On the structural effect of the bridging hydride ligand on a metalmetal bond in a trinuclear cluster. the crystal and molecular structures of (μ-H)(μ-S₂CH)Os₃(CO)₁₀and (μ-H)(μ-S₂CH)Os₃(CO)₉[PP(CH₃)₂C₆H₅]

The crystal and molecular structures of the complexes (μ-H)(μ-S₂CH)Os₃(CO)₁₀), III and (μ-H)(μ-S₂CH)Os₃(CO)₉[P(CH₃)₂C₆H₅],IV, are reported. For III: Space group P2₁/c, No. 14, [C⁵_2h], at 35° C, a = 8.452(2), b = 25.435(12), c = 16.818(5) Å, β = 91.75(3), Z = 8, ϱ_calc = 3.43 g/cc. For IV: Space group = P1, No. 2, at35°C, a = 8.375(3), b = 12.960(4), c = 15.106(4) Å, α = 64.50(2)°, β = 70.22(3)°, γ = 79.20(3)°, Z = 2, ϱ_calc = 2.48 g/cc.Both compounds contain triangular clusters of osmium atoms and have dithioformato ligands bridging edges of the clusters in axial coordination sites. The dimethylphenylphosphine ligand is bonded to the unique osmium atom in IV in an equatorial coordination site. The hydride ligands were not observed directly but their positions are strongly inferred on the basis of geometrical considerations. In III the hydride and the dithioformato ligands bridge the same metalmetal bond. The OsOs internuclear distance is 2.973(1) Å. In IV the hydride ligand bridges a metal metal bond which is adjacent to the one bridged by the dithioformato ligand. The OsOs distance of the dithioformato bridged bond in IV is only 2.854(1) Å. The much longer dithioformato bridged metalmetal bond in III is thus attributed principally to the presence of the bridging hydride ligand.