SYNTHESES, THERMAL-BEHAVIOR, AND SPECTROSCOPIC AND X-RAY STUDIES OF QUINOLINIUM SALTS OF NICKEL(II), PALLADIUM(II) AND PLATINUM(II) 1,2-DITHIOOXALATO-S,S' COMPLEXES - PACKING AND BONDING OF THE QUINOLINIUM BIS(1,2-DITHIOOXALATO-S,S')NICKELATE(II)

Three quinolinium (HC9H7N = Hquin) salts of planar inorganic dithiooxa lato complexes: (Hquin)2[Ni(S2C2O2)2] (1). (Hquin)2[Pd(S2C2O2)2] (2) a nd (Hquin)2[Pt(S2 C2O2)2] (3) were synthesized and characterized by el emental analysis. IR and UV-vis spectroscopies, thermal analysis (TG, DTG and DTA) and X-ray diffraction techniques. Spectroscopic data supp ort the presence of the aromatic cation and the complex anion. The com plexes show a high thermal stability and the thermal studies give evid ence that the onset temperatures of their thermal decompositions, the corresponding reaction mechanism and the final solid products are stro ngly influenced by the atmospheric conditions. as well as the chemical and structural features of the starting compounds. X-ray diffraction analyses show that 2 and 3 are isomorphous with 1. which crystallizes in the monoclinic space group P2(1)/n with Z = 2 so that the anion str addles a crystallographic centre of symmetry. The crystal structure of 1 is built up by layers of quasi-planar [Ni(S2C2O2)2]2 complexes (A) and quinolinium cations (C) stacked along the c-axis, following an ... ACCACC... sequence. with alternative interplanar spacings of 3.3-3.8 a ngstrom (A...C) and 3.44 angstrom (C...C), which suggest the existence of significant pi-pi and d(z2)-pi interactions between the cations an d the complexes' anions. These interactions, together with the electro static forces and an extensive network of hydrogen contacts, ensure th e lattice cohesion and give the compound a three-dimensional character .