Silicon–transition-metal compounds. Part I. Silyltetracarbonylcobalt and related compounds

Abstract

Iodosilane and di-iodosilane react with NaCo(CO)₄ in ether at low temperatures to give silyltetracarbonylcobalt, SiH₃Co(CO)₄, and silylenebis(tetracarbonylcobalt), SiH₂[Co(CO)₄]₂, respectively. Physical properties of both compounds are reported, together with i.r., mass, and n.m.r. spectra of SiH₃Co(CO)₄. Pyrolysis of gaseous SiH₃Co(CO)₄ at 120° yields H₂, CO, SiH₄, and a dark-coloured inert solid; some HCo(CO)₄ is also present in the early stages. The stoicheiometry and probable cross-linked polymeric nature of the solid product are inferred, and its metal coating properties are outlined. The Si–Co bond in SiH₃Co(CO)₄ is broken by HX (X = F, Cl, O/2) to give SiH₃X and HCo(CO)₄, also by HgX₂(X = Cl, I) to give SiH₃X and Hg[Co(CO)₄]₂. SiH₂[Co(CO)₄]₂ behaves similarly. No insertion of CO into the Si–Co bond has been achieved; PPh₃ reacts slowly with SiH₃Co(CO)₄ to displace CO and probably yields trans-SiH₃Co(CO)₃(PPh₃). Evidence for d_π–d_π interaction in the silicon–metal bond is discussed.