Complexes of heterocyclic thiones and Group 12 metals: Part 2: The chemical and electrochemical synthesis of mercury(II) complexes of 1-methylimidazoline-2(3H)-thionate. The crystal structure of trans-[bis-{(η1-S-1-methylimidazoline-2(3H)-thione)(η1-S-1-m

Two complexes of mercury(II) and the anion of 1-methylimidazoline-2(3H)-thione (1-meimz2SH) have been prepared and characterised. The addition of an aqueous solution of mercury(II) acetate to an aqueous solution of 1-methylimidazoline-2(3H)-thione and triethylamine produced [Hg(1-meimz2S)2], as a colourless and intractable precipitate. The electrochemical oxidation of elemental mercury, in the presence of a saturated acetonitrile solution of 1-methylimidazoline-2(3H)-thione and a supporting electrolyte, produced two crystalline products, a pale-yellow microcrystalline complex, [Hg(1-meimz2S)2] and a colourless crystalline complex, [Hg(1-meimz2S)2(1-meimz2SH)]. An X-ray crystal structure analysis of [Hg(1-meimz2S)2(1-meimz2SH)] showed that the complex consists of discrete, centrosymmetrically constrained, mercury(II) dimers. Each dimer contains a pair of bifunctional, binuclear bridging, μ2-S,N(η1-S;η1-N), 1-methylimidazoline-2(3H)-thionate anionic ligands (HgSbridging=2.5196(6), HgN=2.325(2) Å, NCSexo=126.0(2)°). The bridging ligands adopt a ‘head-to-tail’ configuration. This arrangement generates a central eight-membered ring, Hg2S2C2N2, in the complex. The ring adopts a chair conformation. Distorted, pseudo-tetrahedral four-coordination at each metal is completed by a pair of monodentate, sulfur donating, 1-methyl-imidazoline-2(3H)-thione neutral and anionic ligands (HgSthione=2.5735(7) and HgSthionate=2.4829(7) Å). NH⋯N hydrogen bonds (N⋯N=2.701 Å) effectively link the terminal ligands into eight-membered chelates.