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)Å], 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)Å]. 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.