Silylcobalt carbonyl

Several silylcobalt carbonyls were isolated and shown to be formed according to the stoichiometry of Eq. (74). Since the silylcobalt carbonyls were found to be inactive as catalysts, it was concluded that catalyst deactivation resulted from Eq. (73). This was obviated by the use of an excess of olefin to facilitate Eq. (71). 

However, no evidence in support of this could be found from reactions of silylcobalt carbonyls with an equivalent of cobalt hydrocarbonyl in an olefin. Inclusion of an equivalent of silicon hydride in the latter reaction resulted in the formation of some alkylsilane derived from the silicon moiety of the silylcobalt carbonyl. This result was shown to arise from a facile exchange reaction as in Eq. (76), however. 

Siloxymethylation.3 Glycosyl acetates undergo C-siloxymethylation on reaction with a hydrosilane and CO catalyzed by Co2(CO)8. Only the anomeric acetoxy group undergoes this reaction, which takes place from the side opposite to that of the acetoxy group at C3. The reactive reagent is probably a silylcobalt carbonyl, R3SiCo(CO)4. 

Fig. 2. Pressure vessel for the synthesis of substituted silylcobalt carbonyls.

Silicon-hydrogen bonds also add to dinuclear complexes in reactions that are formally one-electron oxidative additions, or simply metal-metal bond cleavage reactions. The reaction of dicobalt octacarbonyl with an excess of silane leads to silylcobalt carbonyls (equation 13)2 3. Similar reactions involving Mn-Mn29, Re-Re30, Fe-Fe31, Ru-Ru32,... 

The investigations described so far indicate that reactions of metal carbonylates in general lead only to the coordination of two metal carbonyl groups to the 1,3,5-trisilacyclohexanes. From the chemistry of silylcobalt compounds it is known that silanes of the type R SiH (n = 1-3) cleave dinuclear Co2(CO)g, producing silyl-cobalt-carbonyl complexes [166, 167, 171]. 

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