The kinetics of the anation reaction of aquopentaamminecobalt(III) by acetate in aqueous acidic solution

The anation reaction of aquopentaamminecobalt(III) by acetate has been studied in the temperature range 60–80°C and acidity range 1.0 ≦ pH ≦ 5.5 for total acetate concentrations ≦ 0.5 M and at ionic strength 1.0 M. The anation by acetic acid follows second-order kinetics (k₀), whereas the kinetic results for the anation by acetate (Q₁, k₁) provide evidence for the formation of an ion-pair with the complex ion. Typical experimental results at 70°C are k₀ = 5.33 X 10^?5 M^?1 sec^?1, Q₁ = 5.87 M^?1 and k₁ = 1.46 X 10^?4sec^?1. The activation parameters for the different reaction paths are reported and the results discussed with reference to various other anation reactions of Co(III) complexes.