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

• Published in: Polyhedron Vol. 24; no. 18; pp. 3057 - 3065
• Main Authors: Casas, J.S., Castaño, M.V., García-Tasende, M.S., Sánchez, A., Sordo, J., Touceda, A.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 08-12-2005
• Subjects: 1H and 13C NMR; 5-Pyrazolones; Metal-induced cyclization; Thiosemicarbazones; X-ray crystallography; Zn(II) complexes; X-ray crystallography; 5-Pyrazolones; Zn(II) complexes; 1H and 13C NMR; Metal-induced cyclization; Thiosemicarbazones
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2005.06.040

The reaction of zinc(II) with thiosemicarbazones derived from β-keto esters induces the cyclization of the thiosemicarbazone to afford [ZnL
2] and [ZnL
2(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.
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
1
N-ethylthiosemicarbazone) induces the cyclization of the thiosemicarbazone to afford [ZnL
2] and (in one case) [ZnL
2(MeOH)] complexes, where HL is a substituted 2,5-dihydro-5-oxo-1
H-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.