Acta Cryst. (2007). E63, m1892 [ doi:10.1107/S1600536807027444 ]
The Hg atom in the title compound, (C12H14N2)[HgBr2Cl2], is coordinated by four halogen atoms in a tetrahedral geometry. The cation lies on a centre of inversion and the anion about a mirror plane. The two halogen atoms on the mirror plane are disordered between Br and Cl in ratios of 0.921 (4):0.079 (4) and 0.795 (4):0.205 (4). The halogen atom in the general position is disordered between Br and Cl in a ratio of 0.142 (1):0.858 (1).
The salt was synthesized from the reaction of ethane-1,2-dipyridinium dibromide (0.035 g, 0.1 mmol) in methanol (5 ml) and mercuric chloride (0.054 g, 0.2 mmol) in DMF (10 ml). The mixture was set aside for the formation of colorless needle-shaped crystals in 40% yield after several days. A needle was cut to give a columnar specimen. The organic reactant was synthesized by using a literature method (Xiao et al., 2006).
Of the three halogens in the asymmetric unit, one lies in a general position and the other two on a mirror plane. Initial attempts to refine the structure with either three chlorines or three bromines gave unacceptably high R-indices and large peaks/deep holes. The three halogen atoms were then refined as three (Br+Cl) mixtures; one attempt allowed the mixtures to have the same displacement parameters as well as sharing the same site. Another attempt had the components having the same displacement parameters only. The second led to a formulation consisting of approximately two Br and two Cl atoms. The use of a restraint that fixed the number of Br and Cl atoms as exactly two each led to occupancies of 0.142 (1), 0.921 (4) and 0.795 (4), respectively, for Br1, Br2 and Br3, and 0.858 (1), 0.079 (4) and 0.205 (4), respectively, for Cl1, Cl2 and Cl3. The formulation is in fair agreement with CH&N elemental analysis.
Disorder also affected the cation; the pyridyl ring was refined as a rigid hexagon (C—C = C—N = 1.39 Å). The C(sp3)—C(sp3) distance was restrained to 1.50 (1) Å, and the N···C(sp3) distance to 2.45 (1) Å. The displacement parameters of atoms of the cation were restrained to be nearly isotropic. C-bound H atoms were positioned geometrically (C–H = 0.93 and 0.97 Å), and were included in the refinement in the riding model approximation, with Uiso(H) = 1.2Ueq(C).
The final difference Fourier map had a large peak at 0.89 Å from N1, indicating a possible disorder in the cation. But no suitable disorder model was found for the cation.
Data collection: SMART (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: X-SEED (Barbour, 2001); software used to prepare material for publication: publCIF (Westrip, 2007).
![[Figure 1]](./ci2386fig1thm.gif)
| Fig. 1. The molecular structure of [C12H14N2][HgBr2Cl2], with displacement ellipsoids drawn at the 50% probability level. The bromine and chlorine atoms are disordered; the figures depicts the anion as an [HgX4]2− species. The halogen atom in the general position is labelled X1 (and the symmetry-related X1i); those in the special position are labelled X2 and X3. Hydrogen atoms are drawn as spheres of arbitrary radius. [Symmetry code (i): x, 3/2 – y, z.]. Unlabelled atoms in the cation are related to the labelled ones by the symmetry code (1 – x, 1 – y, 1 – z). |
| (C12H14N2)[HgBr2Cl2] | F000 = 1136 |
| Mr = 617.56 | Dx = 2.382 Mg m−3 |
| Orthorhombic, Pnma | Mo Kα radiation λ = 0.71073 Å |
| Hall symbol: -P 2ac 2n | Cell parameters from 2764 reflections |
| a = 17.952 (1) Å | θ = 2.3–22.7º |
| b = 14.381 (1) Å | µ = 13.88 mm−1 |
| c = 6.6707 (5) Å | T = 298 (2) K |
| V = 1722.1 (2) Å3 | Column, colourless |
| Z = 4 | 0.20 × 0.10 × 0.10 mm |
| Bruker APEX area-detector diffractometer | 1573 independent reflections |
| Radiation source: fine-focus sealed tube | 1395 reflections with I > 2σ(I) |
| Monochromator: graphite | Rint = 0.038 |
| T = 298(2) K | θmax = 25.0º |
| φ and ω scans | θmin = 2.3º |
| Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | h = −21→20 |
| Tmin = 0.168, Tmax = 0.338 | k = −16→17 |
| 9021 measured reflections | l = −7→7 |
| 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)] = 0.034 | H-atom parameters constrained |
| wR(F2) = 0.102 | w = 1/[σ2(Fo2) + (0.0654P)2 + 2.4853P] where P = (Fo2 + 2Fc2)/3 |
| S = 1.05 | (Δ/σ)max = 0.001 |
| 1572 reflections | Δρmax = 1.40 e Å−3 |
| 92 parameters | Δρmin = −1.17 e Å−3 |
| 57 restraints | Extinction correction: none |
| Primary atom site location: structure-invariant direct methods |
| (C12H14N2)[HgBr2Cl2] | V = 1722.1 (2) Å3 |
| Mr = 617.56 | Z = 4 |
| Orthorhombic, Pnma | Mo Kα |
| a = 17.952 (1) Å | µ = 13.88 mm−1 |
| b = 14.381 (1) Å | T = 298 (2) K |
| c = 6.6707 (5) Å | 0.20 × 0.10 × 0.10 mm |
| Bruker APEX area-detector diffractometer | 1573 independent reflections |
| Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 1395 reflections with I > 2σ(I) |
| Tmin = 0.168, Tmax = 0.338 | Rint = 0.038 |
| 9021 measured reflections |
| R[F2 > 2σ(F2)] = 0.034 | 57 restraints |
| wR(F2) = 0.102 | H-atom parameters constrained |
| S = 1.05 | Δρmax = 1.40 e Å−3 |
| 1572 reflections | Δρmin = −1.17 e Å−3 |
| 92 parameters |
| x | y | z | Uiso*/Ueq | Occ. (<1) | |
| Hg1 | 0.92942 (2) | 0.7500 | 0.65028 (6) | 0.0427 (2) | |
| Br1 | 0.913 (4) | 0.606 (5) | 0.471 (9) | 0.058 (2) | 0.142 (1) |
| Cl1 | 0.9142 (14) | 0.6012 (19) | 0.441 (3) | 0.058 (2) | 0.858 (1) |
| Br2 | 0.8251 (2) | 0.7500 | 0.9091 (3) | 0.0849 (8) | 0.921 (4) |
| Cl2 | 0.821 (8) | 0.7500 | 0.853 (14) | 0.0849 (8) | 0.079 (4) |
| Br3 | 1.06769 (13) | 0.7500 | 0.7582 (4) | 0.0631 (7) | 0.795 (4) |
| Cl3 | 1.0543 (16) | 0.7500 | 0.818 (5) | 0.0631 (7) | 0.205 (4) |
| N1 | 0.59356 (19) | 0.5290 (3) | 0.4047 (7) | 0.066 (2) | |
| C1 | 0.6519 (3) | 0.5275 (4) | 0.5418 (6) | 0.078 (3) | |
| H1 | 0.6479 | 0.4924 | 0.6583 | 0.094* | |
| C2 | 0.7161 (2) | 0.5786 (4) | 0.5046 (7) | 0.057 (2) | |
| H2 | 0.7551 | 0.5776 | 0.5963 | 0.068* | |
| C3 | 0.7221 (2) | 0.6311 (4) | 0.3304 (7) | 0.059 (2) | |
| H3 | 0.7651 | 0.6653 | 0.3056 | 0.071* | |
| C4 | 0.6638 (3) | 0.6325 (4) | 0.1933 (6) | 0.055 (2) | |
| H4 | 0.6678 | 0.6677 | 0.0768 | 0.067* | |
| C5 | 0.5995 (2) | 0.5815 (4) | 0.2305 (7) | 0.064 (2) | |
| H5 | 0.5605 | 0.5824 | 0.1388 | 0.077* | |
| C6 | 0.5273 (3) | 0.4739 (4) | 0.4394 (11) | 0.075 (3) | |
| H6A | 0.5407 | 0.4170 | 0.5085 | 0.090* | |
| H6B | 0.5050 | 0.4572 | 0.3118 | 0.090* |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Hg1 | 0.0363 (3) | 0.0426 (3) | 0.0491 (3) | 0.000 | 0.00310 (16) | 0.000 |
| Br1 | 0.0424 (11) | 0.064 (3) | 0.067 (7) | −0.0014 (15) | −0.001 (4) | −0.031 (4) |
| Cl1 | 0.0424 (11) | 0.064 (3) | 0.067 (7) | −0.0014 (15) | −0.001 (4) | −0.031 (4) |
| Br2 | 0.0753 (12) | 0.1119 (13) | 0.0676 (17) | 0.000 | 0.0385 (16) | 0.000 |
| Cl2 | 0.0753 (12) | 0.1119 (13) | 0.0676 (17) | 0.000 | 0.0385 (16) | 0.000 |
| Br3 | 0.0350 (12) | 0.0791 (11) | 0.0751 (19) | 0.000 | −0.0030 (9) | 0.000 |
| Cl3 | 0.0350 (12) | 0.0791 (11) | 0.0751 (19) | 0.000 | −0.0030 (9) | 0.000 |
| N1 | 0.031 (3) | 0.096 (5) | 0.072 (4) | −0.011 (4) | −0.002 (3) | 0.031 (4) |
| C1 | 0.057 (5) | 0.104 (6) | 0.075 (6) | −0.010 (5) | −0.009 (4) | 0.033 (5) |
| C2 | 0.025 (4) | 0.069 (5) | 0.076 (5) | −0.003 (3) | −0.008 (3) | 0.017 (4) |
| C3 | 0.041 (4) | 0.066 (5) | 0.070 (5) | −0.009 (4) | 0.004 (4) | 0.016 (4) |
| C4 | 0.049 (5) | 0.054 (4) | 0.063 (4) | −0.015 (4) | 0.004 (4) | 0.010 (4) |
| C5 | 0.047 (4) | 0.075 (5) | 0.070 (5) | −0.011 (4) | 0.004 (4) | 0.022 (4) |
| C6 | 0.087 (6) | 0.066 (5) | 0.073 (5) | 0.018 (5) | −0.008 (5) | −0.008 (4) |
| Hg1—Cl2 | 2.37 (11) | C1—H1 | 0.93 |
| Hg1—Br1 | 2.41 (5) | C2—C3 | 1.39 |
| Hg1—Br1i | 2.41 (5) | C2—H2 | 0.93 |
| Hg1—Cl3 | 2.50 (3) | C3—C4 | 1.39 |
| Hg1—Br2 | 2.548 (3) | C3—H3 | 0.93 |
| Hg1—Cl1i | 2.571 (19) | C4—C5 | 1.39 |
| Hg1—Cl1 | 2.571 (19) | C4—H4 | 0.93 |
| Hg1—Br3 | 2.584 (3) | C5—H5 | 0.93 |
| N1—C1 | 1.39 | C6—C6ii | 1.476 (6) |
| N1—C5 | 1.39 | C6—H6A | 0.97 |
| N1—C6 | 1.448 (6) | C6—H6B | 0.97 |
| C1—C2 | 1.39 | ||
| Cl2—Hg1—Br1i | 101 (2) | C1—N1—C5 | 120.0 |
| Cl2—Hg1—Br1 | 101 (2) | C1—N1—C6 | 120.4 (4) |
| Br1i—Hg1—Br1 | 119 (4) | C5—N1—C6 | 119.6 (4) |
| Cl2—Hg1—Cl3 | 119 (3) | N1—C1—C2 | 120.0 |
| Br1i—Hg1—Cl3 | 109.1 (17) | N1—C1—H1 | 120.0 |
| Br1—Hg1—Cl3 | 109.1 (17) | C2—C1—H1 | 120.0 |
| Br1i—Hg1—Br2 | 104.4 (16) | C3—C2—C1 | 120.0 |
| Br1—Hg1—Br2 | 104.4 (16) | C3—C2—H2 | 120.0 |
| Cl3—Hg1—Br2 | 110.9 (6) | C1—C2—H2 | 120.0 |
| Cl2—Hg1—Cl1i | 103.0 (16) | C4—C3—C2 | 120.0 |
| Br1—Hg1—Cl1i | 115.7 (11) | C4—C3—H3 | 120.0 |
| Cl3—Hg1—Cl1i | 109.7 (7) | C2—C3—H3 | 120.0 |
| Br2—Hg1—Cl1i | 106.9 (6) | C3—C4—C5 | 120.0 |
| Cl2—Hg1—Cl1 | 103.0 (16) | C3—C4—H4 | 120.0 |
| Br1i—Hg1—Cl1 | 115.7 (11) | C5—C4—H4 | 120.0 |
| Cl3—Hg1—Cl1 | 109.7 (6) | C4—C5—N1 | 120.0 |
| Br2—Hg1—Cl1 | 106.9 (6) | C4—C5—H5 | 120.0 |
| Cl1i—Hg1—Cl1 | 112.7 (13) | N1—C5—H5 | 120.0 |
| Cl2—Hg1—Br3 | 129 (3) | N1—C6—C6ii | 110.8 (6) |
| Br1i—Hg1—Br3 | 104.6 (16) | N1—C6—H6A | 109.5 |
| Br1—Hg1—Br3 | 104.6 (16) | C6ii—C6—H6A | 109.5 |
| Br2—Hg1—Br3 | 121.16 (9) | N1—C6—H6B | 109.5 |
| Cl1i—Hg1—Br3 | 104.7 (6) | C6ii—C6—H6B | 109.5 |
| Cl1—Hg1—Br3 | 104.7 (6) | H6A—C6—H6B | 108.1 |
| C6—N1—C1—C2 | 178.2 (3) | C1—N1—C6—C6ii | 87.7 (9) |
| C6—N1—C5—C4 | −178.2 (3) | C5—N1—C6—C6ii | −94.1 (9) |
| Symmetry codes: (i) x, −y+3/2, z; (ii) −x+1, −y+1, −z+1. |
| Hg1—Cl2 | 2.37 (11) | Hg1—Br2 | 2.548 (3) |
| Hg1—Br1 | 2.41 (5) | Hg1—Cl1 | 2.571 (19) |
| Hg1—Cl3 | 2.50 (3) | Hg1—Br3 | 2.584 (3) |
The authors thank the National Natural Science Foundation of China (grant No. 20671083), the Henan Province Excellent Young Foundation (grant No. 0612002800), Zhengzhou University and the University of Malaya for supporting this work. We thank Central China Normal University for the diffraction measurements.
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The discrete tetrahedral tetrahalogenomercurate(II) dianion is characterized in a number of salts (Allen, 2002; CSD Version 5.28); examples of the ammonium salts include, for example, bis(tetramethylammonium) tetrachloromercurate (Amami et al., 2002), bis(tetramethylammonium) tetrabromomercurate (Kamenar & Nagl, 1976) and bis(tetramethylammonium) tetraiodomercurate (Pakhomov et al., 1991; Pickardt et al., 2006). The mercury atom in [C12H14N2][HgBr2Cl2] is coordinated by four halogen atoms in a tetrahedral geometry; the halogen atoms are disordered (Fig. 1). Selected bond distances are given in Table 1.