Combined X-ray and neutron diffraction study of [Os₄(CO)₁₁H₃(CHCHPh)]

The title complex has been prepared by the photolytic reaction of styrene with [Os₄(CO)₁₂H₄]. It crystallises in the monoclinic space group P2₁/c with a = 8.720(3), b = 16.338(5), c = 18.144(6) Å, β = 111.60(3)°, and Z = 4. Simultaneous refinement of a single parameter set to fit 2 155 X-ray [(sin θ)/λ > 0.352] and 935 neutron data has led to R 0.058 (X-ray) and 0.096 (neutron). The Os₄ unit is tetrahedral with three long (mean 2.956 Å) and three short (mean 2.806 Å) Os-Os edges. The styrenyl ligand σ bonds to one Os atom and π bonds to another, asymmetrically bridging a short Os-Os edge. The three hydride ligands bridge two long and one short metal-metal bond with O-H distances in the range 1.77 to 1.86 Å. The eleven carbonyl ligands are all terminal.