Platinum(II) complexes of 2-, 3-, and 4-formyl-pyridine thiosemicarbazone and 2-, 3- and 4-acetyl-pyridine thiosemicarbazone Isolda C. Mendes, LetõÂcia R. Teixeira, Rejane Lima, TaÃnia G. Carneiro and Heloisa Beraldo* Departamento de QuõÂmica, Universidade Federal de Minas Gerais, 31270-901, Belo Horizonte, MG, Brazil Received 14 December 1998; accepted 22 February 1999 Abstract Seven platinum(II) complexes isolated from thiosemicarbazones derived from 2-, 3- and 4-formylpyridine and 2-, 3-, and 4-acetylpyridine have been characterised by microanalyses, molar conductivities and by their i.r. and 1 H-n.m.r. spectra. Introduction Thiosemicarbazones and their metal complexes are a class of compounds possessing a wide spectrum of biological applications [1]. The 2-heterocyclic thiosemi- carbazones have been the subject of extensive investiga- tions [2]; in some cases changing the point of attachment of the lateral chain to the 3- or 4-position on the heteroaromatic ring causes a decrease in activity [3], nevertheless the literature contains examples of biologi- cally important bidentate thiosemicarbazones. p-Acet- amidobenzaldehyde thiosemicarbazone, known as thiacetazone, is employed in the clinical treatment of tuberculosis [4, 5] and coordinates as a bidentate N±S ligand. Furthermore, the platinum(II) complexes of thiosemicarbazones have not been extensively studied. The present work deals with platinum(II) complexes of thiosemicarbazones derived from 2-, 3-, and 4-formyl- pyridine (H2FPT, H3FPT and H4FPT, respectively) and 2-, 3-, and 4-acetylpyridine (H2APT, H3APT and H4APT, respectively) (see Figure 1). Experimental The thiosemicarbazones were prepared by re¯uxing an EtOH solution of the desired aldehyde or ketone with thiosemicarbazide [6] (all starting materials were pur- chased from Aldrich). The [PtCl 2 (DMSO) 2 ] complex was prepared according to the literature [7]. Seven platinum(II) complexes were obtained: [Pt(2FPT)Cl] (1), [Pt(H2FPT) 2 Cl 2 ] (2), [Pt(H3FPT) 2 Cl 2 ] (3), [Pt(H4FPT) 2 Cl 2 ] (4), [Pt(2APT)Cl] (5), [Pt(H3APT) 2 ]Cl 2 (6), and [Pt(H4APT) 2 ]Cl 2 (7). Complexes (1) and (3)±(7) were obtained by the following method. An aqueous solution of K 2 PtCl 4 was added to the desired thiosemicarbazone dissolved in a solution of H 2 O/EtOH under re¯ux, with a 2:1 ligand-to-metal molar ratio. The mixture was cooled and then stirred for 4±5 h at room temperature. The resulting solids were ®ltered o, washed with H 2 O, then EtOH and Et 2 O, and dried in vacuo. Complex (2) was prepared by boiling an EtOH solution of [PtCl 2 (DMSO) 2 ] (1 mmol) and H2FPT (2 mmol) with stirring for 4±5 h. The solid which formed on cooling was ®ltered o, washed with EtOH, then Et 2 O, and dried at 35 °C. I.r. spectra were recorded on a Perkin Elmer 283B spectrometer using nujoll mulls between CsI plates; n.m.r. spectra were obtained with a Brucker DRX-400 Avance (400 MHz) spectrometer using d 6 -DMSO as the solvent and TMS as internal reference. Partial elemental Fig. 1. Structures of thiosemicarbazones derived from 2-, 3- and 4- formylpyridine and 2-, 3- and 4-acetylpyridine. * Author for correspondence Transition Metal Chemistry 24: 655±658, 1999. 655 Ó 1999 Kluwer Academic Publishers. Printed in the Netherlands.