Issue 45, 2019

Base-controlled mechanistic divergence between iron(iv)-oxo and iron(iii)-hydroperoxo in the H2O2 activation by a nonheme iron(ii) complex

Abstract

Activation of hydrogen peroxide by FeII salts (Fenton systems) leads to a myriad of oxidizing agents whose nature, FeIVO, or hydroxyl radicals and FeIII species, is dictated by the reaction conditions, in particular the pH value. Using the non heme FeII complex [FeII(L52)(CH3CN)]2+ (1) (where L52 is the pentadentate ligand N-methyl-N,N′,N′-tris(2-pyridylmethyl)ethane-1,2-diamine) we have observed the simultaneous formation of two reaction intermediates, [FeIV(O)(L52)]2+ and [FeIII(OOH)(L52)]2+, in its reaction with excess hydrogen peroxide in the presence of sub-stoichiometric amounts of triethylamine. Kinetic and spectroscopic monitoring of the reaction mixture and of independently prepared [FeIV(O)(L52)]2+ in the presence of the different constituents of the reaction mixture allows drawing a mechanistic scheme. These two reactive species are formed simultaneously following two independent and competitive pathways. [FeIV(O)(L52)]2+ is obtained via heterolytic O–O cleavage of the oxidant assisted by the base in a peroxidase-like mechanism whereas [FeIII(OOH)(L52)]2+ is generated upon homolytic O–O cleavage of hydrogen peroxide. The relative contribution of these two pathways can be tuned by adjusting the amount of base used.

Graphical abstract: Base-controlled mechanistic divergence between iron(iv)-oxo and iron(iii)-hydroperoxo in the H2O2 activation by a nonheme iron(ii) complex

Supplementary files

Article information

Article type
Paper
Submitted
28 aug 2019
Accepted
28 okt 2019
First published
28 okt 2019

Dalton Trans., 2019,48, 17045-17051

Base-controlled mechanistic divergence between iron(IV)-oxo and iron(III)-hydroperoxo in the H2O2 activation by a nonheme iron(II) complex

A. Bohn, C. Chinaux-Chaix, K. Cheaib, R. Guillot, C. Herrero, K. Sénéchal-David, J. Rebilly and F. Banse, Dalton Trans., 2019, 48, 17045 DOI: 10.1039/C9DT03487K

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