Effect of the polymer backbone on the ligand substitution reaction of a macromolecule–metal complex. Acid and base hydrolyses of the polymer-bound cobalt(III) complexes

Abstract

The kinetics of the acid and base hydrolyses of polymer-bound Co^III complexes, cis-[Co(en)₂LCl]²⁺, where L = poly(4-vinylpyridine)(PVP) or partially quaternized PVP (QPVP), have been investigated in aqueous solutions. The rate of the base hydrolysis of the PVP complex was found to be dependent on the degree of polymerization of the polymeric ligand and on the nature and concentration of the dissolved inert salt. The rate constants of the base hydrolyses of the polymer complexes are greater than that of the low-molecular-weight model complex by a factor of ca. 2–3, whereas those of the acid hydrolyses of the PVP complex are smaller than in the low-molecular-weight case by ca. 3. The effect of the polymer backbone on the rates of acid and base hydrolyses of the macromolecule–metal complexes is discussed in terms of the effect of the microenvironment of the polymer domain and the kinetic parameters.