Mechanistic tuning of hydrocarbon oxidations with H₂O ₂, catalyzed by hexacoordinate ferrous complexes

A comparison of the catalytic properties of a series of Fe^IILXY 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.