Synthesis, Spectral and Thermal Characterization of Bis(pyridine-3- carboxy-2-thiolato-S)mercury(II). Crystal Structure of Dibromobis(3- metoxycarbonylpyridine-2-thiolato-S)mercury(II)

2-mercaptonicotinic acid (H2mna = 2-HS(C^sub 5^H^sub 3^N)COOH) gave a thiolato compound of the formula Hg(Hmna)^sub 2^ by a reaction with various mercury(II) salts, HgX^sub 2^ (X = Cl^sup -^, Br^sup -^, I^sup -^, SCN^sup -^) in an ethanol or methanol solution irrespectively of the molar ratio of the reactants (1:1 or 1:2). The same compound was obtained from the reaction of mercury(II) acetate in an aqueous-ethanol solution. Hg(Hmna)^sub 2^ was characterized by vibrational spectroscopy and thermal analysis. ^sup 1^H and ^sup 13^C NMR measurements provided additional information on the thiol-thione tautomerism in H2mna and Hg(Hmna)^sub 2^ and also on the binding mode to mercury in the DMSO-d^sub 6^ solution. HgBr^sub 2^(CH^sub 3^-Hmna)^sub 2^ was obtained from the reaction of H^sub 2^mna with HgBr^sub 2^ in methanol after filtering offthe main product Hg(Hmna)^sub 2^ (CH^sub 3^-Hmna = 2- HS(C^sub 5^H^sub 3^N)COOCH^sub 3^). The crystal structures of H^sub 2^mna and HgBr^sub 2^(CH^sub 3^-Hmna)^sub 2^ were determined by the X-ray structure analysis. 2-mercaptonicotinic acid exists in the crystalline state in the thione tautomeric form. Two bromine atoms and two S-bound CH^sub 3^-Hmna ligands form a tetrahedral coordination sphere around the mercury atom in HgBr^sub 2^(CH^sub 3^-Hmna)^sub 2^. [PUBLICATION ABSTRACT]