Some Three-coordinate Complexes of Mercury(II)

Abstract

Abstract Nicotinic acid, nicotinamide and N-methylnicotinamide – pyridine derivatives with a carboxyl or amido group in the β-position in the ring – possess two potential donor sites, (i) pyridine ring nitrogen, and (ii) carbonyl oxygen in the case of nicotinamide and N-methylnicotinamide or carboxyl oxygen in nicotinic acid. As monodentate ligands bonding may occur through any one of these sites. One cannot rule out the possibility of the two coordination sites bonding to different metal ions (bidentate bridging ligand) resulting in polymeric structures. It should be possible to distinguish between the likely modes of metal–ligand bonding by i.r. spectroscopy. Except for the complexes of mercury(II) chloride and bromide with nicotinamide1 there is no report on those of mercury(II) halides and pseudohalides with these ligands. The present communication describes the coordination compounds formed by the interaction of mercury(II) chloride, bromide, cyanide and thiocyanate with nicotinic acid, nicotinamide and N-methylnicotinamide. The complexes isolated have been characterized by molecular conductance, molecular weight and infrared spectral measurements down to 200 cm−1 to elucidate the mode of metal–ligand bonding and the tentative stereochemistries of the complexes. Most of the complexes isolated have 1:1 stoichiometry (metal:ligand) and are considered to have monomeric, three-coordinated structures in the solid state.