Transition metal complexes with pyrazole-based ligands. Part 8. Characterization and thermal decomposition of zinc(II) complexes with di- and trisubstituted pyrazoles

We report the synthesis and the characterization (elemental analysis, FT-IR spectroscopy, thermal methods and molar conductivity measurements) of the mixed complexes of zinc with acetate and 3-amino-5-methylpyrazole, HL1, [Zn (OAc)(2)(HL1)(2)], or 3-amino-5-phenylpyrazole, HL2, [Zn(OAc)(2)(HL2)(2)], or 4-acetyl-3-amino-5-methylpyrazole, HL3, [Zn(OAc)(L-3)(HL3)](2), with iso thiocyanate and HL2, [Zn(SCN)(2)(HL2)(2)], or HL3, [Zn(SCN)(2)(HL3)(2)], an d with nitrate, isothiocyanate and 3,5-dimethyl-1-carboxamidinepyrazole, HL 4, [Zn(NO3)(NCS)(HL4)(2)]. The thermal decomposition of the complexes is generally continuous resultin g zinc oxide as end product, except [Zn(OAc)(L-3)(HL3)](2), in which case a well-defined intermediate was observed between 570-620 K. On the basis of the IR spectra and elemental analysis data of the intermediate a decomposit ion scheme is proposed.