The First exo-nido-Ruthenacarborane Clusters. Synthesis and Molecular Structure of 5,6,10-[Cl(Ph3P)2Ru]-5,6,10-μ-(H)3-10-H-7,8-C2B9H8

Novel exo-nido-ruthenacarboranes, 5,6,10-[CI(Ph₃P)₂Ru]-5,6,10-μ-(H)₃-10-H-7,8-R₂C₂B₉H₆ (1; R = H, structurally characterized by an X-ray diffraction study, and 2; R = Me) have been prepared by reaction of RuCl₂ (PPh₃)₃ and [nido-7,8-R₂C₂B₉H₁₀]⁻ K⁺ in diethyl ether-tetrahydrofuran; in the solid state clusters 1 and 2 contain tridentate nido–carborane ligands bound to the Ru^II atom through three Ru—H—B bridging hydrogen bonds, whereas in solution they exist as an equilibrium mixture of isomeric exo-nido-bis(triphenylphosphine)chlorohydridoruthenacarboranes formed as a result of the cleavage of one of the Ru—H—B bonds with the formation of a new Ru—B σ-bond and a simultaneous hydrogen atom shift to the metal atom.