Syntheses, structures and comparative electrochemical study of π-acetylene complexes of cobalt

The preparation and characterization of the complexes [Co2(CO)4(μ-dppm)]2(μ-η2-Me3SiC2(Ctriple bond; length of mdashC)2C2H) (2), [Co2(CO)4(μ-dppm)]2(μ-η2-HC2(Ctriple bond; length of mdashC)2C2H) (3), Co2(CO)4(μ-dmpm)(μ-η2-Me3SiC2Ctriple bond; length of mdashCSiMe3) (4), Co2(CO)4(μ-dmpm)(μ-η2-Me3SiC2Ctriple bond; length of mdashCH) (5), [Co2(CO)4(μ-dmpm)]2(μ-η2-Me3SiC2(Ctriple bond; length of mdashC)2C2SiMe3) (6) and [Co2(CO)4(μ-dmpm)]2(μ-η2-HC2(Ctriple bond; length of mdashC)2C2H) (7) are described. A comparative electrochemical study of all these complexes and the related [Co2(CO)4(μ-dppm)]2(μ-η2-Me3SiC2(Ctriple bond; length of mdashC)2C2SiMe3) (1), Co2(CO)4(μ-dppm)(μ-η2-Me3SiC2Ctriple bond; length of mdashCH) and Co2(CO)4(μ-dppm)(μ-η2-HC2Ctriple bond; length of mdashCH) is presented by means of the cyclic and square-wave voltammetry techniques. Crystals of 2 and 3 suitable for single-crystal X-ray diffraction were grown and the molecular structures of these compounds are discussed.