The heteronuclear cluster chemistry of the group 1B metals. Part 4. Synthesis, structures, and dynamic behaviour of group 1B metal–ruthenium cluster compounds containing sulphur ligands. X-Ray crystal structures of [M2Ru3(µ3-S)(µ-Ph2PCH2PPh2)(CO)9](M = Cu or Au)

Abstract

Treatment of a tetrahydrofuran solution of the salt K2[Ru3(µ3-S)(CO)9] with the complex [MX(PPh3)](M =Cu or Au, X =Cl; M = Ag, X = I), in the presence of TIPF6, affords a mixture of cluster compounds, [MRu3(µ-H)(µ3-S)(CO)9(PPh3)][for M = Cu (2), Ag (3), or Au (4)], [MRu3(µ-H)-(µ3-S)(CO)8(PPh3)2][for M = Cu (5) or Ag (6)], and [M2Ru3(µ3-S)(CO)9(PPh3)2][for M = Cu (8), Ag (9), or Au (10)]. In addition, the pentanuclear clusters [M2Ru3(µ3-S)(µ-Ph2PCH2PPh2)-(CO)9][M = Cu (12) or Au (13)] can be synthesized from the reaction between K2[Ru3(µ3-S)-(CO)9] and [M2(µ-Ph2PCH2PPh2)Cl2], using TIPF6. Infrared and n.m.r. spectroscopic data imply that the tetranuclear copper- or silver-containing species (2), (3), (5), and (6) all adopt the same ‘butterfly’ MRu3 metal-core geometry as that previously established for the Au cluster (4) and that the pentanuclear Cu and Ag species (8) and (9) exhibit the same trigonal-bipyramidal M2Ru3 framework as that determined for the Au cluster (10). However, X-ray diffraction studies on the bidentate phosphine-containing pentanuclear Cu2Ru3 species (12) and its Au2Ru3 analogue (13) reveal two different metal-corestructures. The Cu cluster (12) has a trigonal-bipyramidal metal skeleton [Cu–Cu 2.515(3), Cu–Ru 2.552(2)–2.794(2), Ru–Ru 2.814(2)–2.856(2)A], with one of the two phosphine-bridged Cu atoms occupying an equatorial site and the other an axial site. The S atom caps the Ru3 face of the trigonal-bipyramidal unit. In the Au species (13), the metal framework structure is intermediate between a trigonal bipyramid and a square-based pyramid [Au–Au 2.802(1), Au–Ru 2.742(l)–2.836(1), Ru–Ru 2.773(2)–2.968(2)A]. Variable-temperature n.m.r. studies show that, at ambient temperature in solution, the coinage metals in each of the pentanuclear clusters (8)–(10), (12), and (13) are exchanging between the two distinct sites in the cluster skeleton, the PPh3 groups in the copper–ruthenium species (2) and the silver–ruthenium species (3), (6), and (9) are undergoing intermolecular exchange between clusters, and the CO ligands in all of the clusters exhibit dynamic behaviour involving intramolecular site-exchange.