THE PREPARATION AND ASPECTS OF THE CHEMISTRY OF SOME TERTIARY-PHOSPHINE, ARSINE AND STIBINE COMPLEXES OF HEXAOSMIUM CLUSTERS

Good routes have been developed to the mono- and bis-substituted derivatives [Os6(CO)17L] (L = P(OMe)3, PEt3, PPh2Me, PPh3, AsPh3 or SbPh3) and [Os6(CO)16L'2] (L' = PPh3, PPh2Me), which have structures based on the same bicapped tetrahedral Os6-unit established for [Os6(CO)18]. The [Os6(CO)16L'2] compounds apparently exist in more than one isomeric form and small amounts of the tris-substituted derivatives [Os6(CO)15L'3] are also observed. The mono-substituted hexaosmium cluster [Os6(CO)17L] undergoes reaction with Me3NO in CH2Cl2 to yield the previously unknown hydridohexaosmium anion [HOs6(CO)16L]- which on reaction with HBF4.Et2O first gives the neutral hexaosmium dihydride [H2Os6(CO)16L] and then the cation [H3Os6(CO)16L]+. The bis-substituted hexaosmium cluster [Os6(CO)16L2] reacts similarly with Me3NO/CH2Cl2 to give the hydrido-anion [HOs6(CO)16L2]-.