4-METHYLPYRIDINIUM SALTS OF PLANAR NICKEL(II), PALLADIUM(II) AND PLATINUM(II) 1,2-DITHIOOXALATO-S,S' COMPLEXES - PREPARATION, CHEMICAL CHARACTERIZATION AND THERMAL-BEHAVIOR

Three salts of planar inorganic dithiooxalato complexes. (HB)(2)[Ni(dto)(2)] (1), (HB)(2)[Pd(dto)(2)] (2) and (HB)(2)[Pt(dto)(2)] (3), where HB+ is 4-methylpyridinium and dto(2-) is the 1,2-dithiooxalato-S,S' ligand, were synthesized and characterized by elemental analysis, IR and UV-vis spectroscopies, thermal analysis (TG, DTG and DTA) and X-ray diffraction techniques. The IR and UV-vis spectra support the presence of the aromatic cation and the complex anions. The three compounds are isostructural and crystallize in the monoclinic space group P2(1)/n. Thermal studies give evidence that the mechanism and the final solid products are strongly influenced by the atmospheric conditions. The final decomposition products were identified by elemental analysis and the X-ray powder diffraction technique. In an argon-oxygen atmosphere, the final residues were a mixture of nickel sulphides oxides and sulphate for 1, metallic palladium and palladium(II) oxide for 2, and platinum(0) for 3. Thermal decompositions in the inert atmosphere yielded nickel(II) sulphide, a mixture of Pd/PdS and metallic platinum, respectively.