Mercury(II) compounds with 1,3-imidazole-2-thione and its 1-methyl analogue. Preparative and NMR spectroscopic studies. The crystal structures of di-μ-iodo-bis[iodo(1,3-imidazolium-2-thiolato- S)mercury(II)], bis[bromo(1,3-imidazolium-2-thiolato- S)]mercury(II) and bis[μ-(1- N-methyl-1,3-imidazole-2-thiolato- S)]mercury(II)

Abstract

A series of mercury(II) compounds of the empirical formulae HgX 2L, and HgX 2L 2 (X=Cl −, Br −, I −, SCN −; L=imtH 2, meimtH; imtH 2=1,3-imidazole-2-thione, meimtH=1-methyl-1,3-imidazole-2-thione) has been obtained by the reaction of mercury(II) salts and 1,3-imidazole-2-thione and 1-methyl-1,3-imidazole-2-thione, respectively. Mercury(II) acetate yields HgL 2 complexes where L=imtH −, meimt −. The isolated compounds have been characterised by elemental chemical analysis, IR and 1H and 13C NMR spectroscopy. Complexation effects on chemical shifts in 1H and 13C spectra were shown to be a reliable probe for distinguishing HgX 2L and HgX 2L 2 complexes. In the former molecules the thione carbon (C-2) is shielded up to 3.0 ppm and the thioamide protons (NH) are deshielded up to 0.5 ppm, as compared to the corresponding atoms in the latter molecules. In all complexes the 13C complexation shift at C-2 decreases with decreasing electronegativity of the halogen atom (X), indicating the corresponding increase in π-character of the C-2–S bond. The crystal structures of HgI 2(imtH 2), HgBr 2(imtH 2) 2 and Hg(meimt) 2 have been determined by X-ray diffractometry and revealed S-bound imtH 2 in the iodo and bromo complex, while in Hg(meimt) 2 the ligand acts as bridging with stronger S and weaker N bonds.