Syntheses, thermal behaviour, 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)

Abstract

Three quinolinium (HC 9H 7N = Hquin) salts of planar inorganic dithiooxalato complexes: (Hquin) 2[Ni(S 2C 2O 2) 2] ( 1, (Hquin) 2[Pd(S 2C 2O 2) 2] ( 2) and (Hquin) 2[Pt(S 2C 2O 2) 2] ( 3) were synthesized and characterized by elemental analysis, IR and UV-vis spectroscopies, thermal analysis (TG, DTG and DTA) and X-ray diffraction techniques. Spectroscopic data support the presence of the aromatic cation and the complex anion. The complexes show a high thermal stability and the thermal studies give evidence that the onset temperatures of their thermal decompositions, the corresponding reaction mechanism and the final solid products are strongly 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 straddles a crystallographic centre of symmetry. The crystal structure of 1 is built up by layers of quasi-planar [Ni(S 2C 2O 2) 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 Å (A ⋯ C) and 3.44 Å (C ⋯ C), which suggest the existence of significant π-π and d z 2 -π interactions between the cations and the complexes' anions. These interactions, together with the electrostatic forces and an extensive network of hydrogen contacts, ensure the lattice cohesion and give the compound a three-dimensional character.