Synthesis, characterization, in vitro cytotoxicity and anti-inflammatory activity of palladium(II) complexes with tertiary phosphines and heterocyclic thiolates: Crystal structure of [PdC28H19N8PS2]

The new four-coordinated mononuclear palladium(II) complexes 1-9 with chelating heterocyclic thiolates and tertiary phosphines with general formula Pd(L)_nCl(R′R₂P)] (L = Pym2SH (pyrimidine-2-thiolate), Pur6SH (purine-6-thiolate), Py2SH (pyridine-2-thiolate), R₃P = PPh₃, P(o-tolyl)₃, PPh₂Cl), n = 1, 2) have been synthesized by the direct reaction of PdCl₂(R′R₂P)₂] with polyfunctional heterocyclic thiolates which display a wide variety of coordinations. These compounds were characterized by elemental analysis, FT-IR and multinuclear (¹H, ¹³C and ³¹P) NMR. The X-ray diffraction study of non-ionic compound 5 showed that the thiolate acts as unidentate and that the chelating (-N,S) ligand adopts a slightly distorted square planar geometry around the palladium atom. In vitro the anti-inflammatory inhibition of compounds 1-9 was 10-15% greater than that of the standard drug Declofenac. Compounds 1 and 4 showed mostly a moderate to low cytotoxicity against seven human tumor cell lines whereas compound 3 was somewhat more active.