Insights from kinetic studies of photo-generated compound II models: Reactivity toward aryl sulfides.

Insights from kinetic studies of photo-generated compound II models: Reactivity toward aryl sulfides.
J Inorg Biochem. 2018 Mar 09;183:58-65
Authors: Lee NF, Patel D, Liu H, Zhang R
Abstract
Iron(IV)-oxo porphyrins [FeIV(Por)O] (Por = poprhyrin), commonly called compound II models, were produced in three electron-deficient ligands by visible light irradiation of highly photo-labile porphyrin-iron(III) bromates or chlorates. The kinetics of oxygen transfer atom (OAT) reactions with aryl sulfides by these photo-generated [FeIV(Por)O] (3) were studied in CH3CN solutions. The iron(IV)-oxo porphyrins under study include 5,10,15,20-tetra(2,6-dichlorophenyl)porphyrin-iron(IV)-oxo (3a), 5,10,15,20-tetra(2,6-difluorophenyl)porphyrin-iron(IV)-oxo (3b), and 5,10,15,20-tetra(pentafluorophenyl)porphyrin-iron(IV)-oxo (3c). As expected, complexes 3 were competent oxidants and reacted rapidly with thioanisoles to give the corresponding sulfoxides with minor over-oxidation sulfones. Apparent second-order rate constants determined under pseudo-first-order conditions for sulfide oxidation reactions are (9.8 ± 0.1) × 102-(3.7 ± 0.3) × 101 M-1 s-1, which are 3 to 4 orders of magnitude greater in comparison to those of alkene epoxidations and activated CH bond oxidations by the same oxo species. Conventional Hammett analyses gave non-linear correlations, indicating no significant charge developed at the sulfur during the oxidat...

Source: Journal of Inorganic Biochemistry - March 9, 2018 Category: Biochemistry Authors: Lee NF, Patel D, Liu H, Zhang R Tags: J Inorg Biochem Source Type: research