New Pd(II) and Pt(II) complexes with N,S-chelated pyrazolonate ligands: Molecular and supramolecular structure and preliminary study of their in vitro antitumoral activity

New Pd(II) and Pt(II) complexes [ML 2] (HL = a substituted 2,5-dihydro-5-oxo-1 H-pyrazolone-1-carbothioamide) have been synthesized by reacting K 2MCl 4 (M = Pd, Pt) or Pd(OAc) 2 with β-ketoester thiosemicarbazones. The structures of seven of these complexes were determined by X-ray diffraction. Although all exhibit a distorted square-planar coordination with trans- or (in one case) cis-[MN 2S 2] kernels, their supramolecular arrangements vary widely from isolated molecules to 3D-networks. The in vitro antitumoral assays performed with two HL ligands and their metal complexes showed significant cytostatic activity for the latter, with the most active [ML 2] derivative (a palladium complex) being about sixteen times more active than cis-DDP against the cisplatinum-resistant cell line A2780cisR.