Thermal study of nickel(II) pyrazolyl complexes

The thermal behavior of the pyrazolyl complexes [NiCl2(HPz)(4)] (1), [Ni(NCS)(2)(HPz)(4)] (2), [NiCl2(HdmPz)(4)](.)2H(2)O (3) and [Ni(NCS)(2)(HdmPz)(4)](.)2H(2)O (4) (HPz = pyrazole, HdmPz = 3,5-dimethylpyrazole) has been studied by thermogravimetry (TG) and differential thermal analysis (DTA). The TG data indicated that the thermal stability of [NiX2(HL)(4)] (X = Cl, NCS) compounds varies depending on the pyrazolyl ligand in the following order HL = HPz > HdmPz. From the thermal decomposition of 3 and 4 it was possible to isolate the intermediate compounds [Ni(mu-Cl)(2)(HdmPz)(2)] (3a) and [Ni(mu-1,3-NCS)(2)(HdmPz)(2)] (4a), respectively. The final products of the thermal decompositions of 1-4 were identified as NiO by X-ray powder diffraction.