CATALYSIS OF IONIC REACTIONS BY POLYELECTROLYTES . REACTION OF CO(NH3)5CL2+ AND CO(NH3)5BR2+WITH HG2+ AN POLY(SULFONIC ACID) SOLUTION

The Hg2+-induced aquation of Co(NH3)5Cl2+ and Co(NH3)5Br2+ is powerfully catalyzed by poly(vinyl-sulfonate) (PVS) and poly(methacryloxyethylsulfonate) (PMES). In the absence of added electrolyte, the Co-(NH3)5C12+ reaction was accelerated by a factor of 176,000 by 5 × 10−5 N PVS and by a factor of 24,700 by a similar concentration of PMES. Increasing polymer concentration at constant Hg2+, or increasing Hg2+ concentrations at constant concentration of polyions, leads first to an increase and later to a sharp reduction of the reaction rate. These observations can be interpreted in terms of a model in which the catalytic efficiency of the polyion is characterized in terms of an effective concentration of binding sites in the polymer domain and dissociation constants of the polyion-reagent ion complexes. Dissociation constants calculated from the catalytic efficiency of the polyions are in good agreement with dialysis equilibrium of the reagent ions with PVS and PMES. The affinity of various inert cations for the polyanions may be estimated from their efficiency in reducing the catalytic power of the polyion. The activation energy of the Co(NH3)5Cl2+ reaction with Hg2+ is substantially reduced under conditions where only a small fraction of the reagent ions are bound to the polyion. © 1969, American Chemical Society. All rights reserved.