Alkylation of Tricarbonyl Iron Complexes by Trimethylsilyl Cyanide - Synthetic and Kinetic Studies

Trimethylsilyl cyanide has been shown to be a synthetically useful reagent for the alkylation of tricarbonyl(η5-cyclohexadienyl)iron(1+) salts, particularly in cases where the reactive terminus of the dienyl system bears an alkyl substituent. The reaction proceeds via the isocyanide isomer, with a rate-limiting pre-equilibration of the reagent. In cases where reactive metal complexes were used, the rate of reaction was proportional to the concentration of Me3SiCN, and was independent of both the nature and concentration of the dienyl salt. In the case of the deactivated 2-methoxy substituted dienyl salt, non-linear rate plots indicated a change in the rate-limiting step.