Phosphido-bridged dimolybdenum complexes with sulfide and thiolate ligands as precursors to mixed-metal clusters

Article abstract of DOI:10.1016/S0022-328X(97)00297-0

Treatment of [Mo₂( μ-H)( μ-PPh₂)(CO)₄(η-C₅H₅)₂] with an excess of a thiol, RSH, in refluxing toluene produced the novel quadruply-bridged compounds [Mo₂( μ-S)₂( μ-SR)( μ-PPh₂)(η-C₅H₅)₂] (7a, R = Et; 7b, R = Prⁱ; 7c, R = Bu^t; 7d, R = p-C₆H₄Me; 7e R = C₁₂H₂₅) in moderate to good yield. The sulfur ligands in the product are formed by dealkylation of the thiol at the dimolybdenum centre. The reaction is proposed to proceed via the unstable intermediate species [Mo₂( μ-SR)( μ-PPh₂)(CO)₂(η-C₅H₅)₂], which could not be isolated in a pure form. Reaction of 7a-d with [Ru₃(CO)₁₂] in refluxing tetrahydrofuran (thf) produced good yields of the mixed-metal clusters [Mo₂Ru₂( μ₃-S)₂( μ-SR)( μ-PPh₂)(CO)₄(η-C₅H₅)₂] 9; the X-ray crystal structure of the Et-substituted complex 9a has been determined. The cluster consists of a tetrahedral metal core with both Mo₂Ru faces capped by triply bridging sulfides. The phosphido group bridges the Mo-Mo bond, whereas the thiolate ligand has migrated to the Ru-Ru edge.