Transition metal complexes with pyrazole-based ligands. Part 28. Synthesis, structural, DFT and thermal studies of cadmium(II) halides and zinc(II) chloride complexes with 3,5-dimethylpyrazole-1-carboxamidine

The complex formation of 3,5-dimethylpyrazole-1-carboxamidinium nitrate, HL·HNO3 with ammine complexes of cadmium(II) halides (Cl, Br, I) and zinc(II) chloride has been investigated under self-controlled reaction conditions. The complexes have been characterized by X-ray diffraction, FT-IR spectroscopy, thermal analysis and quantum chemical calculations. In the case of cadmium bromide and iodide salts, isostructural complexes with composition of [CdX2(HL)2] were formed. With CdCl2 a binuclear octahedral [Cd2(HL)4(μ-Cl)2](NO3)2 complex is obtained. Zinc(II) chloride with HL·HNO3 gives [Zn(HL)2Cl]NO3, the zinc center exhibiting severely distorted five-coordinate stereochemistry, intermediate between an ideal trigonal bipyramid and a square pyramid. The course of complex formation as well as the thermal properties of the compounds has been explained using the HSAB principle. The assignment of the FT-IR spectra was supported by DFT computations.

Graphical abstractComplexes of CdX2 (X = Cl, Br, I) and ZnCl2 with the bidentate 3,5-dimethylpyrazole-1-carboxamidine (HL) ligand were synthesized and characterized. Single crystals were prepared from the corresponding metal ammine complexes and HL·HNO3 at a self-controlled rate. The complex formation and the thermal decomposition are explained using the HSAB principle. DFT calculations have been performed.Figure optionsDownload full-size imageDownload as PowerPoint slide