On the mechanism of reduction of maleate by a Co(I) complex with a macrocylic ligand in aqueous solutions

Recently, it was shown that a Ni(I) complex with a tetraazamacrocyclic ligand (Ni^I(1, 4, 8, 11-tetraazacyclotetradecane)⁺, Ni(I)L⁺₂, cyclam), reduces maleate in aqueous solutions. It was decided to investigate whether this is a general reaction of low valent transition metal complexes. In this study, the reactions of Co^IL ⁺ (L = 5, 7, 7, 12, 14, 14-hexamethyl-1, 4, 8, 11- tetraazacyclotetradeca-4, 11-diene) with maleate were investigated. The effect of the addition of maleate to aqueous solutions containing this low valent metal complex, prepared via the pulse radiolysis technique, was studied. The d →* complexes formed between the monovalent cobalt complex and maleate were detected and characterized by UV-Vis spectroscopy. The nature of the final products formed was studied and detailed mechanisms of the reduction processes are proposed. The mechanism and kinetics of the reaction of Co(I)L⁺ with maleate was studied applying pulse-radiolysis and analysis of the final products.