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O−O Bond Formation and Liberation of Dioxygen Mediated by N 5 ‐Coordinate Non‐Heme Iron(IV) Complexes
Author(s) -
Kroll Nicole,
Speckmann Ina,
Schoknecht Marc,
Gülzow Jana,
Diekmann Marek,
Pfrommer Johannes,
Stritt Anika,
Schlangen Maria,
Grohmann Andreas,
Hörner Gerald
Publication year - 2019
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201903902
Subject(s) - chemistry , hydrogen peroxide , peroxide , catalysis , bond cleavage , photochemistry , heme , oxygen , catalase , stereochemistry , kinetic isotope effect , organic chemistry , enzyme , deuterium , physics , quantum mechanics
Formation of the O−O bond is considered the critical step in oxidative water cleavage to produce dioxygen. High‐valent metal complexes with terminal oxo (oxido) ligands are commonly regarded as instrumental for oxygen evolution, but direct experimental evidence is lacking. Herein, we describe the formation of the O−O bond in solution, from non‐heme, N 5 ‐coordinate oxoiron(IV) species. Oxygen evolution from oxoiron(IV) is instantaneous once meta ‐chloroperbenzoic acid is administered in excess. Oxygen‐isotope labeling reveals two sources of dioxygen, pointing to mechanistic branching between HAT (hydrogen atom transfer)‐initiated free‐radical pathways of the peroxides, which are typical of catalase‐like reactivity, and iron‐borne O−O coupling, which is unprecedented for non‐heme/peroxide systems. Interpretation in terms of [Fe IV (O)] and [Fe V (O)] being the resting and active principles of the O−O coupling, respectively, concurs with fundamental mechanistic ideas of (electro‐) chemical O−O coupling in water oxidation catalysis (WOC), indicating that central mechanistic motifs of WOC can be mimicked in a catalase/peroxidase setting.