Željka Soldin

Mercury(II) complexes of heterocyclic thiones. Part 1. Preparation of 1:2 complexes of mercury(II) halides and pseudohalides with 3, 4, 5, 6-tetrahydropyrimidine-2-thione. X-ray, thermal analysis and NMR studies

A series of complexes HgX_2(H_4pymtH)_2 (X = Cl, Br, I, SCN, CN ; H_4pymtH = 3, 4, 5, 6-tetrahydropyrimidine-2-thione) has been obtained by the reaction of H_4pymtH with mercury(II) halides and pseudohalides in the 2:1 molar ratio. X-ray diffraction studies revealed tetrahedral coordination of mercury with S-bound H4pymtH. The exception is Hg(CN)_2(H_4pymtH)_2 where the coordination is 2+2 with two strongly bound CN� {; ; ; ; ; ligands and weaker Hg� {; ; ; ; ; S bonds with H4pymtH. One- and twodimensional 1^H and 13^C NMR measurements in dimethylsulfoxide solution confirmed the complexation of mercury to sulphur. The greatest complexation effects on chemical shifts were detected for the C-2, C-5 and H-1, 3 atoms i.e. two, four and five bonds away from mercury atom. The complexation effects in Hg(SCN)_2(H_4pymtH)_2 and Hg(CN)_2(H_4pymtH)_2 are in agreement with the strongest intramolecular H-bonding in the former and the weakest Hg-S bonds in the latter as compared to other complexes here.

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 HgX2L, and HgX2L2 (X=Cl−, Br−, I−, SCN−; L=imtH2, meimtH; imtH2=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 HgL2 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 HgX2L and HgX2L2 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 HgI2(imtH2), HgBr2(imtH2)2 and Hg(meimt)2 have been determined by X-ray diffractometry and revealed S-bound imtH2 in the iodo and bromo complex, while in Hg(meimt)2 the ligand acts as bridging with stronger S and weaker N bonds.

Mercury(II) Complexes with Heterocyclic Thiones- Preparation and Characterization of the 1:1 and 1:2 Mercury(II) Complexes with Benzo-1, 3-imidazole-2-thione

A series of complexes HgX2 (bzimtH_2 ) and HgX_2 (bzimtH2)_2 (X =Cl^- , Br^- , I^- , SCN^- ; bzimtH_2 = benzo-1, 3-imidazole-2-thione) was obtained by reaction of the mercury(II) salts with benzo-1, 3-imidazole-2-thione in the appropriate molar ratio(1:1 or 1:2). Hg(bzimtH)_2 was obtained by the deprotonation of bzimtH_2 with mercury(II) acetate (irrespective of the molar ratio of the reactants). The complexes were characterised by chemical and thermal analysis, IR, 1^H, and 13^C NMR spectroscopy, and some [HgX_2(bzimtH_2), X =I^- and HgX_2(bzimtH_2)_2 , X =I^- and SCN^-] by X-ray single crystal diffractometry. 1^H and 13^C NMR spectroscopic measurements in dimethyl sulphoxide revealed that the sulphur atom is coordinated to the mercury centre. The greatest complexation effects on the chemical shifts were observed for the thione carbon atom and thioamide proton. The crystal structures of HgI_2(bzimtH_2)_2 and Hg(SCN)_2 (bzimtH_2)_2 ˇC_2H_5OH consist of discrete monomeric molecules with halide or pseudohalide donor atoms and thione sulphur atoms tetrahedrally coordinated to the mercury atom. The structure of HgI2 (bzimtH2 )is polymeric with a trigonal bipyramidal 3 + 2 coordination geometry around the mercury atom. Polymerisation occurs through HgˇˇˇI interactions with neighbouring molecules. The distribution of the pi-electron density in bzimtH_2 corresponds to the thioketo tautomeric form in the solid state, and also in the DMSO solution of the complexes. Intermolecular hydrogen bonds of the type N-HˇˇˇN, N-HˇˇˇS and N-HˇˇˇI are observed.

catena-Poly­[[(2-methyl-1,3-benzo­thia­zole-N)­mercury(II)]-di-μ-chloro]

The reaction of 2-methyl-1,3-benzothiazole (mebta) with mercury(II) chloride in methanol in a 1:1 molar ratio resulted in the formation of single crystals of the title compound, [HgCl 2 (C 8 H 7 NS)] n . The molecules exist as continuous chlorine-bridged chains in which Hg atoms lie in distorted trigonal bipyramidal environments. The equatorial positions are occupied by an N atom from the ligand [2.236 (8) A and two Cl atoms [2.428 (3) and 2.459 (3) A]. The two axial Hg-Cl contacts to two neighbouring molecules [2.874 (3) and 2.964 (3) A] are significantly shorter than the sum of the respective van der Waals radii, and form close to linear Cl-Hg-Cl sequences [177.80 (7)].

Building inorganic supramolecular architectures using principles adopted from the organic solid state

The possibility of converting crystal engineering principles that originate in the organic solid state into productive strategies for the effective supramolecular assembly of coordination complexes has been established through a range of complementary techniques. Calculated molecular electrostatic potentials, in conjunction with a systematic structural study, demonstrate that the existence and structural importance of the key hydrogen-bond interactions are not disrupted by the presence of metal cations and charge-balancing anions.

Polymeric μ-bromo-μ-pyridine-3-carboxylato-κ3O, O':N-mercury(II)

The asymmetric unit of the title polymeric complex, [HgBr(C(6)H(4)NO(2))](n) or HgBr(nic), contains mercury coordinated via two Br atoms [Hg-Br = 2.6528 (9) and 2.6468 (9) A], two carboxylate O atoms, which form a characteristic four-membered chelate ring [Hg-O = 2.353 (6) and 2.478 (7) A], and an N atom [Hg-N = 2.265 (5) A], in the form of a very irregular (3+2)-coordination polyhedron. The pronounced irregularity of the effective Hg (3+2)-coordination is a result of the rigid stereochemistry of the nicotinate ligand. According to the covalent and van der Waals radii criteria, the strongest bonds are Hg-Br and Hg-N. These covalent interactions form a two-dimensional polymer. The puckered planes are connected by van der Waals interactions, and there are only two intermolecular C-H...O hydrogen bonds [3.428 (10) and 3.170 (10) A].

Aquabromo(6-carboxypyridine-2-carboxylato- O , N , O ')mercury(II)

The title compound, [HgBr(C7H4NO4)(H2O)], was obtained by the reaction of an aqueous solution of mercury(II) bromide and pyridine-2,6-dicarboxylic acid (picolinic acid, dipicH(2)). The shortest bond distances to Hg are Hg-Br 2.412 (1) A and Hg-N 2.208 (5) A; the corresponding N-Hg-Br angle of 169.6 (1) degrees corresponds to a slightly distorted linear coordination. There are also four longer Hg-O interactions, three from dipicH(-) [2.425 (4) and 2.599 (4) A within the asymmetric unit, and 2.837 (4) A from a symmetry-related molecule] and one from the bonded water molecule [2.634 (4) A]. The effective coordination of Hg can thus be described as 2+4. The molecules are connected to form double-layer chains parallel to the y axis by strong O-H.O hydrogen bonds between carboxylic acid groups of neighbouring molecules, and by weaker hydrogen bonds involving both H atoms of the water molecule and the O atoms of the carboxylic acid groups.

A Design of Mercury(II) Coordination Polymers with Pyridinedicarboxylic Acids: Structural, Spectroscopic and Thermal Studies

Two novel mercury(II) coordination polymers, two-dimensional [HgCl(2,3-pydcH)(H2O)]n (1) and one-dimensional [HgCl(2,5-pydcH)(DMF)]n (2) (2,3-pydcH2 = pyridine-2,3-dicarboxylic acid; 2,5-pydcH2 = pyridine-2,5-dicarboxylic acid), were prepared in the reactions of the corresponding pyridinedicarboxylic acid with mercury(II) chloride. Their structures were solved by the single-crystal X-ray diffraction method. Both 2,3-pydcH− and 2,5-pydcH− are partially deprotonated bridging ligands which display similar coordination modes, acting as N,O-bidentate and O’-monodentate ligands in the structures of 1 and 2, respectively. The presence of DMF in the reaction mixture led to the formation of a 1D coordination polymer, while a 2D coordination polymer was formed in the absence of DMF. Spectroscopic analysis of 1 and 2 was performed by IR spectroscopy in the solid state and by 1H and 13C NMR spectroscopy in the DMSO solutions. Thermal properties of the coordination polymers 1 and 2 were also investigated. NMR data support complete decomposition of 1 and a preserved polymeric structure of 2 in the DMSO solution.Graphical Abstract

Hydrogen-Bonded Frameworks of Mercury(ii) Complexes with Pyridinedicarboxylic Acids

Three novel mercury(ii) coordination compounds, [HgCl(2,4-pydcH2)(2,4-pydcH)]·2H2O (1) and [HgCl(2,6-pydcH)(H2O)]·3H2O (2) that exhibit hydrogen-bonded 3D frameworks, and [Hg(2,6-pydcH)2]·2H2O (3), exhibiting only hydrogen-bonded 1D chains (2,4-pydcH2 = pyridine-2,4-dicarboxylic acid; 2,6-pydcH2 = pyridine-2,6-dicarboxylic acid), were prepared in the reactions of the corresponding pyridinedicarboxylic acid with mercury(ii) chloride or mercury(ii) acetate. Compounds 1–3 were prepared by conventional solution synthesis. Only the hydrogen-bonded 1D chain of 3 was robust enough to be prepared by mechanochemical synthesis. The crystal structures of 1–3 were determined by the single-crystal X-ray diffraction method. Neutral 2,4-pydcH2 and partially deprotonated 2,4-pydcH− act as N,O-bidentate ligands in the structure of 1 whereas crystal structure analysis reveals O,N,O′-tridentate 2,6-pydcH− ligand in the structures of 2 and 3. Compounds 1–3 were characterised by IR spectroscopy in the solid state, and compounds 1 and 2 were also characterised by 1H and 13C NMR spectroscopy in DMSO solution. Thermal properties of 1–3 were also investigated. NMR data support a collapse of the hydrogen-bonded frameworks of 1 and 2 in DMSO solution, and the existence of monomeric species in DMSO solutions.

From versatile hydrogen- and halogen-bond acceptors to elastic bending of metal- containing architectures

In order to use weak interactions as effective tools in deliberate synthesis of desired metal- containing supramolecular assemblies a very detailed understanding of the importance of different noncovalent interactions is required. Thanks to their comparable strengths and directionalities, hydrogen and halogen bonds have emerged as key synthetic tools in this context. To establish similarities and possible mimicry of the two types of interactions we have carried out a structural examination of a series of metal-based halide complexes with pyridine-type ligands equipped with functionalities capable of forming of either hydrogen or halogen bonds. Our results indicate that synthon- transferability from system to system, regardless of the building- block dimensionality, is a genuine possibility. Some surprising physical properties, including elastic bending, will be discussed against a backdrop of weak interactions using a combination of experiment and theory.