Palladium(II) and platinum(II) complexes of pyridine-2-carbaldehyde thiosemicarbazone with potential biological activity. Synthesis, structure and spectral properties. Extended network via hydrogen bond linkages of [Pd(PyTsc)Cl]

The reactions of Li2PdCl4 and Na2PtCl4 with pyridine-2-carbaldehyde thiosemicarbazone, HPyTsc, afforded the complexes [Pd(PyTsc)Cl], [Pd(PyTsc)(2)] and [Pt(PyTsc)Cl], [Pt(PyTsc)(2)]. The new complexes have been characterized by elemental analyses and spectroscopic studies. A crystal structure of [Pd(PyTsc)Cl] shows that the anion of PyTsc coordinates in a planar conformation to the central palladium(II) through the pyridyl N, azomethine N and thiolato S atoms. The planar molecules are linked into polymeric chains by N-(HN)-N-.. and N-(HS)-S-.. hydrogen bonding. The protonation constants of the ligand. K-a1 and K-a2, were determined by spectrophotometry and the logarithms of their values were found to be equal to 11.58+/-0.05 and 3.94+/-0.02 respectively. Correlation of the antitumor activity of these complexes to the structure and to reduction potential is reported. The compounds [Pt(PyTsc)(2)] and [Pd(PyTsc)(2)] were found to exhibit the higher in vivo antitumor activity and the lower cytotoxicity. (C) 1999 Elsevier Science Ltd. All rights reserved.