Demonstration of the Heterolytic OO Bond Cleavage of Putative Nonheme Iron(II)OOH(R) Complexes for Fenton and Enzymatic Reactions

Abstract

One‐electron reduction of mononuclear nonheme iron(III) hydroperoxo (FeIIIOOH) and iron(III) alkylperoxo (FeIIIOOR) complexes by ferrocene (Fc) derivatives resulted in the formation of the corresponding iron(IV) oxo complexes. The conversion rates were dependent on the concentration and oxidation potentials of the electron donors, thus indicating that the reduction of the iron(III) (hydro/alkyl)peroxo complexes to their one‐electron reduced iron(II) (hydro/alkyl)peroxo species is the rate‐determining step, followed by the heterolytic OO bond cleavage of the putative iron(II) (hydro/alkyl)peroxo species to give the iron(IV) oxo complexes. Product analysis supported the heterolytic OO bond‐cleavage mechanism. The present results provide the first example showing the one‐electron reduction of iron(III) (hydro/alkyl)peroxo complexes and the heterolytic OO bond cleavage of iron(II) (hydro/alkyl)peroxo species to form iron(IV) oxo intermediates which occur in nonheme iron enzymatic and Fenton reactions.

A Chromium(III)‐Superoxo Complex as a Three‐Electron Oxidant with a Large Tunneling Effect in Multi‐Electron Oxidation of NADH Analogues

“…Thus,a no verall reaction is summarized in [Eq. (1) [25] It was also confirmed that no reaction occurred between BNA + and OH À in deaerated MeCN (Supporting Information, Figure S2b) when BNA + was produced in the oxidation of BNAH by H 2 O 2 in the presence of Fe(ClO 4 ) 3 (Supporting Information, Figure S2a). This is explained by the resonance structures of the amide group in BNA by ESI-MS and electron paramagnetic resonance (Supporting Information, Figure S4 for UV/Vis and ESI-MS, Figure S5 for EPR).…”

Highly Selective and Catalytic Oxygenations of C−H and C=C Bonds by a Mononuclear Nonheme High‐Spin Iron(III)‐Alkylperoxo Species

“…[4,[7][8][9] Theb ioinspired studies provided useful information about the electronic and structural features of these intermediates and their use in the generation of high-valent iron-oxo species. [3,4,8,[10][11][12][13][14] While the heterolytic O À Ob ond cleavage of ad ioxygen-derived Fe-OOR(H) intermediate forms ahigh-valent iron-oxo species in enzymatic systems, [2,6] the O À O/Fe À Ob onds of synthetic Fe III ÀOOR(H) are often cleaved homolytically. [14][15][16] Among other factors,s pin states of the metal center have been reported to play important roles in modulating the strength of FeÀOand OÀObonds,and their cleavage in nonheme Fe III À OOR species.…”

Selective Formation of an FeIVO or an FeIIIOOH Intermediate From Iron(II) and H2O2: Controlled Heterolytic versus Homolytic Oxygen–Oxygen Bond Cleavage by the Second Coordination Sphere

“…[14][15][16][17] Only af ew examples of nonheme Fe II complexes have shown the direct formation of an Fe IV -oxo from their reaction with H 2 O 2 , [18,19] or from the evolution of ap utative Fe II OOH(R) intermediate. [20] Que et al reported the nearly quantitative formation of [Fe IV O(TMC)] 2+ from [Fe II -(TMC)] 2+ and H 2 O 2 in the presence of 2,6-lutidine. [18] DFT calculations showed that lutidine acted as ageneral base that promoted the proton transfer from the proximal to the distal Oatom, thus facilitating the heterolytic O À Ocleavage.…”