Dimethyl sulfoxide containing platinum(II) and palladium(II) chelate complexes of glyoxylic and pyruvic acid thiosemicarbazones. A new class of cytotoxic metal complexes

The complexes [Pt(DMSO)(GT)] center dot DMSO (1), [Pt(DMSO)(PT)] center dot 1/2DMSO (2) and [Pd(DMSO)(PT)] (3), where DMSO = dimethyl sulfoxide, H(2)GT = glyoxylic acid thiosemicarbazone and H2PT = pyruvic acid thiosemicarbazone, have been synthesized and characterized by elemental analysis, molar electric conductivity, IR, electronic and NMR (H-1 and C-13) spectra. The single crystal X-ray diffraction analysis has revealed for 1 (orthorhombic, Pnma, a = 12.941(3), b = 7.108(2), c = 15.148(3) angstrom, Z = 4) that the doubly deprotonated thiosemicarbazone molecule is coordinated to Pt(H) via the carboxylato O, azomethine N and thiolato S atoms forming two condensed five-membered chelate rings. The fourth coordination site of Pt(II) is occupied by the S atom of DMSO. All the atoms of the complex molecule are coplanar except the methyl groups. The O atom of DMSO is in cis-position towards the thiolato-S atom (point group CS.). A system of hydrogen bonds of the type N-H center dot center dot center dot O links the complex molecules between them and with the lattice DMSO molecules. Similar structures have been deduced for the remaining two complexes on the basis of spectroscopic data. The three complexes and the ligand H(2)GT exhibit cytotoxic activity against F4N leukemia cells, whereas the ligand H2PT is inactive.