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

Abstract

Treatment of [Mo 2(μ-H)(μ-PPh 2)(CO) 4(η-C 5H 5) 2] with an excess of a thiol, RSH, in refluxing toluene produced the novel quadruply-bridged compounds [Mo 2(μ-S) 2(μ-SR)(μ-PPh 2)(η-C 5H 5) 2] (7a, R = Et; 7b, R = Pr 1; 7c, R = Bu 1; 7d, R = p-C 6H 4Me; 7c R = C 12H 25) 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 [Mo 2(μ-SR)(μ-PPh 2)(CO) 2(η-C 5H 5) 2], which could not be isolated in a pure form. Reaction of 7a-d with [Ru 3(CO) 12] in refluxing tetrahydrofuran (thf) produced good yields of the mixed-metal clusters [Mo 2Ru 2( μ 3S) 2( μ-SR)( μ-PPh 2)(CO) 4( η-C 5H 5) 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 Mo 2Ru faces capped by triply bridging sulfides. The phosphido group bridges the MoMo bond, whereas the thiolate ligand rated to the RuRu edge.