Non-isothermal decomposition kinetics of complex of Co(III), Ni(II) with O,O '-dialkyldithiophosphates and adducts of Ni-complex with pyridines

Thermal behaviour of tri(O,O'-diisopropyldithiophosphate)cobalt(III) Co(dpt p)(3), and bis (O,O'-diethyldithiophosphate)nickel(II), Ni(detp)(2) and its adducts with pyridine, Ni(detp)(2)(py)(2) or 4-methylpyridine, Ni(detp)(mp y)(2) in a dynamic nitrogen atmosphere was investigated by TG-DTG and DSC t echniques, which showed a medium endothermic peak for the evolution process of pyridine(or 4-methylpyridine) and a strong exothermic peak for that of O,O'-diethyldithiophosphate. The thermal stability and decomposition patter ns for these compounds were compared and interpreted in terms of structural features such as bond character and steric effects. The kinetic parameters and mechanisms of every decomposition stage involved for all these complex es were obtained employing the non-isothermal kinetic analysis method sugge sted by Malek et al., which showed the kinetics mechanism for pyrolysis of pyridine(or 4-methylpyridine) is an S-B empirical model with lower activati on energy, while that of O,O'-dialkyldithiophosphate is a diffusion model. These results are in accord with the fact that two ligands are of different type.