Kinetic studies on the interactions of manganese–porphyrins with peracetic acid. Part 1. Epoxidation of alkenes and hydroxylation of aromatic rings

Abstract

The mechanism of peracetic acid interactions with Mn^III complexes of meso-tetra(2,6-dichloro-4-R-phenyl)porphyrins (RTDCPPMnCl; R = CH₃O, H, Br, Cl or NO₂) in acetonitrile–acetic acid has been studied. Analysis of the kinetic data revealed that both in cis-stilbene epoxidation and naphthalene hydroxylation the first step of the reaction is the reversible formation of an intermediate adduct ‘A’ between the catalyst and the oxidant. The subsequent irreversible transformation of ‘A’ with rate constant k₂ leads to the formation of two high-valent oxometallo species, [RTDCPPMn^V(O)] and supposedly [RTDCPPMn^IV(O)]^+·. These species are in equilibrium and show distinct oxidation abilities towards the substrates.