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Manganese 1,4,7-trimethyl-1,4,7-triazacyclononane complexes: Versatile catalysts for the oxidation of organic compounds with hydrogen peroxide

2006; Elsevier BV; Volume: 251; Issue: 1-2 Linguagem: Inglês

10.1016/j.molcata.2006.02.025

1873-314X

John R. Lindsay Smith, Bruce C. Gilbert, Antoni Mairata i Payeras, Jane Murray, Terry R. Lowdon, John Oakes, Roger Pons i Prats, Paul H. Walton,

Metal complexes synthesis and properties

The oxidation of phenols, cinnamic acids and methyl aryl sulfides by hydrogen peroxide, using three catalyst systems, [L2Mn2IV(μ-O)3](PF6)2, L = 1,4,7-trimethyl-1,4,7-triazacyclononane; [LMnIV(OMe)3(PF6); and MnII/L/H2O2, have been studied. The results from a combination of spectroscopic and kinetic studies, coupled with Hammett correlations and 18O 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.