The solid state and solution chemistry of selected 3d-transition metal chloride complexes

Abstract

Comparisons were given for the decomposition reactions of several metal complexes containing ligands related to pyridine. The ligands pyridine, quinoline, aniline, a-, b-, r-picoline were studied. The metal complexes included the first-row transition metal complexes, with special reference to cobalt, nickel and manganese. The effects of the electron-releasing substituents on the kinetic data as well as on the metal-ligand bond was reported. These substituents increased the electron density 1n the ring and strengthened the q-bond and weakened the ~-bond. Kinetic models were assigned to the different decomposition reactions. Comparative kinetic data were reported for the analysis of isothermal and dynamic TG curves. It was found that if separate reactions occur the kinetic results of the dynamic TG curve represent the experimental TG curve the best. In addition, the electron microscopy studies supported the assigning of the kinetic models. The enthalpies of formation and the decomposition temperature at peak maximum, obtained from the DSC studies, indicated the strength of the various metal-ligand bonds. The strength of the cobalt (II)-ligand bonds in solution was also studied and if possible, compared to the solid-state chemistry. The strengths of different metal-ligand bonds were investigated by applying various thermogravimetric and physical techniques.