Substituted osmium clusters containing labile ligands. The preparation, characterisation, and some reactions of [Os3H(OR)(CO)9(MeCN)](R = H, Me, Et, or Ph) and the isomers of [Os3H(SR)(CO)9(MeCN)](R = Me, Et, or Ph); the crystal and molecular structure of [Os3H(SPh)(CO)9(PEt3)]

Abstract

The compounds [Os₃H(ER)(CO)₁₀](E = O, R = H, Me, Et, or Ph; E = S, R = Me, Et, or Ph) react with Me₃NO in MeCN to produce the acetonitrile derivatives [Os₃H(ER)(CO)₉(MeCN)]. For ER = OR there is only one such compound formed which has the acetonitrile ligand attached to one of the bridgehead osmium atoms. These clusters react with P(OMe)₃ to form two isomers of the compounds [Os₃H(OR)(CO)₉{P(OMe)₃}], both of which have the phosphite ligands co-ordinated to one of the bridgehead osmium atoms. For the case ER = SR three isomers of the acetonitrile derivative are formed, two with the acetonitrile ligand attached to the unique osmium atom and one as in the alkoxy case. These isomers react with phosphorus donor ligands to produce isomers of the compounds [Os₃H(SR)(CO)₉(PR′₃)], where the phosphorus donor ligand is bound to the same osmium atom as the acetonitrile in the starting material. The compounds [Os₃H(OR)(CO)₈-{P(OMe)₃}₂] were prepared from reaction of [Os₃H(OR)(CO)₁₀] with 2.2 equivalents of Me₃NO followed by P(OMe)₃. All the products have been characterised by i.r. and ¹H n.m.r. spectroscopy and structural assignments made. The structure of [Os₃H(SPh)(CO)₉(PEt₃)] was confirmed by X-ray analysis and shown to consist of a riangle of Os atoms with one edge bridged by both a hydride and a phenylthiolato ligand. The triethylphosphine ligand occupies a ‘pseudo’ axial site on one of the Os atoms involved in bridge bonds. The nine carbonyl groups all occupy terminal co-ordination sites.