title: Reactions of thiosemicarbazones derived from beta-keto amides and beta-keto esters with Zn(II) and Cd(II) acetates: influence of metal, substitution, reagent ratio and temperature on metal-induced cyclization.
abstract: Zinc(II) and cadmium(II) acetates were reacted in methanol under various experimental conditions with thiosemicarbazones derived from beta-keto amides or beta-keto esters (HTSC). Some of these reactions afforded thiosemicarbazonate complexes [M(TSC)2] with IR and NMR spectra compatible with N,S-coordination, but most gave complexes [ML2], where HL is a substituted 2,5-dihydro-5-oxo-1H-pyrazole-1-carbothioamide resulting from cyclization of the HTSC. Some of these pyrazolonates and two of the HL ligands were studied by X-ray diffractometry, and their structures are discussed. Surprisingly, the reactions of zinc(II) acetate with HTSC in 1:1 mol ratio usually gave a third, previously unreported type of complex with a dideprotonated ligand, [Zn(L-H)], which was also formed when [ZnL2] and Zn(OAc)2 interacted at room temperature in 1:1 mol ratio. These L-H complexes are highly insoluble in all common solvents, which hinders their characterization but suggests that they are polymeric in nature.
authors.affiliation: Departamento de Química Inorgánica, Facultade de Farmacia, Universidade de Santiago de Compostela, 15782, Galicia, Spain.
authors.forename: José S
authors.initials: JS
authors.lastname: Casas
authors.forename: María V
authors.initials: MV
authors.lastname: Castaño
authors.forename: María S
authors.initials: MS
authors.lastname: García-Tasende
authors.forename: Enrique
authors.initials: E
authors.lastname: Rodríguez-Castellón
authors.forename: Agustín
authors.initials: A
authors.lastname: Sánchez
authors.forename: Luisa M
authors.initials: LM
authors.lastname: Sanjuán
authors.forename: José
authors.initials: J
authors.lastname: Sordo