The kinetics of the decomposition of amido- and superoxo-bridged binuclear complexes of cobalt
Abstract
The kinetics of the decomposition of the single-bridged decammine µ-amido- and µ-superoxo-dicobalt complexes (NH3)5Co·NH2·Co(NH3)55+ [graphic omitted] Co(NH3)63++ Co(NH3)5H2O3+, and (NH3)5Co·O2·Co(NH3)55+ [graphic omitted] Co(NH3)5H2O3++ Co2++ 5NH4++ O2, have been studied in aqueous perchloric acid, µ= 2·0M, in the range 47·3–80°. Both reactions are first-order in complex and independent of hydrogen-ion concentration in the range 0·02–2·0M. At 64·6°k1= 13·5 × 10–5 sec.–1 and k2= 6·65 × 10–5 sec.–1; the activation parameters are ΔH1‡= 31·5 ± 1·2 kcal. mole–1, ΔS1‡= 5·6 ± 3 e.u., ΔH2‡= 28·1 ± 1·2 kcal, mole–1, and ΔS2‡= 17 ± 3·5 e.u. respectively.
In the decomposition of the double-bridged complex (NH3)4Co·µ(NH2,O2)·Co(NH3)44+ at 85° and µ= 2·0M, the rate constant for the disappearance of complex is ca. 4·1 × 10–5 sec.–1. Evidence for the formation of a single-bridged intermediate is considered.