The ammonium bromomercurates(II) (NH4)Hg5Br11 and (NH4)(4)HgBr6

The crystal structures of two ammonium bromomercurates(II), (NH4)Hg5Br11 (1) and (NH4)(4)HgBr6 (2), were determined from single-crystal X-ray diffraction data: 1: monoclinic, C2/m (no. 12), a = 1231.3(3), b = 1517.4(3), c = 680.4(2) pm, beta = 118.78(2)degrees, Z = 2, R-1 = 0.0391 for I-0 > 2 sigma(I-0); 2: tetragonal, P4/mnc (no. 128), a = 925.6(1), c = 887.2(1) pm, Z = 2, R-1 = 0.0370 for I(0 >)2a(I-0). According to (NH4)Br[HgBr2](5) and (NH4)(4)Br-4[HgBr2] they both contain [Br-Hg-Br] molecules. Additional bromide ions are only loosely attached to the mercury atoms, however involved in (NH4)(+)-Br- bonding.

Crystal structure of pyridinium 1,1 '-bis(4-hydroxy-pyrimid-6-on-2-thion-5-yl)-1 ''-(4-nitrophenyl)methane methanol solvate monohydrate, (C5H6N)(C15H10N5O6S2)center dot CH3OH center dot H2O

C21H22N6O8S2, monoclinic, P12(1)/n1 (no. 14), a = 10.1931(8) angstrom, b = 11.9627(7) angstrom, c = 20.299(2) angstrom, beta = 95.131(4)degrees, V = 2465.2 A(3), Z = 4, R-gt(F) = 0.079, wR(ref)(F-2) = 0.229, T = 100 K.

Bis(trifluoromethyl)mercury(II) complexes with purine and 3,5-dimethyl-4 '-amino-triazole as ligands, [Hg(CF3)(2)(Pur)](4) and [Hg(CF3)(2)(Dat)](2)

Colourless single crystals of [Hg(CF3)(2)(Pur)](4) and [Hg(CF3)(2)(Dat)](2) were obtained from aqueous and etheric solutions of the respective components Purine, (imidazo[4,5-d]pyrimidine, Pur), 3,5-dimethyl-4 '-amino-triazole (Dat) and bis(trifluoromethyl)mercury(II), Hg(CF3)(2). [Hg(CF3)(2)(Pur)](4) crystallizes with the tetragonal system (P-4, Z = 8, a = 1486.8(2), c = 1026.2(l) pm, R-all = 0.0657) with tetrameric molecules consisting of four purine molecules bridged by slightly bent Hg(CF3)2 molecules forming a cage with the CF3 ligands surrounding this cage. The two modifications of [Hg(Dat)(CF3)2]2 (1: 170 K, triclinic, P-1, Z = 2, a 814.9(2), b = 845.4(2), c = 968.4(3) pm, alpha = 106.55(2)degrees, beta= 103.41(2)degrees, gamma = 110.79(2)degrees, R-all = 0.1189; II: monoclinic, P2(1)/c, Z = 8, a = 879.8(2), b = 1731.0(3), c = 1593.9(3) pm, beta = 106.89(2)degrees, R-all = 0.1199) both contain dimeric molecules that are stacked parallel to one crystal axis to strands which are arranged in a parallel fashion in I and rotated against each other in 11 by 110 degrees. In both, the tetrameric [Hg(CF3)(2)(Pur)](4) and the dimeric [Hg(CF3)(2)(Dat)](2) the Hg(CF3)(2) molecules are slightly bent (around 167 and 170 degrees) and rather weakly attached to the N-donor ligands Pur and Dat with Hg-N distances around 272 pm, although in both cases the Hg atoms bridge between two ligand molecules.

Zwitterionic melaminium trichloromercurate(II), [MelH(+)HgCl(3)(-)](Mel)

Colourless long and thin needles of the reaction product of melamine with mercuric chloride in water/methanol, {MelH(+)HgCl(3)(-)}(Mel), crystallize with a structure that contains zwitterionic molecules [MelH(+)HgCl(3)(-)] and

Mercurous azide, Hg-2(N-3)(2)

White polycrystalline mercurous azide, Hg-2(N-3)(2), is obtained by combining aqueous solutions of NaN3 and Hg-2(NO3)(2).2H(2)O (made viscuous by addition of tetramethoxysilane and heating at 65 degreesC). The crystal structure was solved and refined from X-ray powder diffraction data (monoclinic, P2(1)/n, a = 596.07(2) pm, b = 1259.07(4) pm, c = 357.95(1) pm, beta 103.253(2)degrees, Z = 2, R-B = 0.0519). Solid Hg-2(N-3)(2) contains, essentially, molecules of that composition with Hg-Hg distances of 254.4(3) pm, Hg-N distances of 218(2) pm and Hg-Hg-N angles of 178.7(6)degrees. Weak intermolecular interactions with Hg-N distances starting at 280(3) pm lead to a three-dimensional structure.

Affinity of divalent mercury towards nitrogen donor ligands

As with gold, relativistic effects are important in the chemistry of mercury Together with the closed-shell d(10) configuration of Hg2+ they account for the special bonding schemes as preferred linear coordination with highly covalent contributions to chemical bonding or special affinities to nitrogen and sulfur that are so prominent in mercuric chemistry This research report summarizes recent research on coordination compounds with halogen, oxygen and, especially, nitrogen as direct bonding partners of di-valent mercury and their competition with each other. In a rather systematic way N-donor ligands with one, two and more than two nitrogen atoms have been inspected in order to elucidate the influences that lead to the special bonding schemes of Hg-II-N compounds.

Pyrimidine and pyrazine as N-donor ligands in mercurous complexes: [Hg-2(Pym)]NO3)(2), [Hg-2(Pym)](ClO4)(2), and [Hg-2(Pyp)(2)](ClO4)(2)

Colourless single crystals of [Hg-2(Pym)](NO3)(2), [Hg-2(Pym)](ClO4)(2) and [Hg-2(Pyp)(2)](ClO4)(2) were obtained from aqueous solutions of the respective components Hg-2(NO3)(2).2H(2)O, Hg-2(ClO4)(2).6H(2)O, pyrimidine (Pym) and pyrazine (Pyp). The crystal structures were determined from single-crystal X-ray diffractometer data. [Hg-2(Pym)](NO3)(2): monoclinic, C2/c, Z = 8, a = 1607.4(2), b = 652.79(7), c = 2000.5(2) pm, beta = 103.42(2)degrees, R-all = 0.0530; [Hg-2(Pym)](ClO4)(2): orthorhombic, Pnma, Z = 4, a = 1182.7(2), b = 1662.5(2), c = 607.9(1) pm, R-all = 0.0438; [Hg-2(Pyp)(2)](ClO4)(2): orthorhombic, Aba2, Z = 4, a = 1529.39(9), b = 1047.10(14), c = 1133.49(15) pm, R-all = 0.0381. The crystal structures of [Hg-2(Pym)](NO3)(2) and [Hg-2(Pym)](ClO4)(2) contain polymeric cationic chains [Hg-2(Pym)](+) that are arranged to corrugated layers between which the anions are situated. [Hg-2(Pyp)(2)](ClO4)(2) consists of polymeric cationic layers that are built from (Hg-2)(2)(Hg-2)(2/2)(Pyp)(4) rings connected to each other; the perchlorate tetrahedra are located between these layers.

Mercurous dimethylglyoximato nitrate, Hg-2(Dmg)(2)(NO3)(2)

Colourless needles of mercurous dimethylglyoximato nitrate, Hg-2(Dmg)(2)(NO3)(2), grow from a diluted nitric acid solution of mercurous nitrate and dimethylglyoxime. The crystal structure (triclinic, P (1) over bar, a = 728.50(13), b = 1066.8(2), c = 1167.9(2) pm, alpha = 93.78(2)degrees, beta = 94.16(2)degrees, gamma = 98.61(2)degrees, R-all = 0,0726) contains the cations [Hg-2(Dmg)(2)](2+) and

Two mercuric ammoniates: [Hg(NH3)(2)][HgCl3](2) and [Hg(NH3)(4)](ClO4)(2)

[Hg(NH3)(2)][HgCl3](2) (1) is obtained by saturating an equimolar solution of HgCl2 and NH4Cl with Hg(NH2)Cl at 75 degreesC. 1 crystallizes in the orthorhombic space group Pmna with a = 591.9(1) pm, b = 800.3(1) pm, c = 1243.3(4) pm, Z = 2. The structure consists of linear cations [Hg(NH3)(2)](2+) and T-shaped anions [HgCl3](-). The coordination sphere of mercury is

Formation of NH4[Hg-3(NH)(2)](NO3)(3) and transformation to [Hg2N](NO3)

NH4[Hg-3(NH)(2)](NO3)(3) (1) and [Hg2N](NO3) (2) are obtained from cone. aqueous ammonia solutions of Hg(NO3)(2) at ambient temperature and under hydrothermal conditions at 180 degreesC, respectively, as colourless and dark yellow to light brown single crystals. The crystal structures {NH4[Hg-3(NH)(2)](NO3)(3): cubic, P4(I)32, a = 1030.4(2) pm, Z = 4, R-all = 0.028; [Hg2N](NO3): tetragonal, P4(3)2(1)2, a = 1540.4(1), c = 909.8(1) pm, Z = 4, R-all = 0.054} have been determined from single crystal data. Both exhibit network type structures in which [HNHg3] and [NHg4] tetrahedra of the partial structures of 1 and 2 are connected via three and four vertices, respectively. 1 transforms at about 270 degreesC in a straightforward reaction to 2 whereby the decomposition products of NH4NO3 are set free. 2 decomposes at about 380 degreesC forming yellow HgO. Most certainly, I is identical with a mineral previously analyzed as

[Ag(NH3)(2)]ClO4: Crystal structures, phase transition, and vibrational spectra

[Ag(NH3)(2)](ClO4) is obtained from a solution of AgClO4 in cone. ammonia as colourless single crystals (orthorhombic, Pnmn, Z = 4, a = 795.2(1) pm, b 617.7(1) pm, c = 1298.2(2) pm, R-all = 0.0494). The structure consists of linearly coordinated cations, [Ag(NH3)(2)](+), stacked in a staggered conformation and of tetrahedral (ClO4)(-) anions. A first order phase transition was observed between 210 and 200 K and the crystal structure of the low-temperature modification (monoclinic. P2/m, Z = 4, a = 789.9(5) pm, b = 604.1(5) pm, c = 1290.4(5) pm, beta = 97.436(5)degrees, at 170 K, R-all = 0.0636) has also been solved. Spectroscopic investigations (IR/Raman) have been carried out and the assignment of the spectra is discussed.

The structural information content of chemical networks

We present an information-theoretic method to measure the structural information content of networks and apply it to chemical graphs. As a result, we find that our entropy measure is more general than classical information indices known in mathematical and computational chemistry. Further, we demonstrate that our measure reflects the essence of molecular branching meaningfully by determining the structural information content of some chemical graphs numerically.