Thermal decomposition of Co(II), Ni(II) and Cu(II) complexes with formamidine derivative of pyrazole

Abstract

In this communication we discuss the thermal decomposition mechanism of octahedral complexes of cobalt(II), nickel(II) and copper(II) of coordination formulae [Co(ampf)(NO3)(MeOH)2]NO3 (1), [Ni(ampf)(NO3)(MeOH)2]NO3 (2), [Cu(ampf)(NO3)2(MeOH)]•MeOH (3) and squeare pyramidal complex of [Cu(ampf)Cl2] (4). The tridentate ONN ampf = N,N’-bis(4-acetyl-3-amino-5-methylpyrazole-3–yl)formamidine ligand formation takes place in situ, by the reaction of methanolic solutions of 4-acetyl-3-amino-5-methylpyrazole and the corresponding metal salt, in the presence of triethyl orthoformate. In spite of the fact that one MeOH in complex 3 belongs to the outer and the second to the inner coordination sphere while in the complexes 1 and 2 both MeOH molecules are in the inner coordination sphere, the mechanism of the solvent loss in the compounds 2 and 3 is almost identical while that of in complex 1 is significantly different. Before the solvent evaporation is completed, the decomposition proceeds with overlapping processes which cannot be evaluated without applying coupled methods. As compound 4 is not a solvent complex, its thermal decomposition mechanism significantly differs compared to the decomposition of the previous solvent complexes.