Synthesis, Characterization, and Redox Behavior of Mixed 1,3-Diyne Dicobalt/Triosmium and Dicobalt/Triruthenium Carbonyl Clusters

The reaction between [Co-2(mu-eta(2)-HC CC2SiMe3)(mu-dmpm)(CO)(4)] (1) and [Os-3(CO)(10)(MeCN)(2)] gives rise to the formation of three new products: [Os-3(mu-H){mu(3)-eta(1):eta(2);mu-eta(2)-C2C2SiMe3[Co-2(mu-dmpm)(CO)(4)]}-(CO)(9)] (3), [Os-3(mu-H){mu-eta(1):eta(2);mu-eta(2)-C2C2SiMe3[Co-2(mu-dmpm)(CO)(4)]}-(CO)(10)] (4), and [Os-3{mu(3)-eta(1):eta(2).mu-eta(2)-HC2C2SiMe3[Co-2(mu-dmpm)(CO)(4)]}(mu-CO)(CO)(9)] (5). These complexes adopt three different coordination modes: mu(3)-eta(2) perpendicular, mu-eta(1) edge-bridged, and mu(3)-eta(2) parallel mode, respectively. When the reaction is carried out with [Ru-3(CO)(12)], only one product is obtained, [Ru-3(mu-H){mu(3)-eta(1):eta(2);mu-eta(2)-C2C2SiMe3[Co-2(mu-dmpm)(CO)(4)]}-(CO)(9)] (6), in which the triruthenium cluster is coordinated in a perpendicular mode. However, the reaction of [Co-2(mu-eta(2)-HC2(C C)(2)C2SiMe3)(mu-dppm)(CO)(4)] (2), stericaly more congested, with [Os-3(CO)(10)(Me3CN)(2)] yields only one product, the edge-bridged-coordinated [Os-3(mu-H){mu(3)-eta(1):eta(2);mu-eta(2)-C2C2SiMe3[Co-2(mu-dmpm)(CO)(4)]}-(CO)(10)] (7). [Os-3(CO)(10)(MeCN)(2)] reacts with HC CSiMe3, giving rise to the known parallel and perpendicular complexes and the new edge-bridged [Os-3(mu-H){mu-eta(1)-C2SiMe3-(CO)(10)]. All products were characterized by analytical and spectroscopic data (IR, H-1, C-13, and P-31 NMR, and MS). Crystals of 3, 6, and 7 suitable for single-crystal X-ray diffraction were grown, and the molecular structures of these compounds are discussed. A comparative electrochemical study of all these complexes is presented by means of the cyclic and square-wave voltammetry techniques.