Cardiff University | Prifysgol Caerdydd ORCA
Online Research @ Cardiff 
WelshClear Cookie - decide language by browser settings

Regioselectivity of substrate hydroxylation versus halogenation by a nonheme iron(IV)-oxo complex: possibility of rearrangement pathways

Quesne, Matthew and De visser, S. P. 2012. Regioselectivity of substrate hydroxylation versus halogenation by a nonheme iron(IV)-oxo complex: possibility of rearrangement pathways. Journal of Biological Inorganic Chemistry 17 (6) , pp. 841-852. 10.​1007/​s00775-012-0901-4

Full text not available from this repository.

Abstract

Several nonheme iron enzymes and biomimetic model complexes catalyze a substrate halogenation reaction. Recent computational studies (Borowski et al. J Am Chem Soc 132:12887–12898, 2010) on α-ketoglutarate dependent halogenase proposed an initial isomerization reaction that is important to give halogenated products. We present here a series of density functional theory calculations on a biomimetic model complex—[FeIV(O)(TPA)Cl]+, where TPA is tris(2-pyridylmethyl)amine—and investigate the mechanisms of substrate halogenation versus hydroxylation using the reactant and its isomer where the oxo and chloro groups have changed positions. We show here that the reactions occur on a dominant quintet spin state surface, although the reactants are in a triplet state. Despite the fact that the reactants can exist in two stable isomers with the oxo group either trans or cis to the axial ligand, they react differently with substrates, where one gives dominant hydroxylation and the other gives dominant chlorination of substrates. The ligand in the cis position of the oxo group is found to be active in the reaction mechanism and donated to the substrate during the reaction. A detailed thermochemical analysis of possible reaction mechanisms reveals that the strengths of the Fe–OH and Fe–Cl bonds in the radical intermediates are the key reasons for this regioselectivity switch of hydroxylation over halogenation. This study highlights the differences between enzymatic and biomimetic halogenases, where the former only react after an essential isomerization step, which is not necessary in model complexes.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Chemistry
Subjects: Q Science > QD Chemistry
Publisher: SpringerLink
ISSN: 0949-8257
Date of Acceptance: 24 April 2012
Last Modified: 04 Jun 2017 08:58
URI: http://orca-mwe.cf.ac.uk/id/eprint/88640

Actions (repository staff only)

Edit Item Edit Item