SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF SOME TRIANGULAR AND TETRAHEDRAL MIXED METAL PLATINUM-GOLD CLUSTERS

The compounds [Pt2(mu-SO2)(CNxylyl)2(PCy3)2] and [Pt3(mu-SO2)2(CNxylyl)(PCy3)3] react with one mole of [Au(PCY3)Cl] to give [Pt2Au(mu-SO2)(CNxylyl)2(PCy3)3]+PF6- (I) and [Pt3Au(mu-SO2)2(mu-CNxylyl)(PCY3)4]+ PF6- (II), respectively. The molecular structure of I has been determined by single crystal X-ray techniques, and found to be based on a nearly perfect equilateral triangle of the three metal atoms. The Pt-Pt bond is bridged by an SO2 ligand, and the two platinum atoms are also coordinated to one xylyl-isocyanide ligand each. The coordination environments about each metal are completed by a tricyclohexylphosphine ligand. NMR studies (P-31-{H-1) and Pt-195-{H-1}) have confirmed that this structure persists in solution. The molecular structure of II was established from IR, P-31-{H-1} NMR and FAB mass spectroscopic studies, as a tetrahedral structure with only one xylyl isocyanide bridging the two equivalent platinum atoms. There are two SO2 ligands bridging the other Pt-Pt bonds in the triangle and the coordination environment about each metal is completed by a tricyclohexylphosphine ligand.