Reactions of Cadmium(II) Acetate with Acetoacetanilide and Methylacetoacetate Thiosemicarbazones: A Cyclization Process Leading to a Pyrazolone – The Molecular and Crystal Structures of the Free Ligands and the Complex [CdL2Py] (HL = 2-[Amino(thioxo)methyl]-5-methyl-2,3-dihydro-1H-3-pyrazolone, Py = Pyridine)

Abstract

Acetoacetanilide- and methylacetoacetate thiosemicarbazones (HTSC1 and HTSC2, respectively) react with cadmium(II) acetate in methanol, giving complexes containing the ligand 2-[amino(thioxo)methyl]-5-methyl-2,3-dihydro-1H-3-pyrazolonate (L–). An X-ray diffraction study of the structures of HTSC1, HTSC2, HL, and [CdL2Py], identified the main structural changes in the cyclization process. Additionally, the coordination of the metal in the complexes [CdL(AcO)] · 2 MeOH and [CdL2] · 3 H2O was analyzed using IR spectroscopy in the solid state and 1H-, 13C-, and 113Cd-NMR spectroscopy in solution. On reaction with aqueous trifluoroacetic acid, both complexes releases the free pyrazolone, which can be easily isolated.