CLUSTER SYNTHESIS .36. NEW PLATINUM RUTHENIUM AND PLATINUM OSMIUM CARBONYL CLUSTER COMPLEXES FROM THE REACTIONS OF THE COMPLEXES PT2M4(CO)18 (M = RU, OS) WITH CYCLOOCTA-1,5-DIENE IN THE PRESENCE OF UV IRRADIATION

The reactions of Pt2M4(CO)18 (1a, M = Ru; 1b, M = Os) with cycloocta-1,5-diene (COD) in the presence of UV irradiation were studied. The reaction of 1a yielded the new mixed-metal cluster compounds PtRu4(CO)12(mu-4-CO)(COD) (2) (11%) and Pt4Ru5(CO)20(COD) (3) (16%). Compounds 2 and 3 were characterized by IR, H-1 NMR, and single-crystal X-ray diffraction analyses. The cluster of 2 consists of a butterfly tetrahedron of four ruthenium atoms that is capped on one of the triangular faces by a Pt(COD) group. A mu-4-eta-2-CO ligand lies in the fold of the butterfly. The cluster of compound 3 consists of nine metal atoms and can be described as combination of a Pt3Ru3 octahedron fused to a Pt3Ru2 square pyramid with a common Pt3 face and a Pt(COD) capping group on the Ru3 face of the octahedron. The reaction of 1b yielded the hexanuclear products Pt2Os4(CO)17 (5) (29%) and Pt2Os4(CO)15(COD) (6) (25%) and small amounts of the known hexanuclear compounds Pt2Os4(CO)12(COD)2 (8) (6%) and PtOs2(CO)8(COD) (4) (7%). Compound 6 was characterized crystallographically. The cluster of 6 exhibits the well-known triangle of triangles "raft" structure with a Pt(COD) grouping on one of the outer triangles and one Pt(CO) group in the inner triangle. Compound 5 is believed to possess a structure similar to 6 but with two CO ligands in the place of the COD ligand. Cyclic voltammetric measurements on compound 5 showed the presence of two reversible one-electron reductions at E1/2 = -0.57 and -0.84 V. Compound 6 shows two quasireversible one-electron reductions at E1/2 = -0.67 and -0.93 V. Crystal data: for 2, space group = P1BAR, a = 10.544 (1) angstrom, b = 17.064 (4) angstrom, c = 8.847 (2) angstrom, alpha = 104.31 (2)-degrees, beta = 98.36 (2)-degrees, gamma = 74.27 (2)-degrees, Z = 2,2355 reflections, R = 0.028; for 3, space group = C2/c, a = 26.361 (4) angstrom, b = 9.474 (4) angstrom, c = 31.211 (4) angstrom, beta = 94.85 (1)-degrees, Z = 8, 3769 reflections, R = 0.026; for 6, space group = Pbca, a = 14.781 (3) angstrom, b = 35.83 (2) angstrom, c = 11.548 (2) angstrom, Z = 8, 2047 reflections, R = 0.035.