Ligand driven heterolytic O-O bond cleavage in a non-haem phenolato-Fe(III)-OOH complex to yield a formal Fe(V)O intermediate.

Authors

Daniël R Duijnstee, Marika Di Berto Mancini, C Maurits de Roo, Duenpen Unjaroen, Moniek Tromp, Ronald Hage, Wesley R Browne, Marcel Swart

Published in

Dalton transactions (Cambridge, England : 2003). Sep 15, 2025. Epub Sep 15, 2025.

Abstract

Fe(V)O species can be generated by the heterolytic cleavage of the O-O bond of corresponding Fe(III)-OOH species. In haem complexes the redox non-innocence of the ligand facilitates such heterolytic cleavage, however non-haem iron complexes generally show homolytic cleavage to form an Fe(IV)O species and a hydroxyl radical. The hydroxyl radical formed is undesirable due to its non-selective reactivity. Here we show that the redox non-innocence of a phenolato ligand moiety in the complex [LFe(III)(μ-O)Fe(III)L]²⁺, where L is 2-(((di(pyridin-2-yl)methyl)(pyridin-2-ylmethyl)amino)methyl)phenolate, facilitates heterolytic O-O bond cleavage, similar in manner to that observed with haem Fe(III)-OOH species, to yield a formal Fe(V)O intermediate. Although not observed directly, the intermediacy of an Fe(V)O species is manifested in the immediate appearance of a doubly oxidised bis-phenolato bridged complex observed by time resolved UV/vis absorption and resonance Raman spectroscopy. This complex is formed by C-C coupling at the para position of the phenolato moiety of the ligand. The pathways to form the final complex via various Fe(IV)O and Fe(V)O intermediates are investigated by DFT methods, which indicate that the impact of the phenolato moiety is due to its redox non-innocence primarily. The ability of the phenolato moiety to transfer charge and spin density induces a switch in the mechanism of O-O bond cleavage from homolytic to heterolytic manifested in the radical character at the para-position needed for C-C bond formation and the high oxidation state of the first observed product.

PMID:
40952677
Bibliographic data and abstract were imported from PubMed on 15 Sep 2025.

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