The Mechanism of Photo-substitution of Ferrocene in Haloalkane–Ethanol Solutions

Abstract

Abstract The mechanism of photo-substitution of ferrocene in haloalkane–ethanol solutions was investigated by the flash photolysis technique and other chemical methods mainly on the ferrocene–carbon tetrachloride–ethanol system. The photoreaction is initiated by the excitation of charge transfer state (electron transfer from ferrocene to carbon tetrachloride). In the absence of ethanol, CT-excitation leads to the decomposition of ferrocene to FeCl3 with first order reaction kinetics of k=(1.6±0.5)×105 s−1. The formation of FeCl3 was inhibited by ethanol effectively to give ethyl ferrocenecarboxylate. Diethylamine quenched the formation of FeCl3, whereas dimethyl sulfoxide, a stronger base than ethanol, is a less effective quencher than ethanol. These facts suggest that the most important role of ethanol is to ethanolyse trichloromethylferrocene, which otherwise decomposes to FeCl3.