Cluster synthesis. 11. Role of sulfido ligands in the synthesis of heteronuclear clusters. Synthesis and crystal and molecular structures of PtOs₄(CO)₁₁(PMe₂Ph)₂(μ₃-S)₂ and PtOs₃(CO)₉(PMe₂Ph)₂(μ₃-S)₂

The synthesis of the mixed-metal cluster compounds PtOs₄(CO)₁₁(PMe₂Ph)₂(μ₃-S)₂ (1) and PtOs₃(CO)₉(PMe₂Ph)₂(μ₃-S)₂ (2) was achieved by the reaction of Os₄(CO)₁₂(μ₃-S)₂ (3) with Pt(PMe₂Ph)₄. Compound 1 was converted into 2 by treatment with CO. Compound 2 was also synthesized by the reaction of Os₃(CO)₉(μ₃-S)₂ with Pt(PMe₂Ph)₄. Compounds 1 and 2 were characterized structurally by single-crystal X-ray diffraction analyses. For 1: space group Pca2₁, No. 29; a = 23.801 (3) Å, b = 9.136 (3) Å, c = 18.368 (4) Å, Z = 4, ρ_calcd = 2.81 g/cm³. The structure was solved by direct methods (MULTAN) and refined (2343 reflections, F² ≥ 3.0σ(F²)) to the final residuals R_F = 0.040 and R_wF = 0.042. For 2: space group P2₁/c, No. 14; a = 9.533 (4) Å, b = 15.580 (7) Å, c = 24.547 (8) Å, β = 99.87 (3)°, Z = 4, ρ_calcd = 2.51 g/cm³. The structure was solved by direct methods (MULTAN) and refined (2527 reflections, F² ≥ 3.0σ(F²)) to the final residuals R_F = 0.037 and R_wF = 0.049. The cluster of 1 consists of a butterfly tetrahedron of four osmium atoms with a Pt(PMe₂Ph)₂ group bridging one of the peripheral edges. The cluster of 2 consists of an open triangular cluster of three osmium atoms with a Pt(PMe₂Ph)₂ group bridging one of the two osmium-osmium bonds. Variable-temperature ¹H NMR studies of 2 showed that it undergoes a rapid rearrangement of the cluster framework, ΔG₁₆₇ = 7.5 kcal/mol, that produces a time-averaged plane of symmetry. A process in which the platinum atom interchanges bridging sites between the two osmium-osmium bonds is proposed. © 1986 American Chemical Society.