The [Os3(µ-H)(CO)10(MeCN)2]+ cation: synthesis and X-ray crystal structure of [Os3(µ-H)(CO)10(MeCN)2][Os(CO)3Cl3]

The clusters [Os3(CO)11(MeCN)] and [Os3(CO)10(MeCN)2] react with acids HX (X = BF4 or PF6) to form the cationic derivatives [Os3(µ-H)(CO)11(MeCN)]X and [Os3(µ-H)(CO)10(MeCN)2]X, respectively. The cluster [Os3(CO)10(MeCN)2] also reacts with dry HCl to form the salt [Os3(µ-H)-(CO)10(MeCN)2][Os(CO)3Cl3]. X-Ray analysis of this salt shows that the Os atoms in the cation lie at the vertices of an isosceles triangle. A hydride bridges the long Os–Os edge, and the two acetonitrile ligands occupy trans axial sites. Reaction of [Os3(µ-H)(µ-OH)(CO)10] with HBF4 in MeCN also produces [Os3(µ-H)(CO)10(MeCN)2]+. In this reaction direct attack of H+ on the co-ordinated OH– ligand is considered to occur with the resultant liberation of H2O. Treatment of [Os3(µ-H)(CO)10–(MeCN)2]+ with [Os(CO)4]–2 leads to the formation of the neutral complex [Os4H2(CO)14(MeCN)]. The bridging hydride of the cation may also be replaced by a bridging nitrosyl ligand by reaction with NO+.