KINETIC-STUDIES ON THE THERMAL DEHYDRATION OF 4-AMINOPYRIDINIUM (1,2-DITHIOOXALATO-S,S')METALATE(II) DIHYDRATE COMPLEXES (M=NI,PD AND PT)

The thermal dehydration processes of 4-aminopyridinium (1,2-dithiooxal ato-S,S')metalate (II) dihydrate (M = Ni, Pd and Pt) have been studied under inert (Ar) and oxidative (Ar + O-2) atmospheres by thermogravim etric (TG,DTG and DTA) and DSC techniques and using non-isothermal con ditions. The kinetic analysis of the dehydration curves has been perfo rmed applying 21 different rate law expressions for theoretical solid- state models (nucleation, growth, nucleation-growth and diffusion); In both atmospheres, the best fits correspond to random nucleation rate laws. The activation energies obtained are 89.6 kJ mol(-1) for the Ni compound, 94.1 kJ mol(-1) for the Pd compound and 85.1 kJ mol(-1) for the Pt compound in the oxidative atmosphere. In the inert atmosphere, the activation energy values are 101.5, 101.5 and 96.1 kJ mol(-1) for the Ni, Pd and Pt compounds, respectively. These values are in accord with the fact that the three compounds are isostructural. The DSC curv es show sharp endothermic peaks for the dehydration processes of the t hree compounds in both atmospheres and the dehydration enthalpies were computed from them.