Synthesis and structure of highly substituted pyrazole ligands and their complexes with platinum(II) and palladium(II) metal ions

Reaction of 3-methoxycarbonyl-2-methyl- or 3-dimethoxyphosphoryl-2-methyl-substituted 4-oxo-4H-chromones with N-methylhydrazine resulted in the formation of isomeric, highly substituted pyrazoles (major products) and (minor products). Intramolecular transesterification of and under basic conditions led, respectively, to tricyclic derivatives and . The structures of pyrazoles (dimethyl 2-methyl-4-oxo-4H-chromen-3-yl-phosphonate) and (methyl 4-oxo-2-methyl-4H-chromene-3-carboxylate) were confirmed by X-ray crystallography. Pyrazoles and were used as ligands (L) in the formation of ML2Cl2 complexes with platinum(II) or palladium(II) metal ions (M). Potassium tetrachloroplatinate(II), used as the metal ion reagent, gave both trans-[Pt()2Cl2] and cis-[Pt()2Cl2], complexes with ligand , and only cis-[Pt()2Cl2] isomer with ligand . Palladium complexes were obtained by the reaction of bis(benzonitrile)dichloropalladium(II) with the test ligands. trans-[Pd()2Cl2] and trans-[Pd()2Cl2] were the exclusive products of these reactions. The structures of all the complexes were confirmed by IR, 1H NMR and FAB MS spectral analysis, elemental analysis and Kurnakov tests.