C. Comuzzi, A. Melchior, P. Polese
Aug 1, 2002
Citations
1
Influential Citations
26
Citations
Journal
European Journal of Inorganic Chemistry
Abstract
The formation of CoII complexes with differently methylated N-donor ligands ethylenediamine (en), N,N′-dimethylethylenediamine (dmen), N,N,N′-trimethylethylenediamine (trmen), and N,N,N′,N′-tetramethylethylenediamine (tmen), has been studied at 298 K in both the aprotic solvent dimethyl sulfoxide (dmso) and in an ionic medium set to 0.1 mol dm−3 with Et4NClO4 under anaerobic conditions. UV/Vis spectrophotometric and calorimetric measurements were carried out to obtain the thermodynamic parameters for the systems investigated. Only mononuclear CoLj2+ complexes were formed (j = 1−3 for en, j = 1, 2 for dmen; and j = 1 for trmen and tmen) where the diamines act as bidentate agents. All the complexes are enthalpy-stabilized whereas the entropy changes counteract the complex formation. The results are discussed in terms of different basicities and steric requirements both of the ligands and the complexes formed. Voltammetric measurements were carried out to correlate the electrochemical properties of the anaerobic complexes with their different dioxygen affinities. The X-ray structure of the starting adduct [Co(dmso)6][ClO4]2, determined on a monocrystal, is also reported. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)