Fine Control of the Redox Reactivity of a Nonheme Iron( III)-Peroxo Complex by Binding Redox-Inactive Metal Ions

Abstract

Redox-inactive metal ions are one of the most important co-factors involved in dioxygen activation and formation reactions by metalloenzymes. In this study, we have shown that the logarithm of the rate constants of electron-transfer and C-H bond activation reactions by nonheme iron(III)-peroxo complexes binding redox-inactive metal ions, [(TMC)Fe-III(O-2)](+)-Mn+ (Mn+=Sc3+, Y3+, Lu3+, and La3+), increases linearly with the increase of the Lewis acidity of the redox-inactive metal ions (Delta E), which is determined from the g(zz) values of EPR spectra of O-2(center dot-)-Mn+ complexes. In contrast, the logarithm of the rate constants of the [(TMC)Fe-III(O-2)](+)-Mn+ complexes in nucleophilic reactions with aldehydes decreases linearly as the Delta E value increases. Thus, the Lewis acidity of the redox-inactive metal ions bound to the mononuclear nonheme iron(III)-peroxo complex modulates the reactivity of the [(TMC)Fe-III(O-2)](+)-Mn+ complexes in electron-transfer, electrophilic, and nucleophilic reactions.