REACTION OF [OS4(MU-H)4(CO)12] WITH CYCLOHEXA-1,3-DIENE VIA CHEMICAL ACTIVATION - SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF [OS4(MU-H)2(CO)10(ETA-6-C6H6)] AND [OS4(CO)9(ETA-6-C6H6)(ETA-4-C6H8)] AND THEIR INTERCONVERSION

The tetranuclear hydrido cluster [Os4(mu-H)4(CO)12] 1 has been activated by Me3NO-MeCN to give a reactive intermediate [Os4(mu-H)4(CO)10(MeCN)2] 2 which reacts further with cyclohexa-1,3-diene in CH2Cl2 under refluxing to produce new clusters including the benzene-co-ordinated compounds [Os4(mu-H)2(CO)10(eta-6-C6H6)] 5 and [Os4(CO)9(eta-6-C6H6)(eta-4-C6 H8)] 6. Structural analyses of 5 and 6 by X-ray diffraction have shown that the benzene ligand is co-ordinated to one metal atom in an eta-6 fashion, and the C6H8 ligand in 6 is also terminally bonded to one metal atom. Crystal data: 5, a = 8.209(1), b = 15.029(2), c = 16.453(2) angstrom, beta = 89.90(1)-degrees and Z = 4; 6, a = 15.614(2), b = 16.465(2), c = 18.010(2) angstrom, beta = 89.42(2)-degrees and Z = 8. Interconversion between compounds 5 and 6 has been observed. Reaction of 5 with cyclohexa-1,3-diene via Me3NO-MeCN activation leads to the formation of 6, while thermal decomposition of 6 affords 5.