The synthesis, structure and cytotoxic activity of Pt(ii), Pd(ii) and Cu(ii) complexes of the general formula MLCl2(M = Pt, Pd, Cu) 2–4and (CuLCl2)25where L is pyrazole-based chelate ligand 3-methyl-1-(2-pyridinyl)-1H-chromene[4,3-c]pyrazol-4-one 1are described. The complexes were characterized by elemental analysis, infrared and 1H NMR spectroscopy, as well as electrospray mass spectrometry. Compounds 3and 5were also studied using X-ray diffraction. In addition, geometries, partial atomic charges, and lipophilicity, which determines their ability to penetrate through cells membranes, were obtained computationally. Complexes 2–4exhibit square-planar geometries around the metal(ii) centers and adopt cisconfiguration. Complex 5is a dimer with distorted tetragonal pyramidal configuration at both Cu(ii) centers, which are connected by two μ2-chloro bridges in axial positions. The cytotoxic effect of these complexes was examined on HL-60 and NALM-6 human leukemia cells and melanoma WM-115 cells. The Pt-complex cis-2exhibited moderate cytotoxic activity against leukemic cells, but relatively high activity toward melanoma cells with cytotoxicity of IC50= 16.6 μM at a level comparable to that of cisplatin (18.2 μM). [ABSTRACT FROM AUTHOR]