The heterometallic cluster compound (C5Me5)W(μ-O)2Os3(μ-CCPh)(CO)9 (1), which possesses two edge-bridging oxo groups and an acetylide ligand in a μ-η2 mode, has been obtained by addition of (C5Me5)W(O)2(CCPh) to Os3(CO)10(NCMe)2. The subsequent reactivity studies led to the isolation of Cp*W(μ-O)2Os3(μ-H)(CO)9 (2) and Cp*W(O)(μ-O)Os3(CCPh)(CO)9 (3) through hydrogenation and treatment with pressurized CO, respectively. The structures of 1 and 3 reveal two distinctive bonding modes for the (C5Me5)W(O)2 fragment on an Os3 skeleton.

Treatment of acetylide cluster Cp*WOs 3 (µ-O) 2 (µ-CCPh)(CO) 9 (1), Cp* ) C 5 Me 5 , with diphenylacetylene affords two cluster complexes Cp*W(O)Os 3 (µ-O)(CCPh)(PhC 2 Ph)(CO) 8 (2) and Cp*W(O)Os 3 (µ-O)(CCPhCPhCPh)(CO) 8 (3a) by alkyne coordination and cluster-assisted formation of C-C bonds between acetylide and alkyne, respectively. For the reaction with phenylacetylene, only the coupled product Cp*W(O)Os 3 (µ-O)(CCPhCHCPh)(CO) 8 (3b) is obtained, together with a small amount of Cp*W(O)Os 3 (µ-O)(CCPhCCHPh)(CO) 8 (4).Complex 2 slowly converts to 3a and the complex Cp*W(O)(µ-O)Os 3 (CCPhCPhCPh)(CO) 8 (5a) when heated in toluene, whereas the formation of 4 is believed to pass through a pathway involving an alkyne-to-vinylidene rearrangement. The conversion from complexes 3 to 5 demonstrates a unique skeletal isomerization involving the interchange of a Cp*W(O) 2 unit and one Os(CO) 3 fragment. Experimental SectionGeneral Information and Materials. Infrared spectra were recorded on a Perkin-Elmer 2000 FT-IR spectrometer.