Mono- and Polynuclear Hg(II) Complexes with Mixed Ligands: Nicotinamide and Oxalate, Nitrate, or Sulphate

Three new complexes of Hg(II), with the general formulas [Hg2(ox)2(NA)4]n·3nH2O (1), [Hg(NO3)2(NA)2(H2O)2]·2NA (2), and [Hg2(SO4)2(H2O)2(NA)4]·6H2O (3), where ox = oxalate and NA = nicotinamide, were synthesized and characterized by single crystal X-ray diffraction, elemental analysis, FT-IR, and fluorescence spectra. For complex (2), 13C and 1H NMR spectra were recorded. Thermogravimetric analysis was also performed for complexes (1) and (2). Single crystal X-ray diffraction shows that in the polymeric complex (1) and the binuclear complex (3), the Hg(II) ions are hexacoordinated, whereas in the mononuclear complex (2), Hg(II) is octacoordinated. In complex (1), each oxalate group acts in a µ4 coordination manner, the basal plan being made up by four oxygen atoms belonging to the two oxalate ligands, while the nicotinamide molecules occupy the axial positions. In complex (2), the nitrate groups coordinate in a bidentate chelating mode, whereas in complex (3), each sulphate ligand acts in a bidentate chelating–bis monodentate bridging manner.