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

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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

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Publication details

The article was received on 28 Aug 2019, accepted on 28 Oct 2019 and first published on 28 Oct 2019


Article type: Paper
DOI: 10.1039/C9DT03487K
Dalton Trans., 2019, Advance Article

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    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, Advance Article , DOI: 10.1039/C9DT03487K

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