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

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)FeIII (O2 )]+ -Mn+ (Mn+ =Sc3+ , Y3+ , Lu3+ , and La3+ ), increases linearly with the increase of the Lewis acidity of the redox-inactive metal ions (ΔE), which is determined from the gzz values of EPR spectra of O2.- -Mn+ complexes. In contrast, the logarithm of the rate constants of the [(TMC)FeIII (O2 )]+ -Mn+ complexes in nucleophilic reactions with aldehydes decreases linearly as the ΔE 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)FeIII (O2 )]+ -Mn+ complexes in electron-transfer, electrophilic, and nucleophilic reactions.