Catalysis by polyelectrolytes of the Ag+, Hg2+, and Tl3+ induced aquations of Co(NH3)5Br2+

Abstract

The aquation reaction of Co(NH₃)₅Br²⁺ was studied kinetically with Ag⁺, Hg²⁺ and Tl³⁺ as inducing cations. Addition of polyethylene sulphonate, polystyrene sulphonate and polyphosphate markedly enhanced the reaction. The acceleration factor, ranging from 10 to 10⁴, was dependent on the inducing cations, polyelectrolytes, their concentrations and the concentrations of foreign salts. The enthalpy of activation (ΔH^{[graphic omitted]}) and the entropy of activation (ΔS^{[graphic omitted]}) were decreased by addition of polyelectrolytes in the case of Ag⁺ and Hg²⁺, as has been observed previously, whereas ΔH^{[graphic omitted]} was not influenced and ΔS^{[graphic omitted]} increased in the case of Tl³⁺. The behaviour of Tl³⁺ was ascribed to the strong hydration of this cation.