CLUSTER SYNTHESIS .33. NEW PLATINUM OSMIUM CARBONYL CLUSTER COMPLEXES FROM PT2OS5(CO)17(MU-H)6 - SYNTHESIS AND CHARACTERIZATION OF PTOS5(CO)15(MU-3-S)(MU-H)6, PTOS5(CO)18(MU-H)4, AND PTOS4(CO)15(MU-H)2

From the reaction of Pt2Os5(CO)17(mu-H)6 with H2S at 25-degrees-C the new platinum-osmium carbonyl cluster complex PtOs5(CO)15(mu-3-S)(mu-H)6 (2) was obtained in 83% yield. Compound 2 was characterized by IR, H-1 NMR, C-13 NMR, and single-crystal X-ray diffraction analyses. The structure of 2 consists of a PtOs3 tetrahedron fused to a PtOs2 triangle with the platinum atom at the vertex-sharing site. There is a triply bridging sulfido ligand on the PtOs2 triangular grouping. The molecule was shown by variable-temperature H-1 NMR and C-13 NMR spectroscopy to undergo a dynamic process that involves an intramolecular rotation of the Os3 triangular group relative to the Os2S grouping at the platinum atom. DELTA-G*261 = 12.3 kcal/mol. The reaction of Pt2Os5(CO)17(mu-H)6 with Os(CO)5 at 25-degrees-C yielded two new platinum-osmium carbonyl cluster complexes PtOs5(CO)18(mu-H)4 (3) and PtOs4(CO)15(mu-H)2 (4) in 38% and 25% yields, respectively. Both compounds were characterized crystallographically. The cluster of compound 3 consists of a PtOs3 tetrahedron fused to a PtOs2 triangle by the vertex-sharing platinum atom. The cluster of compound 3 contains a PtOs3 tetrahedron with an edge-bridging Os(CO)4 group. The positions of all of the hydride ligands in 3 and 4 were determined by a combination of H-1 NMR spectroscopy and crystallography. Compound 3 is readily degraded by CO (25-degrees-C/1 atm) to yield the products PtOs2(CO)10, H2Os2(CO)8, and H2Os(CO)4. Crystal data: for 2, space group P1BAR, a = 19.451 (6) angstrom, b = 23.075 (3) angstrom, c = 9.771 (2) angstrom, alpha = 94.69 (1)-degree, beta = 100.81 (2)-degrees, gamma = 98.90 (2)-degrees, Z = 6,5486 reflections, R = 0.040; for 3, space group P2(1), a = 8.875 (5) angstrom, b = 19.47 (1) angstrom, c = 9.370 (3) angstrom, beta = 116.42 (3)-degrees, Z = 2, 1607 reflections, R = 0.045; for 4, space group P2(1)/c, a = 13.337 (2) angstrom, b = 8.809 (3) angstrom, c = 20.141 (4) angstrom, beta = 90.59 (2)-degrees, Z = 4, 2400 reflections, R = 0.036.