Preparation and characterization of µ-amido-µ-acetato and µ-amido-µ-formato binuclear ammine complexes of cobalt(III) and related kinetic studies

Abstract

Chloride and Perchlorate salts of µ-amido-µ-acetao-bis[tetra-amminecobalt(III)](I) and µ-amido-µ-formato-bis[tetra-amminecobalt(III)](II) have been prepared from the µ-amido-µ-chloro-bis[tetra-amminecobalt(III)] [graphic omitted] complex. Evidence consistent with the structures indicated in (I) and (II) is considered. A kinetic study has been made of the reaction of the µ-amido-µ-hydroxo-bis[tetra-amminecobalt(III)] complex with acetic acid in perchloric acid solutions, I= 2·0M(LiClO₄). Over the temperature range 25–40°C and at hydrogen-ion concentrations 0·1–1·5M, the rate law is as in (i). Activation parameters have been determined and, at 25 °C, –d In [(Co^III)₂]/dt=(k₁+k₂[H⁺])[CH₃CO₂H](i)k₁=(1·4 ± 0·1)× 10^–6 l mol^–1 s^–1 and k₂=(6·5 ± 0·1)× 10^–6 l² mol^–2 s^–1. The reverse reaction, the decomposition of the µ-amido-µ-acetato-complex, has been investigated briefly at 50°C and the rate law is of the form (ii). –d In [(Co^III)₂]/dt=a+b[H⁺](ii)