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-methylimidazoline-2(3H)-thionate)-(μ2-S,N-1-methylimidazoline-2-thionate)mercury(II)}] at 160 K

Two complexes of mercury(II) and the ani on 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, mu(2)-S,N(eta(1)-S;eta(1)-N), 1-methylimidazoline-2(3H)-thionate anionic ligands (Hg-S-bridging = 2.5196(6), Hg-N = 2.325(2) Angstrom, N-C-S-exo = 126.0(2)degrees). 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-S-thione = 2.5735(7) and Hg-S-thionate = 2.4829(7) Angstrom). N-H ... N hydrogen bonds (N ... N = 2.701 Angstrom) effectively link the terminal ligands into eight-membered chelates. (C) 2000 Elsevier Science S.A. All rights reserved.