Oxidation of hydroquinones by a nonheme iron(IV)-oxo species

The reactivity of an isolated, well-characterized nonheme iron(IV)-oxo complex, [(TMC)FeIV O]2+ (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), has been examined in the oxidation of hydroquinones. This complex has been shown to oxidize a series of hydroquinones, resulting in the production of the corresponding quinone products. Kinetic studies performed with substituted hydroquinones revealed a good correlation between reaction rates of the iron(IV)-oxo complex and the electron-donating ability of the substituents and the bond dissociation energy (BDE) of substrate O–H bonds. These results with a kinetic isotope effect (KIE) of 2.7 led us to propose a hydrogen-atom abstraction mechanism for the oxidation of hydroquinones by the nonheme iron(IV)-oxo species.