HOW ELECTROPHILIC ARE FERROCENYLMETHYL CATIONS - KINETICS OF THEIR REACTIONS WITH PI-NUCLEOPHILES AND HYDRIDE DONORS

Second-order rate constants for the reactions of the ferrocenylmethyli um ions 2a-e with silyl enol ethers, allylsilanes, allylstannanes, and hydride donors have been determined photometrically and conductometri cally in dichloromethane. The ferrocenylmethylium ions 2a-d (fc-CHR(+) , R = H, Me, Ph, An) are slightly stronger electrophiles than the trop ylium ion, and their electrophilic reactivities depend only slightly o n the nature of R. The bis(ferrocenyl)methylium ion 2e is a considerab ly weaker electrophile, comparable to the tricarbonyl(cyclohexadienyl) iron cation.