KINETICS OF PEROXODISULFATE OXIDATION OF BIS(MACROCYCLIC) DINICKEL(II) COMPLEXES - THE ROLE OF THE COORDINATION-NUMBER OF THE METAL-ION

Kinetics of peroxodisulfate oxidation of a number of homologous bis(ma crocyclic) dinickel(II) complexes in weakly acidic solutions (pH appro ximately 6) does not depend on ligand structure and resembles that of their 14-membered monomacrocyclic analogue. By contrast, parameters ob tained in 0.1 M H2SO4 show marked differences depending on the lengths of plymethylene chains connecting two monomacrocyclic subunits. Such behaviour is explained by the distinct reactivity of different forms o f complexes (i.e., four- or six-coordinated) prevailing in solution, w ith the square-planar form being more reactive. No evidence to suggest the complementary two-electron oxidation of dinickel(II) complexes by peroxodisulfate was obtained.