; N, 7.54. C62H52Cl6N8P4Nb2 requires C, 52.02; H, 3.66; N, 7.83%). 1H NMR (CDCl3, 295 K), d 6.60 (s, 4 H, CH2), 7.45 (s, 4 H, H3), 5.85 (s, 4 H, H4), 7.42–7.24 (m, 40 H, Ph). 13C-{1H} NMR (CDCl3), d 61.57 (s, CH2), 134.44 (s, C3), 114.03 (s, C4), 139.52 (s, C5), 134.04–127.87 (m, Ph). 31P-{1H} NMR (CDCl3, H3PO4 as reference), d 234.19 (s, PPh2).IR (Nujol, cm21) 320, 241 [n(Nb–Cl)]. Mass spectrum: m/z 1429 (M 1 1). [NbCl3(bppzm)(PhC]] ] CPh)] 5. The synthetic procedure was the same as for complex 1, using [NbCl3(dme)(PhC]] ] CPh)] (0.250 g, 0.53 mmol) and bppzm (0.280 g, 0.53 mmol), to give complex 5 as an orange solid. Yield 80% (Found: C, 60.18;3742 J. Chem. Soc., Dalton Trans., 1998, 3737–3743 H, 4.22; N, 6.02. C45H36Cl3N4P2Nb requires C, 60.46; H, 4.06; N, 6.27%). 1H NMR (CDCl3, 295 K), d 7.19 (t, 4JHP = 2.7, 2 H, CH2), 8.74 (dd, 3JHH = 2.5, 4JHP = 1.2, 1 H, H3), 7.42 (dd, 1 H, H39), 6.03 (dd, 3JHH = 2.5, 3JHP = 0.6, 1 H, H4), 5.79 (dd, 3JHH = 2.5, 3JHP = 0.7, 1 H, H49), 7.63–7.21 (m, 20 H, PPh2), 7.93 [dd, 3JHo,m = 8.3, 4JHo,p = 0.9 Hz, 4 H, Ho(PhC]] ] )], 7.63–7.21 [m, 6 H, Hm, Hp(PhC]] ] )]. 13C-{1H} NMR (CDCl3), d 58.92 (t, 3JPC = 15.0, CH2), 147.41 (s, C3), 144.42 (s, C39), 114.01 (s, C4), 113.73 (s, C49), 146.69 (dd, 1JPC = 20.0, 5JPC = 3.0, C5), 144.84 (dd, 1JPC = 18.8, 5JPC = 1.7 Hz, C59), 137.84–126.81 (m, Ph), 238.98 (s, C]] ] C). 31P-{1H} NMR (CDCl3, H3PO4 as reference), d 232.65, 232.30 (AB, JAB = 33.6, PPh2, P9Ph2). IR (Nujol, cm21) 1690 [n(C]] ] C)], 393, 323 [n(Nb–Cl)]. [NbCl3(bppzm)(Me3SiC]] ] CSiMe3)] 6. The synthetic procedure was the same as for complex 1, using [NbCl3(dme)- (Me3SiC]] ] CSiMe3)] (0.250 g, 0.54 mmol) and bppzm (0.281 g, 0.54 mmol), to give complex 6 as a blue solid. Yield 78% (Found: C, 52.56; H, 5.13; N, 6.03.C39H44Cl3N4P2Si2Nb requires C, 52.86; H, 5.01; N, 6.32%). 1H NMR (CDCl3, 295 K), d 6.85 (t, 4JHP = 2.6, 2 H, CH2), 8.45 (dd, 3JHH = 2.2, 4JHP = 0.8, 1 H, H3), 7.68 (dd, 3JHH = 2.4, 4JHP = 0.8, 1 H, H39), 6.01 (dd, 3JHH = 2.2, 3JHP = 0.5, 1 H, H4), 5.99 (dd, 3JHH = 2.4, 3JHP = 0.7 Hz, 1 H, H49), 7.45–7.18 (m, 20 H, PPh2), 0.28 (s, Me3SiC]] ] ). 13C-{1H} NMR (CDCl3), d 58.82 (t, 3JPC = 14.8, CH2), 146.13 (s, C3), 144.69 (s, C39), 114.19 (s, C4), 114.07 (s, C49), 146.28 (d, 1JPC = 22.7, C5), 144.79 (d, 1JPC = 15.0 Hz, C59), 133.68– 128.37 (m, Ph), 0.07 (s, Me3Si), 265.62 (s, C]] ] C). 31P-{1H} NMR (CDCl3, H3PO4 as reference), d 232.87, 232.35 (AB, JAB = 34.2 Hz, PPh2, P9Ph2). IR (Nujol, cm21) 1710 [n(C]] ] C)], 370, 322 [n(Nb–Cl)]. [NbCl3(bppzm)(PhC]] ] CMe)] 7. The synthetic procedure was the same as for complex 1, using [NbCl3(dme)(PhC]] ] CMe)] (0.250 g, 0.62 mmol) and bppzm (0.318 g, 0.62 mmol), to give complex 7 as a brown solid.Yield 75% (Found: C, 57.34; H, 3.96; N, 6.96. C40H34Cl3N4P2Nb requires C, 57.75; H, 4.12; N, 6.73%). 1H NMR (CDCl3, 295 K), d 7.08 (t, 4JHP = 2.8, 2 H, CH2), 8.63 (dd, 3JHH = 2.4, 4JHP = 0.9, 1 H, H3), 7.39 (dd, 1 H, H39), 6.01 (dd, 3JHH = 2.4, 3JHP = 0.7, 1 H, H4), 5.86 (dd, 3JHH = 2.5, 3JHP = 0.7, 1 H, H49), 7.45–7.21 (m, 20 H, PPh2), 7.75 [dd, 3JHo,m = 6.9, 4JHo,p = 1.3 Hz, 2 H, Ho(PhC]] ] )], 7.45–7.21 [m, 3 H, Hm, Hp(PhC]] ] )], 3.58 (s, ]] ] CMe). 13C-{1H} NMR (CDCl3), d 59.01 (t, 3JPC = 15.1, CH2), 147.03 (s, C3), 144.65 (s, C39), 114.24 (s, C4), 113.93 (s, C49), 146.73 (d, 1JPC = 23.0, C5), 144.92 (d, 1JPC = 19.6 Hz, C59), 136.94–128.44 (m, Ph), 24.23 (s, ]] ] CMe), 256.78, 235.24 (s, C]] ] C). 31P-{1H} NMR (CDCl3, H3PO4 as reference), d 232.92, 232.36 (AB, JAB = 33.9 Hz, PPh2, P9Ph2). IR (Nujol, cm21) 1692 [n(C]] ] C)], 384, 320 [n(Nb]Cl)]. [NbCl3(bppzm)(PhC]] ] CSiMe3)] 8. The synthetic procedure was the same as for complex 1, using [NbCl3(dme)(PhC]] ] CSiMe3)] (0.250 g, 0.54 mmol) and bppzm (0.278 g, 0.54 mmol), to give complex 8 as a brown solid.Yield 68% (Found: C, 57.05; H, 4.18; N, 5.98. C42H40Cl3N4P2SiNb requires C, 56.67; H, 4.53; N, 6.29%). 1H NMR (CDCl3, 295 K), d 7.00 (t, 4JHP = 2.8, 2 H, CH2), 8.58 (dd, 3JHH = 2.2, 4JHP = 0.7, 1 H, H3), 7.49 (dd, 3JHH = 2.5, 4JHP = 0.8, 1 H, H39), 6.03 (dd, 3JHH = 2.2, 3JHP = 0.6, 1 H, H4), 5.89 (dd, 3JHH = 2.5, 3JHP = 0.8, 1 H, H49 ), 7.47–7.20 (m, 20 H, PPh2), 7.85 [dd, 3JHo,m = 7.0, 4JHo,p = 1.2 Hz, 2 H, Ho(PhC]] ] )], 7.47–7.20 [m, 3 H, Hm, Hp(PhC]] ] )], 0.39 (s, ]] ] CSiMe3). 13C-{1H} NMR (CDCl3), d 58.89 (t, 3JPC = 14.8, CH2), 146.70 (s, C3), 144.55 (s, C39), 114.04 (s, C4), 114.00 (s, C49), 146.56 (d, 1JPC = 21.0, C5), 144.80 (d, 1JPC = 19.7 Hz, C59), 133.56–128.06 (m, Ph), 20.12 (s, ]] ] CSiMe3), 260.43, 246.27 (s, C]] ]C). 31P-{1H} NMR (CDCl3, H3PO4 as reference), d 232.80, 232.20 (AB, JAB = 35.7 Hz, PPh2, P9Ph2). IR (Nujol, cm21) 1698 [n(C]] ] C)], 382, 326 [n(Nb–Cl)]. [PdCl2(bppzm)] 9.To a CH2Cl2 (50 cm3) solution of [PdCl2(PhCN)2] (0.371 g, 0.97 mmol) was added an equimolar quantity of bppzm (0.500 g, 0.97 mmol). The solution was stirred for 5 h at room temperature. The solvent was removed in vacuo and a yellow solid was obtained. Yield 85% (Found: C, 53.51; H, 3.98; N, 8.21. C31H26Cl2N4P2Pd requires C, 53.64; H, 3.78; N, 8.07%). 1H NMR (CDCl3, 295 K), d 6.71 (s, 2 H, CH2), 7.38 (d, 3JHH = 1.5, 2 H, H3), 5.76 (dd, 3JHH = 1.4, 3JHP = 1.3 Hz, 2 H, H4), 7.68–7.26 (m, 20 H, Ph). 13C-{1H} NMR (CDCl3), d 62.68 (t, 3JPC = 3.5 Hz, CH2), 140.28–140.14 (m, C3), 118.98– 118.89 (s, C4), 134.41–128.26 (m, Ph). 31P-{1H} NMR (CDCl3, H3PO4 as reference), d 4.66 (s, PPh2). IR (Nujol, cm21) 332, 309 [n(Nb]Cl)]. [PtCl2(bppzm)] 10. The synthetic procedure was the same as for complex 9, using [PtCl2(PhCN)2] (0.457 g, 0.97 mmol) and bppzm (0.500 g, 0.97 mmol), to give complex 10 as a yellow solid. The crystals for X-ray diVraction were grown from a solution of CH2Cl2–Et2O by slow evaporation of the solvent.Yield 80% (Found: C, 47.34; H, 3.11; N, 6.98. C31H26Cl2N4P2Pt requires C, 47.58; H, 3.35; N, 7.16%). 1H NMR (CDCl3, 295 K), d 6.70 (s, 2 H, CH2), 7.33 (s, 2 H, H3), 5.70 (s, 2 H, H4), 7.63– 7.29 (m, 20 H, Ph). 13C-{1H} NMR (CDCl3), d 62.44 (s, CH2), 139.85 (t, 3JPC = 5.5, C3), 118.46 (t, 3JPC = 4.0 Hz, C4), 134.17– 128.01 (m, Ph). 31P-{1H} NMR (CDCl3, H3PO4 as reference), d 211.30 (t, JPPt = 3623.2 Hz, PPh2).IR (Nujol, cm21) 328, 293 [n(Nb]Cl)]. Crystal data for 10. Yellow crystals (0.50 × 0.30 × 0.23 mm) are triclinic with space group P1� and lattice constants a = 10.32(2), b = 10.965(6), c = 17.486(8) Å, a = 94.04(5), b = 101.65(9), g = 117.75(5)8, V = 6164(13) Å3, Z = 2, Dc = 1.627 g cm23, m = 45.27 cm21. Reflections were collected at 25 8C on a NONIUS-MACH3 diVractometer equipped with graphite monochromated radiation (l = 0.7107 Å), 6201 reflections collected (2 < q < 28), 5450 reflections with I > 2s(I).Data were corrected in the usual fashion for Lorentz and polarization eVects, and empirical absorption correction was based on a y scan (range of transmission factors 0.610–1.000).16 Data/ parameters 6201/382. The structure was solved by direct methods17 and refinement on F2 was carried out by full-matrix least squares analysis.18 Anisotropic temperature parameters were considered for all non-hydrogen atoms, while hydrogen atoms were included in calculated positions but not refined.Final disagreement indices are R1 = 0.0378, wR2 = 0.1085, GOF = 0.953, largest diVerence peak and hole 2.024 and 21.490 e Å23. CCDC reference number 186/1164. Acknowledgements We gratefully acknowledge financial support from the Dirección General de Enseñanza Superior e Investigación, Spain (Grant No. PB95-0023-C02-01). References 1 E. M. Miller and B. L. Shaw, J. Chem. Soc., Dalton Trans., 1974, 480; J.Powell, A. Kuksis, C. J. May, S. C. Nyburg and S. J. Smith, J. Am. Chem. Soc., 1981, 103, 5941; W. Keim, New J. Chem., 1987, 11, 531; U. Klabunde, T. H. Tulip, D. C. Roe and S. D. Ittel, J. Organomet. Chem., 1987, 334, 141; E. Lindner and H. Norz, Chem. Ber., 1990, 123, 459; H. Werner, A. Stark, M. Schultz and J. Wolf, Organometallics, 1992, 11, 1126; D. Soulivong, D. Matt, R. Ziessel, L. Douce and R. Deschenaux, Tetrahedron Lett., 1993, 34, 1151; D. Matt, N. Sutter-Beydoun, J.-P.Brunette, F. Balegroune and D. Grandjean, Inorg. Chem., 1993, 32, 3488. 2 See, for example: T. B. Rauchfuss, F. T. Patino and D. M. Roundhill, Inorg. Chem., 1975, 3, 652; F. Mathey and F. Mercier, J. Organomet. Chem., 1979, 177, 255; D. Sinou, Bull. Soc. Chim. Fr., 1987, 3, 480; O. Stelzer and K.-P. Langhans, The Chemistry of Organophosphorus Compounds, ed. F. R. Hartley, Wiley, New York, 1989, pp. 191–254; W. Levason, ibid., pp. 567–641; W. L. Wilson, J. H. Nelson andJ. Chem. Soc., Dalton Trans., 1998, 3737–3743 3743 N. W. Alcock, Organometallics, 1990, 9, 1699; A. Bader and F. Lindner, Coord. Chem. Rev., 1991, 108, 27. 3 C. A. McAuliVe, Phosphorus, Arsenic, Antimony and Bismuth Ligands, in Comprehensive Coordination Chemistry, eds. G. Wilkinson, R. D. Gillard and J. A. McCleverty, Pergamon, Oxford, UK, 1987, vol. 2, p. 989; W. Levason, The Chemistry of Organophosphorus Compounds, eds. F. R. Hartley and S. Patai, Wiley, New York, 1990, vol. 1, p. 617; F. A. Cotton and B. Hong, Prog. Inorg. Chem., 1992, 40, 179; H. A. Mayer and W. C. Kaska, Chem. Rev., 1994, 94, 1239. 4 P. K. Byers, A. J. Canty and R. T. Honeyman, Adv. Organomet. Chem., 1992, 34, 1. 5 J. Fernández-Baeza, F. A. Jalón, A. Otero and M. E. Rodrigo- Blanco, J. Chem. Soc., Dalton Trans., 1995, 1015. 6 M. Fajardo, A. de la Hoz, E. Díez-Barra, F. A. Jalón, A. Otero, A. Rodriguez, J. Tejeda, D. Belleti, M. Lanfranchi and M. A. Pellinghelli, J. Chem. Soc., Dalton Trans., 1993, 1935. 7 F. A. Jalón, B. R. Manzano, A. Otero and M. C. Rodriguez-Pérez, J. Organomet. Chem., 1995, 494, 179. 8 F. A. Cotton, L. R. Falvello and R. C. Najjar, Inorg. Chem., 1983, 22, 375. 9 J. Sandström, Dynamic NMR Spectroscopy, Academic Press, New York, 1982. 10 See, J. L. Templeton, Adv. Organomet. Chem., 1989, 29, 1. 11 K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination Compounds, Wiley-VCH, New York, 1997. 12 See, for example: W. Lesueur, E. Solari, C. Floriani, A. Chiesi-Villa and C. Rizzoli, Inorg. Chem., 1997, 36, 3354. 13 E. J. Roskamp and S. F. Pedersen, J. Am. Chem. Soc., 1987, 109, 6551. 14 J. Tsuji, Organic Synthesis with Palladium Compounds, Springer, Berlin, 1980, vol. 10, pp. 2–3. 15 E. Díez-Barra, A. de la Hoz, A. Sánchez-Migallón and J. Tejeda, Heterocycles, 1992, 34, 1365. 16 A. C. T. North, D. C. Phillips and F. S. Mathews, Acta Crystallogr., Sect. A, 1968, 24, 351. 17 A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, M. C. Burla, G. Polidori and M. Camalli, J. Appl. Crystallogr., 1994, 435. 18 G. M. Sheldrick, Program r the Refinement of Crystal Structures from DiVraction data, University of Göttingen, Göttingen, 1993. Paper 8/05683H

ISSN:1477-9226    

DOI:10.1039/a805683h

出版商:RSC    

年代:1998

数据来源: RSC