Syntheses, reactivity studies and the catalytic properties of a series of tetraosmium-gold mixed-metal clusters

Treatment of the mixture of [Os4(μ-H)4(CO)12] and [AuPPh3Cl] with excess triethylamine afforded three novel tetraosmium-gold mixed-metal clusters, [Os4Au2(μ-H)2(CO)11(PPh3)3] (4), [Os4Au3(μ-H)3(CO)11(PPh3)3] (5), and [Os4Au4(μ-H)2(CO)11(PPh3)4] (6) in moderate yields. Cluster [Os4Au(μ-H)3(CO)11(NMe3) (PPh3)] (2) was also obtained in a similar reaction in the presence of trimethylamine N-oxide. They were fully characterized by different spectroscopic techniques, and the solid-state structures were established by X-ray analysis. These dimetallic clusters exhibit an osmium/gold ratio ranging from 1 to 4. Their electronic absorption properties, electrochemistry, and catalytic properties, as a result of the oxidative carbonylation of aniline, were investigated in terms of the Os/Au ratio. KGaA, 69451 Weinheim, Germany, 2003.