CLUSTER SYNTHESIS .35. ON THE WAY TO HIGH-NUCLEARITY PLATINUM OSMIUM CLUSTER COMPLEXES - SYNTHESIS AND STRUCTURAL CHARACTERIZATIONS OF PT2OS3(CO)9(COD)2(MU-H)2 AND PT4OS6(CO)21(COD)(MU-H)2 (COD = CYCLOOCTA-1,5-DIENE)

The new platinum-osmium carbonyl cluster complex Pt2Os3(CO)9(COD)2(mu-H)2 (3) was obtained in 31% yield from the reaction of Os3(CO)10(mu-H)2 (1) with two equiv of Pt(COD)2 at 25-degrees-C. When a solution of compound 3 in hexane solvent was heated to reflux, it was transformed into the new decanuclear complex Pt4Os6(CO)21(COD)(mu-H)2 (4) in 16% yield by the condensation of two molecules of 3. The yield of 4 can be increased to 30% by the addition of small amounts of CO. Both products were characterized by IR, H-1 NMR, and single-crystal X-ray diffraction analyses. Compound 3 contains a triangular Os3 cluster that is capped on one face by a triply bridging Pt(COD) group and bridged on one edge by a second Pt(COD) grouping. Compound 3 is formally electron deficient. This can be attributed to the 16-electron configuration of the edge-bridging Pt(COD) grouping. The structure of compound 4 was found to consist of triangulated alternating layers of osmium and platinum atoms with a capping Pt(COD) grouping on one of the triosmium faces. Crystal data: for 3, space group, P1BAR, a = 10.368 (1) angstrom, b = 14.358 (3) angstrom, c = 9.861 (2) angstrom, alpha = 102.80 (2)-degrees, beta = 91.61 (2)-degrees, gamma = 96.39 (1)-degrees, R = 0.036 for 2484 reflections; for 4, space group, P2(1)/c, a = 14.708 (3) angstrom, b = 15.484 (3) angstrom, c = 19.313 (2) angstrom, beta = 90.85 (1)-degrees, R = 0.034 for 2485 reflections.