Behaviour of 1,3-diferrocenylalkenes and 1,2-diferrocenylethylene in strong acid. Apparent intramolecular reduction of α-ferrocenyl carbocations

Abstract

The reactions of 1,3-diferrocenylalkenes and 1,2-diferrocenylethylene in 98% sulphuric acid are described. Reduction of the alkene to an alkane occurs concomitant with oxidation of the two iron atoms to the Fe^III state. The reaction is considered to involve a novel intramolecular electron transfer from the iron to a carbocation centre in a ferrocene molecule. The behaviour of 2-ferrocenylpropan-2-ol in concentrated sulphuric acid yielding 2,4-diferrocenyl-2-methylpentane is rationalized by the same mechanism.