A study of some reactions of acetylacetonatobis(ethylenediamine)cobalt(III) ion in sodium hydroxide solution

The reactions of acetylacetonato cobalt (III) ion in sodium hydroxide solutions have been studied spectrophotometrically over a range of temperatures and hydroxide ion concentrations. The activation enthalpy, ΔH^≠ was 70.6 kJ mol^?1 and the activation entropy, ΔS^≠ was ? 119 JK^?1mol^?1, with a rate law of k_obs = k₂ OH^?]². A mechanism involving initial de-chelation of the acetylacetone ligand is suggested. The rate of exchange of methyl hydrogen of the acetylacetone ligand was studied, using proton nuclear magnetic resonance. The rate law was k_obs = k OH^?]. Initial de-chelation is also suggested as a mechanism for this process. The ¹³C nuclear magnetic resonance spectrum of the complex is reported.