Complexes of heterocyclic thiones and group twelve metals Part 1. Preparation and characterisation of 1:1 complexes of mercury(II) halides with 1-methylimidazoline-2(3H)-thione: the crystal structure of [( μ2-dibromo) bis( trans{(bromo) (1-methyl-imidazoline-2(3H)-thione)}mercury(II))] at 160 K

Abstract

Stoichiometric (1:1) addition of aqueous alcoholic solutions of 1-methylimidazoline-2(3H)-thione (meimz2SH) to a similar series of mercury(II) halides produced crystalline complexes of empirical formula [HgX 2(meimz2SH)] (X = Cl, Br, l). The chemical formulae of the complexes have been characterised by elemental chemical analysis. IR and 11C NMR spectra indicated the presence of the thione form of the heterocyclic ligands in the complexes, as well as their thione-sulphur ligating character. The crystal structure of [HgBr 2(meinz2SH)] 2] has been determined by single crystal X-ray diffraction methods. The complex crystallises in a monoclinic unit cell with a = 7.7063(13), b = 14.471(3), c = 25.705(4) A ̊ , β = 95.114(9)°, Z = 6 (dimers) and space group P2 1/ n. The asymmetric unit consists of one general dimeric complex and half of a dimeric molecule on an inversion centre. Weak intermolecular secondary contacts occur between terminal bromine and mercury(II) atoms (Hg⋙Br=3.587−3.791 Å). These contacts link the bromo-bridged dimers into weakly associated polymeric sheets, Consequently, the mercury(II) atoms have distorted trigonal-bipyramidal coordination in this complex. The apical sites of the trigonal-bipyramidal polyhedra are occupied by terminal bromine (HgBr terminal = 2.489(2)−2.532(2) Å) and terminal thione-sulphur (HgS = 2.405(4) − 2.419(4) Å) atoms. Equatorial bromine atoms consist of the long intermolecular bromine contacts and the bridging bromine atoms (HgBr bridging = 2.659(2) − 2.859(3) Å). The latter arre also involved in the central, binuclear asymmetric Hg 2(μ-Br) 2 cores. These cores also contain long Hg⋙Hg′ contacts (3.901 and 4.041 Å) and narrow bridgingangles (HgBrHg = 89.90(5)−90.62(5)°). Further intermolecular contacts between the ligand amide (NH) groups and some of the bridging and terminal bromine atoms (NH…Br = 2.555−2.683 Å) generate an extensive H-bonded network.