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

The reaction between [Co2(μ−η2-HC⋮CC2SiMe3)(μ-dmpm)(CO)4] (1) and [Os3(CO)10(MeCN)2] gives
rise to the formation of three new products:  [Os3(μ-H){μ3-η1:η2;μ-η2-C2C2SiMe3[Co2(μ-dmpm)(CO)4]}(CO)9] (3), [Os3(μ-H){μ-η1;μ-η2-C2C2SiMe3[Co2(μ-dmpm)(CO)4]}(CO)10] (4), and [Os3{μ3-η1:η2;μ-η2-HC2C2SiMe3[Co2(μ-dmpm)(CO)4]}(μ-CO)(CO)9] (5). These complexes adopt three different coordination
modes:  μ3-η2 perpendicular, μ-η1 edge-bridged, and μ3-η2 parallel mode, respectively. When the reaction
is carried out with [Ru3(CO)12], only one product is obtained, [Ru3(μ-H){μ3-η1:η2;μ-η2-C2C2SiMe3[Co2(μ-dmpm)(CO)4]}(CO)9] (6), in which the triruthenium cluster is coordinated in a perpendicular mode.
However, the reaction of [Co2(μ-η2-HC2(C⋮C)2C2SiMe3)(μ-dppm)(CO)4] (2), stericaly more congested,
with [Os3(CO)10(Me3CN)2] yields only one product, the edge-bridged-coordinated [Os3(μ-H){μ-η1;μ-η2-C2C2SiMe3[Co2(μ-dppm)(CO)4]}(CO)10] (7). [Os3(CO)10(MeCN)2] reacts with HC⋮CSiMe3, giving rise
to the known parallel and perpendicular complexes and the new edge-bridged [Os3(μ-H){μ-η1-C2SiMe3(CO)10]. All products were characterized by analytical and spectroscopic data (IR, 1H, 13C, and 31P 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.