The oxidation of phenols, cinnamic acids and methyl aryl sulfides by hydrogen peroxide, using three catalyst systems, [L2Mn2IV(mu-O)(3)](PF6)(2), L=1,4,7-trimethyl-1,4,7-triazacyclononane; [LMnIV(OMe)(3)(PF6); and Mn-II/L/H2O2, have been studied. The results from a combination of spectroscopic and kinetic studies, coupled with Hammett correlations and O-18 labelling experiments, suggest that with each system the active oxidant is an electrophilic, mononuclear oxo-manganese (V) species. The influence of additives that can act as co-ligands for the manganese species has been investigated, with a view to controlling the activity/selectivity of the active oxidant. The two-step, sulfide-sulfoxide-sulfone, oxidation shows an unusual switch in the philicity of the active oxidant from electrophilic in the first step to nucleophilic in the second. Mechanisms for the oxidations are proposed. (c) 2006 Elsevier B.V. All rights reserved.