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DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1999, 1937–1943 1937 Technetium(V) and rhenium(V) complexes of biguanide derivatives. Crystal structures Andrea Marchi,*†a Lorenza Marvelli,a Michela Cattabriga,b Roberto Rossi,a Maria Neves,c Valerio Bertolasi d and Valeria Ferretti d a Laboratorio di Chimica Inorganica e Nucleare, Dipartimento di Chimica, Università di Ferrara, via L. Borsari 46, 44100 Ferrara, Italy b Dipartimento di Chimica, Università di Venezia, Dorsoduro 2137, 30123 Venezia, Italy c Departamento de Química, Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2685 Sacavém, Portugal d Centro di Strutturistica DiVrattometrica, Dipartimento di Chimica, Università di Ferrara, via L.Borsari 46, 44100 Ferrara, Italy Received 29th January 1999, Accepted 22nd April 1999 Biguanidine ligands HLn (HL1 = 1,1-dimethylbiguanide, HL2 = 1-phenethylbiguanide, HL3 = 1-phenylbiguanide) formed disubstituted cationic oxo- and nitrido-complexes [MO(HLn)2]31 (M = Tc or Re) and [TcN(HLn)2(H2O)]21.They are characterised by the presence of a network of N–H ? ? ? X (X = Cl or H2O) intra- and inter-molecular hydrogen bonds. The imido precursor of ReV [Re(NMe)(PPh3)2Cl3] formed monosubstituted complexes [Re(NMe)(HL1,2)(PPh3)Cl]21. In alkaline solutions deprotonation of ligands occurs and monocationic, disubstituted oxo- and imido-species [MO(Ln)2]1 (M = Tc or Re), [Re(NCH3)(L1,3)2]1 and neutral nitrido complexes [TcN(Ln)2] are obtained.Elemental analyses, FT-IR and NMR spectroscopy and conductivity measurements are consistent with the proposed formulations. Crystal structures of [TcO(L1)2]1 and [TcN(HL1)2(H2O)]21 were determined. The former shows a square pyramidal geometry in which the C–N bond distances are equivalent and indicative of p delocalisation on the chelate ring. The latter displays a pseudo-octahedral geometry with a water molecule trans to the Tc]] ] N multiple bond. The C–N bond distances inside the ligands (1.30 and 1.38 Å) are consistent with single and double bond character, and less p delocalisation through the whole ligands.Introduction Biguanide and its N-substituted derivatives are bidentate ligands which contain nitrogen donor atoms. From a chemical and structural point of view biguanide may be considered as derived from the substitution of both the oxygen atoms of biuret by imino ]] NH groups. These compounds are considered strong s- and p-donating ligands which form stable complexes with transition metal ions in high or usual oxidation states utilising the availability of vacant d orbitals of the metal which may overlap with the filled p orbitals of the ligand.1 They are highly coloured and complexes of bivalent metals such as copper, nickel, and cobalt with biguanides have long been known.2 In 1961 Ray3 reported a systematic investigation of the syntheses and properties of these and other metal complexes including the first oxorhenium( V) complex [ReO(Big)2(OH)][OH]2 (Big = biguanide).More recently, some oxorhenium(V) complexes of biguanide and 1,1-dimethylbiguanide have been formulated as [ReO- (HL)2X]X2, [ReO(L)2X] (X = Cl2 or OH2) and [Re(HL)2- (OH)2]Cl3 (HL = biguanide) on the basis of elemental analysis H2N N H NH2 H2N N H NH2 Biguanide Biuret C C C C O O NH NH † Present address: Dipartimento di Chimica, Università di Ferrara, via L. Borsari 46, 44100 Ferrara, Italy. E-mail: mgl@dns.unife.it and IR spectra.4 Up to now and to our knowledge, no technetium complex has been described.From a chemical point of view the formation of a complex has been considered similar to a protonation process.5 Moreover, EPR and UV spectral studies have been carried out to understand the chemical and pharmaceutical properties of this class of molecules.1b,6 Biguanides have attracted considerable attention for their hypoglycaemic activity 7 and, in particular, metformin (1,1-dimethylbiguanide) is an antidiabetic medication which has been used for over 30 years.This class of compounds has been also studied as antimalarial drugs 8 and more recently for therapeutic treatment of pain, anxiety, and memory disorders.9 The present paper deals with the synthesis and characterisation of rhenium(V) and technetium(V) complexes of biguanide derivatives HLn and the first structurally characterised oxo- and nitrido-complexes of technetium. H N H N H N R1 n = 2 R1 = H, R2 = C2H4-Ph HLn ligands N n = 1 R1 = R2 = Me n = 3 R1 = H, R2 = Ph N N NH C NH R2 C H 1,1-dimethylbiguanide 1-phenethylbiguanide 1-phenylbiguanide1938 J.Chem. Soc., Dalton Trans., 1999, 1937–1943 Results and discussion Syntheses Oxotechnetium(V) and oxorhenium(V) complexes. The violet complexes [TcO(HLn)2]31 1–3 were prepared by reaction of [TcOCl4]2 precursor with HLn ligands under mild conditions. The corresponding oxorhenium(V) complexes [ReO(HLn)2]31 7–9 were obtained by exchange reactions of [ReO(XPh3)2Cl3] (X = P or As) (Scheme 1).The oxorhenium(V) precursors showed a lower reactivity than [TcOCl4]2 salt which readily reacted with HLn ligands. No diVerence of reactivity was observed between the two oxorhenium(V) compounds. Complexes [MO(HLn)2]31 are violet, air stable and soluble in water, MeOH, Me2SO. Conductivity measurements in Me2SO solution seem in agreement with 3 : 1 electrolytes. The oxometal complexes [TcO(Ln)2]1 4–6 and [ReO(Ln)2]1 10–12 were synthesized in good yields following two diVerent procedures. When the reactions were carried out in the presence of base (KOH in MeOH) deprotonation of ligands occurred and the corresponding monocationic species formed.These compounds were also isolated starting from solutions of 1–3 or 7–9 by adding some drops of alkaline solution. The formation of [ReO4]2 was observed in the syntheses of 10–12 since these reactions were performed in air, at neutral or weakly alkaline pH values and under these conditions [ReO4]2 replaced Cl2 as counter ion.On the contrary, [TcO4]2 anion was never detected in the syntheses of 4–6 because technetium complexes are more diYcult to oxidise than are their rhenium analogs.10 In order to evaluate the possibility to form oxotechnetium compounds starting from pertechnetate ion, reactions in aqueous basic solution with Na2S2O4 as reducing agent were performed. Substitution of the OH2 counter ion with [BPh4] 2 gave good crystals of 4 for X-ray diVraction analysis.All of these oxo complexes [MO(Ln)2]1 are yellow and air stable in both the solid state and solution. They are soluble in MeOH, Me2SO and behave as monoelectrolytes in solution. Nitridotechnetium(V) complexes. Cationic complexes [TcN- (HLn)2(H2O)]21 13–15 were prepared starting from the precursor [TcN(PPh3)2Cl2] (Scheme 2). When the reactions were carried out with HL1,2 ligands the presence of NEt3 was required since the former were available as their HCl salts.The corresponding neutral species 16–18 were obtained in basic solution (KOH in MeOH) or alternatively after dissolution of 13–15 in MeOH and addition of alkaline solution. Cationic [TcN(HLn)2(H2O)]21 and neutral [TcN(Ln)2] compounds are yellow, air stable and soluble in CH2Cl2, MeOH, Me2SO. Conductivity measurements in Me2SO are in accord with the proposed formulations. Crystals suitable for X-ray diVraction studies of [TcN(HL1)2(H2O)]21 13 were grown from dichloromethane –ethanol.Imidorhenium(V) complexes. Monosubstituted imido com- Scheme 1 Re Ph3X Cl XPh3 Cl O Cl Tc Cl Cl Cl Cl O O Tc O O O M N N N N O M N N N N O Tc N N N N O OH – (X = P, As) OH –, S2O4 2– HLn M = Tc, 1-3 Re, 7-9 HLn M = Tc, 4-6 Re, 10-12 HN N + + HLn NH N – N N OH- H+ – 4-6 3+ plexes [Re(NMe)(HL1,2)(PPh3)Cl]21 19, 20 were synthesized starting from the easily available species [Re(NMe)(PPh3)2Cl3] (Scheme 3). Even if the ligands were used in a 1 : 2 stoichiometric ratio, attempts to obtain the corresponding disubstituted compounds failed.Monocationic disubstituted compounds 21 and 22 were recovered in the presence of base (NEt3). The complexes [Re(NMe)(HL1,2)(PPh3)Cl]21 and [Re(NMe)(L1,3)2]1 behave as 2 : 1 and 1 : 1 electrolytes, respectively in Me2SO solution. Intentionally, we decided to synthesize only some imido complexes with the aim to make a comparison of reactivity between oxo- and imido-rhenium(V) precursors.Spectroscopy In this discussion we report FT-IR wavenumbers of the ligands for an easier comparison with those of complexes. Infrared spectra of the HLn (n = 1–3) ligands exhibit an intense absorption band in the range 3100–3500 cm21 assignable to the stretching vibration of the NH groups. It is probable that interor intra-molecular hydrogen bonds overlap with NH vibrations and are responsible for this broad band. The presence of intramolecular hydrogen bonds was confirmed by structural studies of biguanides.5b,11 A set of strong bands observed in the range 1500–1700 cm21 may be attributed to C]] N stretch and NH deformation.All IR spectra of the complexes [MO(HLn)2]31 (M = Tc 1–3 or Re 7–9), [TcN(HLn)2(H2O)]21 13–15, and [Re(NMe)- (HL1,2)(PPh3)Cl]21 19, 20 display a broad intense band in the range 3100–3500 cm21 due to the stretching vibrations of the N–H groups and overlapped with stretchings of H2O or ROH (R = Me or Et) involved in hydrogen bonds.The strong bands observed in the range 1640–1700 cm21 are assigned to the n(C]] NH) of co-ordinated groups, and those at 1500–1610 cm21 attributed to n(C–N–C) (ring) and d(NH).1a,12 A new band appearing at 1320–1220 cm21 was assigned to ring vibration and supports the formation of a chelate ring.12b The infrared spectra of technetium and rhenium oxo complexes exhibit a strong M]] O (M = Tc or Re) absorption peak at 980–997 and at 990–1007 cm21, respectively.These MO stretching values are comparable with those observed for other square-pyramidal oxo complexes of Tc and Re containing s- and p-donating ligands.13 The spectra of nitrido complexes show a mediumintensity band which falls in the appropriate range for the Tc]] ] N moiety (1059–1088 cm21). Finally, a band at ca. 1095 cm21 indicates the presence of PPh3 in 19 and 20. The IR spectra of the deprotonated complexes do diVer marginally from those discussed above.For some of them, the region 3100–3500 cm21 appears better resolved, probably due to the absence of hydro- Scheme 2 Tc Ph3P Cl PPh3 Cl N Tc N N N N N H2 O Tc N N N N N 13-15 OH – 2+ HLn H + OH – 16-18 NH HLn N N HN Scheme 3 Re N N N N NMe Re Ph3P Cl PPh3 Cl NMe Cl Re N N PPh3 Cl NMe HL1,2 NEt3 HL1,3 21, 22 19, 20 2+ HN + N NJ. Chem. Soc., Dalton Trans., 1999, 1937–1943 1939 gen bonds (see Experimental section). Indeed there is an appreciable low frequency shifting of n(C]] N) (1600–1620 cm21) with respect to the values of the corresponding protonated species, as well as to HLn unco-ordinated ligands.This fact may be attributed to p-electron delocalisation on the chelate ring. Moreover, in these complexes M]] O and Tc]] ] N stretching vibrations are observed at lower wavenumbers. Finally, disappearance of the characteristic band of the PPh3 moiety in [Re(NMe)(L1,3)2]Cl 21, 22 is consistent with the formulation of the disubstituted complexes.Proton NMR spectra of the metal complexes, recorded in Me2SO-d6 solution, show a downfield shift of the NH resonances with respect to those of the unco-ordinated ligands, while aliphatic and aromatic protons do not undergo significant chemical shifts. For the technetium and rhenium oxo complexes, containing the ligands in their protonated as well as deprotonated form, the ]] NH resonances are the more signifi- cant data in the 1H NMR spectra. In particular the spectra for the oxorhenium complexes exhibit signals at higher values than those of corresponding technetium compounds.Comparing [MO(HLn)2]31 (M = Tc 1–3 or Re 7–9) with [MO(Ln)2]1 (M = Tc 4–6 or Re 10–12) complexes an analogous NH pattern may be observed in all spectra, although the signals for the latter compounds are shifted upfield with respect to the former. A similar behaviour is also observed for the corresponding nitrido derivatives. This trend may be discussed in terms of an increased shielding arising from a strong p conjugation along the chelate ring, in accord with the C–N bond distances of complexes [TcO(L1)2]1 4 and [TcN(HL1)2(H2O)]21 13 (see description of the structures) which indicate a more extensive p delocalization over the whole ligand molecule in 4 than in 13.It is interesting that complex 4 possesses a trans configuration while the corresponding compound 13 is cis. Although isomers could be expected, NMR experiments in solution and at room temperature did not reveal their presence for all oxoand nitrido-complexes.This fact cannot be attributed to steric impediments as well as electronic factors and it is hard to explain it. The presence of only one isomer could be due to a high energy barrier which does not allow inversion. The 31P and 1H NMR spectra of imido complexes 19, 20 are consistent with the formation of monosubstituted compounds such as [Re(NMe)(HL1,2)(PPh3)Cl]21. In particular, the phosphorus NMR spectra exhibit singlets at d28.95 and 26.38 for the co-ordinated PPh3 moiety of 19 and 20, respectively.The 1H NMR spectra show two singlets in the range d 10.95–8.6 attributable to (]] NH) protons. For the complexes [Re(NMe)- (L1)2]1 21 and [Re(NMe)(L2)2]1 22, the 1H spectra recorded at room temperature, as well as at 60 8C, are clearly consistent with the presence of two molecules of the ligand. In particular there is a set of four singlets (d 11.3–9.1) having equal intensity and attributed to the four ]] NH protons of the co-ordinated ligands.Another set of two singlets, twice as intense, at d 7.0– 6.4 is assigned to NH2 groups. This NMR feature could suggest the presence of a 1 :1 mixture of cis and trans isomers about the metal as well as a linear–bent isomerisation at the nitrene ligand. However, NMR spectra of the oxo- or nitrido-complexes, discussed above, did not display a cis–trans isomerization in solution at room temperature, and we believe that for 21 and 22 a non-axial disposition of the ReN–R bond is a plausible explanation.14 A series of UV absorption spectra and their pH dependence were studied in air to evaluate the basicity constants of coordinated biguanide ligand and which complexes are present in solution at diVerent pH values.In these experiments a 0.5 M solution of H3PO4 (25 cm3) was mixed in various ratios with a 1.0 M solution of NaOH and nine solutions at pH values ranging from 1.9 to 6.9 were prepared.All solutions were adjusted to ionic strength I = 0.1 M with Na2SO4. To a 1024 M aqueous solution (10 cm3) of the complex 7 an aliquot (1.0 cm3) of each solution was added and UV spectra recorded. The UV spectra collected in the pH range 1.9–3.5 show the presence of both [ReO(HL1)2]31 and [ReO(HL1)(L 1)]21 species, while at pH 3.55– 4.35 [ReO(HL1)(L1)]21 and [ReO(L1)2]1 are present. The latter was stable until pH 6.9 while at higher pH values oxidation of rhenium(V) to [ReO4]2 took place and it was complete at pH 12 after 2.5 h.From these experiments a pK1 of 3.55 and a pK2 of 4.35 have been estimated. In conclusion, we may assert that deprotonation of two molecules of ligand occurs in two well distinct steps although the two pK values are very similar. In addition, at physiological pH value the species in solution are those that contain both ligands in deprotonated form. These results may be also extended to other complexes taking into account that technetium(V) is more diYcult to oxidise than rhenium(V) 10 and the Tc]] ] N fragment is more stable than Tc]] O in alkaline solution.Crystal structures The [TcO(C4H10N5)2]1 cation of complex 4 displays a noncrystallographic C2 symmetry and a square-pyramidal geometry around Tc with two deprotonated 1,1-dimethylbiguanide molecules on the basal plane and an oxygen at the apex (Fig. 1). The Tc atom is displaced from the plane defined by N(1), N(2), N(6) and N(7) atoms toward O(1) by 0.6777(3) Å.The Tc]] O(1) bond distance of 1.645(3) Å (Table 1) indicating strong multiple bond character is in agreement with the distances found in other square-pyramidal technetium(V) oxo complexes.13a,16 The Tc–N bond distances, in the range 1.97–2.01 Å, are shorter than those observed in compound 13 due to the concomitant presence of a Tc]] O(oxo) group, which is a softer base than Tc]] ] N- (nitrido) group, and partial negative charges on the enaminic NH moieties.The C–N bonds within the two deprotonated dimethylbiguanide ligands display, in fact, almost equivalent distances, from 1.32 to 1.35 Å, indicative of a delocalisation of the double bonds and negative charges throughout the whole ligands. In the crystal packing the cation complexes are linked by hydrogen bonds between aminic hydrogens and deprotonated nitrogens while the N(1)–H and N(7)–H enaminic groups are engaged in the capture of a methanol molecule.The [TcN(C4H12N5)2(H2O)]21 cation belonging to complex 13 displays a non-crystallographic Cs symmetry and an approximately octahedral geometry with two molecules of 1,1-dimethylbiguanide on the basal plane and a water molecule at the apical position trans to the nitrido group (Fig. 2). The four basal N atoms lie approximately on a plane and the Tc atom is displaced from this plane by 0.4384(2) Å toward N(1). The Tc]] ] N triple bond distance of 1.616(2) Å is comparable with other reported distances for technetium(V) nitrido complexes.17 The long Tc–OH2 distance of 2.691(2) Å is ascribed to the strong trans influence of the nitrido ligand and is in agreement with the distances, in the range 2.48–2.95 Å, found in analogous compounds.18 These Tc–O bonds are abnormally long and can Fig. 1 An ORTEP15 view of the cation of compound 4 showing thermal ellipsoids at 30% probability.1940 J.Chem. Soc., Dalton Trans., 1999, 1937–1943 be considered as secondary bonds, intermediate between true bonds and van der Waals contacts.The presence of a water molecule in trans position is associated with a decreasing pyramidalisation of the technetium co-ordination polyhedron measured by the N]] ] Tc–N(cis) mean angle, a, which is 1028 in the present compound, and in typical square-pyramidal technetium nitrido complexes falls in the range 105–1088. The shortening of the Tc–N (sp2, enaminic) bond distances, observed in the range 2.07–2.08 Å, with respect to the Tc–N (sp3, aminic) ones of 2.15–2.22 Å,19 can be attributed to the diVerent hybridisations of the N atoms. The C–N single and double bond distances inside the ligands, of 1.30 and 1.38 Å on average respectively, display a small degree of delocalisation, the standard values of C]] N and C(sp2)–N(sp2) bond lengths being 1.27 and 1.41 Å, respectively.The crystal packing is determined by a complex network of hydrogen bonds involving all the aminic hydrogens, the chloride anions, the water molecule and the enaminic N(2)–H group.Fig. 2 An ORTEP15 view of compound 13 showing thermal ellipsoids at 30% probability. Table 1 Selected bond distances (Å) and angles (8) for complexes [TcO(L1)2]1 4 and [TcN(HL1)2(H2O)]21 13 with estimated standard deviations in parentheses [TcO(L1)2]1 4 Tc–O(1) Tc–N(1) Tc–N(2) N(1)–C(1) N(2)–C(2) N(3)–C(1) N(3)–C(2) N(4)–C(1) N(5)–C(2) O(1)–Tc–N(1) O(1)–Tc–N(2) N(1)–Tc–N(2) N(1)–Tc–N(7) N(1)–Tc–N(6) 1.645(3) 1.973(2) 2.012(3) 1.333(4) 1.336(4) 1.324(4) 1.347(3) 1.343(4) 1.331(4) 112.0(1) 108.4(1) 82.9(1) 83.4(1) 135.2(1) Tc–N(6) Tc–N(7) N(6)–C(5) N(7)–C(6) N(8)–C(5) N(8)–C(6) N(9)–C(5) N(10)–C(6) O(1)–Tc–N(7) O(1)–Tc–N(6) N(6)–Tc–N(7) N(2)–Tc–N(6) N(2)–Tc–N(7) 1.984(2) 2.006(2) 1.353(4) 1.352(4) 1.340(4) 1.345(3) 1.318(4) 1.342(4) 112.7(1) 106.4(1) 83.5(1) 84.0(1) 145.2(1) [TcN(HL1)2(H2O)]21 13 Tc–N(1) Tc–N(2) Tc–N(3) N(2)–C(1) N(3)–C(2) N(4)–C(1) N(4)–C(2) N(5)–C(1) N(6)–C(2) N(1)–Tc–N(2) N(1)–Tc–N(3) N(2)–Tc–N(7) N(2)–Tc–N(3) N(2)–Tc–N(8) N(1)–Tc–O(1) 1.616(2) 2.069(2) 2.080(2) 1.292(2) 1.299(2) 1.381(2) 1.375(2) 1.331(2) 1.344(2) 104.9(1) 100.9(1) 89.5(1) 84.2(1) 153.9(1) 177.3(1) Tc–O(1) Tc–N(7) Tc–N(8) N(7)–C(5) N(8)–C(6) N(9)–C(5) N(9)–C(6) N(10)–C(5) N(11)–C(6) N(1)–Tc–N(7) N(1)–Tc–N(8) N(3)–Tc–N(8) N(7)–Tc–N(8) N(3)–Tc–N(7) 2.691(2) 2.071(2) 2.076(2) 1.292(2) 1.303(2) 1.380(2) 1.380(2) 1.338(3) 1.341(2) 101.9(1) 101.2(1) 90.6(1) 85.4(1) 157.2(1) Conclusion The paucity of relevant IR and NMR spectral data available in the literature 1a,12a,20 makes diYcult any comparison with our results. The complexes here reported have been synthesized by facile exchange reactions between ligands and appropriate technetium and rhenium precursors.They have been fully characterised by FT-IR and NMR spectroscopy and the crystal structures of 4 and 13 determined. Conductivity measurements in Me2SO solution, of all cationic complexes, seem in agreement with literature data 21 for 1 : 1, 2 : 1 and 3 : 1 electrolytes.The charge on the complexes is neutralised by a network of N–H? ? ? Cl hydrogen bonds as demonstrated by crystal structure determinations.22 We have demonstrated that it is possible to promote deprotonation of the co-ordinated ligand and consequently to change the charge of the final complex. This aspect is of great importance in the development of 99mTC and 186/188Re radiopharmaceuticals and studies in order to understand which species are present in the biological environment could be performed.Syntheses of the corresponding 99mTcO complexes and preliminary biodistribution studies in vivo are reported elsewhere.23 Experimental Materials and methods CAUTION: Technetium-99 is a low-energy b2 emitter (E = 292 keV, t1/2 = 2.12 × 105 years). When this material is handled, normal radiation safety procedures must be used to prevent contamination. All manipulations of solids or solutions were performed in a laboratory approved for low-level radioactivity.Unless otherwise noted, all chemicals were reagent grade used without further purification. The salt [NH4][99TcO4] was obtained from the Radiochemical Centre, Amersham, UK; [AsPh4][TcOCl4],24 [TcN(PPh3)2Cl2],25 [ReO(XPh3)2Cl3] 26 (X = P or As) and [Re(NMe)(PPh3)2Cl3] 27 were prepared according to literature methods. The ligands 1,1-dimethylbiguanide (HL1), 1-phenylbiguanide (HL3) (Sigma) and 1-phenethylbiguanide (HL2) (Janssen Chimica) are commercially available products.Biguanide was synthesized according to the procedure of Karipides and Fernelius.28 Elemental analyses were performed using a Carlo Erba Instruments model EA1110 apparatus. FT-IR Spectra were recorded in the range 4000–200 cm21 on a Nicolet 510P FT-IR instrument in KBr, using a Spectra-Tech collector diVuse reflectance accessory, UV-Vis spectra on a Perkin-Elmer Lambda 5 spectrophotometer.pH Measurements were made with a Hanna HI-8417 Digital pH-meter using commercial buVer solutions (pH 4 and 7) as reference points. Proton NMR spectra of Me2SO-d6 solutions of complexes were examined on a Varian Gemini 300 spectrometer with SiMe4 as internal standard, 31P-{1H} NMR spectra on the same instrument in Me2SO-d6 solutions with a 85% H3PO4 solution as external standard. Conductivities were measured with an Amel Model 134 conductivity meter. The conductivity data were obtained at sample concentrations of ca. 1 × 1024 M in Me2SO solutions at room temperature (21 8C). Synthesis of complexes Oxotechnetium(V) complexes [TcO(HLn)2]Cl3 1–3 (n 5 1–3). To the salt [AsPh4][TcOCl4] (80 mg, 0.12 mmol) dissolved in 30 cm3 of CH2Cl2 the ligand (0.48 mmol) was added as a solution in MeOH (1 cm 3). The reaction mixture was gently warmed for 20 min and a change from pale green to violet was observed. Upon slow evaporation of solvent reddish violet crystals of the complexes were obtained.The solid was filtered oV, washed with EtOH and dried with Et2O. Yields were determined on starting technetium complex. [TcO(HL1)2]Cl3 1. Yield 90% (Found: C, 20.3; H, 4.6; N, 29.0. C8H22Cl3N10OTc requires C, 20.0; H, 4.6; N, 29.2%). IR (KBr):J. Chem. Soc., Dalton Trans., 1999, 1937–1943 1941 997 [n(Tc]] O)], 1595, 1630, 1668 [n(C–N–C), d(NH), n(C]] N)], and 3140, 3275 cm21 [n(NH, NH2)]. NMR (Me2SO-d6): dH 11.0 (2 H, s, C]] NH), 9.85 (2 H, s, C]] NH), 9.0 (2 H, s, CNHC), 7.7 (4 H, br s, NH2) and 3.0 [12 H, s, N(CH3)2].LM (Me2SO, 1.5 × 1024 M) 65 S cm2 mol21. [TcO(HL2)2]Cl3 2. Yield >90% (Found: C, 38.1; H, 4.7; N, 22.1. C20H30Cl3N10OTc requires C, 38.0; H, 4.8; N, 22.2%). IR (KBr): 982 [n(Tc]] O)], 1607–1690 [n(C–N–C), d(NH), n(C]] N)] and 3100–3300 cm21 [n(NH, NH2)]. NMR (Me2SO-d6): dH 10.9 (2 H, br s, C]] NH), 7.4–7.2 (20 H, m, C]] NH, CNHC, C6H5, NH2, PhC2H4NH), 3.7 (4 H, m, CH2) and 2.8 (4 H, m, CH2).LM (Me2SO, 1.2 × 1024 M) 80 S cm2 mol21. [TcO(HL3)2]Cl3 3. Yield 70% (Found: C, 37.4; H, 5.8; N, 19.7. C16H22Cl3N10OTc?3C2H5OH requires C, 37.0; H, 5.6; N, 19.6%). IR (KBr): 997 [n(Tc]] O)], 1489–1642 [n(C–N–C), d(NH), n(C]] N)] and 3171–3312 cm21 [n(NH, NH2, OH)]. NMR (Me2SO-d6): dH 11.0 (2 H, s, C]] NH), 10.0–9.8 (4 H, 2 s, C]] NH, CNHC), 8.0–7.0 (16 H, m, C6H5, PhNH, NH2), 3.45 (6 H, q, J = 7.0, CH2) and 1.06 (9 H, t, J = 7.0 Hz, CH3). LM (Me2SO, 1.3 × 1024 M) 74 S cm2 mol21.[TcO(Ln)2]Cl 4–6 (n 5 1–3). The corresponding monocationic yellow complexes were obtained following the same procedure but in the presence of base. Some drops (3–5) of a saturated solution of KOH in MeOH were added to the violet solution. The reaction mixture became yellow, it was heated at 40 8C for 10 min and concentrated in vacuo. The residue was treated with water, filtered oV, washed with EtOH and dried with Et2O. Alternatively, these compounds can be also obtained starting from TcO(HLn)2Cl3 complexes dissolved in the minimum volume of MeOH and 1 or 2 drops of KOH solution added at room temperature.Slow evaporation of the yellow solutions gave crystals of the final products. Similar products were isolated starting from [99TcO4]2. A typical preparation is as follows: to a solution of [NH4][TcO4] in hot water (30 mg, 0.166 mmol, 2 cm3) the hydrochloride salt of HL1 (55 mg, 0.33 mmol) dissolved in 0.05 M NaOH (1 cm3) was added. Sodium dithionite (60 mg, 0.345 mmol) in 1 M NaOH (2 cm3) was added and the reaction mixture heated at 80 8C for 30 min.During this time a yellow powder of [TcO(L1)2]OH was formed. It was filtered oV, washed with water, EtOH and dried with Et2O. Crystals suitable for X-ray analysis were obtained when Na[BPh4] was added to a solution of the complex in MeOH. [TcO(L1)2]Cl 4. Yield 85% (Found: C, 23.3; H, 4.9; N, 34.2. C8H20ClON10Tc requires C, 23.6; H, 5.0; N, 34.4%). IR (KBr): 976 [n(Tc]] O)], 1435, 1501, 1557, 1608 [n(C–N–C), d(NH), n(C]] N)] and 3202, 3318, 3474 cm21 [n(NH, NH2)].NMR (Me2SO-d6): dH 10.2 (2 H, s, C]] NH), 8.6 (2 H, s, C]] NH), 6.8 (4 H, br s, NH2) and 3.2 [12 H, s, N(CH3)2]. LM (Me2SO, 1.2 × 1024 M) 22 S cm2 mol21. [TcO(L2)2]Cl 5. Yield 60% (Found: C, 43.4; H, 5.1; N, 24.9. C20H28ClON10Tc requires C, 43.0; H, 5.0; N, 25.1%). IR (KBr): 986 [n(Tc]] O)], 1449–1574 [n(C–N–C), d(NH), n(C]] N)] and 3231, 3314, 3418 cm21 [n(NH, NH2)]. NMR (Me2SO-d6): dH 9.0 (2 H, br s, C]] NH), 8.8 (2 H, br s, PhC2H4NH), 7.4–7.0 (16 H, m, NH2, C6H5, C]] NH), 3.65 (4 H, t , CH2) and 2.8 (4 H, t, CH2).LM (Me2SO, 1.4 × 1024 M) 26 S cm2 mol21. [TcO(L3)2]OH 6. Yield 70% (Found: C, 40.0; H, 4.4; N, 28.7. C16H21N10O2Tc requires C, 39.7; H, 4.4; N, 28.9%). FT-IR (KBr): 970 [n(Tc]] O)], 1420–1609 [n(C–N–C), d(NH), n(C]] N)] and 2900–3400 cm21 [n(NH, NH2, OH)]. NMR (Me2SO-d6): dH 10.2–9.6 (4 H, br s, C]] NH, PhNH ) and 7.8–7.0 (16 H, m, C6H5, NH2, C]] NH).LM (Me2SO, 1.5 × 1024 M) 19 S cm2 mol21. Oxorhenium(V) complexes [ReO(HLn)2]Cl3 7–9 (n 5 1–3). A solution of ligand (0.36 mmol) in MeOH (1 cm3) was added to precursor [ReO(XPh3)2Cl3] (X = P or As; 0.18 mmol) dissolved in 40 cm3 of CH2Cl2. The reaction mixture was stirred and heated under reflux for 40 min. The violet solution was concentrated in vacuo and the residue treated with CH2Cl2. Violet solids formed upon addition of diethyl ether were filtered oV, washed with EtOH and dried with Et2O. Yields were determined on starting metal compounds.Recrystallisation from CH2Cl2–EtOH produced violet crystals. [ReO(HL1)2]Cl3 7. Yield 80% (Found: C, 16.7; H, 4.0; N, 24.3. C8H22Cl3N10ORe requires C, 17.0; H, 3.9; N, 24.7%). IR (KBr): 1007 [n(Re]] O)], 1597, 1630, 1678 [n(C–N–C), d(NH), n(C]] N)] and 3100–3300 cm21 [n(NH, NH2)]. NMR (Me2SO-d6): dH 13.0 (2 H, br s, C]] NH), 12.05 (2 H, br s, C]] NH), 11.1 (2 H, br s, CNHC), 7.7 (4 H, br s, NH2) and 3.0 [12 H, s, N(CH3)2].LM (Me2SO, 1.4 × 1024 M) 84 S cm2 mol21. [ReO(HL2)2]Cl3 8. Yield >90% (Found: C, 33.0; H, 4.1; N, 19.3. C20H30Cl3N10ORe requires C, 33.4; H, 4.2; N, 19.5%). IR (KBr): 960–990 [n(Re]] O)], 1539, 1634, 1688 [n(C–N–C), d(NH), n(C]] N)] and 3060–3300 cm21 [n(NH, NH2)]. NMR (Me2SO-d6): dH 12.0 (2 H, br s, C]] NH), 8.4, 8.2 (4 H, br s, C]] NH, CNHC), 7.5–7.1 (16 H, m, C6H5, PhC2H4NH, NH2), 4.0, 2.9 (8 H, m, CH2CH2). LM (Me2SO, 1.3 × 1024 M) 85 S cm2 mol21. [ReO(HL3)2]Cl3 9.Yield 70% (Found: C, 29.1; H, 4.1; N, 21.1. C16H22Cl3N10ORe requires C, 29.0; H, 3.4; N, 21.1%). IR (KBr): 993 [n(Re]] O)], 1570–1685 [n(C–N–C), d(NH), n(C]] N)] and 3100–3350 cm21 [n(NH, NH2)]. NMR (Me2SO-d6): dH 10.6– 10.25 (6 H, s, C]] NH, CNHC), 9.65 (2 H, br s, PhNH), 7.6, 7.3 and 7.1 (14 H, d, m, C6H5, NH2). LM (DMSO, 1.1 × 1024 M) 82 S cm2 mol21. [ReO(Ln)2]Cl 10–12 (n 5 1–3). These complexes were obtained as reported for the corresponding oxotechnetium complexes.[ReO(L1)2]Cl 10. Yield 80% (Found: C, 21.8; H, 5.0; N, 25.4. C8H20ClN10ORe?CH3OH requires C, 21.5; H, 5.1; N, 25.1%). IR (KBr): 993 [n(Re]] O)], 1437–1615 [n(CNC), d(NH), n(C]] N)] and 3204, 3319, 3462 cm21 [n(NH, NH2, OH)]. NMR (Me2SO-d6): dH 11.1 (2 H, s, C]] NH), 9.8 (2 H, s, C]] NH), 7.1 (4 H, br s, NH2), 4.25 (1 H, q, J = 5.2, OH), 3.2 (3 H, d, J = 5.2 Hz, CH3) and 3.0 [12 H, s , N(CH3)2]. LM (Me2SO, 1.2 × 1024 M) 24 S cm2 mol21. [ReO(L2)2]Cl 11. Yield <50% (Found: C, 37.4; H, 4.4; N, 21.5.C20H28ClN10ORe requires C, 37.2; H, 4.4; N, 21.7%). IR (KBr): 997 [n(Re]] O)], 1450–1595 [n(C–N–C), d(NH), n(C]] N)] and 3227, 3310, 3416 cm21 [n(NH, NH2)]. NMR (Me2SO-d6): dH 10.2 (2 H, br s, C]] NH), 10.0 (2 H, br s, PhC2H4NH), 7.4–7.1 (16 H, m, C6H5, C]] NH, NH2), 3.45 (4 H, m, CH2) and 2.8 (4 H, m, CH2). LM (Me2SO, 1.3 × 1024 M) 29 S cm2 mol21. [ReO(L3)2][ReO4] 12. Yield 40% (Found: C, 23.9; H, 2.7; N, 17.1. C16H20N10O5Re2 requires C, 24.0; H, 2.5; N, 17.4%).IR (KBr): 910 [n(ReO4)], 966 [n(Re]] O)], 1423–1640 [n(C–N–C), d(NH), n(C]] N)] and 3285, 3420 cm21 [n(NH, NH2)]. NMR (Me2SO-d6): dH 10.5–10.4 (4 H, s, C]] NH), 9.8 (2 H, br s, PhNH) and 7.8–7.0 (14 H, m, C6H5, NH2). LM (Me2SO, 1.4 × 1024 M) 30 S cm2 mol21. Nitrido-complexes of technetium(V) [TcN(HLn)2(H2O)]Cl2 13–15 (n 5 1–3). The pink compound [TcN(PPh3)2Cl2] (100 mg, 0.14 mmol) in CH2Cl2 (40 cm3) was heated and stirred until all the solid dissolved.A solution of ligand (0.28 mmol, MeOH 1 cm3) was added and the reaction mixture heated under reflux. Addition of some drops of NEt3 (it was not necessary for HL3) produced a change from pink to bright yellow. After 30 min the heating was turned oV, the solution concentrated under reduced pressure and the residue taken up in CH2Cl2. The NEt3?HCl salt was filtered oV and washed with CH2Cl2 (2 × 5 cm3). To the combined organic solutions EtOH (5 cm3) was added. Slow evaporation of solvent provided yellow crystals of the desired product.It was washed with ethanol and diethyl ether and recrystallised twice from dichloromethane–ethanol. Yields are based on starting technetium complex. [TcN(HL1)2(H2O)]Cl2 13. Yield 85% (Found: C, 20.7; H, 5.2; N, 33.8. C8H24Cl2N11OTc requires C, 20.85; H, 5.25; N, 33.5%).1942 J. Chem. Soc., Dalton Trans., 1999, 1937–1943 IR (KBr): 1088 [n(Tc]] ] N)], 1497, 1632, 1668 [n(C–N–C), d(NH), n(C]] N)] and 3173–3337 cm21 [n(NH, NH2, OH)].NMR (Me2SO-d6): dH 9.65 (2 H, s, CNHC), 7.75 (4 H, br s, NH2), 7.3, 7.2 (4 H, s, C]] NH), 3.35 (2 H, s, H2O) and 3.2 [12 H, s, N(CH3)2]. LM (Me2SO, 1.4 × 1024 M) 54 S cm2 mol21. [TcN(HL2)2(H2O)]Cl2 14. Yield 90% (Found: C, 39.5; H, 5.2; N, 25.3. C20H32Cl2N11OTc requires C, 39.3; H, 5.30; N, 25.2%). IR (KBr): 1072 [n(Tc]] ] N)], 1531, 1580, 1682 [n(C–N–C), d(NH), n(C]] N)] and 3200–3400 cm21 [n(NH, NH2, OH)]. NMR (Me2SO-d6): dH 10.4 (2 H, br s, CNHC), 7.6–7.0 (20 H, m, NH2, C6H5, C]] NH, PhC2H4NH), 3.6 (4 H, t, CH2), 3.35 (2 H, s, H2O) and 2.85 (4 H, t, CH2).LM (Me2SO, 1.4 × 1024 M) 64 S cm2 mol21. [TcN(HL3)2(H2O)]Cl2 15. Yield 65% (Found: C, 34.6; H, 4.25; N, 27.6. C16H24Cl2N11OTc requires C, 34.5; H, 4.35; N, 27.7%). IR (KBr): 1063 [n(Tc]] ] N)], 1516–1655 [n(C–N–C), d(NH), n(C]] N)] and 3020–3470 cm21 [n(NH, NH2, OH)]. NMR (Me2SO-d6): dH 9.45 (2 H, s, CNHC), 7.4–7.0 (20 H, 2m, NH2, C6H5, C]] NH, PhNH) and 3.35 (2 H, s, H2O).LM (Me2SO, 1.2 × 1024 M): 46 S cm2 mol21. [TcN(Ln)2] 16–19 (n 5 1–3). These compounds were isolated following the procedure described for the analogous oxocomplexes. [TcN(L1)2] 16. Yield 90% (Found: C, 24.5; H, 6.6; N, 35.0. C8H20N11Tc?CH3OH?2H2O requires C, 24.7; H, 6.5; N, 35.2%). IR (KBr): 1059 [n(Tc]] ] N)], 1450–1616 [n(C–N–C), d(NH), n(C]] N)] and 3181, 3299, 3461 cm21 [n(NH, NH2, OH)]. NMR (Me2SO-d6): dH 5.95 (2 H, s, C]] NH), 5.6 (2 H, s, C]] NH), 5.45 (4 H, s, NH2), 4.25 (1 H, q, J = 5.2 Hz, OH), 3.35 (7 H, br s, CH3, H2O) and 3.0 [12 H, s, N(CH3)2].[TcN(L2)2] 17. Yield 90% (Found: C, 46.1; H, 5.5; N, 29.2. C20H28N11Tc requires C, 46.0; H, 5.4; N, 29.5%). IR (KBr): 1067 [n(Tc]] ] N)], 1450–1640 [n(C–N–C), d(NH), n(C]] N)] and 3197, 3310, 3407 cm21 [n(NH, NH2)]. NMR (Me2SO-d6): dH 7.3–7.1 (10 H, m, C6H5), 6.2–5.4 (10 H, m, PhC2H4NH, C]] NH, NH2), 2.8 (4 H, t, CH2) and 2.5 (4 H, t, CH2). [TcN(L3)2 ] 18. Yield 65% (Found: C, 40.9; H, 5.3; N, 29.4.C16H20N11Tc?2CH3OH: C, 40.8; H, 5.3; N, 29.1%). IR (KBr): 1072 [n(Tc]] ] N)], 1480–1640 [n(C–N–C), d(NH), n(C]] N)] and 3150–3312 cm21 [n(NH, NH2 , OH)]. NMR (Me2SO-d6): dH 7.6– 6.6 (20 H, 4m, NH2, C6H5, C]] NH, PhNH), 4.25 (2 H, q, J = 5.2, OH) and 3.2 (6 H, d, J = 5.2 Hz, CH3). Imido-complexes of ReV [Re(NMe)(HL1,2)(PPh3)Cl]Cl2 19, 20. To a solution of the precursor [Re(NCH3)(PPh3)2Cl3] (0.1g, 0.118 mmol) in CH2Cl2 (50 cm3) ligand dissolved in the minimum volume of MeOH and in a 1: 2 stoichiometric ratio was added.The reaction mixture was stirred and heated under reflux for 30 min. During this time a pink solid was formed. It was filtered oV, washed with CH2Cl2, EtOH and dried with Et2O. These complexes were recrystallised by slow evaporation of MeOH solutions. Yields are based on the starting rhenium complex. [Re(NMe)(HL1)(PPh3)Cl]Cl2 19. Yield 70% (Found: C, 38.3; H, 4.2; N, 11.9. C23H29Cl3N6PRe requires C, 38.7; H, 4.1; N, 11.8%).IR (KBr): 1094 [n(PPh3)], 1435–1680 [n(C–N–C), d(NH), n(C]] N)] and 3000, 3233, 3365 cm21 [n(NH, NH2)]. NMR (Me2SO-d6): dH 10.65 (1 H, s, C]] NH), 9.5 (1 H, s, C]] NH), 8.0–7.0 (18 H, m, PPh3, CNHC, NH2), 2.75 [6 H, s, N(CH3)2] and 2.5 [3 H, s, Re(NCH3)]. dP 28.95. LM (Me2SO, 1.15 × 1024 M) 77 S cm2 mol21. [Re(NMe)(HL2)(PPh3)Cl]Cl2 20. Yield >90% (Found: C, 44.4; H, 4.2; N, 10.7. C29H33Cl3N6PRe requires C, 44.1; H, 4.2; N, 10.6%). IR (KBr): 1096 [n(PPh3)], 1435, 1524, 1663 [n(C–N– C), d(NH), n(C]] N)] and 3206, 3335, 3416 cm21 [n(NH, NH2)].NMR (Me2SO-d6): dH 10.95 (1 H, br s, C]] NH), 9.8–8.6 (3 H, s, CNHC, C]] NH, PhC2H4NH), 8.0–7.0 (22 H, m, C6H5, PPh3, NH2), 2.5 [3 H, s, Re(NCH3)], 2.25, 1.8 (4 H, m, CH2CH2). dP 26.38. LM (Me2SO, 1.0 × 1024 M) 66 S cm2 mol21. [Re(NMe)(L1,3)2]Cl 21, 22. These complexes were obtained following the procedure previously described but in the presence of NEt3. When the pink solid was formed 10 drops of base were added.The mixture was heated until the solid disappeared and the solution became clear and yellow (ca. 1 h). The solution was concentrated to dryness and the residue taken up in CH2Cl2 and EtOH. Slow evaporation of solvent gave a yellow ochre powder. The complexes were recrystallised from MeOH solutions. Yields were determined based on the starting metal precursor. [Re(NMe)(L1)2]Cl 21. Yield 80% (Found: C, 21.3; H, 4.6; N, 29.9. C9H23ClN11Re requires C, 21.3; H, 4.6; N, 30.4%).IR (KBr): 1505, 1559, 1611 [n(C–N–C), d(NH), n(C]] N)], 3212, 3318, 3447 cm21 [n(NH, NH2)]. NMR (Me2SO-d6): dH 11.3, 10.25, 9.9, 9.1 (4 H, s, C]] NH), 7.0 (2 H, br s, NH2), 6.4 (2 H, br s, NH2), 3.2, 3.15 [12 H, s, N(CH3)2] and 2.5 [3 H, s, Re(NCH3)]. LM (Me2SO, 1.4 × 1024 M) 33 S cm2 mol21. [Re(NMe)(L3)2]Cl 22. Yield 80% (Found: C, 32.5; H, 4.3; N, 24.6. C17H23ClN11Re?H2O requires C, 32.9; H, 4.1; N, 24.8%). IR (KBr): 1480, 1537, 1645 [n(C–N–C), d(NH), n(C]] N)] and 3100–3400 cm21 [n(NH, NH2, OH)].NMR (Me2SO-d6): dH 10.6–9.4 (6 H, br s, PhNH, C]] NH), 7.8–7.0 (14 H, m, C6H5, NH2), 3.35 (2 H, s, H2O) and 2.5 [3 H, s, Re(NCH3)]. LM (Me2SO, 1.2 × 1024 M) 45 S cm2 mol21. Crystallography Crystal data. [TcO(C4H10N5)2]1[B(C6H5)4]2?CH3OH 4, M = 722.49, monoclinic, space group P21/c (no. 14), a = 11.589(2), b = 15.918(2), c = 18.962(4) Å, b = 96.97(1)8, U = 3472(1) Å3 (by least-squares refinement on diVractometer angles for 25 automatically centred reflections, l = 0.71069 Å), Z = 4, Dc = 1.38 g cm23, m = 4.60 cm21, F(000) = 1504, crystal dimensions 0.38 × 0.41 × 0.45 mm.[TcN(C4H11N5)2(H2O)]212Cl2 13, M = 460.16, monoclinic, space group C2/c (no. 15), a = 19.620(3), b = 7.576(1), c = 25.074(3) Å, b = 102.40(1)8, U = 3640.1(9) Å3 (by least-squares refinement on diVractometer angles for 25 automatically centred reflections, l = 0.71069 Å), Z = 8, Dc = 1.68 g cm23, m = 11.05 cm21, F(000) = 1872, crystal dimensions 0.18 × 0.40 × 0.48 mm.Data collection and processing. CAD-4 diVractometer, w–2q scan mode, graphite-monochromated Mo-K radiation, T = 295 K. Compound 4: 7561 unique reflections measured (2 < q < 28) giving 6172 with I > 3s(I ), corrected for Lorentzpolarisation and absorption (Y scan method, minimum transmission factor 0.86) eVects. Compound 13: 4367 unique reflections measured (2 < q <28) giving 3918 with I >3s(I), corrected as for 4 (minimum transmission factor 0.87).Structure analysis and refinement. Solution by Patterson and Fourier methods. For compound 4, full-matrix least-squares refinement with all non-hydrogen atom anisotropic and hydrogen isotropic, except those of methyl groups which were placed at fixed calculated positions. The Tc and O(1) atoms were disordered and refined over two positions, with occupancies 0.8 and 0.2 respectively, over and under the plane formed by N(1), N(2), N(6) and N(7) atoms. Final R = 0.042 and R9 = 0.062.Goodness of fit = 2.23. Final diVerence map peaks in the range ± 0.43 e Å23. For compound 13, full-matrix least-squares refinement on F with all non-hydrogen atoms anisotropic and hydrogens isotropic. Final R = 0.021 and R9 = 0.027. Goodness of fit = 2.34. Final diVerence map peaks in the range ±0.14 e Å23. Programs used and source of scattering factors are given in ref. 29 and the structures were drawn using ORTEP.15 CCDC reference number 186/1435. See http://www.rsc.org/suppdata/dt/1999/1937/ for crystallographic files in .cif format.J.Chem. Soc., Dalton Trans., 1999, 1937–1943 1943 Acknowledgements This work was supported by Italian MURST in the frame of the project “Pharmacological and Diagnostic Properties of Metal Complexes” (co-ordinator Professor G. Natile). We are grateful to Professor G. Annibale for obtaining and interpreting UV spectra and Dr E. Cavallari for preparing the complexes. We thank Mr M. Fratta for the elemental analyses and technical assitance, Mr P.Formaglio for recording NMR spectra. References 1 (a) C. R. Saha, J. Inorg. Nucl. Chem., 1976, 38, 1635; (b) D. Sen, J. Chem. Soc. A, 1969, 2900. 2 R. Rathke, Ber. Bunsenges. Phys. Chem., 1879, 12, 779; F. Emich, Monatsh. Chem., 1883, 4, 409. 3 P. Ray, Chem. Rev., 1961, 61, 313. 4 S. Roychowdhury, M. K. Sipani and B. Sur, J. Indian Chem. Soc., 1988, 65, 718. 5 (a) L. Fabbrizzi, M. Michelon, P. Paoletti and G. Schwarzenbach, J. Am.Chem. Soc., 1977, 5574; (b) A. A. Pinkerton and D. Schwarzenbach, J. Chem. Soc., Dalton Trans., 1978, 989. 6 R. K. Ray, Polyhedron, 1989, 8, 7; R. K. Ray and G. B. KauVman, Inorg. Chim. Acta, 1990, 274, 237. 7 S. L. Shapiro, V. A. Parrino, E. Rogow and L. Freedman, J. Am. Chem. Soc., 1959, 81, 3725; S. L. Shapiro, V. A. Parrino and L. Freedman, J. Am. Chem. Soc., 1959, 81, 2220, 3728; C. R. Sirtori and C. Pasik, Pharmacol. Res., 1994, 30, 187. 8 W. M. Watkins, J. D. Chulay, D.G. Sixsmith, H. C. Spencer and R. E. Howells, J. Pharm. Pharmacol., 1987, 39, 261. 9 P. Morain, C. Abraham, B. Portevin and G. De Nanteuil, Mol. Pharmacol., 1994, 46, 732. 10 M. Nicolini, G. Bandoli and U. Mazzi (Editors), Technetium and Rhenium in Chemistry and Nuclear Medicine 3, Cortina International Verona, Raven Press, New York, 1990. 11 S. R. Ernst and F. W. Cagle, Jr., Acta Crystallogr., Sect. B, 1977, 33, 235; C. J. Brown and L. Sengier, Acta Crystallogr., Sect. C, 1984, 40, 1294; M.Hriharan, S. S. Rajan and R. Srinivasan, Acta Crystallogr., Sect. C, 1989, 45, 911; S. R. Ernst, Acta Crystallogr., Sect. B, 1977, 33, 237. 12 (a) P. V. Babykutty, C. P. Prabhakaran, R. Anantaraman and C. G. R. Nair, J. Inorg. Nucl. Chem., 1974, 36, 3685; (b) N. C. Ta and D. Sen, J. Inorg. Nucl. Chem., 1981, 43, 209; (c) O. C. Hart, S. G. Bott, J. L. Atwood and S. R. Cooper, J. Chem. Soc., Chem Commun., 1992, 894. 13 (a) M. Cattabriga, A. Marchi, L. Marvelli, R.Rossi, G. Vertuani, R. Pecoraro, A. Scatturin, V. Bertolasi and V. Ferretti, J. Chem. Soc., Dalton Trans., 1998, 1453; (b) A. Marchi, L. Uccelli, L. Marvelli, R. Rossi, M. Giganti, V. Bertolasi and V. Ferretti, J. Chem. Soc., Dalton Trans., 1996, 3105. 14 B. L. Haymore and G. V. Goeden, Inorg. Chem., 1983, 22, 157; G. K. Lahiri, S. Goswami, L. R. Falvello and A. Chakravorty, Inorg. Chem., 1987, 26, 3365. 15 C. K. Johnson, ORTEP II, Report ORNL-5138, Oak Ridge National Laboratory, Oak Ridge, TN, 1976. 16 A. Marchi, L. Marvelli, R. Rossi, L. Magon, V. Bertolasi, V. Ferretti and P. Gilli, J.Chem. Soc., Dalton Trans., 1992, 1485; N. Bryson, J. C. Dewan, J. Lester-James, A. G. Jones and A. Davison, Inorg. Chem., 1988, 27, 2154; T. N. Rao, D. Adhikesavalu, A. Camerman and A. R. Fritzberg, J. Am. Chem. Soc., 1990, 112, 5798; A. Marchi, R. Rossi, L. Magon, A. Duatti, R. Pasqualini, V. Ferretti and V. Bertolasi, J. Chem. Soc., Dalton Trans., 1990, 1411. 17 A.Marchi, A. Duatti, R. Rossi, L. Magon, R.Pasqualini, V. Bertolasi, V. Ferretti and G. Gilli, J. Chem. Soc., Dalton Trans., 1988, 1743; F. Tisato, U. Mazzi, G. Bandoli, G. Cros, M.-H. Darbieu, Y. Coulais and R. Guiraud, J. Chem. Soc., Dalton Trans., 1991, 1301; A. Marchi, R. Rossi, L. Marvelli and V. Bertolasi, Inorg. Chem., 1993, 32, 4673; F. Tisato, F. Refosco and G. Bandoli, Coord. Chem. Rev., 1994, 135/136, 325 and refs. therein. 18 J. Baldas, S. F. Colmanet and G. A. Williams, Inorg. Chim. Acta, 1991, 179, 189; A. Marchi, R. Rossi, L. Magon, A. Duatti, U. Casellato, R. Graziani, M. Vidal and F. Riche, J. Chem. Soc., Dalton Trans., 1990, 1935; V. Bertolasi, V. Ferretti, P. Gilli, A. Marchi and L. Marvelli, Acta Crystallogr., Sect. C, 1991, 47, 2535; Y. Kani, T. Takayama, S. Inomata, T. Sekine and H. Kudo, Chem. Lett., 1995, 1059. 19 A. Marchi, P. Garuti, A. Duatti, L. Magon, R. Rossi, V. Ferretti and V. Bertolasi, Inorg. Chem., 1990, 29, 2097; S. Jurisson, E. O. Schlemper, D. E. Troutner, L. R. Canning, D. P. Nowotnik and R. D. Neirinckx, Inorg. Chem., 1986, 25, 543; R. Faggiani, C. J. L. Lock, L. A. Epps, A. V. Kramer and H. D. Brune, Acta Crystallogr., Sect. C, 1990, 46, 2324; M. R. A. Pillai, C. S. John, J. M. Lo, E. O. Schlemper and D. E. Troutner, Inorg. Chem., 1990, 29, 1850. 20 T. C. Creitz, R. Gsell and D. L. Wampler, Chem Commun., 1969, 1371. 21 K. Chakrabarty, T. Kar and S. P. Sen Gupta, Acta Crystallogr., Sect. C, 1990, 46, 2065. 22 M. R. Snow, Acta Crystallogr., Sect. B, 1974, 30, 1850; D. Sen and S. Guha, J. Chem. Soc., Dalton Trans., 1975, 1701; C. H. L. Kennard, G. Smith and E. J. O’Reilly, Inorg. Chim. Acta, 1983, 77, L113 23 M. Neves, L. Gano, M. J. Ribeiro, A. C. Santos, A. Marchi, C. S. Dimopolou and J. J. Pedroso de Lima, Nucl. Med. Biol., 1998, 26, 79. 24 F. A. Cotton, A. Davison, V. W. W. Day, L. D. Gage and H. S. Trop, Inorg. Chem., 1979, 18, 3024; A. Davison, C. Orvig, H. S. Trop, M. Shon, B. DePamphilis and A. G. Jones, Inorg. Chem., 1980, 19, 1988; R. W. Thomas, M. J. Heeg, R. C. Helder and E. Deutsch, Inorg. Chem., 1985, 24, 1472. 25 J. Baldas, J. F. Boas, J. Bonnyman and G. A. Williams, J. Chem. Soc., Dalton Trans., 1984, 2395; J. Baldas, J. Bonnyman and G. A. Williams, Inorg. Chem., 1986, 25, 150. 26 D. Michos, X. L. Luo, J. A. K. Howard and R. H. Crabtree, Inorg. Chem., 1982, 31, 3914; J. Chatt and G. A. Rowe, J. Chem. Soc., 1962, 4019. 27 J. Chatt, R. J. Dosser, F. King and G. J. Leigh, J. Chem. Soc., Dalton Trans., 1976, 2435. 28 D. Karipides and W. C. Fernelius, Inorg. Synth., 1963, 7, 56. 29 MOLEN, An Interactive Structure Solution Procedure, Enraf- Nonius, Delft, 1990; M. Nardelli, Comput. Chem., 1983, 7, 95; D. T. Cromer and J. T. Waber, International Tables for X-Ray Crystallography, Kynoch Press, Birmingham, 1974, vol. 4. Paper 9/00798I

ISSN:1477-9226    

DOI:10.1039/a900798i

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1998, Pages 1939–1940 1939 Coupling reaction of alkyl cyanide (RCN, R 5 Me or Et) with 7-azaindole on a hexaosmium carbonyl cluster core; molecular structure of [Os6(CO)14(Ï-CO)(Ï-H)(Ï-Á1 :Á2-C9H8N3)] Kelvin Sze-Yin Leung and Wing-Tak Wong *,† Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong, P. R. China Treatment of [Os6(CO)16(NCR)2] (R = Me or Et) with 7-azaindole resulted in the formation of [Os6(CO)14(m-CO)- (m-H)(m-h1 :h2-C8H5N3)(R)] involving coupling of the alkyl cyanide and 7-azaindole.The interaction of two organic fragments bound to the metal cluster core to give a larger and more complex molecular fragment is of basic scientific interest and has potential industrial applications.1 We are currently interested in the study of transition-metal cluster assisted coupling of organic molecules and have recently observed some ruthenium clusters with a coordinated phenoxazinone-like ligand that arose from a ‘quinone–imine or –nitrene’ intermediate via the reductive deoxygenation of the quinone–oxime by the transition-metal carbonyl cluster.2 As part of our continuing investigations, we have studied the interaction of 7-azaindole with the hexaosmium cluster [Os6(CO)16(NCMe)2] and observed that a novel coupling between the co-ordinated acetonitrile ligand and 7-azaindole gave a metallaheterocycle involving osmium metal.Reaction of 1 equivalent of 7-azaindole with the preformed labile bis(acetonitrile)hexaosmium carbonyl cluster [Os6(CO)16- (NCMe)2],3 in CH2Cl2, gave [Os6(CO)14(m-CO)(m-H)(m-h1 :h2- C9H8N3)] 1.‡ The stoichiometry of 1 was initially established by FAB-MS and 1H NMR spectroscopic techniques.§ Single crystals of 1 suitable for X-ray analysis ¶ were obtained from slow evaporation of a toluene–CHCl3 solution at room temperature for 2 d.A perspective drawing of cluster 1 together with some selected bond parameters is shown in Fig. 1. This analysis revealed that complex 1 contains a bicapped-tetrahedron metal core identical to the parent compound Os6(CO)18.5 However, the co-ordinated 7-azaindole ligand was found to couple with a co-ordinated acetonitrile to form three fused rings involving osmium metal [Os(6)]. Such a ring system is nearly planar with a maximum deviation of 0.30 Å. The 7-azaindole also underwent orthometallation and co-ordinated to Os(5), which is a very common observation for pyridine-containing osmium † E-Mail: wtwong@hkucc.hku.hk ‡ Treatment of 7-azaindole (7.1 mg) with [Os6(CO)16(NCMe)2] (100 mg, 0.06 mmol) in CH2Cl2 (25 cm3) under ambient conditions over a period of 24 h aVorded a deep brown reaction mixture.Purification by TLC on silica Merck Kieselgel 60 GF254 (hexane–CH2Cl2, 1 : 3) gave the brown air-stable cluster 1 (35%) together with two uncharacterized products in low yields. Deprotonation of 1 (10 mg) with a slight excess of dbu was carried out in CH2Cl2 (10 cm3) at room temperature.Proton NMR monitoring indicated that the deprotonation to give 2 was complete within 10 min. The subsequent reprotonation of 2 to give 1 was achieved by the addition of excess trifluoroacetic acid (0.2 cm3). Carbonylation of 1 (20 mg) was carried out in CH2Cl2 (30 cm3) at room temperature for 4 h to give the light brown cluster 3. Due to the instability of 3 in solution no accurate yield could be determined. A similar synthetic methodology to 1 was used for the preparation of 4 with EtCN instead of MeCN (yield 30%).clusters. Recently we also reported the reaction of 7-azaindole with [Os3(CO)10(NCMe)2] to give a major product [Os3(m-H)- (CO)9(m-C7H5N2)] containing an orthometallated ligand.6 All the carbonyl ligands were terminally bonded except a bridging CO across the Os(3)]Os(6) edge. This Os]Os edge is found to be significantly shorter than other Os]Os bonds in 1 which might probably be due to the ‘clamping’ eVect of the bridging CO.The hydride and the imine hydrogen, as evident from 1H NMR, could not be located directly by X-ray analysis. However, potential-energy calculations 7 suggested that the hydride bridges Os(4)]Os(5). This is also consistent with the observed long Os(4)]Os(5) distance compared with other Os]Os distances in the structure.8 The imino hydrogen was found to undergo dissociation in the presence of a strong base such as 1,8-diazabicyclo[5.4.0]undec-7-ene (dbu) so that a cluster anion [Os6(CO)14(m-CO)(m-H)(m-h1 :h2-C9H7N3)]2 2 resulted.However, the hydride ligand does not undergo dissociation in § Spectroscopic data: complex 1. IR (CH2Cl2, cm21) 2086m, 2055s, 2022s, 2012vs, 1956w [n(CO)]. Positive-ion FAB mass spectrum: m/z 1720 (Calc. 1720). 1H NMR (CD2Cl2): d 214.33 (s, 1 H, metal hydride), 1.26 (s, 3 H, methyl), 6.75 [dd, 1 H, H1, J(H1,2) 7.8, J(H1,3) 2.0], 7.26 [dd, 1 H, H4, J(H4,3) 7.7, J(H4,2) 1.6], 7.46 [ddd, 1 H, H2, J(H2,1) 7.8, J(H2,3) 4.3, J(H2,4) 1.6], 7.82 [ddd, 1 H, H3, J(H3,4) 7.7, J(H3,2) 4.3, J(H3,1) 2.0 Hz], 8.69 (s br, 1 H, NH) (Found: C, 18.93; H, 0.54; N, 2.44.Calc. for C24H9N3O15Os6?0.5C7H8: C, 18.68; H, 0.74; N, 2.38%). Complex 2. 1H NMR (CD2Cl2): d 214.58 (s, 1 H, metal hydride), 1.26 (s, 3 H, methyl), 6.75 [dd, 1 H, H1, J(H1,2) 7.7, J(H1,3) 2.0], 7.30 [dd, 1 H, H4, J(H4,3) 7.5, J(H4.2) 1.8], 7.52 [ddd, 1 H, H2, J(H2,1) 7.7, J(H2,3) 4.3, J(H2,4) 1.8], 7.82 [ddd, 1 H, H3, J(H3,4) 7.5, J(H3,2) 4.3, J(H3,1) 2.0 Hz].Complex 3. IR (CH2Cl2, cm21) 2019s, 1992vs, 1967s [n(CO)]. Positive-ion FAB mass spectrum: m/z 1749 (Calc. 1748). 1H NMR (CD2Cl2): d 214.46 (s, 1 H, metal hydride), 1.25 (s, 3 H, methyl), 6.50 [dd, 1 H, H1, J(H1,2) 7.8, J(H1,3) 1.9], 7.22 (dd, 1 H, H4, J(H4,3) 7.5, J(H4,2) 1.7], 7.46 [ddd, 1 H, H2, J(H2,1) 7.8, J(H2,3) 4.2, J(H2,4) 1.7], 7.95 [ddd, 1 H, H3, J(H3,4) 7.5, J(H3,2) 4.2, J(H3,1) 1.9 Hz], 11.27 (s br, 1 H, NH).Complex 4. IR (CH2Cl2, cm21) 2085m, 2053s, 2022s, 2012vs, 1950w [n(CO)]. Positive-ion FAB mass spectrum: m/z 1734 (Calc. 1733). 1H NMR (CD2Cl2): d 215.13 (s, 1 H, metal hydride), 1.15 (t, 3 H, J 7.3, methyl), 1.41 (q, 2 H, J 7.3, methylene), 7.32 [dd, 1 H, H1, J(H1,2) 7.9, J(H1,3) 1.9], 7.48 [dd, 1 H, H4, J(H4,3) 7.7, J(H4,2) 1.8], 7.82 [ddd, 1 H, H2, J(H2,1) 7.9, J(H2,3) 4.4, J(H2,4) 1.8], 8.23 [ddd, 1 H, H3, J(H3,4) 7.7, J(H3,2) 4.4, J(H3,1) 1.9 Hz], 8.67 (s, br, 1 H, NH) (Found: C, 18.73; H, 0.79; N, 2.42.Calc. for C25H11N3O15Os6: C, 18.89; H, 0.83; N, 2.32%). ¶ Crystal data: C24H9N3O15Os6?0.5C7H8 1, M = 1766.62, primitive monoclinic, space group P21/n (no. 14, non-standard setting of P21/c), a = 10.223(1), b = 28.137(2), c = 12.357(1) Å, b = 97.70(1)8, U = 3522.4(5) Å3, Z = 4, Dc = 3.331 g cm23, T = 298 K, F(000) = 3100, Mo-Ka radiation (l = 0.710 73 Å), m(Mo-Ka) = 216.17 cm21, dimensions 0.12 × 0.12 × 0.18 mm, 4002 observed diVractometer data [I > 1.0s(I )].The structure was solved by direct methods (SIR 88) 4 and Fourier-diVerence techniques, refined by full-matrix least-squares analysis on F to R = 0.074, R9 = 0.073, w = 1/s2(Fo). A disordered toluene solvate was found and located on a centre of inversion. Therefore, the methyl group [C(28)] on the toluene molecule was assigned an occupancy factor of 0.5. Refinement with this model led to reasonable thermal parameters for this molecule. CCDC reference number 186/997.1940 J. Chem.Soc., Dalton Trans., 1998, Pages 1939–1940 the presence of excess dbu. The reaction was reversible as 2 converted to 1 quantitatively with addition of CF3CO2H, see Scheme 1. Cluster 1 also reacted with CO at room temperature to give an unstable compound with a molecular formula of [Os6(CO)16H(C9H8N3)] 3. However, attempts to obtain single crystals for X-ray analysis have met with little success. Cluster 3 was unstable in solution and reverted back to 2 even when being kept in the CO atmosphere.The coupling reaction of 7-azaindole with the co-ordinated cyanides is also applicable for ethyl cyanide. The analogous compound [Os6(CO)14(m-CO)(m-H)(C10H10N3)] 4 was isolated as the major product (30%) and characterized by solution spectroscopic methods § and is believed to have a similar structure to 1. However, extension of this work to phenyl cyanide is hampered by the poor stability of the precursor complex [Os6(CO)16(NCPh)2]. Interaction of co-ordinated cyanide ligands with other organic ligands on the co-ordination sphere of the cluster core is rather rare.Previously it was believed that the cyanide ligands, in particular MeCN, were good leaving groups and serve as labile substituents for substitution chemistry of transition-metal clusters. Although recent work indicates that the co-ordinated acetonitrile is not necessarily displaceable in the higher nuclearity systems such as [Os6(CO)15H- (MeCN)(C5H5N)(C5H4N)],9 [Os6(CO)20(m4-S)(MeCN)] 10 and [Os6Pt(CO)17H(m3-NCMe)(C8H12)].11 Acknowledgements We gratefully acknowledge financial support from the Hong Kong Research Grants Council and the University of Hong Kong.K. S.-Y. L. acknowledges the receipt of a postgraduate Fig. 1 Molecular structure of [Os6(CO)14(m-CO)(m-H)(C9H8N3)] 1 showing the atomic numbering scheme. Selected bond lengths (Å) and angles (8): Os(1)]Os(2) 2.764(2), Os(1)]Os(3) 2.732(2), Os(1)]Os(5) 2.877(2), Os(2)]Os(3) 2.717(1), Os(2)]Os(5) 2.889(2), Os(3)]Os(5) 2.793(2), Os(2)]Os(4) 2.824(2), Os(3)]Os(4) 2.827(2), Os(4)]Os(5) 2.903(1), Os(3)]Os(6) 2.598(2), Os(4)]Os(6) 2.927(2), Os(5)]Os(6) 2.820(1), Os(5)]C(16) 2.11(3), Os(6)]N(1) 2.08(2), Os(6)]N(3) 2.11(2), N(3)]C(23) 1.32(3), N(2)]C(23) 1.35(3), N(2)]C(20) 1.39(4), N(1)] C(20) 1.36(3); Os(6)]N(3)]C(23) 129(1), N(3)]C(23)]N(2) 124(2), C(23)]N(2)]C(20) 124(2), N(2)]C(20)]N(1) 127(2), C(20)]N(1)]Os(6) 124(1), N(1)]Os(6)]N(3) 85.4(8) studentship and a scholarship, administered by the University of Hong Kong and the Epson Foundation respectively.References 1 D. F. Shriver, H. D. Kaesz and R. D. Adams, The Chemistry of Metal Cluster Complexes, VCH, New York, 1992. 2 K. K.-H. Lee and W.-T. Wong, J. Chem. Soc., Dalton Trans., 1997, 2987. 3 B. F. G. Johnson, R. A. Kamarudin, F. J. Lahoz, J. Lewis and P. R. Raithby, J. Chem. Soc., Dalton Trans., 1988, 1205. 4 M. C. Burla, M. Camalli, G. Cascarano, C. Giacovazzo, G. Polidori, R. Spagna and D. Viterbo, J. Appl. Crystallogr., 1989, 22, 389. 5 C. R. Eady, B. F. G. Johnson and J. Lewis, J. Chem. Soc., Dalton Trans., 1975, 2606; A. J. Blake, B. F. G. Johnson and J. G. M. Nairn, Acta Crystallogr., Sect. C, 1994, 50, 1052. 6 F.-S. Kong and W.-T. Wong, J. Chem. Soc., Dalton Trans., 1997, 1237. 7 A. G. Orpen, J. Chem. Soc., Dalton Trans., 1980, 2509. 8 A. P. Humphries and H. D. Kaesz, Prog. Inorg. Chem., 1979, 2, 145. 9 K. S.-Y. Leung and W.-T. Wong, J. Chem. Soc., Dalton Trans., 1997, 4357. 10 S.-M. Lee, K.-K. Cheung and W.-T. Wong, J. Organomet. Chem., 1995, 503, C19. 11 C. Couture and D. H. Farrar, J. Chem. Soc., Dalton Trans., 1987, 2245. Received 20th February 1998; Communication 8/02325E Scheme 1 Os Os Os Os CO H Os N N N Os 4 3 2 1 2 Os Os Os Os CO H Os N N N Os 4 3 2 1 1 H – CF3CO2H dbu +CO –CO [Os6(CO)16H(C9H8N3)] 3

ISSN:1477-9226    

DOI:10.1039/a802325e

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1998, Pages 1941–1942 1941 Synthesis and structure of a co-ordination polymer based on silver(I) triangles linked by isonicotinate anions Andrew D. Burrows,* Mary F. Mahon and Mark T. Palmer Department of Chemistry, University of Bath, Claverton Down, Bath, UK BA2 7AY Reaction of AgBF4 with isonicotinic acid (NC5H4CO2H-4) led to the formation of an unusual polymeric structure consisting of Ag3 triangles linked together by two isonicotinate ligands: this co-ordination polymer, containing both bridged and unbridged short Ag ? ? ? Ag contacts has been characterised crystallographically. There is currently considerable interest in exploiting both co-ordinative bonds1 and hydrogen bonds 2,3 to facilitate the crystal engineering of structures based on metal complexes.We are interested in systems that are capable of self-assembly using both types of interaction 4 and as part of this programme we have been studying isonicotinic acid HL (NC5H4CO2H-4), which is capable of co-ordinative bonding via the nitrogen and oxygen atoms and hydrogen bonding via the carboxylic acid functionality.The reaction of [Pd(dppe)Cl2] [dppe = bis(diphenylphosphino) ethane] with isonicotinic acid and silver(I) tetrafluoroborate in acetone, followed by recrystallisation from acetone– hexane, resulted in the formation of a mixture of two sets of crystals, one yellow and the other colourless. The yellow crystals lost solvent extremely rapidly, whereas the colourless crystals were stable in air.Spectroscopic data suggested that these colourless crystals contained neither palladium nor dppe, and were instead of a silver isonicotinate complex 1. Further evidence for this conclusion was obtained by the formation of similar crystals from the reaction of silver(I) tetrafluoroborate with isonicotinic acid in the absence of [Pd(dppe)Cl2].† The microanalytical data were consistent with a formulation [Ag3(L)2]BF4, and a single X-ray analysis ‡ was undertaken both to confirm this and to determine the structure.Although the structural analysis for 1 proceeded smoothly, poor spot shape resulting from variable and large mosaicity within the sample led to unusually small thermal displacement parameters for some of the light atoms. However, this does not detract from the unexpected insight gained as a result of the crystal structure determination. The asymmetric unit (Fig. 1) was found to consist of three * E-Mail: a.d.burrows@bath.ac.uk † Silver(I) tetrafluoroborate (316 mg, 1.6 mmol) was added to a stirred suspension of isonicotinic acid (200 mg, 1.6 mmol) in acetone (40 cm3).After stirring for 48 h in darkness, a colourless solution was separated by filtration, the solvent evaporated under reduced pressure and the crude solid obtained recrystallised from acetone–hexane to yield colourless crystals of 1. IR(Nujol): n(CO2) 1580, 1545, 1394; n(BF4) 1156, 1091, 1026, 1010, 984 cm21. 1H NMR [(CD3)2CO]: d 9.24 [d, 3J(HH) 7, CH], 8.65 [d, 3J(HH) 7 Hz, CH] (Found: C, 22.0; H, 1.25; N, 4.32. Calc. for C12H8Ag3BF4N2O4: C, 22.0; H, 1.23; N, 4.28%). ‡ Crystal data for compound 1. C12H8Ag3BF4N2O4, M = 654.62, triclinic, space group P1� , a = 8.328(6), b = 10.43(2), c = 10.618(3) Å, a = 61.49(9), b = 71.48(9), g = 81.66(10)8, U = 769(2) Å3, Z = 2, m(Mo-Ka) = 3.852 mm21, T = 150(2) K, Pre-DIFABS Rint = 0.0809, R1 = 0.0325 for 1381 unique reflections from 2146 data collected over the whole sphere of reciprocal space.CCDC reference number 186/1007. silver atoms at the apices of a triangle, two isonicotinate anions and one tetrafluoroborate anion. Each nitrogen atom in the isonicotinate groups is co-ordinated to a silver atom with Ag]N distances similar to those reported for [Ag(L)(HL)]?4H2O (2.166 Å).5 The silver–silver distances within the triangle in 1 range from 2.969(5) to 3.236(5) Å (see below).Examination of the extended structure revealed that all four oxygen atoms within the two isonicotinate anions are co-ordinated, with O(1) and O(2) bonded to Ag(1) and Ag(3) in the asymmetric unit generated via the symmetry operator 2x, 2y, 1 2 z and similarly, O(3) and O(4) bonded to Ag(1) and Ag(2) generated via the symmetry operator 1 2 x, 1 2 y, 21 2 z. The combined eVect of these contacts is to render a series of one-dimensional columnar polymers in the crystal lattice (Fig. 2). When these polymers are considered in isolation, all silver atoms are four-co-ordinate, assuming silver–silver bonds to be present. Of the three silver–silver contacts within each triangle two are bridged by a carboxylate while one is unbridged, and it is this unbridged edge, between Ag(2) and Ag(3), that is the longest. A centre of inversion proximate to Ag(1) (at 0.5, 0, 0) has the eVect of interlinking the polymers into sheets by the formation of a short Ag(1) ? ? ? Ag(1) contact, concomitantly raising the co-ordination of Ag(1) to five.This Fig. 1 The asymmetric unit in compound 1 with thermal ellipsoids represented at the 30% probability level. Isotropically refined atoms are represented by non-hatched ellipsoids. Selected bond lengths (Å) and angles (8): Ag(1)]Ag(2) 3.011(2), Ag(1)]Ag(3) 2.969(5), Ag(2)]Ag(3) 3.236(5), Ag(2)]N(1) 2.172(7), Ag(3)]N(2) 2.160(6); Ag(3)]Ag(1)] Ag(2) 65.51(10), Ag(1)]Ag(2)]Ag(3) 56.61(9), Ag(1)]Ag(3)]Ag(2) 57.88(10)1942 J.Chem. Soc., Dalton Trans., 1998, Pages 1941–1942 Ag ? ? ? Ag contact is unbridged but significantly shorter [3.062(5) Å] than the unbridged edge of the triangle. The angles between the plane of the silver atoms and the planes of the isonicotinates are somewhat distorted from the perpendicular, being 88.3(2) [for the isonicotinate containing N(1)] and 77.2(2)8 [for the isonicotinate containing N(2)]. Examination of the torsion angles involving the carboxylates Fig. 2 Part of the linked polymeric columns present in the structure of 1, with the tetrafluoroborate anions omitted for clarity. Selected bond lengths (Å) and angles (8): Ag(1)]O(1ii) 2.146(6), Ag(1)]O(3i) 2.134(5), Ag(2)]O(4i) 2.134(6), Ag(3)]O(2ii) 2.129(5), Ag(1)]Ag(1iii) 3.062(5); Ag(3)]Ag(1)]Ag(1iii) 136.23(8), Ag(2)]Ag(1)]Ag(1iii) 74.07(9), O(1ii)] Ag(1)]O(3i) 173.9(2), O(4i)]Ag(2)]N(1) 179.5(3), O(2ii)]Ag(3)]N(2) 175.2(3). Symmetry operations i 2x 1 1, 2y 1 1, 2z 1 1, ii 2x, 2y, 2z and iii 2x, 2y, 2z 1 1, respectively Fig. 3 A section of the structure of polymer 1 showing the interactions between the silver atoms and the tetrafluoroborate anions. The Ag ? ? ? F contacts (Å) are Ag(1) ? ? ? F(2) 2.808(6), Ag(1) ? ? ? F(3) 2.889(7), Ag(2) ? ? ? F(2v) 2.870(6), Ag(2) ? ? ? F(4v) 3.130(7), Ag(3) ? ? ? F(4v) 2.948(6), Ag(2) ? ? ? F(2vi) 2.898(8), Ag(3) ? ? ? F(3vii) 2.857(7), Ag(3) ? ? ? F(4vii) 2.922(7). Symmetry operations v 21 1 x, y, z, vi 1 2 x, 2y, 2z and vii 1 2 x, 1 2 y, 2z, respectively revealed that this functionality in the isonicotinate containing N(2) is considerably more twisted from the pyridyl plane [13(1)8] than that in the isonicotinate containing N(1) [2(1)8].While most prevalent amongst the coinage metals for gold(I),6 d10–d10 interactions have also been observed for copper(I) and silver(I).7 In many examples containing short silver–silver distances, the metals are linked by bridging ligands and it is therefore diYcult to assess whether the d10–d10 interaction contributes significantly to the stability of the structure or whether the metal atoms are just held in proximity by the ligand system.Since compound 1 contains both bridged and unbridged silver–silver contacts it is able to oVer some insight into the role of the carboxylates. The fact that the two unsupported contacts are longer than those supported by a bridging carboxylate suggests that these ligands do have a significant eVect on the silver–silver separation.However, it is noteworthy that the unsupported distances are both considerably shorter than twice the van der Waals’ radius of silver suggesting that significant Ag ? ? ? Ag interactions must be present. Indeed, in the structure of [Ag(Him)2]6[ClO4]6 (Him = imidazole) where Ag(Him units are linked together into a triangle solely by silver–silver interactions 8 the Ag ? ? ? Ag contact is considerably longer (3.493 Å) than either of the two unsupported contacts in 1.Within the plane containing the silver triangles there are, in addition to the Ag ? ? ? Ag interactions, significant interactions between the silver atoms and the tetrafluoroborate anions (Fig. 3). These anions are oriented such that one fluorine atom [F(1)] is pointing in the direction of the polymeric chains, whereas each of the other three fluorine atoms interact with three silver atoms. The Ag ? ? ? F distances range from 2.808(6) to 3.130(7) Å, all within the combined van der Waals’ radii for both atoms (3.19 Å).Interactions between silver(I) and BF4 2 anions have been observed before, most notably in the structure 9 of [Ag(L9)2]BF4 (L9 = 2,6-dimethylpyridine) in which Ag ? ? ?F interactions [3.011(8)] serve to link the cations into chains. The reduction of symmetry of the BF4 2 anion in the solid state is further evidenced by the infrared spectrum which shows several distinct n(B]F) resonances as opposed to a single broad peak. Acknowledgements The University of Bath is thanked for a studentship (to M. T. P.) and Professor M. B. Hursthouse is thanked for providing the data set for compound 1. References 1 D. S. Lawrence, T. Jiang and M. Levett, Chem. Rev., 1995, 95, 2229. 2 S. Subramanian and M. J. Zaworotko, Coord. Chem. Rev., 1994, 137, 357. 3 A. D. Burrows, C.-W. Chan, M. M. Chowdhry, J. E. McGrady and D. M. P. Mingos, Chem. Soc. Rev., 1995, 24, 329. 4 A. D. Burrows, S. Menzer, D. M. P. Mingos, A. J. P. White and D. J. Williams, J. Chem. Soc., Dalton Trans., 1997, 4237. 5 F. Jaber, F. Charbonnier, R. Faure and M. Petit-Ramel, Z. Kristallogr., 1994, 209, 536. 6 H. Schmidbaur, Chem. Soc. Rev., 1995, 24, 391. 7 M. Jansen, Angew. Chem., Int. Ed. Engl., 1987, 26, 1098; P. Pyykkö, Chem. Rev., 1997, 97, 597. 8 G. W. Eastland, M. A. Mazid, D. R. Russell and M. C. R. Symons, J. Chem. Soc., Dalton Trans., 1980, 1682. 9 E. Horn, M. R. Snow and E. R. T. Tiekink, Aust. J. Chem., 1987, 40, 761. Received 12th February 1998; Communication 8/01218K

ISSN:1477-9226    

DOI:10.1039/a801218k

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1998, Pages 1943–1945 1943 Two-fold interpenetration of 3-D nets assembled via three-co-ordinate silver(I) ions and amide–amide hydrogen bonds Christer B. Aakeröy, Alicia M. Beatty and Brian A. Helfrich Department of Chemistry, Kansas State University, Manhattan, Kansas 66506, USA The combination of isonicotinamide with AgBF4 or AgClO4, respectively, led to isostructural compounds [tris(isonicotinamide) silver(I) tetrafluoroborate and tris(isonicotinamide)- silver(I) perchlorate], containing two 3-D interpenetrating nets of three-co-ordinate silver(I) ions linked by N]H? ? ?O hydrogen bonds between adjacent isonicotinamide ligands.Crystal engineering is a rapidly developing field of structural and supramolecular chemistry, and a wide range of assemblies that are relevant to areas ranging from biochemistry to materials science has been conceived and characterized.1 Although much of the inspiration for these eVorts originates in organic solid-state chemistry,2 the inorganic equivalent is quickly defining its own possibilities, strategies and boundaries.The most common approach to inorganic crystal engineering has been to propagate the co-ordination geometry of a specific metal ion into infinite architectures using co-ordinate–covalent bonds, leading to co-ordination polymers of varying dimensionality and topology.3 The result has been a plethora of extended assemblies, e.g.squares,4 ribbons,5 grids,6 helices,7 and interpenetrating or porous diamondoid networks.8 Far less common has been the use of non-covalent intermolecular interactions as a guide to the assembly of co-ordination complexes into extended networks.9 Although such structures can be expected to have less rigid connectors (compared to strong co-ordinate–covalent bonds), the flexibility inherent in an assembly built upon, e.g. hydrogen bonds, may lead to materials with improved solubility and structural agility.Employing a strategy using a combination of covalent and non-covalent synthesis, we now present two isostructural compounds, tris(isonicotinamide)silver(I) tetrafluoroborate 1,* and tris(isonicotinamide)silver(I) perchlorate 2,† where each structure is dominated by a three-dimensional network created by triligated silver(I) ions and short N]H? ? ? O hydrogen bonds between adjacent amide functionalities. Compound 1 was obtained by adding AgBF4 (1.1 mmol) in ethanol–water (40 ml, 1 : 1 v/v) to isonicotinamide (2.2 mmol) in ethanol–water (40 ml, 1 : 1 v/v).Compound 2 was obtained by adding AgClO4 (4.82 mmol) in water (10 ml) to an aqueous solution (30 ml) of isonicotinamide (9.82 mmol). Transparent colourless crystals * Crystal data for 1: C18H18AgBF4N6O3, M = 561.06, monoclinic, P21/n, a = 6.9461(6), b = 18.108(2), c = 16.897(2) Å, b = 97.880(6)8, U = 2105.2(3) Å3, Z = 4, Dcalc = 1.770 g cm23, m(Mo-Ka) = 1.027 mm21, Data were collected at 173(2) K and the structure was refined to R1 = 0.0368, wR2 = 0.0837 for all data, 3703 independent reflections.† Crystal data for 2: C18H18AgClN6O7, M = 573.70 monoclinic, P21/n, a = 6.9240(5), b = 18.199(2), c = 16.988(2) Å, b = 98.052(6)8, U = 2119.6(3) Å3, Z = 4, Dcalc = 1.798 g cm23, m(Mo-Ka) = 1.133 mm21. Data were collected at 173(2) K and the structure was refined to R1 = 0.0331, wR2 = 0.0808 for all data, 2781 independent reflections. CCDC reference number 186/1012.See http://www.rsc.org/suppdata/ dt/1943/ for crystallographic files in .cif format. (m.p. 1: 238–240 8C, 2: 230–235 8C) were obtained after several days through slow evaporation at ambient temperature.‡ These salts are stable in air and apparently do not decay upon continuous exposure to light. As the two compounds are isostructural, the salient features of their molecular geometries and crystal structures will be discussed together. Although the co-ordination number and geometry of silver(I) complexes can vary considerably, the presence of a three-co-ordinate silver(I) ion is somewhat unexpected since there are relatively few reported crystallographically characterized examples of such complexes involving monodentate ligands [a recent survey found three trigonal planar silver(I) structures out of a total of 90 complexes examined].10 The geometry of the complex ion is distorted trigonal planar with N]Ag]N bond angles of ca. 105, 120 and 1358, Fig. 1. The choice of isonicotinamide as a ligand was made for two reasons. First, silver(I) ions have a high aYnity for softer, nitrogencontaining ligands, which encourages covalent–co-ordinate bonds between silver and the ring nitrogen atom in preference to co-ordination to the carbonyl oxygen. Secondly, amide moieties have a well established propensity to engage in complementary hydrogen bonds resulting either in infinite ribbons (through head-to-head interactions), or in infinite chains via equivalent N]H? ? ? O interactions.§ In the case of 1 and 2 the latter motif is observed, and the structures contain three short, near-linear crystallographically inequivalent N]H? ? ? O hydro- Fig. 1 The central silver(I) ions are co-ordinated by three isonicotinamide ligands in a distorted trigonal fashion in both complexes 1 and 2 ‡ Satisfactory elemental analyses were obtained, and X-ray powder diffraction showed that the single crystals were representative of the bulk materials.§ Amide–amide interactions in organic molecular solids typically involve ‘head-to-head’ R2 2(8) or catemer C1 1(4) hydrogen bonds.111944 J. Chem. Soc., Dalton Trans., 1998, Pages 1943–1945 Fig. 2 (a) One of the 3-D cationic nets in the isostructural complexes 1 and 2. (b) The crystal lattice in a-ThSi2 gen bonds that connect neighbouring amide moieties.¶ It is possible to envisage how the pseudo three-fold symmetry of the complex ions can be propagated in several ways in the crystal structure, resulting in hexagonal sheets [analogous to molecules like trimesic acid, C6H3(CO2H3)3-1,3,5], or the three-fold symmetry can be maintained within a spiraling arrangement of ions.The crystal structures of 1 and 2 contain a combination of both of these possibilities resulting in the formation of a net-like array, the topology of which is analogous to the silicon framework in a-ThSi2,|| Fig. 2. Each structure contains two interpenetrating 3-D nets, with each net being formed through amide–amide hydrogen bonds.While the holes created by the 10-membered chair-like assembly of the silicon framework in a-ThSi2 are occupied by thorium atoms,13 the corresponding holes in 1 and 2 are interwoven with the second net, resulting in a tight-fitting three-dimensional assembly, Fig. 3. Fig. 3 The two-fold interpenetration of 3-D nets in complexes 1 and 2 ¶ Intermolecular N]H? ? ?Oamide hydrogen bond lengths (Å) and angles (8) for 1 [2]: N(7) ? ? ? O(27) 2.869(4) [2.884(4)], N(7)]H(7A) ? ? ? O(27) 157.9(1) [163.0(1)]; N(27)? ? ? O(37) 2.862(3) [2.874(4)], N(27)]H(27A) ? ? ? O(37) 162.4(1) [176.9(1)]; N(37) ? ? ? O(7) 2.817(3) [2.815(4)], N(37)]H(37A) ? ? ? O(7) 167.08(1) [168.0(1)]. Amide]anion N]H? ? ? X hydrogen bond lengths (Å) and angles (8) for 1 (X = F) [2 (X = O)]: N(27) ? ? ? X(3) 2.947(4) [3.019(5)], N(27)]H(27B) ? ? ? X(3) 159.5(1) [153.8(1)]; N(37)? ? ?X(1) 2.915(3) [2.970(5)], N(37)]H(37B) ? ? ? X(1) 156.7(1) [152.4(1)].|| Frameworks of this type have been observed in silver(I)-containing co-ordination polymers.12 Our thanks to the reviewer who drew our attention to this lattice type.J. Chem. Soc., Dalton Trans., 1998, Pages 1943–1945 1945 The formation of this framework may also be aided by the nature of the anions, which are contained within channels running through the structure. Each anion is anchored within these channels via two N]H? ? ? F or N]H? ? ? O interactions in 1 and 2, respectively.There are no noteworthy close Ag ? ? ? Ag contacts in these structures. These structures represent relatively rare examples of 3-D metal-containing nets built around three-co-ordinate metal centers and propagated via intermolecular ligand–ligand hydrogen bonds. Thus, the crystal structures of 1 and 2 demonstrate how non-covalent intermolecular interactions can lead to architectures that mimic assemblies formed by both co-ordination polymers and by ‘classic’ inorganic lattices.We intend to further explore the supramolecular assembly of metal complexes via directional hydrogen bonds, and the possibilities of guiding pseudo-trigonal planar complex ions into alternate arrangements. Acknowledgements We acknowledge financial support from Kansas State University, NSF-EPSCoR (OSR-9550487) and DuPont. References 1 C. B. Aakeröy, Acta Crystallogr., Sect. B, 1997, 53, 569; J.-M. Lehn, Supramolecular Chemistry, VCH, Weinheim, 1995; S.Subramanian and M. Zaworotko, Coord. Chem. Rev., 1994, 137, 357; F. Vögtle, Supramolecular Chemistry: An Introduction, Wiley, Chichester, 1991; G. R. Desiraju, Angew. Chem., Int. Ed. Engl., 1995, 34, 2311; M. J. Zaworotko, Nature (London), 1997, 386, 220. 2 G. R. Desiraju, Crystal Engineering: The Design of Organic Solids, Elsevier, Amsterdam, 1989; G. R. Desiraju (Editor), Perspectives in Supramolecular Chemistry, Vol. 2, The Crystal as a Supramolecular Entity, Wiley, Chichester, 1995. 3 R.Robson, B. F. Abrahams, S. R. Batten, R. W. Gable, B. F. Hoskins and J. Liu, Supramolecular Architectures, ACS Publication, Washington, DC, 1992, pp. 256–273. 4 C.-Y. Duan, Z.-H. Liu, X.-Z. You and T. C. W. Mak, Chem. Commun., 1997, 381; M. Fujita, Y. J. Kwon, S. Washizu and K. Ogura, J. Am. Chem. Soc., 1994, 116, 1151. 5 P. Losier and M. J. Zaworotko, Angew. Chem., Int. Ed. Engl., 1996, 35, 2779. 6 A. J. Blake, S. J. Hill, P.Hubberstey and W.-S. Li, J. Chem. Soc., Dalton Trans., 1997, 913; O. M. Yaghi, H. Li and T. L. Groy, Inorg. Chem., 1997, 36, 4292. 7 T. M. Garrett, U. Koert, J.-M. Lehn, A. Rault, D. Meyer and J. Fischer, J. Chem. Soc., Chem. Commun., 1990, 557. 8 L. Carlucci, G. Ciani, D. M. Proserpio and A. Sironi, J. Chem. Soc., Chem. Commun., 1994, 2755; A. J. Blake, N. R. Champness, S. S. M. Chung, W.-S. Li and M. Schröder, Chem. Commun., 1997, 1005; O. M. Yaghi and H. Li, J. Am. Chem.Soc., 1996, 118, 295; S. Subramanian and M. J. Zaworotko, Angew. Chem., Int. Ed. Engl., 1995, 34, 2127; G. B. Gardner, D. Venkataraman, J. S. Moore and S. Lee, Nature (London), 1995, 374, 792. 9 A. D. Burrows, D. M. P. Mingos, A. J. P. White and D. J. Williams, Chem. Commun., 1996, 97; M. M. Chowdhry, D. M. P. Mingos, A. J. P. White and D. J. Williams, Chem. Commun., 1996, 899; J.-C. Shi, B.-S. Kang and T. C. W. Mak, J. Chem. Soc., Dalton Trans., 1997, 2171; C. M. Drain, K. C. Russel and J.-M. Lehn, Chem. Commun., 1996, 337; L. Carlucci, G. Ciani, D. M. Proserpio and A. Sironi, J. Chem. Soc., Dalton Trans., 1997, 1801; C. B. Aakeröy and A. M. Beatty, Chem. Commun., 1998, 1067; C. B. Aakeröy and A. M. Beatty, Crystal Engineering, 1998, 1, 39. 10 D. Venkataraman, S. Lee, J. S. Moore, P. Zhang, K. A. Hirsch, G. B. Gardner, A. C. Covey and C. L. Prentice, Chem. Mater., 1996, 8, 2030. 11 L. Leiserowitz and M. Tuval, Acta Crystallogr., Sect. B, 1978, 34, 1230. 12 L. Carlucci, G. Ciani, D. M. Proserpio and A. Sironi, J. Am. Chem. Soc., 1995, 117, 4562. 13 G. Brauer and A. Mitius, Z. Anorg. Allg. Chem, 1942, 249, 325. Received 2nd April 1998; Communication 8/02520G

ISSN:1477-9226    

DOI:10.1039/a802520g

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1999, 1945–1949 1945 Synthesis of platinum(II) complexes of thymidine and 1-methylthymine (1-MeThy); crystal structure of cis-[PtCl(1-MeThy)- (PPh3)2] Lorenzo De Napoli,a Rosa Iacovino,b Anna Messere,a Daniela Montesarchio,a Gennaro Piccialli,*c Alessandra Romanelli,b Francesco RuVod and Michele Saviano b a Dipartimento di Chimica Organica e Biologica, Via Mezzocannone, 16, Università degli Studi di Napoli “Federico II”, I-80134 Napoli, Italy b Centro di studio di Biocristallografia del CNR, Via Mezzocannone 4, Università degli Studi di Napoli “Federico II”, I-80134 Napoli, Italy c Università degli Studi del Molise, Facoltà di Scienze, via Mazzini, 8, I-86170 Isernia, Italy.E-mail: picciall@unima.it d Dipartimento di Chimica, Via Mezzocannone, 4, Università degli Studi di Napoli “Federico II”, I-80134 Napoli, Italy Received 22nd February 1999, Accepted 20th April 1999 The reaction of 39,59-di-O-acetylthymidine with [Pt(PPh3)4] and KCl yielded a platinum(II) complex where the platinum is co-ordinated to the nucleobase through the N3 atom.In a similar reaction 1-methylthymine (1-MeThy) furnished the complex cis-[PtCl(1-MeThy)(PPh3)2], whose structure was determined by spectroscopic data and single crystal X-ray diVraction. When 1-MeThy was treated with [Pt(PPh3)4] in the absence of chloride ions the complex trans-[Pt(OH)(1-MeThy)(PPh3)2] was obtained. Introduction Platinum compounds, particularly cis-diamminedichloroplatinum( II) (cisplatin or cis-DDP) and several related derivatives, show important cytostatic eVects and are clinically used in the treatment of tumour diseases.1 Their biological activity is related to the ability to form covalent adducts with adjacent guanine bases in DNA.2 The synthesis of a plethora of diVerent platinum nucleobase or nucleoside complexes has largely contributed to clarifying the mechanism of these drugs.Some toxicological side-eVects of cisplatin and the drug resistance developed by some tumours further stimulated research towards the synthesis of new platinum derivatives.To the best of our knowledge, reported studies on the platination of nucleobases have been carried out using exclusively complexes of PtII or PtIV 3 as the starting material. In this framework we have investigated the reactivity of tetrakis- (triphenylphosphine)platinum(0) [Pt(PPh3)4] towards thymine or related nucleosides. This complex was chosen as a substrate by considering that some phosphines and a certain number of arylphosphine complexes have been found to be potent cytotoxic agents against tumour cells in culture or in vivo.4 In a previous paper 5 we have described the synthesis of complex 1, which is characterized by the rare s bond between PtII and C4 of the thymine base.This complex was obtained by reaction of [Pt(PPh3)4] with 39,59-di-O-acetyl-4-chlorothymidine I (Scheme 1) which proceeds by an oxidative addition mechanism.A careful analysis of this reaction showed that, together with 1 (85% yield), a minor product 2 (5–7% yield) was formed when equimolecular quantities of [Pt(PPh3)4] and I were refluxed under a nitrogen atmosphere in toluene for 2 h. Product 2 presented the well documented, for pyrimidine nucleobases, PtII–N3 co-ordination bond,6 the formation of which was not immediately explainable in our reaction system. In fact, as reported,6c,7 the N3 platination of thymine or uracil residues can easily be achieved only starting from their N3 deprotonated forms by reaction with appropriate platinum(II) complexes.Aiming at explaining the unexpected formation of complex 2 the reaction was reinvestigated. Herein we describe the results of our study which disclosed an alternative, straightforward route for the preparation of 2 in high yield. The structure of this complex has been assigned on the basis of its 1H, 31P and 13C NMR, IR and FAB MS data, as well as on single crystal X-ray diVraction studies carried out on the related complex cis- [PtCl(1-MeThy)(PPh3)2] (1-MeThy = 1-methylthyminate).Results and discussion By monitoring the reaction between I and [Pt(PPh3)4] by TLC Scheme 1 R = 3,5-Di-O-acetyl-2-deoxy-b-D-ribofuranosyl except in 3a,3b where it is 2-deoxy-b-D-ribofuranosyl.1946 J. Chem. Soc., Dalton Trans., 1999, 1945–1949 analysis, small amounts of 39,59-di-O-acetylthymidine II were detected, which disappeared in the final mixture.This suggested a possible intervention of II, obtained by an undesired hydrolysis of the very reactive 4-chloro derivative I, in the formation of complex 2. So we hypothesized an oxidative addition of the imidic N3 atom of II on [Pt(PPh3)4] generating a transient platinum hydride complex 4 [Scheme 1, eqn. (1)]. This reaction mechanism was suggested by the reported reactivity of some zerovalent platinum complexes which reacting with imides generated platinum(II) hydrides.8 Further reaction of 4 with water (probably due to trace amounts of water), followed by elimination of H2, furnished complex 5 which, by exchange with chloride ions, finally gave 2 [eqns.(2) and (3)]. To confirm this hypothesis we tested the reactivity of [Pt(PPh3)4] towards II in the presence of chloride ions. The reaction (4), performed under a nitrogen atmosphere in boiling benzene, gave complex 2 in high yield (80% after purification).The 1H and 13C NMR spectra of complex 2 showed two signals for each type of observed nucleus, thus indicating the presence of a mixture of two isomeric species (2a and 2b in 45 : 55 ratio). These isomers separated by HPLC on a silica gel column, are stable as solids but, when dissolved in CHCl3, they interconverted, re-establishing the original mixture in ca. 24 h. These results can be explained by assuming restricted rotation around the Pt–N3 bond in complex 2, inducing a further chirality in the molecule, which, associated with the presence of fixed configurations at the sugar carbons, gives rise to two diastereoisomeric forms.6a,d,9 For a better comprehension of the structure of 2 we then synthesized a similar complex using 1-methylthymine III as pyrimidine ligand, where the hindered rotation around the Pt–N3 bond was expected to generate two enantiomeric complexes.The reaction [Scheme 2, eqn. (5)], performed as described for 2, led smoothly to complex 6, recovered after silica gel chromatography in 82% yield.As expected, 6 exhibited only one signal for each observed nucleus in the 1H, 31P and 13C NMR spectra, closely related to the NMR data of 2. The 1H NMR spectrum of 6 in the presence of a chiral shift reagent confirmed its existence as two enantiomeric forms (see discussion on spectral data). The single-crystal structure of 6 is shown in Fig. 1 (see later). When the reaction of III with [Pt(PPh3)4] was carried out in the absence of chloride ions, eqn.(6), complex 7 was obtained in 85% yield. The structure and the trans geometry of 7 were ascertained by spectroscopic data and FAB MS analysis. Complex 6 could be alternatively prepared by treating 7 with potassium chloride in boiling benzene (2 h, 80% yield). Removal of the acetyl groups at the 59 and 39 positions of the sugar residues of the 2a,2b mixture was achieved by treatment Scheme 2 with concentrated aqueous ammonia for 2 h at 50 8C, giving 3a,3b (not separated, 90%), whose structure was confirmed by spectral data. This reaction, demonstrating the stability of the platinum–nucleobase linkage to basic conditions and furnishing a further derivatizable sugar compound, showed this new platinated nucleoside to be suitable for insertion into oligonucleotide chains by automated procedures.Spectroscopic data The IR spectrum of complex 2a shows strong bands at 1749, 1664 and 1588 cm21 attributed respectively to carbonyl functions of the acetyl groups and to carbonyls of the thymine base.The band at 1588 cm21 has been considered diagnostic for the N3 platinum co-ordinated thyminate ion.6a,c A weak band due to n(Pt–Cl) was observed at 305 cm21. An almost identical IR pattern was observed for isomer 2b. Analogously for complex 3, strong n(CO) bands were detected at 1653 and 1577 cm21. For complex 6 carbonyl resonances were found at 1655 and 1578 cm21, whereas only a weak signal, for n(Pt–Cl), was detected at 300 cm21.Similarly for 7 n(CO) gave strong bands at 1655 and 1579 cm21. The 31P NMR spectrum of complex 2a shows two nonequivalent phosphorus atoms due to two magnetically diVerent trans influences on each phosphine; 1J(Pt–P) values are 3265 and 3960 Hz, attributed respectively to phosphorus trans to N and trans to chloride.8 The 31P NMR spectrum of 2b is identical. For complex 6 the 31P NMR spectrum displayed the same pattern due to two cis phosphines having 1J(Pt–P) values of 3235 (trans to N) and 3984 Hz (trans to chloride).The spectrum of 7 showed a single phosphorus signal [1J(Pt–P) = 3091 Hz] which was attributed to two trans magnetically equivalent phosphines. In the 1H NMR spectrum of complex 2a protons H-6 and CH3-5 showed upfield shifts (Dd 0.92 and 0.33) compared to their resonances for free nucleoside II, suggesting N3 platination of the base.6d,10 Analogous upfield shifts were observed for complexes 2b, 6 and 7 for all the protons of the nucleobase. For 3a,3b the H-6 signals are submerged by the phosphine protons, whereas for CH3-5 signals upfield shifts of Dd 0.3 were observed.When the 1H NMR spectrum of 6 was recorded in the presence of the chiral shift reagent europium tris[3-(hepta- fluoropropylhydroxymethylene)(1)-camphorate] [Eu(hfc)3],- {camphor = (1R)-1,7,7-trimethylbicyclo[2.2.1]heptan-2-one} a doubling and a downfield shift of the signals CH3-N1 (d 3.43 and 3.32) and CH3-5 (d 2.10 and 1.92) were observed.In 1H NMR experiments, performed on the diastereomeric mixture 2 dissolved in DMSO, increasing the temperature to 125 8C, no fluxionality was observed suggesting a high barrier to rotation around the Pt–N3 bond. In the 13C NMR spectra all the isolated complexes showed for the nucleobase carbons a downfield shift in comparison with the resonances of the “free” ligands. This eVect is particularly evident for C2, C4 and CH3-5 (Dd from 1 to 5), in agreement with literature data of similar platinum(II) nucleobase complexes.11 Molecular structure of cis-[PtCl(1-MeThy)(PPh3)2]?MeOH 6 The crystal structure of cis-[PtCl(1-MeThy)(PPh3)2]?MeOH 6 is illustrated in Fig. 1, which also gives the atom numbering scheme. Selected bond distances and angles are in Table 1. The platinum atom displays square planar co-ordination: two cis corners of the square plane are occupied by the P atoms of two triphenylphosphines and the chlorine atom and the amide nitrogen of the MeThy ligand are in cis position to each other.The four atoms co-ordinated to the metal lie in a plane with very small (less than 0.08 Å) deviation from it. The plane of the MeThy ligand is approximately perpendicular to the platinum co-ordination plane, as seen by the torsion angles Cl(1)–Pt–N(1)–C(1) and Cl(1)–Pt–N(1)–C(6) of 87.3(4)J. Chem. Soc., Dalton Trans., 1999, 1945–1949 1947 and 296.4(5)8, respectively. The P–Pt distances [P(1)–Pt 2.241(2), P(2)–Pt 2.268(2) Å] are diVerent, which is consistent with the amide [trans to P(2)] having a slightly larger trans influence than chloride.9,13,14 The analysis of the Pt–N co-ordination distances shows the trans eVect of the P atom.In fact, this distance [N(1)–Pt 2.072(5) Å] is longer (ª0.08 Å) than that observed in platinum(II) complexes with amide nitrogen ligands without co-ordinated P atoms.13 The remaining bond lengths and bond angles are normal.15,16 The analysis of the triphenylphosphine moiety in cis position with respect to the Cl(1) atom shows the Cl(1) atom in a staggered conformation with respect to the C(41), C(51), C(61) Fig. 1 An ORTEP12 projection of two molecules of cis-[PtCl(1- MeThy)(PPh3)2] 6. The thermal ellipsoids are drawn at 30% probability level. Table 1 Selected intramolecular bond distances (Å) and angles (8) for cis-[PtCl(1-MeThy)(PPh3)2] with estimated standard deviations in parentheses MeThy moiety Pt–N(1) Pt–P(1) Pt–P(2) Pt–Cl(1) N(1)–C(6) N(1)–C(1) N(2)–C(4) C(6)–N(1)–C(1) C(6)–N(1)–Pt C(1)–N(1)–Pt C(4)–N(2)–C(6) C(4)–N(2)–C(5) C(6)–N(2)–C(5) O(1)–C(1)–N(1) O(1)–C(1)–C(2) 2.072(5) 2.241(2) 2.268(2) 2.354(2) 1.356(8) 1.373(8) 1.336(10) 123.4(5) 121.7(4) 114.8(4) 119.9(6) 120.9(7) 119.1(7) 120.6(5) 122.4(6) N(2)–C(6) N(2)–C(5) O(1)–C(1) O(2)–C(6) C(1)–C(2) C(2)–C(4) C(2)–C(3) N(1)–C(1)–C(2) C(4)–C(2)–C(1) C(4)–C(2)–C(3) C(1)–C(2)–C(3) N(2)–C(4)–C(2) O(2)–C(6)–N(1) O(2)–C(6)–N(2) N(1)–C(6)–N(2) 1.406(9) 1.498(10) 1.220(8) 1.246(8) 1.406(9) 1.337(11) 1.490(11) 117.0(6) 119.7(6) 122.2(7) 118.0(7) 122.7(6) 120.3(6) 122.5(6) 117.2(6) Triphenylphosphine ligands N(1)–Pt–P(1) N(1)–Pt–P(2) P(1)–Pt–P(2) P(1)–Pt–Cl(1) P(2)–Pt–Cl(1) N(1)–Pt–Cl(1) C(21)–P(1)–C(11) C(21)–P(1)–C(31) C(11)–P(1)–C(31) 88.94(15) 171.22(14) 97.64(8) 175.10(5) 87.05(8) 86.54(15) 111.4(3) 102.5(3) 102.8(3) C(21)–P(1)–Pt C(11)–P(1)–Pt C(31)–P(1)–Pt C(51)–P(2)–C(41) C(51)–P(2)–C(61) C(41)–P(2)–C(61) C(51)–P(2)–Pt C(41)–P(2)–Pt C(61)–P(2)–Pt 113.4(2) 111.5(2) 114.4(2) 101.6(3) 107.3(3) 102.5(3) 114.9(2) 120.6(2) 108.7(2) atoms of the phenyl rings: the dihedral angles Cl(1)–Pt–P(2)– C(41), Cl(1)–Pt–P(2)–C(51) and Cl(1)–Pt–P(2)–C(61) are 2172.9(3), 65.0(2), and 255.2(2)8 respectively.In the crystal packing the molecules are characterized by one intermolecular hydrogen-bond between the oxygen of the methanol molecule and O(2) atom of the MeThy ligand [distance O–H ? ? ? O(2) 2.89(1) Å; angle O–H ? ? ? O(2)]] C(6) 153.2(5)8]. The crystal structure is further stabilized by van der Waals interactions involving the phenyl and the methyl groups.Experimental Material and methods The 1H and 13C-{1H} NMR spectra were recorded on a Bruker WM-400 spectrometer at 400 and 100.13 MHz respectively. All chemical shifts are expressed in ppm with respect to the signal of the protonated solvent (CDCl3: d 7.26 and 77.0. DMSO-d6: d 2.55 and 39.5.CD3OD: d 3.31 and 49.5). The 31P NMR spectra were run on a Bruker WM-400 spectrometer at 161.98 MHz, with external reference to 85% H3PO4 (d 0.0). The complex [Eu(hfc)3] was purchased from Aldrich. The IR spectra were recorded on a Perkin-Elmer 457 spectrophotometer, FAB mass spectra (positive) on a ZAB 2SE spectrometer. The HPLC analyses and purifications were carried out on a Beckman System Gold instrument equipped with a UV detector module 166 and a Shimadzu Chromatopac C-R6A integrator.Compound II was used as supplied by Sigma. Syntheses Complexes 2a,2b. A mixture of compound II (205 mg, 0.63 mmol), [Pt(PPh3)4] (783 mg, 0.63 mmol) and finely powdered KCl (68 mg, 1.26 mmol) was suspended in benzene (8 cm3) and refluxed with stirring under a nitrogen atmosphere for 2 h. After cooling, the mixture was filtered and the solid washed with benzene. The filtrates and washings, evaporated to dryness under reduced pressure, were chromatographed on a silica gel column (3 × 50 cm) eluted with increasing amounts of MeOH in CHCl3 (from 0 to 2%, v/v) to give 544 mg of the isomeric mixture 2a,2b (80%).TLC: Rf 0.4 (eluent CHCl3–MeOH 97: 3, v/v). The isomeric mixture was separated by HPLC on a silica gel column (Lichrosphere Si-60, 250 × 4 mm, 5 mm) eluted in CHCl3 (1 cm3 min21) to give pure 2a and 2b (ratio 45 : 55, retention times 5.1 and 5.7 min, respectively). FAB MS on mixture (195Pt, 35Cl): m/z 1044, [M 2 Cl]1 and 754 [M-nucleoside] 1.Complex 5a: IR (CHCl3) 1749, 1664, 1588 [strong, n(CO)], 305 cm21 [weak, n(Pt–Cl)]; 31P NMR (DMSO-d6) d 15.3 [d, PPh3 trans to Cl, 1J(Pt–P) = 3960] and 8.6 [d, PPh3 cis to Cl, 1J(Pt–P) = 3265 Hz]; 1H NMR (DMSO-d6) d 8.32–7.00 (30 H, m, phenyl protons), 6.67 (1H, s, H-6), 6.17 [1H, dd, J(H19H29) = 5.8 and 6.0, H-19], 5.14 (1H, m, H-39), 4.23 (2H, m, H-59), 4.10 (1H, m, H-49), 2.14 and 2.07 (3H each, s, CH3CO), 2.1–1.9 (2H, m, H-29) and 1.47 (3H, s, CH3-5); 13C-{1H} NMR (DMSO-d6): d 170.0 (CH3CO), 167.9 (C-4), 153.6 (C-2), 134.7–127.5 (phenyl carbons and C-6), 110.1 (C-5), 83.6 (C-49), 80.4 (C-19), 73.2 (C-39), 63.6 (C-59), 35.4 (C-29), 20.7 and 20.5 (2 CH3CO) and 13.3 (CH3-5).Complex 5b: IR (CHCl3) 1750, 1663, 1590 [strong, n(CO)], 308 cm21 [weak, n(Pt–Cl)]; 31P NMR (DMSO-d6) d 15.3 [d, PPh3 trans to Cl, 1J(Pt–P) = 3960] and 8.6 [d, PPh3 cis to Cl, 1J(Pt–P) = 3265 Hz]; 1H NMR (DMSO-d6) d 8.30–7.00 (30 H, m, phenyl protons), 6.64 (1H, s, H-6), 6.26 [1H, dd, J(H19H29) = 6.0 and 5.9, H-19], 5.19 (1H, m, H-39), 4.26 (2H, m, H-59), 4.13 (1H, m, H-49), 2.25 (2H, m, H-29), 2.14 and 2.11 (3H each, s, CH3CO) and 1.48 (3H, s, CH3-5); 13C-{1H} NMR (DMSO-d6) d 170.0 (CH3CO), 167.8 (C-4), 154.1 (C-2), 134.7–127.5 (phenyl carbons and C-6), 109.2 (C-5), 83.6 (C-49), 80.3 (C-19), 74.2 (C-39), 63.6 (C-59), 35.3 (C-29), 20.7 and 20.5 (2 CH3CO) and 13.3 (CH3-5).1948 J.Chem. Soc., Dalton Trans., 1999, 1945–1949 Complexes 3a,3b.Complex 2a,2b (150 mg, 0.14 mmol) was treated with aqueous concentrated NH3 (5 cm3, 35%) and MeOH (5 cm3) for 2 h at 50 8C. The resulting solution, dried under reduced pressure, was purified on a silica gel column (2 × 50 cm) eluted with increasing amounts of MeOH in CHCl3 (from 5 to 20%, v/v) to give 3a,3b (126 mg, 90%). Diastereomeric mixture: IR (CHCl3) 3667 [broad, n(OH)], 1653, 1577 cm21 [strong, n(CO)]; 31P NMR (CD3OD) d 13.5 [d, PPh3 trans to Cl, 1J(Pt–P) = 3971] and 6.8 [d, PPh3 cis to Cl, 1J(Pt– P) = 3305 Hz]; 1H NMR (CD3OD) d 7.80–7.10 (62H, m, phenyl protons and H-6), 6.19 and 6.01 (1H each, dd, H-19), 4.33 (2H, m, H-39), 3.87 (2H, m, H-49), 3.72 (4H, m, H-59) 2.30–2.00 (4H, m, H-29), 1.69 and 1.62 (3H each, s, CH3-5); 13C-{1H} NMR (CD3OD) d 172.7 (C-4), 156.9 (C-2), 137–128.0 (phenyl carbons and C-6), 111.9 and 108.7 (C-5), 88.8 (C-49), 87.5 and 86.9 (C-19), 72.5 and 72.4 (C-39), 63.2 (C-59), 41.8 and 41.4 (C-29) and 13.8 (CH3-5).cis-[PtCl(1-MeThy)(PPh3)2 6. From III. A mixture of compound III (200 mg, 1.44 mmol), [Pt(PPh3)4] (1.79 g, 1.44 mmol) and finely powdered KCl (155 mg, 2.88 mmol) was suspended in benzene (10 cm3) and refluxed with stirring under a nitrogen atmosphere for 2 h. After cooling, the mixture was filtered and the solid washed with benzene. The filtrate and washings, evaporated to dryness under reduced pressure, were chromatographed on a silica gel column (2.5 × 50 cm) eluted with increasing amounts of MeOH in CHCl3 (from 0 to 3%, v/v) to give pure complex 6 (1.05 g, 82%).TLC: Rf 0.44 (eluent CHCl3– MeOH 97: 3, v/v). From 7. A mixture of complex 7 (200 mg, 0.23 mmol), and finely powdered KCl (25 mg, 0.46 mmol) was suspended in benzene (5 cm3) and refluxed with stirring under a nitrogen atmosphere. After 2 h TLC analysis showed the disappearance of 7 and the formation of 6 (164 mg, 80%) which was purified as described above and identified by spectroscopic analyses. FAB MS (195Pt, 35Cl): m/z 893, [M 1 H]1 and 957 [M 2 Cl]1.IR (CHCl3) 1655, 1578 [strong, n(CO)], 300 cm21 [weak, n(Pt–Cl)]. 31P NMR (DMSO-d6): d 15.4 [d, PPh3 trans to Cl, 1J(Pt–P) = 3984] and 8.6 [d, PPh3 cis to Cl, 1J(Pt–P) = 3235 Hz]. 1H NMR (DMSO-d6): d 8.20–7.00 (30 H, m, phenyl protons); 6.31 (1H, s, H-6); 3.0 (3H, s, CH3-1); and 1.62 (3H, s, CH3-5). 13C-{1H} NMR (DMSO-d6): d 169.9 (C-4); 155.1 (C-2); 138.6 (C-6); 109.3 (C-5); 36.1 (CH3-1); and 12.1 (CH3-5).trans-[Pt(OH)(1-MeThy)(PPh3)2] 7. A solution of compound III (200 mg, 1.44 mmol) and [Pt(PPh3)4] (1.79 g, 1.44 mmol) was refluxed in benzene (8 cm3) under a nitrogen atmosphere for 2 h. After cooling, the mixture, evaporated to dryness under reduced pressure, was chromatographed on a silica gel column (2.5 × 50 cm) eluted with increasing amounts of MeOH in benzene (from 0 to 5%, v/v) to give pure complex 7 (107 mg, 85%). TLC: Rf 0.4 (eluent CHCl3–MeOH 95: 5, v/v).FAB MS (195Pt): m/z 875 [M 1 H]1; and 859, [M 2 OH]1. IR (CHCl3) 3334 [broad, n(OH)], 1655, 1579 cm21 [strong, n(CO)]. 31P NMR (CDCl3): d 18.6 [d, PPh3, 1J(Pt–P) = 3091]. 1H NMR (CDCl3): d 7.90–7.20 (30 H, m, phenyl protons); 5.93 (1H, s, H-6); 2.67 (3H, s, CH3-1); and 1.31 (3H, s, CH3-5). 13C-{1H} NMR (CDCl3): d 170.3 (C-4); 155.2 (C-2); 137.6 (C-6); 107.8 (C-5); 36.2 (CH3-1); and 13.2 (CH3-5). Crystallography Suitable crystals of cis-[PtCl(1-MeThy)(PPh3)2] 6 for X-ray analysis were obtained by slow evaporation of CHCl3–MeOH (9 : 1, v/v) at room temperature.Intensity data collection was performed using graphite-monochromated Cu-Ka radiation (l = 1.54178 Å) and a pulse-high discrimination on a CAD4 Enraf-Nonius automated diVractometer equipped with a MicroVax 3100 Digital computer of the “Centro di Studio di Biocristallografia del CNR” at Università di Napoli “Federico II”. The independent reflections were measured in the q range 1–708.Unit cell parameters were determined by least-squares refinement of the setting angles of 25 high angle reflections (18 < q < 228). Three standard reflections were monitored periodically and showed no significant change during data collection. A total of 7789 independent reflections were measured with a w–2q scan mode. Using a prescan speed of 4.128 min21, reflections with a net intensity I < 0.5s(I) were flagged as “weak”; those with I � 0.5s(I) were measured at lower speed depending on the value of s(I)/I. The structure was solved by direct methods using the SIR 97 program.17 The best E maps revealed all the non-H atoms and the methanol solvent molecule.Refinement by the full-matrix least-squares procedure on F2 (all data) used the SHELXL 93 program18 with anisotropic thermal factors for all non-hydrogen atoms. Hydrogen atom positions were calculated and allowed to ride on their attached atoms, with Uiso s = 1.2 Ueq of the attached atom.The scattering factors for all atomic species were calculated from Cromer and Waber.19 Crystal data. C42H34ClN2O2P2Pt?CH3OH, M = 923.23, triclinic, space group P1� (no. 2), a = 11.176(8), b = 13.892(9), c = 13,36(1) Å, a = 97.31(6), b = 91.32(6), g = 88.00(6)8, U = 2056(3) A3, T = 293 K, Z = 2, m(Cu-Ka) = 8.029 mm21, 7789 unique reflections (Rint = 0.0) used in all calculations. The final wR(F2) was 0.1334; R1 = 0.0515. CCDC reference number 186/1433. See http://www.rsc.org/suppdata/dt/1999/1945 for crystallographic files in .cif format.Acknowledgements We are grateful to Ministero dell’Università e della Ricerca Scientifica e Tecnologica, Consiglio Nazionale delle Ricerche for grants in support of this investigation and to Centro di Metodologie Chimico-Fisiche dell’Università degli Studi di Napoli “Federico II” for the NMR facilities. We also thank Rita Carolla for technical assistance. References 1 P. Pil and S. J. Lippard, in Encyclopedia of Cancer, Academic Press, New York, 1997, vol. 1, pp. 392–410; J. Reedjk, Chem. Commun., 1996, 810. 2 P. M. Takahara, A. C. Rosenzweig, C. A. Frederich and S. J. Lippard, Nature (London), 1995, 377, 649; S. E. Sherman, D. Gibson, A. H.-J. Wang and S. J. Lippard, Science, 1985, 230, 412; S. E. Sherman and S. J. Lippard, Chem. Rev., 1987, 87, 1153. 3 B. Lippert, Prog. Inorg. Chem., 1989, 37, 1. 4 S. J. Berners-Price and P. J. Sadler, Struct. Bonding (Berlin), 1988, 70, 27; Coord.Chem. Rev., 1996, 151, 1. 5 V. De Felice, G. Piccialli, C. Santacroce and A. Vitagliano, Tetrahedron Lett., 1987, 28, 2757. 6 (a) B. Longato, B. Corain, G. M. Bonora and G. Pilloni, Inorg. Chim. Acta, 1987, 137, 75; (b) B. Lippert, Inorg. Chim. Acta, 1981, 55, 5; (c) R. Pfab, P. Jandik and B. Lippert, Inorg. Chim. Acta, 1982, 66, 193; (d ) N. Margiotta, A. Habtemariam and P. J. Sadler, Angew. ., Int. Ed. Engl., 1997, 36, 1185. 7 D. Neugebauer and B. Lippert, J. Am. Chem. Soc., 1982, 104, 6596; H. Schollhorn, U. Thewalt and B. Lippert, J. Am. Chem. Soc., 1989, 111, 7213. 8 D. M. Roundhill, Inorg. Chem., 1970, 9, 254; M. Ishikaw and M. Kumada, Chem. Commun., 1969, 567. 9 J. Fawcett, W. Henderson, R. D. W. Kemmitt, R. D. Russell and A. Upreti, J. Chem. Soc., Dalton Trans., 1996, 1897. 10 O. Renn, B. Lippert, H. Schollhorn and U. Thewalt, Inorg. Chim. Acta, 1990, 167, 123. 11 G. H. Y. Chu, R. E. Duncan and R. S. Tobias, Inorg. Chem., 1977, 16, 2625. 12 C. K. Johnson, ORTEP, Report ORNL-5138, Oak Ridge, National Laboratory, Oak Ridge, TN, 1976. 13 A. Lombardi, O. Maglio, E. Benedetti, B. Di Blasio, M. Saviano, F. Nastri, C. Pedone and V. Pavone, Inorg. Chim. Acta, 1992, 196, 241.J. Chem. Soc., Dalton Trans., 1999, 1945–1949 1949 14 A. Lombardi, O. Maglio, V. Pavone, B. Di Blasio, M. Saviano, F. Nastri, C. Pedone and E. Benedetti, Inorg. Chim. Acta, 1993, 204, 87. 15 W. Beck, H. Bissinger, M. Girnth-Weller, B. Purucker, G. Thiel, H. Zippel, H. Seidenberg, B. Wappes and H. Schonenberg, Chem. Ber., 1982, 115, 2256. 16 E. Ambach, U. Nagel and W. Beck, Chem. Ber., 1983, 116, 695. 17 A. Altomare, M. C. Burla, M. Camalli, G. Cascarano, C. Giacovazzo, A. Guagliardi, G. G. Moliterni, G. Polidori and R. Spagna, SIR 97, A Program for Automatic Solution and Refinement of Crystal Structures, University of Bari, 1997. 18 G. M. Sheldrick, SHELXL 93, Program for Crystal Structure Refinement, University of Göttingen, 1993. 19 D. T. Cromer and J. T. Waber, International Tables for X-Ray Crystallography, Kynoch Press, Birmingham, 1974, vol. IV, Table 2.2 B. Paper 9/01459D

ISSN:1477-9226    

DOI:10.1039/a901459d

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, Pages 1947–1949 1947 Antimony(III) tellurium(IV) chloride trioxide SbTeO3Cl: synthesis and ab initio structure determination from X-ray and neutron powder diVraction data José Antonio Alonso* Instituto de Ciencia de Materiales de Madrid, C.S.I.C., Cantoblanco, 28049 Madrid, Spain The mixed chloride oxide SbTeO3Cl has been prepared in polycrystalline form by solvolysis reaction from SbCl3 and TeCl4. The X-ray and neutron powder diVraction patterns were indexed in an orthorhombic unit cell; the structure was partially solved in the space group Pnma from the X-ray data, and completed and refined from neutron data.The crystal consists of strongly covalent [SbTeO3]1 layers, perpendicular to the a axis, corrugated as a consequence of the electrostatic repulsion of the lone pairs of SbIII and TeIV. Both semimetals are three-fold coordinated to oxygens in pyramidal configuration. The layers are held together by discrete Cl2 anions.This is one of the few examples of a positively charged two-dimensional network, very uncommon in the crystal chemistry of inorganic oxo compounds. Antimony and tellurium are typical examples of semimetallic elements for which the isoelectronic character in the oxidation states SbIII and TeIV, similarities of ionic radii and coordination features (determined by the presence of an electron lone pair) allow one to expect the formation of mixed oxo compounds of both elements, adopting closely related environments in the crystal structure.In a previous work1 the preparation and structure of the first example of a mixed chloride oxide of both semimetallic elements, Sb3TeO6Cl, obtained in single-crystal form, were described. In the layered network of composition (Sb3TeO6 1)n the positions of antimony(III) and tellurium( IV) cations were indistinguishable by X-ray diVraction, hence they were assumed to be distributed at random over the semimetal positions. Later, I reported on the existence of three new halide oxides of Sb and Te, of compositions SbTeO3Cl, Sb3Te2O7Cl3 and SbTeO3Br, for which the X-ray diVraction patterns, IR spectra and thermal behaviour were described.2 Attempts to grow single crystals failed, but, recently, I optimized the preparation procedure of SbTeO3Cl, obtaining a well crystallized polycrystalline material. The development of X-ray (XRD) and neutron powder diVraction (NPD) techniques for ab initio crystal structure determination encouraged me to investigate the structure of SbTeO3Cl from powder diVraction data.This paper reports on the results of this study. Results and Discussion The compound SbTeO3Cl was prepared as a white microcrystalline powder by solvolysis from SbCl3 and TeCl4 at 70 8C (see Experimental section), according to equation (1). After an age- SbCl3 1 TeCl4 1 3H2O 70 8C SbTeO3Cl 1 6HCl (1) ing period of 3 d, powder SbTeO3Cl samples exhibited an excellent crystallinity despite the relatively low reaction temperature, as seen from the X-ray powder diagrams (see Fig. 1). Since the X-ray diVraction (XRD) scattering factors of Sb and Te are considerably higher than that of chlorine and, particularly, oxygen, neutron diVraction techniques were necessary to complement the XRD data. The first 20 peaks of the XRD diagram of SbTeO3Cl were unambiguously indexed in an * E-Mail: jalonso@fresno.csic.es orthorhombic unit cell (de WolV figure of merit M20 = 20).Given the observed density, the unit cell contains four formula units. The observed reflection conditions suggested the space groups Pna21 (no. 33) or Pnma (no. 62). The latter, centric, was considered to solve the structure. For this crystal symmetry the matching of the observed and calculated XRD profiles without including a structural model led to excellent residuals. The unitcell parameters after the pattern matching of the XRD data were a = 11.1935(2), b = 5.4281(1), c = 7.2401(1) Å.The matching allowed the precise integration of the diVraction peaks. A set of structure factors in the range 2q 10 to 608 was used to solve the structure. A Patterson map followed by Fourier synthesis allowed the localization of Sb, Te, Cl and O(1) atoms from the XRD data. A first Rietveld refinement of the neutron data at this stage led to discrepancy factors of RI = 0.207. Atom O(2) was located from Fourier synthesis on the NPD data.After the refinement of the anisotropic thermal factors for Cl the RI factor dropped to 0.064. Given the relatively poor resolution of the neutron diVractometer at high angles, a further fully anisotropic refinement was not considered reliable. The agreement between the observed and calculated NPD profiles is shown in Fig. 2. In order to check the consistency of the neutron-derived structure with the X-ray data, a subsequent refinement of the XRD pattern was performed.A significant preferred orientation eVect was observed, which could be minimized in the Fig. 1 The XRD diagram for SbTeO3Cl, indexed according to an orthorhombic unit cell1948 J. Chem. Soc., Dalton Trans., 1998, Pages 1947–1949 refinement by considering platey-habit crystallites normal to the [0 1 0] direction, leading to acceptable discrepancy factors (Rp = 0.131, Rwp = 0.170, c2 = 5.21, RI = 0.0954). However, no improvement in the atomic coordinates (as far as standard deviations are concerned) was observed after the XRD refinement; therefore the final description of the crystal structure refers only to the neutron-derived coordinates.Table 1 includes the final atomic coordinates and thermal factors obtained from NPD data, and Table 2 lists the main interatomic distances and angles. Two views of the crystal structure are shown in Fig. 3. It is constituted by SbO3 and TeO3 trigonal pyramids (see Fig. 4), the apices of which are occupied by the semimetal atoms.Bonding distances are in the range 1.94–2.00 Å for Sb]O and 1.88–1.93 Å for Te]O. Both kinds of polyhedra are linked together via common oxygens, giving rise to corrugated layers of composition [SbTeO3]1, parallel to the bc plane. The strongly covalent two-dimensional networks are positively charged. These layers are held together by Cl2 anions, which are located between the layers at relatively long distances from metal atoms: 3.10 Å for Sb]Cl bonds, 3.16 Å for Te]Cl bonds.The very irregular oxygen environment around SbIII and TeIV shown in Fig. 4 is due to the electrical repulsion of the electron Fig. 2 Observed (crosses), calculated (full line) and diVerence (below) neutron powder diVraction profiles for SbTeO3Cl at 295 K. The short vertical lines indicate the allowed Bragg positions Table 1 Physical and crystallographic data and parameters for neutron powder data collection and refinement Formula M, Dc/g cm23 Space group, Z Crystal symmetry a/Å b/Å c/Å U/Å3 2q Range, step/8 Collection time/h, sample weight/g No.reflections Refined positional parameters Rwp, Rp, Rexp, RI ClO3SbTe 332.8, 5.02 Pnma (no. 62), 2 Orthorhombic 11.197(2) 5.427(1) 7.239(1) 439.93(1) 10.0–89.9, 0.01 4, 4 302 11 0.031, 0.024, 0.020, 0.064 Atom Sba Te a O(1) O(2) Cl Site 4c 4c 8d 4c 4c x 0.2485(6) 0.0718(7) 0.3729(4) 0.7187(7) 0.9226(5) y 0.25 0.25 0.9985(10) 0.25 0.25 z 0.5718(14) 0.1820(10) 0.5113(7) 0.1918(12) 0.5950(7) Beq/Å2 1.3(2) 0.8(2) 0.9(1) 0.9(2) 3.0(2) b a Better labelled as Sb-rich sites and Te-rich sites, given the possibility of partial mixed occupancy between antimony(III) and tellurium(IV) cations.b Anisotropic thermal factors for Cl, Uij (Å2, ×103): U11 = 44(3), U22 = 49(3), U33 = 22(3), U12 = U23 = 0, U13 = 13(1). lone pair, which is thought physically to occupy a volume similar to that of an oxygen anion.3 Considering the lone pair as a sterically significant sphere, the average volume per anion in SbTeO3ClE2 (E = electron lone pair of both SbIII and TeIV) is 18.3 Å3, which compares with the corresponding values of other oxides and chloride oxides of Sb and Te: 16.5 Å3 for Sb2Te2O9,4 22.8 Å3 for Sb3TeO6Cl,1 19.5 Å3 for Sb4O5Cl2 5 and 16.2 Å3 for Te6O11Cl2.6 Fig. 3 Two representations of the SbTeO3Cl structure: (a) along [0 1 0], showing the puckered [SbTeO3]1 layers perpendicular to the a axis; (b) view of one single layer, along the [1 0 0] direction.Key: Sb and Te, dark and light green spheres, respectively; O and Cl, red and orange balls, respectively. The c axis is oriented from left to right ( a) ( b) Fig. 4 Oxygen co-ordination polyhedra about Sb and Te: the electron lone pair physically occupies vacant sites in the structure, in the neighbourhood of each (Sb,Te) atom, as suggested Sb TeJ. Chem. Soc., Dalton Trans., 1998, Pages 1947–1949 1949 Distinction between the positions of SbIII and TeIV in the crystal is possible, in spite of the isoelectronic character of both elements and their similar fermi lengths (see Experimental section), given the significantly shorter observed Te]O than Sb]O bond lengths.In relation to this, the calculation of the bond valences 7 for the antimony and tellurium co-ordination polyhedra is enlightening. As shown in Table 3, bond valence sums for the co-ordination polyhedra of Sb and Te are close to the expected valences of 3 and 4, respectively.However, a partial mixed occupancy of the antimony and tellurium sites should not be discarded, given the size of the thermal motion. It is possible that each site is significantly contaminated with the other ion, leading to the observed valences, slightly higher than 31 for Sb and lower than 41 for Te. An average mixed occupancy of about 20% can be estimated from the valence deviations. The contribution of the bonds to chlorine to the total valence of the semimetals is very small, suggesting that the (Sb,Te)]Cl interactions are weak and predominantly ionic.Examples of positively charged networks are relatively rare in the crystal chemistry of inorganic oxo compounds, considering the large number of known examples of negatively charged networks. With the isolated exception of some crystal structures, like that of [Te2O4H]1[NO3]2,8 in most of the complex compounds of the heavier p elements of the Groups 5–7, which have been proposed to be formed by positively charged one- or two-dimensional networks, either 8 a discrete anion does not exist or the anion forms covalent bonds which complete the primary co-ordination polyhedra of the semimetal atoms in the network.In two-dimensional SbTeO3Cl, puckered layers of [SbTeO3]1 are stacked in a direction perpendicular to the a axis, with discrete Cl2 anions localized between the layers. Thus, SbTeO3Cl is one of the few oxo compounds exhibiting a positively charged two-dimensional network structure.Experimental The compound SbTeO3Cl was prepared from an equimolar mixture of SbCl3 and TeCl4 (total weight of 5 g) which was hydrolysed by addition of a 2 M HCl aqueous solution (100 cm3). The initially amorphous precipitate was digested in the reaction media at 70 8C, with stirring, for 3 d. This procedure led to a microcrystalline material which was thoroughly washed with water and dried at 120 8C in air. The chemical analysis of SbTeO3Cl was performed as fol- Table 2 Main interatomic distances (Å) and angles (8) Sb]O(1) Sb]O(2) Sb]Cl Te]O(1) Te]O(2) Te]Cl 1.998(7) ×2 1.937(13) 3.101(10) 1.932(8) ×2 1.881(11) 3.158(5) O(1)]Sb]O(1) O(1)]Sb]O(2) O(1)]Te]O(1) O(1)]Te]O(2) 86.1(4) 84.5(5) ×2 81.6(4) 91.8(6) ×2 Table 3 Bond valences * (si) for (Sb,Te)](O,Cl) bonds, multiplicity of the bonds [m] and valences (Ssi) for antimony and tellurium cations within the respective co-ordination polyhedra in the SbTeO3Cl structure si [ m] Atom Sb Te O(1) 0.93 [2] 1.13 [2] O(2) 1.10 [1] 1.30 [1] Cl 0.13 [1] 0.12 [1] Ssi 3.09 3.68 * Bond valences are calculated as si = exp[(r0 2 ri)/B]; B = 0.37; r0(SbIII]O) = 1.973, r0(SbIII]Cl) = 2.35, r0(TeIV]O) = 1.977, r0(TeIV]Cl) = 2.37 Å (from ref. 7). Individual distances (ri) are taken from Table 2. lows: 0.1 g was dissolved in concentrated HCl, then diluted to a HCl concentration of about 3 M. The antimony content (quantitatively present as SbIII) was determined by titration with KBrO3.In the resulting solution the tellurium content was determined gravimetrically, by reduction to Te metal with an excess of Na2SO3 and NH2NH2?2HCl. The chlorine content was obtained gravimetrically as AgCl: a new portion of SbTeO3Cl (0.1 g) was dissolved in an aqueous 3 M solution of KOH, then HNO3 was added until neutral pH, and the Cl2 anions from the chloride oxide were precipitated with AgNO3 [Found: Cl, 11.0; O (by diVerence), 13.7; Sb, 37.1; Te, 38.2. SbTeO3Cl requires Cl, 10.66; O, 14.42; Sb, 36.58; Te, 38.34%].The density was determined by immersion in CCl4, Dobs = 5.01(5) g cm23. The XRD patterns were collected with Cu-Ka radiation in a Siemens D-501 goniometer controlled by a DACO-MP computer, by step-scanning from 2q 10 to 1008, in increments of 0.058, and a counting time of 4 s each step. The NPD diagram of SbTeO3Cl was collected at room temperature in the multidetector DN5 diVractometer at the Siloé reactor of the Centre d’Etudes Nucléaires, Grenoble (l = 1.344 Å).The conditions of the data collection are summarized in Table 1. The XRD pattern was indexed with the TREOR 4 program.9 The structure was solved from a Patterson map from XRD data (SHELXS 86 program10) and subsequently completed and refined from NPD data. The profile refinements (pattern matching for XRD data and structural refinement for neutron data) were performed with the FULLPROF program.11 A pseudo- Voigt function was chosen to generate the line shape of the diVraction peaks.The coherent neutron scattering lengths for Sb, Te, O and Cl were, respectively, 5.57, 5.80, 5.803 and 9.577 fm. In the final run the following parameters were refined: background coeYcients, zeropoint, half-width, pseudo-Voigt and asymmetry parameters for the peak shape; scale factor, positional and thermal isotropic factors (anisotropic for Cl) and unit-cell parameters. The maximum shift for atomic coordinates in the final refinement cycle of the neutron data was lower than 1024.Acknowledgements This work was supported by the Spanish Dirección General de Investigación Cientifica y Técnica, under the project PB94-0046. The author thanks the MDN group at the CEN-Grenoble for their hospitality and the facilities at the Siloé reactor. References 1 J. A. Alonso, E. Gutiérrez-Puebla, A. Jerez, A. Monge and C. Ruiz- Valero, J. Chem. Soc., Dalton Trans., 1985, 1633. 2 J. A. Alonso, Ph.D. Thesis, University Complutense of Madrid, 1987. 3 J. Galy, G. Meunier, S. Anderson and A. Astrom, J. Solid State Chem., 1975, 13, 142. 4 J. A. Alonso, A. Castro, R. Enjalbert, J. Galy and I. Rasines, J. Chem. Soc., Dalton Trans., 1992, 2551. 5 Ch. Särnstrand, Acta Crystallogr., Sect. B, 1978, 34, 2402. 6 G. Giester, Acta Crystallogr., Sect. B, 1994, 50, 3. 7 N. E. Brese and M. O’Keefe, Acta Crystallogr., Sect. B, 1991, 47, 192. 8 J. B. Anderson, M. H. Paposch, C. P. Anderson and E. Kostiner, Monatsh. Chem., 1980, 11, 798. 9 P. E. Werner, L. Eriksson and M. Westdahl, J. Appl. Crystallogr., 1985, 16, 367. 10 G. M. Sheldrick, in Crystallographic Computing 3, eds. G. M. Sheldrick, C. Kruger and R. Goggard, Oxford University Press, Oxford, 1985, p. 175. 11 J. Rodríguez-Carvajal, FULLPROF, version 3.1, Institut Laue Langevin, 1995. Received 29th January 1998; Paper 8/00799C

ISSN:1477-9226    

DOI:10.1039/a800799c

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1999, 1951–1956 1951 Synthesis and supramolecular architectures of tetrakis(triorganostannyltetrazoles), including the crystal structure of hydrated 1,2,4,5-tetrakis(triethylstannyltetrazolyl)benzene Sonali Bhandari, Mary F. Mahon and Kieran C. Molloy * Department of Chemistry, University of Bath, Claverton Down, Bath, UK BA2 7AY. E-mail: chskcm@bath.ac.uk Received 4th March 1999, Accepted 26th April 1999 Six tetrakis(triorganostannyltetrazolyl)-alkanes and -benzenes have been prepared by a cycloaddition reaction between SnR3N3 and either 1,2,4,5-(NC)4C6H2, 1,1,3,3-(NC)4C3H4 or 1,3,3,5-(NC)4C5H8.All compounds contain tin in a trans-XYSnR3 environment; in anhydrous compounds the axial co-ordination about tin is exclusively from the tetrazoles (X, Y = N), while hydrated materials may also contain less symmetrical arrangements (X = N; Y = O). The structure of 1,2,4,5-tetrakis(triethylstannyltetrazolyl)benzene dihydrate has been determined and displays a complex three-dimensional network in which each tetrazole acts as at least a bidentate unit.One molecule of water co-ordinates one of the metal centres while the other is embedded in the lattice as a guest. Introduction We have been investigating the structural chemistry of organotin tetrazoles, influenced primarily by the variety of supramolecular lattices which these species generate.1–5 In such compounds the metal centre invariably adopts a trans-N2SnC3 geometry with a near-linear N–Sn–N moiety (established both crystallographically and by Mössbauer spectroscopy) thus acting as a rigid connector between multifunctional azoles.The polydentate nature of each tetrazole leads to a wide variety of supramolecular structures, the nature of which appears to be dependent on the hydrocarbon groups bonded to the tin. Thus, while 1,2-(Et3SnN4C)2C6H4 adopts a non-planar layer structure, its n-butyl analogue, 1,2-(Bu3SnN4C)2C6H4, exhibits a three-dimensional architecture with pores filled by the hydrocarbon groups.4 Other arrangements we have identified include a two-dimensional network of hexamers [1,3,5-(Bu3SnN4C)3- C6H3, 1,3,5-(Bu3SnN4CCH2CH2)3CNO2] 5 and a bilayer structure with channels running in all three directions.3 The latter arises when a flexible alkyl chain is used to link two organotin tetrazoles [1,6-(Bu3SnN4C)(CH2)6]. As the number of organometallic tetrazoles inherent in the molecular motif increases so, potentially, does the complexity of the lattice construct.We now report the syntheses of tetrakis(triorganostannyltetrazolyl)-alkanes and -benzenes as a natural extension of our earlier work on systems containing two and three organostannyl tetrazole moieties. The structure of 1,2,4,5-(Et3SnN4C)4C6H2?2H2O is presented and is the most complex yet of this family of compounds. Results and discussion Synthesis Six triorganotin-substituted tetra-tetrazoles 1–6 have been synthesized using the well established [312] cycloaddition route,2 in which a tetranitrile is heated with a slight excess of the appropriate azide under nitrogen in the absence of any solvent (Scheme 1).Reactions usually reached completion at elevated temperatures (100–170 8C) over one hour. The course of the reaction was followed by the disappearance of the IR bands due to the n(N3) at ª2060 cm21 and n(CN) at ª2250 cm21. The crude products in all cases were recrystallised from methanol.Cooling the methanolic solutions gave gummy materials for 1, 3–6, which needed trituration with hexane to give the respective products in a powder form. Compound 2 crystallised from methanol as a dihydrate in a form suitable for X-ray crystallography. Spectroscopy The 1H and 13C NMR data for compounds 1–6 are largely unexceptional but confirm the formulations shown in Scheme 1. The 13C NMR spectra of all species clearly show the quaternary carbon of the tetrazole at d ca. 160 confirming the result of the cycloaddition reaction; 1J(Sn–C) ª 480 Hz fall within the range for five-co-ordinate tin and the semiempirical relationship derived by Holecek and Lycka 6 for correlating 1J and C–Sn–C angles in butyltin compounds suggests a value of 1248 for compounds 1, 3 and 5, implying a trans-trigonal bipyramidal geometry about the metal centre. The 119Sn NMR spectra of compounds 1–6 exhibit resonances between d 240 and 280.In comparison with previous work on organotin-substituted tetrazoles this indicates a fiveco- ordinate tin.2 For example, the 119Sn chemical shifts of 1,2- [(R3Sn)N4C]C6H4 (R = Et, Bun or Pri), 1,3-[(R3Sn)N4C]C6H4 (R = Et or Bun) and 1,4-[(R3Sn)N4C]C6H4 (R = Bun or Pri) fall within the range of d 240 to 283 and are to low frequency of four-co-ordinated SnBu3(NMe2) (d 36).7 The five-co-ordination at tin could be achieved either via co-ordination of a solvent molecule (as for previously reported triorganostannyl tetrazoles, highly co-ordinating d6-DMSO was required for dissolution of NMR samples) or via formation of an oligomeric species.There is, however, no structural precedent for DMSO co-ordination in the solid state. In addition, the linewidths of the 119Sn resonances are broad (half width at half height, HWHH, ca. 470 Hz). Simple R3SnN4CR9 species exhibit similar spectral characteristics as a result of migration of the tin around the tetrazole nitrogens.2 The Mössbauer spectra for compounds 1–6 have isomer shifts (i.s.) in the range 1.30–1.55 mm s21 and quadrupole splitting (q.s.) between 3.5 and 3.9 mm s21.The former confirms the 14 oxidation state of the tin atom while the latter points towards a trans-trigonal bipyramidal geometry around tin, consistent with the NMR analysis. For comparison, q.s. values of 1,2- [(R3Sn)N4C]C6H4 (R = Et, Bun or Pri), 1,3-[(R3Sn)N4C]C6H41952 J. Chem. Soc., Dalton Trans., 1999, 1951–1956 Scheme 1 (R = Et or Bun) and 1,4-[(R3Sn)NC4]C6H4 (R = Bun or Pri) fall within the narrow range of 3.60–3.86 mm s21.4 The transtrigonal bipyramidal geometry about tin is achieved by axial co-ordination of the tetrazoles, a feature which is common in all published organotin tetrazole structures. Possible exceptions to this may occur, however, in the case of hydrated 2, 4 and 6.In these three cases, both trans-N2SnC3 and trans-NOSnC3 coordinations are possible, the latter arising if the intermolecular NÆSn is replaced by H2OÆSn, and both are consistent with the Mössbauer data.The quadrupole splittings for both possibilities (N2SnC3 vs. NOSnC3) fall within the same range, e.g. q.s. for crystallographically characterised 1,3-bis(tributylstannyltetrazolyl) benzene bis(methanol) is 3.65 mm s21.4 A precedent for simultaneous observation of both tin environments in the same lattice exists in bis(trimethylstannyl)-5,59-azotetrazole for which similar Mössbauer data have also been recorded (q.s.= 3.90 mm s21).8 Broad linewidths for 5 (G = 0.98, 1.07) and 6 (0.83, 1.05 mm s21) are possibly caused by the asymmetry inherent in the tetratetrazole ligands, which in turn may give rise to a combination of diVerent co-ordination modes between tin and the tetrazole nitrogens, e.g. N1 1 N2, N1 1 N3, N1 1 N4, etc. (see numbering in Scheme 1). Crystallography The asymmetric unit of compound 2 consists of three tins of unit occupancy [Sn(2), Sn(4), Sn(5)], two tins which coincide with inversion centres of half occupancy [Sn(1), Sn(3)], along with two separate ligand halves (Fig. 1). Selected bond lengths and bond angles are given in Table 1. The crystallographic symmetry at the two metal centres [Sn(1), Sn(3)] gives rise to disorder with respect to the attached ethyl groups such that only 2 of 6 b-carbons in these groups could be located with any certainty and refined. The overall structural analysis is in no way compromised by these diYculties.All tin environments are trigonal bipyramidal with equatorial ethyl groups. The asymmetric unit contains four trans-N2SnC3 [Sn(1)–Sn(4)] centres and one trans-NOSnC3 centre [Sn(5)]. Both these trigonal bipyramidal tin environments have been found in previously examined tin tetrazoles and are consistent with the spectroscopic interpretation (see above). The axially ligating atoms for the five tins, the N–Sn–N/N–Sn–O bond angles and the modes of co-ordination of the tetrazole ring with respect to the tins are summarised in Table 1.The seven unique Sn–N bond lengths are essentially equivalent within experimental error and the strength of N–Sn bonding is reflected in the proximity of all the N–Sn–N to 1808. The coordination between tetrazole and tin can be described with respect to the metal atom as being either N1 (see Scheme 1 for numbering; for tin, N1, N4 are equivalent) or N2 (N2, N3 are similarly equivalent).The versatility of the tetrazole coordination is reflected in the occurrence of both N1 1 N2 [Sn(2), Sn(4)] and N2 1 N2 [Sn(1), Sn(3)] environments. The N1 1 N2 co-ordination mode has been noted previously in 1,2- (Bu3SnN4C)2C6H4 while the N2 1 N2 mode has been found in 1,2-(Et3SnN4C)2C6H4.4 The gross three-dimensional structure of compound 2 (Fig. 2) is complex but can be broadly described in terms of layers. Propagation along c takes place primarily through the trans- N2Sn(3) [Sn(3) in the asymmetric unit as presented sits on an inversion centre at 0, 0.5, 0], while propagation along a takes place via trans-N2Sn(2) and trans-N2Sn(4).In addition, the lattice is extended in the b direction through the influence of the ligands, which are of two distinct types. The ligand based on C(1) (type A) has an inversion centre at the middle of the C6 ring (0.25, 0.75, 1.0) and is oriented asymmetrically with respect to b. The ligand based on C(7) (type B) has a twofold rotation axis through C(7) and C(10) parallel to b (0, y, 0.25) and is thus symmetrically disposed with respect to this axis.Both ligand types, but particularly those of type A, orchestrate lattice propagation into a third dimension. The pseudo-five-sided, 28-atom rings visible in Fig. 2 containJ. Chem. Soc., Dalton Trans., 1999, 1951–1956 1953 Fig. 1 The asymmetric unit of compound 2, showing the labelling scheme used in the text and Tables. Ellipsoids are at the 30% probability level.three tin atoms [Sn(2)–Sn(4)] and lie approximately in the ac plane. However, these rings are not planar and are tilted with respect to the b axis. They can be viewed as starting and finishing at tetrazoles based on C(5) sharing a common phenylene bridge (type A) and are highlighted in orange in Fig. 3. The tetrazoles labelled 1 or 2 on either side of the type A tetratetrazole are oriented approximately 308 with respect to the ac-plane and facilitate the “top to bottom” nature of these rings in the superstructure.The formation of the three-dimensional lattice is, however, complex as several features contribute to the propagation along b. First, there are two distinct types of ligands as described above. Secondly, the spirals associated with Sn(2) and Sn(4), the pseudo four-sided rings (Fig. 2), are not planar but are related by the screw axis at 0.25, y, 0.25 which propagates the lattice along b. Thirdly, there is a hydrogen-bonding interaction involving water [O(1)] which is co-ordinated to Sn(5) and N(3).This eVectively anchors the position of the two tetrazoles based on C(4) [via the nitrogens not co-ordinating Sn(1)] and generates a new 26-membered centrosymmetric macrocycle (Fig. 3; highlighted in green but sharing some common atoms with the 28-membered ring shown in orange). Finally, the lattice can also be viewed as an interpenetrating network. The pseudo-eightsided rings comprising of 38 atoms, built from 6 trans-N2Sn units and fragments of two type A and four type B ligands (Fig. 3, blue), have the trans-N2Sn(1) bridge (generated by the inversion centre at 0.25, 0.25, 1.0) involving ligand type A threaded through them. The hydrogen-bonding interactions discussed above result from an interaction between the water molecule [O(1)] coordinated to Sn(5) and N(3) of the lattice neighbour generated by the operation 1 2 x, 1 2 y, 2 2 z [O(1)–N(3): 2.65(2) Å].The distance Sn(5)–O(1) [2.27(1) Å] of compound 2 is comparable to Sn–O of hydrated 1,4-(Bu3SnN4C)2C6H4?H2O [2.368(6) Å].9 There is also a second water molecule [O(2)], not co-ordinated to tin but occupying an interstitial guest site within the lattice, which is hydrogen bonded to both O(1) and N(5) of the symmetry related molecule generated by the 0.5 2 x, 20.5 1 y, z transformation [O(2) ? ? ? O(1) 2.72(2); O(2) ? ? ? N(5) 2.84(2) Å]. This is the first example of a non-metal bound solvent guest in an organotin tetrazole lattice and suggests other inclusion species can be synthesized more rationally.Finally, the hierarchy for nitrogen co-ordination within the tetrazole is evident in the behaviour of the four independent heterocycles within the asymmetric unit (Fig. 1). Tetrazoles based on C(6) and C(11) exhibit N1 1 N3 co-ordination (Table 1; see Scheme 1 for numbering), this being the least sterically demanding combination and the one we have most commonly observed in other organotin tetrazole structures.The tetrazole incorporating C(4) also adopts N1 1 N3 co-ordination, with tin bound to N3 (the primary binding site) and the weaker hydrogen bond relegated to the use of N1. The tridentate tetrazole involving C(5) follows a similar pattern: primary co-ordination to tin using N1 1 N3, followed by the use of N4 for the hydrogen bonds. In summary, N1 1 N3 co-ordination imposes the least1954 J. Chem. Soc., Dalton Trans., 1999, 1951–1956 Fig. 2 The unit cell of compound 2 viewed along b. Colour code: Sn, blue; C, black; N, orange, O, green. Ethyl groups omitted for clarity. steric clash between bulky metal centres, and is the primary mode of tetrazole co-ordination. The use of N1 involves steric clashes with the hydrocarbon group attached to the adjacent carbon but these are less significant than metal–metal interactions which would arise from N2 1 N3 bonding. Hydrogen bonds are subservient to tin co-ordination and involve N1, then N4, for their formation. Conclusion Polyfunctional tetrazoles incorporating four organotin tetrazole units can be synthesized and used to construct complex three-dimensional supramolecular lattice arrangements.The structure of 1,2,4,5-(Et3SnN4C)4C6H2?2H2O has been determined as an example and emphasises the structural versatility of tetrazoles in orchestrating supramolecular architectures. The utility of polytetrazoles in the development of such structures is, however, limited by the increasing lack of solubility which accrues as more tetrazoles are incorporated into the ligands.Experimental Spectra were recorded on the following instruments: JEOL GX270 (1H, 13C NMR), GX400 (119Sn NMR), Perkin-Elmer 599B (IR). Details of our Mössbauer spectrometer and related procedures are given elsewhere.10 Isomer shift data are relative to CaSnO3. For all compounds, infrared spectra were recorded as Nujol mulls on KBr plates and all NMR data were recorded on saturated solutions in DMSO-d6.Syntheses The tributyltin and triethyltin azides were prepared by the literature methods.11 The method of Belsky 12 was used to prepare 1,3,3,5-pentanetetracarbonitrile.12 All other reagents were of commercial origin (e.g. Aldrich) and used without further purification. CAUTION: owing to their potentially explosive nature, all preparations of and subsequent reactions with organotin azides were conducted under an inert atmosphere behind a rigid safetyJ.Chem. Soc., Dalton Trans., 1999, 1951–1956 1955 Table 1 Selected structural data for compound 2a Tin Sn–N/Å N–Sn–N/8 Tin co-ordination a Tetrazole Tetrazole co-ordination b 12 34 5 d Sn(1)–N(1) 2.36(1) Sn(2)–N(8) 2.43(1) Sn(2)–N(9) 2.37(1) Sn(3)–N(13) 2.40(1) Sn(4)–N(6) 2.42(1) Sn(4)–N(15) 2.39(1) Sn(5)–N(11) 2.42(1) Sn(5)–O(1) 2.27(1) N(1)–Sn(1)–N(19) 180 N(9)–Sn(2)–N(8) 176.3(4) N(13)–Sn(3)–N(139) 180 N(6)–Sn(4)–N(15) 179.2(4) N(11)–Sn(5)–O(1) 175.6(5) N2 1 N2 N1 1 N2 N2 1 N2 N1 1 N2 N1 C(4) C(5) C(6) C(11) N1 1 N3 c N1 1 N2 1 N4 c N1 1 N3 N1 1 N3 a See Scheme 1 for numbering; with respect to tin, N1, N4 and N2, N3 are equivalent pairs.b See Scheme 1 for numbering. c Atom N1 involved in hydrogen bonding. d Tin co-ordinated to N, O. Fig. 3 A stereoscopic view of the unit cell of compound 2 highlighting the formation of 28- (orange), 26- (green) and 38-atom (blue) rings. Ethyl groups omitted for clarity.screen. None of the tetrazoles synthesized showed any tendancy to detonate at temperatures up to their melting points (ca. 200 8C). Syntheses 1,2,4,5-Tetrakis(tributylstannyltetrazolyl)benzene 1. A mixture of tributyltin azide (2.89 g, 8.7 mmol) and 1,2,4,5- tetracyanobenzene (0.39 g, 2.12 mmol) was heated under N2 at 120 8C for 45 min. The reaction mixture formed a white solid at this temperature, which was then dissolved in hot methanol. Hot filtration aVorded a green solution, which on cooling produced a green gum, which was then washed with hexanes to give 1 as a green powder (0.99 g, 30%), mp 210 8C (decomp.) [Found (Calc.for C29H55N8Sn2): C, 46.2 (47.2); H, 7.30 (7.20); N, 14.9 (15.1)%]. NMR [(CD3)2SO]: 1H, d 8.49 (s, 1 H, H3 of C6H2), 8.10 (s, 1 H, H6 of C6H2), 1.45 (m, 24 H, SnCH2CH2CH2CH3), 1.20–1.30 (m, 48 H, SnCH2CH2CH2CH3) and 0.77 [m, 36 H, (CH2)3CH3]; 13C, d 159.9 (CN4), 134.2 (C3,6 of C6H2), 117.7 (C1,2,4,5 of C6H2), 27.7 (SnCH2CH2CH2CH3), 26.5 [Sn(CH2)2- CH2CH3], 18.4 [SnCH2(CH2)2CH3], 13.5 [(CH2)3CH3], 2J[13CH2–117,119Sn] 77.2 (unresolved), 3J[13CH2–117,119Sn] 28.6 Hz (unresolved); 119Sn, d 248.6. 119mSn Mössbauer (mm s21): i.s. = 1.50; q.s. = 3.67. IR (cm21, KBr disk ): 3406, 2957, 2924, 2872, 2856, 1658, 1618, 1464, 1417, 1377, 1358, 1292, 1217, 1157, 1080, 1047, 1026, 879, 769, 700, 679, 524 and 432. 1,2,4,5-Tetrakis(triethylstannyltetrazolyl)benzene dihydrate 2. A mixture of triethyltin azide (0.92 g, 3.71 mmol) and 1,2,4,5-tetracyanobenzene (0.15 g, 0.84 mmol) was heated under N2 at 105 8C for 30 min.The reaction mixture formed a white solid at this temperature, which was washed with hexanes and dried in vacuo. The resultant white powder, which was partially soluble in methanol, was extracted in this solvent using a Soxhlet apparatus. Hot filtration aVorded a clear solution, which on cooling at room temperature produced colourless crystals (0.59 g, 56%), mp 200 8C [Found (Calc. for C17H33- N8OSn2): C, 33.5 (33.9); H, 5.32 (5.53); N, 17.8 (18.6)%].NMR [(CD3)2SO]: 1H, d 8.0 (s, 2 H, H3,6 of C6H2), 0.8–1.4 (m, 60 H, CH2CH3); 13C, d 160.2 (CN4), 131.1 (C3,6 of C6H2), 129.3 (C1,2,4,5 of C6H2), 9.7 (CH2CH3), 9.1 (CH2CH3), 1J[13C–117,119Sn] 478 (unresolved), 2J[13C–117,119Sn] 34.9 Hz (unresolved); 119Sn, d 243.2. 119mSn Mössbauer (mm s21): i.s. = 1.50; q.s. = 3.76. IR (cm21, KBr disk ): 3661, 3061, 2924, 2870, 1637, 1479, 1460, 1427, 1377, 1190, 1074, 1057, 1022, 997, 729, 698, 661, 524 and 447. 1,1,3,3-Tetrakis(tributylstannyltetrazolyl)propane 3. A mixture of tributyltin azide (2.07 g, 6.23 mmol) and 1,1,3,3- tetrapropanecarbonitrile (0.18 g, 1.30 mmol) was heated while stirring under N2 at 130 8C for half an hour. An orange-brown glass was formed at this temperature, which was dissolved in1956 J. Chem. Soc., Dalton Trans., 1999, 1951–1956 hot methanol. Hot filtration resulted in a yellow solution, which, on cooling, gave a yellow gummy substance.The yellow gum, when washed with hexanes, gave compound 3 as a yellow powder (0.43 g, 24%), mp 195 8C [Found (Calc. for C55H112- N16Sn4): C, 44.8 (44.0); H, 7.61 (7.58); N, 15.2 (14.9)%]. NMR [(CD3)2SO]: 1H, d 1.48 (m, 24 H, SnCH2CH2CH2CH3), 1.2–1.3 (m, 48 H, SnCH2CH2CH2CH3) and 0.78 [m, 36 H, (CH2)3CH3]; 13C, d 163.0 (CN4), 27.7 (SnCH2CH2CH2CH3), 26.4 [Sn(CH2)2- CH2CH3], 18.1 [SnCH2(CH2)2CH3], 13.5 [(CH2)3CH3], 2J[13C– 117,119Sn] 76 Hz (unresolved); 119Sn, d 250.2. 119mSn Mössbauer (mm s21): i.s. = 1.47; q.s. = 3.65. IR (cm21, KBr disk): 3420, 2957, 2924, 2872, 2855, 2073, 1653, 1635, 1464, 1377, 1342, 1292, 1155, 1126, 1026, 960, 879, 679 and 611. 1,1,3,3-Tetrakis(triethylstannyltetrazolyl)propane dihydrate 4. Prepared as for compound 3 using triethyltin azide (1.83 g, 7.38 mmol) and 1,1,3,3-tetrapropanecarbonitrile (0.26 g, 1.81 mmol). Yellow powder (1.75 g, 80%), mp 205 8C (decomp.) [Found (Calc. for C31H68N16O2Sn4): C, 31.8 (31.8); H, 5.68 (5.86); N, 19.0 (19.1)%].NMR [(CD3)2SO]: 1H, d 1.0–1.3 (m, 60 H, CH2CH3); 13C, d 163.5 (CN4), 10.1 (CH2CH3), 10.0 (CH2CH3), 1J[13C–117,119Sn] 478 Hz (unresolved); 119Sn, d 245.1. 119mSn Mössbauer (mm s21): i.s. = 1.53; q.s. = 3.87. IR (cm21, KBr disk): 3406, 3182, 2949, 2870, 2735, 1458, 1421, 1379, 1199, 1126, 1016, 956 and 684. 1,3,3,5-Tetrakis(tributylstannyltetrazolyl)pentane 5. Prepared as for compound 3 using tributyltin azide (2.13 g, 6.42 mmol) and 1,3,3,5-tetracyanopentane (0.26 g, 1.5 mmol).Yellow powder (1.56 g, 70%), mp 209 8C [Found (Calc. for C57H116N16Sn4): C, 45.6 (44.1); H, 7.73 (7.46); N, 14.9 (14.7)%]. NMR [(CD3)2SO]: 1H, d 2.50–2.80 [m, 4 H, C(CH2CH2)2], 1.48 (m, 24 H, SnCH2CH2CH2CH3), 1.20–1.25 (m, 48 H, SnCH2- CH2CH2CH3) and 0.76 [m, 36H, (CH2)3CH3]; 13C, d 160.0 (CN4), 27.7 (SnCH2CH2CH2CH3), 26.4 [Sn(CH2)2CH2CH3], 18.1 [SnCH2(CH2)2CH3], 13.5 [(CH2)3CH3], 1J[13C–117,119Sn] 476 (unresolved), 2J[13C–117,119Sn] 75.4 Hz (unresolved); 119Sn, d 253.5. 119mSn Mössbauer (mm s21): i.s. = 1.47; q.s. = 3.59. IR (cm21, KBr disk): 3387, 2957, 2924, 2872, 2856, 1655, 1589, 1464, 1400, 1377, 1342, 1292, 1251, 1226, 1080, 1049, 1026, 962, 879, 771, 748, 679, 611, 515 and 453. 1,3,3,5-Tetrakis(triethylstannyltetrazolyl)pentane hydrate 6. Prepared as for compound 3 using triethyltin azide (1.72 g, 6.9 mmol) and 1,3,3,5-tetracyanopentane (0.25 g, 1.5 mmol). Yellow powder (1.17 g, 68%), mp 206 8C (decomp.) [Found (Calc.for C33H68N16Sn4?H2O): C, 33.3 (33.5); H, 5.78 (5.92); N, 19.0 (18.9)%]. NMR [(CD3)2SO]: 1H, d 1.04–1.50 (m, 60 H, CH2CH3) and 2.48–2.55 [m, 4 H, C(CH2CH2)2]; 13C, d 161.5 (CN4), 121.9 [(CN4)2C], 38.2 [(CN4)2C(CH2)2(CH2)2], 21.9 [(CN4)2C(CH2)2(CH2)2], 10.9 [CH2CH3], 10.8 (CH2CH3), 1J[13C–117,119Sn] 482 Hz (unresolved); 119Sn, d 251.8. 119mSn Mössbauer (mm s21): i.s. = 1.43; q.s. = 3.63. IR (cm21, KBr disk): 2949, 2850, 1637, 1458, 1400, 1196, 1130, 1016, 962 and 682.X-Ray crystallography Suitable crystals of 1,2,4,5-tetrakis(triethylstannyltetrazolyl)- benzene dihydrate 2 were grown from methanol at room temperature. A crystal of approximate dimensions 0.25 × 0.25 × 0.3 mm was used for data collection. Crystal data. C34H66N16O2Sn4, M = 1205.79, monoclinic, a = 30.070(3), b = 14.241(2), c = 25.259(2) Å, b = 105.28(1)8, U = 10434(2) Å3, space group C2/c, Z = 8, Dc = 1.535 g cm23, m(Mo-Ka) = 1.936 mm21, F(000) = 4784.Crystallographic measurements were made at 293(2) K on a CAD4 automatic four-circle diVractometer in the range 2.17 < q < 23.928. Data (8368 reflections) were corrected for Lorentz-polarisation eVects and also for linear decay of the crystal during data collection. In the final least squares cycles all Sn, O and N atoms along with carbons 1–11 were allowed to vibrate anisotropically. Ethyl carbons were refined isotropically as a consequence of disorder of these groups which naturally arises from the site symmetry of the associated centres [Sn(1) and Sn(3)].Associated a-carbons were refined with half site occupancies but only two b-carbons could be reliably located and refined around these two metal centres. Hydrogen atoms were included at calculated positions where relevant on nondisordered ethyl groups. The hydrogen atoms on the water molecules could not be located with any reliability and were not modelled. The solution of the structure (SHELXS 86)13 and refinement (SHELXL 93)14 converged to a conventional [i.e.based on 4244 reflections with Fo > 4s(Fo)] R1 = 0.0628 and wR2 = 0.1451. Goodness of fit = 1.043. The maximum and minimum residual densities were 0.944 and 21.086 e Å23 respectively. CCDC reference number 186/1442. See http://www.rsc.org/suppdata/dt/1999/1951/ for crystallographic files in .cif format. Acknowledgements We thank the University of Bath for financial support in the form of a studentship (to S. B.). References 1 R. J. Deeth, K. C. Molloy, M. F. Mahon and S. Whitaker, J. Organomet. Chem., 1992, 430, 25. 2 S. J. Blunden, M. F. Mahon, K. C. Molloy and P. C. Waterfield, J. Chem. Soc., Dalton Trans., 1994, 2135. 3 A. Goodger, M. Hill, M. F. Mahon, J. G. McGinley and K. C. Molloy, J. Chem. Soc., Dalton Trans., 1996, 847. 4 M. Hill, M. F. Mahon, J. G. McGinley and K. C. Molloy, J. Chem. Soc., Dalton Trans., 1996, 835. 5 M. Hill, M. F. Mahon and K. C. Molloy, J. Chem. Soc., Dalton Trans., 1996, 1857. 6 J. Holecek and A. Lycka, Inorg. Chim. Acta, 1986, 118, L15. 7 B. Wrackmeyer, Annu. Rep. NMR Spectrosc., 1985, 16, 73. 8 M. F. Mahon, K. C. Molloy and S. F. Sayers, unpublished results. 9 S. Bhandari, Ph.D. Thesis, University of Bath, 1998. 10 K. C. Molloy, T. G. Purcell, K. Quill and I. Nowell, J. Organomet. Chem., 1984, 267, 237. 11 W. T. Reichle, Inorg. Chem., 1964, 3, 237. 12 I. Belsky, J. Chem. Soc., Chem. Commun., 1977, 237. 13 G. M. Sheldrick, SHELXS 86, A Computer Program for Crystal Structure Determination, University of Göttingen, 1986. 14 G. M. Sheldrick, SHELXL 93, A Computer Program for Crystal Structure Refinement, University of Göttingen, 1993. Paper 9/01737B

ISSN:1477-9226    

DOI:10.1039/a901737b

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1999, 1957–1965 1957 Cycloplatinated ferrocenylamine-carboxylate and dithiocarbamate complexes: synthesis and aqueous properties Kim McGrouther, Debbrah K. Weston, Delwyn Fenby, Brian H. Robinson * and Jim Simpson Department of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand. E-mail: brobinson@alkali.otago.ac.nz Received 16th February 1999, Accepted 16th April 1999 Metathetical reaction of the cyclometallated ferrocenylamine complexes [Pt{FeCp(s,h5-C5H3CHRNMe2)}(dmso)Cl] (R = H 1 or Me 3) and [Pt2{Fe(s,h5-C5H3CH2NMe2)2}(dmso)2Cl2] 2 with TlX (X = OAc or malonate), or the direct reaction with P(C6H4SO3-m)3 32 (tppms) and Et2NCS2 2(dedtc), gave [Pt{FeCp(s,h5-C5H3CHRNMe2)}(dmso)(OAc)], [{Pt[FeCp(s,h5-C5H3CHRNMe2)](dmso)}2(mal)] (mal = malonate), Na5[Pt{FeCp(s,h5-C5H3CHRNMe2)}(tppms)2], [Pt{FeCp(s,h5-C5H3CHRNMe2)}(dedtc)] and bis-Pt analogues.These complexes were characterised by analysis, ES-MS and 1H, 13C and 195Pt NMR.Metathetical reaction of 1–3 with silver(I) salts generally gave ferrocenium derivatives. Substitution trans to the Pt–N or Pt–C bond is determined by the acceptor character of the co-ordinating group and this together with steric constraints limit the range of carboxylato complexes. The acetato complex [Pt{FeCp(s,h5-C5H3CH2NMe2)}(dmso)(OAc)] crystallises with one molecule of H2O and a single crystal structure indicates a hydrogen bond between a solvent H2O and acetate ligand. Aqueous solutions of the water-soluble OAc, malonate and tppms complexes were studied by electrochemical and spectroscopic techniques.Their chemistry is regulated by pH-dependent equilibria involving aqua and hydroxo complexes and competing oxidation to the ferrocenium compound by molecular oxygen. Introduction Ferrocene is a useful building block for the synthesis of derivatives which feature as enzyme inhibitors,1 therapeutic agents,2 metabolic competitors,3 antimicrobial compounds,4 radiopharmaceutical 5 and histological agents.6 Their potential as anti-tumour agents is well documented.7 While their lipophilic character is ideal for crossing cellular membranes, their toxicity is dependent on the metabolism to water soluble derivatives via hydroxylation.Detoxification primarily occurs inside the liver microsomes.8 Conjugates of ferrocenylamines and platinum(II) are of particular interest because they may be selective molecular carriers possessing the antineoplastic properties of ferrocene and the well known cisplatin [PtCl2(NH3)2].9 Ferrocenylamine analogues of cisplatin 10,11 have been made but the facile cycloplatination of ferrocenylamines has provided 12–14 a versatile series of complexes which incorporate the two cytostatic moieties (1–3 are used in the work described herein).Toxicity, histological, platinum distribution and antitumour studies in mice have shown that these cyclometallated ferrocenylamines exhibit kidney rather than liver dysfunction, that they have reasonable toxicity and are mildly cytotoxic against standard tumours.15 However, 1–3 were active against cisplatin resistant cell lines. One of the diYculties with biological studies on the cyclometallated compounds has been their low solubility in water or saline solution; for example, peanut oil was used as a vehicle for drug injection in the toxicity work and irritation of the kidney may have been a contributing factor in the hepa- Pt dmso NMe2 C CH2 NMe2 Pt dmso CH2 NMe2 Pt dmso Fe H R Fe R = H, 1; R = Me, 2 3 Cl Cl Cl toxicity.15 It was also not clear whether, in vivo, the complexes remained intact. We therefore set out to increase the aqueous solubility, at the same time extending the range of leaving and biologically active groups in the platinum(II) co-ordination sphere.There are two potential co-ordination sites, trans to either the Pt–C (s site) or the Pt–NMe2 bond (p site), but each have specific electronic requirements.Hard neutral or anionic monodentate species or a softer donor of a chelate occupy the s site whereas soft p acceptors can replace dmso.14 Farrell 16 has shown that PtII–dmso complexes bind to DNA forming interstrand crosslinks by the displacement of dmso but a ferrocenyl cyclometallated configuration appears to strengthen the Pt–S bond as indicated by the shorter Pt–S bond length 12 and slow reactions with p acceptors.Target ligands for the work described in this paper were those with potential O–O (oxalate, ox; malonate, mal; cyclobutane- 1,1-dicarboxylate, cbdc), O–S (O-alkyl dithiocarbonate), N–S (cysteine) or S–S (diethyldithiocarbamate, dedtc) functionality as well as OAc and anionic P-donors. Within the O–O group malonate may either bridge, chelate or bind as mal-O whereas ox or cbdc must chelate; this sequence would also give an insight on the influence of the bite angle on the leaving group.Malonate is biologically active and platinum(II) complexes in which ferrocene is tethered to mal-O were found17 to be active against P338 murine leukemia cells, with congruent liver and spleen deposition. Diethyldithiocarbamate has also shown clinically therapeutic cytotoxic eVects in conjunction with platinum drugs 17,18 and it is capable of S–N, S or S–S binding. Complexes with sulfonated phosphines are a standard method to increase water solublity 19 and ferrocenylphosphines have inherent biological activity.20 Steric and electronic factors dictated that not all binding modes were achievable and the characterised complexes, solution and redox properties are described herein.Results and discussion Synthesis and structure Carboxylates. Metathetical reactions with thallium(I) salts1958 J. Chem. Soc., Dalton Trans., 1999, 1957–1965 gave a convenient route to the acetato complexes 4 and 5 (eqn. 1). Although 4 was accessible in good yield from AgOAc, metathetical reactions of 2 and 3 with AgOAc, and 1 with all other silver(I) salts, resulted in oxidation of the ferrocenyl moiety, eqn.(2). The hygroscopic ferrocenium salts 7 from AgNO3 oxidation were characterised and provided a set of water-soluble salts for sensitisation studies.21 Compounds 4–6 were characterised by microanalysis, ES-MS, FAB-MS, 1H, 13C (DEPT and heteronuclear correlation, HETCOR) and 195Pt NMR spectroscopy. Owing to the lability of the acetate group the primary ions of 4–6 in ES-MS are [(M 2 OAc) 1 CH3CN]1; at high cone voltages (40 or 80 V) both the CH3CN and dmso are lost in the primary ion.Chemical shifts for 4–6 in organic solvents are similar to those for 1–3 with ‘up and down’ Me of the SMe2 and NMe2 groups appearing as four discrete resonances with 195Pt– 1H satellites due to the planar chirality. 195Pt NMR is a useful diagnostic tool in this work and the expected 22 upfield shift from dPt[1] to dPt[4] is observed.The preparation of racemic 5 is described but both DL and meso 5 were also prepared from the appropriate stereoisomer of 2. Reaction with thallium malonate gave compound 8, eqn. (3). Surprisingly, no reaction was observed between 2 or 3 and malonate, or with TlX, where X is a potential bidentate anion, oxalate, cyclobutanedicarboxylate or acetylacetonate. FABMS and ES-MS showed that the malonate 8 was dimeric in the solid. A parent ion was not observed.The primary ion is [M 2 2(dmso)]1 followed by the cleavage ion [1 -Cl]1, an ion which may be expected if the malonato group is trans to the (Fc) C–Pt bond. Vapour pressure osmometry also confirmed the dimeric formulation in solution, as did the NMR data. In particular, J(195Pt-1H), the CH2 (mal) :Cp (Fc) ratio in the Pt dmso NMe2 CH R OC CH3 CH2NMe2 Pt dmso OC CH3 Pt NMe2 dmso CH2 OC CH3 R = H 4; R = Me 5 1-3 + TlX + + Fe Fe (1) 6 O O O 1 + AgX 4 X = OAc [7]+X– (2) Pt Me2N CH2 CO CH2 Pt OC C NMe2 dmso O dmso O H 1 + Tl(Hmal) (3) Fe Fe 8 1H NMR and one carboxylato 13C resonance were only compatible with a dimeric, O,O9 structure.Methyl and methylene carbon assignments, established via DEPT and HETCOR NMR, were compatible with the proposed structure and the non-equivalence of the prochiral NMe2 and SMe2 protons con- firmed that the cyclometallated framework was maintained. Finally, the complementarity of dPt[4] and dPt[8] shows that only one O-donor is bound per cyclometallated unit.To our knowledge this is the first bridged malonato complex in platinum(II) chemistry. trans-EVects normally favour ring closure of an malonato-O over the formation of bridged complexes and sequential chelation with the active cisplatin species cis-[PtCl- (NH3)2(OH2)]1, and cis-[Pt(NH3)2(OH2)2]21, has been demonstrated. 23 We could find no spectroscopic evidence for either O or O,O9 binding modes during the formation of 8 in buVered or unbuVered solutions, or for bidentate malonato complexes of 2 and 3.This is diYcult to rationalise as, while steric reasons may inhibit the formation of a bis-platinum analogue of 8, there are no constraints for a staggered structure derived from 2; for example, complexes of 2 with bulky phosphines are known.14 An alternative approach starting with the cis-Pt(dmso)2- (carboxylate) did not give cyclometallated products but, instead, resulted in protonation of the amine, a result not unexpected given the strong basicity of the ferrocenylamines.12 Similarly, metathetical replacement of Cl in the precursors to 1–3, trans-[PtCl2(dmso)(ferrocenylamine)], under the conditions which gave cyclometallated complexes, led to cleavage of the ferrocenylamine L, eqn.(4). The inability to isolate trans-[PtCl2(dmso)L] 1 TlX æÆ trans-[PtX2(dmso)L] æÆ decomp. (4) complexes of chelating carboxylates of 1–3 can easily be understood by reference to the structure of 8.Clearly, these carboxylates cannot bridge two cyclometallated units. Furthermore, the co-ordination of hard bases is restricted to a trans C–Pt site and chelation which requires the trans Pt–N site is not possible. Compounds 4–6 and 8 were moderately soluble in water (5 was the most soluble) but very soluble in 0.1 M NaOH as well as alcohols and CH2Cl2. A common feature of 4–6 was the crystallisation with loosely bound water molecules; these could be removed in vacuo.Values of dPt for 4–6 and 8, but not for those with other anionic groups trans to the Pt–C bond, show a strong solvent dependence (selected data are given in Table 1). For 4 hydrogen-bonding solvents cause a large upfield shift whereas the converse holds for 8; the explanation for this is not obvious as the intermolecular interactions for individual cyclometallated units should be similar for 4 and 8. This encouraged us to investigate the inter- and intra-molecular interactions in the crystal structure of 4.Crystal structure of compound 4. A perspective view of the molecule is shown in Fig. 1 with selected bond length and angle data in Table 2. Co-ordination about the Pt atom in compound 4 is similar to that observed in the closely related [Pt{CpFe- (s,h5-C5H4CH2NMe2)}(dmso)Cl] 24 but with the chloro ligand replaced by an acetato group, bound through O(2), trans to the metallated C(3) atom of the dimethylaminomethylferrocene moiety. The co-ordination sphere is completed by a dmso ligand bound through S(1) and trans to the amine nitrogen N(1).The Pt–C bond distance in the acetato complex, 1.976(8) Å, is not significantly diVerent from that observed in the chloro analogue or from those in other complexes with an equivalent set of donor atoms.25 The Pt–S and Pt–N distances are also unremarkable. In contrast, the Pt(1)–O(2) distance, 2.115(5) Å, is significantly longer than those reported for platinum(II) acetato complexes.26 This observation clearly reflects the considerable trans influence of the s-bound C(3) atom noted previously.12 The cyclopentadiene rings of the ferrocene moiety are planar, and inclined at an angle of 3.8(6)8; they adopt an approximately eclipsed conformation.The platinum boundJ. Chem. Soc., Dalton Trans., 1999, 1957–1965 1959 Table 1 195Pt NMR and E1/2 data Compound Group trans to PtC dPt a E1/2 b/V Compound Group X trans to PtC, L trans to PtN dPt a 8441 36 mal OAc OAc Cl Br I Cl OAc — 22091 22078 22122 22143 22195 22279 22136, 22156 22075 — 0.06 0.24 0.23 0.25 0.27 0.30 0.03 0.03 — 9 11 13 14 12 L = tppms, X = Cl L = X = tppms L = X = dedtc L = PPh3, X = Cl L = CO, X = Cl L = X = dedtc L = PPh3, X = Cl L = X = tppms 2(2600) 2(3259) 21974 22553 22303 21981, 22227 22557 2(3258) a dPt in CDCl3 except for those in italics which are in D2O.b Recorded in CH2Cl2 except for those in italics which are in D2O; referenced against SCE at 200 mV s21, platinum electrode at 20 8C.C(2)–C(6) ring is almost coplanar with the adjacent fivemembered platinocyclic ring [interplanar angle 0.1(6)8]. The oxygen atom O(4) of the solvent water molecule makes close contact, d [O(3) ? ? ? O(4)] 2.837(7) Å, with the carbonyl oxygen atom O(3) of the co-ordinated acetate ligand, suggesting a reasonably strong hydrogen bonding interaction in the crystal lattice. Interestingly, similar interactions are observed in two other platinum complexes with monodentate acetate ligands.26 Phosphine.A sulfonated phosphine having p-acceptor capability should co-ordinate at a trans Pt–N site but unexpectedly the anionic phosphine tppms P(C6H4SO3-m)3 32also bound at Fig. 1 Perspective view of compound 4 showing the atom numbering scheme. The possible hydrogen-bonding interaction is displayed as a dashed line. Table 2 Selected bond lengths (Å) and angles (8) for compound 4 Pt(1)–O(2) Pt(1)–S(1) Pt(1)–N(1) Pt(1)–C(3) O(2)–C(17) O(3)–C(17) C(17)–C(18) S(1)–O(1) S(1)–C(15) S(1)–C(16) N(1)–C(13) N(1)–C(14) N(1)–C(1) C(1)–C(2) O(2)–Pt(1)–S(1) O(2)–Pt(1)–N(1) O(2)–Pt(1)–C(3) S(1)–Pt(1)–N(1) S(1)–Pt(1)–C(3) 2.115(5) 2.188(2) 2.117(6) 1.976(8) 1.293(8) 1.218(8) 1.525(10) 1.473(5) 1.785(9) 1.771(7) 1.492(8) 1.490(8) 1.497(10) 1.477(10) 94.3(1) 88.6(2) 171.1(2) 175.4(2) 94.1(2) C(2)–C(3) C(2)–C(6) C(3)–C(4) C(4)–C(5) C(5)–C(6) C(8)–C(9) C(8)–C(12) C(9)–C(10) C(10)–C(11) C(11)–C(12) Fe(1)–C(2–6) Fe(1)–C(8–12) O(3) ? ? ? O(4) N(1)–Pt(1)–C(3) C(17)–O(2)–Pt(1) O(2)–C(17)–O(3) O(2)–C(17)–C(18) O(3)–C(17)–C(18) 1.468(11) 1.404(11) 1.416(9) 1.448(11) 1.422(9) 1.411(10) 1.428(11) 1.419(11) 1.426(11) 1.398(11) 2.06(2) (mean) 2.051(14) (mean) 2.837(7) a 83.3(3) 122.4(5) 124.9(7) 113.1(6) 122.0(7) a Translation 1 1 x, ��� 2 y, ��� 2 z.the trans Pt–C site. Direct addition of an aqueous solution of sodium salt of tris(m-sulfonatophenyl)phosphine to a CHCl3 solution of compound 1 at room temperature results in an immediate transfer of the orange colour to the aqueous layer due to the formation of monosubstituted 9 and the dominant bis-substituted 11 tppms complexes, eqn.(5); a similar mono- 10 and bis-tppms complex 12 were made from 3. The mono-tppms complexes 9 and 10 were only spectroscopically characterised in solutions of 11 and 12. This is the opposite of the behaviour found in reactions with PPh3.14 Compounds 9–12 rapidly oxidise in water and their syntheses required strictly anaerobic conditions.The formulation of 11 and 12 as bis-substituted adducts is predicated on the ES-MS and NMR spectra. Since they are highly charged species, cations are accumulated in the gas phase to give a net charge of 23. Thus the primary ion in the ES-MS for 11 is [11 2 4Na1 1 7H1]; the primary ion for 12 was likewise [12 2 8Na1 111H1]. The SMe2 resonances were absent in the 1H NMR of 11 and 12 although, from the NMe2 profile, planar chirality is maintained.dPt[11] = 23259 and dPt[12] = 23258, akin to those for chelated phosphine analogues (cf. d 23970 for the dppm complex).14 The 31P NMR also supported the cis orientation of the ligands. A smaller 1JPt–P is observed for the phosphorus trans to the Pt–C bond (3662/3690 Hz for 11 and 12 respectively) compared to that for phosphorus trans to the Pt–N bond z), as expected for a weaker Pt–P bond in the trans Pt–C site. Both coupling constants are larger than those for comparable chelates (1JPt–P =1510 and 3300 for the dppm analogue), but smaller than for P(OPh)3 (1JPt–P = 7153),14 and presumably reflect the high charge on the complex.For 9 and 10 a single 31P resonance, a typical dH for an SMe2 group in cyclometallated derivatives, and the coupling constants (1JPt–P = 3735, 3675 Hz for 9 and 10 respectively) characterised these unstable molecules as having a tppms ligand trans to the Pt–N bond. The anionic phosphine induces water solubility but also functions as both a hard and soft donor.This could be Pt NMe2 C Cl P(C6H4SO3)3 H H Pt NMe2 C P(C6H4SO3)3 P(C6H4SO3)3 H H (5) 1 + n(tppms3–) + Fe 3– Fe 9 11 5–1960 J. Chem. Soc., Dalton Trans., 1999, 1957–1965 important for biological activity and we therefore looked at other anions with this capability. Diethyldithiocarbamate/O-alkyl dithiocarbonate. In contrast to sodium carboxylates the direct reaction of sodium diethyldithiocarbamate with compounds 1 and 3 at room temperature gave good yields of the water-insoluble N,S chelates 13 and 14, eqn.(6). Parent ions were observed in both the FAB- and ESMS (at a cone voltage of 80 V); they are very stable species. Non-equivalence of the NMe and NEt protons and carbons was observed in the 1H and 13C NMR for 13 confirming the N,S chelate structure. The CS2 resonance dC 211 is typical of N,Schelate complexes. The NMR complexity increases further for 14 as the platinum(II) co-ordination sites are non-equivalent and individual dH and dC resonances are seen for each CH3 and CH2 group.The PtN2SC co-ordination sphere results in a 195Pt resonance (Table 1) at d 21974, for 13, and two at d 21981 and 22227 for 14, compared to 22070 (22075), 22140 (22136 and 22156) and 22550 (22557) for PtNOSC, PtNSClC and PtNPClC respectively (data for di-Pt compounds in italics). The diethylthiocarbamate ligand is a poor p acceptor and the anionic sulfur and tight ‘bite’ would contribute to the upfield shift but the 240 ppm diVerence between the two dPt, not seen in other bis-Pt cyclometallated complexes (Table 1), suggests that the co-ordination sphere in 14 is distorted.Given the ready formation of an N,S anionic chelate we anticipated a similar result for an O,S donor ligand but there was no NMR evidence for substitution by O-alkyl dithiocarbonate. Reactivity in aqueous solution Oxidation of compounds 4–6 by Ag1 in non-aqueous solvents to give green ferrocenium salts 7 has already been mentioned.What was unexpected was the facile oxidation of 4–12 in water by molecular oxygen, in all solvents, as manifested by the collapse of resonances in the NMR and the onset of ferrocenium absorption bands in the visible spectra. This facile oxidation had a marked influence on reactivity in aqueous solution; in particular, solutions of 4–6 and 8 were eYcient scavengers of Cl2 ion converting rapidly into 1–3.Electrochemical data were collected for all compounds but detailed spectroscopic studies were only undertaken on 4 and 8 as the oxidation process is extremely fast for 11 and 12. Electrochemistry. Cycloplatination shifts Fc1/0 approximately 0.2 V cathodic of ferrocene and compounds 4–6, 8 and 13 and 14 displayed typical reversible Nernstian behaviour for the [1/0] couple. There was nothing unusual in the E1/2 values except for the dimer 8, E1/2 = 0.06 V, which is ª 0.16 V more cathodic than comparable couples 13 (Table 1).Cyclic voltammetric and square wave responses for 11 and 12 were complicated by the lability of the tppms, particularly if traces of water were present, but in non-aqueous solvents Ep[11] at ª 0.10 V is comparable to E1/2 for the PMePh2 and dppm complexes of 2.13 In water E1/2[4–6] and E1/2[8] are apparently chemically Pt NMe2 CH2 S NEt2 C S S NEt2 C S CH2 NMe2 Pt Pt Et2N C S S (6) Fe 14 13 Fe 1 or 3 + dedtcreversible but the slow electrode kinetics results in large DEp of ª 100 mV.Taking cognisance of junction potentials there is a cathodic shift of ª 0.1 V from acetone to water. The electrochemical response for compound 4 was independent of pH, scan rate or solvent mix (e.g. methanol–water). However, a second cathodic wave is seen for 8 in water at scan rates > 800 mV s21 (Fig. 2), indicative of an ECE process. We suggest that this is due to dissociation of one end of the bridging malonate ligand on oxidation to give an mal-O analogue of 4 (there is evidence for this process in ES-MS, eqn.(7). Compounds 11 and 12 oxidised rapidly in water during the electrochemical measurement which, together with the ligand lability and co-ordination of water at the trans Pt–C site, led to very complex voltammetric data. When Cl2 was added to an aqueous solution of 4–6 or 8 the only redox process seen was that due to the respective 1–3. NMR. Provided the sample is sealed under argon, there is no change with time in the profile of the 195Pt resonance for compound 4 in any solvent.dPt[4] displays a large variation with solvent: 22122 in D2O, 22078 in CDCl3 22138 in MeOH and 22038 in acetone. This dependence on solvent is attributed to Fig 2 Cyclic voltammograms of compound 8 electrode at a platinum (a) in acetone, NEt4ClO4, 20 8C, repeat scans, 50, 100, 800 mV s21; (b) in water, NaClO4, 20 8C, 2 scans, 100 (dotted) and 800 mV s21. Pt Me2N CH2 NMe2 CH2 Pt OCCH2CO dmso Pt Me2N CH2 dmso solv NMe2 CH2 Pt OCCH2CO– + dmso (7) Fe Fe O O O Fe Fe 8 OJ.Chem. Soc., Dalton Trans., 1999, 1957–1965 1961 hydrogen bonding although the formation of another species could not be ruled out in aqueous solvents. Confirmation that a new species is formed in the presence of water came from the appearance of a new resonance at d 22073 when D2O was added to dry MeOH solutions of 4, the intensity being proportional to the relative amount of D2O added.A similar downfield shift and new resonances were found in acetone– D2O and CDCl3–D2O solvent mixes. Concomitant with this downfield shift in dPt, dH(OAc) changes to the position of an unco-ordinated OAc but planar chirality is maintained in the co-ordination sphere with only small shifts in the prochiral protons (SMe2, NMe2). These data are consistent with the formation of an aqua complex 15. However, immediately compound 4 is dissolved in D2O or ‘wet’ organic solvents in air the 195Pt resonance broadens and eventually collapses, as do the ferrocene proton resonances, and the solution has a green tinge.These spectral changes are faster at low pH and at pH > 9 spectral collapse due to the oxidation is relatively slow. Similar observations were made for aqueous solutions 5, 6 and 8. In acid the resonance attributed to 15 is the major species but at pH 6 15 and a new species (dPt 22257) coexist. At pH > 8 the only remaining species has dPt 22027.The addition of ClO4 2 to 4(aq) in D2O in air has no immediate eVect on dPt[4] but buVered PO4 32 (pH 7.4), OD2 (pH 9) and glycinate shift dPt to 22027, 22024 and 22209 respectively. The 1H NMR spectra show that the cyclometallated skeleton is retained but in the PO4 32 and OD2 solutions (but not glycinate) dH(SMe2) surprisingly disappeared. Since the dmso cannot be replaced in non-aqueous solutions by other than p acceptors the loss of dH(SMe2) suggests that another leaving group in the trans Pt–N position has been created.In halogenated solvent–water mixtures in air, or with Cl2 present, there is rapid formation of 1–3, clearly seen in the 195Pt NMR, particularly if a trace of acid is present (Scheme 1). Electronic spectra. The UV/visible spectra were run in conjunction with the NMR as they give an insight into the oxidation step. In dry organic solvents compounds 4–6 and 8 have the 1A1g æÆ 1E1g(1E2g) transition at ª450 nm. This oxidation in water gives rise to two new bands at ª 570(sh) nm and the major 2E1g æÆ 2E1u transition at 750 nm27 of a ferrocenium species (Fig. 3). There is a red-shift compared to the parent ferrocenylamine and an increase in oscillator strength, features which are common within ferrocene derivatives 28 but not usually seen in complexes with metal ions. Undoubtedly, this is a consequence of cyclometallation causing a mixing of the co-ordinated platinum(II) and ferrocenium orbitals. By monitoring the band at 750 nm it was found that oxidation of 4 to 41 is a pseudo-first order reaction, t1/2 = 16 min at pH 2 decreasing with increased pH (pH 6: t1/2 = 68 h) until, at pH 12, t1/2 = > 120 h; this substantiates the qualitative NMR results.The lmax of the product and the change in molar absorbance with time diVer at pH 2, 6 and 9 (Fig. 3) indicating that diVerent species are present. Equilibria in aqueous solution. These NMR and spectral data show that two distinct processes influence the aqueous solution chemistry of the water-soluble complexes (Scheme 1).First, there is an equilibrium which leads to a hydrated species 15 which provides a labile group trans to the Pt–C bond and subsequent co-ordination of weakly co-ordinating groups like the glycinate anion. Secondly, an oxidation process involving molecular oxygen leading to ferrocenium species. Consequently, the electrochemical investigations in water were with solutions containing both the original complex and 15.Aside from the oxidation process the equilibria proposed in Scheme 1 are familiar in cisplatin chemistry.10,29 At pH 2 the aqua species 15 (dPt 22122, 580/785 nm) dominates and, as the pH increases, hydroxo species 16 (dPt 22257, 575/750 nm) is formed. In strongly basic solutions a hydroxo-bridged species 17 may be produced which stabilises the ferrocenyl core of 4–6 to oxidation. This explains why dPt is the same for solutions buVered by PO4 32 and OD2. It is postulated that formation of a dimsyl species 18 at this pH provides a good leaving group and the impetus to create the necessary cis co-ordination site.Concurrent with the establishment of the equilibria incorporating the neutral species, oxidation gives a parallel series of products incorporating the ferrocenium analogues, the relative concentration being influenced by time and pH. It is well known that ferrocenium species are stabilised in acid solution, and clearly the proportion of oxidised species will decrease with pH, but under physiological conditions for biological testing ferrocenium species will dominate.Conclusion Incorporation of carboxylate moieties into the cyclometallated platinum(II) complexes based on ferrocenylamines induces the water solubility necessary for drug use. The trans influence and the preference for a p acceptor trans to the Pt–N bond dictate the range of ligands which can be co-ordinated, in particular chelating carboxylates.An additional factor is the steric conges- Scheme 1 Pt dmso NMe2 C R OC CH3 Pt dmso NMe2 C R OH2 Pt dmso NMe2 C R OH Pt NMe2 CH R OH OH Pt Me2N CH Pt NMe2 C R OH S O H2C CH3 R OAc– H2O H H H – Fe 17 Fe Fe + O2 4 15 [15]+ 16 18 Fe Fe + –H+ –H+ Fe O H1962 J. Chem. Soc., Dalton Trans., 1999, 1957–1965 tion around the PtII but the absence of malonato complexes of 2 and 3 is unexpected. Toxicity and anti-tumour data have been published for 4.15 Data now available for 5, 6 and 8 confirmed that this class of compound shows general hepatotoxicity with lower toxicity than the “free” ligands and there was less intestinal irritation with the water soluble compounds.Most signifi- cant, however, is that their cytotoxicities are virtually identical to those of the parent chloro complexes 1–3.21 The reason for this is now clear. In the presence of oxygen, when 4–6 or 8 encounter Cl2(aq) in vivo, they are converted into 1–3 and consequently in vivo biological testing, especially in saline solution, will always be of the chlorocycloplatinated species irrespective of the injected complex.The evidence strongly supports the formation of an aqua complex 15 at low pH, and hydroxo species at higher pH, in aqueous solutions of the carboxylate derivatives. In principle, 15 should have provided a route to complexes with amino acids and nucleotides (as with cisplatin 30) but there was no NMR evidence for substitution under strictly anerobic conditions; substitution in aqueous solution is complicated by the facile oxidation to ferrocenium species in air.Although molecular oxygen is definitely involved, there is insuYcient evidence to speculate whether oxidation involves a pH-dependent peroxo or radical oxidation mechanism. The oxidation is being thermodynamically driven by the lower E1/2 for the cycloplatinated complexes but the system is more subtle than this because the addition of Cl2 to solutions of the ferrocenium species gives neutral 1–3, not [1]1–[3]1.From a physiological perspective, the in vivo equilibria and biologically active complex will be diYcult to unravel. Experimental All synthetic work was performed in a fumehood as ferro- Fig 3 Electronic spectra of compound 4 in water, 20 8C, under argon, at various times after dissolution: (a) pH 2, intervals of 20 min, t1/2 = 16 min; (b) pH 6, intervals of ª 50 min, t1/2 = 68 h; (c) pH 12, over 400 h.cenylamines have acrid odours. All reactions were carried out in oven-dried glassware under an atmosphere of argon or oxygenfree nitrogen. The compounds 1, 2, 3,12 and TlX31 were prepared by literature methods. The IR and NMR spectra were recorded on Digilab FX60 and Varian VXR300 MHz /Gemini 200 MHz spectrometers respectively, with 195Pt referenced against K2PtCl4. Microanalyses were carried out by the Campbell Microanalytical Laboratory, University of Otago.Electrospray mass spectra were recorded on a VG Platform II spectrometer in a 1 : 1 v/v acetonitrile–water or methanol–water mobile phase (0.1 mM in compound) and FAB spectra on a Kratos MS80RFA instrument with an Iontech ZN11NF atom gun. Electrochemical measurements were performed with a three-electrode cell using a computer controlled EG & G PAR 273A potentiostat/galvanostat at scan rates 0.05–10 V s21. A polished platinum disc electrode was employed; the reference was SCE uncorrected for junction potentials ([ferrocene]1/0, E1/2 = 0.466 V in acetone), the supporting electrolyte 0.1 M (NEt4- ClO4) and the substrate ª 1 × 1023 M.Preparation of compounds 4–6 from thallium(I) acetate Compound 4. To a solution of compound 1 (52.8 mg, 0.96 mmol) in chloroform (5 ml) was added a solution of thallium(I) acetate (25.3 mg, 0.96 mmol) in ethanol (5 ml). The mixture was left standing at room temperature in the dark for six hours. The thallium(I) chloride which had precipitated and was removed by centrifuge.More precipitated when the supernatant solution was left overnight at room temperature. After all had precipitated and been filtered oV, the orange solution was evaporated to dryness and the residue recrystallised from acetone–hexane (1 : 3) to give orange-yellow crystals of 4 (68.3%) (Found: C, 35.63; H, 4.57; N, 2.36. C17H25FeNO3PtS requires C, 35.55; H, 4.39; N, 2.44%). dH(CDCl3) 2.04 (s, 3 H, CH3CO2); 2.83 (s, 3 H, JPt–H = 15.5, NCH3); 3.03 (s, 3 H, JPt–H = 14.2, NCH3); 3.37 (s, 3 H, JPt–H = 12.4, SCH3); 3.57 (s, 3 H, JPt–H = 13.5 Hz, SCH3) and 4.12–4.33 (m, 8 H, C8H8).dPt(CDCl3) 22076. n(KBr, cm21) 1614 (C]] O), 1319 (C–O) and 1139 (S]] O). lmax/nm(e/M21 cm21) (CHCl3) 455(332). Compound 6. This was prepared similarly, from compound 2 (26.2 mg, 0.29 mmol) and thallium(I) acetate (15.2 mg, 0.58 mmol). The orange residue was recrystallised from benzene– hexane (1 : 3) to give pale orange crystals of 6 (Found: C, 30.32; H, 4.12; N, 2.92.C24H40FeN2O6Pt2S2 requires C, 29.94; H, 4.19; N, 2.91%). dH(CD2Cl2) 1.93 (s, 6 H, CH3CO2); 2.73 (s, 6 H, JPt–H = 15.0, NCH3); 2.92 (s, 6 H, JPt–H = 13.2, NCH3); 3.33 (s, 6 H, JPt–H = 11.7, SCH3); 3.44 (s, 6 H, JPt–H = 12.3 Hz, SCH3); and 4.04–4.24 (m, 8 H). dPt(CD2Cl2) 22075. n(KBr, cm21) 1620 (C]] O), 1328 (C–O) and 1140 (S]] O). Compound 5. Compound 3 (43.7 mg, 0.77 mmol) in the minimum volume of chloroform was added to thallium(I) acetate (0.2032 g, 0.77 mmol) dissolved in ethanol (10 ml).The mixture was stirred for 10 mins and then left to stand at room temperature overnight in the dark. The precipitated thallium chloride was centrifuged, the supernatant solution filtered and then left to stand until precipitation had stopped. The orangeyellow residue obtained after the solvent was removed was recrystallised from acetone–methanol to give 5 as an orange solid (62%); mp 182 8C (Found: C, 36.45; H, 4.94; N, 2.41.C18H27FeNO3PtS requires C, 36.74; H, 4.63; N, 2.38%). ES-MS: m/z 571, [M 2 OAc 1 CH3CN]1; and 528, [M 2 OAc]1. dH(CDCl3) 1.23 (d, 3 H, J = 6.88, CHCH3), 2.03 (s, 3 H, O2CCH3), 2.50 (s, 3 H, 3JPt–H = 36.1, NCH3), 2.79 (s, 3 H, 3JPt–H = 32.8, NCH3), 3.38 (s, 3 H, 3JPt–H = 22.9, SCH3), 3.51 (s, 3 H, 3JPt–H = 30.2 Hz, SCH3), 4.03 (s, 1 H, one of h5-C5H3), 4.09 (s, 5 H, h5-C5H5), 4.26 (s, 1 H, one of h5-C5H3) and 4.38 (s, 1 H, one of h5-C5H3). dC (CDCl3) 11.15 (CCH3), 25.40 (CH3CO2), 29.72 (SCH3), 43.51 (SCH3), 46.14 (NCH3), 47.65 (NCH3),J.Chem. Soc., Dalton Trans., 1999, 1957–1965 1963 63.29 (CH), 65.72 (CH), 69.52 (h5-C5H5), 69.59 (CH), 70.65 (CH), 74.04 (quaternary carbon), 97.73 (quaternary carbon) and 177.58 (CH3CO2). dPt(CDCl3) 22091. n(KBr, cm21) 1602(C]] O), 1414(CH3CO2), 1130(C–O), 1022(S]] O) and 688(C–S). lmax/nm(e/M21 cm21) 451(339). Preparation of compound 8 A chloroform solution of compound 1 (0.4591 g, 0.83 mmol, 45 ml) was added to thallium malonate (0.4259 g 0.81mmol), in boiling distilled water–ethanol.Thallium chloride precipitated as the solution was stirred for 48 h in the dark. The liquid was centrifuged, filtered and solvent stripped to give a bright orange oil 8 which eventually solidified on pumping in a high vacuum (83%); mp 150 8C (decomp.) (Found: C, 33.96; H, 4.45; N, 2.31; S, 5.60. C33H48Fe2N2O6Pt2S2?2H2O requires C, 33.91; H, 4.31; N, 2.40; S, 5.49%). ES-MS: m/z 1055 [M1-dmso].dH(CDCl3) 2.85 (s, 3 H, 3JPt–H = 15.9, NCH3), 3.08 (s, 3 H, 3JPt–H = 14.7, NCH3), 3.31 (s, 2 H, C3H2O4), 3.41 (s, 3 H, 3JPt–H = 13.8, SCH3), 3.48 (s, 2 H, CH2), 3.59 (s, 3 H, 3JPt–H = 14.2 Hz, SCH3), 4.15 (s, 5 H, h5-C5H5Fe) and 4.32 (s, 3 H, h5-C5H3Fe). dC(CDCl3): 45.45 (SCH3), 46.22 (SCH3), 49.47 [(CO2)2CH2], 51.91 (NCH3), 52.31 (NCH3), 61.60 (CH2), 66.68 (CH2), 68.84 (C5H5Fe), 94.65 (quaternary C) and 174.76 [(CO2)2CH2]. dPt(CDCl3) 22091. n(KBr, cm21) 1662(C]] O), 1125(C–O) and 1015(S]] O).lmax/ nm(e/M21 cm21) (CHCl3) 455 (72). A similar reaction with compound 2 gave only starting material; other methods tried unsuccessfully were hot and cold acetone–water and chloroform–hot water solvent mixtures, and ultrasonic reactions. Reaction of compound 1 with other thallium(I) salts Thallium cyclobutane-1,1-dicarboxylate, a new salt, was synthesized as follows. Thallium(I) nitrate (0.500 g, 0.19 mmol), dissolved in the minimum amount of hot water, was added to a boiling aqueous solution of cyclobutane-1,1-dicarboxylic acid (0.271 g, 0.19 mmol) and the solution concentrated.White platelets of the salt deposited on cooling (86%); mp 208 8C (Found: C, 12.96; H, 1.01. C3H3O2Tl requires C, 13.08; H, 1.10%). n(KBr, cm21) 1703 (C]] O). dH(D2O) 1.95 (2 H, CH2B) and 2.48 (4 H, CH2A,A9). dC(D2O) 180.30. This salt was used in reactions with compounds 1 and 2, in a variety of solvent mixtures, without success. A similar result was obtained with thallium(I) oxalate and nitrate.Reaction of compound 1 with silver salts Silver acetate. Silver acetate (15.2 mg, 0.09 mmol) suspended in acetone (20 cm3) was added to compound 1 (50 mg, 0.09 mmol) and stirred for at least 5 h at room temperature, in the dark. The mixture was centrifuged, the yellow solution decanted and evaporated to dryness. The orange solid was recrystallised from acetone–hexane; yield 58% of 4 identical to that prepared from the thallium(I) salt.Silver nitrate. The nitrate (15.42 mg, 0.09 mmol) in water (10 cm3) was added to compound 1 (50 mg, 0.09 mmol) dropwise, resulting in a green solution. This was centrifuged, then filtered and evaporated to dryness to give green 7. Recrystallisation was unsatisfactory as 7 is extremely hygroscopic (Found: C, 29.46; H, 3.55; N, 5.43. C15H12ClFeN2O4PtS requires C, 29.38; H, 3.63; N, 4.57%). n(Nujol, cm21): 1385 (NO3 2) and 1126 (S]] O). Lmax(H2O) 53.5 W21 cm2 mol21.l/nm(e/M21 cm21) (acetone): 588(364) and 780(515). Other salts. The salt AgX(aq) [X = ClO4 2, NO3 2, SO4 22, BF4 2, PF6 2, ox, or Hmal] was added to compound 1 dissolved in acetone at which point the solutions changed from orange to green giving ferrocenyl derivatives. For non-co-ordinating anions the species produced was 151. Reactions of compound 1 with Pt(dmso)2X2 (X 5 ox or Hmal) The compound [Pt(dmso)2Cl2] (70.0 mg, 0.17 mmol) was dissolved in warm water (10 ml) and added to a solution of silver malonate (52.7 mg, 1.7 mmol) in HNO3 (1 mol dm23, 10 ml).The precipitated AgCl was removed and the solution left overnight during which time further AgCl precipitated. Evaporation of the filtered solution to dryness gave [Pt(dmso)2- (Omal)]. n(Nujol, cm21): 1736 (C]] O) and 1156 (S]] O). This was dissolved in acetone–methanol (2 : 1, 40 ml), 1 (115 mg, 4.7 mmol) added and the solution heated at 50–60 8C in the dark with stirring for three hours.It was then stirred overnight at 20 8C, the resulting pale yellow-orange solution centrifuged and the supernatant liquid evaporated to dryness to give pale yellow crystals of [FeCp(h-C5H4CH2NHMe2)] (Found: C, 50.09; H, 5.95; N, 9.08. C13H18FeN2O3 requires C, 51.00; H, 5.93; N, 9.15%). dH (CDCl3) 2.73 (6 H, CH3); 4.11 (2 H, CH3); 4.20 (5 H, C5H3); and 4.31–4.36 (4 H, C5H4). Similar results were obtained using silver oxalate and with 1 even if a base (e.g. K2CO3) was present in the final step.Preparation of compounds 9–12 Compounds 9 and 11. Compound 1 (0.414 g, 0.75 mmol) was dissolved in 2 ml of rigorously deoxygenated chloroform and added to the sodium salt of tris(m-sulfonatophenyl)phosphine (54.6 mg, 1.50 mmol) in 20 ml degassed distilled water. This solution was sealed under nitrogen and left stirring for 2 h. Once the aqueous layer had reached full orange colouration the water was evaporated and the product immediately (due to very rapid oxidation) chromatographed on a octadecylfunctionalised silica gel reversed-phase column with methanol– water (1 : 2).The solvent was removed and the solid dissolved in hot water, hot methanol added and the solution centrifuged. Removal of solvent and recrystallisation from methanol– acetone gave pure 11 as orange crystals (57%); mp 220 8C (decomp.) (Found: C, 38.21; H, 2.90; Cl, 0.00; N, 0.8; S, 12.13. C49H40FeNNa5O18P2PtS6 requires C, 37.94; H, 2.60; Cl, 0.00; N, 0.90; S, 12.40%) ES-MS: m/z 488 [(M 2 4Na1)2 1 7H1].dH(D2O) 2.72 (s, 3 H, 3JPt–H = 4.6, NCH3), 3.35 (s, 3 H, 3JPt–H = 5.2, NCH3), 4.11 (s, 1 H, one of h5-C5H3Fe), 4.22 (s, 5 H, h5-C5H5Fe), 4.33 (s, 1 H, one of h5-C5H3Fe), 4.38 (s, 1 H, one of h5-C5H3Fe) and 7.34–8.17 [m, 24 H, P(C6H4SO3)3]. dC(D2O) 38.72 (NCH3), 41.35 (NCH3), 57.34 (CH), 69.11 (h5-C5H5Fe), 70.09 (CH), 71.02 (CH) and 126.96–130.23 [P(C6H4SO3)3]. dP(D2O) 5.64 (d, 2JP–P = 18.3, 1JPt–PC = 3128) and 15.91 (d, 2JPt–P = 19.2, 1JPt–PN = 3748 Hz).Also characterised spectroscopically in aged solutions, 9: dp(D2O) 14.68 (s, 1JPt–PN = 3735 Hz, N–Pt–P product only); dPt(D2O) 23259 (d, 1JPt–PN = 4981, 1JPt–PC = 3662 Hz); n(KBr, cm21) 1466 (P–Ph), 993 (P–Ph) and 622 (C–S); lmax/nm (e/M21 cm21) water 480(162), 585(71) and 809(90). Compounds 10 and 12. A similar procedure to that for compound 11 using 3 gave 12 as orange crystals (54%); mp 264 8C (decomp.) Rapid oxidation and hygroscopic character resulted in poor microanalytical data (Found: C, 37.18; H, 3.44; N, 0.77; S, 12.83.C88H70FeN2Na10O36P4Pt2S12 requires C, 36.24; H, 2.40; N, 0.96; S, 13.18%). ES-MS: m/z 913 [(M 2 8Na1)2 1 11H1]. n(KBr, cm21) 621 (C–S). lmax/nm (e/M21 cm21): 407 (534), 504 (257) and 682 (534). dH(D2O) 2.64 (s, 3 H, 3JPt–H = 4.3, NCH3), 2.71 (s, 3 H, 3JPt–H = 4.6, NCH3), 2.88 (s, 3 H, 3JPt–H = 5.3, NCH3), 3.02 (s, 3 H, 3JPt–H = 5.6 Hz, NCH3), 3.92–4.04 (m, 6 H, h5-C5H3Fe) and 7.17–7.97 (m, 48 H, tppms).dC(D2O) 27.90 (NCH3), 38.71 (NCH3), 41.36 (NCH3), 57.86 (NCH3), 71.13 (h5-C5H5Fe), 71.74 (h5-C5H5Fe) and 124.84–143.49(tppms). dP(D2O) 20.29 (d, 2JPt–P = 18.3, 1JPt–PN = 4474) and 24.13 (d, 2JPt–P = 18.3, 1JPt–PC = 2478 Hz). Characterised spectroscopically in aged solutions, 12: dP(D2O) 12.92 (t, 2JP–P = 40.31, 1JPt–PN = 3675 Hz); dPt (D2O) 23258 (d, 1JPt–PN = 4995, 1JPt–PC = 3690).1964 J. Chem. Soc., Dalton Trans., 1999, 1957–1965 Preparation of compounds 13 and 14 Compound 13.Sodium diethyldithiocarbamate (dedtc) (6.4 mg 0.02 mmol) dissolved in 20 ml methanol was added to compound 1 (15.6 mg, 0.02 mmol) dissolved in the minimum volume of degassed chloroform. The solution was stirred for 2 h in the dark and the resulting brown-orange product extracted with hexane. The hexane solution was washed with water to remove the dmso and then solvent removed in vacuo. Chromatography on silica in chloroform removed all remaining impurities and recrystallisation of the residue from hot ethyl acetate gave 13 as orange-yellow crystals (67%); mp 95 8C (decomp.) (Found: C, 37.20; H, 5.14; N, 4.31.C18H26FeN2PtS2?2MeOH requires C, 36.93; H, 4.48; N, 4.79%). ES-MS: m/z 585 (M1). dH(CDCl3) 1.30 (t, 3 H, J = 7.3, CH2CH3), 1.34 (t, 3 H, J = 7.3, CH2CH3), 2.89 (s, 3 H, 3JPt–H = 18.4, NCH3), 3.24 (s, 3 H, 3JPt–H = 16.7, NCH3), 3.67 (q, 2 H, J = 6.9 Hz, CH2CH3), 3.70 (q, 2 H, J = 7.1 Hz, CH2CH3), 3.85 (s, 1 H, h5-C5H3Fe), 4.01 (s, 1 H, h5- C5H3Fe), 4.12 (s, 5 H, h5-C5H5Fe) and 4.23 (s, 1 H, h5-C5H3Fe). dC(CDCl3) 12.48 (CH2CH3)2), 43.94 (CH2CH3), 45.46 (CH2- CH3), 54.00 (CH3N), 54.93 (CH3N), 62.09 (CH, h5-C5H3Fe), 68.75 (CH, h-C5H3Fe), 69.23 (CH, h5-C5H3Fe) and 69.37 (5CH, h5-C5H5Fe).dPt(CDCl3) 21974. n(KBr, cm21): 1442, 1384 (C–N), 1279(C]] S) and 847(C–S). lmax/nm(e/M21 cm21) (CHCl3) 455(330) and 362(860). Compound 14. This was obtained as orange crystals (58%) by a similar route from compound 2; mp 112 8C (decomp.) (Found: C, 34.25; H, 4.41; N, 5.07.C26H42FeN4Pt2S4: C, 34.92; H, 4.30; N, 5.69%). ES-MS: m/z 985 (M1). dH(CDCl3) 1.24 (3 H, J = 9.9 Hz, CH2CH3), 1.27 (3 H, J = 9.9, CH2CH3), 1.28 (3 H, J = 9.4, CH2CH3), 1.30 (3 H, J = 9.3, CH2CH3), 2.87 (3 H, 3JPt–H = 13.8, NCH3), 2.89 (s, 3 H, 3JPt–H = 13.5, NCH3), 3.22 (s, 3 H, 3JPt–H = 16.2, NCH3), 3.24 (s, 3 H, 3JPt–H = 18.1, NCH3), 3.61 (q, 2 H, J = 7.2, CH2CH3), 3.65 (q, 2 H, J = 7.5, CH2CH3), 3.67 (q, 2 H, J = 7.2 Hz, CH2CH3), 3.70 (q, 2 H, J = 7.5 Hz, CH2CH3), 3.99 (2 H, h5-C5H3Fe), 4.04 (5 H, h5-C5H5Fe), 4.07 (2 H, h5-C5H3Fe) and 4.10 (2 H, h5-C5H3Fe).dC(CDCl3) 12.49 (CH2CH3), 12.62 (CH2CH3), 43.81 (CH2CH3), 43.95 (CH2CH3), 45.31 (CH2CH3), 45.43 (CH2CH3), 53.61 (NCH3), 53.85 (NCH3), 54.46 (NCH3), 54.92 (NCH3), 59.08, 59.46, 62.47, 67.13, 68.68 and 70.66 (CH, h5-C5H3)2Fe). dPt (CDCl3) 22227 and 21981. n(KBr, cm21): 1272(C]] S) and 844(C–S). lmax/nm(e/M21 cm21) (CHCl3) 470(75). Crystal structure determination of compound 4 Crystals of compound 4 were grown as yellow plates from acetone–hexane. Data were collected on a Nicolet, R3M dif- Table 3 Crystal data and structure refinement for compound 4 Empirical formula Formula weight T/K l/Å Crystal system Space group a/Å b/Å c/Å b/8 V/Å3 Z Dc/Mg m23 m/mm21 F(000) Crystal size/mm Reflections collected Independent reflections Data/parameters Final R,R9 [I > 2s(I)] Largest diVerence peak and hole/e Å23 C17H27FeNO4PtS 592.40 293(2) 0.71073 Monoclinic P21/c 10.066(2) 15.265(4) 12.997(3) 103.30(2) 1943.5(8) 4 2.025 8.065 1152 0.5 × 0.25 × 0.1 2640 2060 [R(int) = 0.0435] 2060/241 0.0278, 0.0323 0.918 and 21.080 fractometer using the w–2q scan technique.Details of the data collection and structure refinement are summarised in Table 3. The structure was solved by direct methods using SHELXS 86.32 The E map revealed the location of the Pt, Fe and S atoms with the remaining non-hydrogen atoms located in a series of least-squares refinement on F, Fourier diVerence cycles.Weighted refinement was performed using SHELX 76,33 with all non-hydrogen atoms refined anisotropically. A Fourierdi Verence synthesis following the location of all anticipated non-hydrogen atoms revealed electron density that could be sensibly assigned to a solvent water molecule. Inclusion of this in the refinement led to a significant improvement in R but the associated hydrogen atoms were not located.Other hydrogen atoms were included in the refinements as fixed contributions to Fc. CCDC reference number 186/1430. Acknowledgements We thank Professor B. K. Nicholson and Dr. W. Henderson (University of Waikato) for the ES-MS spectra and Professor W. Robinson (University of Canterbury) for the X-ray data collection. B. H. R. thanks Robinson College, Cambridge, for a Bye Fellowship. References 1 R. P. Hanzlik, P. Soine and W. H. Soine, J. Med. Chem., 1979, 22, 424. 2 R.Kalish, T. V. Steppe and A. Wlaser, J. Med. Chem., 1975, 17, 222; J. A. Edwards, R. C. Ursillo and J. E. Hoke, Br. J. Haematol., 1974, 27, 445; J. T. Yarrington, K. W. HuVman, G. A. Leeson, D. J. Syrinkle, D. E. Loudy, C. Hampton, G. J. Wright and J. P. Gipson, Fundam. Appl. Toxicol., 1983, 3, 86. 3 N. P. Buu-Hoi, Hien-Do-Phouc and C. R. Huynh-Trong-Hieu, C. R. Acad. Sci., Ser. D, 1970, 270, 217. 4 E. I. Edwards, R. Epton and G. Marr, J. Organomet. Chem., 1979, 157, 259. 5 M.Schneider and M. Wenzel, J. Labelled Compd. Rad., 1981, 17, 293. 6 R. Tiggemann and M. V. Govidan, Experientia, 1981, 37, 1066. 7 I. Haiduc and C. Silvestru, Organometallics in Cancer Chemotherapy, CRC Press, Boca Raton, FL, 1979; P. Köpf-Maier and H. Köpf, Struct. Bonding (Berlin), 1988, 70, 103; P. Köpf-Maier, H. Köpf and E. W. Neuse, J. Cancer Res. Clin. Oncol., 1984, 107, 336. 8 M. Wenzel and Y. Wu, Appl. Radiat. Isot., 1988, 39, 1237. 9 M. Nicolini (editor), Platinum and Other Coordination Compounds in Cancer Chemotherapy, Martinus NijhoV, Boston, 1988; D.M. Hayes, E. Cvitkovic, R. B. Golbey, E. Scheiner, L. Helson and I. H. KrakoV, Cancer, 1977, 39, 1372; S. J. Lippard, Science, 1982, 217, 1075; J. Reedijk, A. J. M. Fichtinger-Schepman, A. T. Van Oosterom and P. Van de Putte, Struct. Bonding (Berlin), 1987, 57, 53. 10 E. W. Neuse, M. G. Meirim and N. F. Blom, Organometallics, 1988, 7, 2562. 11 N. W. DuVy, J. Harper, P. R. R. Ranatunge-Bandarage, B.H. Robinson and J. Simpson, J. Organomet. Chem., 1998, 554, 125. 12 P. R. R. Ranatunge-Bandarage, B. H. Robinson and J. Simpson, Organometallics, 1994, 13, 500; P. R. R. Ranatunge-Bandarage, N. W. DuVy, S. M. Johnson, B. H. Robinson and J. Simpson, Organometallics, 1994, 13, 511. 13 N. W. DuVy, C. J. McAdam, B. H. Robinson and J. Simpson, Inorg. Chem., 1994, 13, 511. 14 N. W. DuVy, M. Spescha, B. H. Robinson and J. Simpson, Organometallics, 1994, 13, 4895. 15 R. W. Mason, K. McGrouther, P. R. R. Ranatunge-Bandarage, B. H. Robinson and J. Simpson, J. App. Organomet. Chem., 1999, 13, 163. 16 N. Farrell, J. Chem. Soc., Chem. Commun., 1982, 331; P. S. Fontes, Y. Zou and N. Farrell, J. Inorg. Biochem., 1994, 55, 79. 17 J. Blum, A. Rosenfeld, D. Gibson and A. Ramu, Inorg. Chim. Acta, 1992, 201, 219. 18 P. F. Carfagna, S. D. Wyrick, D. J. Holbrook and S. G. Chaney, J. Biochem. Toxicol., 1991, 5, 71; R. S. Dewoskin and J. E. Riviere, Toxicol. Appl. Pharmacol., 1992, 112, 182; P. Francis, M. Markman, T. Haker, B. Reichman, S. Rubin, W. Jones, J. L. Lewis, J. Curtin, R. Barakat, M. Phillips and W. Hoskins, J. Cancer Res. Clin. Oncol.,J. Chem. Soc., Dalton Trans., 1999, 1957–1965 1965 1993, 119, 360; H. Ehrsson, S. Stoneelander, S. Mashashee, A. Andersson, J. O. Thorell and N. Elander, J. High Resolut. Chromatogr., 1994, 17, 283. 19 B. Cornilis and W. A. Herrmann, Applied Homogeneous Catalysis by Organometallic Catalysts, Wiley-VCH, Weinheim, 1998; W. A. Herrmann and C. W. Kohlpainter, Angew. Chem., Int. Ed. Engl., 1993, 32, 1524. 20 V. Scarcia, A. Fulrani, B. Longato, B. Corain and G. Pilloni, Inorg. Chim. Acta, 1988, 153, 67. 21 J. L. Kerr, University of Otago, unpublished results. 22 P. S. Pregosin, Coord. Chem. Rev., 1982, 44, 247. 23 S. O. Dunham, R. D. Lassen and E. H. Abbot, Inorg. Chem., 1991, 30, 4328 and refs. therein; S. E. Miller and D. A. House, Inorg. Chim. Acta, 1991, 177, 125. 24 C. L. Headford, R. Mason, P. R. R. Ranatunge-Bandarage, B. H. Robinson and J. Simpson, J. Chem Soc., Chem. Commun., 1990, 601. 25 C. Matsubayashi, Y. Kondo, T. Tanaka, S. Nishigaki and K. Nakatsu, Chem. Lett., 1979, 375. 26 F. D. Rochon, R. Melanson, J.-P. Macquet, F. Belanger-Gariepy and A. L. Beachamp, Inorg. Chim. Acta, 1985, 107, 17; A. L. Tan, P. M. N. Low, Z.-Y. Zhou, W. Zheng, B.-M. Wu, T. C. W. Mak and T. S. A. Hor, J. Chem. Soc., Dalton Trans., 1996, 2207. 27 Y. S. Sohn, D. N. Henrickson and H. B. Gray, J. Am. Chem. Soc., 1971, 93, 3603; D. Nielson, D. Boone and H. Eyring, J. Phys. Chem., 1972, 75, 511. 28 R. Prins, Chem. Commun., 1970, 280. 29 J. Arpalahti, R. Sillanpaa and M. Mikola, J. Chem. Soc., Dalton. Trans., 1994, 1499. 30 T. G. Appleton, J. R. Hall and P. D. Prenzler, Inorg. Chem., 1990, 29, 3562. 31 G. Brauer, Handbook of Preparative Inorganic Chemistry, 2nd edn., Academic Press, New York, 1963, p. 1. 32 G. M. Sheldrick, SHELXS 86, a program for the solution of crystal structures from diVraction data, University of Göttingen, 1986. 33 G. M. Sheldrick, SHELX 76, a program for crystal structure determination, University of Cambridge, 1976. Paper 9/01260E

ISSN:1477-9226    

DOI:10.1039/a901260e

出版商:RSC    

年代:1999

数据来源: RSC

摘要:

J. Chem. Soc., Dalton Trans., 1998, Pages 1961–1968 1961 DALTON FULL PAPER Crystal engineering via negatively charged O]H? ? ?O2 and chargeassisted C]H‰1 ? ? ?O‰2 hydrogen bonds from the reaction of [Co(Á5-C5H5)2][OH] with polycarboxylic acids § Dario Braga,*,† Alessandro Angeloni, Emilio Tagliavini and Fabrizia Grepioni *,‡ Dipartimento di Chimica G. Ciamician, Università di Bologna, Via Selmi 2, 40126 Bologna, Italy The polycarboxylic acids C6H3(CO2H)3-1,3,5 (trimesic acid, H3tma) and O2,O3-dibenzoyl-L-tartaric acid (L-H2bta) reacted in water or thf with [Co(h5-C5H5)2][OH] prepared in situ by oxidation of [Co(h5-C5H5)2] to generate organic superanions self-assembled via negatively charged O]H? ? ?O2 and neutral O]H? ? ? O hydrogen bonds.The resulting organic host accommodates the cations via charge assisted C]Hd1 ? ? ?Od2 hydrogen bonds between organometallic and organic components. Crystalline [Co(h5-C5H5)2]1[(H3tma)(H2tma)]2?2H2O 1 was obtained as the major product from acid and base in a 1 : 2 stoichiometric ratio.Compound 1 contains a complex hydrogen bonded honeycomb-type structure formed by superanions [(H3tma)(H2tma)]2 and water molecules. The mixed salt [Co(h5-C5H5)2]1[Co(H2O)6]21[tma]32 2 was obtained as a minor product from the same reaction. In crystalline 2 the water molecules of the aqua complex form hydrogen bonds with the three carboxylic groups of the organic anion resulting in a caged structure that encapsulates the [Co(h5-C5H5)2]1 cation. When dibenzoyl-L-tartaric acid was used the chiral crystal [Co(h5-C5H5)2]1[L-Hbta]2 3 is obtained.The crystal contains chains of O]H? ? ?O2 hydrogen bonded anions. These results are used to discuss a design strategy for the engineering of organometallic crystals with predesigned structures. Though on a limited data set, the structure of the elusive crystalline hydrate [Co(h5-C5H5)2]1[OH]2?4H2O 4, which is liquid at ambient temperature, is discussed.Crystal engineering is at the intersection of supramolecular chemistry and materials chemistry. For this reason, the experimental 2 and theoretical 3 generation of desired crystal structures is attracting the interest of an increasing number of research groups. The ultimate goal is that of making crystals with a purpose. This implies the design, synthesis, characterization and utilization of crystalline materials with predefined assembly of molecules and ions that result in useful collective crystalline properties (magnetism,4 conductivity and superconductivity,5 charge transfer,6 NLO applications,7 etc.).The synthesis of crystals containing organic and organometallic molecules or ions is a means to combine within supramolecular aggregates the intra- and inter-molecular bonding features of organic fragments, whether as ligands or free molecules, with the variable valence state and magnetic behavior of transition metal atoms.8 An intelligent choice of the organometallic and organic ‘partners’ allows the rational design of solid materials with predefined arrangements of the component molecules or ions.9,10 In Parts 1 11 and 2 1 of this series of papers we have reported the design, synthesis and structural characterization of organic– organometallic crystals obtained from the paramagnetic cations [Cr(h6-arene)2]1 (arene = benzene or toluene) reacted with cyclohexane-1,3-dione (chd) and from the hydroxide [Co(h5-C5H5)2]1[OH]2 reacted with carboxylic acids.Crystalline aggregates of the type [Cr(h6-C6H6)2]1[(chd)2 2 H]2?2chd and [Cr(h6-C6H5Me)2]1[(chd)2 2 H]2 have been obtained from the former reaction, whereas crystalline products of chemical formulae [Co(h5-C5H5)2]1[(D,L-Hta)(D,L-H2ta)]2 and [Co(h5- C5H5)2]1[L-Hta]2 have been obtained by utilizing D,L-tartaric acid and L-tartaric acid and the cobaltocenium cation. The structural prerequisites of the organic acidic species are the presence of strong donor/acceptor hydrogen bonding groups and a number of acceptor sites larger than the number † E-Mail: dbraga@ciam.unibo.it; http://catullo.ciam.unibo.it ‡ E-Mail: grepioni@ciam.unibo.it; http://catullo.ciam.unibo.it § Organic-organometallic crystal synthesis.Part 3. of donor sites. The organometallic partners, on the other hand, must not possess strong hydrogen bonding donor/acceptor systems which may compete with the organic fragments, but rather a large number of acidic Csp]H groups in the arene and cyclopentadienyl ligands.This is necessary to drive the acid selectively to self-assemble into large hydrogen bonded superanions which can then interact with the organometallic system via charge assisted C]Hd1 ? ? ?Od2 bonds. The importance of charge assistance in the reinforcement of weak hydrogen bonds such as C]Hd1 ? ? ?Od2, but also C]Hd1 ? ? ?Fd2 (when fluorine is part of inorganic anions such as PF6 2 and BF4 2) and C]Hd1 ? ? ?pd2 (when the p system of alkynes, alkenes and aromatic carbocycles belongs to organometallic anions), in organometallic crystal chemistry has been assessed and discussed.12 In this paper we have taken our strategy to the polycarboxylic acids benzene-1,3,5-tricarboxylic acid (trimesic acid, H3tma) and O2,O3-dibenzoyl-L-tartaric acid (L-H2bta) and investigated the preparation of new organo–organometallic solids by reaction of the acids with [Co(h5-C5H5)2]1[OH]2.The structure of the crystalline hydrated hydroxide [Co(h5-C5H5)2]1[OH]2?3H2O is discussed.Experimental Crystal synthesis As in the cases discussed in Parts 1 and 2, the synthetic aspect of this work is related to the synthesis and crystallization of solid materials. All reagents were commonly available organic and organometallic substances. [Co(Á5-C5H5)2]1[(H3tma)(H2tma)]2 1, [Co(Á5-C5H5)2]1[Co- (H2O)6]21[tma]32 2, [Co(Á5-C5H5)2]1[L-Hbta]2 3 and [Co(Á5- C5H5)2]1[OH]2?4H2O 4. Brown powder of [Co(C5H5)2] (100 mg, 0.53 mmol) was suspended in bidistilled water (20 cm3) with stirring at room temperature.Oxygen was bubbled until a clear solution of bright yellow [Co(C5H5)2]1[OH]2 (pH of the solution >10) was obtained. White powder of benzene-1,3,5-1962 J. Chem. Soc., Dalton Trans., 1998, Pages 1961–1968 tricarboxylic acid (H3tma) (56 mg, 0.26 mmol) was mixed with cobaltocenium hydroxide (5 cm3, 0.13 mmol) to obtain in almost quantitative yield bright yellow crystals of complex 1 after evaporation of water at room temperature in the air.Among the yellow crystals, however, a few well shaped light orange crystals were also found. These were later identified as 2. Crystals of complex 3 were obtained in the same way as those of 1 by mixing a basic solution of [Co(C5H5)2]1[OH]2 (5 cm3, 0.13 mmol) with white powder of L-O2,O3-dibenzoyltartaric acid (L-H2bta) (46.5 mg, 0.13 mmol) followed by evaporation of water at room temperature in the air.The reaction to produce 3 gave almost quantitative yield. Benzene-1,3,5-tricarboxylic acid, L-O2,O3-dibenzoyltartaric acid and cobaltocene were from Aldrich. Compound 4 was obtained by evaporation of the bright yellow solution resulting from prolonged stirring in the air of a suspension of brown powder of [Co(C5H5)2] (100 mg, 0.53 mmol) in bidistilled water (20 cm3). Tetrahydrofuran was distilled from sodium–benzophenone and stored under argon. Crystallography All X-ray diVraction data collections were carried out on a Nonius CAD-4 diVractometer equipped with an Oxford Cryostream liquid-N2 device.Crystal data and details of measurements are reported in Table 1. DiVraction data were corrected for absorption by azimuthal scanning of high-c reflections. The programs SHELXS 8613a and SHELXL 9213b were used for structure solution and refinement based on F2; SCHAKAL 9213c was used for the graphical representation of the results. Common to all compounds: Mo-Ka radiation, l = 0.710 69 Å, graphite monochromator.All non-H atoms, except for the O atoms in 4, were refined anisotropically. The positions of all hydrogen atoms in 1, of the water hydrogens in 2, and of the carboxylic hydrogen atoms in 3 have been observed in the Fourier maps. The remaining H atoms bound to C atoms were added in calculated positions in 2, 3 and 4. The computer program PLATON13d was used to analyze the geometry of the hydrogen bonding patterns.In order to evaluate C]H? ? ? O bonds the C]H distances were normalized to the neutron derived value of 1.08 Å. In 2 the C5H5 ligands were found to be disordered over two sites of occupancy ratio 1 : 1. The water molecules and the OH groups in crystals of compound 4 are aVected by disorder. There are five independent oxygen atoms in the hydrogen bond network. Two of these oxygens are disordered over two positions with equal occupancy related by a centre of inversion (O4) and a two-fold axis (O6), whereas O1, O2 and O3 are close to a crystallographic two-fold axis and form almost flat hexagons interconnected via atom O5 in general position.The very large thermal motion of the oxygen atoms perpendicular to the hexagon plane is a clear indication that the hexagonal six-water systems are puckered as usually observed in water clathrates and in the structure of ice and that the flat hexagon results as an average of the oxygen atoms displaced above and below the ring.As mentioned above, all attempts to obtain better behaving crystalline material have failed. Crystals of 4 are only formed at low temperature by slow evaporation and cooling of the solution. This procedure often results in an enamel-like material covering the surface of the container from which solid particles were obtained and used for measurement at low temperature. CCDC reference number 186/976. Results and Discussion As described in Part 2 of this series,1 the crystal synthesis is based on a direct acid–base reaction followed by self-assembly of the partially deprotonated organic acids into organic superanions which then host the organometallic cations in cavities or channels.Crystalline compounds 1, 2 and 3 have been obtained in three steps: (i) oxidation of cobaltocene to the cobaltocenium cation and consequent formation of a basic solution as the final product of oxygen reduction in solution is the OH2 anion (see below), (ii) acid–base reaction between [Co(C5H5)2][OH] and the organic acid and (iii) precipitation of the crystalline aggregate.The preparation can be carried out in water or thf but, while in water the hydroxide [Co(C5H5)2][OH] can be prepared first and then treated with the organic acid, in thf the oxidation must occur in the presence of the organic acid. In both cases the oxidant is molecular oxygen and the oxidation is indicated by the bright yellow color of the solution due to the presence of cobaltocenium cation.Though simple it may appear, the formation of the desired product depends not only on the diVerence in solubility in water or thf between the organic acid and the organic– organometallic aggregate, but also on the acid–base equilibria controlling first, second (and third in the case of trimesic acid) deprotonations of the polycarboxylic acid. The crystallization conditions are also diVerent: while crystals from water are obtained by slow evaporation of the reaction mixture, crystallization from thf never gives crystalline products but only powder materials.It is necessary to solubilize the precipitates in water and allow recrystallization. The precipitation from thf is somewhat cleaner than that from water as unchanged cobaltocene may remain in solution. Structural characterization Relevant intramolecular and intermolecular bonding parameters are reported in Tables 2 and 3, respectively. For clarity the following conventional description of hydrogen bonding structural parameters has been adopted: X(H) ? ? ? O (X = C, O) indicates the distance between a donor C or O atom and acceptor O atom, (X)H ? ? ? O the distance between a donor hydrogen atom bound to X and acceptor, while X]H? ? ? O indicates the angle.Crystalline [Co(h5-C5H5)2]1[(H3tma)(H2tma)]2?2H2O 1 represents the first example of an organometallic salt of trimesic acid. Trimesic acid 14a is a kind of prototypical system in crystal engineering studies.Thanks to the highly symmetrical distribution of the three carboxylic groups, trimesic acid should, in principle, be able to form a very stable two-dimensional hydrogen bond network by in plane arrangement of molecules. This is not so, and the pure organic material forms pseudo-catenane structures by interpenetration of condensed six-molecule hydrogen bonded rings. One hydrated form of trimesic acid is also known.14b A few cocrystals have also been obtained.15 Crystalline salts of trimesic acid as well as co-ordination compounds in which the carboxylic groups bind to metal atoms are also known.16 The salient structural features of crystalline compound 1 can be summarized as follows.(i) There are two units derived from trimesic acid forming a dimeric superanion of formula [(H3tma)(H2tma)]2 from which only one acidic proton has been removed. The superanion is held together by a strong negative hydrogen bond between one CO2H system of one formally neutral acid molecule and the deprotonated CO2 unit from a formally anionic [H2tma]2 system [see A in Fig. 1(a)]. (ii) The [H3tma] 1 [H2tma]2 description can only be formal and approximate as the ‘inter-trimesic’ hydrogen atom is shared between the two trimesic acid units, so that the organic repeating unit is more correctly described as formed by a deprotonated dimeric system of two trimesic acid moieties. (iii) This basic unit is left with a grand total of four CO2H groups to employ in hydrogen bonding systems with the surrounding anions; this is done with the intermediacy of two water molecules which appear to play a crucial role in the stabilization of the hydrogen bond network.(iv) The water molecules bridge pairs of CO2H units by forming 10-atom rings via insertion of one OwH group within the carboxylic ring [B in Fig. 1(a)], while the other OwH group of the same water molecules links the free oxygen atoms on theJ. Chem.Soc., Dalton Trans., 1998, Pages 1961–1968 1963 Table 1 Crystal data and details of measurements for compounds 1, 2, 3 and 4 Formula MT /K System Space group a/Å b/Å c/Å a/8 b/8 g/8 U/Å3 Z Minimum, maximum transmission m(Mo-Ka)/mm21 Measured reflections Unique reflections Unique reflections [I > 2s(I)] Goodness of fit on F2 R1 [on F, I > 2s(I)] wR2 (on F2, all data) 1 C28H25CoO14 644.41 223(2) Triclinic P1� 7.874(4) 8.964(9) 10.967(9) 97.92(8) 107.44(6) 110.84(7) 644(1) 1 0.83, 1.00 0.724 2603 2450 1726 1.035 0.0341 0.1362 2 C19H25Co2O12 563.24 223(3) Monoclinic C2/c 11.058(4) 19.393(8) 10.880(10) 101.97(6) 2283(2) 4 0.74, 1.00 1.515 2121 1994 807 0.974 0.0628 0.1815 3 C28H23CoO8 546.39 223(2) Orthorhombic P212121 10.522(10) 13.053(6) 17.58(1) 2414(3) 4 0.81, 1.00 0.763 1938 1917 1229 0.997 0.0440 0.1344 4 C10H19CoO5 277.93 253(2) Monoclinic C2/c 22.28(2) 8.805(9) 13.81(1) 101.55(9) 2654(4) 8 0.77, 1.00 1.25 1837 1602 892 0.897 0.1055 0.3559 deprotonated inter-trimesic CO2]H]O2C system. In such a way, although the ions and molecules depicted in Fig. 1(a) do actually lie almost coplanar, the water molecules propagate the structure in the third dimension by expanding to layers above and below the reference plane. This is easy to appreciate from Fig. 1(b). The benzene rings lie flat on the next layer at a graphitic distance of 3.30 Å. This arrangement recalls closely that observed in crystals of trimesic acid. (v) Hydrogen bonding distances grouped in Table 3 are comparable to those formed by other negative OCO2H ? ? ?OCO2 and neutral OCO2H ? ? ?OCO2H hydrogen bonds.1,11 (vi) The distribution of trimesic acid moieties and water molecules results in a large anionic organic superstructure Fig. 1 (a) Ball and stick representation of the hydrogen bonding patterns in crystalline compound 1 showing the complex mixing of negatively charged hydrogen bonds between the two trimesic acid units (A) and the hydrogen bonds involving the water molecules forming 10- atom rings via insertion of one OH group within the carboxylic ring (B).(b) The water hydrogen bonds propagate the structure in the third dimension forming layers of trimesic acid anions (H atoms omitted for clarity) which folds around the cobtocenium cations as shown in Fig. 2(a). A view of the whole three-dimensional organic superanion is shown in Fig. 2(b). Note the honeycomb type structure with channels extending along the a axis, reminiscent of the superstructures obtained from D,L- and L-tartaric acid.1 Fig. 2 (a) Space filling representation of the anionic organic superstructure folding around the cobaltocenium cation in crystalline compound 1. (b) The honeycomb type anionic organic superstructure formed by trimesic acid and water molecules1964 J. Chem. Soc., Dalton Trans., 1998, Pages 1961–1968 Table 2 Relevant bonding distances (Å) for compounds 1, 2 and 3a 2 b 4 c Co]C 1 2.022(4) 2.013(5) 2.016(5) 2.022(5) 2.022(4) A 2.03(2) 2.04(2) 2.03(2) 2.02(2) 2.02(2) B 2.11(2) 2.09(2) 2.02(2) 1.98(2) 2.04(2) 3 2.010(7) 2.017(8) 2.020(7) 2.022(7) 2.024(7) 2.029(7) 2.036(7) 2.032(7) 2.039(7) 2.035(7) a 2.029(11) 2.020(11) 2.004(11) 2.004(11) 2.019(12) b 2.017(9) 2.035(9) 2.040(8) 2.024(8) 2.010(8) mean Co]O C]C in C5H5 mean 2.0194 1.396(7) 1.409(6) 1.403(7) 1.402(7) 1.403(7) 1.4034 2.044 2.081(6) 2.063(6) 2.104(6) 1.42 d 2.0269 1.42 d 2.0159 1.42 d tma mean Cring]Cring mean CPh]CCO2 mean C]O mean C]] O 1.3904 1.4986 1.29818 1.21411 1.3837 1.50911 1.25411 e bta mean C]Cchain mean C]CPh mean C]O mean C]Obenzoyl mean C]] O 1.53823 1.4624 1.2721 1.34915 1.20110 a Estimated standard deviations on the mean values are given as subscripts.b A and B are the two disordered images of the C5H5 ring (occupancy factor 0.5 for both images). c Two half independent cations in the asymmetric unit. d C5H5 rings defined as rigid groups. e The C]O and C]] O groups are not distinguishable on the basis of bond distances.The cobaltocenium cations are accommodated within the channels. (vii) The interaction between the cobaltocenium cations and the organic framework is based on charge assisted C]Hd1 ? ? ?Od2 hydrogen bonds between the positively charged CH groups of the cations and the oxygen atom lone pairs left ‘free’ by the stronger hydrogen bonded network with carboxylic groups or water molecules (see Table 3). Crystalline [Co(h5-C5H5)2]1[Co(H2O)6]21[tma]32 2 can only be obtained as a minor product accompanying the preparation Table 3 Relevant intermolecular hydrogen bonding parameters in crystalline compounds 1, 2 and 3 (distances in Å, angles in 8) Interaction type O? ? ? (H) ? ? ?O2 O(H) ? ? ?O O? ? ?Ow (C)Hd1 ? ? ?Od2 < 2.6 C]Hd1 ? ? ?Od2 (C)Hd1 ? ? ?Ow < 2.6 C]H? ? ?Ow 1 2.448 2.609 2.567 2.887 2.769 2.529 2.548 2.473 140.32 141.66 127.91 2 2.656 2.777 2.666 2.532 a 2.527 a 2.382 b 143.50 a 145.60 a 150.58 b 2.397 a 2.519 b 152.90 a 164.27 b 2.729 2.745 2.771 3 2.415 2.299 2.343 2.484 2.516 136.17 133.48 148.40 129.34 2.556 2.496 2.487 2.367 139.95 155.76 124.95 163.60 a Interaction involving ring A.b Interaction involving ring B. of 1 in water. Its formation is very likely due to decomposition of the cobaltocene or of the cobaltocenium cation upon reaction with the acid. Although admittedly serendipitous, the formation and stability of such a crystalline aggregate indicate the possibility of forming even more complex crystals by cocrystallization of diVerent ions.Strictly speaking, crystalline 2 is an example of organic–inorganic–organometallic cocrystallization. The most relevant structural features are as follows. (i) The crystal is formed by hexaaquacobalt(II) cations [Co(H2O)6]21 which co-crystallize together with cobaltocenium cations and one fully deprotonated trimesic acid unit per formula, e.g. corresponding to the formula [Co(h5-C5H5)2]1- [Co(H2O)6]21[tma]32.The aqua complex shows three independent Co]O distances of length 2.081(6), 2.063(6) and 2.104(6) Å. (ii) To our knowledge this is the first example of a fully deprotonated trimesate [tma]32 anion; salts of this anion have not been observed before, all the other examples being derived from partially deprotonated acid molecules.16 (iii) DiVraction data were of suYcient quality to allow location of all water hydrogen atoms. The knowledge of these atomic positions permits a clear understanding of the hydrogen bonds linking the anions and cations, as well as the two types of cations.(iv) Fig. 3 shows how the trimesate anions interact with the aqua complexes with each oxygen atom taking part in a bifurcated interaction with two water molecules co-ordinated to two cations. (v) The [Co(H2O)6]21 cations are arranged in columns through the crystal architecture as shown in Fig. 4. Each [Co(H2O)6]21 column is completely surrounded by six columns formed by an A/B/A/B stacking of [Co(h5-C5H5)2]1 cations intercalated between the benzene rings of the trimesic acid anions [see Fig. 5(a)]. The distance between the cyclopentadienyl planes and those of the C6 rings ranges from 3.4 to 3.8 Å. (vi) The {[Co(h5-C5H5)2]1[tma]32}n columns are arranged soJ. Chem. Soc., Dalton Trans., 1998, Pages 1961–1968 1965 that each [Co(h5-C5H5)2]1 cation of one column is eVectively embraced by three trimesate anions of neighboring columns [see Fig. 5(b)]. (vii) The C]H? ? ? O hydrogen bonds are formed between the C]H groups of the cyclopentadienyl ligands and the water or trimesic acid moieties. The cyclopentadienyl ligands are disordered over two orientations of identical occupancy (see Experimental section). Both orientations allow C]H? ? ?O hydrogen bonds to be established in almost equal number and distribution of C]H? ? ? O lengths so that the orientation of the C5H5 ligand is indiVerent for crystal cohesion.The dibenzoyl-L-tartaric acid derivative 3 will now be discussed. Although the stoichiometry is much simpler than that of 1 and 2 and the crystal architecture less striking, 3 is somewhat more interesting because the crystal is chiral in space group P212121 (see Experimental section). This was to be expected as the starting material is enantiomerically pure dibenzoyl-L-tartaric acid. No water of crystallization is present. The use of enantiomerically pure chiral acids is at the basis of the development of our crystal engineering strategy.As mentioned in the introduction our scope is that of gaining control over the crystallization of chiral materials with the objective of introducing dipolar organometallic molecules (which, of course is not the case of the cobaltocenium cation!) for optoelectronic applications. However, crystallization of chiral objects in a non-centrosymmetric space group is generally more diYcult than that of racemic mixtures or of non-chiral molecules. We Fig. 3 The trimesate anions in crystalline [Co(h5-C5H5)2]1- [Co(H2O)6]21[tma]32 2 interact directly with the [Co(H2O)6]21 cations, each oxygen atom taking part in a bifurcated interaction Fig. 4 The [Co(H2O)6]21 cations are arranged in columns through the crystal and completely surrounded by piles of alternating [Co(h5- C5H5)2]1 and [tma]32 ions. Only H(water) atoms are shown for clarity have previously succeeded only with L-tartaric and dibenzoyl-Ltartaric acids, but in this latter case only via the serendipitous isolation of an (extremely interesting though) undecahydrate crystalline material obtained from complete deprotonation of the L-H2bta acid.1 The existence of compound 3 now demonstrates that it is possible to obtain a chiral crystal of L-H2bta without water molecules.The important characteristics of 3 can be summarized as follows. (i) The acid is deprotonated only once, i.e. one CO2H group remains untouched whereas the second one forms the carboxylate system CO2 2 which becomes a strong hydrogen bond acceptor.(ii) The L-Hbta anions are linked in chains through the crystal by CO2]H]O2C interactions [see Fig. 6(a)]. Contrary to 1, the hydrogen atom position along this bond has not been observed and the hydrogen bond feature needs to be judged from the O ? ? ? O distance which is 2.415 Å, i.e. towards the shortest values for negatively charged hydrogen bonds of this type (see Table 3).(iii) The (L-Hbta2)n anionic chains have no means to interlink via hydrogen bonds as the only available hydrogen atom is used along the chain. Small channels, generated along the a axis [see Fig. 6(b)], accommodate a snake-like arrangement of cobaltocenium cations [see Fig. 7(a)]. The resulting packing arrangement is shown in Fig. 7(b). Although the dibenzoyl-L-tartaric acid is very bulky compared with the cobaltocenium cation the flexibility of the tartaric acid skeleton allows folding about the cations and eYcient packing. (v) As observed in all previous cases, the interaction between the organometallic guest and the large organic host is based on charge assisted C]Hd1 ? ? ?Od2 interactions (there are eight Fig. 5 (a) Each [Co(H2O)6]21 column in crystalline 2 is completely surrounded by six columns formed by an A/B/A/B stacking of [Co- (h5-C5H5)2]1 cations sandwiched between trimesic acid anions. (b) Each [Co(h5-C5H5)2]1 cation of one {[Co(h5-C5H5)2]1[tma]32}n column is embraced by three trimesate anions of neighboring columns1966 J.Chem. Soc., Dalton Trans., 1998, Pages 1961–1968 H? ? ? O distances in the range 2.299–2.496 Å, three of which are shorter than 2.370 Å. The C]H? ? ? O distances involving phenyl hydrogens of the organic anions are in general longer. It is worth recalling that, contrary to compound 3, in the crystalline material 2[Co(h5-C5H5)2]1[L-bta]22?11H2O11 the acid was completely deprotonated, hence no hydrogen bonding donor group was available to cope with the presence of twelve potential hydrogen bonding acceptor sites.In that compound the eleven water molecules appear to play a twofold function: Fig. 6 (a) The L-Hbta2 anions in crystalline compound 3 are linked in chains through the crystal by CO2]H]O2C interactions. (b) Space filling representation of the organic chains. Note that small channels are generated in which the cobaltocenium cations are accommodated.Hydrogen atoms are omitted for clarity Fig. 7 (a) The snake-like arrangement of the cobaltocenium cations in crystalline compound 3. (b) Space filling representation of the overall packing arrangement. Hydrogen atoms are omitted for clarity they fill space eYciently, but also, and more importantly, they provide a large number of O]H donor groups to stabilize the crystal structure. Based on this consideration it is interesting to consider the role of water in crystalline 2, which, is the undecahydrate crystal,11 contains only fully deprotonated anions derived from the organic acid and six water molecules, though co-ordinated to the cobalt(II) center.One may speculate that, though co-ordinated to the Co21 cations, the water molecules play the same role of compensation towards a highly unbalanced hydrogen bonding donor/acceptor ratio. Finally, the crystal structure of the hydrated hydroxide [Co(h5-C5H5)2]1[OH]2?4H2O 4 will be described.As mentioned in the Experimental section, this crystalline material is easy to prepare but crystals suitable for X-ray diVraction are very hard to get. It seems that the hydroxide solidifies with a variable number of water molecules at a temperature around 0 8C. While solid materials can, of course, always be obtained by decreasing the temperature, only in four distinct cases small fragments with some diVracting power could be rescued from the solid mass. In all four cases the number of observed reflections is far from desirable, and only in two cases the same unit cell could be attributed and the structure solved.Here we discuss the best results of such eVorts, with the awareness that some reader (or referee) may object to the reporting of diVraction data of low quality. The crystalline hydroxide is however extremely interesting. It is worth stressing, that, after the bis(benzene)chromium species [Cr(h6-C6H6)2]1[OH]2?3H2O,11 crystalline 4 is only the second case of an organometallic sandwich complex hydroxide to be structurally characterized.As in the case of the chromium complex, the [OH]2 groups are indistinguishable from the water molecules. The [OH]2? 4H2O system forms a three-dimensional structure that closely resembles some of the structural types obtained with polycarboxylic acids [see Fig. 8(a)]. The oxygen atoms form zigzagged chains of disordered hexagonal rings (see Experimental section for a description of the disorder) interconnected via two oxygen atoms disordered over two positions (O4 and O6) and the one in general position (O5).This disordered arrangement is shown schematically in Fig. 8(b). A space filling representation of how the water/OH2 hydrogen bonded superstructure hosts the cobaltocenium cations is shown in Fig. 8(c). Conclusion and Perspectives With this study we have demonstrated that common polycarboxylic organic acids can be used to construct complex chiral and achiral organic superstructures by ‘forcing’ selfassembly of the organic moieties via strong hydrogen bonds between carboxylic or carboxylate groups.This can easily be achieved by partially deprotonating the organic acid with a base whose conjugate acid is unable to interact directly with the carboxylate groups, as would otherwise be the case if an alkali or an alkaline earth metal had been used. The organometallic cations obtained from [Cr(h6-C6H6)2] and from [Co(h5- C5H5)2] are well suited for this purpose; the latter has been used in Part 2 and in this work.The oxidation of both sandwich complexes is spontaneous in the presence of oxygen in water, tetrahydrofuran or nitromethane solutions and leads to the simultaneous formation of the hydroxide anion to deprotonate the acid and of the cations for crystallization of the organic– organometallic aggregate. The deprotonation generates negatively charged OCO2H ? ? ? OCO2- hydrogen bonds that constitute a robust backbone for the three-dimensional aggregation of the organic fragments.Negatively charged bonds are amongst the strongest hydrogen bonds and have been shown to possess dissociation energies in the range 60–120 kJ mol21,17 hence they are very well suited for the construction of robust hydrogen bonded frameworks. The O ? ? ? O distances involving the negatively charge assisted hydrogen bond present in crystalline 1 and 3 are comparable toJ.Chem. Soc., Dalton Trans., 1998, Pages 1961–1968 1967 the values observed in the cyclohexanedione derivatives of [Cr(h6-C6H6)2]1 and in the derivatives of tartaric acid reported in Parts 1 and 2. The second design criterion is based on the possibility of taking advantage of the abundance of weakly polarized C]H groups present on the cyclopentadienyl ligands. These ligands have been shown to be able to participate in weak hydrogen bonds of the C]H? ? ? O type when suitable acceptors are present in the crystals.18 These interactions are strengthened when the acceptor atom belongs to an anionic system and the ligand Fig. 8 (a) Space filling arrangement of the water molecules in crystalline compound 4. (b) Schematic representation of the disordered hexagons of water molecules. (c) Space filling representation of the overall packing in the hydroxide [Co(h5-C5H5)2]1[OH]2?4H2O belongs to a cationic complex. The ‘charge assistance’ is reflected in an appreciable decrease of the C]H? ? ? O distances with respect to the values commonly observed with neutral species.Similar approaches have been developed in the organic crystal engineering field. For example, L-malic acid and substituted benzylamines have been employed by Aakeroy and Nieuwenhuyzen 19 to prepare ionic materials via hydrogen bonding interactions of the O]H? ? ? O type between the deprotonated acid and of the N]H? ? ? O type between anions and cations. The strategy adopted by Hosseini et al.20 to build one-, two- and three-dimensional networks in mixed organic crystals is also based on the interaction between acids and bases.In both cases, however, the building blocks are chosen so that there is preferential hydrogen bond formation between anions and cations rather than forced self-assembly of the organic part. The use of electrostatic interactions to template and sustain crystalline aggregates with predefined arrangements of the ionic components has also been exploited by Ward and co-workers 21 to prepare crystalline materials for charge transfer applications and caged structures in which molecules could be trapped.Trimesic acid appears to be a versatile building block in organic–organometallic crystal engineering. Species 1 and 2 demonstrate that it is possible to achieve a progressive deprotonation of the acid, which, in turn, allows one to vary the number of acceptor sites on the organic moiety and the interaction with other hydrogen bond donors.The structure of 3 demonstrates that the use of enantiomerically pure derivatives of L-tartaric acid is a viable and easy route to chiral crystals. Work is in progress to isolate and characterize other crystalline aggregates based on the utilization of chiral acids including natural amino acids, and of other organometallic molecules and ions. We will also investigate the possibility of using organometallic acids as hydrogen bond ‘carriers’ to be employed with organic bases.Acknowledgements Financial support by Minístero dell’Università e della Ricerca Scientifica e Tecnologica and by the University of Bologna (projects: Intelligent Molecules and Molecular Aggregates and Advanced Materials) is acknowledged. We thank Professor F. Calderazzo for useful discussions. References 1 Part 2, D. Braga, A. Angeloni, F. Grepioni and E. Tagliavini, Organometallics, 1997, 16, 5478. 2 D. Braga and F. Grepioni, Chem. Commun., 1996, 571; J.Hulliger, Angew. Chem., Int. Ed. Engl., 1994, 33, 143; C. L. Bowes and G. A. Ozin, Adv. Mater., 1986, 8, 13; G. A. Ozin, Acc. Chem. Res., 1997, 30, 17; M. J. Zaworotko, Nature (London), 1997, 386, 220; O. M. Yaghi, L. Guangming and H. Li, Nature (London), 1995, 378, 703; P. Ball, Nature (London), 1996, 381, 648. 3 A. Gavezzotti, Acc. Chem. Res., 1994, 27, 309; H. R. Karfunkel and R. J. Gdanitz, J. Comput. Chem., 1992, 13, 1171; R. J. Gdanitz, Chem. Phys. Lett., 1992, 190, 391; S.J. Maginn, Acta Crystallogr., Sect. A, 1996, 52, C79; Theoretical Aspects and Computational Modeling of the Molecular Solid State, ed. A. Gavezzotti, Wiley, Chichester, 1997. 4 O. Khan, Molecular Magnetism, VCH, New York, 1993; D. Gatteschi, Adv. Mater., 1994, 6, 635. 5 J. M. Williams, H. H. Wang, T. J. Emge, U. Geiser, M. A. Beno, P. C. W. Leung, K. Douglas Carson, R. J. Thorn, A. J. Schultz and M. Whangbo, Prog. Inorg. Chem., 1987, 35, 218; J. M. Williams, J.R. Ferraro, R. J. Thorn, K. D. Carlson, U. Geiser, H.-H. Wang, A. M. Kini and M.-H. Whangbo, Organic Superconductors, (including Fullerenes): Syntheses, Structure, Properties and Theory, Prentice Hall, Englewood CliVs, NJ, 1992. 6 J. S. Miller and A. J. Epstein, Angew. Chem., Int. Ed. Engl., 1994, 33, 385; Chem. Eng. News, 1995, 73; 30. 7 S. R. Marder, Inorg. Mater., 1992, 115; N. J. Long, Angew. Chem., Int. Ed. Engl., 1995, 34, 21; T. J. Marks and M. A. Ratner, Angew.Chem., Int. Ed. Engl., 1995, 34, 155; D. R. Kanis, M. A. Ratner and T. J. Marks, Chem. Rev., 1994, 94, 195.1968 J. Chem. Soc., Dalton Trans., 1998, Pages 1961–1968 8 P. J. Fagan and M. D. Ward, The Crystal as a Supramolecular Entity. Perspectives in Supramolecular Chemistry, ed. G. R. Desiraju, Wiley, Chichester, 1996, vol. 2, p. 107. 9 D. Braga and F. Grepioni, Acc. Chem. Res., 1994, 27, 51; Coord. Chem. Rev., in the press. 10 G. R. Desiraju, Angew. Chem., Int. Ed. Engl., 1995, 34, 2311; A.D. Burrows, C.-W. Chan, M. M. Chowdry, J. E. McGrady and D. M. P. Mingos, Chem. Soc. Rev., 1995, 329. 11 D. Braga, A. L. Costa, F. Grepioni, L. Scaccianoce and E. Tagliavini, Organometallics, 1996, 15, 1084. 12 D. Braga and F. Grepioni, Acc. Chem. Res., 1997, 30, 81; Current Challenges on Large Supramolecular Assemblies, ed. G. Tsoucaris, Kluwer, Dordrecht, 1998, in the press; D. Braga, G. Cojazzi, F. Grepioni, N. Scully and S. M. Draper, Organometallics, 1998, 17, 296. 13 (a) G. M. Sheldrick, Acta Crystallogr., Sect. A, 1990, 46, 467; (b) G. M. Sheldrick, SHELXL 92, Program for Crystal Structure Determination, University of Göttingen, 1993; (c) E. Keller, SCHAKAL 92, Graphical Representation of Molecular Models, University of Freiburg, 1993; (d ) A. L. Spek, Acta Crystallogr., Sect. A, 1990, 46, C31. 14 (a) D. J. Duchamp and R. E. Marsh, Acta Crystallogr., Sect. B, 1969, 25, 5; (b) F. H. Herbstein and R. E. Marsh, Acta Crystallogr., Sect. B, 1977, 33, 2358. 15 See, for example, F. H. Herbstein and M. Kapon, Acta Crystallogr., Sect. B, 1978, 34, 1608; F. H. Herbstein, M. Kapon and G. M. Reisner, J. Inclusion Phenom., 1987, 5, 211; F. H. Herbstein, M. Kapon, I. Maor and G. M. Reisner, Acta Crystallogr., Sect. B, 1981, 37, 136. 16 See, for example, F. H. Herbstein and M. Kapon, Acta Crystallogr., Sect. B, 1979, 35, 1614; H. Oshio and H. Ichida, J. Phys. Chem., 1995, 99, 3294; O. M. Yaghi, L. Guangming and L. Hailian, Nature (London), 1995, 14, 378. 17 M. Meot-Ner (Mautner), J. Am. Chem. Soc., 1984, 106, 1257; M. Meot-Ner (Mautner) and L. W. Sieck, J. Am. Chem. Soc., 1986, 108, 7525. 18 D. Braga, F. Grepioni, K. Biradha, V. R. Pedireddi and G. R. Desiraju, J. Am. Chem. Soc., 1995, 117, 3156. 19 C. B. Aakeroy and M. Nieuwenhuyzen, J. Am. Chem. Soc., 1994, 116, 10 983; J. Mol. Struct., 1996, 374, 223. 20 M. W. Hosseini, R. Ruppert, P. SchaeVer, A. De Cian, N. Kyritsakas and J. Fisher, J. Chem. Soc., Chem. Commun., 1994, 2135; O. Félix, M. W. Hosseini, A. De Cian and J. Fisher, Tetrahedron Lett., 1997, 38, 1933 and refs. therein; G. Brand, M. W. Hosseini, R. Ruppert, A. De Cian, J. Fisher and N. Kyritsakas, New J. Chem., 1995, 19, 9; O. Félix, M. W. Hosseini, A. De Cian and J. Fisher, Angew. Chem., Int. Ed. Engl., 1997, 36, 102. 21 V. A. Russell, C. C. Evans, W. Li and M. D. Ward, Science, 1997, 276, 575. Received 3rd February 1998; Paper 8/00914G

ISSN:1477-9226    

DOI:10.1039/a800914g

出版商:RSC    

年代:1998

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DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1999, 1967–1974 1967 Synthesis and crystal structure of the 16 e2 cationic tungsten(IV) complex [WCp*(4,49-Me2bipy)Cl2]1BPh4 2† Christian Cremer and Peter Burger * Anorganisch-chemisches Institut der Universität Zürich, Winterthurerstr. 190, 8057 Zürich, Switzerland. E-mail: chburger@aci.unizh.ch Received 16th December 1998, Accepted 23rd April 1999 A general synthetic route to electron rich half-sandwich tungsten(IV) complexes with a series of 4,49-disubstituted 2,29-bipyridyl (R2bipy) donor ligands of the type [WIVCp*(R2bipy)Cl3] has been elaborated.The crystal structure and conductivity measurements of the R = methyl derivative evidenced quite weak bonding of the chloride ligands in these complexes. This propensity has been utilized to prepare the novel square pyramidal, 16e2 Lewis acid [WCp*(Me2bipy)Cl2]1BPh4 2 through halide abstraction from [WCp*(Me2bipy)Cl3] with NaBPh4. The crystal structures of the cationic complex and its 18e2 CO adduct [WCp*(Me2bipy)(CO)Cl2]1BPh4 2 obtained through carbon monoxide addition to the former have been determined.Introduction The chemistry of monocyclopentadienyl (Cp) transition metal halide complexes is in general well developed and has quite recently been reviewed by Poli.1 His group has largely contributed to and in particular extended the chemistry of halfsandwich Cp molybdenum complexes in higher oxidation states, i.e. MoIV–VI.2–8 For the higher tungsten homologue there have been numerous publications from the groups of Schrock and Green mostly dedicated to tungsten in its WIII,V,VI oxidation state.1,9–17 The latter compounds have frequently been obtained from the very versatile and readily available starting materials [W(CpR)Cp*Cl4].1,9–19 On the other hand, little was known about tungsten(IV) halfsandwich complexes when we started to work in this area.20–25 To the best of our knowledge, the single electron reduction of [W(CpR)Cp*Cl4] to yield “[W(CpR)Cp*Cl3]” had so far not been carried out with success; Schrock et al.17 have even provided some limited evidence that “[WCp*Cl3]” might undergo disproportionation to tungsten-(III) and -(V) species.Related redox chemistry of the PMe3 adduct of [WCp*Cl4], [WCp*- Cl4(PMe3)], in the presence of phosphine donors has recently been described by Baker et al.23 It is noteworthy that the corresponding molybdenum(IV) complex “[MoCp*Cl3]” has very recently been prepared by Poli and co-workers 4 by a oneelectron reductive route from [MoCp*Cl4].The crystal structure analysis showed that the molybdenum(IV) compound is actually a doubly m-chloride bridged dimer, i.e. [{MoCp*Cl2(m-Cl)}2], which can be cleaved to monomeric complexes by addition of phosphine ligands.4 In the search for a route to electron rich half-sandwich tungsten( IV) complexes with a series of 4,49-disubstituted 2,29-bipyridyl (R2bipy) donor ligands of the type [WIVCp*(R2bipy)Cl3] the aforementioned route for molybdenum seemed attractive since a common starting material, i.e.“[WCp*Cl3]”, could be used in these syntheses. We have hence turned to the synthesis of this material from [WCp*Cl4] under reductive conditions and have briefly reported on its preparation and dimeric crystal structure in a recent communication.26 In this publication, we will present a general route to [WIVCp*(R2bipy)Cl3] complexes from this hitherto unknown starting material.The crystal structures of the 4,49-dimethylbipyridyl representative and the cationic 16e2 † Monocyclopentadienyl complexes. Part 1. Lewis acid obtained from it through halide abstraction, i.e. [WCp*(Me2bipy)Cl2]1, will be reported. Results and discussion Since the synthesis, isolation, electronic and magnetic properties of [(WCp*Cl3)2] 1 will be described in some detail in a forthcoming publication, we will just briefly review some aspects of its preparation.Compound 1 can be obtained according to eqn. (1) by one-electron reduction through careful controlled addition of NaHg to [WCp*Cl4] in toluene, to avoid formation of [(WCp*Cl2)2]. However, the isolation of pure compound 1 from this reaction mixture is rather cumbersome owing to its extremely high air-sensitivity and limited solubility in innocent solvents, such as toluene, which have to be used to prevent decomposition. We have therefore prepared complexes 2-R from compound 1 generated in situ according to eqn.(2). Preferably, 1/2 equivalent of the mild reducing agent, the electron rich tetrakis(dimethylamino) substituted olefin, (NMe2)2C]] C(NMe2)2 (TDAE), is used in this reaction. Complexes 2-R were prepared by this route in good to excellent yields as microcrystalline materials; depending on the bipyridyl substituent R their colours vary from yellow to dark violet (see Experimental section). Although the quite low solubility of most compounds posed some problems to their1968 J.Chem. Soc., Dalton Trans., 1999, 1967–1974 isolation pure, we have obtained correct elemental analysis data for all novel complexes 2-R shown in eqn. (2). The related Cp molybdenum complex to 2-R, [MoCp- (bipy)Br3], had been reported by Haines et al.27 some years ago and has been prepared through thermal decarbonylation of the dicarbonyl starting material, [MoCp(CO)2Br3], in the presence of the N-donor. Owing to the low solubility, however, this compound has been characterized only by elemental analysis. Adaptation of this synthesis for the tungsten analogues required [WCp*(CO)2Cl3], which just recently has become available.24 The compound 2-Me could be prepared according to this route in reasonable yield, eqn.(2). It should be noted that the reductive pathway shown in eqn. (2) is clearly superior to the latter preparation, since isolation from carbonyl containing by-products is not required, higher overall yields are obtained and the more readily available starting material [WCp*Cl4] can be utilized.Analytically pure compounds 2-R are weakly paramagnetic with magnetic moments, meff, of 0.5–0.8 mB at RT. This explains the broad lines observed in the 1H NMR spectra and leads in most cases to unresolved H–H coupling due to line broadening of the bipyridyl resonances. It is interesting, however, that the chemical shifts of the bipyridyl and the Cp* methyl 1H NMR resonances are still in the expected range for the presumed diamagnetic complexes.The measurement of 13C NMR spectra was limited to the tert-butyl substituted complex 2-tBu owing to the very low solubilities of the other complexes 2-R. However, even at 1021 M concentration of 2-tBu in CD2Cl2 at 75.1 MHz and using polarization transfer techniques, we could merely detect the rather broad resonance of the peripheral tert-butyl methyl groups. Hence, although the NMR data allowed only limited structural assignments, the 1H NMR spectra provided evidence for Cs symmetry in complexes 2-R.The chemical equivalence of the equivalent positions in the bipyridyl rings suggested that of two possible isomers (mer and fac) for 2-R shown, only the facial isomer a was present in solution. This was also in accordance with steric arguments, since an energetically less favourable structure for the meridional isomer b was anticipated due to steric repulsion between the Cp* and one of the bipyridyl rings. It deserves special mention, however, that in the cyclopentadienyl molybdenum series, i.e.for complexes of the type [MoCpL2X3] where L is a mono- or bi-dentate phosphine donor and X = halide, both types of isomers a, b have been observed.5,8,28,29 In order to establish the structure of complexes 2-R unambiguously, we have therefore performed a crystal structure analysis of the methyl derivative 2-Me. Crystal structure of complex 2Et-Me Although the collected data for complex 2-Me allowed us to establish clearly the geometric arrangement around the tungsten centre as the facial isomer a, disorder in the Cp* rings led to severe problems with the data refinement.We have therefore prepared and collected a crystal data set for the ethyltetramethyl analogue [W(C5Me4Et)(Me2bipy)Cl3] 2Et-Me. This small variation allowed us to obtain better data and to solve and refine the molecular structure of 2Et-Me which is presented in Fig. 1.Selected bond distances and angles are given in Table 1. Although the W central atom in complex 2Et-Me is formally eight-co-ordinate, the structure is described better in terms of a pseudo-octahedral geometry with the ethyltetramethylcyclopentadienyl (C5Me4Et) ligand occupying one co-ordination site. The equatorial plane then includes the nitrogen atoms of the 4,49-dimethylbipyridyl (N1, N2) and the Cl ligands, Cl1 and Cl2. This is best illustrated through the Cl3–W1–Z1 angle of 174.88 (Z1 = ring centroid).Notably, we observed significant variations in the W–CCp bond lengths (Table 1) which are in the range of 2.244(9) to 2.453(8) Å. Distortions of this type have been observed by Poli and co-workers 6 in the crystal structures of Cp molybdenum complexes and have been interpreted in electronic terms, i.e. W–Cp d bonding.31 Since additional bending of the Cp-ring substituents out of the cyclopentadienyl ring plane away from the metal centre is observed, we anticipate that steric congestion at the metal centre is also contributing.However, by comparison with tungsten–chlorine bonds in other 18 e2 tungsten complexes,32 the most prominent feature of thisJ. Chem. Soc., Dalton Trans., 1999, 1967–1974 1969 trichloro complex is the rather long W–Cl bond distances [W1– Cl1 2.487(2), W1–Cl2 2.470(2) Å] with the Cl ligand Cl3 in “trans” position to the C5Me4Et group having an even 5 pm longer W–Cl bond [W1–Cl3 2.534(7) Å].Considering the pronounced elongation of the W–Cl bonds, we anticipated that facile ionization of the unique Cl3 ligand might occur in solution and have hence turned to conductivity measurements which are described in the next paragraph. Conductivity measurements Ionization of one of the Cl ligands would lead to the equilibrium (3). The results of a concentration dependent molar [WCp*(R2bipy)Cl3] [WCp*(R2bipy)Cl2]1 1 Cl2 (3) conductivity study for 2-Me in CH2Cl2 solution presented in Fig. 2 clearly established that 2-Me is only partially dissociated at 1023 M concentration (Lm = 1.4 S cm2 mol21, c = 1023 M) and therefore is not a 1 : 1 electrolyte. However, in full agreement with the equilibrium (3), complex 2-Me behaves as an ionophore 33 and is completely dissociated at low concentrations (c < 1025 M, Lm = 32 S cm2 mol21 at 5 × 1026 M). The outcome of these measurements suggested that the cationic complexes [WCp*(R2bipy)Cl2]1 had indeed some inherent stability.Owing to the latter considerations and, also, since these cations were deemed synthetically valuable Lewis acids, we made eVorts to establish the synthetic access to this type of compounds. Fig. 1 An ORTEP30 plot of complex 2Et-Me (ellipsoids are at the 50% probability level). Table 1 Selected bond distances (Å) and angles (8) with estimated standard deviations (e.s.d.s) for complex 2Et-Me W1–Cl1 W1–Cl3 W1–N2 W1–C2 W1–C4 W1–Z1a Cl1–W1–Cl2 Cl2–W1–Cl3 Cl1–W1–N2 Cl3–W1–N1 Cl3–W1–N1 N1–W1–N2 Cl2–W1–Z1 N1–W1–Z1 2.487(2) 2.534(7) 2.164(7) 2.453(8) 2.244(9) 2.20 85.7(1) 77.7(1) 92.8(2) 74.4(2) 74.4(2) 75.8(3) 106.5 102.3 W1–Cl2 W1–N1 W1–C1 W1–C3 W1–C5 C–C (Cp*)av Cl1–W1–Cl3 Cl1–W1–N1 Cl2–W1–N1 Cl3–W1–N2 Cl3–W1–N2 Cl1–W1–Z1 Cl3–W1–Z1 N2–W1–Z1 2.470(2) 2.163(7) 2.436(8) 2.345(9) 2.307(8) 1.423(12) 76.7(1) 151.0(2) 91.1(2) 72.5(2) 72.5(2) 106.3 174.8 103.0 a Z1 is the midpoint of carbon atoms C1 to C5.Synthesis of the cationic complexes 3-R We had anticipated that the cationic complexes 3-R might be directly obtained from compounds 2-R by addition of NaX salts, where X = BPh4 2, PF6 2 or SbF6 2, forcing the equilibrium (3) to the right through formation of insoluble sodium chloride, eqn.(4). Upon addition of NaBPh4 to a violet solution of 2-Me in dichloromethane according to eqn. (4) indeed an immediate change to dark green was noticed. From the reaction mixture, the cationic complex 3-Me could be isolated as an analytically pure microcrystalline green solid in excellent yields.Conductivity measurements in dichloromethane at 1023 and 1024 M gave molar conductivity values of 32 and 58 S cm2 mol21. This clearly evidenced that 3-Me was a 1 : 1 electrolyte consistent with the description as a formal 16-electron complex. The NMR characterization was diYcult due to the observed paramagnetism (meff = 2.18 mB at RT), which gives rise to broad and strongly shifted, temperature dependent 1H NMR resonances.Since the NMR spectroscopy allowed little structural assignment, we have performed a single crystal X-ray diVraction study to establish the molecular structure of 3-Me. Crystal structure of complex 3-Me Attempts to grow suitable single crystals of the cationic complexes were rather cumbersome and only successful for the Fig. 2 Concentration dependent molar conductivity of complex 2-Me in dichloromethane.1970 J. Chem. Soc., Dalton Trans., 1999, 1967–1974 BPh4 2 salt, [WCp*(Me2bipy)Cl2]1BPh4 2 3-Me.The crystal structure of this complex is presented in Fig. 3; selected distances and angles are given in Table 2. The shortest contact between the BPh4 2 counter ion and the W atom is 4.7 Å which suggests that there is just coulombic interaction between the cationic metal complex and the anion. A formal 16-electron configuration can therefore be ascribed to 3-Me. The complex adopts a square pyramidal structure, i.e. a four-legged piano stool structure, which is corroborated through the angles at the tungsten centre between the Cp* centroid, Z1, and the bipyridyl and chloride ligands (Cl1–W1–Z1 110.7; Cl2–W1–Z1 113.7; N1–W1–Z1 113.4; N2–W1–Z1 113.38).The bipyridyl donor and the chloride ligands form the basal ligands; the tungsten centre is located 0.087 Å above the basal plane. As expected, the tungsten–chloride bonds W1–Cl1 2.355(1) and W1–Cl2 2.366(1) Å in the cationic complex are significantly shorter than in the corresponding trichloro complex 2-Me suggesting p donation of the chloride ligands to the Lewis acidic tungsten centre.In addition, stronger donation from the Cp* ring to the metal centre is implied through the shorter Cp*centroid–W distance (3-Me: W1–Z1 2.02 vs. 2.20 Å in 2-Me). Overall, the structural parameters of complex 3-Me strongly resemble those reported by Poli 34 for the aforementioned cationic molybdenum [MoCp(PMe3)2Cl2]1 complex, which also displays a square pyramidal structure.Reactivity of complex 3-Me The exceedingly high water sensitivity of the cationic complex 3-Me imposed diYcult problems to the study of its reaction Fig. 3 Molecular structure of the cationic complex 3-Me; the BPh4 2 counter ion has been omitted for clarity (ellipsoids are at the 50% probability level). Table 2 Selected bond distances (Å) and angles (8) with e.s.d.s for complex 3-Me W1–Cl1 W1–N1 W1–C1 W1–C3 W1–C5 C–C (Cp*)av Cl1–W1–Cl2 Cl1–W1–N2 Cl2–W1–N2 Cl1–W1–Z1 N1–W1–Z1 2.355(1) 2.134(3) 2.305(4) 2.334(4) 2.372(3) 1.408(5) 83.1(4) 85.0(1) 132.8(1) 110.7 113.4 W1–Cl2 W1–N2 W1–C2 W1–C4 W1–Z1a Cl1–W1–N1 Cl2–W1–N1 N1–W1–N2 Cl2–W1–Z1 N2–W1–Z1 2.366(1) 2.143(2) 2.302(3) 2.405(4) 2.02 135.7(1) 83.9(8) 73.6(1) 113.7 113.3 a Z1 is the midpoint of carbon atoms C1 to C5.chemistry. Even under very careful conditions, i.e. using high vacuum and dry-box techniques and thoroughly dried solvents, the formation of the violet, diamagnetic, dinuclear m-oxo, bis-m- Cl bridged complex, [{WCp*(Me2bipy)}2(m-O)(m-Cl)2]21 4,35 was noticed in the presence of even trace amounts of water.So far, we were therefore restricted to reactions which proved to be suYciently fast to intercept the irreversible formation of the undesired hydrolysed product 4. The CO addition to complex 3-Me, which quite surprisingly is only moderately fast and complete within 45 min at RT, fulfils this requirement and gives the cationic carbonyl complex 5-Me in excellent yield, eqn.(5). In contrast to the other mononuclear tungsten(IV) complexes described herein, the carbonyl complex 5-Me is diamagnetic, as evidenced through sharp well resolved 1H and 13C NMR spectra. This quite likely reflects the larger ligand field splitting due to the carbonyl ligand. The inequivalence of the 1H and 13C NMR resonances of the equivalent positions in the bipyridyl rings immediately allowed us to establish that 5-Me no longer possessed Cs symmetry.This clearly evidenced that the CO ligand was not incorporated into the vacant co-ordination site of the square-pyramidal complex, i.e. trans to the Cp* ring, but rather was co-ordinated in the equatorial plane of the pseudooctahedral complex. The IR spectrum displays a single stretching frequency at n(CO) 2004 cm21 in the carbonyl range, which suggests sizeable back donation from the metal centre to the CO ligand and also rules out the presence of another isomer in solution.The spectroscopic assignment was confirmed later by the results of a crystal structure analysis (Fig. 4); selected bond lengths and angles in Table 3. Crystal structure investigation of complex 5-Me Despite some minor crystallographic problems due to positional disorder of the equatorial CO and Cl ligands (see Experimental section for details), the equatorial position of the CO ligand in the carbonyl complex could be unambiguously demonstrated through the results of the crystal structure analysis.The co-ordination geometry around the tungsten centre in complex 5-Me is best described as a pseudo-octahedron with the bipyridyl, the CO and Cl(1) ligands in the equatorial plane and the Cp* ring and Cl(2) in the axial positions. The averaged W–Cl(1,2) distances of 2.42 Å are intermediate between those found in the trichloro complex 2-Me and the correspondingJ. Chem. Soc., Dalton Trans., 1999, 1967–1974 1971 cationic complex 3-Me, which implies that the CO ligand can remove electron density from the rather electron rich d2 system.In order to establish whether co-ordination of CO occurs initially at the axial position, which is then followed by isomerization (path a), or alternatively, through isomerization prior to CO addition (path b), we have monitored the reaction of 3-Me with CO by variable temperature 1H NMR spectroscopy. Within detection limits, we could only observe the resonances of the starting material 3-Me and the product 5-Me in these experiments, which suggests that the reaction proceeds via path b.It should be noted, however, that the absence of NMR signals arising from a (undetected) Cs symmetrical intermediate with the CO ligand in trans position to the Cp* ring does not completely rule out path a since the latter transient might just be present at very low concentration. Nevertheless, it is deemed that co-ordination of the CO ligand in the equatorial plane of complex 5-Me is thermodynamically preferred on both (1) steric and (2) more relevant electronic grounds.Item (1) can be rationalized based on the steric encumbrance in the related trichloro complex 2-Me, which has been used in the latter context to explain the out-of-plane bending of the Cp* methyl groups (see above). The smaller (slimmer) CO ligand thus can orient in a way that just one of the sterically more demanding Cl ligands is oriented in cis position to the Cp* ring. For item (2) it has to be considered that in an unperturbed octahedral d2 system (Oh symmetry) the two electrons reside in the basal plane, the dxy orbital. On these grounds p-back donation to the CO ligand can only be established if the CO group is co-ordinated in the basal plane.Fig. 4 Molecular structure of the carbonyl complex 5-Me; only one of the disordered positions of atoms Cl1,2 and the carbonyl ligand are presented. The BPh4 2 counter ion has been omitted for clarity (ellipsoids are at the 50% probability level).Table 3 Selected bond distances (Å) and angles (8) with e.s.d.s for complex 5-Me W1–Cl1a,ba W1–N1 W1–C1 W1–C3 W1–C6 C23a,b–O1a,b C–C (Cp*)av Cl1a,b–W1–Cl2a,b C23a,b–W1–Cl1a,b W1–C23a,b–O1a,b Cl1a,b–W1–Z1 N1–W1–Z1 2.41 2.187(3) 2.394(6) 2.295(6) 2.432(6) 1.14 1.413(8) 78.4 87.5 170.8 105.7 105.1 W1–Cl2a,b W1–N2 W1–C2 W1–C4 W1–C23a,b W1–Z1b N1–W1–N2 Cl2a,b–W1–C23a,b Cl2a,b–W1–Z1 N2–W1–Z1 2.45 2.176(3) 2.320(5) 2.350(5) 2.00 2.03 74.4(1) 75.9 171.4 106.0 a Averaged values for disordered positions given.b Z1 is the midpoint of carbon atoms C1 to C5. Conclusion We have demonstrated that bipyridyl substituted half-sandwich tungsten(IV) 2-Me complexes are readily obtained through one electron reduction of the versatile starting material [WCp*Cl4] in the presence of the bipyridyl donors. Facile ionization of one chloride ligand in these electron rich complexes allowed us to isolate the corresponding cationic tungsten(IV) complex 3-Me.Most of the d2 tungsten(IV) complexes described herein are paramagnetic; the investigation of the paramagnetic origin by both experimental and theoretical methods will be reported in due course. Experimental Reactions were carried out under a dinitrogen atmosphere with thoroughly dried solvents using glove-box and Schlenk techniques. The compounds [WCp*Cl4],12 [W(C5Me4Et)Cl4],12 [WCp*(CO)2Cl3] 24 and tBu2bipy 36 were prepared according to published methods.The rather cumbersome synthesis of (NMe2)2bipy has been described previously.37 We have prepared this ligand by a straightforward albeit low-yield (15%) route through reductive coupling of the commercially available pdimethylaminopyridine with Raney nickel. The 1H NMR and 13C NMR spectra were recorded on Varian Gemini 200 and 300 spectrometers. Chemical shifts are given in ppm and referenced to the residual 1H or 13C NMR solvent shifts.The assignment of resonances is based on DEPT and selective 1H NMR homo decoupling experiments. The IR spectra were measured on a Bio-Rad FTS-45 Fourier IR spectrometer. The CHN analyses were carried out with a LECO CHNS-932 elemental analyser in our institute. Some of the compounds contained solvents from recrystallization in the analytically pure material; this has been confirmed independently by integration of the solvent in the 1H NMR spectrum. Conductivity measurements were performed with an Amel-160 conductometer using a glass cell with platinum electrodes (K = 1.0).Magnetic moments have been determined at room temperature with a Johnson-Matthey laboratory magnetic susceptibility balance and were corrected for diamagnetic contributions. Syntheses [WCp*(Me2bipy)Cl3] 2-Me. From [WCp*Cl4]. At room temperature, a solution of 183 mg (0.91 mmol) (NMe2)2C]] C(NMe2) (TDAE) in 10 ml dichloromethane was added to an orange suspension of 842 mg (1.83 mmol) [WCp*Cl4] and 336 mg (1.83 mmol) Me2bipy in 100 ml dichloromethane upon which a change to dark violet was observed.The suspension was stirred for 1 h at this temperature, then filtered through a pad of Celite and the Celite washed with a small amount of CH2Cl2. After concentration of the filtrate to ca. 40 ml the product was precipitated through addition of 40 ml of diethyl ether. The solid was collected by filtration, washed twice with ether and pentane and finally dried in high vacuo to give complex 2-Me as an analytically pure violet microcrystalline solid.Yield: 1.01 g, 1.66 mmol, 91% (based on [WCp*Cl4]. 1H NMR (CD2Cl2, RT, 300 MHz): d 8.7 (br, w1/2 ª 32, 2 H, Me2bipy), 8.1 (br, w1/2 ª 13, 2 H, Me2bipy), 7.5 (br, w1/2 ª 13, 2 H, Me2bipy), 2.8 (br, w1/2 ª 24, 6 H, Me2bipy) and 1.7 (br, w1/2 ª 6 Hz, 15 H, C5Me5). MS (EI): m/z 608 (M1 22H) and 575 (M1 2Cl) (Calc. for C22H27Cl3N2W: C, 43.34; H, 4.46; N, 4.59. Found: C, 43.13; H, 4.30; N, 4.50%).From [WCp*(CO)2Cl3]. A suspension of 80 mg (0.170 mmol) [WCp*(CO)2Cl3] and 31 mg (0.170 mmol) Me2bipy in 20 ml toluene was heated in vacuum for 6 h to 110 8C leading to a change from yellow to dark brown. After this time the reaction mixture was allowed to cool to RT, the solid collected by centrifugation and washed with small portions of ether until the washing solutions remained colourless. The residue was then dried in high vacuo and recrystallized at –36 8C from a pentane1972 J.Chem. Soc., Dalton Trans., 1999, 1967–1974 layered solution of the crude product in CH2Cl2. Yield: 66 mg, 64%. [W(Á5-C5Me4Et)(Me2bipy)Cl3] 2Et-Me. A solution of 58 mg (0.290 mmol) TDAE in 3 ml dichloromethane was slowly dropped on to a solution of 276 mg (0.581 mmol) [W(h5- C5Me4Et)Cl4] and 108 mg (0.587 mmol) Me2bipy in 15 ml CH2Cl2 at RT giving a violet suspension which was stirred for 1 h at RT. Upon filtration through Celite the filtrate was concentrated to ca. 10 ml, then cooled to 236 8C. At this temperature complex 2Et-Me was obtained as violet needles which were isolated by decantation of the mother-liquor. The crystals were washed with a small amount of pentane, then dried in high vacuo to give 309 mg, 0.495 mmol, 85% 2Et-Me {based on [W(h5-C5Me4Et)Cl4]}. Crystals suitable for X-ray diVraction were obtained by slow diVusion of diethyl ether into a solution of 2Et-Me in dichloromethane at room temperature. 1H NMR (CD2Cl2, RT, 300 MHz): d 8.6 (br, w1/2 ª 69, 2 H, Me2bipy), 8.1 (br, w1/2 ª 11, 2 H, Me2bipy), 7.5 (br, w1/2 ª 23, 2 H, Me2bipy), 2.9 (br, w1/2 ª 56 Hz, 6 H, Me2bipy), 1.80 (s, 6 H, C5Me4Et), 1.75 (s, 6 H, C5Me4Et), 1.45 (q, 2 H, C5Me4CH2CH3, J = 7) and 1.03 (t, 3 H, C5Me4CH2CH3, J = 7 Hz) (Calc.for C23H29Cl3N2W: C, 44.29; H, 4.69; N, 4.49. Found: C, 44.18; H, 4.72; N, 4.64%). [WCp*(tBu2bipy)Cl3] 2-tBu. To a suspension of 1.73 g (3.75 mmol) [WCp*Cl4] and 1.01 g (3.77 mmol) tBu2bipy in 150 ml CH2Cl2, a solution of 375 mg (1.88 mmol) TDAE in 15 ml CH2Cl2 was slowly added at RT.After stirring for 1 h the violet suspension was filtered through Celite and the volume of filtrate reduced to ca. 50 ml in vacuo. Upon addition of 100 ml diethyl ether to the filtrate the product precipitated and was collected by filtration and washed with ether and pentane. The solid was finally dried in high vacuo to yield 2.47 g, 3.56 mmol, 95% 2-tBu based on [WCp*Cl4]. 1H NMR (CD2Cl2, RT, 300 MHz): d 8.8 (br, w1/2 ª 35, 2 H, tBu2bipy), 8.2 (br, w1/2 ª 10, 2 H, tBu2bipy), 7.7 (br, w1/2 ª 40, 2 H, tBu2bipy), 1.71 (br, w1/2 ª 15 Hz, 15 H, C5Me5) and 1.45 (s, 18 H, CMe3).MS (EI): m/z 692 (M1) and 657 (M1 2 Cl) (Calc. for C28H39Cl3N2W: C, 48.47; H, 5.67; N, 4.04. Found: C, 48.10; H, 5.49; N, 4.07%). [WCp*{(NMe2)2bipy}Cl3] 2-NMe2. A solution of 76 mg (0.38 mmol) TDAE in 20 ml dichloromethane was added dropwise to a solution of 350 mg (0.76 mmol) [WCp*Cl4] and 185 mg (0.76 mmol) (NMe2)2bipy in 60 ml CH2Cl2 giving a yellow-orange suspension.After stirring for 2 h at RT the reaction mixture was filtered through a pad of Celite and washed with a small amount of CH2Cl2. The collected filtrates were concentrated in vacuo to ca. 10 ml, upon which the product precipitated as a yellow-orange solid; precipitation was completed through addition of 40 ml ether. The solid was collected by filtration, washed with toluene and ether and finally dried in high vacuum.Yield: 450 mg, 0.67 mmol, 89% based on [WCp*Cl4]. 1H NMR (CD2Cl2, 298 K): d 8.37 [d, 4J = 2, 2 H, (NMe2)2bipy], 7.46 [m, 2 H, (NMe2)2bipy], 7.0 [d, 3J = 7 Hz, 2H, (NMe2)2bipy], 4.84 [br, w1/2 = 20, 12 H, (NMe2)2bipy] and 2.61 (br, w1/2 = 6 Hz, 15 H, C5Me5) (Calc. for C24H33Cl3N4W: C, 43.17; H, 4.98; N, 8.39. Found: C, 43.22; H, 5.25; N, 8.01%). [WCp*(Me2bipy)Cl2]1BPh4 2 3-Me. A solution of 1.05 g (3.08 mmol) NaBPh4 in 30 ml THF was added to a stirred suspension of 1.88 g (3.08 mmol) [WCp*(Me2bipy)Cl3] in 100 ml THF at RT.After stirring for 30 min at this temperature a clear brown solution was obtained which was evacuated to dryness. The residue was extracted into 150 ml of 1,2-dichloroethane and filtered through a fine porous frit covered with a pad of Celite. After concentration of the green filtrate to 80 ml in vacuo, 180 ml ether were slowly added. From this mixture, the product crystallized overnight as a microcrystalline dark green solid at RT. The mother-liquor was decanted oV, the solid washed with ether and finally dried in high vacuum to give 2.1 g, 2.35 mmol 3-Me, 76% based on [WCp*(Me2bipy)Cl3]. Single crystals suitable for X-ray diVraction were obtained at RT by crystallization from an ether–1,2-dichloroethane solution. 1H NMR (CD2Cl2, 300 MHz, 293 K): d 106 (br, w1/2 ª 105), 43 (br, w1/2 ª 40), 28 (br, w1/2 ª 30), 17.5 (br, w1/2 ª 40), 7.4 (m, 8 H, BPh4 2), 7.0 (m, 8 H, BPh4 2), 6.9 (m, 4 H, BPh4 2) and 285 (br, w1/2 ª 110 Hz).MS: FAB1 m/z 535 (M1 2 Cl); FAB2 m/z 319 (BPh4 2). Molar conductivity, Lm(CH2Cl2): c = 1024, 58; 1023 M, 32 S cm2 mol21 (Calc. for C46H47BCl2N2W: C, 61.84; H, 5.30; N, 3.14. Found: C, 61.49; H, 5.33; N, 3.10%). [WCp*{(NMe2)2bipy}Cl2][BPh4] 3-NMe2. A solution of 102 mg NaBPh4 (0.30 mmol) in 10 ml THF was added to a suspension of 199 mg (0.30 mmol) [WCp*{(NMe2)2bipy}Cl3] in 10 ml THF. After stirring for 30 min at RT the reaction mixture was evaporated to dryness in high vacuum.The residue was extracted into 15 ml 1,2-dichloroethane, and filtered through a fine frit covered with a pad of Celite. Diethyl ether was added to the filtrate until precipitation of the product was observed. Overnight the product crystallized from this mixture as a dark green microcrystalline solid. The solid was collected by filtration, washed with ether and dried in high vacuum. Yield: 160 mg, 0.17 mmol, 56% based on [WCp*{(NMe2)2bipy}Cl3]. 1H NMR (CD2Cl2, 293 K): d 8.64 [dd, 3J = 7, 4J = 2, 2 H, (NMe2)2bipy], 7.31 (m, 8 H, BPh4 2), 7.01 (m, 8 H, BPh4 2), 6.85 (m, 4 H, BPh4 2), 6.58 [d, 4J = 2 Hz, 2 H, (NMe2)2bipy], 6.30 [br, w1/2 = 30, 6 H, (NMe2)2bipy], 5.85 [br, w1/2 = 30 Hz, 6 H, (NMe2)2bipy], 4.85 [d, 3J = 7 Hz, 2 H, (NMe2)2bipy] and 3.26 (s, w1/2 = 4 Hz, 15 H, C5Me5) (Calc. for C48H53BCl2N4W?CH2Cl2: C, 56.78; H, 5.35; N, 5.41. Found: C, 56.40; H, 5.22; N, 5.39%). [WCp*(Me2bipy)(CO)Cl2]1BPh4 2 5-Me. In the dry-box, 363 mg (0.41 mmol) [WCp*(Me2bipy)Cl2]1BPh4 2 3-Me were dissolved in 30 ml 1,2-dichloroethane in a 200 ml high-vacuum Young tap-sealed Schlenk tube and transferred to a high vacuum manifold. The solution was frozen out at liquid nitrogen temperature, evacuated, then refilled with 1 bar of carbon monoxide and warmed to RT.Within 45 min of stirring at this temperature a change from dark green to red was observed. After stirring for 90 min the solution was concentrated to 10 ml in vacuo and the product precipitated as a microcrystalline orange-red solid by slow addition of diethyl ether.It was collected by filtration, washed twice with ether and pentane, then dried in high vacuo. The CO complex 5-Me is insoluble in THF but dissolves well in CH2Cl2. Yield: 325 mg, 0.35 mmol, 87%. 1H NMR (CD2Cl2, 300 MHz, 293 K): d 9.03 (d, 3J = 6, 1 H, Me2bipy), 8.33 (d, 1 H, 3J = 6, Me2bipy), 7.91 (m, 1 H, Me2bipy), 7.89 (m, 1 H, Me2bipy), 7.56 (dd, 3J = 6, 4J = 2, 1 H, Me2bipy), 7.35 (m, 8 H, BPh4 2), 7.28 (dd, 3J = 6, 4J = 2 Hz, 1 H, Me2bipy), 6.99 (m, 8 H, BPh4 2), 6.83 (m, 4 H, BPh4 2), 2.52 (s, 3 H, Me2bipy), 2.48 (s, 3 H, Me2bipy) and 1.78 (s, 15 H, C5Me5). 13C-{1H} NMR (CD2Cl2, 75.4 MHz, 298 K): d 214.1 (s, CO), 164.3 [q, B(C6H5)4 2, 1JB-C = 50], 156.8 (s, quart. Carom, Me2bipy), 156.1 (s, quart. Carom, Me2bipy), 155.7 (s, CHarom, Me2bipy), 154.9 (s, quart. Carom, Me2bipy), 154.5 (s, quart. Carom, Me2bipy), 149.7 (s, CHarom, Me2bipy), 136.4 [q, CHarom, B(C6H5)4 2, JB-C = 2], 131.3 (s, CHarom, Me2bipy), 129.8 (s, CHarom, Me2bipy), 126.4 (s, CHarom, Me2bipy), 126.2 [q, CHarom, B(C6H5)4 2, JB-C = 3 Hz], 122.3 [q, CHarom, B(C6H5)4 2], 110.2 (s, quart.Carom, C5Me5), 22.2 (s, Me2bipy), 22.0 (s, Me2bipy) and 10.9 (s, C5Me5). IR (CH2Cl2): n(CO) 2004 cm21 (Calc. for C47H47- BCl2N2OW?C2H4Cl2: C, 57.68; H, 5.04; N, 2.75. Found: C, 58.04; H, 4.66; N, 2.70%). Single crystals suitable for X-ray diVraction were obtained by slow diVusion of ether into a solution of 5-Me in 1,2-dichloroethane at RT.Crystal structure analyses General remarks. Suitable single crystals of complexes 2Et-Me, 3-Me and 5-Me were mounted on a glass fibre in Paratone-NJ. Chem. Soc., Dalton Trans., 1999, 1967–1974 1973 Table 4 Crystal and data collection parameters for compounds 2Et-Me, 3-Me and 5-Me 2Et-Me 3-Me 5-Me Formula M Crystal system Space group a/Å b/Å c/Å b/8 V/Å3 Z m/mm21 T/K 2q range/8 No. measured reflections (total, unique) R1 [F2 > 2s(F2)] wR2 [F2 > 2s(F2)] C23H29Cl3N2W?2CH2Cl2 793.5 Monoclinic P21/n (no. 14) 8.324(1) 17.879(3) 20.464(4) 100.92(1) 2990.4(9) 4 4.50 193 4–52 5749, 5339 0.0563 0.1463 C46H47BCl2N2W 893.4 Monoclinic P21/c (no. 14) 11.672(1) 16.362(2) 21.122(2) 99.61(1) 3977.2(7) 4 3.07 193 4–52 36931, 7678 0.0192 0.0372 C47H47BCl2N2OW?C2H4Cl2 1020.4 Monoclinic P21/n (no. 14) 22.428(2) 9.264(1) 23.646(2) 115.13(1) 4448.0(7) 4 2.88 193 4–52 34876, 8462 0.0280 0.0770 (oil), transferred on the goniometer head to the diVractometer and cooled to 280 8C in a nitrogen cryostream.The data sets were collected with graphite monochromated Mo-Ka radiation (l 0.71073 Å) on Siemens P4 four-circle (2Et-Me) and Stoe IPDS image plate diVractometers (3-Me and 5-Me). Intensities were corrected for Lorentz-polarization eVects and absorption corrections performed either empirically from y scans (2Et-Me) or numerically with the faces and corresponding crystal dimensions determined using the STOE Faceit-Video CCD camera microscope system (3-Me and 5-Me).The structures were solved using direct methods with the SHELXS 86 program package.38 The refinements were carried out with SHELXL 93 using all unique Fo 2.39 Except for complex 5-Me all nonhydrogen atoms were refined anisotropically. The positions of the hydrogen atoms were calculated in idealized positions (C–H bonds fixed at 0.96 Å) and refined as a riding model with a fixed isotropic displacement factor of U = 0.08 Å2.The details of the data collection and refinement including R values are summarized in Table 4. Complex 5-Me. One disordered molecule of 1,2-dichloroethane from recrystallization was contained per molecule of complex and was refined with two split positions with occupation factors of 0.55 and 0.45 for the disordered Cl3 atom. The CO ligand and atom Cl1 were positionally disordered; this was indicated in the Fourier-diVerence map through a large peak between the C23–O1 bond vector and by another peak located on the W1–Cl1 axis (distant from W1) in close proximity to Cl1 (0.56 Å apart from Cl1).The disorder was resolved and refined with split positions for atoms C23 and O1 (denoted as C23a,b and O1a,b) and two split positions for Cl1, denoted as Cl1a,b, with their occupational parameters refined as an independent variable. The positions of C23a,b and O1a,b were refined isotropically using identical displacement parameters (EADP card) while Cl1a,b was treated anisotropically.The refinement of the occupational parameter converged at final values of 0.44 and 0.56. In addition, a strong thermal mobility of Cl2 was noticed. This could be refined with two split positions, i.e. Cl2a,b, and using the occupational parameters obtained for the aforementioned positional disorder of the CO and Cl1 ligands. The residual non-hydrogen atoms were refined anisotropically; the positions of the hydrogen atoms were calculated in idealized positions and refined as above.CCDC reference number 186/1438. See http://www.rsc.org/suppdata/dt/1999/1967/ for crystallographic files in .cif format. Acknowledgements We are indebted to Professor Heinz Berke for his generous support. We thank Mr Thomas Hiltebrand for working out the details of the synthesis of (NMe2)2bipy. Funding of this project by the Swiss National Science Foundation is gratefully acknowledged. References 1 R.Poli, Chem. Rev., 1991, 91, 509. 2 J. U. Desai, J. C. Gordon, H.-B. Kraatz, V. T. Lee, B. E. Owens- Waltermire, R. Poli, A. L. Rheingold and C. B. White, Inorg. Chem., 1994, 33, 3752. 3 F. Abugideiri, J. C. Gordon, R. Poli, B. E. Owens-Waltermire and A. L. Rheingold, Organometallics, 1993, 12, 1575. 4 F. Abugideiri, G. A. Brewer, J. U. Desai, J. C. Gordon and R. Poli, Inorg. Chem., 1994, 33, 3745. 5 R. Poli and M. A. J. Kelland, Organomet. Chem., 1991, 419, 127. 6 S. T. Krueger, R. Poli, A. L. Rheingold and D. L. Staley, Inorg. Chem., 1989, 28, 4599. 7 S. T. Krueger, B. E. Owens and R. Poli, Inorg. Chem., 1990, 29, 2001. 8 B. E. Owens and R. Poli, Inorg. Chim. Acta, 1991, 179, 229. 9 R. R. Schrock, A. H. Liu, M. B. O’Regan, W. C. Finch and J. F. Payack, Inorg. Chem., 1988, 27, 3574. 10 R. R. Schrock, T. E. Glassman, M. G. Vale and M. Kol, J. Am. Chem. Soc., 1993, 115, 1760. 11 M. B. O’Regan, A. H. Liu, W. C. Finch, R. R. Schrock and W. M.Davis, J. Am. Chem. Soc., 1990, 112, 4331. 12 R. C. Murray, L. Blum, A. H. Liu and R. R. Schrock, Organometallics, 1985, 4, 953. 13 X. Morise, M. L. H. Green, P. C. McGowan and S. J. Simpson, J. Chem. Soc., Dalton Trans., 1994, 871. 14 A. H. Liu, R. C. Murray, J. C. Dewan, B. D. Santarsiero and R. R. Schrock, J. Am. Chem. Soc., 1987, 109, 4282. 15 M. L. H. Green, J. D. Hubert and P. Mountford, J. Chem. Soc., Dalton Trans., 1990, 3793. 16 M. L. H. Green, A. Izquierdo, J. J. Martin-Polo, V. S. B. Mtetwa and K. Prout, J. Chem. Soc., Chem. Commun., 1983, 538. 17 R. R. Schrock, S. F. Pedersen, M. R. Churchill and J. W. Ziller, Organometallics, 1984, 3, 1574. 18 M. L. H. Green and P. Mountford, Chem. Soc. Rev., 1992, 29. 19 T. E. Glassman, M. G. Vale and R. R. Schrock, Inorg. Chem., 1992, 31, 1985. 20 S. J. Holmes and R. R. Schrock, Organometallics, 1983, 2, 1463. 21 Q. Feng, M. Ferrer, M. L. H. Green, P. Mountford and V. S. B. Mtetwa, J. Chem. Soc., Dalton Trans., 1992, 1205. 22 Q. Feng, M. Ferrer, M. L. H. Green, P. Mountford, V. S. B. Mtetwa and K. Prout, J. Chem. Soc., Dalton Trans., 1991, 1397. 23 R. T. Baker, J. C. Calabrese, R. L. Harlow and I. D. Williams, Organometallics, 1993, 12, 830. 24 H. Blackburn, H.-B. Kraatz, R. Poli and R. C. Torralba, Polyhedron, 1995, 14, 2225. 25 E. R. Burckhardt, J. J. Doney, R. G. Bergman and C. H. Heathcock, J. Am. Chem. Soc., 1987, 109, 2022. 26 C. Cremer, H. Jacobsen and P. Burger, Chimia, 1997, 51, 650. 27 R. J. Haines, R. S. Nyholm and M. H. B. Stiddard, J. Chem. Soc. A, 1966, 1606. 28 G. S. B. Adams and M. L. H. Green, J. Chem. Soc., Dalton Trans., 1981, 353.1974 J. Chem. Soc., Dalton Trans., 1999, 1967–1974 29 K. Stärker and M. D. Curtis, Inorg. Chem., 1985, 24, 3006. 30 C. K. Johnson, ORTEP, Report ORNL-5138, Oak Ridge National Laboratory, Oak Ridge, TN, 1976. 31 P. Kubácek, R. HoVmann and Z. Havlas, Organometallics, 1982, 1, 180. 32 A. G. Orpen, L. Brammer, F. H. Allen, O. Kennard, D. G. Watson and R. Taylor, J. Chem. Soc., Dalton Trans., 1989, S1. 33 W. J. Geary, Coord. Chem. Rev., 1971, 7, 81. 34 R. Poli, Chem. Rev., 1996, 96, 2135. 35 C. Cremer and P. Burger, unpublished work. 36 G. M. Badger and W. H. F. Sasse, J. Chem. Soc., 1956, 616. 37 P. Wehman, G. C. Dol, E. R. Moorman, P. C. J. Kramer and P. W. N. M. van Leeuwen, Organometallics, 1994, 13, 4856. 38 G. M. Sheldrick, SHELXTL PLUS, University of Göttingen, 1988. 39 G. M. Sheldrick, SHELXL 93, University of Göttingen, 1993. Paper 9/02743B

ISSN:1477-9226    

DOI:10.1039/a902743b

出版商:RSC    

年代:1999

数据来源: RSC