STRUCTURAL ASPECTS OF THE OSMIUM AND RUTHENIUM CLUSTERS [M3(CO)10(ALKYNE)] AND RELATED SUBSTITUTED COMPOUNDS

The synthesis and single-crystal structure determination of the cluster [Os3(CO)10(mu3-MeO2CC2CO2Me)], derived from the bis-acetonitrile complex [Os3(CO)10(MeCN)2] and the alkyne MeO2CC=CCO2Me, are described. The alkyne C-C bond is approximately parallel to an Os-Os edge and one CO ligand is bridging. Distinct distortions from an idealized structure with C(s) symmetry are apparent, as previously noted for this class of compound, and a comparison with nine other reported structures of related osmium and ruthenium clusters is presented. Essentially all situations are encountered between two extremes: a structure close to C(s) symmetry with a symmetrical mu-CO and a parallel alkyne and another with only terminal CO and a rather more distorted alkyne coordination. There is a clear correlation between the geometry of the bridging CO, metal-metal distances, and the arrangement of the mu3-alkyne. IR spectra indicate that there are different structures in solution in some cases.