Comparison between the inter- and intra-molecular kinetics of reduction of penta-ammine(ligand)cobalt(III) complexes by the para-nitrobenzoate radical: a pulse-radiolytic study

Abstract

Second-order rate constants for reduction by the p-nitrobenzoate radical of the complexes [Co^III(NH₃)₅X][X = NH₃. PhCO₂^–, p-O₂NC₆H₄CO₂^–, Br^–, pyridine (py), and m-H₂NCOC₅H₄N] have been measured and are in the range 10⁵–10⁷ I mol^–1 s^–1. The rates of the first three reactions are considerably faster than those expected from the intramolecular rate of electron transfer in [Co^III(NH₃)₅(O₂CC₆H₄NO₂^–p)]⁺ and suggest poor ‘electron permeability’ of the carboxylate group.