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DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, Pages 2827–2831 2827 Mononuclear nickel complexes assembled into two-dimensional networks via hydrogen bonds and �–� stacking interactions Bao-Hui Ye,* Xiao-Ming Chen, Gen-Qiang Xue and Liang-Nian Ji Department of Chemistry, Zhongshan University, Guangzhou, 510275, P. R. China Three monomeric nickel complexes [Ni(bipy)(O2CMe)2(H2O)2] 1 (bipy = 2,29-bipyridine), [Ni(dmbipy)- (O2CMe)2(H2O)2] 2 (dmbipy = 4,49-dimethyl-2,29-bipyridine) and [Ni(phen)(O2CMe)2(H2O)2]?0.5H2O 3 (phen = 1,10-phenanthroline) have been synthesized and characterized by single-crystal X-ray diVraction methods.In complexes 1 and 2 the molecules are self-assembled via double intermolecular hydrogen bonds to form one-dimensional infinite zigzag chains, which are stacked next to each other through the diimine aromatic rings in a zipper-like fashion, giving a novel two-dimensional co-operating structure. In 3 the molecule is linked by a hydrogen bond to form a one-dimensional chain, which is further associated with another adjacent chain via double hydrogen bonds forming a double chain.These double chains are intercalated to each other through the p–p interaction giving a novel two-dimensional structure. Design and self-assembly of metal compounds into one-, twoand three-dimensional supramolecular architecture is currently attracting considerable attention for potential applications.1,2 Three main lines of studies are adopted, based on the diVerent nature of the interactions responsible for networking, which concern: (i) frames comprised of metal centers and bi- or polydentate ligands connected through co-ordination bonds; (ii) networks derived by the organization of mono- or poly-nuclear metal complexes via hydrogen bonds;3–9 and (iii) structures assembled by p–p interaction of aromatic rings.10 Among these notable systems, the former is connected through chemical bonds, while the last two are self-assembled by weak interactions which play vital roles in highly eYcient and specific biological reactions and are essential for molecular recognition and self-organization of molecules in supramolecular chemistry.In particular, hydrogen-bond assembled molecular materials are of considerable interest, and the incorporation of a transition metal ion into hydrogen-bond systems is important in the crystal engineering of non-linear optical, conducting and ferromagnetic materials.2c,4 Obviously, networks of metal compounds can, in principle, be extended into two or three dimensions via weak interactions such as hydrogen bonds and p–p stacking interactions, though these species have attracted less attention and have rarely been reported.6–10 Here, we report the mononuclear nickel complexes [Ni(bipy)(O2CMe)2(H2O)2] 1 (bipy = 2,29-bipyridine), [Ni(dmbipy)(O2CMe)2(H2O)2] 2 (dmbipy = 4,49-dimethyl-2,29- bipyridine), [Ni(phen)(O2CMe)2(H2O)2]?0.5H2O 3 (phen = 1,10- phenanthroline), in which the hydrophilic groups are selfassembled via hydrogen bonds while the hydrophobic groups are stacked via p–p interaction giving two-dimensional structures.The use of diVerent polypyridyl ligands demonstrates the influence of the p system stacking on self-assembly. Experimental Starting materials were from commercial sources and used without further purification. Elemental analyses (C, H and N) were performed on a Perkin-Elmer 240Q Elemental analyzer.The FT-IR spectra were recorded on a Bruker IFS-66 spectrometer as KBr pellets (4000–400 cm21), UV/VIS spectra on a Shimadzu MPS-2000 spectrophotometer in methanol solution at room temperature. Syntheses [Ni(bipy)(O2CMe)2(H2O)2] 1. 2,29-Bipyridine (0.156 g, 1.0 mmol) in methanol (5 cm3) was added to a methanol solution (10 cm3) containing Ni(O2CMe)2?4H2O (0.249 g, 1.0 mmol). The blue solution was stirred at room temperature for 3 h and filtered.A blue product was obtained by diVusion of diethyl ether into the filtrate, collected by filtration, washed by acetone and diethyl ether, and dried overnight in vacuo. Yield: 72% (Found: C, 45.68; H, 4.73; N, 7.63. Calc. for C14H18N2NiO6: C, 45.53; H, 4.88; N, 7.59%). IR data (KBr, cm21): 3284vs (br), 1556vs, 1441m, 1418vs, 1334m, 1307m, 1165m, 1155m, 1051m, 1027m, 1017m, 873w, 774s, 739m, 662s and 418vw. A single crystal suitable for X-ray diVraction was obtained by diVusing diethyl ether into the methanol solution of complex 1.[Ni(dmbipy)(O2CMe)2(H2O)2] 2. The complex was synthesized by a similar procedure using dmbipy instead of bipy. Yield: 80% (Found: C, 48.50; H, 5.61; N, 7.12. Calc. for C16H22N2NiO6: C, 48.35; H, 5.54; N, 7.05%). IR data (KBr, cm21): 3270vs (br), 1559vs, 1440m, 1420vs, 1337m, 1302m, 1162m, 1153m, 1054m, 1024m, 1013m, 871w, 776s, 738m, 661s and 417vw. A single crystal suitable for X-ray diVraction was obtained by diVusing diethyl ether into the methanol solution of complex 2.[Ni(phen)(O2CMe)2(H2O)2]?0.5H2O 3. The complex was synthesized by a similar procedure using phen in place of bipy. Yield: 73% (Found: C, 48.02; H, 4.86; N, 6.73. Calc. for C16H19N2NiO6.5: C, 47.76; H, 4.72; N, 6.69%). IR data (KBr cm21): 3240vs (br), 1552vs, 1515s, 1428m, 1416vs, 1396s, 1336m, 1024m, 900m, 856s, 730s, 662s, 644m and 426vw. A single crystal suitable for X-ray diVraction was obtained by diVusing diethyl ether into the methanol solution of complex 3.X-Ray crystallography The single crystals of complexes 1, 2 and 3 were mounted on a glass fiber and placed on a Siemens P3/V diVractometer (graphite-monochromated Mo-Ka radiation, l = 0.710 73 Å). The crystal class, orientation matrix, and unit-cell dimensions were determined according to established procedures; parameters were calculated from least-squares fitting of 2q angles for 25 reflections. Three standard reflections were monitored after every 100 data measurements, showing only small random variations. The raw data were processed with a learn-profile procedure, and semiempirical absorption corrections were applied.The crystal structures were solved by direct methods using the SHELXS 97 program package,11 and refined with full-matrix least squares on F2 using SHELXL 97.12 In complex 3 the lattice water molecule exhibits two-fold orientational disorder.2828 J. Chem. Soc., Dalton Trans., 1998, Pages 2827–2831 Table 1 Crystal data and details of the structural determinations for complexes 1–3 at 293(2) K Empirical formula M Crystal system Space group a/Å b/Å c/Å a/8 b/8 g/8 U/Å3, Z Dc/Mg m23 m/mm21 q Range for data collection/8 Reflections collected Independent reflections Observed reflections [I > 2s(I)] R, R9 [I > 2s(I)]* (all data) * Goodness of fit on F2 1 C14H18N2NiO6 369.01 Monoclinic C2/c 15.383(3) 12.758(3) 8.143(2) 92.93(3) 1596.0(6), 4 1.536 1.247 2.07–25.04 1458 1409 1193 0.0343, 0.0801 0.0459, 0.0856 1.065 2 C16H22N2NiO6 397.07 Orthorhombic Pbcn 16.517(6) 13.346(6) 8.148(3) 90.0 1796.1(1), 4 1.468 1.114 1.96–25.03 1589 1589 1009 0.0495, 0.1054 0.0919, 0.1229 1.039 3 C16H19N2NiO6.5 402.04 Triclinic P1� 7.5390(10) 10.303(4) 11.798(4) 106.22(2) 96.10(2) 102.25(1) 846.4(5), 2 1.578 1.185 2.33–26.00 3346 3334 2885 0.0333, 0.0836 0.0420, 0.0882 1.008 * R9 = [Sw(Fo 2 2 Fc 2)2/Sw(Fo 2)2]� �� .All the non-hydrogen atoms were refined anisotropically.Hydrogen atoms of the ligands were generated geometrically (C]H 0.96 Å), assigned isotropic thermal parameters. Crystal data as well as details of data collection and refinement for the complexes are summarized in Table 1. Selected bond distances and angles are listed in Table 2. CCDC reference number 186/1050. Results and Discussion Syntheses and characterization of complexes Aromatic diimine compounds such as bipy and phen may be used as ligands to generate models of metalloenzyme active sites 13 and the sites of molecular recognition.14 They have strong stacking interactions with the side chain aromatic ring of amino acids, and were used to observe the stacking interaction in solution and the solid state.14 Recently, we have noticed some interesting phenomena during the systematic observation of the reactions between bipy ametal acetates.First, the diVerent metal ions can influence the structure assembly, for example treatment of metal acetates with bipy in methanol solution produces linear trinuclear complexes [M3(bipy)2(O2- CMe)6] (M = Mn, Fe or Co),15 a dinuclear complex [Cd2(bipy)2- (O2CMe)4(H2O)2] 16 or a monomeric complex [Ni(bipy)(O2- CMe)2(H2O)2] under similar reaction conditions.Secondly, the presence of a high ionic strength anion such as ClO4 2 resulted in mono- or di-nuclear complexes. For example, treatment of the reaction solution of 1 with 1.5 equivalents NaClO4 led to the formation of [Ni(bipy)2(O2CMe)][ClO4]?H2O.16 Interestingly, a similar procedure applied to the analogous solution containing Cu21 or Zn21 ion gave a dinuclear complex [M2(bipy)2(m-O2CMe)3][ClO4] (M = Cu or Zn).17 This indicated that an equilibrium was existent in solution; when the solvent of the reaction solution was allowed to evaporate slowly or when a hydrophobic solvent, diethyl ether, was added a neutral mono-, di- or tri-nuclear complex was obtained. If NaClO4 was added to the solution the reaction was driven to the formation of a thermodynamically preferred product.The IR spectra of complexes 1, 2 and 3 display an intense and broad band centered at 3284, 3270 and 3240 cm21, respectively. These bands can be assigned to n(O]H) of the aqua ligand, and the broadness is indicative of hydrogen bonds, in accord with the crystal structures. The symmetric and asymmetric stretching vibrations of acetate ligands display characteristic absorption bands at 1556, 1559 and 1552 and 1418, 1420 and 1416 cm21 for complexes 1, 2 and 3, respectively.The D values [nasym(CO2) 2 nsym(CO2)] are 138, 139 and 136 cm21 for complexes 1, 2 and 3, respectively, which are markedly less than those of the unidentate complexes (D @ 160 cm21), but are similar to those of the bidentate bridging complexes (D < 160 cm21).18 This observation suggests that the geometry of the acetate group is similar to that of bidentate bridging, and can be rationalized by the eVect of hydrogen bonds.There exists a strong ‘pulling eVect’ on the non-co-ordinated oxygen of the acetate group, from two hydrogen bonds, one intra- and one inter-molecular. This makes the otherwise very ‘asymmetric’ terminal unidentate acetate group much more ‘symmetric’ than in the normal non-hydrogen-bonded case, and may be regarded as a ‘pseudo-bridging’ arrangement.18 Crystal structures Crystal structures of complexes 1, 2 and 3 reveal that each nickel(II) ion is ligated by a diimine ligand and two terminal unidentate acetates, and further co-ordinated by two aqua ligands forming a slightly distorted NiN2O4 octahedron as shown in Figs. 1 and 2 with the atom numbering scheme. In complexes 1 and 2 the molecule has a crystallographically imposed two-fold axis passing through the nickel ion, and the two oxygen atoms from a pair of acetate ligands occupy the two axial positions with O(1)]Ni(1)]O(1a) 179.3(1)8 for complex 1 and 178.7(2)8 for 2.In contrast, the two aqua ligands occupy the axial positions with O(1w)]Ni(1)]O(2w) 178.45(7)8 for complex 3; this may be attributed to the stronger stacking interaction of phen than bipy ligands (see below). The bond angles around the Ni21 ion at the equatorial plane defined by N(1), N(1a), O(1w) and O(1wa) in complexes 1 and 2, and N(1), N(2), O(1) and O(3) in 3, sum to 3608 within experimental error, showing that they are coplanar. The Ni]N bond distances are 2.069(2), 2.067(4) and 2.070(2) Å, those of Ni]O (aqua) are 2.082(2), 2.077(3) and 2.072(2) Å, and those of Ni]O (acetate) are 2.079(2), 2.077(3) and 2.054(2) Å for complexes 1, 2 and 3, respectively, which are comparable with those of other nickel(II) complexes.20 Each aqua ligand is further stabilized by forming a strong intramolecular hydrogen bond with the unco-ordinated acetate oxygen atom at 2.620(3) Å, D]H? ? ? A 153.28 (A = hydrogen-bond acceptor, D = hydrogen-bond donor) for complex 1, 2.620(5) Å, 153.28 for 2 and 2.589(3) Å, 164.08 and 2.624(3) Å, 152.88 for 3.The bond length diVerences of the C]O at the acetate group are trivial in complexes 1 (0.009 Å) and 2 (0.014 Å) due to the hydrogen-bond eVect, giving rise toJ. Chem. Soc., Dalton Trans., 1998, Pages 2827–2831 2829 Table 2 Selected bond distances (Å) and angles (8)* Complex 1 Ni(1)]O(1w) Ni(1)]N(1) Ni(1)]O(1) O(1)]C(6) N(1)]Ni(1)]N(1a) N(1a)]Ni(1)]O(1) O(1wa)]Ni(1)]N(1) N(1)]Ni(1)]O(1w) O(1)]Ni(1)]O(1w) O(1w)]H(1A) ? ? ? O(2a) H(1B)]O(1w)]H(1A) 2.082(2) 2.069(2) 2.079(2) 1.253(3) 78.97(13) 90.80(8) 171.61(8) 93.42(9) 92.54(8) 153.2 104.9 C(6)]O(2) O(2a) ? ? ? O(1w) O(2b) ? ? ? O(1w) N(1)]Ni(1)]O(1) O(1)]Ni(1)]O(1a) O(1w)]Ni(1)]O(1wa) O(1)]Ni(1)]O(1wa) O(1)]C(6)]O(2) O(1w)]H(1B) ? ? ? O(2b) 1.244(4) 2.620(3) 2.776(3) 88.67(8) 179.31(11) 94.39(11) 87.93(8) 124.7(3) 155.6 Symmetry codes: a 2x, y, 2z 1 ��� ; b 2x, 1 2 y, 1 2 z.Complex 2 Ni(1)]O(1w) Ni(1)]N(1) Ni(1)]O(1) O(1)]C(7) N(1)]Ni(1)]N(1a) N(1)]Ni(1)]O(1w) N(1)]Ni(1)]O(1a) N(1)]Ni(1)]O(1) O(1a)]Ni(1)]O(1) O(1w)]H(1A) ? ? ? O(2a) H(1B)]O(1w)]H(1A) 2.077(3) 2.067(4) 2.077(3) 1.266(5) 78.57(19) 93.52(13) 91.38(13) 87.59(13) 178.67(17) 153.2 103.0 O(2)]C(7) O(2a) ? ? ? O(1w) O(2b) ? ? ? O(1w) N(1)]Ni(1)]O(1wa) O(1wa)]Ni(1)]O(1w) O(1w)]Ni(1)]O(1a) O(1w)]Ni(1)]O(1) O(2)]C(7)]O(1) O(1w)]H(1B) ? ? ? O(2b) 1.252(5) 2.620(5) 2.788(5) 170.87(13) 94.71(17) 88.06(13) 92.84(13) 123.8(5) 162.5 Symmetry codes: a 2x, y, ��� 2 z; b 1 2 x, 1 2 y, 2z.Complex 3 Ni(1)]O(1w) Ni(1)]O(2w) Ni(1)]N(1) Ni(1)]N(2) Ni(1)]O(1) Ni(1)]O(3) O(1)]C(13) O(2)]C(13) O(3)]Ni(1)]N(2) N(2)]Ni(1)]N(1) N(2)]Ni(1)]O(2w) O(3)]Ni(1)]O(1w) N(1)]Ni(1)]O(1w) O(3)]Ni(1)]O(1) N(1)]Ni(1)]O(1) O(1w)]Ni(1)]O(1) O(3)]C(15)]O(4) O(2w)]H(2A) ? ? ? O(4) O(2w)]H(2B) ? ? ? O(1b) H(2A)]O(2w)]H(2B) 2.073(2) 2.072(2) 2.072(2) 2.068(2) 2.075(2) 2.033(2) 1.270(3) 1.237(3) 172.83(8) 79.73(8) 86.27(8) 87.57(7) 89.66(7) 89.87(8) 176.43(8) 90.77(7) 125.6(2) 152.8 166.0 106.9 O(3)]C(15) O(4)]C(15) O(1w) ? ? ? O(2) O(1wa) ? ? ? O(4) O(1) ? ? ? O(2wb) O(2w) ? ? ? O(4) O(3w) ? ? ? O(1w) O(3)]Ni(1)]N(1) O(3)]Ni(1)]O(2w) N(1)]Ni(1)]O(2w) N(2)]Ni(1)]O(1w) O(2w)]Ni(1)]O(1w) N(2)]Ni(1)]O(1) O(2w)]Ni(1)]O(1) O(1)]C(13)]O(2) O(1w)]H(1A) ? ? ? O(2) O(1w)]H(1B) ? ? ? O(4a) H(1A)]O(1w)]H(1B) O(1w) ? ? ? O(3w) ? ? ? O(1wc) 1.242(3) 1.251(3) 2.589(3) 2.770(3) 2.788(3) 2.624(3) 2.885 93.69(8) 90.94(7) 90.01(7) 95.16(8) 178.45(7) 96.70(7) 89.65(7) 124.6(2) 164.0 170.9 98.2 155.62 Symmetry codes: a 1 1 x, y, z; b 2x, 2y, 2z; c 1 2 x, 2y, 1 2 z.* A and B represent geometrically generated hydrogen atoms. what may be regarded as a ‘pseudo-bridging’ arrangement of the terminal acetate group.18 This is also observed in complex 3, in which the diVerence between C(15)]O(4) and C(15)]O(3) is 0.009 Å. The distance C(13)]O(1) [1.270(3) Å] is significantly longer than C(13)]O(2) [1.237(3) Å], due to the co-ordinated O(1) atom forming an intermolecular hydrogen bond with O(2wb) from an adjacent aqua ligand. The crystal structures of complexes 1 and 2 consist of similar two-dimensional organizations.Interestingly, the hydrophilic groups recognize each other via intermolecular hydrogen bonds to form one-dimensional infinite zigzag chains viewed along the a axis as shown in Fig. 3. Each pair of aqua ligands forms a donor hydrogen bond with an unco-ordinated acetate oxygen atom from an adjacent molecule, while each pair of uncoordinated acetate oxygen atoms forms an acceptor hydrogen bond with an aqua ligand from the adjacent molecule.Each molecule is associated with two adjacent molecules each through one donor and one acceptor hydrogen bond, i.e. of the AD]] DA type, giving one-dimensional chains in the lattice (see Fig. 3). In these chains the hydrogen bonds are 2.77 (D]H? ? ?A 155.68) and 2.78 Å (162.58) for complexes 1 and 2, respectively.The Ni ? ? ? Ni intermolecular distances bridged by these double hydrogen bonds are 7.08 Å for complex 1 and 7.06 Å for complex 2, and the distances between every second Ni21 in the chain are 8.14 Å for 1 and 8.1r 2. It is also interesting that, in complexes 1 and 2, the hydrophobic bipyridyl groups are thus alternatively extended outwards at both sides of the chain; each pair of adjacent bipyridyl groups at the same side forms one pitch of the chain, and is virtually oriented in a parallel fashion with a separation at 7.02 and 7.31 Å for complexes 1 and 2, respectively.Intercalation of each bipyridyl group at one side of a chain into each pit of an adjacent chain in a zipper-like2830 J. Chem. Soc., Dalton Trans., 1998, Pages 2827–2831 fashion extends the structure into a two-dimensional network, where the close interchain bipyridyl groups, being arranged in an oV-set fashion, have an average face-to-face distance of 3.44 Å for complex 1 and 3.60 Å for 2, respectively, showing significant p–p stacking interaction.9,10,14 The chain-to-chain spacing (13.34 Å) and the interchain bipyridyl stacking distance (3.60 Å) in complex 2 are both markedly larger than the corresponding values in 1 (12.70 and 3.44 Å), which can be attributed to the repulsion of the methyl groups of dmbipy in complex 2.The crystal structure of complex 3 is very diVerent from that of 1 and 2. One aqua ligand donates an intermolecular hydrogen bond to an unco-ordinated acetate oxygen atom from an adjacent molecule with A ? ? ? D 2.770(3) Å (D]H? ? ? A 170.98), forming a one-dimensional single chain, as shown in Fig. 4. Within this chain the Ni ? ? ? Ni distance is 7.54 Å. The single chain is further associated with another single chain through double hydrogen bonds between the other aqua ligand and one of the co-ordinated acetate oxygen atoms [O(1) ? ? ? O(2wb) 2.788(3) Å, D]H? ? ? A 166.08] (Fig. 4), giving rise to a double chain supported by 5.2 Å. These double chains are further assembled via hydrogen bonds and p–p stacking interactions. Every lattice water is connected to two aqua ligands from two double chains by hydrogen bonds at O(3w) ? ? ? O(1w) 2.885 Å, O(1w) ? ? ? O(3w) ? ? ? O(1wc) 155.68 (Fig. 4). The aqua mol- Fig. 1 An ORTEP19 view (35% probability) of the molecular structure of complex 1 with the intramolecular hydrogen bonds and atomnumbering scheme Fig. 2 An ORTEP view of the molecular structure of complex 3. Details as in Fig. 1 ecule O(1w) not only co-ordinates to Ni21 but also donates two hydrogen bonds to two oxygen atoms of acetates, and additionally accepts a hydrogen bond from the lattice water. In these double chains the hydrophobic phen rings are oriented outwards in a similar fashion to that found in both complexes 1 and 2, and therefore resulting in analogous intercalation into the adjacent double chains. The interchain stacking interaction between the phen is also in an oV-set fashion with average face-to-face distances of 3.34 and 3.24 Å, showing markedly stronger interaction between the phen ligands in complex 3 than those between the bipyridyl ligands in 1 (3.44 Å) and 2 (3.60 Å).This may be ascribed to the larger p system in the phen ligand. Such stronger p–p interactions result in the diVerent geometries and packing arrangements of complexes 3 and 1 and 2. In 3 the bulky acetate groups (relative to water) occupy the equatorial plane (see above) to meet the needs of space for the stronger p–p stacking, and result in the diVerent intermolecular hydrogen bonds and the diVerent structural arrangements.The Ni ? ? ? Ni distance bridged by double hydrogen bonds is 5.46 Å, and the interchain spacing between the double chains is 13.17 Å in complex 3. Fig. 3 View of the packing and double hydrogen-bond-linked zigzag chains in complex 1 along the a axis Fig. 4 View of the two-dimensional network in complex 3 along the b axisJ. Chem. Soc., Dalton Trans., 1998, Pages 2827–2831 2831 Conclusion Three monomeric nickel complexes have been synthesized and characterized by single-crystal X-ray diVraction methods. The complexes were self-assembled into two dimensional networks via intermolecular hydrogen bonds and p–p stacking interactions. The structures described demonstrated that intermolecular hydrogen bonds and aromatic ring interactions have enormous potential for assembling multicomponent systems in which the subunits are metal complexes.This contribution adds several new features to the fast developing field of supramolecular chemistry and aids in the fundamental understanding of molecular recognition and systematic rationalization of molecular aggregation in inorganic crystal engineering. Acknowledgements This work was supported by the NSFC and the Ministry of Education of China. References 1 See, for examples, J.-M.Lehn, Angew. Chem., Int. Ed. Engl., 1988, 27, 89; 1990, 29, 1304. 2 (a) C. B. Aakeröy and K. R. Seddon, Chem. Soc. Rev., 1993, 22, 397; (b) S. Subramanian and M. J. Zaworotko, Coord. Chem. Rev., 1994, 137, 357; (c) A. D. Burrows, C.-W. Chan, M. M. Chowdhry, J. E. McGrady and D. M. P. Mingos, Chem. Soc. Rev., 1995, 329; (d) M. Munakata, L. P. Wu and T. Kuroda-Sowa, Bull. Chem. Soc. 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Matsuda, S. Akiyama and M. Maekawa, J. Chem. Soc., Dalton Trans., 1995, 2201. 11 G. M. Sheldrick, SHELXS 97, Program for Crystal Structure Solution, University of Göttingen, 1997. 12 G. M. Sheldrick, SHELXL 97, Program for Crystal Structure Refinement, University of Göttingen, 1997. 13 See, for examples, J. B. Vincent, H.-L. Tsai, A. G. Blackman, S. Wang, P. D. W. Boyd, K. Folting, J. C. HuVman, E. B. Lobkovsky, D. N. Hendrickson and G. Christou, J. Am. Chem. Soc., 1993, 115, 1253; K. Dimitrou, K. Folting, W. E. Streib and G.Christou, J. Am. Chem. Soc., 1993, 115, 6432; S.-B. Yu, S. J. Lippard, I. Shweky and A. Bino, Inorg. Chem., 1992, 31, 3502; M. Corbella, R. Costa, J. Ribas, P. H. Fries, J.-M. Latour, L. Öhrström, X. Solans and V. Rodríguez, Inorg. Chem., 1996, 35, 1857. 14 T. Sugimori, H. Masuda, N. Ohata, K. Koiwai, A. Odani and O. Yamauchi, Inorg. Chem., 1997, 36, 576; O. Yamauchi, A. Odani, A. Masuda and H. Sigel, Met. Ions Biol. Syst., 1996, 32, 207. 15 R. L. Rardin, A. Bino, P. Poganiuch, W.B. Tolman, S. Liu and S. J. Lippard, Angew. Chem., Int. Ed. Engl., 1990, 29, 812; S. Ménage, S. E. Vitols, P. Bergerat, E. Codjovi, O. Kahn, J.-J. Girerd, M. Guillot, X. Solans and T. Calvet, Inorg. Chem., 1991, 30, 2666; B.-H. Ye, F. Xue and T. C. W. Mak, unpublished work. 16 B.-H. Ye, X.-M. Chen and L.-N. Ji, unpublished work. 17 X.-M. Chen, Y.-X. Tong and T. C. W. Mak, Inorg. Chem., 1994, 33, 4586; G. Christou, S. P. Perlepes, E. Libby, K. Folting, J. C. HuVman, R. J.Webb and D. N. Hendrickson, Inorg. Chem., 1990, 29, 3657. 18 G. B. Deacon and R. J. Phillips, Coord. Chem. Rev., 1980, 33, 227. 19 C. K. Johnson, ORTEP, Report ORNL-5138, Oak Ridge National Laboratory, Oak Ridge, TN, 1976. 20 M. Melnik, T. Sramko, M. Dunaj-Jurco, A. Sirota and C. E. Holloway, Rev. Inorg. Chem., 1994, 14, 1. Received 9th April 1998; Paper 8/02695EJ. Chem. Soc., Dalton Trans., 1998, Pages 2827–2831 2831 Conclusion Three monomeric nickel complexes have been synthesized and characterized by single-crystal X-ray diVraction methods.The complexes were self-assembled into two dimensional networks via intermolecular hydrogen bonds and p–p stacking interactions. The structures described demonstrated that intermolecular hydrogen bonds and aromatic ring interactions have enormous potential for assembling multicomponent systems in which the subunits are metal complexes. This contribution adds several new features to the fast developing field of supramolecular chemistry and aids in the fundamental understanding of molecular recognition and systematic rationalization of molecular aggregation in inorganic crystal engineering.Acknowledgements This work was supported by the NSFC and the Ministry of Education of China. References 1 See, for examples, J.-M. Lehn, Angew. Chem., Int. Ed. Engl., 1988, 27, 89; 1990, 29, 1304. 2 (a) C. B. Aakeröy and K. R. Seddon, Chem. Soc. Rev., 1993, 22, 397; (b) S. Subramanian and M.J. Zaworotko, Coord. Chem. Rev., 1994, 137, 357; (c) A. D. Burrows, C.-W. Chan, M. M. Chowdhry, J. E. McGrady and D. M. P. Mingos, Chem. Soc. Rev., 1995, 329; (d) M. Munakata, L. P. Wu and T. Kuroda-Sowa, Bull. Chem. Soc. Jpn., 1997, 70, 1727. 3 M. M. Chowdhry, D. M. P. Mingos, A. J. P. White and D. J. Williams, Chem. Commun., 1996, 899. 4 A. D. Burrows, D. M. P. Mingos, A. J. P. White and D. J. Williams, Chem. Commun., 1996, 97; J. Chem. Soc., Dalton Trans., 1996, 149. 5 A. Neels, B. M. Neels, H. Stoeckli-Evans, A. Clearfield and D. M. Poojary, Inorg. Chem., 1997, 36, 3402. 6 S. Kawata, S. R. Breeze, S. Wang, J. E. Greedan and N. P. Raju, Chem. Commun., 1997, 717. 7 A. J. Blake, S. J. Hill, P. Hubberstey and W.-S. Li, J. Chem. Soc., Dalton Trans., 1997, 913. 8 L. Carlucci, G. Ciani, D. M. Proserpio and A. Sironi, J. Chem. Soc., Dalton Trans., 1997, 1801. 9 M. Munakata, L. P. Wu, M. Yamamoto, T. Kuroda-Sowa and M. Maekawa, J. Am. Chem. Soc., 1996, 118, 3117. 10 J. Dai, M. Yamamoto, T. Kuroda-Sowa, M. Maekawa, Y. Suenaga and M. Munakata, Inorg. Chem., 1997, 36, 2688; M. Munakata, J. Dai, M. Maekawa, T. Kuroda-Sowa and J. Fukui, J. Chem. Soc., Chem. Commun., 1994, 2331; T. Kuroda-Sowa, M. Munakata, H. Matsuda, S. Akiyama and M. Maekawa, J. Chem. Soc., Dalton Trans., 1995, 2201. 11 G. M. Sheldrick, SHELXS 97, Program for Crystal Structure Solution, University of Göttingen, 1997. 12 G. M. Sheldrick, SHELXL 97, Program for Crystal Structure Refinement, University of Göttingen, 1997. 13 See, for examples, J. B. Vincent, H.-L. Tsai, A. G. Blackman, S. Wang, P. D. W. Boyd, K. Folting, J. C. HuVman, E. B. Lobkovsky, D. N. Hendrickson and G. Christou, J. Am. Chem. Soc., 1993, 115, 1253; K. Dimitrou, K. Folting, W. E. Streib and G. Christou, J. Am. Chem. Soc., 1993, 115, 6432; S.-B. Yu, S. J. Lippard, I. Shweky and A. Bino, Inorg. Chem., 1992, 31, 3502; M. Corbella, R. Costa, J. Ribas, P. H. Fries, J.-M. Latour, L. Öhrström, X. Solans and V. Rodríguez, Inorg. Chem., 1996, 35, 1857. 14 T. Sugimori, H. Masuda, N. Ohata, K. Koiwai, A. Odani and O. Yamauchi, Inorg. Chem., 1997, 36, 576; O. Yamauchi, A. Odani, A. Masuda and H. Sigel, Met. Ions Biol. Syst., 1996, 32, 207. 15 R. L. Rardin, A. Bino, P. Poganiuch, W. B. Tolman, S. Liu and S. J. Lippard, Angew. Chem., Int. Ed. Engl., 1990, 29, 812; S. Ménage, S. E. Vitols, P. Bergerat, E. Codjovi, O. Kahn, J.-J. Girerd, M. Guillot, X. Solans and T. Calvet, Inorg. Chem., 1991, 30, 2666; B.-H. Ye, F. Xue and T. C. W. Mak, unpublished work. 16 B.-H. Ye, X.-M. Chen and L.-N. Ji, unpublished work. 17 X.-M. Chen, Y.-X. Tong and T. C. W. Mak, Inorg. Chem., 1994, 33, 4586; G. Christou, S. P. Perlepes, E. Libby, K. Folting, J. C. HuVman, R. J. Webb and D. N. Hendrickson, Inorg. Chem., 1990, 29, 3657. 18 G. B. Deacon and R. J. Phillips, Coord. Chem. Rev., 1980, 33, 227. 19 C. K. Johnson, ORTEP, Report ORNL-5138, Oak Ridge National Laboratory, Oak Ridge, TN, 1976. 20 M. Melnik, T. Sramko, M. Dunaj-Jurco, A. Sirota and C. E. Holloway, Rev. Inorg. Chem., 1994, 14, 1. Received 9th April 1998; Paper 8/02695E

ISSN:1477-9226    

DOI:10.1039/a802695e

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, Pages 2833–2838 2833 Structural studies of [Pt(CNMe)4][M(mnt)2]n {M 5 Pd or Pt, mnt 5 [S2C2(CN)2]22, n 5 1 or 2}: structure-dependent paramagnetism of three crystal forms of [Pt(CNMe)4][Pt(mnt)2]2 Hugues Bois,a Neil G. Connelly,*,†,a John G. Crossley,a Jean-Christophe Guillorit,a Gareth R. Lewis,a A. Guy Orpen *,a and Peter Thornton b a School of Chemistry, University of Bristol, Bristol, UK BS8 1TS b Department of Chemistry, Queen Mary and Westfield College, Mile End Road, London, UK E1 4NS The reaction of [NEt4]2[Pt(mnt)2] {mnt = [S2C2(CN)2]22} with [Pt(CNMe)4][PF6]2 gave the diamagnetic ‘stacked’ salt [Pt(CNMe)4][Pt(mnt)2].In acetonitrile, nitromethane and nitropropane solution respectively, treatment of [NEt4][Pt(mnt)2] with [Pt(CNMe)4][PF6]2 yielded three diVerent crystal forms of the salt of 1 : 2 stoichiometry: [Pt(CNMe)4][Pt(mnt)2]2?2MeCN, [Pt(CNMe)4][Pt(mnt)2]2?MeNO2 and [Pt(CNMe)4][Pt(mnt)2]2.These show structure-dependent antiferromagnetism, reflecting diVering arrangements of the formally platinate(III) anions [Pt(mnt)2]2 within the crystal lattice. The palladium salts [Pt(CNMe)4][Pd(mnt)2] and [Pt(CNMe)4][Pd(mnt)2]2? 2MeCN are isomorphous with their platinum analogues. Low dimensional molecular solids have attracted widespread interest because of the prospect of novel electrical, optical and magnetic properties. Perhaps the most studied classes of onedimensional transition metal complexes 1 are the partially oxidised square planar tetracyanoplatinates,2 e.g.K2[Pt(CN)4]- Cl0.3?3H2O, and related complexes containing two bidentate dithiolate dianions 3 such as [S2C2(CN)2]22 (mnt). The structural and physical (electrical conductivity and magnetism) properties of salts of [M(mnt)2]z2 complexes with simple cations such as K1 and [NH4]14 or organic cations such as that of perylene 5 and [BEDT-TTF]1 [BEDT-TTF = bis- (ethylenedithio)tetrathiafulvalene; tetrathiafulvalene = 2-(1,3- dithiol-2-ylidene)-1,3-dithiole] 6 have been well studied. By contrast, salts with a transition metal complex as the counter cation are less well known but of obvious potential, as exemplified by [Au(ttp)][M(mnt)2] (M = Ni, Pt or Au; ttp = 5,10,15,20- tetraphenylporphyrinate),7 [Fe(h-C5Me5)2][M(mnt)2] (M = Ni or Pt) (which show ferromagnetic behaviour),8 [Cr(h- C6H6)2]2[Ni(mnt)2],9 [Fe(h-C5H4R)2]2[Ni(mnt)2], (R = H10 or CH]] CHC6H4EMe-4, E = O or S, etc.11) and [Fe(h-C5H5)(h6- C6H5Me)]2[Ni(mnt)2].10,12 Our preliminary studies 13 in this area showed that the square planar ions [Pt(CNMe)4]21 and [M(mnt)2]z2 (M = Pd, z = 1 or 2; M = Au, z = 1) give salts with crystal structures which depend on both the charge of the anion and its magnetic state and which show low dimensional motifs (layers and stacks).Here we describe detailed structural and magnetic studies of [Pt- (CNMe)4][M(mnt)2], [Pt(CNMe)4][M(mnt)2]2?2MeCN (M = Pd or Pt), [Pt(CNMe)4][Pt(mnt)2]2?MeNO2 and [Pt(CNMe)4]- [Pt(mnt)2]2. Results and Discussion Synthesis of complex salts The salts [Pt(CNMe)4][Pt(mnt)2] and [Pt(CNMe)4][Pt(mnt)2]2 are prepared by metathesis reactions between [Pt(CNMe) 4][PF6]2 and 1 equivalent of [NEt4]2[Pt(mnt)2] or 2 equivalents of [NEt4][Pt(mnt)2], each dissolved in an appropriate polar solvent.For each complex salt the reaction was carried † E-Mail: Neil.connelly@bristol.ac.uk out in two ways.First, stirring solutions of the reactants together on a preparative scale gave the products as precipitates, generally as powders. Secondly, allowing solutions of the reactants to diVuse together slowly provided crystals suitable for X-ray diVraction studies. The crystal structure and magnetic behaviour of the products were crucially dependent on solvent incorporation in the lattice. Thus, in the reaction between [Pt(CNMe)4][PF6]2 and [NEt4][Pt(mnt)2] three crystals forms were isolated, namely [Pt(CNMe)4][Pt(mnt)2]2?2MeCN (from MeCN), [Pt(CNMe) 4][Pt(mnt)2]2?MeNO2 (from MeNO2) and [Pt(CNMe)4][Pt- (mnt)2]2 (from PrnNO2) (Table 1).Magnetic studies were therefore carried out only on crystalline samples for which the unit cell dimensions of representative single crystals were verified to ensure identity with samples taken for single crystal X-ray diVraction studies. Crystal structural studies Aspects of the crystal structures of the salts [Pt(CNMe)4]- [Pt(mnt)2] 1, [Pt(CNMe)4][Pd(mnt)2] 2,13 [Pt(CNMe)4][Pt- (mnt)2]2?2MeCN 3, [Pt(CNMe)4][Pd(mnt)2]2?2MeCN 4,13 [Pt(CNMe)4][Pt(mnt)2]2?MeNO2 5 and [Pt(CNMe)4][Pt(mnt)2]2 6 are shown in Figs. 1–9; selected structural data are summarised in Table 2.Molecular structures of the constituent ions. In salts 1–6 the diamagnetic dication [Pt(CNMe)4]21 comprises a square planar d8 platinum(II) core with nearly linear (apart from the methyl hydrogen atoms) methyl isocyanide ligands; the average Pt]C bond lengths (Table 2) are comparable with that found in [Pt(CNMe)4][PF6]2.14 The bond distances within the square planar anions of 1–6 (Table 2) are likewise consistent with those found in the crystal structures of the salts [NEt4][Pt(mnt)2] 15 and [NBun 4]2[Pt(mnt)2].16 Thus, d8 MII]S bonds are slightly longer than d7 MIII]S bonds.{For simplicity, throughout this paper formal oxidation states of II and III are assigned to the metal atoms of [M(mnt)2]22 and [M(mnt)2]2 (M = Pd or Pt) respectively.} In other respects the ions have the expected approximately square planar geometry at the metal and there are no substantial distortions of the ligands from their usual dimensions.The Pt atoms in 1–3 lie slightly out of the S4 plane (Table 2) as a result of the ‘dish’ distortion of the Pt(mnt)2 unit.2834 J. Chem. Soc., Dalton Trans., 1998, Pages 2833–2838 Table 1 Analytical data for complexes 1–6 Analysis (%) b Complex 1 [Pt(CNMe)4][Pt(mnt)2] 2 [Pt(CNMe)4][Pd(mnt)2] 3 [Pt(CNMe)4][Pt(mnt)2]2?2MeCN 4 [Pt(CNMe)4][Pd(mnt)2]2 5 [Pt(CNMe)4][Pt(mnt)2]2?MeNO2 6 [Pt(CNMe)4][Pt(mnt)2]2 State a P CP CCP c CC d Colour Dark red Dark red Yellow-green Yellow-green Black Black Black Black Yield (%) 71 61 63 48 79 52 67 25 C 23.2 (23.0) 22.9 (23.0) 25.6 (25.8) 26.0 (25.8) 24.2 (24.2) 25.0 (25.4) 22.1 (21.9) 22.0 (22.0) H 1.5 (1.5) 1.4 (1.5) 1.6 (1.6) 1.4 (1.6) 1.2 (1.3) 1.1 (1.1) 0.9 (1.1) 1.1 (0.9) N 13.4 (13.4) 13.5 (13.4) 14.9 (15.0) 15.0 (15.0) 13.9 (14.1) 14.3 (14.8) 13.0 (13.3) 12.8 (12.8) a P = Powder, C = crystals.b Calculated values in parentheses. c Precipitated powder, unresolved. d From PrnNO2. Crystal structures of salts 1–6. The two ions of [Pt(CNMe) 4][Pt(mnt)2] 1 are arranged such that the metal atoms form an infinite anion–cation one-dimensional stack of type . . . A22C21A22C21A22C21. . . (A = anion, C = cation) along the b axis (Fig. 1) with a Pt ? ? ? Pt distance of b/2, i.e. 3.328 Å, and a Pt]Pt]Pt angle of 1808. Ions of like charge have an eclipsed ligand arrangement along the stack. The ions form layers parallel to the ac plane of the unit cell (Fig. 2) such that there are segregated homomolecular ribbons of anions and cations along c. Each anion is therefore in face-to-face contact with two cations and edge-on contact with two further cations as well as two anions; cations have the converse pattern of contacts. There are also CH ? ? ?N]] ] C contacts in the layers of ca. 2.6 Å. Fig. 1 Crystal structure of complex 1 perpendicular to the b axis. Hydrogen atoms have been omitted for clarity Fig. 2 Crystal structure of complex 1 as viewed along the b axis. Details as in Fig. 1 As seen in Table 3, [Pt(CNMe)4][Pd(mnt)2] 2 is strictly isostructural with 1, with palladium atoms replacing platinum in the anions of 1. The location, site symmetry and geometry of the ions are essentially identical to those described above, with the Pt ? ? ? Pd separation along the metal–metal chain 3.307 Å.Substituting the diamagnetic d8 dianions in complexes 1 and 2 by paramagnetic, formally d7, [M(mnt)2]2 monoanions causes a change in the stoichiometry of the salt and a dramatic eVect on the crystal structure. Moreover, the extensive structural modifications brought about by lattice solvation in the three crystal forms 3, 5 and 6 result in substantial changes in bulk magnetic behaviour. The crystal structure of [Pt(CNMe)4][Pt(mnt)2]2?2MeCN 3 comprises two separate repeating motifs (Fig. 3) formed by the complex ions in addition to the solvent molecules which lie in Fig. 3 Crystal structure of complex 3 as viewed along the a axis. Solvent and hydrogen atoms have been omitted for clarity Fig. 4 Crystal structure of complex 3 as viewed along the b axis. Details as in Fig. 3J. Chem. Soc., Dalton Trans., 1998, Pages 2833–2838 2835 the interstices in the array of ions. Face-to-face cationic chains consisting of alternating dication pairs and anion dimers (i.e.of type . . . A2A2C21C21A2A2C21C21. . .) run along the b axis of the crystallographic unit cell at x = 0, z = 0.5 and x = 0.5, z = 0. In these chains, the two dications are mutually slipped; the angle of slippage (defined as the angle made by the Pt ? ? ? Pt vector to the perpendicular to the PtL4 square plane) is 34.5(4)8 and the PtII ? ? ? PtII separation is 4.272(8) Å. Each dication is, in turn, slipped by 22.6(3)8 with respect to the neighbouring [Pt(mnt)2]2 anion.The closest PtII ? ? ? PtIII separation, between dication and anion, is 3.514(6) Å. The anions in the chain form weak face-to-face dimers with a PtIII ? ? ? PtIII separation of Fig. 5 Crystal structure of complex 5 as viewed along the c axis. Details as in Fig. 3 Fig. 6 Cationic chains in the crystal structure of complex 5 as viewed along the a axis. Details as in Fig. 3 Fig. 7 Anion layers in the bc plane in the crystal structure of complex 5 as viewed along the a axis.Details as in Fig. 3 3.507(6) Å; the angle of slippage is only 1.6(2)8, i.e. the anions are nearly perfectly eclipsed. The b-axis chains are linked by weak Pt ? ? ? S contacts [3.860(6) Å] (Fig. 4) to anion dimers which are similar to those in the b-axis chain but more internally slipped, so giving a much greater intradimer Pt ? ? ? Pt distance [4.252(8) Å] and an angle of slippage of 28.6(3)8. Substituting the d7 platinate anion [Pt(mnt)2]2 of complex 3 by the d7 palladate anion [Pd(mnt)2]2 of 4 has little eVect on the overall crystal structure.As seen in Table 3 crystals of the two salts, as their acetonitrile solvates, are strictly isostructural. The palladium–palladium distances in 4 within the two types of anion dimer are slightly shorter [i.e. Pd ? ? ? Pd 3.421(5) Å (in the b-axis chain) and 4.240(6) Å (in the isolated dimers)] than in the corresponding platinum anion pairs. As seen in Figs. 5 and 6, the solvation of [Pt(CNMe)4]- [Pt(mnt)2]2 by MeNO2 in 5 (cf. 2MeCN in 3) results in a markedly diVerent structure. The crystal structure of 5 contains two types of ion arrangement. Chains of alternating [Pt(mnt)2]2 and [Pt(CNMe)4]21 ions, of the form . . . A2C21A2C21A2C21. . ., may be observed parallel to the c axis (Figs. 5 and 6). In these cationic chains, therefore, the paramagnetic anions are isolated from other paramagnetic centres. One sulfur of the anion is closest to the metal atom of the adjacent dication, at a distance of 3.657(8) Å and with an angle of slippage of 16.6(3)8.In turn, the metal atom of the dication lies 3.310(7) Å above the platinum of the next neighbouring anion. In addition a layer of [Pt(mnt)2]2 anions is formed in the bc plane at x = 0, 1, 2, etc. (Fig. 7) in which the anions lie face-to-face, forming an array in which highly slipped ‘chains’ may be identified with closest PtIII ? ? ? PtIII separations of 7.454(7) and 7.582(8) Å.However, there are shorter PtIII ? ? ? PtIII contacts (6.641 Å) between anions in the chains and layers. Thus, there are two diVerent magnetic Fig. 8 Neutral chains along the b axis of the crystal structure of complex 6 as viewed along the c axis. Details as in Fig. 1 Fig. 9 Neutral chains along the a axis of the crystal structure of complex 6 as viewed along the c axis. Details as in Fig. 12836 J. Chem. Soc., Dalton Trans., 1998, Pages 2833–2838 Table 2 Selected average bond and interatomic lengths (Å) and angles (8) for complexes 1–6 Cation Average PtII]Ca Average cis C]PtII]C Average PtII]N]C 1 1.991(4) b 89.50(2) 175.7(4) 2 1.968(6) 90.00(1) 179.4(2) 3 1.972(12) 88.4(4) 172.0(7) 4 1.979(1) 90.0(1) 177.4(1) 5 2.005(5) 90.00(8) 177.9(8) 6 1.957(2) 91.32(3) 176.1(2) Anion Average M]Sc Average cis S]M]S Deviation of M from MS4 square plane 2.311(1) 90.2(2) 0.0(0) 2.304(2) 90.0(2) 0.0(0) 2.271(2) 90.0(7) 0.0303(4) 0.0299(4) 2.275(1) 90.0(3) 0.0351(3) 0.0245(3) 2.268(3) 90.1(6) 0.0860(3) 0.0340(2) 2.257(3) 90.0(1) 0.0270(2) 0.0170(2) a Literature value = 1.980 Å.14 b Typical standard uncertainties in the last digit of individual values are given in parentheses.c Literature values: Pt]S in [Pt(mnt)2]2 2.266 Å;15 in [Pt(mnt)2]22 2.283 Å;16 Pd]S in [Pd(mnt)2]2 2.278 Å.4c environments for the platinum(III) centres within the crystals of 5 (see below) and the large separations between the paramagnetic centres seem likely to provide an insulating environment for the anions.As in 4 the solvent molecules lie in the interstices of the array of ions in 5. The unsolvated crystal structure of complex 6 (Figs. 8 and 9) once again contains anion dimers. However, in this case the dimers are separated only by single dications thereby forming neutral chains of the form . . . A2A2C21A2A2C21A2A2C21. . . . Two such chains are formed, one parallel to the b axis and a second, more weakly associated, along the a axis.In the b axis chain (Fig. 8) the dimers are only slightly slipped, at an angle of 7.2(3)8, and the PtIII ? ? ? PtIII distance is 3.859(8) Å. The [Pt- (CNMe)4]21 dication is slightly staggered with respect to the anion dimer, and aligned such that the platinum(II) centre is below the sulfur atom of an mnt ligand, at a Pt ? ? ? S distance of 3.490(8) Å, and at an angle of slippage of 14.2(3)8. In the a axis chain (Fig. 9) the PtIII ? ? ? PtIII distance is longer and more slipped [at 5.433(7) Å and 19.2(3)8] and the PtII ? ? ? PtIII distance shorter and less slipped [at 3.742(5) Å and 17.1(3)8]. Fig. 10 Magnetic susceptibility vs. temperature for complex 3. Experimental points, squares; calculated values, filled circles and line, see text Magnetic susceptibility studies on [Pt(CNMe)4][Pt(mnt)2]2? 2MeCN 3, [Pt(CNMe)4][Pt(mnt)2]2?MeNO2 5 and [Pt(CNMe)4]- [Pt(mnt)2]2 6 The magnetic susceptibilities of the salts 3, 5 and 6 were measured by the Faraday method from 74 to 294 K. The c vs.T plots are shown in Figs. 10–12. Temperature independent paramagnetism is accounted for by the inclusion of a correction term, 8Nb2/D, with D for [Pt(mnt)2]2 measured from the electronic spectrum as 11 700 cm21,3a giving a second order molar susceptibility of 1.80 × 1024 cm3 mol21. Each of the crystal forms is antiferromagnetic, but the extent of antiferromagnetism reflects the diVerent structures. The bis(acetonitrile) solvate 3 contains two types of well separated platinate(III) anion dimers (see above, Figs. 3 and 4). Its magnetism is well described using the Bleaney–Bowers equation 17 with a value of J, the magnetic interaction parameter, of 280 cm21 (Fig. 10). A value of 2.000 was assumed for g; a higher value to include some spin–orbit coupling gives a poorer fit below 150 K. The fit of theory to experiment is Fig. 11 Magnetic susceptibility vs. temperature for complex 6. Details as in Fig. 10J. Chem. Soc., Dalton Trans., 1998, Pages 2833–2838 2837 not exact, but in the available temperature range all the experimental points are within two standard deviations of the theoretical curve. Compound 6, the unsolvated salt obtained from nitropropane solution, also contains platinate(III) anion dimers (albeit of two markedly diVerent types in approximately orthogonal chains) and might therefore be expected to show similar behaviour to that of 3. However, it can be seen from Fig. 11 that the susceptibility decreases more rapidly at lower temperatures than the Bleaney–Bowers theory for an S = ��� dimer predicts, using the best J value of 2135 cm21. This may be attributthe possibility of interdimer coupling to give an alternating chain with additional antiferromagnetism between dimeric anions through orbital overlap with the dications. This additional antiferromagnetism will be more prominent at lower temperatures. It is noteworthy that the intradimer coupling constant in 6 is much greater than for 3, despite the distance between platinum(III) atoms being much longer.It may be that for 6 exchange mediated through the dication is greater in magnitude than that between two anions which are not apparently insulated by a dication and that, magnetically speaking, 6 should be considered as a dimer of monoanions bridged by a dication. We consider it premature to compute an additional exchange parameter to represent the minor coupling in advance of data for lower temperatures; these might well give a maximum in the susceptibility vs.temperature curve at about 50 K. The nitromethane solvate 5 contains a polymeric layer of faceto- face platinum(III) ions, each with spin of ��� , with additional separate platinate(III) anions in the cationic stack. For an infinite chain of spins of ��� interacting antiferromagnetically the formula derived by Bonner and Fisher 18 applies [equation (1)] c = Nag2b2 kT 0.25 1 0.074 974x 1 0.075 235x2 1.0 1 0.9931x 1 0.172 135x2 1 0.757 825x3 (1) where x = J/kT.The susceptibility of the salt is found by adding the susceptibility given by equation (1) to that for an isolated ion of spin ��� . It can be seen from Fig. 12 that a satisfactory fit to the data can be obtained using a value of J of 239 cm21. Fig. 12 Magnetic susceptibility vs. temperature for complex 5. Details as in Fig. 10 It is notable that the diVerent polymeric array of complex 5 gives antiferromagnetism of the same order as that of the dimer-based antiferromagnets 3 and 6.However, the values of J obtained are not really comparable, as they are obtained from diVerent equations and probably arise from diVerent combinations of orbital overlaps. The remote Pt ? ? ? Pt separations in 5 imply interaction through overlaps with cations, but the much shorter contacts in 3 and 6 suggest that some direct overlap of magnetic orbitals on Pt is possible for these salts.Any superexchange pathways will be diVerent in all three compounds. Experimental The preparation, purification and reactions of the complexes described were carried out under an atmosphere of dry nitrogen using dried, distilled and deoxygenated solvents. Unless stated otherwise, the complex salts are air-stable in the solid state and are insoluble in all common organic solvents. The complexes [Pt(CNMe)4][PF6]2,19 [ NEt4]2[Pt(mnt)2],20 [ NEt4][Pt- (mnt)2],21 [NBun 4]2[Pd(mnt)2] 20 and [NBun 4][Pd(mnt)2] 21 were prepared by published methods.Microanalyses were carried out by the staV of the Microanalytical Service of the School of Chemistry, University of Bristol. Preparations [Pt(CNMe)4][Pt(mnt)2] 1. (a) Powder. The complex [NEt4]2- [Pt(mnt)2] (0.111 g, 0.151 mmol) in MeCN (10 cm3) was added to a stirred solution of [Pt(CNMe)4][PF6]2 (0.101 g, 0.156 mmol) in MeCN (10 cm3). After 40 min the red solid was removed by filtration, washed with diethyl ether and dried in air, yield 0.09 g (71%). (b) Crystals.To a solution of [Pt(CNMe)4][PF6]2 (25 mg, 0.039 mmol) in MeCN (10 cm3) in a 2 cm diameter Schlenk tube was carefully added [NEt4]2[Pd(mnt)2] (28 mg, 0.040 mmol) in MeCN (10 cm3) to form two layers. After the two layers had diVused together for 2 d the dark red crystals were collected, washed with acetonitrile (10 cm3) and diethyl ether (10 cm3) and then dried in air, yield 20 mg (61%). The salt [Pt(CNMe)4][Pd(mnt)2] 2 was prepared similarly, as yellow-green needles, from [Pt(CNMe)4][PF6]2 and [NBun 4]2- [Pd(mnt)2].[Pt(CNMe)4][Pt(mnt)2]2?2MeCN 3. To a solution of [Pt- (CNMe)4][PF6]2 (0.160 g, 0.246 mmol) in MeCN (25 cm3) in a 5 cm diameter Schlenk tube was carefully added [NEt4][Pt- (mnt)2] (0.298 g, 0.492 mmol) in MeCN (25 cm3) to form two layers. After diVusion for 1 month, the product was obtained as black diamond-shaped crystals which were washed with MeCN and then diethyl ether and dried in air, yield 0.270 g (79%).The salt [Pt(CNMe)4][Pd(mnt)2]2?2MeCN 4 was prepared similarly. The complex [Pt(CNMe)4][Pt(mnt)2]2?MeNO2 5 was obtained by the same method, in MeNO2, as large black needles after 2 d in 67% yield (after washing the crystals with MeNO2 and diethyl ether); [Pt(CNMe)4][Pt(mnt)2]2 6 was obtained by the same method, in PrnNO2, as black cubes after 2 d in 25% yield (after washing the crystals with PrnNO2 and diethyl ether). Magnetic studies Magnetic susceptibilities were determined by the Faraday technique using apparatus and methods described earlier.22 Owing to the large diamagnetic corrections and low susceptibilities of the compounds the experimental error in susceptibility is rather higher than normal, being ±4% for 3, ±3% for 5 and ±7% for 6.Crystallography Crystal data and other details of the structure analyses are presented in Table 3. For complex 4 diVerence electron density2838 J. Chem. Soc., Dalton Trans., 1998, Pages 2833–2838 Table 3 Crystal and refinement data for complexes 1–6 Salt Empirical formula MT /K Crystal system Space group (no.) a/Å b/Å c/Å a/8 b/8 g/8 U/Å3 Z m/mm21 Reflections collected Independent reflections Rint Final R1 [I > 2s(I)], wR2 1 C16H12N8Pt2S4 834.76 298(5) Monoclinic C2/m (12) 20.000(7) 6.655(3) 9.182(4) 94.13(3) 1219.0(9) 2 11.83 2656 1760 0.0633 0.0499, 0.0959 2 C16H12N8PdPtS4 746.06 298(5) Monoclinic C2/m (12) 19.933(4) 6.614(1) 9.152(3) 94.09(2) 1203.5(5) 2 6.92 2191 1475 0.0246 0.0329, 0.0813 3 C28H18N14Pt3S8 1392.30 298(5) Monoclinic P21/n (14) 14.071(4) 14.414(4) 20.747(6) 91.16(2) 4208.0(21) 4 10.39 11 430 8707 0.0528 0.0546, 0.1044 4 C24H18N14Pd2PtS8 1214.93 298(5) Monoclinic P21/n (14) 14.063(6) 14.385(6) 20.668(9) 91.28(3) 4180.0(31) 4 4.63 7349 5409 0.0310 0.0465, 0.0990 5 C25H15N13O2Pt3S8 1371.23 173(2) Monoclinic P21/c (14) 15.913(3) 16.807(3) 14.799(3) 96.417(3) 3933.1(9) 4 11.11 14 791 5600 0.0779 0.0677, 0.1542 6 C24H12N12Pt3S8 1310.19 173(2) Triclinic P1� (2) 11.069(2) 12.463(3) 13.514(3) 100.323(10) 91.272(12) 96.547(11) 1820.5(7) 2 11.99 7818 5103 0.0585 0.0493, 0.1247 close to the weakly dimerised [Pd(mnt)2]2 anions in the columnar stacks making four short contacts of ca. 2.3 Å could be modelled as an oxygen atom, or more satisfactorily, as a low occupancy disordered [0.103(3)] orientation of the Pd(2) atom in the dimer. The second orientation, in which the dimer is rotated by 908 about its longest axis, apparently occupies a very similar volume and shape as the first.Acetonitrile hydrogens were refined in idealised geometries (C]H 0.96 Å, H]C]H 109.58, free rotation about the C]Me bond). CCDC reference number 186/1060. See http://www.rsc.org/suppdata/dt/1998/2833/ for crystallographic files in .cif format. Acknowledgements We thank the EPSRC for research studentships (to J. G. C. and G. R. L.). References 1 See, for example, Inorganic Materials, eds.D. W. Bruce and D. O’Hare, Wiley, New York, 1992; Extended Linear Chain Compounds, ed. J. S. Miller, Plenum, New York, 1992; J. S. Miller and A. J. Epstein, Prog. Inorg. Chem., 1976, 20, 1. 2 J. M. Williams, Adv. Inorg. Chem. Radiochem., 1983, 26, 235; K. Krogmann, Angew. Chem., Int. Ed. Engl., 1969, 8, 35. 3 (a) J. A. McCleverty, Prog. Inorg. Chem., 1968, 10, 49; (b) R. P. Burns and C. A. McAuliVe, Adv. Inorg. Chem. Radiochem., 1979, 22, 303. 4 (a) A. T. Coomber, D. Beljonne, R.H. Friend, J. L. Bredas, A. Charlton, N. Robertson, A. E. Underhill, M. Kurmoo and P. Day, Nature (London), 1996, 380, 144; (b) P. I. Clemenson, Coord. Chem. Rev., 1990, 106, 171; (c) M. B. Hursthouse, R. L. Short, P. I. Clemenson and A. E. Underhill, J. Chem. Soc., Dalton Trans., 1989, 67; (d ) M. B. Hursthouse, R. L. Short, P. I. Clemenson and A. E. Underhill, J. Chem. Soc., Dalton Trans., 1989, 1101. 5 L. Alcacar and A. H. Maki, J. Phys. Chem., 1974, 78, 215; 1976, 80, 1912; A.Domingos, R. T. Henriques, V. Gama, M. Almeida, A. Lopes Vieira and L. Alcacer, Synth. Metals, 1988, 27, B, V. Gama, G. Bonfait, I. C. Santos, M. J. Matos, M. Almeida, M. T. Duarte and L. Alcacer, Synth. Metals, 1993, 56, 1846; V. Gama, R. T. Henriques, G. Bonfait, L. C. Pereira, J. C. Waerenborgh, I. C. Santos, M. T. Duarte, J. M. P. Cabral and M. Almeida, Inorg. Chem., 1992, 31, 2598; V. Gama, R. T. Henriques, G. Bonfait, M. Almeida, A. Meetsma, S. van Smaalen and J. L. de Boer, J. Am. Chem. Soc., 1992, 114, 1986. 6 W. Reith, K. Polborn and E. Amberger, Angew. Chem., Int. Ed. Engl., 1988, 27, 699. 7 Z. J. Zhong, H. Okawa, R. Aoki and S. Kida, Inorg. Chim. Acta, 1988, 144, 233. 8 J. S. Miller, J. C. Calabrese and A. J. Epstein, Inorg. Chem., 1989, 28, 4230. 9 E. Polo, M. Scoponi, S. Sostero, J. Szklarewics and O. Traverso, Gazz. Chim. Ital., 1994, 124, 503. 10 J. Qin, Y. Ding, W. Zhou and D. Liu, Huaxue Xuebao, 1993, 51, 202 (Chem. Abstr., 1993, 119, 95 750). 11 M. Hobi, S. Zurcher, V. Gramlich, U. Burckhardt, C. Mensing, M. Spahr and A. Togni, Organometallics, 1996, 15, 5342. 12 J. G. Qin, W. H. Zhou, C. L. Yang, D. Y. Liu, N. H. Hu and Z. S. Jin, Synth. Metals, 1995, 70, 1217. 13 N. G. Connelly, J. G. Crossley, A. G. Orpen and H. Salter, J. Chem. Soc., Chem. Commun., 1992, 1564. 14 J. G. Crossley and A. G. Orpen, Acta Crystallogr., Sect. C, 1995, 51, 1102. 15 P. I. Clemenson, A. E. Underhill, M. B. Hursthouse and R. L. Short, J. Chem. Soc., Dalton Trans., 1989, 61. 16 W. Guntner, G. Gliemann, U. Klement and M. Zabel, Inorg. Chim. Acta, 1989, 165, 51. 17 B. Bleaney and K. D. Bowers, Proc. R. Soc. London, Ser. A, 1952, 214, 451. 18 J. C. Bonner and M. E. Fisher, Phys. Rev. A, 1964, 135, 640. 19 J. S. Miller and A. L. Balch, Inorg. Chem., 1972, 11, 2069. 20 A. Davison, N. Edelstein, R. H. Holm and A. H. Maki, Inorg. Chem., 1963, 2, 1227. 21 J. F. Weiher, L. R. Melby and R. E. Benson, J. Am. Chem. Soc., 1964, 86, 4329. 22 M. A. LaVey and P. Thornton, J. Chem. Soc., Dalton Trans., 1982, 313. Received 8th May 1998; Paper 8/03456G

ISSN:1477-9226    

DOI:10.1039/a803456g

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, Pages 2839–2847 2839 Selenium and tellurium derivatives of a monocarbon platinacarbaborane complex† Stewart A. Batten,a John C. JeVery,a Leigh H. Rees,a Martin D. Rudd b and F. Gordon A. Stone *,b a School of Chemistry, The University, Bristol, UK BS8 1TS b Department of Chemistry, Baylor University, Waco, TX 76798-7348, USA The reaction between Na[Pt(PEt3)2(h5-7-CB10H11)] 1 and PhSeCl in thf (tetrahydrofuran) aVorded a mixture containing the isomeric species [Pt(SePh)(PEt3)(h5-n-SePh-7-CB10H10)] (n = 8 2a or 9 2b) and the compound [Pt(SePh)(PEt3){h5-8-O(CH2)4Cl-7-CB10H10}] 3.The molecular structures of complexes 2a and 3 were established by X-ray crystallography. Both molecules have Pt(SePh)(PEt3) groups with the platinum atoms pentahapto co-ordinated by nido-7-CB10 cage frameworks. In 2a the cage substituted SePh group is attached to the boron atom in the a site with respect to the carbon in the CBBBB ring ligating the platinum and this is true also of the O(CH2)4Cl substituent in 3.The isomers 2 are also formed when PhSeSePh is used instead of PhSeCl. Treatment of the salt 1 with PhTeI in thf yielded a mixture of [Pt(PEt3)2{h5-9-Te(Ph)CH2Cl-7-CB10H10}] 4 and [Pt2(TePh)(m-TePh)2(PEt3)2(h5-2-CB10H11)] 5. Single-crystal X-ray diVraction studies were employed to establish the formulations and molecular structures of both molecules. Compound 4 is a charge-compensated platinacarbaborane with a Pt(PEt3)2 group and with the nido-7-CB10 framework carrying a Te(Ph)CH2Cl moiety at the boron vertex situated in the b site with respect to the carbon in the CBBBB ring ligating the platinum.Complex 5 is a diplatinum species in which Pt(TePh)(PEt3) and Pt(PEt3)(h5-2-CB10H11) units are bridged by two TePh groups. The X-ray study revealed that in forming compound 5 from the reagent 1 the nido-7-CB10H11 cage system has undergone an unusual polytopal rearrangement to a nido-2-CB10H11 framework.As part of studies 1 directed towards extending the range of monocarbon metallacarbaboranes with icosahedral frameworks, the salt Na[Pt(PEt3)2(h5-7-CB10H11)] 1 has been prepared and used to obtain a variety of new products, including the heterodinuclear metal compounds [PtM(PEt3)2L(h5-7-CB10- H11)] (M = Cu or Au, L = PPh3; M = Hg, L = Ph).1a The latter were prepared by treating the reagent 1 with the chloro complexes [MCl(PPh3)] (M = Cu or Au) and [HgCl(Ph)], respectively.Formation of these dimetal species suggested that a similar reaction between the platinum species 1 and the compounds PhSeCl or PhTeI should yield as products the complexes [Pt(EPh)(PEt3)2(h5-7-CB10H11)] (E = Se or Te). These compounds would be of interest since as far as we are aware platinacarbaborane cage complexes in which the platinum vertex is exopolyhedrally bonded to selenium or tellurium are not known. Moreover, the desired products might be potentially useful as reagents for further syntheses by virtue of the donor properties of lone pairs associated with the Se or Te atoms.However, instead of obtaining the anticipated complexes [Pt(EPh)(PEt3)2(h5-7-CB10H11)] (E = Se or Te), mixtures of products were isolated as a consequence of reactions occurring at BH groups of the CBBBB face of the nido-7-CB10H11 cage ligating the platinum. Results and discussion Addition of the reagent 1 in thf (tetrahydrofuran) to a solution of PhSeCl in the same solvent aVorded at ambient temperatures a mixture of products which were separated by column chromatography. Two isomeric species [Pt(SePh)(PEt3)(h5-n-SePh-7- † The complexes described in this paper have a platinum atom incorporated into a closo-1-carba-2-platinadodecaborane structure.However, to avoid a complicated nomenclature for the compounds reported, and to relate them to species with pentahapto-co-ordinated cyclopentadienyl ligands, following precedent (see ref. 1) we treat the cages as nido-11-vertex ligands with numbering as for an icosahedron from which the twelfth vertex has been removed. CB10H10)] (n = 8 2a or 9 2b) were obtained, but also formed were the compounds [Pt(SePh)(PEt3){h5-8-O(CH2)4Cl-7-CB10H10}] 3 and [Pt(SePh)2(PEt3)2]. These complexes were characterised by microanalysis and NMR spectroscopy (Table 1), and for 2a and 3 also by single-crystal X-ray diVraction studies. A mixture of the isomers 2 was also isolated when PhSeSePh was used instead of PhSeCl.The molecule 2a is shown in Fig. 1 and selected bond distances and angles are listed in Table 2. It is immediately apparent that there are two SePh groups one of which is attached to the platinum atom and the other exopolyhedrally to a boron atom of the nido-7-CB10H10 fragment. Moreover, B(2), the atom of the carbaborane group to which the SePh group is attached, is located in an a site with respect to the carbon in the CBBBB ring ligating the platinum.The Se(2)]B(2) distance [1.984(9) Å] in 2a is somewhat shorter than those [2.016(15) and 2.023(16) Å] in the salt [NEt4]2[Se3B11H9], a disubstituted derivative of [closo-B11H11]22 in which an Se3 chain bridges two boron atoms.2 The Pt]Se(1) separation [2.4438(8) Å] lies within the range [2.376(2)–2.590(7) Å] observed in various complexes containing Pt]Se bonds.3 Interestingly, however, the Pt]Se(1) connectivity is shorter than those [2.676(1) Å] in the complexes [Pt(PR3)2(h5- 7-SeB10H10)] (R = Et or Ph) where the selenium atom is a vertex in a closo-cage system.4 Of interest is whether the Se(1)Ph group of 2a formally contributes one electron to the valence shell of2840 J.Chem. Soc., Dalton Trans., 1998, Pages 2839–2847 Table 1 Hydrogen-1, carbon-13, boron-11 and phosphorus-31 NMR data a Compound 2a 1H (d) 1.25 [d of t, 9 H, Me, J(PH) 16, J(HH) 8], 2.23 [d of q, 6 H, CH2, J(PH) 15, J(HH) 8], 3.50 (s br, 1 H, cage CH), 6.60–7.57 (m, 10 H, Ph) 13C (d) b 137.2–128.3 (m, Ph), 49.0 (br, cage CH), 18.5 [d, PCH2Me, J(PC) 15], 8.3 [d, PCH2Me, J(PC) 8] 11B (d) c 21.7 (1 B, BSe), 19.3 (1 B), 8.0 (1 B), 4.7 (1 B), 3.0 (1 B), 25.2 (1 B), 28.8 (1 B), 210.3 (1 B), 214.1 (1 B), 215.2 (1 B) 31P (d) d 27.8 [J(PtP) 3283] 2b e 1.26 [d of t, 9 H, Me, J(PH) 16, J(HH) 8], 2.25 [d of q, 6 H, CH2, J(PH) 15, J(HH) 8], 3.53 (s br, 1 H, cage CH), 6.60–7.57 (m, 10 H, Ph) 23.5 (1 B, BSe), 20.1 (1 B), 7.1 (1 B), 3.2 (1 B), 21.0 (1 B), 25.3 (1 B), 28.3 (1 B), 210.5 (1 B), 217.4 (2 B) 26.5 [J(PtP) 3469] 3 1.24 [d of t, 9 H, Me, J(PH) 16, J(HH) 8], 1.74–1.91 (m, 4 H, OCH2 and CH2Cl), 2.50 [d of t, 6 H, PCH2Me, J(PH) 16, J(HH) 8], 3.40–3.72 (m, 4 H, CH2CH2CH2CH2), 7.21–7.50 (m, 5 H, Ph) 137.0–128.5 (m, Ph), 69.6 (s, OCH2), 65.3 (br, cage CH), 45.2 (CH2Cl), 29.6 (CH2), 28.6 (CH2), 17.4 [d, PCH2Me, J(PC) 37], 7.8 [d, PCH2Me, J(PC) 8] 22.2 (1 B, BOCH2), 19.2 (1 B), 13.3 (1 B), 6.7 (2 B), 28.5 (2 B), 210.5 (1 B), 211.9 (1 B), 220.8 (1 B) 35.4 [J(PtP) 3147] 4 0.70 [d of t, 9 H, Me, J(PH) 14, J(HH) 8], 1.08 [d of t, 9 H, Me, J(PH) 15, J(HH) 7], 1.86 [d of q, 6 H, CH2, J(PH) 15, J(HH) 8], 2.09 (m, 6 H, CH2), 2.57 (s, 1 H, cage CH), 4.46, 4.52 [AB, 2 H, CH2Cl, J(AB) 5], 7.43–7.84 (m, 5 H, Ph) 136.6–130.3 (m, Ph), 50.2 (br, cage CH), 32.8 (CH2Cl), 18.8 (m, PCH2Me), 8.5 (m, PCH2- Me) 24.7 (1 B, BTe), 29.6 (2 B), 220.2 (5 B), 225.1 (2 B) 20.23 [J(PtP) 3513], 0.85 [J(PtP) 3190] 5 0.96 (m, 18 H, Me), 1.54–2.24 (m, 12 H, CH2), 2.66 (s br, 1 H, cage CH), 6.77–7.90 (m, 15 H, Ph) 142.4–127.6 (m, Ph), 45.5 (br, cage CH), 18.1 (m, PCH2Me), 9.5 (m, PCH2Me) 2.0 (3 B), 23.5 (3 B), 213.9 (4 B) 1.23 [J(PtP) 2997], 2.11 [J(PtP) 2988] a Chemical shifts in ppm, coupling constants in Hz, measurements in CD2Cl2 at room temperature.b Hydrogen-1 decoupled, chemical shifts are positive to high frequency of SiMe4. c Hydrogen-1 decoupled, chemical shifts are positive to high frequency of BF3?Et2O (external).Assignments for BX (X = Se, Te or OCH2) groups made from the observation of resonance as a singlet peak in a fully coupled 11B spectrum. d Hydrogen-1 decoupled, chemical shifts are positive to high frequency of 85% H3PO4 (external). e The 13C-{1H} spectrum was too weak to give meaningful data. platinum or three if a lone pair on the selenium p bonds to the metal center. The angles Pt]Se(1)]C(21) [106.2(2)8] and B(2)]Se(2)]C(11) [105.4(3)8] are very similar, and of a magnitude suggesting that the selenium atoms in the two sites are both sp3 hybridised.It is thus reasonable to suppose that Pt]Se(1) is a s bond involving an electron pair, and hence with the PEt3 and h5-8-SePh-7-CB10H10 ligands contributing two and three electrons, respectively, overall the platinum atom has 16 electrons in its valence shell. The Pt]P distance [2.330(2) Å] is similar to that in [PtAu(PEt3)2(PPh3)(h5-7-CB10H11)] [2.3487(14) Å].1a The average found for the many complexes with Pt]PEt3 bonds studied by X-ray diVraction is 2.296 Å, though these separations vary slightly with the co-ordination number of the platinum.5 The NMR data (Table 1) for complex 2a are in accord with the structure established by X-ray diVraction. The 1H NMR spectrum reveals a diagnostic broad peak for the cage CH group at d 3.50 while a characteristic resonance for this group is also seen in the 13C-{1H} spectrum at d 49.0.1 In the 11B-{1H} NMR spectrum there are ten signals in accord with the asymmetry of the nido-8-SePh-7-CB10H10 fragment.The resonance in this spectrum at d 21.7 may be ascribed to the BSePh nucleus as it remained a singlet in a fully coupled 11B spectrum, whereas the other peaks became doublets [J(BH) > 100 Hz]. The 31P- {1H} NMR spectrum was as expected, a singlet (d 27.8) with 195Pt satellite peaks. The microanalytical data for complex 2b established that it Fig. 1 Molecular structure of [Pt(SePh)(PEt3)(h5-8-SePh-7-CB10H10)] 2a showing the atom labelling scheme. Ellipsoids are drawn at the 40% probability level and hydrogen atoms are omitted for clarityJ. Chem. Soc., Dalton Trans., 1998, Pages 2839–2847 2841 Table 2 Selected internuclear distances (Å) and angles (8) for [Pt(SePh)(PEt3)(h5-8-SePh-7-CB10H10)] 2a with estimated standard deviations (e.s.d.s) in parentheses Pt]B(2) Pt]B(3) Se(2)]C(11) B(2)]B(3) C(12)]C(13) C(21)]C(22) C(24)]C(25) B(2)]Pt]B(5) B(2)]Pt]B(4) B(2)]Pt]B(3) B(4)]Pt]B(3) C(1)]Pt]P B(2)]Pt]Se(1) B(4)]Pt]Se(1) C(21)]Se(1)]Pt B(8)]B(2)]Se(2) Se(2)]B(2)]Pt C(22)]C(21)]Se(1) 2.178(8) 2.278(8) 1.936(8) 1.876(11) 1.345(11) 1.373(11) 1.376(11) 82.2(3) 82.4(3) 49.7(3) 47.0(3) 177.6(2) 123.7(2) 142.0(2) 106.2(2) 121.3(6) 100.3(4) 120.2(6) Pt]B(5) Pt]P Se(2)]B(2) B(3)]B(4) C(13)]C(14) C(21)]C(26) C(25)]C(26) B(2)]Pt]C(1) B(5)]Pt]B(4) B(5)]Pt]B(3) B(2)]Pt]P B(4)]Pt]P B(5)]Pt]Se(1) B(3)]Pt]Se(1) C(11)]Se(2)]B(2) B(7)]B(2)]Se(2) C(16)]C(11)]Se(2) C(26)]C(21)]Se(1) 2.195(9) 2.330(2) 1.984(9) 1.797(12) 1.411(13) 1.398(10) 1.381(11) 46.2(3) 50.8(3) 84.3(3) 132.8(2) 95.8(3) 101.5(2) 170.9(2) 105.4(3) 129.6(5) 118.1(7) 119.5(6) Pt]C(1) Pt]Se(1) C(1)]B(2) C(11)]C(16) C(14)]C(15) C(22)]C(23) B(5)]Pt]C(1) C(1)]Pt]B(4) C(1)]Pt]B(3) B(5)]Pt]P B(3)]Pt]P C(1)]Pt]Se(1) P]Pt]Se(1) C(1)]B(2)]Se(2) B(3)]B(2)]Se(2) C(12)]C(11)]Se(2) 2.230(7) 2.4438(8) 1.732(11) 1.385(12) 1.347(12) 1.368(11) 47.0(3) 81.9(3) 82.0(3) 131.7(2) 95.8(2) 96.8(2) 85.49(6) 127.8(5) 111.7(5) 121.6(7) Pt]B(4) Se(1)]C(21) C(1)]B(5) C(11)]C(12) C(15)]C(16) C(23)]C(24) 2.231(9) 1.934(8) 1.766(11) 1.428(11) 1.403(12) 1.406(11) Fig. 2 Extended Hückel MO calculations for complex 2a: (i) LUMO, (ii) Frontier energy levels, (iii) HOMO. Key: boron, yellow; carbon, grey; selenium, red; phosphorus, pink; platinum, silver x y z (i) (iii) Pt contributions E/eV –8.34 –9.18 –10.28 (LUMO) (HOMO) –10.47 86 85 84 83 d xy d z2 (ii) had the same elemental composition as 2a.Moreover, the 1H, 31P-{1H}, and 11B-{1H} NMR data for the two species are very similar (Table 1). On the basis of earlier studies 1 we identify 2b as [Pt(SePh)(PEt3)(h5-9-SePh-7-CB10H10)] the isomer in which the SePh cage substituent is attached to a boron atom in the b site in the CBBBB ring co-ordinated to the platinum atom. The presence of stable 16e2 platinum(IV) centers in the complexes 2 is somewhat unusual and prompted us to examine the frontier orbitals of 2a.Using the atomic coordinates generated by the crystal structure determination, an extended Hückel MO calculation 6 was carried out. The LUMO [Fig. 2(i)] is a p-symmetry orbital which primarily consists of a platinum dxy atomic orbital in antibonding combination with carbaborane cage atomic orbitals in the CBBBB co-ordinating face. It lies some 1.1 eV (1 eV ª 1.60 × 10219 J) higher in energy [Fig. 2(ii)] above the HOMO [Fig. 2(iii)], which comprises a significant contribution from the platinum dz2 orbital, the latter being in bonding combination with cage atomic orbitals.Thus 2a does not seem particularly electronically susceptible to attack by the lone pair of, say, a second PEt3 ligand. This was indeed observed to be the case as attempts to add 1 equivalent of PEt3 to the complexes 2 did not succeed. Treatment of 2a with the rod-like ligand CNBut also failed to aVord an 18-electron complex [Pt(SePh)(CNBut)(PEt3)(h5-8-SePh-7-CB10H10)]. Furthermore, examination of the space-filling diagram of 2a (Fig. 3) reveals that approach of an extra co-ordinating ligand would be severely sterically hindered; there is little room to accommodate further groups around the platinum, even when the cage-bound SePh has its phenyl group oriented away from the metal center.2842 J. Chem. Soc., Dalton Trans., 1998, Pages 2839–2847 As mentioned above, there was no evidence from the X-ray diVraction study that selenium lone pairs elevated the electron count at the platinum, and this is supported by the absence of any contribution of these lone pair atomic orbitals to the frontier HOMO region.The question arises as to why the complexes 2 do not increase their co-ordination number, while the complexes [PtM(PEt3)2L(h5-7-CB10H11)] (M = Cu or Au, L = PPh3; M = Hg, L = Ph) 1a do achieve the expected 18e2 count by co-ordination of two PEt3 ligands rather than one. The problem would primarily appear to be one of a steric nature, for it is qualitatively intuitive that the Tolman cone angle,7 qT, of the bent SePh group far exceeds that of the linear ML units in the complexes [PtM(PEt3)2L(h5-7-CB10H11)] (M = Cu or Au, L = PPh3; M = Hg, L = Ph).A complicated series of reaction steps is evidently responsible for replacement of the H atom of a BH moiety in the reagent 1 by an SePh group in order to aVord the isomers 2. The pathway Fig. 3 Space-filling diagram of the molecule 2a showing a lack of accessibility to the platinum.Colour key: as for Fig. 2 by which this occurs is obscure at the present time and any proposal is necessarily speculative. One possibility for the formation of 2a (Scheme 1) is that the compound [Pt(SePh)- (PEt3)(h5-7-CB10H11)] A is initially formed by nucleophilic attack of [Pt(PEt3)2(h5-7-CB10H11)]2 on PhSeCl or PhSeSePh with concomitant dissociation of phosphine. The loss of phosphine at this stage would be expected on the basis of the above discussion.The species A could in turn aVord the zwitterionic molecule [Pt(PEt3)2{h5-8-Se(H)Ph-7-CB10H10}] B by migratory insertion of SePh into the Ba]H bond of the nearby CBBBB ring accompanied by reco-ordination of the phosphine to give an 18e2 platinum center. Insertion of metal bonded alkylidene groups into adjacent B]H bonds in icosahedral metallacarbaboranes is well documented.8 Deprotonation of the boron-bound Se(H)Ph group in B by traces of dissociated phosphine or X2 (X = Cl2 or SePh2) would give the anionic reagent [Pt(PEt3)2(h5-8-SePh-7-CB10H10)]2 C, which could react further with PhSeX to give the complex 2a.This mechanism would also account for the formation of 2b by a route with intermediates similar to B and C, but with the selenium fragment bound to a b-boron atom in the CBBBB face of the cage. In the reaction between the salt 1 and PhSeCl, compound 3 was the product formed in highest yield (ca. 35%, compared with a combined yield of ca. 20–25% for the isomers 2 based on the platinum used). The nature of complex 3 only became evident after an X-ray diVraction study had been undertaken. The molecule is shown in Fig. 4 and selected internuclear distances and angles are given in Table 3. The platinum atom carries PEt3 and SePh ligands as it does in complex 2a. As might be expected the Pt]P [2.329(2) Å] and Pt]Se [2.4125(6) Å] bond lengths in complex 3 are very similar to those in compound 2a.The carbaborane ligand in complex 3, however, is a nido-7-CB10H10 cage fragment having an O(CH2)4Cl substituent attached to a boron atom in an a site in the CBBBB ring co-ordinated to the platinum. Thus complex 3 is established as having the formulation [Pt(SePh)(PEt3){h5-8-O(CH2)4Cl-7-CB10H10}]. We found no evidence for formation of an isomer [Pt(SePh)- Scheme 1 Suggested pathways for the formation of complexes 2a and 3J. Chem. Soc., Dalton Trans., 1998, Pages 2839–2847 2843 Table 3 Selected internuclear distances (Å) and angles (8) for [Pt(SePh)(PEt3){h5-8-O(CH2)4Cl-7-CB10H10}] 3 with e.s.d.s in parentheses Pt]B(5) Pt]C(1) B(2)]O(51) B(2)]B(3) Cl]C(55) B(5)]B(10) B(4)]B(10) B(8)]B(9) B(7)]B(11) B(10)]B(9) B(5)]Pt]B(2) B(5)]Pt]B(4) B(5)]Pt]C(1) B(4)]Pt]C(1) B(3)]Pt]P B(5)]Pt]Se B(4)]Pt]Se C(41)]Se]Pt 2.185(6) 2.243(5) 1.369(7) 1.903(9) 1.800(7) 1.758(8) 1.776(9) 1.778(9) 1.751(9) 1.784(9) 82.4(2) 50.5(2) 46.4(2) 81.7(2) 96.8(2) 114.3(2) 157.4(2) 107.9(2) Pt]B(2) Pt]P B(2)]C(1) P]C(31) C(1)]B(6) B(5)]B(6) B(4)]B(3) B(8)]B(11) B(6)]B(11) B(9)]B(11) B(5)]Pt]B(3) B(2)]Pt]B(4) B(2)]Pt]C(1) B(5)]Pt]P B(4)]Pt]P B(2)]Pt]Se C(1)]Pt]Se O(51)]B(2)]C(1) 2.215(6) 2.329(2) 1.754(8) 1.814(5) 1.688(8) 1.783(8) 1.778(9) 1.784(9) 1.774(9) 1.763(9) 83.5(2) 83.9(2) 46.3(2) 127.9(2) 93.0(2) 112.7(2) 98.50(13) 120.6(4) Pt]B(3) Pt]Se B(2)]B(8) P]C(11) C(1)]B(7) B(5)]B(4) B(3)]B(9) B(8)]B(7) B(6)]B(10) B(2)]Pt]B(3) B(3)]Pt]B(4) B(3)]Pt]C(1) B(2)]Pt]P C(1)]Pt]P B(3)]Pt]Se P]Pt]Se O(51)]B(2)]B(8) 2.230(6) 2.4125(6) 1.777(8) 1.819(6) 1.694(8) 1.886(9) 1.769(9) 1.795(9) 1.782(9) 50.7(2) 47.0(2) 81.5(2) 136.0(2) 174.06(13) 155.6(2) 85.39(4) 126.4(5) Pt]B(4) Se]C(41) B(2)]B(7) P]C(21) C(1)]B(5) B(4)]B(9) B(3)]B(8) B(7)]B(6) B(10)]B(11) 2.231(6) 1.924(5) 1.810(9) 1.834(6) 1.745(8) 1.768(8) 1.781(9) 1.734(9) 1.783(9) (PEt3){h5-9-O(CH2)4Cl-7-CB10H10}] with the O(CH2)4Cl group attached to a b-boron in the CBBBB ring.It is noteworthy that isomer 2a was isolated in about twice the amount of 2b seemingly indicating a preference for substitution at a sites in the CBBBB rings and it is possible that small amounts of [Pt(SePh)(PEt3){h5-9-O(CH2)4Cl-7-CB10H10}] were formed but lost in the work up procedures. However, we are currently assessing the preference for reactions at the BHa or BHb sites and there are insuYcient data available at the present time to draw any firm conclusions.The O(CH2)4Cl group in compound 3 is reminiscent of the O(CH2)4F substituent attached to the cage in the molybdenum complex [NBun 4][Mo(CO)2(h3-C3H5){h5-7,8-Me2-10-O(CH2)4- F-7,8-C2B9H8}]. The O(CH2)4F group in this molybdenum complex is formed by nucleophilic attack of F2 ion on the three-co-ordinate oxygen atom of a thf molecule in the ylid complex [Mo(CO)2(h3-C3H5){h5-7,8-Me2-10-O(CH2)4-7,8-C2- B9H8}].9a Similar ring opening of cyclic ethers attached to boron cage systems by nucleophiles has been reported for other systems.9b,10 It thus seems certain that the O(CH2)4Cl group in 3 results from Cl2 attack on a thf molecule co-ordinated to a cage boron atom.Chloride anion would be formed in the reaction of the salt 1 with PhSeCl and since thf is the solvent the necessary components for producing the O(CH2)4Cl fragment are present. Not unexpectedly 3 was not observed in the reaction between the reagent 1 and PhSeSePh since there is no source of Cl2 under these conditions.The pathway proposed above for the formation of the isomers 2 can be modified to accommodate the synthesis of complex 3 (Scheme 1). The boron-co-ordinated PhSeH molecule in Fig. 4 Molecular structure of [Pt(SePh)(PEt3){h5-8-O(CH2)4Cl-7- CB10H10}] 3. Details as in Fig. 1 the suggested zwitterionic intermediate B might readily be displaced by a thf molecule to give [Pt(PEt3)2{h5-8-O(CH2)4-7- CB10H10}] D in a process thermodynamically favoured on account of the strength of B]O bonds. A species D once formed would be expected 9 to react readily with Cl2 to give [Pt(PEt3)2- {h5-8-O(CH2)4Cl-7-CB10H10}]2 E, and subsequently with PhSe- Cl to yield compound 3.The NMR data (Table 1) for complex 3 are in accord with the results of the X-ray diVraction study. In particular the 11B-{1H} NMR spectrum has a peak at d 22.2 which may be ascribed to the BOCH2 nucleus. It remained a singlet in a fully coupled 11B spectrum and moreover the chemical shift may be compared with that observed (d 20.1) for the BOCH2 nucleus in [NBun 4]- [Mo(CO)2(h3-C3H5){h5-7,8-Me2-10-O(CH2)4F-7,8-C2B9H8}].9a Other peaks in the NMR spectra of compound 3 are readily assigned.The pathway by which [Pt(SePh)2(PEt3)2] is formed in the reactions is very unclear. It may form from [PtCl2(PEt3)2] and NaSePh. Some [PtCl2(PEt3)2] might be present as a contaminant in the reagent 1 as it is a precursor of this salt,1 while NaSePh could be generated at some point in the complicated reaction pathways.Following investigation of reactions between the reagent 1 and the selenium compounds the study was continued with tellurium using PhTeI generated in situ by adding iodine to PhTeTePh.11 The salt 1 and PhTeI in thf aVorded two products, one yellow (4) and the other red (5), which were separable by column chromatography. Neither could be fully characterised solely by microanalysis and NMR spectroscopy so an X-ray crystallographic study was carried out on each.Compound 4 proved to be the zwitterionic species [Pt(PEt3)2- {h5-9-Te(Ph)CH2Cl-7-CB10H10}]. Many such charge-compensated metallacarbaboranes are known.9,12 The molecule 4 is shown in Fig. 5 and selected internuclear distances and angles are listed in Table 4. The platinum is ligated on one side by two PEt3 groups. The two Pt]P bond distances average 2.313 Å and are very similar to those found in the molecules 2a and 3, and close to the average (2.288 Å) observed in several other platinum complexes having this ligand when the metal has a co-ordination number of four or five.5 The other side of the platinum atom is pentahapto co-ordinated by a nido- 9-Te(Ph)CH2Cl-7-CB10H10 cage moiety.The Te(Ph)CH2Cl fragment is attached to B(3) [B(3)]Te 2.215(6) Å] in the b site with respect to the carbon atom in the CBBBB ring. However, the formation of the group is inexplicable at the present time, although the CH2Cl fragment must be derived from CH2Cl2.Since this solvent was only introduced during the work up procedures a precursor to compound 4 must have formed initially and then undergone further reaction with CH2Cl2.2844 J. Chem. Soc., Dalton Trans., 1998, Pages 2839–2847 Table 4 Selected internuclear distances (Å) and angles (8) for [Pt(PEt3)2{h5-9-Te(Ph)CH2Cl-7-CB10H10}] 4 with e.s.d.s in parentheses Pt]B(3) Pt]P(1) Te]C(2) C(1)]B(7) B(2)]B(8) B(3)]B(9) B(4)]B(5) B(6)]B(11) B(8)]B(11) B(10)]B(11) B(3)]Pt]B(4) B(3)]Pt]B(2) B(3)]Pt]P(1) B(2)]Pt]P(1) B(5)]Pt]P(2) B(3)]Pt]C(1) B(2)]Pt]C(1) C(31)]Te]C(2) Cl9]C(2)]Te C(13)]P(1)]C(11) C(15)]P(1)]Pt C(23)]P(2)]C(25) C(21)]P(2)]Pt 2.235(6) 2.3074(14) 2.154(7) 1.670(8) 1.814(9) 1.766(8) 1.895(9) 1.766(9) 1.796(9) 1.805(9) 46.9(2) 47.9(2) 137.5(2) 161.9(2) 146.8(2) 73.8(2) 40.1(2) 93.7(3) 118.3(13) 101.6(3) 116.1(2) 101.2(3) 115.0(2) Pt]B(4) Pt]P(2) Te]B(3) C(1)]B(5) B(2)]B(7) B(3)]B(4) B(5)]B(10) B(6)]B(10) B(8)]B(9) B(3)]Pt]B(5) B(4)]Pt]B(2) B(4)]Pt]P(1) B(3)]Pt]P(2) B(2)]Pt]P(2) B(4)]Pt]C(1) P(1)]Pt]C(1) C(31)]Te]B(3) Cl]C(2)]Te C(15)]P(1)]C(11) C(11)]P(1)]Pt C(21)]P(2)]C(25) C(25)]P(2)]Pt 2.244(6) 2.3189(14) 2.215(6) 1.672(8) 1.823(8) 1.782(8) 1.793(9) 1.782(9) 1.799(9) 77.9(2) 79.8(2) 95.6(2) 115.2(2) 93.8(2) 75.7(2) 121.77(12) 104.2(2) 108.7(4) 103.2(3) 114.8(2) 101.4(3) 118.5(2) Pt]B(5) Pt]C(1) C(2)]Cl9 C(1)]B(6) B(2)]B(3) B(4)]B(10) B(5)]B(6) B(7)]B(8) B(9)]B(11) B(4)]Pt]B(5) B(5)]Pt]B(2) B(5)]Pt]P(1) B(4)]Pt]P(2) P(1)]Pt]P(2) B(5)]Pt]C(1) P(2)]Pt]C(1) C(2)]Te]B(3) C(13)]P(1)]C(15) C(13)]P(1)]Pt C(23)]P(2)]C(21) C(23)]P(2)]Pt 2.294(6) 2.565(5) 1.67(2) 1.676(8) 1.839(9) 1.778(9) 1.815(8) 1.784(9) 1.766(9) 49.3(2) 72.1(2) 91.5(2) 159.4(2) 96.17(5) 39.8(2) 111.73(12) 101.9(3) 102.7(3) 116.4(2) 102.9(3) 115.6(2) Pt]B(2) Te]C(31) C(2)]Cl C(1)]B(2) B(3)]B(8) B(4)]B(9) B(6)]B(7) B(7)]B(11) B(9)]B(10) 2.295(6) 2.117(6) 1.777(8) 1.686(8) 1.753(8) 1.796(9) 1.753(8) 1.788(9) 1.785(9) Fig. 5 Molecular structure of [Pt(PEt3)2{h5-9-Te(Ph)CH2Cl-7-CB10- H10}] 4. Details as in Fig. 1 The 31P-{1H} NMR spectrum (Table 1) of complex 4 shows two resonances in accord with the non-equivalence of the PEt3 ligands. Several peaks in the 11B-{1H} NMR spectrum were broad and overlapped, and little could be inferred from this spectrum. However, a signal corresponding in intensity to a single boron atom at d 24.7 is assigned to the BTe nucleus since in a fully coupled 11B spectrum it remained a singlet. A broad peak in the 13C-{1H} NMR spectrum at d 50.2 is diagnostic for the cage-carbon atom.The X-ray diVraction study of the red product 5 established its formulation as the diplatinum complex [Pt2(TePh)(m-TePh)2- (PEt3)2(h5-2-CB10H11)]. The molecule is shown in Fig. 6 and important bond distances and angles are given in Table 5. There are several features of interest in the structure. Two TePh groups bridge the Pt(1) and Pt(2) atoms, with Pt(1) carrying PEt3 and h5-2-CB10H11 ligands, and Pt(2) a TePh and a PEt3 group.In the bridge system the Pt(1)]Te(1) [2.7220(6) Å] and Pt(1)]Te(2) [2.7054(6) Å] bond lengths are perceptibly longer than the Pt(2)]Te(1) [2.6175(6)] and Pt(2)]Te(2) [2.6113(7) Å] Fig. 6 Molecular structure of [Pt2(TePh)(m-TePh)2(PEt3)2(h5-2-CB10- H11)] 5. Details as in Fig. 1J. Chem. Soc., Dalton Trans., 1998, Pages 2839–2847 2845 Table 5 Selected internuclear distances (Å) and angles (8) for [Pt2(TePh)(m-TePh)2(PEt3)2(h5-2-CB10H11)] 5 with e.s.d.s in parentheses Pt(1)]B(5) Pt(1)]B(2) Pt(2)]P(2) B(1)]B(6) B(2)]B(8) B(3)]B(8) B(4)]B(5) B(6)]B(7) B(8)]B(11) C(10)]B(11) B(5)]Pt(1)]Te(2) B(1)]Pt(1)]Te(2) B(5)]Pt(1)]Te(1) B(1)]Pt(1)]Te(1) Te(2)]Pt(1)]Te(1) Te(2)]Pt(2)]Te(1) Te(1)]Pt(2)]Te(3) Pt(2)]Te(1)]Pt(2) Pt(2)]Te(2)]Pt(1) 2.203(8) 2.246(7) 2.284(2) 1.757(10) 1.787(10) 1.803(10) 1.885(10) 1.767(10) 1.769(11) 1.718(10) 105.1(2) 150.9(2) 168.4(2) 129.0(2) 79.24(2) 82.89(2) 94.68(2) 97.22(2) 97.78(2) Pt(1)]B(4) Pt(1)]P(1) Pt(2)]Te(2) B(1)]B(7) B(2)]B(7) B(3)]B(4) B(5)]B(10) B(6)]B(11) B(8)]B(9) Te(1)]C(1) B(4)]Pt(1)]Te(2) B(2)]Pt(1)]Te(2) B(4)]Pt(1)]Te(1) B(2)]Pt(1)]Te(1) P(2)]Pt(2)]Te(2) P(2)]Pt(2)]Te(3) C(11)]Te(1)]Pt(2) C(21)]Te(2)]Pt(2) C(31)]Te(3)]Pt(2) 2.226(7) 2.392(2) 2.6113(7) 1.782(9) 1.790(11) 1.820(11) 1.718(10) 1.796(11) 1.786(11) 2.131(6) 85.5(2) 156.3(2) 120.4(2) 88.1(2) 94.79(4) 87.60(4) 105.4(2) 99.7(2) 103.7(2) Pt(1)]B(3) Pt(1)]Te(2) Pt(2)]Te(1) B(1)]B(2) B(2)]B(3) B(4)]C(10) B(5)]B(6) B(7)]B(8) B(9)]C(10) Te(2)]C(21) B(3)]Pt(1)]B(2) P(1)]Pt(1)]Te(2) B(3)]Pt(1)]Te(1) P(1)]Pt(1)]Te(1) P(2)]Pt(2)]Te(1) Te(2)]Pt(2)]Te(3) C(11)]Te(1)]Pt(1) C(21)]Te(2)]Pt(1) 2.242(7) 2.7054(6) 2.6175(6) 1.840(10) 1.878(10) 1.693(9) 1.758(10) 1.781(11) 1.688(10) 2.119(6) 108.7(2) 88.50(4) 83.6(2) 95.66(4) 176.91(4) 177.20(2) 106.0(2) 107.7(2) Pt(1)]B(1) Pt(1)]Te(1) Pt(2)]Te(3) B(1)]B(5) B(3)]B(9) B(4)]B(9) B(6)]C(10) B(7)]B(11) B(9)]B(11) Te(3)]C(31) 2.242(7) 2.7220(6) 2.6225(7) 1.840(10) 1.774(10) 1.743(10) 1.711(10) 1.785(10) 1.755(10) 2.124(6) bond lengths.This may be the result of the platinum atoms having diVerent formal oxidation states a feature discussed further below in the context of the Pt]P distances. Few platinum– tellurium bond lengths have been recorded but all five bonds in 5 are longer than those found in [Pt2Cl2(m-Cl)(m-TePh)(PBun 3)2] (2.531 Å) 13 and [Pt(1,2-Te2C6H4)(PPh3)2] (2.589 Å).14 The phenyl groups attached to Te(1) and Te(2) lie, respectively, below and above the Pt2Te2 ring (Fig. 6), the atoms of which are slightly buckled about the Te(1) ? ? ?Te(2) vector. The dihedral angle between the Pt(1)Te(1)Te(2) and Pt(2)Te(1)Te(2) planes is 1638. The m-Te(2)Ph moiety lies trans to the Te(3)Ph ligand [Te(2)]Pt(2)]Te(3) 177.20(2)8, Pt(2)]Te(3) 2.6225(7) Å] and m]Te(1)Ph is trans to the P(2)Et3 group [Te(1)]Pt(2)]P(2) 176.91(4)8, Pt(2)]P(2) 2.284(2) Å].Thus Pt(2) lies in a well defined square planar configuration with respect to its ligands as is normal for PtII. The maximum deviation of any of the ligated atoms from the mean plane Pt(2)Te(1)Te(2)Te(3)P(2) is only 0.014 Å. The Pt(1) atom carries a PEt3 group [Pt(1)]P(1) 2.392(2) Å] and is also ligated by a nido-CB10H11 cage framework. However, unusually the carbon atom in the cage has migrated to the upper pentagonal belt so that Pt(1) is coordinated by an open BBBBB face.The X-ray diVraction data for complex 5 were of good quality and collected at low temperatures. This allowed the location of C(10) by comparison of the anisotropic thermal parameters of this atom with its neighbouring atoms. Further confirmation of the correct identifi- cation of C(10) comes from an examination of the C(10)]B separations (average 1.70 Å) which as expected for the more electronegative C atom are ca. 0.08 Å shorter than related B]B connectivities (1.78 Å) in the boron cage.Migration of carbon atoms in reactions of dicarbon icosahedral metallacarbaboranes containing nido-7,8-R2-7,8-C2B9H9 (R = H or Me) ligands is not uncommon,8,15,16 but a carbon atom site exchange has not to our knowledge been previously observed with a monocarbon icosahedral metallacarbaborane. The atom Pt(2) is formally PtII, d8 with 16e2 in its valence shell, counting 2e2 each from the terminal [TePh]2 and PEt3 groups, and four from the m-TePh system.In contrast Pt(1) is formally PtIV, d6 with an 18e2 shell receiving 6e2 from the [nido- 2-CB10H11]32 anion, 2 from the P(1)Et3 ligand and 4 from the m-(TePh)2 system. Whereas Pt(2) is ligated by four ligands, the groups around Pt(1) occupy six sites since an h5 carbaborane cage is generally regarded as being tridentate.17 In accord with the diVerent co-ordination numbers of the two Pt atoms, the Pt(1)]P(1) bond [2.392(2) Å] is somewhat longer than the Pt(2)]P(2) [2.284(2) Å] connectivity, as is generally found with PtPEt3 complexes with co-ordination numbers of 6 and 4.5 The NMR data (Table 1) for compound 5 are in accord with the results of the X-ray diVraction study.In the 31P-{1H} NMR spectrum as expected there are two resonances for the nonequivalent PEt3 groups. The 13C-{1H} NMR spectrum had a very broad peak at d 45.5 due to the cage carbon nucleus, and correspondingly there is a singlet peak for this group in the 1H NMR spectrum at d 2.66.8 The 11B-{1H} NMR spectrum revealed broad unresolved peaks aVording no diagnostic information.Conclusion The motivation for the research described in this paper was to synthesize complexes of the type [Pt(EPh)(PEt3)2(h5-7-CB10- H11)] (E = Se or Te) and to investigate their chemistry. Instead several new compounds were obtained having unprecedented molecular structures. Further studies in this area are warranted, particularly as the pathways by which the various products are formed are uncertain. The structures of 4 and 5 are especially novel, that of the latter arising from a low energy polytopal rearrangement of the cage in the precursor 1, such a process not having been observed previously in a monocarbon metallacarbaborane. Experimental General All experiments were conducted under an atmosphere of dry argon using Schlenk tube techniques.Solvents were freshly distilled under nitrogen from appropriate drying agents before use. Light petroleum refers to that fraction of boiling point 40– 60 8C.Chromatography columns (ca. 30 cm long and 3 cm in diameter) were packed under nitrogen with silica gel (Acros 70– 230 mesh). The NMR measurements were recorded at the following frequencies: 1H at 360.13, 13C at 90.56, 11B at 115.55 and 31P at 145.78 MHz. The reagents nido-7-NMe3-7-CB10H12 18 and [PtCl2(PEt3)2] 19 were prepared according to literature methods. The salt Na3[nido-7-CB10H11] was synthesized according to the method of Knoth et al.20 and used to prepare Na[Pt(PEt3)2(h5- 7-CB10H11)] 1 as described earlier.1a The species Te2Ph2, PhSeCl and Se2Ph2 were used as commercially supplied by Aldrich.Synthesis of the platinum–selenium complexes A thf (20 cm3) solution of the reagent 1 (0.50 mmol), prepared in situ and cooled with a toluene–liquid nitrogen bath to 295 8C, was added to a thf (10 cm3) solution of PhSeCl (0.25 g, 0.50 mmol) using a syringe. After warming the mixture to room2846 J.Chem. Soc., Dalton Trans., 1998, Pages 2839–2847 Table 6 Crystallographic data and refinement details for compounds 2a–5 Formula M Colour, habit Crystal size/mm Crystal system Space group a/Å b/Å c/Å b/8 U/Å3 Z Dc/g cm23 m(Mo-Ka)/cm21 F(000) 2q Range/8 Reflections collected Unique reflections R(int) h,k,l Ranges Final residuals * wR2 (R1) Weighting factors * a, b Final electron-density diVerence features (maximum,minimum)/ e Å23 Goodness of fit on F2 2a C19H35B10PPtSe2 755.6 Purple prism 0.30 × 0.40 × 0.60 Monoclinic P21/n 9.139(3) 14.9839(11) 20.095(3) 98.85(2) 2772.6(9) 4 1.810 77.52 1440 5–50 12 953 4858 0.0413 211 to 9, 217 to 17, 223 to 16 0.0953 (0.0394) 0.0498, 0.0000 2.07, 21.30 1.009 3 C17H38B10ClOPPtSe 707.04 Orange block 0.10 × 0.20 × 0.30 Monoclinic P21/c 11.2452(11) 11.9971(13) 20.475(3) 99.035(13) 2728.0(6) 4 1.722 66.45 1368 4–50 14 147 4814 0.0261 213 to 14, 215 to 11, 226 to 24 0.0787 (0.0308) 0.0447, 2.6472 2.899, 21.421 1.061 4 C20H47B10ClP2PtTe?CH2Cl2 900.68 Yellow block 0.50 × 0.40 × 0.20 Monoclinic P21/c 17.617(2) 10.8358(8) 17.866(2) 97.036(11) 3384.8(6) 4 1.767 53.36 1744 5–50 17 692 5932 0.0307 220 to 20, 212 to 12, 28 to 21 0.0819 (0.0298) 0.0343, 23.1239 0.89, 21.11 1.095 5 Monoclinic P21/c 22.050(5) 10.023(2) 21.422(4) 115.40(2) 4276.7(14) 4 2.131 86.38 2536 5–50 19 603 7479 0.0398 221 to 26, 211 to 11, 225 to 25 0.0715 (0.0295) 0.0248, 17.5048 1.35, 21.18 1.171 * Refinement was by full-matrix least squares on all F2 data: wR2 = [Sw(Fo 2 2 Fc 2)2/Sw(Fo 2)2]� �� where w = [s2(Fo 2) 1 (aP)2 1 bP]21 and P = [max(Fo 2, 0) 1 2Fc 2]/3.The value in parentheses is given for comparison with refinements based on Fo with a typical threshold of F > 4s(F) with R1 = S||Fo| 2 |Fc||/S|Fo| and w21 = [s2(Fo) 1 g|Fo|2]. temperature it was stirred for 2 h. Solvent was removed in vacuo and the dark yellow residue was dissolved in CH2Cl2 (50 cm3) and filtered through a Whatman 1 mm poly(tetrafluoroethylene) membrane.The volume of the filtrate was reduced to ca. 5 cm3 and loaded onto a silica gel column. Elution with CH2Cl2–light petroleum (1: 3) aVorded a blue-purple band 2b, followed quickly by an intense red-purple band 2a and then a deep red band 3. Further elution with CH2Cl2–light petroleum (1 : 1) aVorded a yellow fraction containing [Pt(SePh)2(PEt3)2]. Solvent was removed in vacuo from each eluate and the respective solids obtained crystallized. In this manner purple prisms of [Pt(SePh)(PEt3)(h5-8-SePh-7-CB10H10)] 2a (0.030 g, 15%) (Found: C, 30.2; H, 4.7.C19H35B10PPtSe2 requires C, 30.2; H, 4.7%) were obtained from pentane at 260 8C, and bluish purple microcrystals of [Pt(SePh)(PEt3)(h5-9-SePh-7-CB10H10)] 2b (0.015 g, 8%) (Found: C, 30.4; H, 4.8. C19H35B10PPtSe2 requires C, 30.2; H, 4.7%) were obtained from CH2Cl2–pentane (1 : 8, 2 cm3). Red crystals of [Pt(SePh)(PEt3){h5-8-O(CH2)4Cl-7- CB10H10}] 3 (0.07 g, 35%) (Found: C, 28.9; H, 5.4.C17H38B10- ClOPPtSe requires C, 29.9; H, 5.4%) were grown by diVusion of a hexane solution of the complex into CH2Cl2. Finally yellow crystals of [Pt(SePh)2(PEt3)2] (0.03 g, 15%) (Found: C, 39.0; H, 5.4. C24H40P2PtSe2 requires C, 39.0; H, 5.4%) were isolated from CH2Cl2–hexane (1 : 4, 5 cm3). If Ph2Se2 was the reagent of choice the isomers 2 were formed but 3 was not observed. Synthesis of the platinum–tellurium complexes A freshly prepared thf (20 cm3) solution of complex 1 (0.66 mmol), prepared in situ, was cooled to 295 8C, then a thf (15 cm3) solution containing Te2Ph2 (0.135 g, 0.33 mmol) and iodine (0.083 g, 0.33 mmol) (yielding PhTeI) was added using a syringe.After warming to room temperature, an orange-brown solution formed and this was maintained at 40 8C for 1 h. Solvent was removed in vacuo, the residue extracted with CH2Cl2 (20 cm3) and filtered through a Whatman 1 mm poly(tetrafluoroethylene) membrane to give a clear deep red solution which was reduced in volume to ca. 5 cm3. Column chromatography, eluting with CH2Cl2–light petroleum (3 : 1) removed an orange-red band of 5 followed by a bright yellow band of 4. Evaporation of solvent in vacuo and then crystallization of the respective solids from CH2Cl2–light petroleum (1 : 8, 5 cm3) gave yellow block-like crystals of [Pt(PEt3)2{h5-9-Te(Ph)CH2Cl-7-CB10- H10}] 4 (0.075 g, 20%) (Found: C, 29.8; H, 6.0. C20H47B10- ClP2PtTe requires C, 29.5; H, 5.8%), and deep red prisms of [Pt2(TePh)(m-TePh)2(PEt3)2(h5-2-CB10H11)] 5 (0.085 g, 25%) (Found: C, 27.0; H, 4.0.C31H56B10P2Pt2Te3 requires C, 27.1; H, 4.1%). Crystallography Crystals of complex 2a were grown from n-hexane by cooling to 260 8C. Crystals of 3, 4 and 5 were grown by diVusion of n-hexane into CH2Cl2 solutions of the complexes. Crystals of complex 4 were obtained as large yellow plates and that used for data collection was cut from a larger crystal.All crystals were mounted on glass fibres and data were collected at 173 K on a Siemens SMART CCD area detector three-circle (2a, 3 and 4) or P4 four-circle (5) diVractometers (Mo-Ka X-radiation, graphite monochromator, l � = 0.710 73 Å). It was confirmed that crystal decay had not taken place during the course of the data collections. In the studies of 2a, 3 and 4, narrow ‘frames’ were collected for 0.38 increments in w for three settings of fl. In each of these three cases a total of 1271 frames of data were collected aVording rather more than a hemisphere of data for each experiment.The substantial redundancy in data allows empirical absorption corrections (SADABS)21 to be applied using multiple measurements of equivalent reflections. The data frames were integrated using SAINT.21 For 5 data were collected with the diVractometer operating in the w-scan mode using XSCANS.21 Data were corrected for Lorentz-polarization and X-ray absorption eVects, the latter by a semiempirical method based upon y-scan data. All structures were solved byJ.Chem. Soc., Dalton Trans., 1998, Pages 2839–2847 2847 conventional direct methods and refined by full-matrix least squares on all F2 data using SHELXTL version 5.03.21 All non-hydrogen atoms were refined with anisotropic thermal parameters. The cage carbon atoms in all complexes were identified by their thermal parameters and bond distances to adjacent boron atoms. All hydrogen atoms were included in calculated positions with isotropic thermal parameters ca. 1.2 × (aromatic CH or BH) or 1.5 × (Me) the equivalent isotropic thermal parameters of their parent carbon atoms. The Cl atom of the TeCH2Cl group in compound 4 is disordered over two sites (67 : 33). The thermal parameters for the disordered Cl with major site occupancy are appreciably lower than those of the minor component and therefore the former is shown in Fig. 5. Additionally, the asymmetric unit contains one molecule of CH2Cl2 which is also disordered with two positions for the carbon atom.The molecule of CH2Cl2 lies close to the TeCH2Cl group in the asymmetric unit and it is probable that the disorder observed in these groups is caused by mutual packing interactions. Chemically equivalent distances within the disordered groups were weakly restrained to be equivalent to assist stable refinement. All calculations were carried out on Silicon Graphics Iris, Indigo or Indy computers and experimental data are summarised in Table 6.CCDC reference number 186/1044. See http://www.rsc.org/suppdata/dt/1998/2839/ for crystallographic files in .cif format. Acknowledgements We thank the Robert A. Welch Foundation for support (Grant AA-1201), Dr. Paul A. Jelliss for many helpful discussions and Dr. Dianne Ellis for the MO calculations. References 1 (a) S. A. Batten, J. C. Je L. Jones, D. F. Mullica, M. D. Rudd, E. L. Sappenfield, F. G. A.Stone and A. Wolf, Inorg. Chem., 1997, 36, 2570; (b) J. C. JeVery, P. A. Jelliss and F. G. A. Stone, Organometallics, 1998, 17, 1402; (c) I. Blandford, J. C. JeVery, H. Redfearn, L. H. Rees, M. D. Rudd and F. G. A. Stone, J. Chem. Soc., Dalton Trans., 1998, 1669. 2 G. D. Freiser, J. L. Little, J. C. HuVmann and L. J. Todd, Inorg. Chem., 1979, 18, 755. 3 W. B. Hewer, A. E. True, P. N. Swepson and B. M. HoVmann, Inorg. Chem., 1988, 27, 1474 and refs. therein. 4 G. Ferguson, M.Parvez, J. A. McCurtian, O. N. Dhubhghaill, T. R. Spalding and D. Reed, J. Chem. Soc., Dalton Trans., 1987, 699; Faradoon, O. N. Dhubhghaill, T. R. Spalding, G. Ferguson, B. Kaitner, X. L. R. Fontaine and J. D. Kennedy, J. Chem. Soc., Dalton Trans., 1989, 1657. 5 A. G. Orpen, L. Brammer, F. H. Allen, O. Kennard, D. Watson and R. Taylor, J. Chem. Soc., Dalton Trans., 1989, S1. 6 CAChe Scientific, The Oxford Molecular Group, Oxford, 1994. 7 C. A. Tolman, Chem. Rev., 1977, 77, 313. 8 S. A. Brew and F. G. A. Stone, Adv. Organomet. Chem., 1993, 35, 135. 9 (a) D. F. Mullica, E. L. Sappenfield, F. G. A. Stone and S. F. Woollam, Organometallics, 1994, 13, 157; (b) M. Gómez-Saso, D. F. Mullica, E. L. Sappenfield and F. G. A. Stone, Polyhedron, 1996, 15, 793. 10 T. Peymann, K. Kück and D. Gabel, Inorg. Chem., 1997, 36, 5138. 11 N. Petragnani, L. Torres and K. J. Wynne, J. Organomet. Chem., 1975, 92, 185. 12 E. H. S. Wong and M. F. Hawthorne, Inorg. Chem., 1978, 17, 2863; R.E. King, S. B. Miller, C. B. Knobler and M. F. Hawthorne, Inorg. Chem., 1983, 22, 3548; H. C. Kang, S. S. Lee, C. B. Knobler and M. F. Hawthorne, Inorg. Chem., 1991, 30, 2024; I. T. Chizhevsky, I. V. Pisareva, P. V. Petrovskii, V. I. Bregadze, A. I. Yanovsky, Yu. T. Struchkov, C. B. Knobler and M. F. Hawthorne, Inorg. Chem., 1993, 22, 3393. 13 V. K. Jain, S. Kannan and R. Bohra, Polyhedron, 1992, 11, 1551. 14 D. M. Giolando, T. B. Rauchfuss and A. L. Rheingold, Inorg.Chem., 1987, 26, 1636. 15 M. F. Hawthorne, K. P. Callahan and R. J. Wiersema, Tetrahedron, 1974, 30, 1795; C. B. Knobler, T. B. Marder, E. A. Mizusawa, R. G. Teller, J. A. Long, P. E. Behnken and M. F. Hawthorne, J. Am. Chem. Soc., 1984, 106, 2990. 16 S. A. Brew, N. Carr, J. C. JeVery, M. U. Pilotti and F. G. A. Stone, J. Am. Chem. Soc., 1992, 114, 2203; S. Li and F. G. A. Stone, Polyhedron, 1993, 12, 1689. 17 T. P. Hanusa, Polyhedron, 1982, 1, 663. 18 J. Ples¡ek, T. Jelínek, E.Drdakova, S. Her¡mánek and B. Stíbr, Collect. Czech. Commun., 1984, 49, 1559. 19 G. W. Parshall, Inorg. Synth., 1970, 12, 26. 20 W. H. Knoth, J. L. Little, J. R. Lawrence, F. R. Scholer and L. J. Todd, Inorg. Synth., 1968, 11, 33. 21 Bruker X-ray Instruments, Madison, WI, 1995. Received 18th May 1998; Paper 8/03702GJ. Chem. Soc., Dalton Trans., 1998, Pages 2839–2847 2847 conventional direct methods and refined by full-matrix least squares on all F2 data using SHELXTL version 5.03.21 All non-hydrogen atoms were refined with anisotropic thermal parameters.The cage carbon atoms in all complexes were identified by their thermal parameters and bond distances to adjacent boron atoms. All hydrogen atoms were included in calculated positions with isotropic thermal parameters ca. 1.2 × (aromatic CH or BH) or 1.5 × (Me) the equivalent isotropic thermal parameters of their parent carbon atoms. The Cl atom of the TeCH2Cl group in compound 4 is disordered over two sites (67 : 33).The thermal parameters for the disordered Cl with major site occupancy are appreciably lower than those of the minor component and therefore the former is shown in Fig. 5. Additionally, the asymmetric unit contains one molecule of CH2Cl2 which is also disordered with two positions for the carbon atom. The molecule of CH2Cl2 lies close to the TeCH2Cl group in the asymmetric unit and it is probable that the disorder observed in these groups is caused by mutual packing interactions.Chemically equivalent distances within the disordered groups were weakly restrained to be equivalent to assist stable refinement. All calculations were carried out on Silicon Graphics Iris, Indigo or Indy computers and experimental data are summarised in Table 6. CCDC reference number 186/1044. See http://www.rsc.org/suppdata/dt/1998/2839/ for crystallographic files in .cif format. Acknowledgements We thank the Robert A. Welch Foundation for support (Grant AA-1201), Dr.Paul A. Jelliss for many helpful discussions and Dr. Dianne Ellis for the MO calculations. References 1 (a) S. A. Batten, J. C. JeVery, P. L. Jones, D. F. Mullica, M. D. Rudd, E. L. Sappenfield, F. G. A. Stone and A. Wolf, Inorg. Chem., 1997, 36, 2570; (b) J. C. JeVery, P. A. Jelliss and F. G. A. Stone, Organometallics, 1998, 17, 1402; (c) I. Blandford, J. C. JeVery, H. Redfearn, L. H. Rees, M. D. Rudd and F. G. A. Stone, J. Chem. Soc., Dalton Trans., 1998, 1669. 2 G. D. Freiser, J. L. Little, J. C. HuVmann and L. J. Todd, Inorg. Chem., 1979, 18, 755. 3 W. B. Hewer, A. E. True, P. N. Swepson and B. M. HoVmann, Inorg. Chem., 1988, 27, 1474 and refs. therein. 4 G. Ferguson, M. Parvez, J. A. McCurtian, O. N. Dhubhghaill, T. R. Spalding and D. Reed, J. Chem. Soc., Dalton Trans., 1987, 699; Faradoon, O. N. Dhubhghaill, T. R. Spalding, G. Ferguson, B. Kaitner, X. L. R. Fontaine and J. D. Kennedy, J. Chem. Soc., Dalton Trans., 1989, 1657. 5 A. G. Orpen, L. Brammer, F. H. Allen, O. Kennard, D. Watson and R. Taylor, J. Chem. Soc., Dalton Trans., 1989, S1. 6 CAChe Scientific, The Oxford Molecular Group, Oxford, 1994. 7 C. A. Tolman, Chem. Rev., 1977, 77, 313. 8 S. A. Brew and F. G. A. Stone, Adv. Organomet. Chem., 1993, 35, 135. 9 (a) D. F. Mullica, E. L. Sappenfield, F. G. A. Stone and S. F. Woollam, Organometallics, 1994, 13, 157; (b) M. Gómez-Saso, D. F. Mullica, E. L. Sappenfield and F. G. A. Stone, Polyhedron, 1996, 15, 793. 10 T. Peymann, K. Kück and D. Gabel, Inorg. Chem., 1997, 36, 5138. 11 N. Petragnani, L. Torres and K. J. Wynne, J. Organomet. Chem., 1975, 92, 185. 12 E. H. S. Wong and M. F. Hawthorne, Inorg. Chem., 1978, 17, 2863; R. E. King, S. B. Miller, C. B. Knobler and M. F. Hawthorne, Inorg. Chem., 1983, 22, 3548; H. C. Kang, S. S. Lee, C. B. Knobler and M. F. Hawthorne, Inorg. Chem., 1991, 30, 2024; I. T. Chizhevsky, I. V. Pisareva, P. V. Petrovskii, V. I. Bregadze, A. I. Yanovsky, Yu. T. Struchkov, C. B. Knobler and M. F. Hawthorne, Inorg. Chem., 1993, 22, 3393. 13 V. K. Jain, S. Kannan and R. Bohra, Polyhedron, 1992, 11, 1551. 14 D. M. Giolando, T. B. Rauchfuss and A. L. Rheingold, Inorg. Chem., 1987, 26, 1636. 15 M. F. Hawthorne, K. P. Callahan and R. J. Wiersema, Tetrahedron, 1974, 30, 1795; C. B. Knobler, T. B. Marder, E. A. Mizusawa, R. G. Teller, J. A. Long, P. E. Behnken and M. F. Hawthorne, J. Am. Chem. Soc., 1984, 106, 2990. 16 S. A. Brew, N. Carr, J. C. JeVery, M. U. Pilotti and F. G. A. Stone, J. Am. Chem. Soc., 1992, 114, 2203; S. Li and F. G. A. Stone, Polyhedron, 1993, 12, 1689. 17 T. P. Hanusa, Polyhedron, 1982, 1, 663. 18 J. Ples¡ek, T. Jelínek, E. Drdakova, S. Her¡mánek and B. Stíbr, Collect. Czech. Commun., 1984, 49, 1559. 19 G. W. Parshall, Inorg. Synth., 1970, 12, 26. 20 W. H. Knoth, J. L. Little, J. R. Lawrence, F. R. Scholer and L. J. Todd, Inorg. Synth., 1968, 11, 33. 21 Bruker X-ray Instruments, Madison, WI, 1995. Received 18th May 1998; Paper 8/03702G

ISSN:1477-9226    

DOI:10.1039/a803702g

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, Pages 2849–2854 2849 Aromatic substituted metallacarboranes as extractants of 137Cs and 90Sr from nuclear wastes Clara Viñas,a Josep Bertran,a Sílvia Gomez,a Francesc Teixidor,*,a Jean-François Dozol,*,b Hélène Rouquette,b Raikko Kivekäs a and Reijo Sillanpää d a Institut de Ciència de Materials de Barcelona (CSIC), Campus de la U.A.B., 08193 Bellaterra, Spain. E-Mail: teixidor@icmab.es b D.C.C./D.E.S.D./S.E.P., C.E.A. Cadarache, 13108 Saint Paul lez Durance, France.E-Mail: DOZOLjf@DESDCAD.cea.fr c Department of Chemistry, University of Helsinki, Box 55, FIN-00014 Helsinki, Finland d Department of Chemistry, University of Turku, FIN-20014 Turku, Finland Phenyl- and 1,2-diphenyl-1,2-dicarba-closo-dodecaborane have been synthesized and deboronated to yield [7-C6H5-7,8-C2B9H11]2 and [7,8-(C6H5)2-7,8-C2B9H10]2. Reaction of the monophenyl with KOBut and CoCl2 in 1,2-dimethoxyethane (dme) led to [3,39-Co(1-C6H5-1,2-C2B9H10)2]2 12.This has been fully characterized by X-ray analysis. A similar reaction with [7,8-(C6H5)2-7,8-C2B9H10]2 did not yield the expected sandwich compound. On the contrary, reaction of [7,9-(C6H5)2-7,8-C2B9H10]2 with KOBut and CoCl2 in a mixture of dme and diethylene glycol dimethyl ether led to [3,39-Co{1,7-(C6H5)2-1,7-C2B9H9}2] 22. The two sandwich complexes were tested for liquid–liquid extraction and transport through supported liquid membranes of 137Cs, 90Sr and 152Eu.Extractions for 137Cs were very good at pH 3 but decreased considerably at pH 1 for H[1], while H[2] showed good eYciency even at this pH. The extraction of 90Sr was performed with the incorporation of a synergistic linear polyether and was good at pH 3 and 1. For the extraction of 152Eu, compound H[2] displayed good eYciency. Transport experiments of Cs using supported liquid membranes were performed with H[1] and H[2] and o-nitrophenyl hexyl ether as the membrane solvent.The permeability of 137Cs for compound H[2] was 30.9 cm h21 while for H[1] it was 7.95 cm h21. These permeabilities are much higher than those of usual carriers under comparable conditions. Introduction In 1965 the first metallacarboranes, [3,39-Fe(1,2-C2B9H11)2]n2 (n = 1 or 2) were reported.1 Owing to their interesting properties and applications, their chemistry developed very quickly.2 Current applications of these novel species include: (1) solubility in electron-donating organic solvents, e.g.in solvent extraction of radionuclides;3 (2) isolation, separation and characterization of organic bases, including natural substances;3 (3) radiometal carriers;4 and (4) electron acceptor molecules, e.g. [3,39-Ni(1,2-C2B9H11)2].5 Concerning the solvent extraction of radionuclides, nuclear fuel reprocessing operations produce high and medium level liquid wastes (HLLW and MLLW) containing diVerent longlived radioactive elements as b/g emitters (Tc, I, Zr, Se, Cs, etc.) and a emitters (transuranium actinides: Np, Pu, Am, Cm, etc.).In order to simplify the conditioning of such wastes, it would be highly desirable selectively to remove these very long-lived radionuclides. This would decrease the volume of wastes intended for disposal in deep geological repositories, using instead subsurface repositories which are easier to manage.6 Furthermore, these nuclides, separated from the matrix, could afterwards be turned into short-lived elements or nonradioactive ones through transmutation.One of the generally used chemical separation processes in fuel treatment is liquid– liquid extraction by specific molecules. Cobaltabis(dicarbollide), [3,39-Co(1,2-C2B9H11)2]2, has shown a very high eYciency in the extraction of 137Cs, when nitrobenzene is used as solvent.3,7 However, the use of this solvent is very inconvenient due to technological and safety reasons. On the other hand, most of the selective sensors for cesium contain nitrobenzene 8 or its derivatives;9 which shows the importance of introducing aromatic groups in cobaltabis- (dicarbollide) derivatives, in order to enhance the extracting capacity of 137Cs.Results and discussion Synthetic results The synthesis of C-substituted 1,2-dicarba-closo-dodecaboranes (o-carboranes) from decaborane B10H14 and the appropriate acetylenic species (phenylacetylene and diphenylacetylene) was required to produce the cobaltabis(dicarbollide) derivatives incorporating aromatic rings.10 Deboronation of 1-C6H5-1,2- C2B10H11 and 1,2-(C6H5)2-1,2-C2B10H10 with an excess of KOH in EtOH as solvent led to the nido species [7-C6H5-7,8-C2B9H11]2 and [7,8-(C6H5)2-7,8-C2B9H10]2.11,12 Reaction of the monophenyl with KOBut and CoCl2, in 1,2-dimethoxyethane (dme) as solvent led to the complex [3,39-Co(1-C6H5-1,2-C2B9H10)2]2 12.12 Two geometric isomers resulted, which we were not able to separate (racemic mixture and meso form, Fig. 1) owing to their extremely similar physical properties.However, chemical analyses established their stoichiometric purity although the pattern of the 11B NMR resonances clearly suggests the existence of more than one isomer. Crystals of Na[3,39-Co(1-C6H5-1,2-C2B9H10)2]?0.4C6H5- CH3, used for X-ray analysis, were grown from acetone– toluene. The crystal structure contains disordered sodium cations, three crystallographically non-equivalent [3,39-Co(1- C6H5-1,2-C2B9H10)2]2 units and toluene molecules.Unit A has crystallographic two-fold symmetry with the metal atom Fig. 1 Geometric isomers of complex 12 (view from the top of the pentagonal faces).2850 J. Chem. Soc., Dalton Trans., 1998, Pages 2849–2854 occupying the symmetry axis. Units B and C are at common positions and show pseudo-twofold symmetry. Despite the crystallographic dissimilarity, the three complex units are geometrically very similar: (i) in each unit the mutual orientation of the two dicarbollide ligands is practically identical, the conformation of the co-ordinated pentagonal C2B3 faces being staggered so that the non-substituted cluster carbon of one face is oriented between the cluster carbons of the other face; (ii) in each unit the dihedral angles between the pentagonal C2B3 faces [6.1(9)–8.2(6)8] as well as the B(10)]Co(3)2B(109) jackknife angles [176.7(3)–177.6(4)8] are equal within experimental errors. A view of the complex unit B is shown in Fig. 2, and selected interatomic distances and angles are reported in Table 1. Several attempts at complexation of [7,8-(C6H5)2-7,8-C2B9- H10]2 to cobalt were made in our group, but it was a nonstraightforward reaction which did not allow the isolation of the product, even under forcing reaction conditions, e.g. increasing the temperature of the refluxing or the reaction time. The reason may be due to the steric crowding caused by the aromatic rings. As it was known that [7,8-(C6H5)2-7,8-C2B9- Fig. 2 Perspective view of the complex unit B of Na[3,39-Co(1-C6H5- 1,2-C2B9H10)2]?0.4C6H5CH3 showing 20% displacement ellipsoids.Hydrogen atoms are omitted for clarity. Table 1 Selected interatomic distances (Å) and angles (8) for Na[1]? 0.4C6H5CH3 Complex unit Co3]C1 Co3]C2 Co3]B4 Co3]B7 Co3]B8 Co3]C19 Co3]C29 Co3]B49 Co3]B79 Co3]B89 C1]C2 C1]C13 C19]C29 C19]C139 B10]Co3]B10* B10]Co3]B109 A 2.115(8) 2.068(8) 2.124(10) 2.110(11) 2.106(12) 1.601(11) 1.511(11) 177.6(4) B 2.130(8) 2.097(8) 2.115(11) 2.101(10) 2.120(11) 2.133(9) 2.097(9) 2.108(11) 2.109(10) 2.112(11) 1.629(11) 1.508(12) 1.640(12) 1.544(13) 176.7(3) C 2.116(9) 2.081(8) 2.097(12) 2.128(12) 2.102(12) 2.117(9) 2.087(8) 2.083(10) 2.116(10) 2.146(12) 1.649(13) 1.493(13) 1.620(12) 1.507(12) 176.8(3) * Equivalent position: 2x 1 1, y, 2z 1 1– 2.H10]2 isomerizes at high temperature to give [7,9-(C6H5)2-7,8- C2B9H10]2,13 this compound was used to form the corresponding cobaltabis(dicarbollide) derivative under similar conditions as those for [7-C6H5-7,8-C2B9H11]2. However, higher temperatures were needed for the reaction to proceed, and a mixture of dme and diethylene glycol dimethyl ether (dime) (5 : 1 v/v) was used as solvent.Precipitation with [N{(CH2)3CH3}4]Br led to the pure compound [N{(CH2)3CH3}4][3,39-Co{1,7-(C6H5)2-1,7- C2B9H9}2], [N{(CH2)3CH3}4][2], in 55% yield. As has been stated, the use of nitrobenzene as solvent increases considerably the eYciency in the extraction of caesium.3,7 Likewise, most extraction essays are carried out in solvents incorporating a nitrophenyl group (e.g.nitrophenyl hexyl ether and nitrophenyl octyl ether), as will be described. This apparently necessary presence of the nitrophenyl group in caesium extraction or detection motivated us to synthesize the closo compound 1-p-C6H4NO2-1,2-C2B10H11 14 with the purpose of preparing the cobaltabis(dicarbollide) derivative.After successful partial degradation, no convenient route to the corresponding cobaltabis(dicarbollide) derivatives was found and the complex could not be isolated. Incorporation of the moiety C6H4NO2 on boron atoms was then proposed as an alternative and reaction of [3,39-Co(1,2-C2B9H11)2]2 with AlCl3 and nitrobenzene was attempted. It was expected that the nitrophenyl group could be introduced at the 8,89 positions. Analysis of the NMR data led us to hypothesize the formation of the zwitterion [3,39-Co(8-C6H5ONO-1,2-C2B9H10)(19,29-C2B9H11)] as well as several chlorinated products.The absence of a negative charge in this zwitterion made it useless for extraction purposes. Extraction and transport through supported liquid membranes The cobaltabis(dicarbollide) derivatives presented in this paper have been first tested in liquid–liquid extraction of 137Cs, 90Sr and 152Eu. Table 2 presents the distribution coeYcients of 137Cs (DCs), of 90Sr (DSr) and of 152Eu (DEu), defined as the equilibrium ratio of the radionuclide between the organic and the aqueous phases. The distribution coeYcients of the metals decrease with pH in the feed solution due to the equilibrium of the cation Mn1, which is governed in acidic media for a basic cobaltabis(dicarbollide) by eqn.(1).7 Protons in the organic phase are provided nH1(org) 1 Mn1(aq) nH1(aq) 1 Mn1(org) (1) by the cobaltabis(dicarbollide) and by the nitric acid in the aqueous phase, with an extraction constant Kex [eqn.(2)]. Kexn1 = [H1(aq)]n [Mn1(org)] [H1(org)]n [Mn1(aq)] (2) In a first approach, for the extraction of trace level radioactive cations producing a small change in the nitric acid concentration, distribution coeYcients can be linked to the extraction constant by the relationship (3) where [H1CoB2 2] DMn1 = Mn1(org) Mn1(aq) = Kex [H1CoB2 2] [HNO3] (3) corresponds to the concentration of the protonated cobaltabis( dicarbollide) species, H[1] or H[2]. The higher the nitric acid concentration the lower will be the distribution coeYcient.For the extraction of 137Cs, both tested compounds show a very high extraction eYciency at pH 3 (D > 1000), regardless of the nature of the exo-cluster group. This eYciency is expected to be lower on increasing the acidity of the medium. This is the behavior displayed by H[1], for which D decreases from >1000 to 4, just by varying the pH value from 3 to 1. However, H[2] shows a good eYciency even at pH 1.In the extraction of 90Sr the compounds show a very high extraction eYciency, even at pH 1, upon the incorporation ofJ. Chem. Soc., Dalton Trans., 1998, Pages 2849–2854 2851 Table 2 Distribution coeYcients (DM) in aqueous HNO3–nitrophenyl hexyl ether of the diVerent radionuclides extracted by the protonated form of cobaltabis(dicarbollide) derivatives DCs DSr DEu Compound H[1] H[2] pH 3 >1000 >1000 pH 1 4 27 pH 3 8 22 pH 1 <1023 0.08 pH 1* >1000 >1000 pH 3 55 >1000 pH 1 0.02 <1023 * Essays carried out with addition of a linear polyether (polyethylene glycol) to the organic phase (0.003 M).a synergistic linear polyether added to the organic phase. For the extraction of 152Eu, distribution coeYcients at pH 3 are excellent for compound H[2]. Previous results with [3,39- Co(1,2-C2B9H11)2]2 derivatives incorporating long lipophilic chains have shown excellent extractive properties.15 The results obtained in the extraction of cesium by these compounds led us to perform some transport experiments by using supported liquid membranes (SLM) with o-nitrophenyl hexyl ether as the membrane solvent.Preliminary results carried out with compounds H[1] and H[2] showed that the best transport performance was with the latter. The transport of radionuclides from aqueous HNO3 solutions was monitored by measurement of the decrease of radioactivity in the feed solution by g spectrometry analysis.This allowed determination of the constant permeabilities P/cm h21 of 137Cs permeating through the SLM for 24 h by plotting the logarithm of the ratio C:C0 vs. time, as described in the model of mass transfer proposed by Danesi,16 eqn. (3), where C is ln SC C0D= 2e S V Pt (3) concentration of the cation in the feed solution at time t (mol l21) C0 the initial concentration of the cation in the feed solution (mol l21), e the volume porosity of the SLM (%), S the membrane surface area (cm2), V the volume of the feed and stripping solutions (cm3) and t the time (h). Under these conditions, at pH 3, both compounds display very interesting results; the permeability for compound H[2] is 30.9 cm h21, showing an extraction of 92.9% of caesium in 1 h.Compound H[1] displays a slower transport with a permeability of 7.95 cm h21, e.g. an extraction of 52% in 1 h. As a comparison, permeabilities ranging from 1 to 4 cm h21 have been measured for several ‘carriers’ such as calix[4]arene, crowns-6, carbamoylmethylphosphine oxides or disphosphine dioxides under comparable conditions.Better permeabilities were achieved with calixarenes incorporating carbamoylmethylphosphine oxide moieties (4–7 cm h21). Although these results are very promising, fine modifi- cations on these compounds are still needed to improve their extraction capacity at lower pH.17 In fact, a linear behavior is only observed in the first part of the experiment, until t = 1 h.This eVect may be explained by the fact that counter transport of metal ions by cobaltabis(dicarbollide) anions is driven by the transfer of protons from the stripping phase into the feed phase. The complexation equilibrium is (4) where CoB2 2 corresponds to the cobaltabis- Cs1(aq) 1 H1CoB2 2(org) Cs1CoB2 2(org) 1 H1(aq) (4) (dicarbollide) anion, i.e. 12 or 22. Thus, in order to get maximum eYciency, the pH of the feed phase must be suYciently high completely to deprotonate the carrier in the interface.Similarly, the pH of the receiving phase must be low enough to force a complete reversal of the complexation–deprotonation balance, to encourage maximum stripping. As indicated in Table 2, the distribution coeYcients DCs decrease considerably with the pH. This means that, for a certain amount of transported caesium from the feed to the stripping phase, the same quantity of protons has been counter-transported from the stripping to the feed phase, and consequently the pH of the feed phase has decreased.This leads to a lower extraction of caesium after a certain time, i.e. the transport becomes slower. This is why the Danesi model is not valid after a certain time. In fact, this model is based on the hypothesis that reextraction takes place immediately and completely, which is not true in this case if the pH decreases, inducing an asymptotic line. In conclusion, cobaltabis(dicarbollide) derivatives are monoanionic compounds suitable for the extraction of radionuclides.This, along with their low charge density and resistance to radiation, makes them suitable for the removal of cationic radionuclides from nuclear wastes. The introduction of aromatic rings to the cluster permits one to modulate the extraction properties of the compound. The presence of two phenyl groups per cluster led to the best performance at pH 3 for the extraction of caesium. Transport experiments confirmed the interest in implementing cobaltabis(dicarbollide) derivatives on SLM to separate caesium from nuclear wastes.Experimental Commercial B10H14 was purified by sublimation at 0.01 mmHg (ca. 1.33 Pa). 1-Phenyl- and 1,2-diphenyl-1,2-dicarba-closododecaborane were synthesized according to the literature.10 The compound [3,39-Co(1-C6H5-1,2-C2B9H10)2]2 12 was prepared according to a previous paper.12 1,2-Dimethoxyethane and diethylene glycol dimethyl ether were dried with sodium– benzophenone.All organic and inorganic salts were analytical reagent grade and used as received. The solvents were reagent grade. All reactions were carried out under a dinitrogen atmosphere employing Schlenk techniques. Microanalyses were performed in our analytical laboratory on a Perkin-Elmer 240B microanalyzer. Infrared spectra of KBr pellets were obtained on a Nicolet 710-FT spectrophotometer, NMR spectra on a Bruker ARX-300 spectrometer equipped with the appropriate decoupling accessories.Preparations [N{(CH2)3CH3}4][3,39-Co{1,7-(C6H5)2-1,7-C2B9H9}], [N{(CH2)3CH3}4][2]. In a two-necked flask, [N(CH3)4][7,9- (C6H5)2-7,9-C2B9H10] 13 (0.360 g, 1.00 mmol) was dissolved in anhydrous 1,2-dimethoxyethane (25 cm3) and anhydrous diethylene glycol dimethyl ether (5 cm3) under dinitrogen and stirring. Then, potassium tert-butoxide (1.36 g, 10.5 mmol) and anhydrous CoCl2 (1.48 g, 10.5 mmol) were added. The reaction mixture was refluxed for 72 h.After cooling, the solvent was evaporated in vacuum and the residue extracted with 1 M HCl- (aq)–diethyl ether. After drying the ether layer with MgSO4, the solvent was evaporated. The residue was dissolved in a mixture of ethanol (2 cm3) and water (10 cm3) and treated with an excess of [N{(CH2)3CH3}4]Br in water. The dark red precipitate was filtered oV, washed with water and n-hexane and dried in vacuum to aVord [N{(CH2)3CH3}4][2] (yield 0.183 g, 55%). FTIR (KBr): n/cm21 = 3079, 3051, 3030, 3016 [n(C]H)aryl], 2966, 2938, 2875 [n(C]H)alkyl], 2566 [n(B]H)], 1483, 1448, 1384 [d(C]H)alkyl]. 1H NMR (300 MHz, CD3COCD3, 25 8C, SiMe4): d 7.60–6.75 (m, 20 H, CHaryl), 3.50–3.44 (m, 8 H, NCH2),2852 J. Chem. Soc., Dalton Trans., 1998, Pages 2849–2854 1.89–1.79 (m, 8 H, NCH2CH2), 1.51–1.39 [m, 8 H, N(CH2)2- CH2], 0.99 [t, 3J(HH) = 7.5 Hz, 12 H, CH3) and 3.8–1.3 (br, 18 H, BH). 11B NMR (96 MHz, CD3COCD3, 25 8C, BF3?Et2O): d 0.8 [d, 1J(BH) = 130 Hz, 4B], 23.8 (2B), 25.1 (2B), 26.1 (2B), 28.5 (2B), 210.2 (2B), 212.7 (2B) and 213.6 (2B). 13C{1H}- NMR (75 MHz, CD3COCD3, 25 8C, SiMe4): d 148.2, 144.3, 129.5, 129.4, 128.7, 127.9, 127.6, 126.4, 125.7, 125.2, 124.7 (Caryl), 80.4, 76.1, 72.5, 61.6 (Ccluster), 58.5 (NCH2), 23.5 (NCH2CH2), 19.5 [N(CH2)2CH2] and 12.9 (CH3) (Found: C, 60.66; H, 8.55; N, 1.69. Calc. for C32H47B18CoN?2C6H14: C, 60.63; H, 8.67; N, 1.61%). [3,39-Co(8-C6H5ONO-1,2-C2B9H10)(19,29-C2B9H11)]. In a two-necked flask, Cs[3,39-Co(1,2-C2B9H11)2] (0.250 g, 0.548 mmol) and AlCl3 (0.190 g, 1.425 mmol) were dissolved in anhydrous nitrobenzene (25 cm3) under dinitrogen and stirring.The mixture was heated to 80 8C for 4 h. On cooling, the precipitate was filtered oV and washed with nitrobenzene. The solid was discarded as the IR spectrum showed no B]H band between 2500 and 2600 cm21. Nitrobenzene was evaporated in vacuum and the residue washed with 5% HCl. After column chromatography (n-hexane–CH2Cl2 1: 1), [3,39-Co(8-C6H5- ONO-1,2-C2B9H10)(19,29-C2B9H11)] was isolated (yield 0.020 g, 9%). 1H NMR (300 MHz, CD3COCD3, 25 8C, SiMe4): d 8.71 [d, 3J(HH) = 9, 2 H, CHaryl], 8.29 [t, 3J(HH) = 9, 1 H, CHaryl], 7.98 [t, 3J(HH) = 9 Hz, 2 H, CHaryl], 4.42 (br, 1 H, CclusterH), 4.10 (br, 1 H, CclusterH) and 3.5–1.5 (br, 17 H, BH). 11B NMR (96 MHz, CD3COCD3, 25 8C, BF3?Et2O): d 19.9 [s, 1B, B(8)], 7.3 [d, 1J(BH) = 138, 1B], 4.8 [d, 1J(BH) = 78, 1B], 22.5 [d, 1J(BH) = 173, 1B], 24.3 [d, 1J(BH) = 147, 4B], 27.3 [d, 1J(BH) = 146, 4B], 215.1 [d, 1J(BH) = 161, 2B], 217.7 [d, 1J(BH) = 167, 2B], 220.8 [d, 1J(BH) = 210, 1B] and 224.2 [d, 1J(BH) = 171 Hz, 1B]. 13C{1H} NMR (75 MHz, CD3COCD3, 25 8C, SiMe4): d 140.6, 130.3, 125.5, 124.1 (Caryl), 66.2, 53.0 and 47.8 (Ccluster). Chlorination derivatives of Cs[3,39-Co(1,2-C2B9H11)2] were isolated after elution with more polar solvent mixtures (thf, CH3CN). The IR and NMR spectra of these products compare well with those previously reported.18 Crystallography Single crystal data for Na[3,39-Co(1-C6H5-1,2-C2B9H10)2]? 0.4C6H5CH3 were obtained at ambient temperature on a Rigaku AFC5S diVractometer using graphite monochromatized Mo-Ka radiation.The unit cell parameters were determined by least-squares refinement of 25 carefully centred reflections. Data obtained were corrected for Lorentz-polarization eVects, and for dispersion. Corrections for empirical absorption (y scan) were also applied. As the reflection power at high reflection angles was very poor, limited data were collected.A Table 3 Crystallographic data for Na[1]?0.4C6H5CH3 Chemical formula Crystal system M Space group a/Å b/Å c/Å b/8 U/Å3 ZT /8C l/Å Dc/g cm23 m/cm21 R1 a [I > 2s(I)] wR2 b [I > 2s(I)] Na[1]?0.4C6H5CH3 C16H30B18CoNa?0.4C7H8 Monoclinic 535.75 C2/c (No. 15) 39.479(3) 21.677(5) 24.156(3) 125.600(6) 16 809(5) 20 21 0.710 69 1.059 5.33 0.0927 0.2566 a R1 = S||Fo| 2 |Fc||/S|Fo. bwR2 = [Sw(|Fo 2| 2 |Fc 2|)2/Sw|Fo 2|2]� �� total of 11 127 reflections giving 10 940 unique reflections (Rint = 0.0426) were collected by w–2q scan mode (2qmax = 458).The structure was solved by direct methods by using the SHELXS 86 program19 and least-squares refinements and all subsequent calculations were performed using the SHELXL 97 program system.20 The asymmetric unit of the structure consists of one half of the [3,39-Co(1-C6H5-1,2-C2B9H10)2]2 complex unit (labelled A) having two-fold symmetry, two other units (labelled B and C) at common positions, one toluene solvent molecule and 2.5 disordered sodium cations.Refinement of all atoms, except the sodium cations, revealed seven residual electron maxima of 1.0–1.8 e Å23 in large cavities between the complex anions and we assumed that the maxima represent partially occupied sodium cations. Site occupation parameters of the sodium positions, resulting from refinement of the sodium cations with equivalent isotropic displacement parameters, were fixed in the final refinement.Non-hydrogen atoms of the toluene solvent were refined with isotropic, the remaining non-hydrogen atoms with anisotropic, displacement parameters. Hydrogen atoms were included in the calculations at the fixed distances from their host atoms and treated as riding atoms using the SHELXL 97 default parameters. CCDC reference number 186/1073. Determination of distribution coeYcients The distribution coeYcients D, were determined at room temperature (25 8C) by mixing the same volume of each phase at 100 revolutions min21 in a polypropylene test-tube, and then measuring the radioactivity in each phase by g spectrometry.To perform the extraction experiments, the extractant was washed previously with an aqueous 1 M HNO3 solution, leading to the formation of the protonated species (H[1] and H[2]). Then, 5 cm3 of the organic phase, i.e., a 0.01 M solution of the studied extractant in o-nitrophenyl hexyl ether, and aqueous feed solution (5 cm3; HNO3 containing traces of 137Cs, 90Sr and 152Eu) were mixed.To determine DM in the stripping experiments, 4 cm3 of the last organic phase were mixed with aqueous stripping solution (4 cm3) containing a lanthanide complexing agent [oxalic acid (0.5 M) or sodium citrate (0.25 M)]. Duplicate runs of each experiment were routinely performed. Supported liquid membranes A thin flat sheet SLM device described by Stolwijk et al.21 was used.The volume of both aqueous solutions was 50 cm3. The membrane was a “Celgard 2500 (of 25 mm thickness and 45% volume porosity) polypropylene microporous support soaked with a 0.01 M solution of the test compound in o-nitrophenyl hexyl ether. The surface area of the membrane was about 15–16 cm2, depending on the device; the mass of the organic phase was about 25 mg. This mass was determined by measuring the activity of the membrane after soaking it in an organic phase containing nuclides. Permeability determination The transport of 137Cs from synthetic aqueous solutions of HNO3 (pH 3) was monitored by measurement of the decrease in radioactivity in td solution and of the increase in the strip solution [sodium citrate (0.25 M)] by g spectrometry analysis.This allowed determination of the constant permeabilities P/cm h21 of caesium permeation through the SLM for 24 h, by plotting the logarithm of the ratio C:C0 vs. time. Acknowledgements We thank the EU for financial support under project CIPACT93- 0133 and the Comisión Interministerial de Ciencia y Tecnologia agency through MAT94-1414-CE; J.B. thanks the Generalitat de Catalunya for a Predoctoral Grant (FIAP/96-98.469).J. Chem. Soc., Dalton Trans., 1998, Pages 2849–2854 2853 References 1 M. F. Hawthorne, D. C. Young and P. A. Wegner, J. Am. Chem. Soc., 1965, 87, 1818. 2 M. F. Hawthorne and T. D. 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Dozol, presented at the International Conference on Accelerator-Driven Transmutation Technology and Applications, Las Vegas, 1994. 7 S. D. Reilly, C.F. V. Mason and P. H. Smith, Report LA-11695, Los Alamos National Laboratory, Los Alamos, NM, 1990. 8 C. J. Coetzee and A. J. Basson, Anal. Chim. Acta, 1976, 83, 361. 9 E. W. Baumann, Anal. Chem., 1976, 48, 548; C. J. Coetzee and A. J. Basson, Anal. Chim. Acta, 1977, 92, 399; K. Kimura, H. Tamura and T. Shono, J. Electroanal. Chem., Interfacial Electrochem., 1979, 105, 335; K. Kimura, A. Ishikawa, H. Tamura and T. Shono, J. Chem. Soc., Perkin Trans. 2, 1984, 447. 10 T.L. Heying, J. W. Ager, jun., S. L. Clark, D. J. Mangold, H. L. Goldstein, M. Hillman, R. J. Polak and J. W. Szymanski, Inorg. Chem., 1963, 2, 1089; M. M. Fein, D. Grafstein, J. E. Paustian, J. Bobinski, B. M. Lichstein, N. Mayes, N. N. Schwartz and M. S. Cohen, Inorg. Chem., 1963, 2, 1115; M. M. Fein, J. Bobinski, N. Mayes, N. Schwartz and M. S. Cohen, Inorg. Chem., 1963, 2, 1111. 11 M. F. Hawthorne, D. C. Young, P. M. Garrett, D. A. Owen, S. G. Schwerin and F. N. Tebbe, J. Am.Chem. Soc., 1968, 90, 862. 12 C. Viñas, J. Pedrajas, J. Bertran, F. Teixidor, R. Kivekäs and R. Sillanpää, Inorg. Chem., 1997, 36, 2482. 13 A. J. Welch and A. S. Weller, J. Chem. Soc., Dalton Trans., 1997, 1205; M. A. Fox and K. Wade, Polyhedron, 1997, 16, 2517. 14 M. F. Hawthorne, T. E. Berry and P. A. Wegner, J. Am. Chem. Soc., 1965, 87, 4746. 15 C. Viñas, S. Gomez, J. Bertran, F. Teixidor, J. F. Dozol and H. Rouquette, Chem. Commun., 1998, 191. 16 P. R. Danesi, Sep. Sci.Technol., 1983–1985, 19, 857. 17 C. Hill, J. F. Dozol, H. Rouquette, S. Eymard and B. Tournois, J. Membr. Sci., 1996, 114, 73; F. Arnaud-Neu, V. Böhmer, J. F. Dozol, C. Grüttner, R. A. Jakobi, D. Kraft, O. Mauprivez, H. Rouquette, M. J. Schwing-Weill, N. Simon and W. Vogt, J. Chem. Soc., Perkin Trans. 2, 1996, 1175; H. J. Cristau, P. Mouchet, J. F. Dozol and H. Rouquette, Heteroatom Chem., 1995, 6, 533. 18 L. Mátel, F. Macásek, P. Rajec, S. Hermánek and J. Plesek, Polyhedron, 1982, 1, 511. 19 G. M. Sheldrick, SHELXS 86, Program for Crystal Structure Solution, University of Göttingen, 1986. 20 G. M. Sheldrick, SHELXL 97, Program for Crystal Structure Refinement, University of Göttingen, 1997. 21 T. B. Stolwijk, E. J. R. Sudholter and D. N. Reinhoudt, J. Am. Chem. Soc., 1987, 109, 7042. Received 11th May 1998; Paper 8/03495HJ. Chem. Soc., Dalton Trans., 1998, Pages 2849–2854 2853 References 1 M. F. Hawthorne, D. C. Young and P. A. Wegner, J. Am. Chem.Soc., 1965, 87, 1818. 2 M. F. Hawthorne and T. D. Andrews, Chem. Commun., 1965, 443; M. F. Hawthorne, T. D. Andrews, P. M. Garrett, F. P. Olsen, M. Reintjes, F. N. Tebbe, L. F. Warren, P. A. Wegner and D. C. Young, Inorg. Synth., 1967, 10, 91; M. F. Hawthorne, D. C. Young, T. D. Andrews, D. V. Howe, R. L. Pilling, A. D. Pitts, M. Reintjes, L. F. Warren, jun. and P. A. Wegner, J. Am. Chem. Soc., 1968, 90, 879; A. R. Siedle, G. M. Bodner and L. J. Todd, J. Organomet. Chem., 1971, 33, 137; T.E. Paxson, M. K. Kaloustian, G. M. Tom, R. J. Wiersema and M. F. Hawthorne, J. Am. Chem. Soc., 1972, 94, 4882. 3 J. Plesek, Chem. Rev., 1992, 92, 269. 4 K. Shelly, C. B. Knobler and M. F. Hawthorne, New. J. Chem., 1988, 12, 317; M. F. Hawthorne, Pure Appl. Chem., 1991, 63, 327. 5 P. A. Chetcuti, W. Hofherr, A. Liégard, G. Rihs, G. Rist, H. Keller and D. Zech, Organometallics, 1995, 14, 666. 6 C. Madic, J. Bourges and J. F. Dozol, presented at the International Conference on Accelerator-Driven Transmutation Technology and Applications, Las Vegas, 1994. 7 S. D. Reilly, C. F. V. Mason and P. H. Smith, Report LA-11695, Los Alamos National Laboratory, Los Alamos, NM, 1990. 8 C. J. Coetzee and A. J. Basson, Anal. Chim. Acta, 1976, 83, 361. 9 E. W. Baumann, Anal. Chem., 1976, 48, 548; C. J. Coetzee and A. J. Basson, Anal. Chim. Acta, 1977, 92, 399; K. Kimura, H. Tamura and T. Shono, J. Electroanal. Chem., Interfacial Electrochem., 1979, 105, 335; K. Kimura, A. Ishikawa, H. Tamura and T. Shono, J. Chem. Soc., Perkin Trans. 2, 1984, 447. 10 T. L. Heying, J. W. Ager, jun., S. L. Clark, D. J. Mangold, H. L. Goldstein, M. Hillman, R. J. Polak and J. W. Szymanski, Inorg. Chem., 1963, 2, 1089; M. M. Fein, D. Grafstein, J. E. Paustian, J. Bobinski, B. M. Lichstein, N. Mayes, N. N. Schwartz and M. S. Cohen, Inorg. Chem., 1963, 2, 1115; M. M. Fein, J. Bobinski, N. Mayes, N. Schwartz and M. S. Cohen, Inorg. Chem., 1963, 2, 1111. 11 M. F. Hawthorne, D. C. Young, P. M. Garrett, D. A. Owen, S. G. Schwerin and F. N. Tebbe, J. Am. Chem. Soc., 1968, 90, 862. 12 C. Viñas, J. Pedrajas, J. Bertran, F. Teixidor, R. Kivekäs and R. Sillanpää, Inorg. Chem., 1997, 36, 2482. 13 A. J. Welch and A. S. Weller, J. Chem. Soc., Dalton Trans., 1997, 1205; M. A. Fox and K. Wade, Polyhedron, 1997, 16, 2517. 14 M. F. Hawthorne, T. E. Berry and P. A. Wegner, J. Am. Chem. Soc., 1965, 87, 4746. 15 C. Viñas, S. Gomez, J. Bertran, F. Teixidor, J. F. Dozol and H. Rouquette, Chem. Commun., 1998, 191. 16 P. R. Danesi, Sep. Sci. Technol., 1983–1985, 19, 857. 17 C. Hill, J. F. Dozol, H. Rouquette, S. Eymard and B. Tournois, J. Membr. Sci., 1996, 114, 73; F. Arnaud-Neu, V. Böhmer, J. F. Dozol, C. Grüttner, R. A. Jakobi, D. Kraft, O. Mauprivez, H. Rouquette, M. J. Schwing-Weill, N. Simon and W. Vogt, J. Chem. Soc., Perkin Trans. 2, 1996, 1175; H. J. Cristau, P. Mouchet, J. F. Dozol and H. Rouquette, Heteroatom Chem., 1995, 6, 533. 18 L. Mátel, F. Macásek, P. Rajec, S. Hermánek and J. Plesek, Polyhedron, 1982, 1, 511. 19 G. M. Sheldrick, SHELXS 86, Program for Crystal Structure Solution, University of Göttingen, 1986. 20 G. M. Sheldrick, SHELXL 97, Program for Crystal Structure Refinement, University of Göttingen, 1997. 21 T. B. Stolwijk, E. J. R. Sudholter and D. N. Reinhoudt, J. Am. Chem. Soc., 1987, 109, 7042. Received 11th May 1998; Paper 8/03495H

ISSN:1477-9226    

DOI:10.1039/a803495h

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1997, Pages 2853–2854 2853 Preparation and crystal structures of two forms of trans- [CuCl2{N(H)SPh2}2]; an unusual example of square planar/pseudotetrahedral isomerism in a neutral copper(II) complex Paul F. Kelly,* Alexandra M. Z. Slawin and Kevin W. Waring Department of Chemistry, Loughborough University, Loughborough, Leics., UK LE11 3TU At ambient temperatures, in acetonitrile, S,S-diphenylsulfimide reacted with CuCl2 (molar ratio 2 : 1) to give trans-[CuCl2- {N(H)SPh2}2]; depending upon the crystallisation technique this can be isolated as either blue (perfect square-planar geometry) or green (pseudo-tetrahedral) crystals which do not interconvert in the solid state.The ability of some complexes of the late transition metals, in particular copper and nickel, to exhibit variable isomerism between square planar and tetrahedral (or pseudo-tetrahedral) geometries is well known.1 For example, many salts of [CuCl4]22 exhibit thermochromic effects due to such structural changes while a number of nickel(II) complexes (typically those involving phosphine ligands) can exist in the two respective forms (or even, in some cases, exhibit both geometries within the same unit cell).What appears to be a much rarer scenario, however, is isomerism such as this occurring for neutral copper(II) species. Indeed, we have yet to confirm the occurrence of any such example in the literature.We have, however, isolated an example of just such a complex during investigations into the coordination chemistry of S,S-diphenylsulfimide, N(H)SPh2 I. Our interest in the co-ordination chemistry of compound I stems from our general investigations into the interaction of sulfur–nitrogen chain species with transition-metal centres. During such work we have tended to concentrate upon longchain species such as (Me3SiNSNSNSNSiMe3), which can act as a source of a range of S]N ligands via reaction with simple platinum-group complexes.2 While the latter is amongst the longest S]N chain species that may be isolated as a discrete molecule, I is clearly a good example of the shortest such chain.Interest in its chemistry is dominated by its use in organic chemistry as, for example, a source of aziridines.3 In contrast, its co-ordination chemistry is very much underdeveloped, with a recently reported uranium species being the only metal complex so far noted.4 We have been able to show that in fact I readily co-ordinates to a wide range of late-transition-metal units, including CuCl2.† When a solution of compound I (75 mg, 0.38 mmol) in acetonitrile (20 cm3) is slowly added to a solution of CuCl2 (25 mg, 0.19 mmol) in the same solvent (20 cm3), the expected complex [CuCl2{N(H)SPh2}2] 1 forms.If the solution is reasonably concentrated the latter spontaneously precipitates at ambient temperatures; if this precipitate is redissolved by heating, a small amount of diethyl ether added and the solution lagged to promote slow cooling, a good yield of 1 may be obtained as well formed blue crystals (henceforward designated 1a) which † For example [Co{N(H)SPh2}6]21 results from the 6 : 1 reaction of I with CoCl2 while [Pt{N(H)SPh2}Cl(PMe2Ph)2][BF4] can be isolated from the reaction of I with [PtCl2(PMe2Ph)2] and [NH4][BF4]. Details of such reactions will be published in due course.analyse as a straightforward 2 : 1 complex (Found: C, 53.6; H, 3.8; N 5.1.Calc. for C24H22CuCl2N2S2: C, 53.7; H, 4.1; N, 5.2%). X-Ray crystallography reveals these to have a trans arrangement of the ligands with the sulfimides bound, as expected, by their nitrogen atoms (Fig. 1).‡ The overall geometry about the copper is square planar, with no discernable axial intermolecular interactions up to 6 Å from the copper. Such interactions are probably precluded by the fact that the two sets of phenyl rings are arranged roughly perpendicular to the CuCl2N2 plane, providing a steric barrier to any axial close approaches.If a variation upon the above crystallisation procedure is performed whereby the 1a that initially precipitates in acetonitrile is filtered off and the remaining solution treated with diethyl ether and cooled in a freezer, a combination of blue crystals of 1a and green crystalline material 1b is generated. Our initial assumption was that the latter would prove to be the cis analogue of 1a; in fact X-ray crystallography reveals it to again be a trans arrangement but now with a pseudo-tetrahedral geometry about the copper (Fig. 2). The level of distortion from Fig. 1 Crystal structure of complex 1a. Selected bond distances (Å) and angles (8): Cu]N(1) 1.911(8), Cu]Cl(1) 2.271(3), N(1)]S(1) 1.582(9); N(1)]Cu]Cl(1) 87.0(3), N(1)]Cu]N(1*) 180.0, Cl(1)]Cu] Cl(1*) 180.0, Cu]N(1)]S(1) 129.0(5) ‡ Crystal data 5 for complex 1a. C24H22Cl2CuN2S2, M = 537.02, monoclinic, Space group C2/c (no. 15), a = 17.038(2), b = 8.928(5), c = 16.234(2) Å, b = 97.5378, U = 2448(1) Å 3, T = 20 8C, Z = 4 (the molecule possesses a crystallographic centre of symmetry), m(Cu- Ka) = 4.99 mm21, R = 0.058 (R9 = 0.050) for 866 observed reflections [I > 3s(I)]. Crystal data 5 for complex 1b. C24H22Cl2CuN2S2, M = 537.02, monoclinic, space group P21/a (no. 14), a = 11.443(5), b = 16.114(4), c = 14.267(2) Å, b = 109.62(3)8, U = 2478(2) Å 3, T = 20 8C, Z = 4, m(Cu- Ka) = 4.93 mm21, R = 0.053 (R9 = 0.048) for 1748 observed reflections [I > 2s(I)].CCDC reference number 186/645.2854 J. Chem. Soc., Dalton Trans., 1997, Pages 2853–2854 planar can be quantified by the N(2)]Cu]N(1) and Cl(1)]Cu] Cl(2) angles of 157.6 and 153.18 respectively (the corresponding angles both being precisely 1808 in 1a). In other respects, however, there is minimal difference between the two structures; thus the average Cu]N and S]N bond lengths in 1b (1.926 and 1.596 Å respectively) compare well with those in 1a (1.911 and 1.582 Å) while the angles at the nitrogens (i.e.S]N]Cu) are also similar (125.48 in 1b compared to 1298 in 1a). The difference in packing arrangements in the two cases manifests itself in their IR spectra. Thus the n(N]H) stretch in 1b is seen at 3202 cm21, which is some 90 cm21 lower than in 1a, presumably reflecting the fact that the N]H bond is now free to interact with Cu]Cl bonds of neighbouring molecules (the closest such H ? ? ? Cl approach being 2.68 Å in 1b compared to 6.26 Å in 1a; both have, of course, some degree of intramolecular interaction, with H ? ? ? Cl distances of 2.65 and 2.68 Å for 1a and 1b respectively).The two forms of complex 1 do not interconvert in the solid state at room temperature and melt at effectively the same temperature (157 8C) decomposing in the process. As far as Fig. 2 Crystal structure of complex 1b. Selected bond distances (Å) and angles (8): Cu]N(1) 1.932(8), Cu]N(2) 1.919(8), Cu]Cl(1) 2.280(2), Cu]Cl(2) 2.284(2), N(1)]S(1) 1.607(7), N(2)]S(2) 1.584(7); N(1)]Cu]N(2) 157.6(3), Cl(1)]Cu]Cl(2) 153.1(1), N(1)]Cu]Cl(1) 90.5(2), N(1)]Cu]Cl(2) 96.2(2), N(2)]Cu]Cl(1) 93.8(2), N(2)]Cu]Cl(2) 89.9(2), Cu]N(1)]S(1) 122.9(4), Cu]N(2)]S(2) 125.4(4) interconverting in solution goes, we have been able to show that pure crystalline 1a can be redissolved and used to generate crystalline 1b; indeed in such situations it is common to obtain a mixture of intergrown crystals of both forms.As for ascertaining the ability of 1b to generate 1a this has been made harder to prove by the limited amounts of the former at our disposal (crystallisation of 1b only occurs from relatively dilute solutions, precluding the isolation of much more than 5–10 mg from any one batch). We can say, however, that slow evaporation of a solution of 1b does not seem to yield any blue crystals of 1a, and that the UV/VIS spectrum of such a solution lacks a band (lmax 385 nm, emol = 1700 mol21 dm3 cm21) that appears in solutions of 1a [note that an additional band at lmax 235 nm (emol 15 000) is common to both while a broad d–d band centred on 730 nm in 1a envelopes the area covered by a sharper band at 620 nm in solutions of 1b].Both these observations leave open the possibility that 1b could be the most thermodynamically stable of the two forms and that, once formed, it cannot regenerate 1a. We hope that future work will shed more light on this question. In conclusion we can say that the appearance of two such isomeric forms appears to be unprecedented for a neutral copper(II) complex. Given that it is likely to be some feature of I as a ligand that is inducing such effects, it follows that these results suggest that the ligand properties of the whole family of sulfimides deserve far more attention than they have so far been afforded. References 1 Comprehensive Coordination Chemistry, ed. G. Wilkinson, Pergamon Press, Oxford, 1987, vol. 5. 2 P. F. Kelly, A. M. Z. Slawin and A. Soriano-Rama, J. Chem. Soc., Dalton Trans., 1996, 53. 3 T. L. Gilchrist and C. J. Moody, Chem. Rev., 1977, 77, 409. 4 R. E. Cramer, K. A. N. S. Ariyaratne and J. W. Gilje, Z. Anorg. Allg. Chem., 1995, 621, 1856. 5 TEXSAN, Crystal Structure Analysis Package, Molecular Structure Corporation, Houston, TX, 1985, 1992. Received 18th June 1997; Communication 7/04276K

ISSN:1477-9226    

DOI:10.1039/a704276k

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, Pages 2855–2860 2855 Infrared spectroelectrochemistry of [Co3(CPh)(CO)9] in methanol at a platinum electrode Paula A. Brooksby, Noel W. DuVy, A. James McQuillan,*,† Brian H. Robinson and Jim Simpson Department of Chemistry, University of Otago, PO Box 56, Dunedin, New Zealand In situ infrared spectroelectrochemistry [SNIFTIRS (subtractively normalized interfacial FTIR spectroscopy)] has been used to obtain spectra at a platinum electrode of the reduction products of [Co3(CPh)(CO)9] in absolute methanol, in CO saturated methanol, in the presence of a ligand [P(C6H4SO3-m)3]32 (L) and in dichloromethane.The cluster species 49e [Co3(CPh)(CO)9]~2, 50e [Co3(CPh)(CO)9]22 and, tentatively, the 47e [Co3(CPh)(CO)8]2 and 49e [Co3(CPh)(CO)8L]~2 were identified and their interrelationships elucidated. Adsorption of the cluster at the surface may be responsible for the unexpected formation of CO2 upon decomposition of Co(CO)4 2.Electron-transfer processes in metal–metal bonded clusters have been probed primarily using cyclic voltammetry.1 Clusters with strong p-acceptor ligands, such as CO, normally undergo one-electron reduction to the radical anion as the primary process whereas clusters with donor ligands, such as cyclopentadienyl or phosphines, may be oxidised to the radical cation. Control of the redox chemistry is therefore possible by tuning the ligand sphere.2 The most important consequence of radical anion or radical cation formation is activation of the cluster towards nucleophilic substitution.This has allowed a number of eYcient electron-transfer catalysed (ETC) cycles to be devised 2,3 with considerable synthetic utility.3,4 One of the most studied family of systems is that based on the tricobaltcarbon cluster 2 [Co3(CR)(CO)9]. The electrochemical behaviour of these clusters and their phosphine derivatives has been examined5–7 in several non-aqueous solvents, MeCN, acetone, thf and CH2Cl2.These clusters primarily undergo reversible reduction to the 49e radical anion, with the unpaired electron occupying an a2 SOMO centred on the Co3 framework,8 followed by the irreversible formation of a 50e dianion. This dianion rapidly undergoes Co]Co bond cleavage giving the electroactive species Co(CO)4 2. The activated 49e radical anion then participates in rapid ETC ligand exchange reactions, both within the electrode double layer and in bulk solution.It has been suggested 7 that a key step in these reactions is the reversible loss of CO to give a co-ordinatively unsaturated 47e anion which can be further reduced to a 48e dianion (Scheme 1). The kinetic data could also be compatible with Co]Co edge cleavage as the rate determining step. Although the 49e radical anion has been isolated and characterised 9,‡ there are features of Scheme 1 which are still puzzling. We have shown10 that the essential electrochemical processes are unchanged in water or aqueous methanol, including rapid ETC reactions.Electrochemical experiments with [Co3(CR)(CO)9] clusters in non-aqueous solutions at platinum electrodes often show some data variability which appears to indicate adsorption of cluster material. This work sets out to provide a spectroscopic test of the proposed mechanisms and to generate new molecular information about the reaction products. Methanol is similar to water in many respects but much more suitable for infrared studies with generally weaker infrared absorptions and a wider potential † E-Mail: jmcquillan@alkali.otago.ac.nz ‡ The green anion was prepared by sodium reduction of the cluster in thf and, after concentrating the solution, precipitated as the N(PPh3)2 1 salt.It was recrystallised from CH2Cl2 but no crystals suitable for X-ray diVraction work were obtained. window. It has no large absorptions in the carbonyl region and thus provides a good medium to investigate the [Co3(CR)(CO)9] cluster.The IR spectroelectrochemistry of absolute methanol solutions has been studied by Pham et al.11 and Brooksby et al.12 and the reduction and oxidation behaviour of absolute methanol is well documented. It was also of importance to investigate the cluster configuration at the electrode surface using spectroscopic methods which have proved successful in investigations with organic substrates.13 Results and Discussion Cyclic voltammetry of [Co3(CPh)(CO)9] in absolute methanol and CO saturated methanol A cyclic voltammogram between 10.4 and 20.9 V of 1.0 × 1023 mol dm23 [Co3(CPh)(CO)9] in absolute methanol containing 0.1 mol dm23 NaClO4 electrolyte is shown in Fig. 1(i). The negative potential limit is close to that for the onset of dianion formation.5 The primary redox process depicted by the waves at A and B is that associated with the 48e/49e couple [Co3(CPh)- (CO)9]0/2. Peak C is due 5 to the oxidation of Co(CO)4 2, a decomposition product of a radical species.When CO was present there was no voltammetric evidence for Co(CO)4 2 [Fig. 1(ii)]. This observation is similar to that of Hinkelmann et al.7 for [Co3(CMe)(CO)9]. Wave E is associated with methanol oxidation. These results from methanol solutions are similar to the well documented results for [Co3(CPh)(CO)9] and related clusters in aqueous10 and non-aqueous5,6 solvents. Extension of the potential range to 21.2 V for the cyclic voltammograms of 1.0 × 1023 mol dm23 [Co3(CPh)(CO)9] in absolute methanol and in CO saturated methanol solutions showed little change [Fig. 1(iii),(iv)].Reduction of [Co3(CPh)(CO)9]~2 to the 50e dianion is expected in this region but the 21.2 V potential limit is close to that for solvent decomposition. In Fig. 1(iii) an additional peak is observed at 20.94 V on the reverse scan which may arise from the oxidation of this dianion. This peak is again not observed when CO is present.Whether in solution or Scheme 1 [Co3(CR)(CO)9] [Co3(CR)(CO)9]•– [Co3(CR)(CO)9]2– [Co3(CR)(CO)8]– [Co3(CR)(CO)8]2– 48e 49e 50e 47e 48e e e e –CO +CO ? +CO2856 J. Chem. Soc., Dalton Trans., 1998, Pages 2855–2860 adsorbed on the surface CO plays a significant role in the electrochemistry. The electrochemical behaviour of CO dissolved in methanol at a platinum electrode has been investigated.14 A featureless cyclic voltammogram within the solvent limits is observed between 21.0 and 11.1 V (vs.SCE). At the positive potential limit adsorbed CO is oxidised to CO2. At the negative potential limit adsorbed CO appears to desorb from the platinum surface. Carbon monoxide only aVects the potential range where methanol oxidation and reduction occurs. The addition of 1.0 × 1023 mol dm23 [Co3(CPh)(CO)9] to a CO saturated methanol solution gave voltammetric waves for the primary couple unchanged from those already described [Fig. 1(ii)]. A small prepeak, D, appeared on all the initial scans where the platinum electrode was newly polished. This was not observed during the second or subsequent scans. It is not seen in aqueous solution,10 nor if the solution is purged with CO [Fig. 1(ii)]. The process which gives rise to D has been observed at intermittent times during scans conducted in acetone and dichloromethane, and is likely to be a feature that arises in low dielectric solvents. A prepeak, such as wave D, is generally15,16 associated with the strong adsorption of a reduction product, in this case the 49e radical anion.The absence of peak D during subsequent potential cycling, in methanol solutions without added CO, suggests that any adsorbed material remains on the platinum surface within the timescale of the voltammetry. Further adsorption of electroactive material is therefore blocked. SNIFTIRS spectra of [Co3(CPh)(CO)9] in CO saturated methanol Infrared spectroscopic methods have been developing during the past two decades that allow the observation of molecular changes associated with electron transfer processes at elec- Fig. 1 Cyclic voltammograms of 1 × 1023 mol dm23 [Co3(CR)(CO)9] in methanol containing 0.1 mol dm23 NaClO4 electrolyte. Scan rate = 100 mV s21. All scans were initially to more negative potentials from 20.2 V: (i) 10.4 to 20.9 V, N2 saturated; (ii) 10.2 to 20.9 V, CO purged; (iii) 10.4 to 21.2 V, N2 purged; (iv) 10.4 to 21.2 V, CO saturated trodes.Using the SNIFTIRS 17 methodology, absorbance difference spectra that are induced by changes in potential are obtained. Species present at higher concentrations at the sampling potential (Es) give rise to positive IR bands while those present at higher concentrations at the reference potential (Eb) give negative IR bands. The spectrum of the bulk solvent and electrolyte do not change with potential and are not observed. Ideal electrochemical cell behaviour is sacrificed in a SNIFTIRS thin layer cell and large solution resistances often result.The observation of species produced during reduction and oxidation reactions may therefore occur at potentials which are somewhat diVerent to those observed during conventional electrochemical experiments. Distinguishing between adsorbed and solution species is possible using the surface selection rules 17 which predict diVerences between the spectra of adsorbed species for s- and p-polarised light.p-Polarised spectra contain information about both adsorbed and solution species while s-polarised spectra contain information about only solution species. A comparison of the spectra obtained using both types of polarisation will usually allow detection of adsorbed species, provided the absorptions arising from solution species do not obscure the generally weak absorptions of adsorbed species. As shown in the voltammetry, CO saturated methanol solutions containing [Co3(CPh)(CO)9] provide the least complex system to study and will be examined initially.An infrared solution spectrum of [Co3(CPh)(CO)9] in methanol has four n(CO) bands at 2102w (sym. A1 mode), 2055vs cm21 (E), 2039vs (A1), and 2022w (sh) cm21 (E) as expected for a local C3v symmetry.18 The attachment of a large unsymmetrical group on the carbyne or by CO replacement by other ligands is known to lead to a splitting of the 2039 cm21 band and the appearance of weaker bands at lower wavenumbers.18 The SNIFTIRS spectra between 20.6 and 20.9 V of 1.0 × 1023 mol dm23 [Co3(CPh)(CO)9] in a CO saturated methanol solution containing 0.1 mol dm23 NaClO4 electrolyte are shown in Fig. 2. All spectra shown were recorded using p-polarised light. Spectra were also obtained using s-polarised light to test for adsorbed species but no diVerences were observed between the spectra of the cluster species with diVerent polarisations. The SNIFTIRS spectra recorded between 20.2 (Eb) and 20.6 V during the forward and reverse potential steps showed no absorption changes in the carbonyl region and have been omitted for clarity.As the electrode potential is stepped from 20.6 to 20.9 V, [Co3(CPh)(CO)9] is reduced to the radical anion [Co3(CPh)- (CO)9]~2 in the thin solution layer. The negative absorption peaks are due to the loss of [Co3(CPh)(CO)9], whilst the positive absorption peaks at lower wavenumber are due to [Co3- (CPh)(CO)9]~2. The peaks at 1988 and 1977 cm21 are assigned to the strong E modes of the 49e [Co3(CPh)(CO)9]~2, the weaker A1 mode is seen as a broad ill defined feature at ca. 2010 cm21. For comparison, the n(CO) bands of [Co3(CPh)(CO)9]~2 occur at 2040w, 1989s, 1973s and 1945vw cm21 in thf or CH2Cl2 solutions and similar to those of the solid [isolated as its N(PPh3)2 1 salt].9 The highest wavenumber weak absorption of [Co3(CPh)(CO)9]~2 is not evident due to overlap with other more intense absorptions. A shift of 60–70 cm21 from the 48e to 49e species is compatible with a large increase in charge associated with occupancy of the antibonding a2 SOMO.This shift is significantly larger than that of 30 cm21 observed when a CO is replaced by a weaker p-acceptor ligand. Of interest is the confirmation from the IR spectra that radical anion formation is reversible in accordance with the CV results shown in Fig. 1(ii). No decomposition products such as Co(CO)4 2 were observed but there is one weak feature at 1950 cm21 which has not been assigned.This absorption may be due to a dianion but since its intensity correlates with the other [Co3(CPh)(CO)9]~2 peaks it is assigned to the E mode of this anion.18J. Chem. Soc., Dalton Trans., 1998, Pages 2855–2860 2857 The SNIFTIRS spectra for the extended potential range where the dianion is expected to be observed are shown in Fig. 3. As the electrode potential is stepped from 20.4 to 21.0 V, [Co3(CPh)(CO)9] is reduced to [Co3(CPh)(CO)9]~2 as described above.When the potential is stepped further from Fig. 2 The SNIFTIRS spectra of 1 × 1023 mol dm23 [Co3(CPh)(CO)9] in methanol saturated with CO and containing 0.1 mol dm23 NaClO4 electrolyte. Negative potential steps starting at Eb = 20.2 V followed by positive potential steps from 20.9 V Fig. 3 The SNIFTIRS spectra of 1 × 1023 mol dm23 [Co3(CPh)(CO)9] in methanol saturated with CO and containing 0.1 mol dm23 NaClO4 electrolyte. Negative potential steps starting at Eb = 0.0 V followed by positive potential steps from 21.2 V 21.0 to 21.2 V there is a decrease in the intensity of the n(CO) peaks for [Co3(CPh)(CO)9]~2 and at the same time two additional peaks emerge at 1931 and 1904 cm21.Stepping the potential back to 20.2 V reverses this sequence of events except that the broad feature at 1904 cm21 remains. On this evidence the 1931 cm21 band is assigned to the most intense n(CO) E mode of the 50e [Co3(CPh)(CO)9]22 species.The shift in energy of ca. 60 cm21 is consistent with the addition of a further electron to the a2 SOMO and is of the order of that encountered for the one-electron reduction of the parent. The species giving rise to the broad peak at 1904 cm21 remained unoxidised until 0.0 V during the positive potential steps, indicating some irreversible decomposition of the cluster at high negative potentials. In methanol solution Co(CO)4 2 has a broad band at 1904 cm21 and this assignment was previously confirmed9 from the IR spectrum in methanol of the N(PPh3)2 1 salt of this anion.Oxidation of Co(CO)4 2 during a SNIFTIRS experiment gave a weak and broad absorption centred at ca. 2030 cm21. The most likely candidate for assigning this peak is the most intense E mode of [Co2(CO)8].19 Absorptions due to solution CO2 at 2339 cm21 and adsorbed CO at about 2070 cm21 were also present. A bipolar peak seen at ca. 2060 cm21 in Fig. 3 during the initial scan, and the singular peak around 2075 cm21 on the reverse scan, was confirmed by polarisation studies as due to CO adsorbed onto the platinum surface.14 The peak at 2339 cm21 is due to solution CO2.14 In all of the SNIFTIRS spectra the CO2 signal emerges as the oxidation of Co(CO)4 2 is completed.The origin of this CO2 signal appears to be related to the oxidation of a decomposition product but this remains to be established. SNIFTIRS spectra of [Co3(CPh)(CO)9] in absolute methanol The SNIFTIRS spectra between 20.3 and 21.2 V of 1.0 × 1023 mol dm23 [Co3(CPh)(CO)9] in absolute methanol are shown in Figs. 4 and 5 (20.2 to 0.9 V and 0.0 to 21.2 V respectively). Fig. 4 The SNIFTIRS spectra of 1 × 1023 mol dm23 [Co3(CPh)(CO)9] in methanol containing 0.1 mol dm23 NaClO4 electrolyte. Negative potential steps starting at Eb = 20.2 V followed by positive potential steps from 20.9 V2858 J. Chem. Soc., Dalton Trans., 1998, Pages 2855–2860 These spectra are essentially the same as those in Figs. 2 and 3 from 0.0 V until Es = 20.8 V. There was no observable diVerence between the spectra obtained in either p- or s-polarised light. The SNIFTIRS spectra for the reduction of [Co3(CPh)- (CO)9] (Fig. 4) produced evidence of cluster decomposition at 20.9 V by the appearance of an infrared peak for Co(CO)4 2. This is in accordance with the CV results [Fig. 1(i)]. There is also evidence for minor amounts of [Co3(CPh)(CO)9]22 (1931 cm21) being produced.During the positive potential steps the oxidation of [Co3(CPh)(CO)9]~2 to [Co3(CPh)(CO)9] is observed. However, complete recovery of the cluster compound is not achieved when the potential has returned to 20.3 V, with the infrared absorptions of the carbonyl peaks for [Co3(CPh)- (CO)9] showing a net loss. This is due to [Co3(CPh)(CO)9]~2 decomposition but some diVusion of electroactive material out of the infrared optical path may also contribute.17 As Eb is approached during the reverse potential steps, two residual peaks at 1992 and 1973 cm21 are observed and will be discussed later in this paper. These peaks are not present in the SNIFTIRS spectra for the CO saturated methanol system (Figs. 2 and 3) and are more clearly observed in Fig. 5 when more negative potentials are applied. The SNIFTIRS spectra for the extended negative potential region are shown in Fig. 5. These are significantly diVerent at 20.8 V, once reduction of the cluster has begun, from those observed when CO has been added (Fig. 3). There are at least three diVerent species present at 21.0 V. These are [Co3(CPh)- (CO)9]22 (1931 cm21), Co(CO)4 2 (1904 cm21) and a species (Z) which has two strong absorptions at 1992 and 1973 cm21. The intensity of the 1904 cm21 band (Figs. 3 and 5) indicates that the majority of the decomposition to Co(CO)4 2 takes place via the 50e dianion rather than the 49e anion. To investigate the influence of solvent on the reduction products of the cluster the SNIFTIRS spectra were run in dichloromethane (Fig. 6). Although the bands are not as clearly resolved there is a close correlation with the spectra in methanol solution. The n(CO) band wavenumbers of the Fig. 5 The SNIFTIRS spectra of 1 × 1023 mol dm23 [Co3(CPh)(CO)9] in methanol containing 0.1 mol dm23 NaClO4 electrolyte. Negative potential steps starting at Eb = 0.0 V followed by positive potential steps from 21.2 V predominant reduction product, [Co3(CPh)(CO)]~2, are identical.However, there is a marked solvent shift to lower energy of ca. 10 cm21 for n(CO) of [Co3(CPh)(CO)9]22 and of Co(CO)4 2. An alternative assignment of the 1922 cm21 band to an octacarbonyl species is unlikely given its behaviour with potential. Such solvent shifts are well known20 for Co(CO)4 2. What is surprising is the appearance of this decomposition species at 20.7 V before the 49e species is observed in the SNIFTIRS spectra. This suggests that another cluster species, unstable in dichloromethane, is being formed at a lower potential.A clue to this species is provided by a careful examination of Figs. 4 and 5. The two residual peaks at 1992 and 1973 cm21 can be seen in Fig. 4 as Eb is approached during the reverse potential steps. These peaks are not present in the SNIFTIRS spectra for CO saturated methanol solutions (Fig. 2). There is also a change in the intensity profile of the principal product peaks in the potential sequence 21.2 æÆ 20.2 V in Fig. 5. Species Z persists at potentials positive of the [Co3(CPh)(CO)9]0/2 couple potential. The wavenumbers of the n(CO) peaks for Z, as well as the band profile, are similar to those of the 49e [Co3(CPh)(CO)9]~2 species and suggest that Z must be an anion with a closely related structure. The obvious candidate is the 47e [Co3- (CPh)(CO)8]2 species analogous to the proposed 7 labile species, [Co3(CMe)(CO)8]2, in the redox cycle of [Co3(CMe)- (CO)9].Oxidation of Z led to the decomposition product, Co(CO)4 2, as is seen in Fig. 5. Clearly, the co-ordinatively saturated [Co3(CPh)(CO)9]~2 will be stabilised in the presence of CO and this is observed. Hinkelmann et al.7 have suggested that this also accounts for the chemical reversibility of the 48e/49e couple at high concentrations of [Co3(CR)(CO)9]. Electrochemical evidence for the co-ordinatively unsaturated species is inferred from the data obtained from 1025 mol dm23 solutions.The SNIFTIRS spectra for 5 × 1025 mol dm23 [Co3(CPh)(CO)9] in methanol did not allow Z and [Co3(CPh)(CO)9]~2 to be distinguished. Fig. 6 The SNIFTIRS spectra of 1 × 1023 mol dm23 [Co3(CPh)(CO)9] in dichloromethane containing 0.1 mol dm23 NBu4ClO4 electrolyte. Negative potential steps starting at Eb = 20.2 V followed by positive potential steps from 21.2 VJ. Chem. Soc., Dalton Trans., 1998, Pages 2855–2860 2859 SNIFTIRS spectra of [Co3(CPh)(CO)9] in the presence of a phosphine ligand Phosphines participate in very eYcient electron transfer catalysed reactions where the 49e [Co3(CPh)(CO)9]~2 is the initiating species.2 The reduction (or oxidation) of electroactive species in a thin layer arrangement is essentially complete within a very short period of time, of the order of seconds.Therefore a catalytic reaction, once initiated, will proceed quite rapidly, but not necessarily go to completion depending upon the limiting reagent. Scheme 2 is representative of an ETC reaction for [Co3(CPh)(CO)9] and L based upon the scenario put forward by Hinkelmann et al.7 Fig. 7 contains the SNIFTIRS spectra of 1 × 1023 mol dm23 [Co3(CPh)(CO)9] and 1 × 1023 mol dm23 Na3[P(C6H4SO3-m)3] (L) in methanol with 0.1 mol dm23 NaClO4 electrolyte. It is clear from the IR spectra that the moment [Co3(CPh)(CO)9] begins to be reduced (at 20.50 V) the substituted cluster, [Co3(CPh)- (CO)8L], is formed. The latter has n(CO) peaks at 2078, 2035, 2024 and 2013 cm21.From 20.6 to 20.8 V the IR spectra show a significant amount of [Co3(CPh)(CO)9]~2 is present, whilst no further increase in the n(CO) peaks for [Co3(CPh)(CO)8L] is seen. This result is expected as there are two competing pathways in which [Co3(CPh)(CO)9] is being removed (I and IV of Scheme 2). In the thin layer there is a limited supply of [Co3(CPh)(CO)9] and in this case the electrochemical reduction of the cluster dominates. Once [Co3(CPh)(CO)9] has been depleted from the thin layer no further catalysis past step III can occur.As the potential becomes more negative, the IR spectra predominantly reflect the behaviour that is observed in the absence of L. A notable diVerence is the increase in the relative intensity of the IR peak (at 1937 cm21) which has been attributed to [Co3(CPh)(CO)9]22 and the reduction of [Co3(CPh)(CO)8L]. The IR bands for [Co3(CPh)(CO)8L]~2 are expected to be found in much the same wavenumber region as that of [Co3(CPh)(CO)8]2 and this would make identification of these bands diYcult.However, [Co3(CPh)(CO)8L]~2 was shown3 to be unstable with respect to decomposition to [Co3(CPh)(CO)9] and, as already observed, reaction II is not significantly competitive. Therefore, the predominant pathway of reduction at Es > 20.8 V is likely to be reaction V. The SNIFTIRS spectra that were run in the presence of a threefold excess of L had a very small peak at ca. 1965 cm21 which may be related to [Co3(CPh)(CO)8L]~2.The IR spectra resulting from the positive potential steps are similar to those observed in solutions without L (or CO). Once [Co3(CPh)(CO)9] has been produced in the thin layer, from the oxidation of [Co3(CPh)(CO)9]~2, then the ETC reaction can recommence. At 20.9 V (positive potential steps) the substituted cluster, [Co3(CPh)(CO)8L], is reformed and is not oxidised further within the potential limits explored here. Conclusion The SNIFTIRS results have provided, for the first time, in situ infrared spectra of the species produced during the electro- Scheme 2 [Co3(CPh)(CO)9] [Co3(CPh)(CO)9]•– [Co3(CPh)(CO)9]2– [Co3(CPh)(CO)8L]– e e I V Es >–0.8 V [Co3(CPh)(CO)8]– –CO +L II III IV [Co3(CPh)(CO)8L] [Co3(CPh)(CO)9] L chemical reduction of [Co3(CPh)(CO)9] in methanol under N2, CO and in the presence of a phosphine ligand. From the commonality of electrochemical behaviour for generic [Co3(CR)- (CO)9] clusters a similar reaction sequence can be expected for other capped clusters of this type.In general, these results in thin layers concur with the interpretation by Hinkelmann et al.7 of the solution electrochemistry for [Co3(CMe)(CO)9]. There is clear evidence for a co-ordinatively unsaturated species (Z) which is stable over a considerable potential range and the oxidation of which leads to [Co3(CPh)(CO)9]. Reduction of [Co3(CPh)(CO)9] gave the species identified as 49e [Co3(CPh)- (CO)9]~2, 50e [Co3(CPh)(CO)9]22 and tentatively 47e [Co3- (CPh)(CO)8]2.The interrelationships between these species at various electrode potentials, and in the presence of CO, were able to be better resolved using the SNIFTIRS technique. Decomposition to Co(CO)4 2 occurred from both the dianion and the co-ordinatively unsaturated species, but not necessarily from the primary reduction product, [Co3(CPh)(CO)9]~2. The SNIFTIRS spectra for the reduction of [Co3(CPh)- (CO)9] in the presence of L clearly show the rapid ETC formation of the neutral product, [Co3(CPh)(CO)8L].The ETC cycle was quickly suppressed in the thin layer cell due to the depletion of [Co3(CPh)(CO)9]. Reduction of the [Co3(CPh)(CO)8L] species was evident in product IR peaks but the product species was not able to be identified. Since the substituted [Co3(CPh)- (CO)8L] species was able to be identified it should be possible in further studies to investigate the competitive co-ordination that occurs between a chelating and non-chelating phosphine ligand.Experimental The compound [Co3(CPh)(CO)9] was prepared by the literature Fig. 7 The SNIFTIRS spectra of 1 × 1023 mol dm23 [Co3(CPh)(CO)9] and 1 × 1023 mol dm23 Na3[P(C6H4SO3-m)3] in methanol containing 0.1 mol dm23 NaClO4 electrolyte. Negative potential steps starting at Eb = 20.2 V followed by positive potential steps from 21.1 V2860 J. Chem. Soc., Dalton Trans., 1998, Pages 2855–2860 method and doubly crystallised from hexane.21 All manipulations were carried out in an inert atmosphere. Carbon monoxide was used directly from a steel cylinder.As CO from this source has been shown22 to contain [Fe(CO)5] any iron carbonyl impurity was removed by bubbling the gas through a methanol scrubbing solution containing PPh3. A comparison of the results obtained during the reduction of [Co3(CPh)(CO)9], using CO directly from the steel cylinder or purified as above, showed no observable diVerence.Spectroscopy and electrochemistry Measurements were made at 20 8C with purified solvents. Acetone was removed from the reagent-grade methanol by fractional distillation from iodoform and dried by fraction distillation from Mg/I2 then standing over activated 4 Å molecular sieves. The water content was less than 0.01 vol. % (typically between 0.008 and 0.003 vol. %) water as determined by the Karl Fischer titration using a biamperometric end-point detection method.23 Dichloromethane was washed with aqueous alkali, distilled, dried over activated 4 Å molecular sieves 24 and stored in the dark under nitrogen. Electrolyte solutions were freshly prepared prior to each experiment from anhydrous NaClO4 or tetrabutylammonium perchlorate.All potentials are with respect to an aqueous KCl saturated calomel electrode (SCE). Electrode potential control, electrochemical data and SNIFTIRS were obtained using an EG & G Princeton Applied model 363 potentiostat coupled to a HB Thompson & Associates model DRG16 ramp generator for cyclic voltammetry.Working potentials were monitored with a Thandar TM351 digital multimeter and the I/A vs. E/V plots recorded on a Houston X-Y recorder. Cyclic voltammograms were conducted in a standard three electrode cell comprising platinum disc working and platinum wire secondary electrodes with an aqueous KCl saturated calomel electrode. Solutions were purged with oxygen-free nitrogen before measurements.The polished platinum working electrode and other components of the electrochemical cell were similar to those previously described.14 The platinum working electrodes were polished with 0.015 mm Al2O3 before being subjected to an electrochemical cleaning treatment which consisted of 30 s of potential stepping between 4.0 and 24.0 V at 2 Hz in 0.5 mol dm23 aqueous H2SO4 solution. Such a treatment gave well resolved adsorbed hydrogen peaks in a cyclic voltammogram recorded in the 0.5 mol dm23 H2SO4 solution.The electrode was then successively rinsed with water, methanol and a portion of the cell solution before being placed in the spectroelectrochemical cell without allowing the electrode surface to dry at any stage of the rinsing. The infrared spectra were obtained with a Digilab FTS60V evacuable optical bench spectrometer equipped with a mercury cadmium telluride detector and coupled to a thin layer electrochemical cell via a CaF2 608 dove prism.A description of the SNIFTIRS cell and evacuable optical bench will be given elsewhere. 12 The SNIFTIRS spectra were obtained with a solution layer of about 5 mm between the electrode and the CaF2 prism. The lower limit of the wavenumber range was determined by the CaF2 absorption. All spectra were recorded at 4 cm21 resolution with an acquisition time of 60 s at each potential after 30 s was allowed for steady state conditions to be achieved.The noise level over most of the spectral range was less than 0.0002 absorbance. Acknowledgements We thank the Research Committee of the University of Otago for financial support. P. A. B. acknowledges Ph.D. funding from the University of Otago. References 1 N. G. Connelly and W. Geiger, Adv. Organomet. Chem., 1985, 24, 87. 2 B. H. Robinson and J. Simpson, Paramagnetic Organometallic Species in Activation/Selectivity Catalysis, ed. M. Chanon, Kluwer, Dordrecht, 1989, p. 357. 3 C. M. Arewgoda, B. H. Robinson and J. Simpson, J. Chem. Soc., Chem. Commun., 1982, 284; G. J. Bezems, P. H. Rieger and S. J. Visco, J. Chem. Soc., Chem. Commun., 1981, 265; C. M. Arewgoda, B. H. Robinson and J. Simpson, J. Am. Chem. Soc., 1983, 105, 1893; A. J. Downard, B. H. Robinson and J. Simpson, Organometallics, 1986, 5, 1122. 4 M. I. Bruce, D. C. Kehoe, J. G. Matisons, B. K. Nicholson, P. H. Rieger and M. L. Williams, J. Chem. Soc., Chem. Commun., 1982, 442; A. Dachen, C.Mahe and H. Patin, J. Chem. Soc., Chem. Commun., 1982, 243; R. G. Cunninghame, A. J. Downard, L. R. Hanton, S. D. Jensen, B. H. Robinson and J. Simpson, Organometallics, 1984, 3, 180; R. G. Cunninghame, L. R. Hanton, S. D. Jensen, B. H. Robinson and J. Simpson, Organometallics, 1987, 6, 1470; S. D. Jensen, B. H. Robinson and J. Simpson, Organometallics, 1987, 6, 1479. 5 B. M. Peake, B. H. Robinson, J. Simpson and D. J. Watson, Inorg. Chem., 1977, 16, 410; A. M. Bond, U. Honrath, P.N. T. Lindsay, B. M. Peake, B. H. Robinson, J. Simpson and H. Vahrenkamp, Organometallics, 1984, 3, 413; A. J. Downard, B. H. Robinson and J. Simpson, Organometallics, 1986, 5, 1132. 6 A. M. Bond, B. M. Peake, B. H. Robinson, J. Simpson and D. J. Watson, Inorg. Chem., 1977, 16, 2199. 7 K. Hinkelmann, J. Heinze, H.-T. Schacht, J. S. Field and H. Vahrenkamp, J. Am. Chem. Soc., 1989, 111, 5078. 8 B. M. Peake, P. H. Rieger, B. H. Robinson and J. Simpson, Inorg. Chem., 1979, 18, 1000; 1981, 20, 2540; S. B.Colbran, L. R. Hanton, B. H. Robinson, W. T. Robinson and J. Simpson, J. Organomet. Chem., 1987, 330, 415. 9 P. N. T. Lindsay, Ph.D. Thesis, University of Otago, 1982. 10 N. W. DuVy, B. H. Robinson, K. Robinson and J. Simpson, J. Chem. Soc., Dalton Trans., 1994, 2821. 11 M.-C. Pham, F. Adami, P.-C. Lacaye, J.-P. Doucet and J.-E. Dubois, J. Electroanal. Chem. Interfacial Electrochem., 1986, 201, 413. 12 J. G. Love, P. A. Brooksby and A. J. McQuillan, unpublished work. 13 P. A. Brooksby, C. A. Hunter, A. J. McQuillan, D. H. Purvis, A. E. Rowan, R. J. Shannon and R. Walsh, Angew. Chem., Int. Ed. Engl., 1994, 33, 2489; A. Babaei and A. J. McQuillan, J. Phys. Chem., 1997, 101, 7443. 14 J. G. Love and A. J. McQuillan, J. Electroanal. Chem. Interfacial Electrochem., 1989, 274, 263. 15 R. H. Wopschall and I. Shain, Anal. Chem., 1967, 39, 1514. 16 A. J. Bard and L. R. Faulkner, Electrochemical Methods, Wiley, New York, 1980. 17 Spectroelectrochemistry: Theory and Practice, ed. R. J. Gale, Plenum, New York, 1988; K. Ashley and S. Pons, Chem. Rev., 1988, 88, 673; T. Iwasita and F. C. Nart, Adv. Electrochem. Sci. Eng., 1995, 4, 126. 18 G. Bor, Proc. Symp. Coord. Chem. Tihany, 1964, 361. 19 P. S. Braterman, Metal Carbonyl Spectra, Academic Press, London, 1975. 20 W. F. Edgell and S. Chanjamai, J. Am. Chem. Soc., 1980, 102, 147 and refs. therein. 21 W. T. Dent, L. A. Duncanson, R. G. Guy, H. W. B. Reed and B. L. Shaw, Proc. Chem. Soc., 1961, 169. 22 A. Cuesta and C. Gutierrez, J. Electroanal. Chem. Interfacial Electrochem., 1995, 395, 331. 23 Standard Test Method for Water in Volatile Solvents (Fischer Reagent Titration Method), The American Society for Testing and Materials, Annual Book of ASTM Standards, 1982, Part 29, D1364-78, pp. 175–178. 24 A. Weissberger, in Techniques in Chemistry, eds. J. A. Riddick and W. B. Bunger, Wiley, New York, 3rd edn., 1970, vol. 2. Received 13th May 1998; Paper 8/03596B

ISSN:1477-9226    

DOI:10.1039/a803596b

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON COMMUNICATION J. Chem. Soc., Dalton Trans., 1997, Pages 2857–2859 2857 Ultrafast reductive elimination of hydrogen from a metal carbonyl dihydride complex; a study by time-resolved IR and visible spectroscopy † Mirco Colombo,a Michael W. George,b John N. Moore,a David I. Pattison,a Robin N. Perutz,*,a Ian G. Virrels b and Tian-Qing Ye a a Department of Chemistry, University of York, York, UK YO1 5DD b Department of Chemistry, University of Nottingham, Nottingham, UK NG7 2RD Laser flash photolysis of [Ru(PPh3)3(CO)(H)2] 1 in benzene solution yielded transient [Ru(PPh3)3(CO)] which was observed by both microsecond UV/VIS and IR spectroscopy [lmax = 380 nm, n(CO) = 1845 cm21] and reacted with H2 to reform 1 [k2 = (8.4 ± 0.4) × 107 dm3 mol21 s21]; photolysis of 1 with an ultrafast laser equipped with IR detection demonstrates that reductive elimination of H2 and formation of [Ru(PPh3)3(CO)] is complete within 6 ps.Reductive elimination of hydrogen and the reverse reaction, oxidative addition, occupy fundamental positions in transitionmetal chemistry.When initiated thermally, such reactions play a crucial role in catalysis. However, it is often the photoinduced reactions which offer a gateway to mechanistic studies, since numerous metal dihydride complexes undergo reductive elimination of hydrogen on ultraviolet irradiation.1–5 When placed under a hydrogen atmosphere, the photoproduct may react back with hydrogen to regenerate the precursor [equation (1)].3–5 We have used flash photolysis with UV/VIS detection to [M]H2 hn k2 [M] 1 H2 (1) observe the primary photoproducts, [M], and to determine the kinetics of the back reaction with hydrogen, notably with [Ru(drpe)2] (drpe = R2PCH2CH2PR2, dmpe when R = Me, depe when R = Et, etc.).3–5 Such measurements are made with typical ‘nanosecond apparatus’ with an instrumental risetime of ca. 50 ns. It is invariably found that formation of the 16-electron transient is complete within the risetime.The early steps of the photochemical reaction, including formation of excited state(s), M]H bond breaking, H]H bond making and rearrangement of the MP4 skeleton to its new equilibrium geometry must occur within this time. Ultrafast spectroscopy (time-scale 10213–1029 s) offers the opportunity of studying the early stages of reaction but is less straightforward and requires very different equipment. In our first investigation of reductive elimination on the picosecond time-scale, we irradiated [Ru(dmpe)2H2] with an ultrafast laser and followed the transient UV/VIS absorption over time.6 We obtained evidence that reductive elimination was already complete ca. 16 ps after the laser pulse, but these experiments were confined to a few probe wavelengths and were limited by the lack of conclusive evidence of oxidation states from UV/VIS spectroscopy. In this communication, we report ultrafast experiments on a † Non-SI unit employed: atm = 101 325 Pa.related metal carbonyl dihydride complex in which we have followed the reaction from excitation to 2000 ps after the laser pulse by time-resolved infrared (TRIR) spectroscopy using the CO stretching vibration as a reporter.7 These experiments form the first application of ultrafast IR spectroscopy to study reductive elimination, and provide conclusive evidence that reductive elimination is complete within 6 ps. Our precursor, [Ru(PPh3)3(CO)(H)2] 1, has been shown to lose H2 upon photolysis in steady-state experiments.8 It is of particular interest because it catalyses insertion of alkenes into C]H bonds at unsaturated carbon (alkene or aromatic) in a bposition relative to a carbonyl group.9–11 In one of the putative reaction mechanisms, the thermal reaction is initiated by hydrogenation of the alkene to form [Ru(PPh3)3(CO)], the same intermediate as would be expected to form upon photolysis.9 The white precursor 1 is soluble in benzene and exhibits a shoulder at 325 nm (e ª 9000 dm3 mol21 cm21) in its UV/VIS absorption spectrum and a n(CO) band at 1939 cm21.On laser flash photolysis‡ (instrumental risetime ca. 50 ns), a conspicuous transient is observed with lmax ª 380 nm [Fig. 1(a)]. The transient decays with pseudo-first-order kinetics (kobs = 3 × 103 s21) under an argon atmosphere. The rate constant increases linearly with concentration of dissolved hydrogen [Fig. 1(b)]. The slope of this plot yields the second-order rate constant for reaction of the transient with H2 in benzene of (8.4 ± 0.4) × 107 dm3 mol21 s21.Transient absorption experiments with 1 dissolved under 1 atm H2 in tetrahydrofuran (thf) yield a comparable value of kobs (2.1 × 105 s21) to the experiments with benzene as solvent (2.5 × 105 s21).‡ Similar experiments were performed with 1 dissolved in C6D6 under H2, but with IR detection.§ A spectrum measured 1 ms after the laser flash revealed loss of precursor at 1940 cm21 and ‡ [1] typically ca. 1024 mol dm23 in C6H6, 10 mm pathlength, laser at 308 nm, pulse energy at sample ca. 5 mJ. Samples were degassed by freeze–pump–thaw methods and H2–Ar gas mixtures admitted with a total pressure of 1 atm. One measurement was made at higher pressure of H2, viz. 3.2 atm. No significant change in the rate constant under 1 atm H2 was found when C6H6 solvent was replaced by C6D6, nor when the concentration of 1 was increased to 5 × 1024 and 1 × 1023 mol dm23 (2 and 1 mm pathlengths, respectively).The concentration of dissolved hydrogen was taken as 2.85 × 1023 mol dm23 atm21.12a The solubility of H2 in thf has not been documented, but is ca. 6 × 1023 mol dm23 atm21 in Et2O.12b The value derived for the rate constant for reaction of the transient with H2 in thf is ca. 3.6 × 107 dm3 mol21 s21. § Pump laser at 355 or 308 nm, detection with diode IR laser, sample 2 × 1023 or 3 × 1023 mol dm23 dissolved in C6D6 (for IR transparency) under 1 atm hydrogen and flowed through an IR cell (CaF2 windows, 1 mm pathlength) within a closed circulating system (glass with PTFE connections and stainless steel micropump).Notice that the kinetics were sometimes monitored away from the band maxima, in order to use the optimum laser output. The instrument was set up to maximise the signal-to-noise ratio, such that the risetime was ca. 500 ns.2858 J. Chem. Soc., Dalton Trans., 1997, Pages 2857–2859 formation of product bands with maxima at 1845 and 1974 cm21 [Fig. 2(a)]. The kinetics of the first product band were monitored at 1840 cm21; the band rose within the risetime of the instrument and decayed to about 30% of its initial absorbance with first-order kinetics with a rate constant, kobs, of 2.0 × 105 s21 [Fig. 2(b)]. The same value of kobs was obtained at two concentrations of 1 and is consistent with the kinetics from the UV experiments. The second transient band at 1973 cm21 showed a significant risetime of ca. 5 ms with rate constants for growth dependent on [1] and did not show any subsequent decay over 50 ms.¶ The bleach signal at 1940 cm21 recovered partially (to ca. 80% of initial change in absorbance). The transient species with lmax at 380 nm and n(CO) at 1845 cm21 is assigned unequivocally as [Ru(PPh3)3(CO)] on the basis of its rapid rise, the kinetics of its reaction with H2, the partial recovery of starting material and the position of the IR band (Scheme 1).The very large shift of ca. 100 cm21 in n(CO) from RuII in 1 to Ru0 in [Ru(PPh3)3(CO)] is consistent with shifts recently determined for related ruthenium complexes in matrices. 13,14 The lack of kinetic stabilisation by thf provides no support for solvent co-ordination to [Ru(PPh3)3(CO)]. The coordination geometry at ruthenium in [Ru(PPh3)3(CO)] cannot be determined from these experiments. In contrast, the relative intensity of the n(CO) bands provides bond angle information for [Ru(CO)2(dmpe)].14 The long-lived species with n(CO) at 1973 cm21 must be a secondary dinuclear product since it rose relatively slowly with kinetics dependent on [1].The photolysis of 1 has also been monitored by TRIR spec- Fig. 1 (a) Transient absorption, monitored at 410 nm, following laser flash photolysis (lex = 308 nm) of 1 dissolved in benzene under 1 atm H2; (d) experimental points, (—) exponential fit. (b) Plot of the variation of kobs vs.concentration of dissolved hydrogen. The slope yields the second-order rate constant for reaction of [Ru(PPh3)3(CO)] with hydrogen to reform 1 ¶ The observed rate constants for the growth of the 1973 cm21 band were 6.8 × 105 s21 and 9.3 × 105 s21 at [1] = 2 × 1023 and 3 × 1023 mol dm23, respectively. The kinetics of the bleach at 1940 cm21 could be fitted satisfactorily to a model comprising a finite rise and a competing decay component corresponding to the rate constants of the two product bands.troscopy on the picosecond time-scale.|| An IR spectrum measured 25 ps after the laser pulse revealed two features: a negative peak at 1940 ± 3 cm21 corresponding to the loss of the precursor and a positive peak at 1843 ± 3 cm21 corresponding to formation of [Ru(PPh3)3(CO)]. No other bands were observed between 1800 and 2050 cm21. A kinetic trace measured at 1843 cm21 showed a very fast rise and decay within the instrumental response function of ca. 6 ps. After this initial period, the signal maintained its amplitude over 2 ns [Fig. 3(a)]. The very fast decay corresponds to the solvent response, since a positive signal with these kinetics was observed at all wavenumbers for the solvent alone. The long-lived signal arises from [Ru(PPh3)3(CO)]; curve fitting shows that this signal appeared within ca. 6 ps and remained constant [Fig. 3(a)]. A kinetic trace measured at 1941 cm21 showed that the bleaching signal of 1 also rose within 6 ps and remained steady for the succeeding 2 ns [Fig. 3(b)]; again, a signal was observed which decayed with the instrument response function. Fig. 2 Microsecond TRIR spectrum recorded 1 ms after laser flash photolysis (lex = 355 nm) of 1 dissolved in C6D6 under 1 atm H2. The negative feature is due to bleach of 1, the positive features are due to photoproducts. (b) Microsecond kinetics of the lower wavenumber product band monitored at 1840 cm21 (lex = 308 nm) Scheme 1 Photochemical reactions of complex 1 PPh3 Ru PPh3 Ph3P H OC H 1940 cm–1 [Ru(PPh3)3(CO)] + H2 1845 cm–1 hn k2 = 8.4 x 107 dm3 mol–1 s–1 || Ultrafast setup;7 pump pulses at 304 nm of 4 ps full width at half maximum (6 ps autocorrelation time) duration and 1.05 kHz repetition rate, pulse energy ca. 1–2 mJ. IR absorption was measured with a CO laser (1800–1960 cm21 at 4 cm21 intervals) or with a diode laser (1965– 2050 cm21) via a detection system employing upconversion. The solutions were handled in the same flow system as for the microsecond experiments, but with a faster flow rate.Complex 1 (ca. 1023 mol dm23) dissolved in C6D6 under 1 atm H2. IR cell of pathlength 1 mm giving an absorbance ca. 1 at the pump wavelength and ca. 0.3 at 1940 cm21.J. Chem. Soc., Dalton Trans., 1997, Pages 2857–2859 2859 Ultrafast experiments on binary metal carbonyls usually show the absorptions of metal carbonyls in vibrational excited states of the electronic ground state which decay over tens or hundreds of picoseconds.15 The vibrational excitation is detected through broadening and shifts in the n(CO) bands.However, [Ru(PPh3)3(CO)] shows no signs of vibrational relaxation although the photon energy absorbed by 1 greatly exceeds the energy needed to break the bonds, just as when photodissociating CO from metal carbonyls. When expelling CO, the CO bond length is altered little, so the CO carries away relatively little vibrational energy leaving much of the excess of energy in the photoproduct.When H2 is dissociated from a metal dihydride, the H ? ? ? H distance is necessarily compressed with the result that much of the excess of energy may be removed by vibrational excitation of expelled H2 (cf. CH2O).16 Almost all of the excess of energy would be removed if H2 leaves in its v = 7 state.** In reality, some of the excess of energy will go into rotation of H2 and translation of the photofragments, as well as vibrations of [Ru(PPh3)3(CO)]. However, the lack of observable vibrational relaxation of [Ru(PPh3)3(CO)] is understandable.The ultrafast experiments provide unambiguous evidence for removal of 1 and formation of [Ru(PPh3)3(CO)] within the experimental time-scale. The use of IR detection has removed any possibility that the signals are due to excited states of precursor or photoproducts. We conclude that photoelimination of H2 from 1 is a process in which H]H bond formation, Ru]H Fig. 3 Ultrafast TRIR kinetics following laser photolysis of 1 dissolved in C6D6 under 1 atm H2 (lex = 304 nm, laser pulse duration = 4 ps) (a) at 1843 cm21 showing formation of [Ru(PPh3)3(CO)] (d), (b) at 1941 cm21 showing bleaching of 1 (j).The very fast component in both traces lasting ca. 6 ps lies within the instrumental response function ** At 304 nm, hn = 393 kJ mol21. Enthalpy 17 of [Ru(dmpe)2H2] æÆ [Ru(dmpe)2] 1 H2 = 95 kJ mol21. If enthalpy change for 1 æÆ [Ru- (PPh3)3(CO)] 1 H2 is the same, excess of energy = 298 kJ mol21.Energy of H2 (v = 7) ª 290 kJ mol21.18 bond cleavage and any reorganisation of the co-ordination geometry at ruthenium occur within 6 ps. Acknowledgements We are grateful to EPSRC for support for equipment, studentships and an Advanced Fellowship (to J. N. M.). We also acknowledge the support of the European Commission and British Gas. References 1 M. Berry, K. Elmitt, M. L. H. Green and S. J. Simpson, J. Chem. Soc., Dalton Trans., 1979, 1950; P.Grebenik, R. Grinter and R. N. Perutz, Chem. Soc. Rev., 1988, 17, 453. 2 W. D. Jones and F. J. Feher, Acc. Chem. Res., 1989, 22, 91; R. M. Chin, L. Dong, S. B. Duckett, M. G. Partridge, W. D. Jones and R. N. Perutz, ibid., 1993, 115, 7685; A. H. Janowicz and R. G. Bergman, J. Am. Chem. Soc., 1983, 105, 3929; J. M. Buchanan, J. M. Stryker and R. G. Bergman, ibid., 1986, 108, 1537; B. M. Sponsler, B. H. Weiller, P. O. Stoutland and R. G. Bergman, ibid., 1989, 111, 6841; P.E. Bloyce, A. J. Rest and I. Whitwell, J. Chem. Soc., Dalton Trans., 1990, 813; M. G. Partridge, A. McCamley and R. N. Perutz, ibid., 1994, 3519; W. A. Kiel, R. G. Ball and W. A. G. Graham, J. Organomet. Chem., 1990, 383, 481; S. A. Brough, C. Hall, A. McCamley, R. N. Perutz, S. Stahl, U. Wecker and H. Werner, ibid., 1995, 504, 33; H. Azizian and R. H. Morris, Inorg. Chem., 1983, 22, 6. 3 R. N. Perutz, Chem. Soc. Rev., 1993, 361; R. Osman, D. I. Pattison, R.N. Perutz, C. Bianchini and M. Peruzzini, J. Chem. Soc., Chem. Commun., 1994, 513. 4 L. Cronin, M. C. Nicasio, R. N. Perutz, R. G. Peters, D. M. Roddick and M. K. Whittlesey, J. Am. Chem. Soc., 1995, 117, 10 047. 5 C. Hall, W. D. Jones, R. J. Mawby, R. Osman, R. N. Perutz and M. K. Whittlesey, J. Am. Chem. Soc., 1992, 114, 7425. 6 R. Osman, R. N. Perutz, A. D. Rooney and A. J. Langley, J. Phys. Chem., 1994, 98, 3562. 7 T. Q. Ye, C. J. Arnold, D. I. Pattison, C. L. Anderton, D.Dukic, R. N. Perutz, R. E. Hester and J. N. Moore, Appl. Spectrosc., 1996, 50, 597. 8 G. L. Geoffroy and M. G. Bradley, Inorg. Chem., 1977, 16, 744. 9 F. Kakiuchi, S. Sekine, Y. Tanaka, A. Kamatani, M. Sonoda, N. Chatani and S. Murai, Bull. Chem. Soc. Jpn., 1995, 68, 62 and refs. therein. 10 M. Sonoda, F. Kakiuchi, A. Kamatani and S. Murai, Chem. Lett., 1996, 109. 11 B. M. Trost, K. Imi and I. W. Davies, J. Am. Chem. Soc., 1995, 117, 5371; F. Kakiuchi, Y. Tanaka, T. Sato, N. Chatani and S. Murai, Chem. Lett., 1995, 679. 12 (a) E. Wilhelm and R. Battino, Chem. Rev., 1973, 73, 1; (b) P. G. T. Fogg and W. Gerrard, Solubility of Gases in Liquids, Wiley, Chichester, 1991. 13 R. J. Mawby, R. N. Perutz and M. K. Whittlesey, Organometallics, 1995, 14, 3268. 14 M. K. Whittlesey, R. N. Perutz, I. G. Virrels and M. W. George, Organometallics, 1997, 16, 268. 15 M. Lee and C. B. Harris, J. Am. Chem. Soc., 1989, 111, 8963; J. C. King, J. Z. Zhang, B. J. Schwartz and C. B. Harris, J. Chem. Phys., 1993, 99, 7595; T. P. Dougherty and E. J. Heilweil, Chem. Phys. Lett., 1994, 227, 19; S. M. Arrivo, T. P. Dougherty, W. T. Grubbs and E. J. Heilweil, Chem. Phys. Lett., 1995, 235, 247. 16 C. B. Moore, Ann. Rev. Phys. Chem., 1983, 34, 525. 17 S. T. Belt, J. C. Scaiano and M. K. Whittlesey, J. Am. Chem. Soc., 1993, 115, 1921. 18 G. Herzberg and L. L. Howe, Can. J. Phys., 1959, 37, 636. Received 25th June 1997; Communication 7/04484D

ISSN:1477-9226    

DOI:10.1039/a704484d

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, Pages 2861–2866 2861 Synthesis, crystal structures and dynamic NMR studies of novel trinuclear copper(I) halide complexes with 2,5-bis[(diphenylphosphino)- methyl]thiophene Bang-Lin Chen, Kum-Fun Mok*,† and Siu-Choon Ng * Department of Chemistry, National University of Singapore, Kent Ridge, 119260, Singapore Novel trinuclear copper(I) halide complexes with 2,5-bis[(diphenylphosphino)methyl]thiophene (dpmt), [Cu3(m3-X)(m-X)2(m-dpmt)2] (X = I 1, Br 2 or Cl 3), have been synthesized and structurally characterised.They have unusual three-runged ladder structures with one triple-bridging and two double-bridging halide atoms. Two of the CuI are tetrahedrally co-ordinated and one, in the middle of the structure unit, has trigonal co-ordination geometry. The trinuclear Cu3(m3-X)(m-X)2 framework shows some changes with halide anion X due to the size eVect and intramolecular non-bonding Cu ? ? ? Cu and X ? ? ? X interactions.The NMR studies showed that the trinuclear framework is retained in solution for 1 (X = I), is in equilibrium with Cu3(m-X)3 for 2 (X = Br) and changes to Cu3(m-Cl)3 for 3 (X = Cl), an eVect attributable to the decrease of halide size from iodide to chloride. The frameworks in the solutions of 2 and 3 exhibit fluxional behaviour involving bromine and chlorine mobility respectively. Copper(I)–phosphine complexes have attracted increasing attention over the past decade due to their structural,1–12 photochemical 6,10,12,13 and antitumor properties.14 These complexes are of diverse structural architecture which is mainly influenced by the preparation conditions, steric properties such as the chain length, spatial arrangements and bulkiness of phosphine ligands and the co-ordinating ability and properties of the counter-ions.Thus copper(I) complexes with monodentate phosphine ligands exist as mononuclear [Cu(PPh3)4]ClO4 2 and [Cu(PPh3)3Cl],3 binuclear [{Cu[P(totp)3](m-X)}2] 4 (totp = tri-otolylphosphine, X = Br or Cl) and [Cu2(PPh3)3(m-X)2] 5 (X = I, Br or Cl) and tetranuclear [{Cu(PPh3)X}4] with pseudo- ‘cubane’ 6 (X = I, Br or Cl) and open ‘step’ 7 (X = I or Br) structures.The dppm [bis(diphenylphosphino)methane] ligand has been reported to support mono- and bi-capping triangular-Cu3 frameworks which are further stabilised by anions in [Cu3- (m3-Cl)2(dppm)3]Cl,8a [Cu3(m3-I)2(m-I)(dppm)2],8b [Cu3(dppm)3- (m3-OH)][BF4]2,8c [Cu3(m3-h1-C]] ] CR)(m-dppm)3]X2 8d (R = Ph, X = BF4; R = But, X = PF6), [Cu3(m3-h1-C]] ] CR)(m3-Cl)(dppm)3]- X8e (R = Ph, X = BF4; R = But, X = PF6) and [(dppm)3Cu3- (m3-C]] ] CC6H4C]] ] C-p-m3)Cu3(dppm)3].8h It can also stabilise the open ‘step’ tetrameric [{(CuX)2(dppm)}2] 9 (X = I, Br or Cl) and planar [Cu4(dppm)4(m4-E)][BF4]2 10 (E = C]] ] C, S or Se) complexes.As 1,2-bis(diphenylphosphino)ethane (dppe) can coordinate as a bidentate bridging and chelating ligand, binuclear complexes are common in its copper(I) complexes [{CuX- (dppe)}2(m-dppe)] 11 (where X is a monoanionic ligand such as N3, Cl, OPh, PhCO2, etc.).Among the above diverse mono-, bi-, tri- and tetra-nuclear arrangements, trinuclear Cu3 frameworks are comparatively few and found only in copper(I) complexes with dppm8 and bis(diphenylphosphino)-alkyl/-arylamine (PNP)12 ligands with triangular Cu3 frameworks which are further bridged and stabilised by anions.Meanwhile, the co-ordination chemistry of thiophene derivatives has been less developed.15,16 The thiophene sulfur shows weak co-ordination ability and thiophene rings usually act as spacing units in the co-ordination compounds of SchiV bases derived from thiophene-2-carbaldehyde or thiophene-2,5- dicarbaldehyde.16 Mathieu et al.17 examined the co-ordination properties of 2,5-bis[2-(diphenylphosphino)ethyl]thiophene † E-Mail: chmmokkf@nus.edu.sg and 2,5-bis[3-(diphenylphosphino)propyl]thiophene.In 2,5-bis- [2-(diphenylphosphino)ethyl]thiophene complexes with Mo0, CoI and RhI, the thiophene is h1 (S) co-ordinated, while in 2,5- bis[3-(diphenylphosphino)propyl]thiophene complexes with RhI the h2, h3 and h7 co-ordination modes have been established. The diVerent behaviour indicates that the chain length between the phosphorus atom and the thiophene ring in the above two ligands aVects the co-ordination properties of thiophene sulfur. In an attempt to study the co-ordination properties of thiophene derivatives in more detail, we have synthesized another novel ligand, 2,5-bis[(diphenylphosphino)methyl]thiophene (dpmt).With suitable bridging length and spatial arrangement, its complexes with copper(I) halides displayed unusual trinuclear Cu3 frameworks with a three-runged ladder structure. Here we report the synthesis of dpmt and its novel trinuclear copper(I) halide complexes [Cu3(m3-X)(m-X)2- (m-dpmt)2] (X = I 1, Br 2 or Cl 3).Crystal structure and dynamic NMR studies show that there are no direct copper(I)–thiophene sulfur interactions in the solid as well as in solution in the trinuclear copper(I) halide complexes. Results and Discussion The ligand was synthesized by reaction of freshly distilled 2,5- bis(chloromethyl)thiophene with LiPPh2 and characterised by MS, NMR and elemental analysis. It is stable in the solid state and unstable in CH2Cl2 and CHCl3 solutions, being easily oxidised to form 2,5-bis(diphenylphosphorylmethyl)thiophene. Reaction of [Cu(MeCN)4]PF6 with dpmt in the molar ratio of 3 : 2 in acetonitrile, followed by additions of methanolic potassium halide or aqueous sodium chloride, gave the trinuclear complexes 1 (X = I), 2 (X = Br) and 3 (X = Cl) as colourless solids.These can also be synthesized by treating CuX with dpmt in dichloromethane followed by addition of methanol. Recrystallisation from dichloromethane–methanol gave single2862 J.Chem. Soc., Dalton Trans., 1998, Pages 2861–2866 crystals suitable for structure determinations. Complexes 1–3 were found stable in solution as well as in the solid state, but single crystals turned opaque on standing in air. Structures of complexes 1–3 In order to investigate any systematic structural changes with the halide anions, complexes 1–3 were structurally characterised. They displayed a similar ‘three-runged ladder’ structure where the Cu3(m3-X)(m-X)2 units were bridged by two dpmt ligands above and below the trinuclear plane. Fig. 1 shows a representative perspective drawing of complex 3. Selected bond distances and angles are listed in Table 1. To the best of our knowledge, complexes 1–3 are the first examples of trinuclear copper(I) complexes with a ‘three-runged ladder’ structural Table 1 Selected bond and contact distances (Å), angles (8) and some structural parameters for complexes for 1–3 Cu(1)]X(1) Cu(1)]X(2) Cu(1)]X(3) Cu(2)]X(1) Cu(2)]X(2) Cu(3)]X(1) Cu(3)]X(3) Cu(2)]P(1) Cu(2)]P(4) Cu(3)]P(2) Cu(3)]P(3) X(1)]Cu(1)]X(2) X(1)]Cu(1)]X(3) X(2)]Cu(1)]X(3) P(1)]Cu(2)]P(4) P(1)]Cu(2)]X(2) P(4)]Cu(2)]X(2) P(1)]Cu(2)]X(1) P(4)]Cu(2)]X(1) X(2)]Cu(2)]X(1) P(2)]Cu(3)]P(3) P(2)]Cu(3)]X(3) P(3)]Cu(3)]X(3) P(2)]Cu(3)]X(1) P(3)]Cu(3)]X(1) X(3)]Cu(3)]X(1) Cu(1)]X(1)]Cu(3) Cu(1)]X(1)]Cu(2) Cu(3)]X(1)]Cu(2) Cu(1)]X(2)]Cu(2) Cu(1)]X(3)]Cu(3) Cu(1) ? ? ? Cu(2) Cu(1) ? ? ? Cu(3) Cu(2) ? ? ? Cu(3) X(1) ? ? ? X(2) X(1) ? ? ? X(3) Cu(1) ? ? ? S(1) Cu(1) ? ? ? S(2) S(1) ? ? ? Cu(1) ? ? ? S(2) 1 (X = I) 2.542(2) 2.545(2) 2.577(2) 2.862(2) 2.678(2) 2.744(2) 2.724(2) 2.273(2) 2.273(2) 2.255(3) 2.264(3) 120.02(6) 120.65(6) 119.17(6) 131.33(9) 104.99(6) 102.17(6) 105.35(7) 105.32(7) 105.33(4) 124.30(10) 103.09(8) 103.69(8) 106.78(8) 109.21(8) 108.86(4) 65.32(4) 65.84(4) 131.15(4) 68.70(4) 65.16(4) 2.949(2) 2.857(2) 5.104(3) 4.406(2) 4.448(2) 2.971(2) 3.134(2) 175.99(8) 2?2CH2Cl2 (X = Br) 2.438(2) 2.419(2) 2.379(2) 2.563(1) 2.577(1) 2.791(1) 2.482(1) 2.254(2) 2.245(2) 2.250(2) 2.249(2) 113.01(5) 119.88(5) 120.08(5) 123.65(6) 102.41(5) 101.57(5) 110.27(5) 112.08(5) 104.01(3) 126.58(6) 105.34(5) 109.29(5) 99.35(5) 109.65(5) 104.35(3) 64.85(3) 70.40(3) 132.77(3) 70.45(3) 70.87(4) 2.885(2) 2.819(2) 4.907(3) 4.051(2) 4.189(2) 2.659(2) 3.339(2) 172.26(5) 3?1.25CH2Cl2 (X = Cl) 2.377(2) 2.275(2) 2.237(2) 2.435(2) 2.456(2) 2.757(2) 2.340(2) 2.253(2) 2.242(2) 2.248(2) 2.241(2) 107.87(7) 116.61(8) 127.40(8) 122.20(7) 102.53(7) 101.86(7) 112.19(6) 113.58(6) 100.51(6) 126.30(7) 105.57(7) 111.91(7) 100.56(6) 108.60(6) 100.45(6) 66.47(5) 73.84(5) 137.94(7) 75.24(6) 76.41(7) 2.891(2) 2.832(2) 4.648(3) 3.761(3) 3.926(3) 2.645(2) 3.341(2) 168.76(7) Mean deviation of 0.008 0.164 0.146 Cu3X(1) plane/Å Mean deviation of 0.023 0.140 0.142 Cu(1)X3 plane/Å Mean deviation of 0.019 0.159 0.156 Cu3X3 plane/Å Deviation of Cu(1) from Cu3X3 plane/Å 0.046 0.349 0.341 framework constructed of one triple-bridging, atom X(1), two double-bridging X atoms X(2) and X(3), two tetrahedrally coordinated copper atoms Cu(2) and Cu(3) and one trigonally coordinated atom Cu(1), in the middle of the trinuclear structure unit.Atoms Cu(2) and Cu(3) are each co-ordinated to the phosphorus donor of two bridging dpmt molecules, one bridging halide and one m3-bridging halide. The two thiophene rings are syn sandwiching the Cu3(m3-X)(m-X)2 plane. Structures involving a mixed copper(I) stereochemistry of tetrahedral and trigonal chromophores and both triple- and double-bridging X have been found in the tetranuclear open ‘step’ [{Cu(PPh3)- X}4] 7 and [{(CuX)2(dppm)}2] 9 (X = I, Br or Cl).The structures of complexes 1–3 have some similarities with these open ‘step’ molecules, but diVer from them by the virtual planarity of the trinuclear Cu3(m3-X)(m-X)2 frame. Obviously the dpmt ligands with a suitable bridging length and spatial arrangement play important roles in stabilising the planar trinuclear Cu3(m3-X)- (m-X)2 framework.Such a ‘three-runged ladder’ structure is comparatively uncommon and has so far been found only in trinuclear rhodium(I) complexes [Rh3(m-dpmp)2(CO)3I2]BPh4 18a and [Rh3(m-dpmp)2(CO)I4]BPh4 18b {dpmp = bis[(diphenylphosphino) methyl]phenylphosphine} in which the planar trinuclear Rh3(m3-I)(m-I)(m-CO) or Rh3(m3-I)(m-I)2 planes are bridged by two dpmp ligands. As previously noted,5,7,9 the Cu]X bond distances for tetrahedrally co-ordinated Cu(2) and Cu(3) are longer than those for trigonally co-ordinated Cu(1) and decrease with the halide anions from iodide to chloride.The longest Cu]X bond distance is 2.862(2) Å in 1, 2.791(1) Å in 2 and 2.757(2) Å in 3. Such long distances suggest that the above three bond interactions are comparatively weak. As the size of the bridging halogen atoms decreases along the sequence I > Br > Cl the X(2)]Cu(2)]X(1) and X(3)]Cu(3)]X(1) angles decrease and Cu(3)]X(1)]Cu(2), Cu(1)]X(2)]Cu(2) and Cu(1)]X(3)]Cu(3) angles increase. The X]Cu(1)]X angles are all within 18 of an ideal 1208 for trigonal planar co-ordinated copper(I) in 1, but deviate increasingly from the ideal value from 2 [X = Br, 113.01(5), 119.88(5), 120.08(5)8] to 3 [X = Cl, 107.87(7), 116.61(8), 127.40(8)8].The mean deviation of Cu(1) from the corresponding Cu3X3 mean plane is 0.046 Å in 1, 0.349 Å in 2 and 0.341 Å in 3, all towards S(1), so that the Cu(1) ? ? ? S(1) distance decreases with halide anions in the above three trinuclear complexes: 2.971(2) Å in 1, 2.659(2) Å in 2 and 2.645(2) Å in 3.The stereochemical changes with the halide anions in the above three structures, to some extent, are due to the size eVects of the diVerent halide anions on the trinuclear Cu3(m3-X)(m-X)2 frameworks and intramolecular non-bonding Cu ? ? ? Cu and X? ? ? X interactions. Size eVects of halide anions on structural changes have been found in trinuclear [Rh3(m-dpmp)2(CO)3X2]- BPh4 18a,c (X = I, Br or Cl).In [Rh3(m-dpmp)2(CO)3I2]BPh4 18a,c Fig. 1 Perspective view of the structure of [Cu3(m3-Cl)(m-Cl)2- (m-dpmt)2] 3 with atomic numbering schemeJ. Chem. Soc., Dalton Trans., 1998, Pages 2861–2866 2863 and [Rh3(m-dpmp)2(CO)I4]BPh4,18b which have similar structural features to our reported complexes, only iodide anions can bridge the planar Rh3(m3-I)(m-I)(m-CO) or Rh3(m3-I)(m-I)2, while the bromide and chloride anions are not large enough to act as m3 planar ligands.Thus [Rh3(m-dpmp)2(CO)3X2]BPh4 18a,c (X = Br or Cl) have slightly diVerent structural features [the two tridentate bridging dpmp ligands determine the Rh3(m3-I)(m-I)- (m-CO) or Rh3(m3-I)(m-I)2 planes]. Teo and Calabrese 19 have systematically studied the structures of (R3Y)4M4X4-type complexes (R = Ph or Et; Y = P or As; M = Cu or Ag; X = Cl, Br or I) and made an unequivocal conclusion that their stereochemistries are to a significant extent dictated by intramolecular non-bonded van der Waals interactions which are a function of the size of the metal, the bridging X and the terminal ligands.In our three trinuclear [Cu3(m3-X)(m-X)2- (m-dpmt)2] complexes the Cu(2) ? ? ? Cu(3) separation decreases with the halide anion from iodide [1, 5.104(3) Å] to bromide [2, 4.907(3) Å] and to chloride [3, 4.648(3) Å] due to the decreasing atom size. Distortion of the planar Cu3(m3-X)(m-X)2 framework in 2 and 3, to some extent, can minimise the repulsions between Cu ? ? ? Cu and X ? ? ? X as shown in the X ? ? ? X distances [Cl ? ? ? Cl 3.761(3) and 3.926(3); Br ? ? ? Br 4.051(2) and 4.189(2); I ? ? ? I 4.406(2) and 4.448(2) Å].These distances are all greater than or close to normal van der Waals contacts (viz. Cl ? ? ? Cl 3.60; Br ? ? ? Br 3.90; I ? ? ? I 4.30 Å) 20 suggesting that these halogen–halogen interactions are strongly repulsive. The CuI ? ? ? S contact distances in the range 2.89–3.44 Å were found in other systems containing thiophene units 16 and were considered to be weak or non-bonding interactions.Copper(I)– sulfur bond distances are in the range 2.23–2.48 Å for coordinated sulfurs.1 Co-ordination of thiophene sulfur has been established in [M(sttp)Cl] 21 (M = Fe21, Ni21 or Cu21, Hsttp = 5,10,15,20-tetraphenyl-21-thiaporphyrin) with M]S bond distances of 2.388 (M = FeII), 2.296(1) (M = NiII) and 2.335(2) Å (M = CuII), fac-[Mo(CO)3L] 17a [Mo0]S 2.569(1) Å] and [Rh(CO)L][ClO4] 17a [RhI]S, 2.318(1) Å] {L = 2,5-bis- [2-(diphenylphosphino)ethyl]thiophene}.The fact that the Cu(1) ? ? ? S(1) distances in the range 2.645(2)–2.971(2) Å are longer than the sum of the covalent radii (2.21 Å),22 whilst the S(1)]C(14), S(1)]C(17), S(2)]C(44) and S(2)]C(47) bond distances are comparable with 1.714(2) Å in free thiophene,23 together with corroborating solution NMR studies, suggest that there are no direct bonded interactions between CuI and thiophene sulfur in our complexes.The copper–copper distances are in the range 2.819(2)–2.949(2) Å in 1–3, shorter than those found in ‘cubane’ [Cu4X4(PPh3)4] 6 (X = I, Br or Cl) [2.874(5)–3.164(4) Å] and ‘step’ [Cu4X4(PPh3)4] 7 (X = I or Br) [2.835(3)–3.448(3) Å], and comparable with those found in ‘step’ [{(CuX)2(dppm)}2] 9 (X = I, Br or Cl) [2.682(7)–3.180(2) Å], indicating that there are no direct Cu ? ? ? Cu interactions.Trinuclear copper(I) complexes though comparatively rare can be found in some reduced forms of ascorbate oxidase.24 Some spatial Cu3 arrangements together with the tricopper(I) site of ascorbate oxidase are shown in Fig. 2. The ligand dppm is the appropriate supporter in Cu3 framework (i) 8 which are further mono- or bi-capped by acetylide, alkynyl, halide, isocyanide and WS4 anions. In Cu3 framework (ii) 25 S-donor edgebridging ligands such as ethane-1,2-dithiolate, S4, S6, Me3PS and (PhO)2P(S)NC(S)NEt2 are needed to stabilise the structure framework.N-Donor ligands have recently been developed to support the triangular Cu3 framework (iv) 26 as models of the active site of ascorbate oxidase; as no co-ordinated anions are involved in bridging, Cu ? ? ? Cu distances in structure framework (iv) are comparatively long. In our reported Cu3 framework (iii) the new ligand dpmt with suitable bridging length and spatial arrangement stabilises the Cu3(m3-X)(m-X)2 framework, the triangular Cu3 core is approximately isosceles with one edge distance much longer than the other two as shown in Table 1.As no obvious direct Cu ? ? ? Cu bonding interactions 27 exist in these systems the Cu ? ? ? Cu distances were mainly determined by the spatial arrangements and bridging length of the ligands and the electronic properties of the bridging anions. The Cu ? ? ? Cu distances in some of the trinuclear Cu3 complexes are listed in Table 2.Besides the triangular Cu3 frameworks shown in Fig. 2, equilateral triangular Cu3 geometry linked by Cu] H]B and Cu]Cu interactions was found in [Cu3(m-H)3- {C2B9H9[C5H4N(CO2CH3)-4]}] 28a with a relatively short copper–copper distance of 2.519(2) Å. G. van Koten and coworkers 28c reported two triangular organocopper(I) complexes bridged by aryl and O2CPh in [Cu3(C6H2Me3-2,4,6)(O2CPh)2], aryl and Br in [Cu3Br{C6H4(CH2MeCH2CH2NMe2)-2}2]. Solution studies The electronic absorption spectrum of complexes 1–3 show bands at about 226 and 256 nm in dichloromethane, attributable to the intraligand transition of dpmt, since the uncoordinated dpmt also absorbs strongly in this region.The low-energy absorptions at about 320 nm of 1 and 300 nm of 2 are likely to arise from a ligand-to-metal charge transfer (LMCT) transition. The room-temperature 31P-{1H} and 1H NMR spectra of 1 show a singlet 31P resonance at d 216.9 and singlet thiophene proton resonances at d 5.61 respectively, which means the surroundings of the two dpmt ligands around the trinuclear Cu3(m3-I)(m-I)2 plane are identical.The existence of two sets of doublet methylene proton resonances at d 4.12 (J = 14.0) and 3.61 (J = 14.0 Hz) indicates that the two geminal methylene protons are non-equivalent and are coupled to each other, so that rotation of bridging ligands around the trinuclear Cu3(m3-I)(m-I)2 framework is blocked. The non-equivalence of the two methylene protons in the 1H NMR spectrum arises on account of the diVerent orientations of the two protons to the trinuclear Cu3(m3-I)(m-I)2 framework, with one equatorial and the other axial which is also established in the solid structure of 1.The 31P-{1H} and 1H NMR spectra of 2 at room temperature (300 K) are similar to those of 1 in CDCl3 solution, exhibiting a singlet 31P resonance at d 210.3, singlet thiophene proton resonances at d 5.44 and two sets of doublets at d 4.04 and 3.48, again indicating that the two ligands are symmetrically oriented with respect to the trinuclear Cu3(m3-Br)(m-Br)2 framework. Additional weak resonances at d 1.2 and 28.0 in 31P-{1H} NMR and d 5.73 in 1H NMR suggest that there is also a minor amount of another isomer in solution. Variable-temperature 31P-{1H} and 1H NMR spectra of 2 are unchanged over the range 218 to 320 K.Those of the minor isomer exhibit some changes as evident in thiophene protons at d 5.68 (320 K) to 5.85 and 5.79 (218 K) and several methylene proton resonances Fig. 2 Comparison of some triangular CuI 3 frameworks. (i) Ref. 8, (ii) ref. 25, (iii) this work, (iv) ref. 26. See text for detailed discussion2864 J. Chem. Soc., Dalton Trans., 1998, Pages 2861–2866 Table 2 Comparison of Cu ? ? ? Cu distances (Å) in some of the triangular Cu3 frameworks Complex [Cu3(m3-I)(m-I)2(m-dpmt)2] [Cu3(m3-Br)(m-Br)2(m-dpmt)2]?2CH2Cl2 [Cu3(m3-Cl)(m-Cl)2(m-dpmt)2]?1.25CH2Cl2 [Cu3(m3-I)2(m-I)(m-dppm)3] [Cu3(m3-Cl)2(m-dppm)2]Cl [Cu3(m3-OH)(m-dppm)3][BF4]2 [Cu3(m3-h1-C]] ] CR)(m-h1-C]] ] CNR)(m-dppm)3][BF4] [Cu3(m3-h1-C]] ] CPh)(m-dppm)3][BF4]2 [Cu3(m3-h1-C]] ] CPh)2(m-dppm)3][BF4] [Cu3(m3-h1-C]] ] CPh)(m3-Cl)(m-dppm)3][BF4] Na[Me3NCH2Ph]2[Cu3(S2C2H4)3]?MeOH [{Cu[(PhO)2P(S)NC(S)NEt2]}3] [Cu3(C6H2Me3-2,4,6)(O2CPh)2] [Cu3Br{C6H4(CH2MeCH2CH2NMe2)-2}2] [Cu3L1 2][PF6] c [Cu(m-L2)2{Cu(cnge)(MeCN)}2][BF4]3?MeCNd Tricopper(I) site of ascorbate oxidase Cu ? ? ? Cu 2.857(2) 2.819(2) 2.832(2) 2.546(3) 3.175(4) 3.120(2) 2.497(2) 2.813(2) 2.570(3) 2.785(3) 2.749(1) 2.769(1) 2.421(2) 2.403(1) 2.915 3.624(16) 4.1 2.949(2) 2.885(2) 2.891(2) 2.916(4) 3.175(4) 3.127(2) 2.800(2) 2.904(3) 2.598(3) 2.803(3) 2.751(1) 2.773(1) 2.421(2) 2.409(1) 3.500 3.634(15) 4.4 5.104(3) 4.907(3) 4.648(3) 3.142(4) 3.281(3) 3.322(2) 3.294(2) 3.274(3) 2.615(3) 2.871(3) 2.846(1) 2.816(1) 2.888(2) 3.299(1) 3.614 5.011(15) 5.1 Ref aaa 8(b) 8(a) 8(c) 8(i) b 8(d ) 8(d ) 8(d ) 25(d) 25(e ) 28(b) 28(c) 26(b) 26(a) 24 a This work.b R = 4-MeC6H4. c L1 = Hydrotris[3-(2-pyridyl)pyrazol-1-yl]borate. d L2 = 3,6-Bis(3-tert-butylpyrazolyl)pyridazine, cnge = 2-cyanoguanidine. at 218 K, suggesting fluxional behaviour in solution. It is of interest that the relative concentration of the two isomers is dependent on the temperature. The minor : major concentration ratio is 0.08, 0.10, 0.18, 0.21 and 0.75 : 1 at 218, 233, 273, 300 and 320 K respectively, indicating that the higher the temperature the higher is the concentration of the minor isomer, and transformation of the major to the minor isomer is an endothermic reaction.The solid structure of 2 shows that the Cu(3)]Br(1) interaction is comparatively weak with a long bond distance of 2.79(1) Å, so there is a possible equilibrium (1) in CDCl3 solution with DH‡ ca. 6.5 kJ mol21 obtained from the Van’t HoV equation.29 Room-temperature 31P-{1H} and 1H NMR spectra of complex 3 in CDCl3 solution, however, are quite diVerent from those of 1 and 2, and show two sets of singlet 31P resonances at d 22.5 and 27.4, one set of thiophene proton resonances at d 5.70 and one set of methylene proton resonances at d 3.71.Variable-temperature NMR spectroscopy was used to probe the dynamic behaviour of 3 in CDCl3 solution as shown in Fig. 3. At ambient and sub-ambient temperatures, the 31P-{1H} NMR spectrum shows two singlet resonances. On increasing the temperature the two sets of singlet 31P resonances gradually coalesce to a broad 31P resonance at d 22.9 with a coalescence temperature of 323 K.Likewise, at low temperatures, the 1H NMR spectrum has two sets of singlet at d 5.84 and 5.77 (218 K), which gradually coalesce to a singlet for thiophene protons at d 5.70 (300 K) with a coalescence temperature of 286 K. At 218 K the 1H NMR shows four sets of doublet methylene protons at d 4.28 (2J = 13.5), 3.70 (2J = 13.7), 3.52 (2J = 13.5) and 3.46 (2J = 13.7 Hz).Irradiation of the protons at d 3.70 removes the doublet coupling at d 3.46, indicating they are coupled to each other; similarly, the protons at d 4.28 are coupled with those at d 3.52. The two sets of singlet 31P resonances have an integration ratio of 1 : 0.92 at 218 K. The diVerent NMR behaviour of 3, compared with those of 1 and 2 in solution, possibly indicates that its structure in solution is diVerent from that in the solid phase. The molecular structure of 3 indicates that the Cu(3)]Cl(1) bond distance [2.757(2) Å] is very long and interaction between Cu(3) and Cl(1) is comparatively weak.The above NMR behaviour in solution suggests that 3 is undergoing the fluxional process shown in equation (2). At high temperature, rapid equilibration leads to equivalence of four phosphorus atoms and only one set of 31P-{1H} signals can be resolved. Fluxional processes involving chlorine mobility have been established in NMR studies of some trinuclear complexes such as [Rh3(CO)3(m-Cl)Cl(m-dpmp)2]BPh4,18a,c [Ir3- (m-CO)2(CO)2(m-Cl)Cl(m-dpma)2]BPh4, [Ir2Rh(m-CO)2(CO)3- (m-Cl)(m-dpma)2]BPh4 and [Rh2Pd(m-Cl)(CO)2Cl2(m-dpma)2]- BPh4 30 {dpma = bis[(diphenylphosphino)methyl]phenylarsine}. The activation energy DG‡ for process (2) calculated by the Eyring equation 31 is ca. 57 kJ mol21 from VT 31P-{1H} NMR Fig. 3 Variable-temperature 31P-{1H} (a) and 1H (b) NMR spectra of complex 3 in CDCl3; the signals at d ca. 5.30 in (b) are from CH2Cl2J.Chem. Soc., Dalton Trans., 1998, Pages 2861–2866 2865 Table 3 Crystal data and refinement details for complexes 1, 2?2CH2Cl2 and 3?1.25CH2Cl2 Formula M Crystal system Space group a/Å b/Å c/Å b/8 U/Å3 Z Dc/mg cm23 m/mm21 F(000) Crystal size/mm hkl Index ranges Independent reflections No. parameters refined Largest diVerence peak and hole/e Å23 R1 a [I > 2s(I)] wR2 b Goodness of fit on F2 1 C60H52Cu3I3P4S2 1532.34 Monoclinic P21/c (no. 14) 29.207(4) 9.929(2) 22.083(4) 110.78(1) 5987(2) 4 1.700 2.816 3000 0.33 × 0.25 × 0.23 235 to 29, 29 to 11, 221 to 26 10 820 649 2.34, 21.70 0.0713 0.1844 1.031 2?2CH2Cl2 C62H56Br3Cl4Cu3P4S2 1561.22 Monoclinic C2/c (no. 15) 58.950(6) 10.390(2) 21.589(3) 104.33(2) 12 812(3) 8 1.619 3.229 6240 0.30 × 0.20 × 0.13 257 to 71, 212 to 11, 224 to 26 11 775 703 2.69, 22.36 0.0536 0.1449 1.047 3?1.25CH2Cl2 C61.25H54.5Cl5.5Cu3P4S2 1364.14 Monoclinic C2/c (no. 15) 58.830(1) 10.219(1) 21.663(1) 104.00(1) 12 636(1) 8 1.434 1.438 5556 0.50 × 0.38 × 0.25 247 to 73, 212 to 11, 227 to 26 12 811 703 1.62, 21.41 0.0685 0.1956 0.966 a R1 = Sw|Fo 2 Fc|/S(Fo).b wR2 = [Sw(Fo 2 2 Fc 2)2/SwFo 4]� �� . spectra (Tc = 323 K, Dn = 2171 Hz), agreeing well with a value of ca. 60 kJ mol21 derived from VT 1H NMR spectra for the coalescence of thiophene protons (Tc = 286 K, Dn = 34.3 Hz). Variable-temperature 31P-{1H} and 1H NMR spectra of the minor isomer of 2 are similar to those of 3 in solution, indicating that the minor isomer of 2 also shows similar fluxional behaviour to that of 3.The diVerent NMR behaviours of complexes 1–3, to some extent, are attributed to a size eVect of the halide anions. The small size of chlorine (X = Cl) is not large enough for Cl(1) to make contact with all three copper centres, so that the Cu(2)]Cl(1) or Cu(3)]Cl(1) bond is readily broken in solution. Experimental Materials and methods All solvents were dried and degassed prior to use and all reactions were carried out under a nitrogen atmosphere.Elemental analyses were carried out by the Microanalytical Laboratory of the Department of Chemistry, National University of Singapore. Electron impact mass spectra were recorded on a Micromass VG 7035 mass spectrometer at 70 eV (ca. 1.12 × 10217 J), UV/VIS spectra at room temperature on a Shimadzu UV-240 spectrophotometer in CH2Cl2 solution and NMR spectra on a Bruker AC500 at 500.14 (1H) or 202.46 MHz (31P) using SiMe4 or 85% H3PO4 as standards.The compounds 2,5-bis(chloromethyl)thiophene,32 PPh2H33 and [Cu(MeCN)4]- PF6 34 were prepared according to the published methods. Other reagents were used as received. Preparations 2,5-Bis[(diphenylphosphino)methyl]thiophene. A solution of LiPPh2 (45.0 mmol) in thf (150 cm3) was prepared from PPh2H (7.9 cm3, 45.0 mmol) and LiBun in hexane (1.6 M, 28.1 cm3, 45.0 mmol) and cooled to 0 8C. To this solution was slowly added freshly distilled 2,5-bis(chloromethyl)thiophene (22.5 mmol, 4.08 g) dissolved in thf (150 cm3).The solution was stirred for 3 h at room temperature, after which the thf was removed under vacuum. The residue was dissolved in dichloromethane (150 cm3), and the solution washed with water (3 × 150 cm3). After removing the solvent, crystallisation of the residue from methanol gave 4.76 g (44%) of dpmt as pale yellow crystals. d(31P) 211.2 (s); d(1H) 7.60–7.34 (m, 20 H, phenyl ring), 6.36 (s, 2 H, thiophene ring) and 3.48 (s, 4 H, methylene). EI MS: m/z 480 (M1) (Found: C, 74.85; H, 5.38; S, 6.46.Calc. for C30H26P2S: C, 74.96; H, 5.45; S, 6.67%). 2,5-Bis(diphenylphosphorylmethyl)thiophene. A dichloromethane solution (20 cm3) of dpmt (1 mmol, 0.48 g) was gently heated for 5 min. After removing the solvent in vacuo, crystallisation of the residue from dichloromethane–acetonitrile gave 0.38 g (75%) of colourless crystals. d(31P) 28.4 (s); d(1H) 7.69– 7.40 (m, 20 H), 6.57 (d, 2 H) and 3.72 [d, 4 H, 3J(PH) = 12.4 Hz].EI MS: m/z 512 (M1) (Found: C, 70.20; H, 5.01; S, 6.18. Calc. for C30H26O2P2S: C, 70.28; H, 5.11; S, 6.25%). [Cu3(Ï3-X)(Ï-X)2(Ï-dpmt)2] (X 5 I 1 or Br 2). The compound dpmt (0.30 mmol) was added to a stirred solution of [Cu- (MeCN)4]PF6 (0.45 mmol) in acetonitrile (15 cm3). After 2 h, methanol (10 cm3) containing KX (0.90 mmol) was added and stirred for 1 h. The precipitated white powder was collected and recrystallised from CH2Cl2–MeOH in 45–58% yield.Compound 1: d(31P) (CDCl3, 298 K) 216.9 (s); d(1H) (CDCl3, 298 K) 8.61–6.90 (m, 20 H), 5.61 (s, 2 H), 4.12 [d, 2 H, 2J(HH) = 14.0] and 3.61 [d, 2 H, 2J(HH) = 14.0 Hz]; UV/VIS lmax/nm (e/M21 cm21) 226 (88 200), 256 (sh, 54 100) and 320 (sh, 12 200) (Found: C, 47.15; H, 3.46; Cu, 11.86; S, 4.32. Calc. for C60H52Cu3I3P4S2: C, 47.02; H, 3.42; Cu, 12.44; S, 4.18%). Compound 2: d(31P) (CDCl3, 300 K) 210.3 (s); d(1H) (CDCl3, 300 K) 7.72–6.87 (m, 20 H), 5.44 (s, 2 H), 4.04 [d, 2 H, 2J(HH) = 13.6] and 3.48 [d, 2 H, 2J(HH) = 13.4 Hz]; UV/VIS lmax/nm (e/M21 cm21) 226 (89 300), 256 (sh, 61 200) and 300 (sh, 24 500) (Found: C, 51.49; H, 3.58; Cu, 13.14; S, 4.25.Calc. for C60H52Br3Cu3P4S2: C, 51.78; H, 3.77; Cu, 13.71; S, 4.61%). [Cu3(Ï3-Cl)(Ï-Cl)2(Ï-dpmt)2] 3. Compound dpmt (0.30 mmol) was added to a stirred solution of [Cu(MeCN)4]PF6 (0.45 mmol) in acetonitrile (15 cm3). After 2 h an aqueous solution (10 cm3) containing NaCl (0.90 mmol) was added and stirred for 1 h.After the acetonitrile was removed in vacuo, CH2Cl2 (30 cm3), was added to the residue. The CH2Cl2 phase was washed twice with water (20 cm3) and evaporated to give crude complex 3. This was purified by washing with small amounts of methanol and recrystallisation from CH2Cl2–MeOH to get 3 in 35% yield. d(31P) (CDCl3, 300 K) 22.5 (s) and 27.4 (s); d(1H)2866 J. Chem. Soc., Dalton Trans., 1998, Pages 2861–2866 (CDCl3, 300 K) 7.37 and 7.17 (br, 20 H), 5.70 (s, 2 H) and 3.71 (s, 4 H).UV/VIS: lmax/nm (e/M21 cm21) 226 (88 300) and 256 (sh, 53 600) (Found: C, 56.93; H, 4.46; Cu, 14.68; S, 4.85. Calc. for C60H52Cl3Cu3P4S2: C, 57.27; H, 4.17; Cu, 15.16; S, 5.10%). Crystallography A single crystal of complex 1 was mounted on a glass fiber and covered with a film of an inert oil, while crystals of 2 and 3 were sealed into glass capillaries with the mother-liquor. Crystal data and a summary of the crystallographic analyses are given in Table 3.The data were collected at 295 K on a Siemens CCD diffractometer using graphite-monochromated Mo-Ka radiation (l = 0.710 73 Å). All the structures were solved by direct methods and some non-hydrogen atoms located from Fourierdi Verence maps. All non-hydrogen atoms were refined anisotropically. Refinement was by full-matrix least squares based on F 2 using SHELXL 93.35 Hydrogen atoms were placed in assigned positions and with their isotropic thermal parameters riding on the parent carbon atoms.The largest residual peaks and holes were found above and below the Cu3(m3-X)(m-X)2 plane. CCDC reference number 186/1066. Acknowledgements We thank the National University of Singapore for the research scholarship to B.-L. Chen and Dr. P. H. Leung and Ms. S.-Y. Wong for their discussion of the NMR studies. References 1 B. J. Hathaway, in Comprehensive Coordination Chemistry, eds. G. Wilkinson, R. D. Gillard and J. A. McCleverty, Pergamon Press, Oxford, 1987, vol.V, ch. 53 and refs. therein. 2 L. M. Engelhardt, C. Pakawatchai, A. H. White and P. C. Healy, J. Chem. Soc., Dalton Trans., 1985, 125. 3 J. T. Gill, J. J. Mayerle, P. S. Welcker, D. F. Lewis, D. A. Ucko, D. J. Barton, D. Stowens and S. J. Lippard, Inorg. Chem., 1976, 15, 1155. 4 S. K. Hadjikakou, P. D. Akrivos, P. Karagiannidis, E. Paptopoulou and A. Terzis, Inorg. Chim. Acta, 1993, 210, 27. 5 D. F. Lewis, S. J. Lippard and P. S. Welcker, J. Am. Chem.Soc., 1970, 92, 3805; V. G. Albano, P. L. Bellon, G. Ciani and M. Manassero, J. Chem. Soc., Dalton Trans., 1972, 171; P. G. Eller, G. J. Kubas and R. R. Ryan, Inorg. Chem., 1977, 16, 2454. 6 M. R. Churchill and K. L. Kalra, Inorg. Chem., 1974, 13, 1065; P. F. Barron, J. C. Dyason, L. M. Engelhardt, P. C. Healy and A. H. White, Inorg. Chem., 1984, 23, 3766; J. C. Dyason, P. C. Healy, L. M. Engelhardt, C. Pakawatchai, V. A. Patrick, C. L. Raston and A. H. White, J. Chem.Soc., Dalton Trans., 1985, 831. 7 M. R. Churchill and K. L. Kalra, Inorg. Chem., 1974, 13, 1427; M. R. Churchill, B. G. DeBoer and D. J. Donovan, Inorg. Chem., 1975, 14, 617. 8 (a) N. Bresciani, N. Marsich, G. Nardin and L. Randaccio, Inorg. Chim. Acta, 1974, 10, L5; (b) G. Nardin, L. Randaccio and E. Zangrando, J. Chem. Soc., Dalton Trans., 1975, 2566; (M. Ho and R. Bau, Inorg. Chem., 1983, 22, 4079; (d ) J. Díez, M. P. Gamasa, J. Gimeno, E. Lastra, A. Aguirre and S.García-granda, Organometallics, 1993, 12, 2213; (e) V. W. W. Yam, W. K. Lee and T. F. Lai, Organometallics, 1993, 12, 2383; ( f ) C. K. Chan, C. X. Guo, R. J. Wang, T. C. W. Mak and C. M. Che, J. Chem. Soc., Dalton Trans., 1995, 753; (g) V. W. W. Yam, W. K. Lee, K. K. Cheung, B. Crystall and D. Phillips, J. Chem. Soc., Dalton Trans., 1996, 3283; (h) V. W. W. Yam, W. K. M. Fung and K. K. Cheung, Chem. Commun., 1997, 963; (i) J. Díez, M. P. Gamasa, J. Gimeno, A. Aguirre and S. García-granda, Organometallics, 1997, 16, 3684 and refs therein. 9 N. Marsich, G. Nardin and L. Randaccio, J. Am. Chem. Soc., 1973, 95, 4053; G. Nardin and L. Randaccio, Acta Crystallogr., Sect. B, 1974, 30, 1377; S. Ramaprabhu, N. Amstutz, E. A. C. Lucken and G. Bernardinelli, J. Chem. Soc., Dalton Trans., 1993, 871. 10 V. W. W. Yam, W. K. Lee and T. F. Lai, J. Chem. Soc., Chem. Commun., 1993, 1571; V. W. W. Yam, W. K. M. Fung and K. K. Cheung, Angew. Chem., Int. Ed. Engl., 1996, 35, 1100; V.W. W. Yam, K. W. W. Lo and K. K. Cheung, Inorg. Chem., 1996, 35, 3459. 11 A. P. Gaughan, R. F. Ziolo and Z. Dori, Inorg. Chem., 1971, 10, 2776; A. P. Gaughan, K. S. Bowman and Z. Dori, Inorg. Chem., 1972, 11, 601; V. G. Albano, P. L. Bellon and G. Ciani, J. Chem. Soc., Dalton Trans., 1972, 1938; P. Fiaschi, C. Floriani, M. Pasquali, A. Chiesi-Villa and C. Guastini, Inorg. Chem., 1986, 25, 462; E. W. Ainscough, E. N. Baker, A. G. Bingham, A. M. Brodie and C. A. Smith, J.Chem. Soc., Dalton Trans., 1989, 2167; E. W. Ainscough, E. N. Baker, M. L. Brader, A. M. Brodie, S. L. Ingham, J. M. Waters, J. V. Hanna and P. C. Healy, J. Chem. Soc., Dalton Trans., 1991, 1243; M. B. Cingi, A. M. Manotti-Lanfredi, F. Ugozzoli, A. Camus and N. Marsich, Inorg. Chim. Acta, 1997, 262, 69. 12 V. W. W. Yam, W. K. M. Fung and M. T. Wong, Organometallics, 1997, 16, 1772. 13 See, for example, (a) D. Li, H. K. Yip, C. M. Che, Z. Y. Zhou, T. C. W. Mak and S. T. Liu, J.Chem. Soc., Dalton Trans., 1992, 2445; (b) V. W. W. Yam, S. W. K. Choi, C. L. Chan and K. K. Cheung, Chem. Commun., 1996, 2067; (c) V. W. W. Yam, W. K. Lee and K. K. Cheung, J. Chem. Soc., Dalton Trans., 1996, 2335. 14 S. J. Berners-Price and P. J. Sadler, Struct. Bonding (Berlin), 1988, 70, 27; V. Scarcia, A. Furlani, G. Pilloni, B. Longato and B. Corain, Inorg. Chim. Acta, 1997, 254, 199. 15 R. J. Angelici, Coord. Chem. Rev., 1990, 105, 61; T. B. Rauchfuss, Prog. Inorg.Chem., 1991, 39, 259. 16 N. A. Bailey, M. M. Eddy, D. E. Fenton, S. Moss, A. Mukhopadhyay and G. Jones, J. Chem. Soc., Dalton Trans., 1984, 2281; P. C. Yates, M. G. B. Drew, J. T. Grimshaw, K. P. McKillop, S. M. Nelson, P. T. Ndifon, C. A. McAuliVe and J. Nelson, J. Chem. Soc., Dalton Trans., 1991, 1973; J. F. Modder, R. J. Leijen, K. Vrieze, W. J. J. Smeets, A. L. Spek and G. van Koten, J. Chem. Soc., Dalton Trans., 1995, 4021; M. G. B. Drew, C. J. Harding, O. W. Howarth, Q.Lu, D. J. Marrs, G. G. Morgan, V. McKee and J. Nelson, J. Chem. Soc., Dalton Trans., 1996, 3021; S. R. Collinson and D. E. Fenton, Coord. Chem. Rev., 1996, 148, 19. 17 (a) M. Alvarez, N. Lugan and R. Mathieu, Inorg. Chem., 1993, 32, 5652; (b) M. Alvarez, N. Lugan, B. Donnadieu and R. Mathieu, Organometallics, 1995, 14, 365. 18 (a) M. M. Olmstead, R. R. Guimerans and A. L. Balch, Inorg. Chem., 1983, 22, 2473; (b) A. L. Balch, R. R. Guimerans and M. M. Olmstead, J. Organomet.Chem., 1984, 268, C38; (c) A. L. Balch, L. A. Fossett, R. R. Guimerans, M. M. Olmstead, P. E. Reedy, jun., and F. E. Wood, Inorg. Chem., 1986, 25, 1248. 19 B. K. Teo and J. C. Calabrese, Inorg. Chem., 1976, 15, 2467; 2474. 20 L. Pauling, The Nature of the Chemical Bond, 3rd edn., Cornell University Press, Ithaca, NY, 1960, p. 260. 21 L. Latos-Grazynski, J. Lisowski, M. M. Olmstead and A. L. Balch, Inorg. Chem., 1989, 28, 1183. 22 J. Emsley, The Elements, Oxford University Press, Oxford, 1989, pp. 54 and 180. 23 B. Bak, D. Christensen, L. Hansen-Nygard and J. Rastrup- Andersen, J. Mol. Spectrosc., 1961, 7, 58; W. R. Harsbarger and S. H. Bauer, Acta Crystallogr., Sect. B, 1970, 26, 1010. 24 A. Messerschmidt, in Bioinorganic Chemistry of Copper, eds. K. D. Karlin and Z. Tykelar, Chapman and Hall, New York, 1993, pp. 471–484. 25 (a) J. A. Tiethof, J. K. Stalick, P. W. R. Corfield and D. W. Meek, J. Chem. Soc., Chem. Commun., 1972, 1141; (b) A. Müller and U. Schimanski, Inorg. Chim. Acta, 1983, 77, L187; (c) A. Müller, F. W. Baumann, H. Bögge, M. Römer, E. Krickemeyer and K. Schmitz, Angew. Chem., Int. Ed. Engl., 1984, 23, 632; (d ) C. P. Rao, J. R. Dorfman and R. H. Holm, Inorg. Chem., 1986, 25, 428; (e) E. Hermann, R. Richter and Nguyen thi thu Chau, Z. Anorg. Allg. Chem., 1997, 623, 403. 26 (a) P. Hubberstey and C. E. Russel, J. Chem. Soc., Chem. Commun., 1995, 959; (b) P. L. Jones, J. C. JeVery, J. P. Maher, J. A. McCleverty, P. H. Rieger and M. D. Ward, Inorg. Chem., 1997, 36, 3088. 27 F. A. Cotton, X. Feng, M. Matusz and R. Bli, J. Am. Chem. Soc., 1988, 110, 7077 and refs therein. 28 (a) H. L. Aalten, G. van Koten, K. Goubitz and C. H. Stam, J. Chem. Soc., Chem. Commun., 1985, 1252; (b) H. C. Kang, Y. Do, C. B. Knobler and M. F. Hawthorne, Inorg. Chem., 1988, 27, 1716; (c) M. D. Janssen, M. A. Corsten, A. L. Spek, D. M. Grove and G. van Koten, Organometallics, 1996, 15, 2810. 29 P. W. Atkins, Physical Chemistry, Oxford University Press, 2nd edn., 1982, p. 268. 30 A. L. Balch, Prog. Inorg. Chem., 1994, 41, 239 and refs therein. 31 H. Günther, NMR Spectroscopy: Basic Principles, Concepts, and Applications in Chemistry, 2nd edn., Wiley, New York, 1992, p. 344. 32 J. M. GriYng and L. F. Salisbury, J. Am. Chem. Soc., 1948, 70, 3416. 33 W. Gee, R. A. Shaw and B. C. Smith, Inorg. Synth., 1967, 9, 19. 34 G. J. Kubas, Inorg. Synth., 1976, 19, 90. 35 G. M. Sheldrick, SHELXL 93, Program for Crystal Structure Refinement, University of Göttingen, 1993. Received 7th May 1998; Paper 8/03440K

ISSN:1477-9226    

DOI:10.1039/a803440k

出版商:RSC    

年代:1998

数据来源: RSC

摘要:

DALTON J. Chem. Soc., Dalton Trans., 1997, Pages 2865–2868 2865 Covalent radii of four-co-ordinate copper(I), silver(I) and gold(I): crystal structures of [Ag(AsPh3)4]BF4 and [Au(AsPh3)4]BF4 Upendra M. Tripathi, Andreas Bauer and Hubert Schmidbaur * Anorganisch-chemisches Institut der Technischen Universität München, Lichtenbergstrasse 4, D-85747 Garching, Germany The complexes [Ag(AsPh3)4]BF4 and [Au(AsPh3)4]BF4 were prepared from AgBF4 and 4 equivalents of AsPh3, and from equimolar quantities of [Au(AsPh3)Cl] and AgBF4 and 3 equivalents of AsPh3, respectively, in dichloromethane solution.Single crystals of the two compounds are isomorphous (trigonal, space group R3� , Z = 6) and contain cations with a tetrahedral Ag/Au]As4 core. From the Ag/Au]As distances measured at 199 K the covalent radii of four-co-ordinate silver(I) and gold(I) have been calculated using an accepted standard covalent radius for four-co-ordinate arsenic(III), r(AsIII) = 1.20 Å; r(AuI) = 1.37 Å is found to be 6% smaller than r(AgI) = 1.46 Å.This contraction reflects the strong influence of relativistic effects on atomic radii. From other data, r(CuI) for four-co-ordinate copper is estimated to be 1.29 Å. Owing to a current debate about the relevance of relativistic effects for chemistry 1 there is growing interest in reliable structural data of compounds of the elements for which this effect is expected to be particularly pronounced. Gold is considered the ‘relativistic element’ par excellence, and therefore its atomic and molecular parameters are the subject of scrutiny in both theoretical calculations and experimental studies.A recent investigation 2 of the structural chemistry of standard two-co-ordinate phosphine complexes of copper(I), silver(I) and gold(I) provided convincing evidence that the data on the covalent radii of the coinage metals in many handbooks and textbooks should be revised, with gold(I) definitely smaller than silver(I), and copper(I) as the smallest metal atom.These data are based on accurate X-ray diffraction studies carried out (1) under strictly comparable experimental conditions, (2) on perfectly isomorphous single crystals and (3) of compounds with the same composition and stoichiometry (ligands, counter ions). The radius of gold(I) was found to be almost 7% smaller than the radius of silver(I), agreeing very well with calculated data obtained in theoretical treatments including relativistic effects.Several other groups have since rightly pointed out that there was scattered evidence in many of the previous papers dealing with one or the other aspect of the structural chemistry of the coinage metals which can now be taken as support of the more recent findings. It was also noted 2 that the new data are only valid for the two-co-ordinate state of the univalent metals, and that studies of the situation with higher co-ordination numbers would be highly desirable.Directed by Bruce et al.3 we discovered that there was already one set of isomorphous compounds in the literature, where CuI, AgI and AuI are three-co-ordinate. Comparison of the data shows that the radii are again Cu smaller than Au smaller than Ag, with M]P bonds very similar in length as in the twoco- ordinate cases. It therefore appeared that at least for coordination numbers two and three the results are in excellent agreement. Four-co-ordinate complexes of gold(I) with monodentate Group 5 donor ligands are rare,4,5a,b and therefore comparative studies with analogous compounds of copper(I) and silver(I) are not possible for the most common sets of ligands. In an early, very careful study Jones 4 showed that a representative cation such as [Au(PPh3)4]1 appears in very different structures in salts with the [BPh4]2 anion, none of which is really strictly four-co-ordinate.On the other hand, [Cu(PPh3)4]1 and [Ag(PPh3)4]1 are both truly four-co-ordinate species in their isomorphous perchlorate salts,6 although there are slight distortions associated with the local three-fold symmetry of the cations.The [Ag(PPh3)4]1 cation was also structurally characterized in the nitrate 7 and hexafluorophosphate 8,9 salts which are again isomorphous with the perchlorate salts, and there is also an isomorphous [Cu(PPh3)4]1PF6 2 salt.9a Yet another example, from the silver series, was encountered 10 in salts [Ag(PPh3)4]1[SnPh2(NO3)2(Cl,NO3)]2, but markedly different distortions of the cation make comparisons less meaningful for these compounds.Compounds [CuL4]ClO4 with L = PPh3, AsPh3 and SbPh3 were prepared, but their structures have not been determined.9b Where determined, the average M]P distances in all these Ph3P complexes show silver to be much larger than copper, but there was no suitable species available for a comparison with gold. The only structurally confirmed homoleptic compound5 of the type [Au(PR3)4]1X2, with four independent tertiary phosphines, is [Au(PMePh2)4]1PF6 2, but for this example the structures of the copper and silver analogues are not known.There is reason to believe that compounds with the cation [Au(PPh3)4]1 are actually unstable owing to steric hindrance and poor acceptor properties of the two- and three-co-ordinate precursor complexes, and will therefore not be available for comparison. In the family of the tertiary arsine complexes the situation was less satisfactory in that structural data of homoleptic four-co-ordinate complexes were only known for silver: [Ag- (AsPh3)4]1 was structurally characterized 11,12 with the anions [SnPh2(NO3)2(Cl,NO3)]2 and [Sn2Ph2(NO3)4(OH)2(MeCN)2]22.These are isomorphous with each other, and also with the PPh3 analogues. The perchlorate salt with the cation [Au(AsPh3)4]1 was prepared by Parish et al.13 and investigated by 197Au Mössbauer spectroscopy (at 4 K).From the zero quadrupole splitting of the gold ‘resonance’ (isomeric shift: 20.39 mm s21 relative to gold foil) the authors concluded that the metal atom is in a highly symmetrical, most probably tetrahedral, environment in this complex, but the structure has not been determined. In the present paper we now report the synthesis and structure of [Au(AsPh3)4]1BF4 2 and its isomorphous silver(I) analogue. Our results provide a unique chance unambiguously to determine the relative covalent radii of the two heavier coinage metals in their four-co-ordinate state.It should be2866 J. Chem. Soc., Dalton Trans., 1997, Pages 2865–2868 noted that [Au(SbPh3)4]1 is also known and can be considered for further comparative studies.14–16 Results The compounds [Ag(AsPh3)4]BF4 and [Au(AsPh3)4]BF4 are readily synthesized from the reaction of an excess of triphenylarsine and the metal tetrafluoroborates [equations (1) and (2)]. 4 AsPh3 1 AgBF4 æÆ [Ag(AsPh3)4]1 BF4 2 (1) 3 AsPh3 1 [(AsPh3)AuCl] 1 AgBF4 æÆ [Au(AsPh3)4]1 BF4 2 1 AgCl (2) For this purpose, gold(I) tetrafluoroborate is prepared in situ from (triphenylarsine)gold(I) chloride and AgBF4.The products are obtained in high yield as colourless crystals with high melting points [299–300 8C (Ag), 268–269 8C (Au), with decomposition], stable to air and moisture, soluble in dichloromethane, trichloromethane and tetrahydrofuran, but insoluble in diethyl ether and hydrocarbon solvents.The solutions in CDCl3 show a single set of phenyl resonances in the 1H and 13C NMR spectra, and microanalysis data confirm the proposed composition (see Experimental section). In order to rule out isomorphous substitution of gold by silver in [Au(AsPh3)4]BF4, which was prepared using AgBF4 [equation (2)], the samples were analyzed for silver, but no such impurities were found. Single crystals were grown by layering dichloromethane solutions with diethyl ether. At 199 K these crystals are isomorphous [trigonal, space group R3� (no. 148), Z = 6] with very Table 1 Crystallographic data for [Ag(AsPh3)4]1 BF4 2 1 and [Au- (AsPh3)4]1 BF4 2 2 Compound Empirical formula M Crystal system Space group a/Å b/Å c/Å a/8 b/8 g/8 U/Å3 rcalc/g cm23 Z F(000) m(Mo-Ka)/cm21 T/ 8C Diffractometer Scan type hkl Range Measured reflections Unique refions Used reflections Rint Refined parameters H-atoms (found/calc.) Absorption correction Tmin, Tmax R1 a [Fo > 4s(Fo)] wR2 a (used reflections) Weighting scheme a rfin(max, min)/e Å23 1 C72H60AgAs4BF4 1419.56 Trigonal R3� (no. 148) 14.291(1) 14.291(1) 51.456(6) 90 90 120 9101.1(14) 1.542 6 4272 25.3 274 Enraf-Nonius CAD4 w–q 217 < h < 0, 0 < k < 17, 263 < l < 63 6920 3981 3969 0.0502 266 0/60 Empirical 0.8156, 0.9978 0.0502 0.1154 a = 0.0409, b = 70.7311 10.79, 20.60 2 C72H60As4AuBF4 1508.66 Trigonal R3� (no. 148) 14.245(1) 14.245(1) 51.467(3) 90 90 120 9044.2(6) 1.662 6 4464 47.7 274 Enraf-Nonius CAD4 w 0 < h < 17, 217 < k < 0, 263 < l < 63 8372 3952 3952 0.0300 254 0/60 DIFABS17 0.942, 1.000 0.0407 0.0887 a = 0.0000, b = 222.8159 13.78, 22.88 b a R1 = S ( |Fo| 2 |Fc| )/S|Fo|, wR2 = [Sw(Fo 22Fc 2)2]/S[w(Fo 2)2]� �� , w = 1/2s2(Fo 2) 1 (aP)2 1 bP, P = (Fo 2 1 2Fc 2)/3.b Residual electron densities located at the Au atom. similar dimensions of the unit cells (Table 1). The lattice is composed of tetrafluoroborate anions and tetrakis(triphenylarsine) metal(I) cations, which show no conspicuous sub-van der Waals contacts.Crystallographically the cations have only three-fold symmetry, but in both cases (M = Ag or Au) the structure of the MAs4 cores deviates only very slightly from regular tetrahedral symmetry. There are also no anomalies regarding the dimensions of the triphenylarsine ligands. The cations of the silver compound show some disorder in the crystal, but the site occupation factor (s.o.f.) for the second orientation is only 7% and could be accounted for in a satisfactory way in the refinement.The central silver atom is not disordered (s.o.f. 100%). For both compounds the boron atoms of the anions are located on 3� centers, and the anions are therefore disordered in an analogous manner. The high symmetry of the environment of the gold atoms in the lattice of [Au(AsPh3)4]BF4 is in excellent agreement with the Mössbauer results (see above).13 The low electrical field gradient at the centre of the AuAs4 tetrahedron leads to the observed zero quadropole splitting. Discussion The structural data of the [Ag(AsPh3)4]1 cation in the BF4 2 salt (Fig. 1) agree very well with the geometry of the same cation in the three stannates already in the literature.11,12 This agreement gives confidence that the data are indeed intrinsic values not influenced significantly by the environment in the crystal. The average Ag]As distance in the BF4 2 salt [this work: 2.6546(6) Å, from Ag]As(1) 2.6451(10) and Ag]As 2.6578(5) Å (×3)] is in the range of the standard deviations for the other three examples and is perhaps presently the most accurate value.Deviations of the As]Ag]As bond angles [As]Ag]As(1) 109.01(2)8 (×3) and As]Ag]As9 109.92(2)8 (×3)] from the standard value for the ideal tetrahedron [109.488] are very small indeed, suggesting again that there is no meaningful distortion induced by neighbouring components of the lattice.For the dimensions of the [Au(AsPh3)4]1 cation in the BF4 2 salt (Fig. 2) there are no reference data from salts with other anions. The average Au]As distance [2.5827(7) Å, from Au]As(1) 2.5663(10) and Au]As 2.5882(6) (×3)] is smaller than the Ag]As distance in the silver-centered cation (above) by 0.072 Å. Assuming that the covalent radius of arsenic is the same for both compounds, and using textbook datum of Fig. 1 Structure of the cation [Ag(AsPh3)4]1 in complex 1 (ORTEP,18 50% probability ellipsoids; phenyl hydrogen atoms omitted for clarity).Selected bond lengths (Å) and angles (8): Ag]As(1) 2.6451(10), Ag]As 2.6578(5); As]Ag]As(1) 109.01(2), As]Ag]As9 109.92(2)J. Chem. Soc., Dalton Trans., 1997, Pages 2865–2868 2867 r(As) = 1.20 Å for four-co-ordinate arsenic as the presently accepted value,19 the covalent radius of four-co-ordinate gold(I) (1.366 Å) is thus found to be ca. 6% smaller than the covalent radius of four-co-ordinate silver(I) (1.455 Å).This result agrees well with the trend observed in two- and three-co-ordinate complexes (Introduction), which clearly indicates that silver is the larger of the two metals, and confirms the data of pertinent calculations.20,21 In the absence of structural data of an isomorphous copper(I) arsenic compound, no direct comparison of the radii of all three coinage metals can be made. The data of several pairs of Cu/Ag compounds with other ligands 5–7,9 leave no doubt, however, that copper(I) is the smallest of the coinage metals also in a four-co-ordinate environment.The covalent radius for CuI is estimated to be 1.29 Å. With this entry, the radii of the univalent Group 11 metals should be tabulated in reference treatises as: (a) two-co-ordinate: 2 Cu: 1.13, Ag: 1.33, Au: 1.25 Å. (b) four-co-ordinate: Cu: 1.29, Ag: 1.46, Au: 1.37 Å. These values are based here on currently accepted covalent radii of four-coordinated PIII (1.11 Å) and AsIII (1.20 Å), but similar data are also found for complexes with isocyanide 22 or ketimine ligands, 23 where carbon or nitrogen atoms are the donor sites, respectively.Experimental Stringent precautions were taken to exclude moisture from the solvents and reactants, as well as from the glassware employed throughout the investigation. All experiments were carried out under a purified nitrogen atmosphere. The compound [Au(AsPh3)Cl] was prepared by following the literature procedure.24 Other starting materials, AsPh3 and AgBF4, were commercially available.Proton (399.8 MHz) and 13C-{1H} (100.5 MHz) NMR spectra were recorded on a JEOL GX 400 Fourier-transform NMR spectrometer using SiMe4 as internal standard. Microanalyses of the compounds were performed in-house by combustion and atomic absorption spectroscopic (AAS) techniques. Preparations Tetrakis(triphenylarsine)silver(I) tetrafluoroborate, [Ag(As- Ph3)4]BF4. To a suspension of AgBF4 (66 mg, 0.34 mmol) in dichloromethane (20 cm3), AsPh3 (415 mg, 1.36 mmol) was added and the reaction mixture was stirred for 3 h.After removing 10 cm3 of dichloromethane under vacuum, the product Fig. 2 Structure of the cation [Au(AsPh3)4]1 in complex 2 (ORTEP, 50% probability ellipsoids; phenyl hydrogen atoms omitted for clarity). Selected bond lengths (Å) and angles (8): Au]As(1) 2.5663(10), Au]As 2.5882(6); As]Au]As(1) 109.36(2), As]Au]As9 109.58(2) (433 mg, 90%) was obtained as colourless crystals by layering the resulting solution with diethyl ether (20 cm3).M.p. 299– 300 8C (decomp.) (Found: C, 60.78; H, 4.43; Ag, 7.70. C72H60- AgAs4BF4 requires C, 60.91; H, 4.22; Ag, 7.60%). NMR: 1H (CDCl3) d 7.35 (4 H, t, JHH = 7.32, para-Ph), 7.07 (8 H, t, JHH = 7.7, meta-Ph) and 7.01 (8 H, d, JHH = 7.0 Hz, ortho-Ph). 13C-{1H} (CDCl3) d 134.78 (s, ipso-C), 133.28 (s, para-C), 129.82 (s, meta-C) and 129.26 (s, ortho-C). Tetrakis(triphenylarsine)gold(I) tetrafluoroborate, [Au(As- Ph3)4]BF4.A solution of AgBF4 (32.6 mg, 0.16 mmol) in tetrahydrofuran (thf) (5 cm3) was added with stirring to a clear solution of [Au(AsPh3)Cl] (90 mg, 0.16 mmol) in dichloromethane (10 cm3) and stirring was continued for 15 min at room temperature. A solution of AsPh3 (153 mg, 0.50 mmol) in dichloromethane (10 cm3) was then added to the resulting reaction mixture and stirred at ambient temperature for 3 h. Separation of precipitated AgCl by filtration, followed by removal of volatiles under reduced pressure (25 8C, 0.8 Torr ª 106.6 Pa) afforded the product (237 mg, 95%).The product was crystallised by dissolving in dichloromethane and layering with diethyl ether. M.p. 268–269 8C (decomp.) [Found: C, 57.07; H, 4.06; Au, 13.10. The compound contains no significant amounts of silver (as determined by AAS). C72H60As4AuBF4 requires: C, 57.33; H, 3.98; Au, 13.06%]. NMR: 1H (CDCl3) d 7.39 (4 H, t, JHH = 7.5, para-Ph), 7.15 (8 H, t, JHH = 7.5, meta-Ph) and 7.06 (8 H, d, JHH = 7.3 Hz, ortho-Ph). 13C-{1H } (CDCl3) d 135.01 (s, ipso-C), 133.09 (s, para-C), 130.30 (s, meta-C) and 129.38 (s, ortho-C). Crystallography Suits of the compounds were sealed into glass capillaries and used for measurement of precise cell constants and intensity data collection. During data collection, three standard reflections were measured periodically as a general check of crystal and instrument stability. No significant changes were observed for either compound.Diffraction intensities were corrected for Lorentz-polarization and absorption effects (empirically). The structures were solved by direct methods and refined by full-matrix least-squares calculations 25 against F 2. The thermal motion of all non-hydrogen atoms was treated anisotropically. All hydrogen atoms were calculated in idealized positions and allowed to ride on their corresponding carbon atom. Their isotropic thermal parameters were tied to that of the adjacent carbon atom by a factor of 1.5.The boron atoms (s.o.f. 0.17) of the tetrafluoroborate anions are located at centres of 3� symmetry and the anions are therefore crystallographically disordered. The cation in the silver compound is disordered in two positions with very different site occupation factors (s.o.f. 0.93 and 0.07, respectively). The silver atom shows no sign of disorder (s.o.f. 1). For the molecule with the low s.o.f. only the arsenic atoms could be found and successfully refined.Important interatomic distances and angles are given in the corresponding figure captions. Experimental details are summarized in Table 1. CCDC reference number 186/627. Acknowledgements This work was supported by Deutsche Forschungsgemeinschaft and Fonds der Chemischen Industrie. U. M. T. is grateful to the Alexander von Humboldt Foundation for a research fellowship. Support by Degussa AG and Heraeus GmbH through the donation of chemicals is acknowledged.Mr. J. Riede is thanked for collecting the X-ray data sets. References 1 N. Kaltsoyannis, J. Chem. Soc., Dalton Trans., 1997, 1 and refs. therein.2868 J. Chem. Soc., Dalton Trans., 1997, Pages 2865–2868 2 A. Bayler, A. Schier, G. A. Bowmaker and H. Schmidbaur, J. Am. Chem. Soc., 1996, 118, 7006; (b) G. A. Bowmaker, H. Schmidbaur, S. Krüger and M. Rösch, Inorg. Chem., 1997, 36, 1754. 3 M. I. Bruce, M. L. Williams, J. M. Patrick, B. W. Skelton and A.H. White, J. Chem. Soc., Dalton Trans., 1986, 2557. 4 P. G. Jones, J. Chem. Soc., Chem. Commun., 1980, 1031. 5 (a) R. C. Elder, E. H. K. Zeiher, M. Onady and R. R. Whittle, J. Chem. Soc., Chem. Commun., 1981, 900; (b) S. J. Berners-Price, L. A. Colquhoun, P. C. Healy, K. A. Byriel and J. V. Hanna, J. Chem. Soc., Dalton Trans., 1992, 3357. 6 L. M. Engelhardt, C. Pakawatchi, A. H. White and P. C. Healy, J. Chem. Soc., Dalton Trans., 1985, 125. 7 P. F. Barron, J. C. Dyason, P.C. Healy, L. M. Engelhardt, B. W. Skelton and A. H. White, J. Chem. Soc., Dalton Trans., 1986, 1965. 8 F. A. Cotton and R. L. Luck, Acta Crystallogr., Sect. C, 1989, 45, 1222. 9 (a) G. A. Bowmaker, P. C. Healy, L. M. Engelhardt, J. D. Kildia, B. W. Skelton and A. H. White, Aust. J. Chem., 1990, 43, 1697; (b) A. Bell, R. A. Walton, D. A. Edwards and M. A. Poulter, Inorg. Chim. Acta, 1985, 104, 171. 10 C. Pelizzi, G. Pelizzi and P. Tarasconi, J. Organomet. Chem., 1984, 277, 29. 11 M. Nardelli, C. Pelizzi and P. Tarasconi, J. Chem. Soc., Dalton Trans., 1985, 321. 12 A. Bonardi, A. Cantoni, C. Pelizzi, G. Pelizzi and P. Tarasconi, J. Organomet. Chem., 1991, 402, 281. 13 R. V. Parish, O. Parry and C. A. McAuliffe, J. Chem. Soc., Dalton Trans., 1981, 2098. 14 P. G. Jones, Z. Naturforsch., Teil B, 1982, 37, 937. 15 P. G. Jones, Acta Crystallogr., Sect. C, 1992, 48, 1487. 16 J. Vicente, A. Arcas, P. G. Jones and J. Lantner, J. Chem. Soc., Dalton Trans., 1990, 451. 17 N. Walker and D. Stuart, Acta Crystallogr., Sect A, 1983, 39, 158. 18 C. K. Johnson, ORTEP, Report ORNL-5138, Oak Ridge National Laboratory, Oak Ridge, TN, 1976. 19 N. N. Greenwood and A. Earnshaw, Chemistry of the Elements, Pergamon Press, Oxford, 1984, p. 642. 20 P. Pyykkö, Relativistic Theory of Atoms and Molecules, Springer- Verlag, Berlin, 1986. 21 M. S. Liao and W. H. E. Schwarz, Acta. Crystallogr., Sect. B, 1994, 50, 9. 22 W. Schneider, K. Angermaier, A. Sladek and H. Schmidbaur, Z. Naturforsch., Teil B, 1996, 51, 790. 23 W. Schneider, A. Bauer and H. Schmidbaur, J. Chem. Soc., Dalton Trans., 1997, 415. 24 A. D. Westland, Can. J. Chem., 1969, 47, 4135. 25 G. M. Sheldrick, SHELXL 93, University of Göttingen, 1993. Received 15th April 1997; Paper 7/0258

ISSN:1477-9226    

DOI:10.1039/a702582c

出版商:RSC    

年代:1997

数据来源: RSC

摘要:

DALTON FULL PAPER J. Chem. Soc., Dalton Trans., 1998, Pages 2867–2871 2867 Synthesis, structure and spectroscopic properties of [Cu3(Ï-dpnapy)3- (CH3CN)][ClO4]3?CH3CN (dpnapy 5 7-diphenylphosphino-2,4- dimethyl-1,8-naphthyridine) with a linear copper atom array Wing-Han Chan,a Shie-Ming Peng b and Chi-Ming Che *,a a Department of Chemistry, The University of Hong Kong, Pokfulam Road, Hong Kong b Department of Chemistry, National Taiwan University, Taipei, Taiwan The co-ordination chemistry of 7-diphenylphosphino-2,4-dimethyl-1,8-naphthyridine (dpnapy) with CuI has been examined.Reaction of [Cu(CH3CN)4][ClO4] with dpnapy in CH3CN aVorded [Cu3(m-dpnapy)3(CH3CN)][ClO4]3 1[ClO4]3. The crystal structure of 1[ClO4]3?CH3CN reveals a linear Cu]Cu]Cu array with both trigonal and tetrahedral co-ordination modes for the copper atoms. The intramolecular Cu]Cu distances of 2.449(2) and 2.721(2) Å suggest that only two of the copper atoms have a bonding interaction.Complex 1 reacts with triphenylphosphine (PPh3) and 2,29-bipyridine (bpy) to give [Cu(bpy)(dpnapy)2][ClO4] 2[ClO4] and [Cu2(m-dpnapy)3][ClO4]2 3[ClO4]2, respectively. Spectroscopic properties of the complexes have been examined. There has been considerable interest in using polyfunctional ligands for the construction of heterometallic complexes. In this context, rigid pyridylphosphine ligands with short bite distances have attracted our attention since they can support linear chains or more complex arrays of metal atoms.1 The ligand dpnapy (7-diphenylphosphino-2,4-dimethyl-1,8-naphthyridine), reported by Lo Schiavo,2a has a short bite distance and the combined structural features of the binucleating 1,8-naphthyridine (napy) and 2-(diphenylphosphino)pyridine (dppy) ligands.The possible co-ordination modes of dpnapy are shown in Scheme 1. Lo Schiavo and co-workers have studied the reactions of dpnapy with IrI, RhI, PtII and PdII and the coordination modes I–V (Scheme 1) were found.2 However, no trinuclear metal complex with dpnapy (VI) has been reported.Herein is described the co-ordination chemistry of dpnapy with CuI, showing the formation of a linear Cu]Cu]Cu array supported by this ligand. Experimental Materials The salt [Cu(CH3CN)4][ClO4] and dpnapy were prepared according to literature methods.2a,3 2,29-Bipyridine (bpy) and triphenylphosphine were purchased from Aldrich. All reactions were performed under a nitrogen atmosphere unless otherwise stated.Solvents for emission measurements were of spectroscopic grade and solutions for photochemical experiments were degassed by at least four freeze–pump–thaw cycles. Instrumentation Proton, 13C and 31P NMR spectra were recorded on a DPX-500 Bruker spectrometer and SiMe4 was added as internal standard; FAB and ESI mass spectra were collected on a Finnigan MAT 95 high-resolution mass spectrometer. Elemental analyses were performed by Butterworth Laboratories Ltd.Cyclic voltammetry was performed on a Princeton Applied Research (PAR) model 273 potentiostat-galvanostat. Tetrabutylammonium hexafluorophosphate (Aldrich) in acetonitrile was used as supporting electrolyte. The UV/VIS absorption spectra were recorded on a Milton Roy Spectronic 3000 diode-array spectrophotometer. Emission spectra were recorded on a SPEX Fluorolog-2-Model 1680 spectrophotometer. Preparation of complexes [Cu3(Ï-dpnapy)3(CH3CN)][ClO4]3 1[ClO4]3.The salt [Cu- (CH3CN)4][ClO4] (0.33 g, 1.0 mmol) was suspended in acetonitrile (25 ml) and a solution of dpnapy (0.34 g, 1.0 mmol) in dichloromethane (5 ml) was added dropwise. The solution was stirred at room temperature for 1 h. The solvent was removed in vacuo leaving an orange solid. Orange crystals of 1[ClO4]3?CH3- CN (1.12 g, 70%) were obtained by diVusion of diethyl ether into an acetonitrile solution (Found: C, 56.6; H, 4.0; N, 7.0. Calc. for C70H63Cl3Cu3N8O12P3: C, 56.2; H, 4.0; N, 7.0%).[Cu(bpy)(dpnapy)2][ClO4] 2[ClO4]. A mixture of 1[ClO4]3 (1.34 g, 1.0 mmol) and bpy (0.20 g, 1.2 mmol) in dichloromethane (25 ml) was stirred at room temperature for 1 h. The mixture gradually turned from orange to clear yellow. The solvent was removed in vacuo leaving an orange solid. Recrystallization of the crude product from an acetonitrile–diethyl ether solution aVorded a mixture of red and yellow crystals. The red crystals were identified as [Cu(bpy)2][ClO4] [0.06 g, 20%, FAB MS: m/z = 375 (M1)] and the yellow crystals as 2[ClO4] [0.6 g, 60% (Found: C, 64.3; H, 4.6; N, 8.5.Calc. for C54H46ClCu- N6O4P2: C, 64.6; H, 4.6; N, 8.4%)]. [Cu2(Ï-dpnapy)3][ClO4]2 3[ClO4]2. A mixture of 1[ClO4]3 (1.34 g, 1.0 mmol) and PPh3 (0.32 g, 1.2 mmol) in dichloromethane (25 ml) was stirred at room temperature for 1 h. The mixture gradually turned from orange to clear yellow. The solvent was concentrated to ca. 5 ml. Recrystallization of the crude product from a dichloromethane–diethyl ether solution aVorded a mixture of orange and yellow crystals.The orange crystals were identified as [Cu(dpnapy)(PPh3)2]ClO4 [0.32 g, 31%, ESI MS: m/z = 930 (M1) (Found: C, 68.3; H, 4.6; N, 2.5. Scheme 1 Possible co-ordination modes of dpnapy2868 J. Chem. Soc., Dalton Trans., 1998, Pages 2867–2871 Table 1 Crystallographic data for 1[ClO4]3?CH3CN and 2[ClO4] Complex Formula M Crystal system Space group a/Å b/Å c/Å b/8 U/Å3 Z Dc/g cm23 m(Mo-Ka)/cm21 Crystal size/mm F(000) 2qmax/8 No.of unique reflections No. of observed reflections (No) No. of variables (Nv) R Rw Goodness of fit Residual electron density/e Å23 1[ClO4]3?CH3CN C70H63Cl3Cu3N8O12P3 1598.2 Monoclinic P21/n 13.804(3) 38.427(3) 14.926(2) 116.60(2) 7079(2) 4 1.500 11.34 0.13 × 0.25 × 0.45 3279 45 9227 4542 [I > 2s(I)] 892 0.049 0.046 1.55 10.56, 20.35 2[ClO4] C54H46ClCuN6O4P2 1003.9 Monoclinic Pc 10.253(2) 10.368(2) 23.487(2) 95.23(2) 2486.3(7) 2 1.341 5.55 0.20 × 0.40 × 0.50 1042 50 4382 3120 [I > 2s(I)] 613 0.042 0.039 1.58 10.38, 20.35 R = S||Fo| 2 Fc||/S|Fo|, Rw = [Sw(|Fo| 2 |Fc|)2/Sw|Fo|]� �� , S = [Sw(|Fo| 2 |Fc|)2/No 2 Nv]� �� , w = [s2(F ) 2 0.0001F2]21. Calc.for C58H49ClCuN2O4P3: C, 67.7; H, 4.8; N, 2.7%)] and the yellow crystals as 3[ClO4]2?2H2O?3CH3OH [0.86 g, 58% (Found: C, 54.3; H, 4.6; N, 5.5. Calc. for C69H73Cl2Cu2N6O13P3: C, 55.8; H, 5.0; N, 5.7%)]. X-Ray data collection and refinement Information concerning the conditions for crystallographic data collection and structure refinement is summarized in Table 1.DiVraction data for 1[ClO4]3?CH3CN and 2[ClO4] were collected on an Enraf-Nonius diVractometer with monochromatic Mo-Ka radiation (l = 0.7107 Å).4 Intensity data were collected at 298 K using the w-2q scan technique. Three standard reflections monitored every hour showed an intensity variation < 2%. The structures were solved by the Patterson method and refined by full-matrix least-squares refinement using the NRCVAX program.5 Complex 1 has a long axis and three perchlorates in an asymmetric unit, which leads to fewer observed reflections (50% observed).Complex 2 has a space group Pc based on the facts that (1) the intensity distribution indicates that the molecule is non-centrosymmetric, and (2) after successful resolution of the structure the complex cation exhibits a noncrystallographic two-fold axis [passing through the midpoint of N(1)N(2), Cu and the mid-point of P(1)P(2)].The two-fold axis does not parallel the b axis and is impossible as a crystallographic two-fold axis. The ratios of data to parameters for complexes 1 and 2 are low (ª5 : 1), but both structure analyses are sound on the basis of low R values, reasonable thermal parameters and low electron residues. DiVraction data of 3[ClO4]2?2H2O?3CH3OH were collected on a Rigaku RAXIS IIc diVractometer at 293 K using w–2q scans technique.Absorption collection was based on ABSCOR. 6 The structure was solved by direct methods and refined by full-matrix least squares using SHELXTL 93.7 Crystal data for C69H73Cl2Cu2N6O13P3, M = 1485.2, orthorhombic, space group Pbcn (no. 6)(6), b = 16.578(3), c = 30.500(6) Å, U = 14 010(5) Å3, Z = 8, Dc = 1.408 g cm23, m(Mo- Ka) = 8.18 cm21, crystal dimension = 0.20 × 0.16 × 0.14 mm, F(000) = 6160, index range 0 < h < 33, 0 < k < 20, 0 < l < 37, 2qmax = 528, unique reflections = 11 460, reflections with F > 2.0s(F) = 3656, variables = 792, R = 0.094, Rw = 0.301, goodness of fit = 0.951, residual electron density = 0.51, 20.38 e Å23.Though the R and Rw values are high (due to large number of co-crystallized solvents), the bond distances and angles appear to be reasonable. CCDC reference number 186/1072. Results and Discussion Procedures for the preparation of complexes 1–3 are depicted in Scheme 2. Complex 1 is readily obtained by the reaction of [Cu(CH3CN)4][ClO4] with a stoichiometric amount of dpnapy in acetonitrile.It is one of the few trinuclear CuI complexes with a linear copper atom array.8–11 Two notable literature examples are [Cu3(bpd)2]2 [bpd = N,N9-bis(p-tolylsulfonyl)pyridine-2,6- diaminato] and [Cu3(tolN5tol)3] (HN5 = 1,4-pentaazadiene, tol = p-tolyl),10,11 both of which have short bite bridging Scheme 2 Preparation of complexes 1–3: i [Cu(CH3CN)4][ClO4], acetonitrile; ii bpy, dichloromethane; iii PPh3, dichloromethane at room temperatureJ.Chem. Soc., Dalton Trans., 1998, Pages 2867–2871 2869 ligands. We conceive that besides the stereochemistry of the bridging ligands, the weakly attractive CuI]CuI interaction is a driving force for the formation of a linear Cu]Cu]Cu array with short intramolecular metal–metal distances. This would be the case in 1 since a considerable coulombic repulsion has to be overcome in bridging the three CuI ions at short separations.Indeed, results of molecular orbital calculation also revealed the existence of weakly attractive forces between d10 metal ions.12,13 We envisaged that the co-ordinated acetonitrile in 1 would be labile and easily undergo substitution reaction. Treatment of 1 with bpy and PPh3 resulted in disintegration of the copper atom array with subsequent rearrangement to form 2 and 3. These reactions were accompanied by the formation of side products such as [Cu(bpy)2][ClO4] and [Cu(dpnapy)(PPh3)2][ClO4], respectively.It is likely that the three copper atoms in 1 experience strong coulombic repulsion, and cleavage of the trinuclear structure is facilitated through ligand substitution reactions. The structures of complex cations 1–3 have been determined Fig. 1 The 31P-{H} NMR spectra of 1[ClO4]3 in CD3CN at (a) 60, (b) 25 and (c) 260 8C Table 2 Selected 1H, 13C-{H} and 31P-{H} NMR spectroscopic data for complexes 1–3 at room temperature 1H NMR 13C-{H} NMR 31P-{H} NMR Complex 1a 2 a 3 b dpnapy b d2-Me 2.80 2.71 2.75, 2.80, 2.82 2.73 d4-Me 2.67 2.55 2.60, 2.69, 2.71 2.62 d2-Me 27.8 25.9 25.4, 27.4, 28.5 25.6 d4-Me 18.6 18.1 18.2, 18.3, 18.4 18.0 d 2.5, 5.3 3.8 2.0, 3.2, 4.1 21.1 a In CD3CN.b In CD2Cl2. by X-ray crystal analyses. All compounds are air-stable in the solid state, but slow decomposition has been observed in solutions at room temperature. Selected 1H, 13C and 31P NMR spectral data of the complexes are listed in Table 2.The 2-Me protons of dpnapy in 2 and in the free ligand have similar chemical shifts (d2-Me). However, significant downfield shifts are observed for those in 1 and 3. This is in accordance with the M]N (naphthyridyl) co-ordination in the latter two complexes. Variable-temperature 31P NMR spectroscopy of 1 (Fig. 1) reveals a fluxional behaviour in CD3CN. At room temperature, the complex exhibits two broad phosphorus signals at d 2.5 and 5.3. As the temperature increases, they gradually coalesce at d 3.55 (60 8C).By cooling to 260 8C several phosphorus resonances are observed. Addition of a stoichiometric amount of dpnapy has no notable eVect on the 31P NMR spectrum. This excludes the possibility of a ligand exchange reaction and the dynamic behaviour may be attributed to a switching-on and -oV process of the phosphine moieties (Scheme 3). The electrochemical properties of complexes 1–3 have been studied by cyclic voltammetry.All complexes exhibit irreversible oxidation waves. The voltammogram of 1 is characterized by two irreversible waves with Epa at 1.25 and 1.65 V (vs. SCE), whereas 2 and 3 exhibit a single peak at 1.0 V (broad) and 1.1 V, respectively. Spectroscopic properties The UV/VIS absorption spectra of 1–3 are characterized by absorptions at 320–328 nm [lmax/nm (e/104 M21 cm21) for 1: 328 (2.39), 2: 320 (1.33) and 3: 325 (1.88)]. For complex 1, a low energy absorption tail at 430–450 nm (e = 1.22 × 104 M21 cm21) is observed. Upon excitation at 350 nm, 1[ClO4]3 shows room-temperature emission at ca. 530 nm (lifetime 0.21 ms) in degassed acetonitrile.Cooling the solution to 77 K leads to an increase in emission intensity but no vibrational fine structure is recorded. The emission is assigned to the d(Cu) æÆ p*(dpnapy) MLCT excited state. At room temperature, the solid-state emission of 1 at 634 nm (lifetime 0.44 ms) is considerably red-shifted from the solution emission.We assign the solid-state emission to the excited state of a metal-centred ds* æÆ ps transition, where ds* refers to the antibonding combination of the 3dz2 orbitals and ps refers to the bonding combination of the 4s/4p orbitals (the Cu ? ? ? Cu ? ? ? Cu axis is taken as the z direction).14 Crystal structures Perspective drawings of the complex cations 1–3 are depicted in Figs. 2–4. Selected bond lengths and bond angles are listed in Tables 3–5.The three Cu atoms in 1 are held in close proximity and in a nearly linear array [Cu(1)]Cu(2)]Cu(3) angle 177.50(6) Å] by three bridging dpnapy ligands. The dpnapy ligands are in a head-to-head arrangement with the [P(1), P(2), P(3)], [N(1), N(3), N(5)] and [N(2), N(4), N(6)] planes almost parallel to each other. The atom Cu(1) adopts a distorted tetrahedral Scheme 3 Dynamic behaviour of 1[ClO4]3 in acetonitrile showing an on and oV switching of the phosphorus moieties2870 J.Chem. Soc., Dalton Trans., 1998, Pages 2867–2871 geometry with a co-ordinated acetonitrile molecule. Atoms Cu(2) and Cu(3) are three-co-ordinated and each is bonded to three pyridyl-nitrogen atoms in a distorted trigonal manner. It is noted that the CuI]N (acetonitrile) and CuI]N (dpnapy) distances are comparable, suggesting that the acetonitrile is weakly co-ordinated to the metal atom. Two distinct Cu]Cu distances are present in the complex, of which the shorter Cu(2)]Cu(3) distance [2.449(2) Å] appears to be comparable to those found in [Cu2(napy)2][ClO4]2 [2.506(2) Å],15 [Cu3(bpd)2]2 [2.466(1) and 2.468(1) Å] 10 and [Cu3(tolN5tol)3] [2.348(2) and 2.358(2)].11 We believe that there is metal–metal interaction between Cu(2) and Cu(3).The longer Cu(1)]Cu(2) distance of 2.721(2) Å is virtually identical with that observed in [Cu2(m-dppy)3(MeCN)]- [BF4]2.16 This can be indicative of no metal–metal interaction between the copper atoms. Complex 2 is mononuclear with the Cu atom co-ordinated to two P-monodentate dpnapy ligands and a chelating bipyridyl ring in a distorted tetrahedral geometry. The N]Cu]N angle sustained by bpy is 80.1(2)8.The Cu]P and Cu]N distances are similar to those in [Cu(m-bpym)(PPh3)2]2[ClO4]2 (bpym = bipyrimidine).17 As shown in Fig. 3, there is a p–p interaction between the naphthyridyl rings of two dpnapy ligands. The dihedral angle between the naphthyridyl planes is 8.37(2)8 and the closest inter-planar separation is 3.18(1) Å.This is comparable to the p–p stacking separation found in some organic sandwich compounds.18 The chemical connectivity of complex 3 has been established Fig. 2 A perspective drawing of the complex cation 1 with atomic numbering scheme, H atoms are omitted for clarity Table 3 Selected bond lengths (Å) and bond angles (8) for 1[ClO4]3? CH3CN Cu(1)]Cu(2) Cu(2)]Cu(3) Cu(1)]P(1) Cu(1)]P(2) Cu(1)]P(3) Cu(1)]N(7) Cu(2)]P(1) Cu(1)]Cu(2)]Cu(3) Cu(2)]Cu(1)]N(7) P(1)]Cu(1)]P(2) P(1)]Cu(1)]P(3) P(1)]Cu(1)]N(7) P(2)]Cu(1)]P(3) P(2)]Cu(1)]N(7) 2.721(2) 2.449(2) 2.315(3) 2.304(3) 2.327(3) 2.016(7) 3.017(3) 177.50(6) 174.2(2) 113.1(1) 116.8(1) 107.8(2) 111.2(1) 106.9(2) Cu(2)]N(1) Cu(2)]N(3) Cu(2)]N(5) Cu(3)]N(2) Cu(3)]N(4) Cu(3)]N(6) P(3)]Cu(1)]N(7) N(1)]Cu(2)]N(3) N(1)]Cu(2)]N(5) N(3)]Cu(2)]N(5) N(2)]Cu(3)]N(4) N(2)]Cu(3)]N(6) N(4)]Cu(3)]N(6) 2.033(6) 2.064(6) 2.029(7) 1.975(7) 2.050(7) 1.977(7) 99.8(2) 111.7(3) 127.6(3) 116.5(3) 113.3(3) 132.6(3) 113.6(3) by X-ray crystal analysis but the high Rw value of the structure precludes any precise discussion.As shown in Fig. 4, complex cation 3 displays a highly irregular structure. Two kinds of Cu atoms are found in the complex. Atom Cu(1) adopts a trigonal planar co-ordination while Cu(2) is distorted tetrahedral. The dpnapy ligands show three diVerent types of coordination geometry, and these are the II, III and V modes (Scheme 1). Conclusion The short bite dpnapy ligand reacts with CuI to form complexes that display various co-ordination modes.The structure of 1 is interesting as it features one of the few linear trimeric CuI complexes. An X-ray crystallographic study revealed that the three Cu atoms are arranged in a nearly linear array and are held in close proximity by the bridging dpnapy ligands. The Cu]Cu distance of 2.449(2) Å is even comparable to the shortest distances of 2.348(2) and 2.358(2) Å observed in [Cu3(tolN5tol)3].11 Fig. 3 A perspective drawing of the complex cation 2 with atomic numbering scheme, H atoms are omitted for clarity Table 4 Selected bond lengths (Å) and bond angles (8) for 2[ClO4] Cu(1)]P(1) Cu(1)]P(2) P(1)]Cu(1)]P(2) P(1)]Cu(1)]N(1) P(1)]Cu(1)]N(2) P(2)]Cu(1)]N(1) P(2)]Cu(1)]N(2) 2.267(2) 2.247(2) 114.40(6) 117.0(2) 109.0(2) 116.4(2) 115.1(2) Cu(1)]N(1) Cu(1)]N(2) N(1)]Cu(1)]N(2) Cu(1)]N(1)]C(5) Cu(1)]N(2)]C(6) N(2)]C(6)]N(5) N(1)]C(5)]N(4) 2.066(5) 2.073(5) 80.1(2) 114.1(4) 113.6(4) 115.7(6) 121.3(6) Table 5 Selected bond lengths (Å) and bond angles (8) for 3[ClO4]2? 2H2O?3CH3OH Cu(1)]N(4) Cu(1)]N(5) Cu(1)]P(1) Cu(2)]N(1) N(5)]Cu(1)]N(4) N(4)]Cu(1)]P(1) N(5)]Cu(1)]P(1) N(2)]Cu(2)]P(2) N(2)]Cu(2)]P(3) 2.106(7) 2.098(6) 2.227(3) 2.239(6) 108.6(2) 139.4(2) 111.8(2) 113.7(2) 118.9(2) Cu(2)]N(2) Cu(2)]P(2) Cu(2)]P(3) N(2)]Cu(2)]N(1) N(1)]Cu(2)]P(2) N(1)]Cu(2)]P(3) P(2)]Cu(2)]P(3) 2.160(7) 2.253(3) 2.277(2) 61.8(2) 112.0(2) 114.2(2) 121.4(2)J.Chem. Soc., Dalton Trans., 1998, Pages 2867–2871 2871 Fig. 4 A perspective drawing of the complex cation 3 with atomic numbering scheme, H atoms are omitted for clarity Acknowledgements We acknowledge support from the Research Grants Council of Hong Kong, The University of Hong Kong and the Croucher Foundation. References 1 A. Balch, Prog. Inorg. Chem., 1993, 41, 239. 2 (a) M. Grassi, G. D. Munno, F. Nicolo and S. Lo Schiavo, J. Chem. Soc., Dalton Trans., 1992, 2367; (b) S.Lo Schiavo, M. S. Sinicropi, G. Tresoldi, C. G. Arena and P. Piraino, J. Chem. Soc., Dalton Trans., 1994, 1517; (c) S. Lo Schiavo, G. D. Munno, F. Nicolo and G. Tresoldi, J. Chem. Soc., Dalton Trans., 1994, 3135; (d ) S. Lo Schiavo, M. Grasi, G. D. Munno, F. Nicolo and G. Tresoldi, Inorg. Chim. Acta, 1994, 216, 209. 3 G. J. Kubas, Inorg. Synth., 1979, 19, 90. 4 CAD-4 Express Software, Version 5.1, Enraf-Nonius, Delft, 1994. 5 E. J. Cabe, Y. Le Page, J.-P. Charland, F.L. Lee and P. S. White, J. Appl. Crystallogr., 1989, 22, 384. 6 T. Higashi, An Empirical Absorption Correction Based on Fourier Coefficient Fitting, Rigaku Corporation, Tokyo, 1995. 7 K. L. Krause and G. N. Phillips, jun., J. Appl. Crystallogr., 1992, 25, 146; M. Sato, M. Yamamoto, K. Imada, Y. Katsube, N. Tanaka and T. Higashi, J. Appl. Crystallogr., 1992, 25, 348. 8 D. Li, H. K. Yip, C. M. Che, Z. Y. Zhou, T. C. W. Mak and S. T. Liu, J. Chem. Soc., Dalton Trans., 1992, 2445. 9 X. He, K. R. Senge and P. P. Power, J. Am. Chem. Soc., 1994, 116, 6963. 10 M. S. Tsai and S. M. Peng, J. Chem. Soc., Chem. Commun., 1991, 514. 11 J. Beck and J. Strahle, Angew. Chem., Int. Ed. Engl., 1985, 24, 409. 12 K. M. Merz, jun. and R. HoVmann, Inorg. Chem., 1988, 27, 2120. 13 X. Y. Liu, F. Mota, P. Alemany, J. J. Novoa and S. Alvarez, Chem. Commun., 1998, 1149. 14 K. R. Kyle, C. K. Ryu, J. A. DiBenedetto and P. C. Ford, J. Am. Chem. Soc., 1991, 113, 2954; C. K. Ryu, K.R. Kyle and P. C. Ford, Inorg. Chem., 1991, 30, 3982; A. Vogler and H. Kunkely, J. Am. Chem. Soc., 1986, 108, 7211. 15 M. Munakata, M. Maekawa, S. Kitagawa, M. Adachi and H. Masuda, Inorg. Chim. Acta, 1990, 167, 181. 16 E. Lastra, M. P. Gamasa, J. Gimeno, M. Lanfranchi and A. Tiripicchio, J. Chem. Soc., Dalton Trans., 1989, 1499. 17 C. Vogler, H. D. Hausen, W. Kaim, S. Kohlmann, H. E. A. Kramer and J. Rieker, Angew. Chem., Int. Ed. Engl., 1989, 28, 1659. 18 M. Schwach, H.D. Hausen and W. Kaim, Chem. Eur. J., 1996, 2, 446. Received 24th March 1998; Paper 8/02279HJ. Chem. Soc., Dalton Trans., 1998, Pages 2867–2871 2871 Fig. 4 A perspective drawing of the complex cation 3 with atomic numbering scheme, H atoms are omitted for clarity Acknowledgements We acknowledge support from the Research Grants Council of Hong Kong, The University of Hong Kong and the Croucher Foundation. References 1 A. Balch, Prog. Inorg. Chem., 1993, 41, 239. 2 (a) M.Grassi, G. D. Munno, F. Nicolo and S. Lo Schiavo, J. Chem. Soc., Dalton Trans., 1992, 2367; (b) S. Lo Schiavo, M. S. Sinicropi, G. Tresoldi, C. G. Arena and P. Piraino, J. Chem. Soc., Dalton Trans., 1994, 1517; (c) S. Lo Schiavo, G. D. Munno, F. Nicolo and G. Tresoldi, J. Chem. Soc., Dalton Trans., 1994, 3135; (d ) S. Lo Schiavo, M. Grasi, G. D. Munno, F. Nicolo and G. Tresoldi, Inorg. Chim. Acta, 1994, 216, 209. 3 G. J. Kubas, Inorg. Synth., 1979, 19, 90. 4 CAD-4 Express Software, Version 5.1, Enraf-Nonius, Delft, 1994. 5 E. J. Cabe, Y. Le Page, J.-P. Charland, F. L. Lee and P. S. White, J. Appl. Crystallogr., 1989, 22, 384. 6 T. Higashi, An Empirical Absorption Correction Based on Fourier Coefficient Fitting, Rigaku Corporation, Tokyo, 1995. 7 K. L. Krause and G. N. Phillips, jun., J. Appl. Crystallogr., 1992, 25, 146; M. Sato, M. Yamamoto, K. Imada, Y. Katsube, N. Tanaka and T. Higashi, J. Appl. Crystallogr., 1992, 25, 348. 8 D. Li, H. K. Yip, C. M. Che, Z. Y. Zhou, T. C. W. Mak and S. T. Liu, J. Chem. Soc., Dalton Trans., 1992, 2445. 9 X. He, K. R. Senge and P. P. Power, J. Am. Chem. Soc., 1994, 116, 6963. 10 M. S. Tsai and S. M. Peng, J. Chem. Soc., Chem. Commun., 1991, 514. 11 J. Beck and J. Strahle, Angew. Chem., Int. Ed. Engl., 1985, 24, 409. 12 K. M. Merz, jun. and R. HoVmann, Inorg. Chem., 1988, 27, 2120. 13 X. Y. Liu, F. Mota, P. Alemany, J. J. Novoa and S. Alvarez, Chem. Commun., 1998, 1149. 14 K. R. Kyle, C. K. Ryu, J. A. DiBenedetto and P. C. Ford, J. Am. Chem. Soc., 1991, 113, 2954; C. K. Ryu, K. R. Kyle and P. C. Ford, Inorg. Chem., 1991, 30, 3982; A. Vogler and H. Kunkely, J. Am. Chem. Soc., 1986, 108, 7211. 15 M. Munakata, M. Maekawa, S. Kitagawa, M. Adachi and H. Masuda, Inorg. Chim. Acta, 1990, 167, 181. 16 E. Lastra, M. P. Gamasa, J. Gimeno, M. Lanfranchi and A. Tiripicchio, J. Chem. Soc., Dalton Trans., 1989, 1499. 17 C. Vogler, H. D. Hausen, W. Kaim, S. Kohlmann, H. E. A. Kramer and J. Rieker, Angew. Chem., Int. Ed. Engl., 1989, 28, 1659. 18 M. Schwach, H. D. Hausen and W. Kaim, Chem. Eur. J., 1996, 2, 446. Received 24th March 1998; Paper 8/02279H

ISSN:1477-9226    

DOI:10.1039/a802279h

出版商:RSC    

年代:1998

数据来源: RSC