The kinetics of the reduction of the µ-amido-µ-superoxo-complexes (bipy)2Co·µ(NH2, O2)·Co(bipy)24+ and (phen)2Co·µ(NH2, O2)·Co(phen)24+ with Fe2+ and related studies

Abstract

The 1:1 Fe²⁺ reductions of the µ-amido-µ-superoxo-complexes (bipy)₂Co·µ(NH₂, O₂)·Co(bipy)₂⁴⁺ and (phen)₂Co·µ(NH₂, O₂)·Co(phen)₂⁴⁺(bipy = 2,2′-bipyridyl and phen = 1,10 phenanthroline), have been studied µ= 0·25M(LiNO₃–HNO₃). The reactions are first order in Fe²⁺ and in complex and independent of [H⁺] over the range 0·05 to 0·20M. At 25°k= 9·63 (±0·26)× 10³ l mol^–1 s^–1, ΔH^‡= 2·67 ± 0·25 kcal mol^–1 and ΔS^‡=–31·4 ± 0·9 e.u. for the bipyridyl complex, and k= 1·41 (±0·05)× 10⁴ l mol^–1 s^–1, ΔH^‡= 2·21 ± 0·18 kcal mol^–1 and ΔS^‡=–32·2 ± 0·6 e.u. for the phenanthroline complex. Protonated forms of the µ-amido-µ-peroxo-products have been identified.