Protodemercuration of some mercury derivatives of ferrocene and cyclopentadienylmanganese tricarbonyl

Abstract

The protolysis of some symmetrical and asymmetrical mercury derivatives of ferrocene and cyclopentadienylmanganese tricarbonyl in 90% dioxane has been described. In this reaction the ferrocenyl radical was found to be more electron-attracting than the p-anisyl radical, while the cyclopentadienylmanganese-tricarbonyl radical behaved as a weak acceptor with respect to the phenyl radical. The protodemercuration of diferrocenylmercury proceeds about 130 times more rapidly than that of ferrocenylmercury chloride, and the protolysis of bis(cyclopentadienylmanganese-tricarbonyl)mercury is 30 times faster than the protolysis of cyclopentadienylmanganese-tricarbonylmercury chloride. The protodemercuration of diferrocenylmercury with perchloric acid is about half that with hydrochloric acid As in the case of diphenylmercury, the addition of potassium chloride increases the reaction rate in the protolysis with both perchloric and hydrochloric acids. It was shown that the sensitivities of the mercury atoms in diferrocenylmercury and in diphenylmercury to nucleophilic assistance are approximately equivalent. The effect of the water content of dioxane on the rate of protodemercuration of diferrocenylmercury, bis-(cyclopentadienylmanganese-tricarbonyl)mercury and diphenylmercury has been studied. The rates of decompositions of all three compounds were found to decrease with increase in the water content of dioxane. It was also shown that the mechanisms of protodemercuration of diferrocenylmercury and bis(cyclopentadienylmanganese-tricarbonyl)mercury do not differ in principle from that of diphenylmercury and the explanation does not require the participation of the metal atom in any form in the stage determining the reaction rate.