Mechanistic Tuning of Hydrocarbon Oxidations with H 2 O 2 , Catalyzed by Hexacoordinate Ferrous Complexes

A comparison of the catalytic properties of a series of Fe II LXY complexes on oxidation reactions with H 2 O 2 , [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 CH 3 CN) 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 CH 3 CN ligands (X = Y = CH 3 CN) 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 = CH 3 CN), 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. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)