One-pot synthesis, physicochemical characterization and crystal structures of cis- and trans-(1,4,8,11-tetraazacyclotetradecane)-dichloroiron(III) complexes†

Abstract

The synthesis and characterization of cis- and trans-[Fe(cyclam)Cl₂]⁺ (cyclam = 1,4,8,11-tetraazacyclotetradecane) are described. The assignment of geometrical configuration to these complexes has been made on the basis of their infrared spectra in the 800–900 cm^–1 region. In addition, the molecular structures of the cis and trans derivatives were determined by X-ray diffraction. Both complexes have a d⁵ electronic system, the cis and trans species being respectively in a high spin and a low spin configuration. These two isomers are fully characterized by electrochemistry and they are simultaneously observed in the reaction mixture by cyclic voltammetry. This study shows that the reactivity towards dioxygen of the two reduced isomers is different, and that the formation of the oxygenated species is not observed in some solvents.