The Crystal and Molecular Structure of HOs6(CO)21(NCMe)PH2

The crystal structure of the phosphide-bridged cluster [Os6(μ-H)(CO)12(NCMe)(μ-PH2)] 4 has been determined. The cluster consists of two Os3 triangles which are linked by a PH2 moiety which is terminally bound to each triangle. The acetonitrile ligand is axially coordinated and the hydride bridges the Os---Os edge to which the phosphide moiety and the acetonitrile are coordinated. The molecular structure of 4 resembles those of the related clusters [Os6(μ-H)(CO)22(μ-PH2)] 1 and [Os6(μ-H)(CO)21(CNBut)(μ-PH2)] 2 although the dihedral angles between the two osmium triangles vary for 1, 2 and 4. The relative orientation of the two linked metal triangles in 4 (as well as 1 and 2) differs from that of the phosphite-substituted analogue [Os6(μ-H)(CO)20{P(OMe)3}2(μ-PH2)]3; this difference is attributed to steric factors