Binding modes of a mixed donor multidentate iminobisphosphane ligand to the triosmium cluster: the crystal structures of [{Os3(CO)11}2(PNCHP)], [Os3(μ-H)(μ3-PNCP)(CO)7] and [Os3(μ-H)(μ2-PNCP)(CO)8]

The triosmium clusters [Os3(CO)11(CH3CN)] and [Os3(CO)10(CH3CN)2] react with 2-(diphenylphosphino)-N-[2-(diphenylphosphino)benzylidene]benzeneamine (PNCHP) to give [{Os3(CO)11}2(PNCHP)] (1), two coordination isomers of [Os3(CO)11(PNCHP)] (2a) and (2b), and 1,1-[Os3(CO)10(PNCHP)] (3), respectively. When (3) is reacted with trimethylamineoxide the major product is [Os3(μ-H)(CO)7(μ3-PNCP)] (4) with two geometrical isomers of [Os3(μ-H)(CO)8(μ2-PNCP)] (5a) and (5b) being minor products. The clusters have been fully characterised by spectroscopic means and the structures of 1·CH2Cl2, 4·1.5CH2Cl2 and 5a established by single-crystal X-ray analyses. In 1 PNCHP bridges two osmium triangles equatorially. In 4 the imine hydrogen of PNCHP has migrated to the osmium cluster and PNCP acts as a triply bridging nine electron donor, while in 5a PNCP acts as a doubly bridging seven electron donor ligand.