Spectral Characteristics and Kinetic Features of Redox Reactions of Nickel(II) And Nickel(III) Complexes with Dioxotetraaza Macrocyclic Ligands

Abstract

Abstract Spectral characteristics of nickel(II) and nickel(III) complexes with unsubstituted and benzyl-substituted 13- and 14-membered dioxotetraaza macrocyclic ligands have been studied. The interaction of nickel(II) complexes with peroxodisulfate was shown to yield two different products depending on the ring size of the macrocycle: [Ni(III)L]' in case of 14-membered ligands and NiL-2H, i.e. nickel(II) complexes with the oxidized macrocycle, in case of 13-membered ligands. The [Ni(III)L]+ complexes decompose in neutral solutions via an intramolecular redox reaction to yield Ni(II)L-2H compounds. The presence of a new C˭N bond in the products of redox reaction was established by means of electronic spectroscopy and 1H and 13C NMR data. Rate constants and activation parameters for oxidation of Ni(II)L by peroxodisulfate and decomposition reactions of [Ni(III)L]+ in aqueous solution at pH 5.7 have also been measured. The influence of ligand structure on the kinetic parameters of redox reactions studied was investigated. Comparison of data obtained with the results of the study of redox reactions of similar copper complexes has been made and possible reaction mechanisms discussed.