Some chemistry of Group IVB-cobalt carbonyl compounds

Abstract

The reaction of MeGeH₃ and Co₂(CO)₈ has been reinvestigated. Products obtained from this reaction include MeGeCo₃(CO)₁₁, Me₂Ge₂Co₄(CO)₁₄ (or [MeGeCo(CO)₄]₂Co₂(CO)₆), MeGeHCo₂(CO)ₓ (x = 7 or 8), (MeGe)₂Co₄(CO)₁₁ and Co₄(CO)₁₂, the relative proportion depending on the ratio of the reactants. Decarbonylation of a mixture of Me₂Ge₂Co₄(CO)₁₄, MeGeCo₃(CO)₁₁ and MeGeHCo₂(CO)ₓ produced a small amount of (MeGe)₂Co₄(CO)₁₁ together with a new compound Me₃Ge₃Co₅(CO)₁₄ (or (MeGe)₂Co₄(CO)₁₀(μ-Ge(Me)Co(CO)₄)) which was characterised by a full crystal structure. The crystal structure of MeGeCo₃(CO)₁₁ was also determined. A new, convenient and efficient route to (MeM')₂Co₄(CO)₁₁ (M'= Si, Ge) clusters has been developed, based on the reaction of MeM'H₃ with Co₄(CO)₁₂. Reactions of RGeH₃ (R= Me, Et, Ph) with M'Co₄(CO)₁₄ (M'= Si, Ge) have been investigated in detail. (RGeH)ₙGeCo₄(CO)₁₄₋ₙ (n= 1 or 2) were obtained from the GeCo₄(CO)₁₄ system. Further reaction of the products with Co₂(CO)₈ produced two new clusters : RGe₂Co₅(CO)₁₅ (or (RGe)Co₄(CO)₁₁(GeCo(CO)₄)) (R= Me, Ph) from the (RGeH)GeCo₄(CO)₁₃ reaction and R₂Ge₃Co₆(CO)₁₇ (or (RGe)₂Co₄(CO)₁₀(μ-GeCo₂(CO)₇) from the (RGeH)₂GeCo₄(CO)₁₂ reaction. Representative X-ray crystal structures of MeGe₂Co₅(CO)₁₅ and Et₂Ge₃Co₆(CO)₁₇ are described. With SiCo₄(CO)₁₄, MeGeH₃ produced a mixture of compounds, including the new compound RGeSiCo₅(CO)₁₅ (or (RGe)Co₄(CO)₁₁(SiCo(CO)₄), characterised by a full crystal structure), (RGe)₂Co₄(CO)₁₁, Me₃Ge₃Co₅(CO)₁₄, SiCo₄(CO)₁₃, Co₄(CO)₁₂ and Co₂(CO)₈. RR'GeH₂ (R= Me, R'=Me, Cl) reacted with GeCo₄(CO)₁₄ to form (RR'Ge)GeCo₄(CO)₁₃ and (RR'Ge)₂GeCo₄ (CO)₁₂ depending on the reaction conditions. Preliminary studies on the reaction of Me₂GeH₂ with SiCo₄(CO)₁₄ indicated that Me₂GeCo₂(CO)₇, Me₂GeCo₂(CO)₈ (Me₂Ge)₂Co₂(CO)₆ and SiCo₄(CO)₁₃ were formed. The reaction of MeSiH₃ with GeCo₄(CO)₁₄ resulted only in the decarbonylation of GeCo₄(CO)₁₄ to GeCo₄(CO)₁₃. However, in the reaction of MeSiH₃ with SiCo₄(CO)₁₄, a number of products were formed. These include MeSiH₂Co(CO)₄, Co₂(CO)₈, SiCo₄(CO)₁₃ and a new product of formula MeSi₂Co₅(CO)₁₅ (or (MeSi)Co₄(CO)₁₁(SiCo(CO)₄). Preliminary studies on the following reactions were also carried out: the reaction of Me₂SiH₂ with M'Co₄(CO)₁₄ and the reaction of Me₂SiH₂ with Co₄(CO)₁₂. In the GeCo₄(CO)₁₄ system no reaction other than the decarbonylation of GeCo₄(CO)₁₄ to GeCo₄(CO)₁₃ was observed. In both the SiCo₄(CO)₁₄ and Co₄(CO)₁₂ systems, Me₂SiHCo(CO)₄, Me₂[Co(CO)₄]SiOCCo₃(CO)₉, Co₂(CO)₈ and Co₄(CO)₁₂ were obtained. All new products in this study were fully characterised by infrared, ¹H NMR, ¹³CO NMR and mass spectroscopy, and for most, by X-ray crystallography. Some ¹³CO NMR studies on M'-Co carbonyl compounds are also reported.