Mechanistic tuning of hydrocarbon oxidations with H2O2, catalyzed by hexacoordinate ferrous complexes

A comparison of the catalytic properties of a series of (FeLXY)-L-II complexes on oxidation reactions with H2O2, [L = N,N'-bis(pyridin-2-yl-methyl)-N,N'-bis(3,4,5-trimethoxybenzyl)- ethane-1,2-diamine] indicates that the lability of the X and Y ligands (Cl- or CH3CN) determines the nature of the oxidation pathway. The absence of a labile site in the complex, i.e. when X = Y = Cl-, causes the reaction to proceed via a Fenton pathway (generation of hydroxyl radicals, exclusively), The presence of two labile CH3CN ligands (X = Y = CH3CN) allows the catalysis to proceed through a metal-based mechanism, whereas in the case of a complex with only one labile ligand (X = Cl- and Y = CH3CN), the reaction is less controlled by the metal. We wish to emphasize that the cleavage of the O-O bond in the Fe-OOH moeity, a key intermediate in the reaction, is different in the last two cases. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).