Abstract
The ligand N,N′‐bis(6‐methyl‐2‐pyridylmethyl)‐N,N′‐bis(2‐pyridylmethyl)ethane‐1,2‐diamine (L~6~^2^2M) has allowed to prepare the new Fe^II^ complex [(L~6~^2^2M)FeCl~2~] (1), and to compare its structural and spectroscopic characteristics with [(L~6~^2^2M)FeCl]PF~6~ (2). The molecular structure of 1, resolved by X‐ray diffraction, exhibits the ligand tetracoordinated with the two non‐methylated pyridine rings coordinated. As shown by UV/Vis spectroscopy and cyclic voltammetry, upon dissolution in methanol or acetonitrile, one chloride ion is released and replaced by a pyridine group. Therefore, complexes 1 and 2 adopt identical structures in solution, i.e. [(L~6~^2^2M)FeCl^+^. However, upon oxidation complex 1 gives several ferric complexes with the ligand L~6~^2^2M pentacoordinated, or tetracoordinated with two chloride ions. This peculiar behaviour is due to the presence of chloride ions in solution in the case of 1. Upon reaction with H~2~O~2~ in methanol, complex 2 leads to the formation of low‐spin [(L~6~^2^2M)Fe^III^(OOH)^2+^, whereas it is not observed in the case of 1. Based on the presence or not of chloride ions in solution, a mechanism is proposed for the reactivity of complexes 1 and 2 toward H~2~O~2~. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)