Syntheses and chemical, spectroscopic and structural study of 4-aminopyridinium salts of dithiooxalate ligand complexes, [M(S 2C 2O 2) 2] 2− (M = Ni II, Pd II or Pt II)

Abstract

The synthesis conditions, the solid state characterization and the crystal structures of three 4-aminopyridinium salts of planar inorganic dithiooxalato anions, (C 5H 7N 2) 2[M(S 2C 2O 2) 2].2H 2O where M = Ni(II), Pd(II) and Pt(II) (hereafter abbreviated as NIDT4AP, PDDT4AP, and PTDT4AP, respectively), are described. The compounds have been prepared by reaction of 4-aminopyridinium hydrochloride and the corresponding K 2[M(S 2C 2O 2) 2] in aqueous solution, and then recrystallized in N,N-dimethylformamide. The compounds have been identified by using IR, thermoanalytical, and X-ray diffraction techniques. X-ray diffraction analyses of these compounds show that all of them are isostructural and crystallize in monoclinic system, space group C2/m, Z = 2. The crystal and molecular structure of compound PDDT4AP was determined: a = 10.462(1), b = 12.020(4), c = 9.207(1) A ̊ , β = 114.44(5)°, V = 1054.1(6) A ̊ 3 , Z = 2, F(000) = 576, μ = 12.866 cm −1, M = 572.98, D o = 1.80(1), D x = 1.81 Mg· m −3, and λ( MoKα) = 0.71069 A ̊ . Final refinement led to R = 0.025 and wR = 0.030 for 1542 observed reflections with I > 3 σ(I). The unit cell is made up of bis(dithiooxalato)palladate(II) anions and 4-aminopyridinium cations forming layers, and the water molecules occupy the space among them. In the crystal structure there are some significant π-π interactions between the aromatic cations and also d z2-π interactions between the metal ion of the complex anion and the planar cations. There is also an extensive hydrogen bond network. All these types of interactions ensure the lattice cohesiveness and give to the compound a tridimensional character.