Synthesis, structure, protolytic properties, alkylating and cytotoxic activity of novel platinum(II) and palladium(II) complexes with pyrazole-derived ligands

Article abstract of DOI:10.1002/ejic.200700139

Novel platinum(II) and palladium(II) complexes [PtCl₂(HL ¹)] (3a), [NH₂CH₃)₂][PtCl ₂(L¹)] (3b), [PdCl₂(HL¹)] (4a), [NH₂(CH₃)₂][PdCl₂(L¹)] (4b) and [PdCl(CH₃CN)(L¹)] (4c), where HL¹ = 4-(2-hydroxybenzoyl)-2-(pyridin-2-yl)-1H-pyrazol-3-ol, have been synthesised as potential anticancer compounds. Protonation constants of the ligand were determined by pH-metric titration (log K₁ = 7.74 ± 0.03; log K₂ = 2.85 ± 0.05). The solid-state structures of complexes 3b and 4c have been determined by X-ray diffraction, showing sguare-planar coordination geometry of Pt^II and Pd^II ions. In addition, the compounds have been characterised by IR, ¹H NMR and FAB mass spectrometry. The results of preliminary studies on the cytotoxic activity in vitro against HL-60 and NALM-6 leukaemia cell lines are also reported and the IC₅₀ values compared with those of the metal-free ligand and cisplatin. Cytotoxic evaluation revealed that Pt^II and Pd ^II complexes were active in the micromolar concentration range. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.