Zn(II) pyrazolonate complexes obtained by metal-induced cyclization of thiosemicarbazones: Crystal structures and spectroscopic properties

The reaction of zinc(II) acetate with thiosemicarbazones derived from β-keto esters (methyl propionylacetate thiosemicarbazone, ethyl benzoylacetate thiosemicarbazone, ethyl 2-ethylacetoacetate thiosemicarbazone and methyl acetoacetate 1N-ethylthiosemicarbazone) induces the cyclization of the thiosemicarbazone to afford [ZnL2] and (in one case) [ZnL2(MeOH)] complexes, where HL is a substituted 2,5-dihydro-5-oxo-1H-pyrazolone-1-carbothioamide. The four complexes were studied by X-ray diffraction, which showed that the pyrazolonate ligand binds with the metal through the S and N(3) atoms. The influence of cyclization and metallation on the 1H and 13C NMR spectra of the starting thiosemicarbazones is also discussed.

Graphical abstractThe reaction of zinc(II) with thiosemicarbazones derived from β-keto esters induces the cyclization of the thiosemicarbazone to afford [ZnL2] and [ZnL2(MeOH)] complexes, where HL is a pyrazolone ligand. The complexes were studied by X-ray diffraction, which showed that the pyrazolonate ligand binds with the metal through the S and N(3) atoms. The 1H and 13C NMR spectra of these complexes are also discussed.Figure optionsDownload full-size imageDownload as PowerPoint slide