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 (O )] -M (M =Sc , Y , Lu , and La ), increases linearly with the increase of the Lewis acidity of the redox-inactive metal ions (ΔE), which is determined from the g values of EPR spectra of O -M complexes. In contrast, the logarithm of the rate constants of the [(TMC)Fe (O )] -M 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)Fe (O )] -M complexes in electron-transfer, electrophilic, and nucleophilic reactions.

The Influence of Alkali Metal Ions on the Stability and Reactivity of Chromium(III) Superoxide Moieties Spanned by Siloxide Ligands

“…Due to a slight pseudosymmetryt owards the space group Pbca,t here are two molecules with similar bond lengthsp resenti nt he unit cell. The arithmetic mean of the OÀOb ond lengths of the two molecules [O7ÀO8 1.334 (7) and O20ÀO21 1.324 (7) ]p resent in the unit cell, namely 1.33 ,i sa lmosti dentical to that determined for 2 [1.334(4) ]and rathersimilar to the OÀOd istance calculatedm erely for O 2 À· ÀNa + (1.34 ). [15] The coordination sphereo fe ach sodium ion in 5·THF is saturated by two THF molecules.…”

“…In previous studies performed by Bae et al. on an iron peroxo complex, a close correlation between the reactivity and the Lewis acidity of the added metals was found . However, such a clear correlation of the reactivity with the Lewis acidity was unlikely to be observed for the chromium superoxide series described above.…”

“…[5,6] In contrastt ot his, it was also shown that the additiono fL ewis acids such as Sc III ,Y III , Lu III ,o rL a III enhances the reactivity of an on-hemei ron(III) peroxoc omplex in single-electron transfer and electrophilic reactions. [7] Moreover,O hkuboe tal. observedt hat the rate of the one-electron conversion of O 2 to as uperoxide ion is directly correlatedw ith the Lewis aciditieso fa dded redox-inactive metali ons, underlining that these indeed play an important role in dioxygen activation.…”

“…For instance, the intermediate formed in a reaction of a cobalt complex with O 2 could be stabilized in the presence of metal ions such as Sc III , Zn II or Ce III , which allowed for a spectroscopic analysis of the transient species . In contrast to this, it was also shown that the addition of Lewis acids such as Sc III , Y III , Lu III , or La III enhances the reactivity of a non‐heme iron(III) peroxo complex in single‐electron transfer and electrophilic reactions . Moreover, Ohkubo et al.…”

Electro‐kinetic Separation of Rare Earth Elements Using a Redox‐Active Ligand

“…[19] As imilar influence of Lewis acidity on the rates of electron transfer from bromoferrocene to nonheme iron(III)-peroxo complexes binding RE 3+ ions was reported. [20] (Figure 3a nd Table S10). Computed separations of these binary mixtures showed that the RE-TriNOx compounds with higher homogeneous oxidation rates were enriched in the oxidized fraction and those with lower homogeneous oxidation rates in the unoxidized fraction.…”