Does a Metal to Metal “Ligand” Effect Influence the Catalytic Activity of Bimetallic Cluster Complexes? Synthesis and Catalytic Activity of Pt3Ru6(CO)19(SMe2)(μ3-PhC2Ph)(μ3-H)(μ-H)

The layer-segregated platinum−ruthenium cluster complex Pt 3 Ru 6 (CO) 19 (SMe 2 )(μ 3 -PhC 2 Ph)(μ 3 -H)(μ-H) ( 2 ) has been obtained in 51% yield from the reaction of Pt 3 Ru 6 (CO) 20 (μ 3 -PhC 2 Ph)(μ 3 -H)(μ-H) ( 1 ) with SMe 2 . Compound 2 is structurally analogous to 1 but contains a Me 2 S ligand coordinated to one of the ruthenium atoms of the Ru 3 triangle that contains a bridging PhC 2 Ph ligand. EXSYS 2D 1 H NMR measurements have shown that the Me 2 S ligand is labile and readily exchanges with free Me 2 S in solution. Fresh solutions of compound 2 rapidly hydrogenate PhC 2 Ph to ( Z )-stilbene at a turnover frequency TOF of 102 h - 1, but the activity is quickly reduced to the level of 1 because 2 is converted to 1 under the conditions of the catalysis. It is proposed that the high catalytic activity of 2 compared to 1 is related to lability of the Me 2 S ligand, thus implying that this site on the PhC 2 Ph-bridged Ru 3 triangle is catalytically active. It is proposed that all catalytic transformations occur at the ruthenium triangle(s). It is suggested that the enhanced catalytic activity of these bimetallic cluster complexes is due in part to the presence of the platinum layer. The promotional effect may be due to a simple donation of electron density from the platinum to the ruthenium, a metal to metal “ligand” effect.