On the oxidation of alkyl and aryl sulfides by [(Me3TACN)MnVO(OH)2]+:: A density functional study

Density functional theory suggests that the formal 2-electron oxidation of sulfides, RR'S, to sulfoxides, (RR2S)-S-'=O by the model Mn-V=O catalyst, [(TACN)(MnO)-O-V(OH)(2)](+), proceeds in two quite distinct 1-electron steps. Transfer of the first electron is barrierless and generates a sulfur radical cation, antiferromagnetically coupled to a Mn-IV centre via a covalent mu-oxo bridge. The second electron-transfer step is accompanied by migration of the oxygen atom to the sulfur centre, and is rate-determining. The absence of a barrier in the first step, where a sulfur radical is formed, means that the presence of electron-donating or withdrawing substituents on the sulfide has only a minor impact on the rate of reaction. (C) 2007 Elsevier B.V. All rights reserved.