COMPLEXES OF HETEROCYCLIC THIONES AND GROUP-12 METALS - PART 1 - PREPARATION AND CHARACTERIZATION OF 1 1 COMPLEXES OF MERCURY(II) HALIDES WITH 1-METHYLIMIDAZOLINE-2(3H)-THIONE - THE CRYSTAL-STRUCTURE OF )(1-METHYL-IMIDAZOLINE-2(3H)-THIONE))MERCURY(II))] AT 160 K/

Stoichiometric (1:1) addition of aqueous alcoholic solutions of 1-meth ylimidazoline-2(3H)-thione (meimz2SH) to a similar series of mercury(I I) halides produced crystalline complexes of empirical formula [HgX2(m eimz2SH)] (X = Cl, Br, I). The chemical formulae of the complexes have been characterised by elemental chemical analysis. IR and C-13 NMR sp ectra indicated the presence of the thione form of the heterocyclic li gands in the complexes, as well as their thione-sulphur ligating chara cter. The crystal structure of [{HgBr2(meimz2SH)}(2)] has been determi ned by single crystal X-ray diffraction methods. The complex crystalli ses in a monoclinic unit cell with a = 7.7063(13), b = 14.471 (3), c = 25.705(4) Angstrom, beta = 95.114(9)degrees, Z = 6 (dimers) and space group P2(1)/n. The asymmetric unit consists of one general dimeric co mplex and half of a dimeric molecule on an inversion centre. Weak inte rmolecular secondary contacts occur between terminal bromine and mercu ry(II) atoms (Hg ... Br = 3.587-3.791 Angstrom). These contacts link t he bromo-bridged dimers into weakly associated polymeric sheets. Conse quently, the mercury(II) atoms have distorted trigonal-bipyramidal coo rdination in this complex, The apical sites of the trigonal-bipyramida l polyhedra are occupied by terminal bromine (Hg-Br-terminal = 2.489(2 )-2.532(2) Angstrom) and terminal thione-sulphur (Hg-S = 2.405(4)-2.41 9(4) Angstrom) atoms. Equatorial bromine atoms consist of the long int ermolecular bromine contacts and the bridging bromine atoms (Hg-Br-bri dging = 2.659(2)-2.859(3) Angstrom). The latter are also involved in t he central, binuclear asymmetric Hg-2(mu-Br)(2) cores. These cores als o contain long Hg ... Hg' contacts (3.901 and 4.041 Angstrom) and narr ow bridging angles (Hg-Br-Hg = 89.90(5)-90.62(5)degrees). Further inte rmolecular contacts between the ligand amide (>NH) groups and some of the bridging and terminal bromine atoms (NH ... Br = 2.555-2.683 Angst rom) generate an extensive H-bonded network. (C) 1998 Elsevier Science S.A. All rights reserved.