Ferrocene/ferrocenium ion as a catalyst for the photodecomposition of chloroform

Irradiation (λ > 320 nm) of ferrocene in chloroform causes decomposition of chloroform and the accumulation of HCl, CCl₃OOH, and C₂Cl₆. This appears to occur initially through a cycle in which (a) ferrocene is oxidized to ferrocenium and tetrachloroferrate ions, (b) FeCl₄ ⁻ undergoes photodissociation, and (c) ferrocenium reoxidizes the chloroferrate(II) species. On extended photolysis, the concentrations of CCl₃OOH and FeCl₄ ⁻ build up and a competing cycle in which FeCl₄ ⁻ is restored through oxidation of the chloroferrate(II) species by CCl₃OOH accelerates the decomposition rate.