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Mercury(II) Complexes with Heterocyclic Thiones- Preparation and Characterization of the 1:1 and 1:2 Mercury(II) Complexes with Benzo-1, 3-imidazole-2-thione

A series of complexes HgX2 (bzimtH_2 ) and HgX_2 (bzimtH2)_2 (X =Cl^- , Br^- , I^- , SCN^- ; bzimtH_2 = benzo-1, 3-imidazole-2-thione) was obtained by reaction of the mercury(II) salts with benzo-1, 3-imidazole-2-thione in the appropriate molar ratio(1:1 or 1:2). Hg(bzimtH)_2 was obtained by the deprotonation of bzimtH_2 with mercury(II) acetate (irrespective of the molar ratio of the reactants). The complexes were characterised by chemical and thermal analysis, IR, 1^H, and 13^C NMR spectroscopy, and some [HgX_2(bzimtH_2), X =I^- and HgX_2(bzimtH_2)_2 , X =I^- and SCN^-] by X-ray single crystal diffractometry. 1^H and 13^C NMR spectroscopic measurements in dimethyl sulphoxide revealed that the sulphur atom is coordinated to the mercury centre. The greatest complexation effects on the chemical shifts were observed for the thione carbon atom and thioamide proton. The crystal structures of HgI_2(bzimtH_2)_2 and Hg(SCN)_2 (bzimtH_2)_2 ˇC_2H_5OH consist of discrete monomeric molecules with halide or pseudohalide donor atoms and thione sulphur atoms tetrahedrally coordinated to the mercury atom. The structure of HgI2 (bzimtH2 )is polymeric with a trigonal bipyramidal 3 + 2 coordination geometry around the mercury atom. Polymerisation occurs through HgˇˇˇI interactions with neighbouring molecules. The distribution of the pi-electron density in bzimtH_2 corresponds to the thioketo tautomeric form in the solid state, and also in the DMSO solution of the complexes. Intermolecular hydrogen bonds of the type N-HˇˇˇN, N-HˇˇˇS and N-HˇˇˇI are observed.

Mercury; Sulphur heterocycles; Crystal structure; TGA-DTA analysis

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