Acta Cryst. (2009). E65, m323 [ doi:10.1107/S1600536809005972 ]
The Hg atoms in the crystal structure of the title compound, (CH6N3)2[HgBr4], are tetrahedrally coordinated by four Br atoms and the resulting [HgBr4]2- tetrahedral ions are linked to the [C(NH2)3]+ ions by bromine-hydrogen bonds, forming a three-dimensional network. In the structure, the anions are located on special positions. The two different Hg
Br distances of 2.664 (1) and 2.559 (1) Å observed in the tetrabromidomercurate unit are due to the connection of Br atoms to different number of H atoms.
Guanidinium tetrabromidomercurate(II) was prepared by slow concentration of methanolic solution containing mercuric bromide (0.01 mole) and guanidium bromide (0.02 mole) in 1:2 molar ratio. The purity of the compound was checked by elemental analysis and characterized by its NMR and NQR spectra (Furukawa et al., 2005). The single crystals used in X-ray diffraction studies were grown in methanolic solution by a slow evaporation at room temperature.
The N-H distances were restrained to 0.87 (1)Å and the coordinates of the H atoms were refined with isotropic displacement parameters set to 1.2 times of the Ueq of the parent atom.
Data collection: EXPOSE (Stoe & Cie, 1999); cell refinement: CELL (Stoe & Cie, 1999); data reduction: XPREP (Bruker, 2003); program(s) used to solve structure: SHELXS86 (Sheldrick, 2008); program(s) used to refine structure: SHELXL93 (Sheldrick, 2008); molecular graphics: DIAMOND (Crystal Impact, 2008); software used to prepare material for publication: SHELXL93 (Sheldrick, 2008).
![[Figure 1]](./bt2874fig1thm.gif)
| Fig. 1. Molecular structure of (I), showing the atom labeling scheme. The displacement ellipsoids are drawn at the 50% probability level. The H atoms are represented as small spheres of arbitrary radii. |
![[Figure 2]](./bt2874fig2thm.gif)
| Fig. 2. : Connection scheme of the HgBr42- tetrahedra with the [C(NH2)3]+ ions. |
![[Figure 3]](./bt2874fig3thm.gif)
| Fig. 3. : The planar [C(NH2)3]+ ion. |
| (CH6N3)2[HgBr4] | F(000) = 1144 |
| Mr = 640.41 | Dx = 3.059 Mg m−3 |
| Monoclinic, C2/c | Melting point: not measured K |
| Hall symbol: -C 2yc | Mo Kα radiation, λ = 0.71073 Å |
| a = 10.035 (2) Å | Cell parameters from 2000 reflections |
| b = 11.164 (2) Å | θ = 2.9–26.1° |
| c = 13.358 (3) Å | µ = 22.53 mm−1 |
| β = 111.67 (3)° | T = 298 K |
| V = 1390.7 (6) Å3 | Cylindric, colourless transparent |
| Z = 4 | 0.09 × 0.09 × 0.09 mm |
| Stoe IPDS-I diffractometer | 982 reflections with I > 2σ(I) |
| Radiation source: fine-focus sealed tube | Rint = 0.093 |
| graphite | θmax = 26.1°, θmin = 2.9° |
| imaging plate dynamic profile intergration scans | h = −12→12 |
| 9651 measured reflections | k = −13→13 |
| 1361 independent reflections | l = −16→16 |
| Refinement on F2 | Secondary atom site location: difference Fourier map |
| Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
| R[F2 > 2σ(F2)] = 0.030 | H atoms treated by a mixture of independent and constrained refinement |
| wR(F2) = 0.069 | w = 1/[σ2(Fo2) + (0.0376P)2] where P = (Fo2 + 2Fc2)/3 |
| S = 0.90 | (Δ/σ)max = 0.001 |
| 1361 reflections | Δρmax = 0.71 e Å−3 |
| 79 parameters | Δρmin = −1.03 e Å−3 |
| 6 restraints | Extinction correction: SHELXL93 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
| Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.00077 (10) |
| (CH6N3)2[HgBr4] | V = 1390.7 (6) Å3 |
| Mr = 640.41 | Z = 4 |
| Monoclinic, C2/c | Mo Kα radiation |
| a = 10.035 (2) Å | µ = 22.53 mm−1 |
| b = 11.164 (2) Å | T = 298 K |
| c = 13.358 (3) Å | 0.09 × 0.09 × 0.09 mm |
| β = 111.67 (3)° |
| Stoe IPDS-I diffractometer | 982 reflections with I > 2σ(I) |
| 9651 measured reflections | Rint = 0.093 |
| 1361 independent reflections | θmax = 26.1° |
| R[F2 > 2σ(F2)] = 0.030 | H atoms treated by a mixture of independent and constrained refinement |
| wR(F2) = 0.069 | Δρmax = 0.71 e Å−3 |
| S = 0.90 | Δρmin = −1.03 e Å−3 |
| 1361 reflections | Absolute structure: ? |
| 79 parameters | Flack parameter: ? |
| 6 restraints | Rogers parameter: ? |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
| x | y | z | Uiso*/Ueq | ||
| Hg1 | 0.5000 | 0.71191 (4) | 0.2500 | 0.0577 (2) | |
| Br1 | 0.30789 (8) | 0.86270 (7) | 0.27353 (7) | 0.0555 (2) | |
| Br2 | 0.38905 (10) | 0.60032 (7) | 0.07086 (6) | 0.0635 (3) | |
| C1 | 0.4454 (8) | 0.8215 (6) | 0.6018 (6) | 0.0492 (18) | |
| N1 | 0.5515 (10) | 0.8736 (7) | 0.5829 (6) | 0.070 (2) | |
| H1A | 0.592 (10) | 0.818 (7) | 0.558 (8) | 0.084* | |
| H1B | 0.549 (10) | 0.950 (2) | 0.594 (8) | 0.084* | |
| N2 | 0.4254 (7) | 0.7072 (6) | 0.5904 (6) | 0.0625 (17) | |
| H2A | 0.363 (7) | 0.673 (8) | 0.612 (7) | 0.075* | |
| H2B | 0.485 (8) | 0.665 (7) | 0.571 (7) | 0.075* | |
| N3 | 0.3560 (9) | 0.8857 (7) | 0.6335 (7) | 0.075 (2) | |
| H3A | 0.369 (11) | 0.960 (3) | 0.622 (8) | 0.090* | |
| H3B | 0.278 (7) | 0.856 (9) | 0.636 (9) | 0.090* |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Hg1 | 0.0706 (3) | 0.0544 (3) | 0.0586 (3) | 0.000 | 0.0359 (2) | 0.000 |
| Br1 | 0.0569 (4) | 0.0485 (4) | 0.0714 (5) | −0.0003 (3) | 0.0359 (4) | −0.0070 (4) |
| Br2 | 0.0950 (6) | 0.0453 (5) | 0.0638 (5) | −0.0062 (4) | 0.0454 (5) | −0.0100 (4) |
| C1 | 0.051 (4) | 0.043 (4) | 0.043 (4) | 0.005 (3) | 0.005 (3) | −0.006 (3) |
| N1 | 0.090 (5) | 0.054 (4) | 0.064 (5) | −0.021 (4) | 0.026 (4) | −0.001 (4) |
| N2 | 0.058 (4) | 0.052 (4) | 0.081 (5) | −0.005 (3) | 0.030 (4) | −0.011 (4) |
| N3 | 0.081 (5) | 0.063 (5) | 0.073 (5) | 0.011 (5) | 0.018 (5) | −0.009 (4) |
| Hg1—Br2 | 2.5593 (10) | N1—H1A | 0.87 (9) |
| Hg1—Br2i | 2.5593 (10) | N1—H1B | 0.87 (9) |
| Hg1—Br1 | 2.6639 (9) | N2—H2A | 0.87 (9) |
| Hg1—Br1i | 2.6639 (9) | N2—H2B | 0.87 (9) |
| C1—N2 | 1.293 (10) | N3—H3A | 0.87 (9) |
| C1—N1 | 1.316 (11) | N3—H3B | 0.87 (9) |
| C1—N3 | 1.334 (11) | ||
| Br2—Hg1—Br2i | 121.74 (4) | C1—N1—H1A | 107 (7) |
| Br2—Hg1—Br1 | 109.51 (4) | C1—N1—H1B | 109 (7) |
| Br2i—Hg1—Br1 | 106.33 (3) | H1A—N1—H1B | 144 (10) |
| Br2—Hg1—Br1i | 106.33 (3) | C1—N2—H2A | 120 (6) |
| Br2i—Hg1—Br1i | 109.51 (4) | C1—N2—H2B | 118 (7) |
| Br1—Hg1—Br1i | 101.62 (4) | H2A—N2—H2B | 121 (9) |
| N2—C1—N1 | 121.0 (8) | C1—N3—H3A | 107 (8) |
| N2—C1—N3 | 118.3 (8) | C1—N3—H3B | 122 (8) |
| N1—C1—N3 | 120.7 (7) | H3A—N3—H3B | 125 (10) |
| Symmetry codes: (i) −x+1, y, −z+1/2. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| N1—H1A···Br2i | 0.87 (9) | 3.03 (4) | 3.845 (8) | 158 (9) |
| N1—H1B···Br1ii | 0.87 (9) | 2.77 (6) | 3.512 (7) | 144 (8) |
| N2—H2A···Br1iii | 0.87 (9) | 2.72 (4) | 3.541 (7) | 159 (8) |
| N2—H2B···Br2i | 0.87 (9) | 2.74 (4) | 3.535 (7) | 153 (8) |
| N3—H3A···Br1iv | 0.87 (9) | 3.05 (10) | 3.505 (8) | 115 (8) |
| N3—H3B···Br1iii | 0.87 (9) | 2.98 (8) | 3.667 (9) | 137 (9) |
| Symmetry codes: (i) −x+1, y, −z+1/2; (ii) −x+1, −y+2, −z+1; (iii) −x+1/2, −y+3/2, −z+1; (iv) x, −y+2, z+1/2. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| N1—H1A···Br2i | 0.87 (9) | 3.03 (4) | 3.845 (8) | 158 (9) |
| N1—H1B···Br1ii | 0.87 (9) | 2.77 (6) | 3.512 (7) | 144 (8) |
| N2—H2A···Br1iii | 0.87 (9) | 2.72 (4) | 3.541 (7) | 159 (8) |
| N2—H2B···Br2i | 0.87 (9) | 2.74 (4) | 3.535 (7) | 153 (8) |
| N3—H3A···Br1iv | 0.87 (9) | 3.05 (10) | 3.505 (8) | 115 (8) |
| N3—H3B···Br1iii | 0.87 (9) | 2.98 (8) | 3.667 (9) | 137 (9) |
| Symmetry codes: (i) −x+1, y, −z+1/2; (ii) −x+1, −y+2, −z+1; (iii) −x+1/2, −y+3/2, −z+1; (iv) x, −y+2, z+1/2. |
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Terao, H., Hashimoto, M., Hashimoto, A. & Furukawa, Y. (2000). Z. Naturforsch. Teil A, 55, 230–236.
The guanidium ion, [C(NH2)3]+ is interesting due to its ability of making hydrogen bonds and its unique planar shape (Terao et al., 2000). Further, the guanidium ions tend to undergo reorientation motions about their (pseudo) C3 axes in the crystals. Due to the soft nature of the Hg atom amenable to polarization, the Hg-halogen bonds are sensitive to the intermolecular interactions such as hydrogen bonding (Ishihara et al., 2002). This was evident in the halogen NQR of the Hg compounds in which the resonance lines are widely spread in frequency (Furukawa et al., 2005). Thus we are interested in studying the structure and bonding in this class of compounds. As a part of our study, we report herein the crystal structure of Guanidinium tetrabromidomercurate(II). In the structure, mercury atoms are tetrahedrally coordinated by four bromine atoms and the resulting HgBr4 tetrahedra are interconnected to the [C(NH2)3]+ ions by bromine-hydrogen bonds (Fig. 1) forming a three-dimensional network. In the tetrabromidomercurate unit, two different Hg—Br distances were observed: Hg—Br1 = 2.664 (1) Å and Hg—Br2 = 2.559 (1) Å. The shorter distance of the latter is due to its connection with two hydrogen atoms, whereas the Br1 is connected to four different hydrogen atoms, which elongate the Hg—Br bond (Fig.2). The C(NH2)3 moity (Fig. 3) itself is planar where the N—H bonds are somewhat elongated (1.01 (2) Å) to form the network bonds to the bromine atoms of the HgBr4 tetrahedra.