The heteronuclear cluster chemistry of the Group 1B metals. Part 6. Synthesis, structures, and dynamic behaviour of the bimetallic hexanuclear Group 1B metal cluster compounds [M2Ru4(µ3-H)2{µ-Ph2P(CH2)nPPh2}(CO)12](M = Cu or Ag, n= 1–6). X-Ray crystal structures of [Cu2Ru4(µ3-H)2{µ-Ph2P(CH2)nPPh2}(CO)12](n= 2, 3, or 5)

Abstract

Treatment of a dichloromethane solution of the salt [N(PPh₃)₂]₂[Ru₄(µ-H)₂(CO)₁₂] with two equivalents of the complex [M(NCMe)₄]PF₆(M = Cu or Ag) at –30 °C, followed by the addition of one equivalent of Ph₂P(CH₂)_nPPh₂(n= 1–6) affords the mixed-metal cluster compounds [M₂Ru₄(µ₃-H)₂{µ-Ph₂P(CH₂)_nPPh₂}(CO)₁₂] in ca. 65–75% yield. These species have been characterized by i.r. and n.m.r. spectroscopy and the structures of [Cu₂Ru₄(µ₃-H)₂{µ-Ph₂P(CH₂)_nPPh₂}(CO)₁₂](n= 2, 3, or 5) have been determined by X-ray diffraction studies. The clusters all adopt the same metal core structure, which consists of a tetrahedron of ruthenium atoms capped by a Group 1B metal, with one of the MRu₂ faces of the MRu₃ tetrahedron so formed further capped by a second Group 1B metal to give a capped trigonal-bipyramidal skeletal geometry. The other two MRu₂ faces of the MRu₃ tetrahedron are each capped by a triply-bridging hydrido ligand, the bidentate diphosphine ligand bridges the two coinage metals, and each ruthenium atom is ligated by three terminal CO groups. Variable-temperature ¹H and ³¹P-{¹H} n.m.r. studies show that, at ambient temperature in solution, the metal frameworks of all of the clusters still undergo dynamic behaviour involving coinage metal site-exchange, even though the two Group 1B metals are linked together by bidentate diphosphine ligands.