Thermodynamics of solvent extraction processes: Synergic adducts of copper and zinc diketonates with bidentate nitrogen bases

Abstract

By direct titration calorimetry, the equilibrium constants and the enthalpy, entropy and free energy changes of the reaction MA 2 + L → MA 2L, leading to the formation of synergic adducts of 1,10-phenanthroline, 2,2′-dipyridyl and 4,4′-dipyridyl with several bis-(β-diketonato) copper and zinc chelates have been determined in chloroform solution at 25°C. The thermodynamic functions indicate that the lower the stability of the metal diketonate and the greater basicity of the donor atom, the greater the stability of the adduct formed. In most cases the adducts are stalilized by large exothermic enthalpy changes. In some copper compounds, however, the Jahn-Teller distortion affects the enthalpy and entropy contributions to the free energy changes.