Acta Cryst. (2008). E64, m13 [ doi:10.1107/S1600536807061491 ]
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N4)mercury(II) dihydrateThe asymmetric unit of the title compound, [HgBr2(C5H4N2O2)2]·2H2O, contains one half-molecule and one water molecule. The HgII ion, lying on a twofold rotation axis, is four-coordinated by two N atoms of pyrazine-2-carboxylic acid ligands and two bromide ions, forming a highly distorted tetrahedral geometry. In the crystal structure, intermolecular O-H
O and O-HN hydrogen bonds link the molecules.
For the preparation of the title compound, mercury(II) bromide (360 mg, 1 mmol) and 2,3-pyrazine dicarboxylic acid (168 mg, 1 mmol) were dissolved in a mixed solvent of ethanol (5 ml) and acetonitrile (5 ml). Then the mixture was added into a Teflon-lined stainless steel autoclave at 413 K for 2 d. The green crystals were obtained after cooling to room temperature and was filtrated. Elemental analysis calcd: C 19.58%, H 4.40%, N 45.60%; Found: C 19.51%, H 4.35%, N 45.53%.
H atoms (for H2O) were located in a difference map and refined [O—H = 0.84 (2) and 0.84 (2) Å, Uiso(H) = 1.5Ueq(O)]. The remaining H atoms were positioned geometrically, with O—H = 0.82 Å (for OH) and C—H = 0.93 Å, for aromatic H atoms and constrained to ride on their parent atoms, with Uiso(H) = xUeq(C,O), where x = 1.2 for aromatic H and x = 1.5 for OH H atoms.
Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software (Enraf–Nonius, 1989); data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2000); software used to prepare material for publication: SHELXTL (Bruker, 2000).
![[Figure 1]](./hk2365fig1thm.gif)
| Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level [symmetry code A: 2 - x, y, 3/2 - z]. Hydrogen bonds are shown as dashed lines. |
![[Figure 2]](./hk2365fig2thm.gif)
| Fig. 2. A packing diagram of (I). Hydrogen bonds are shown as dashed lines. |
| [HgBr2(C5H4N2O2)2]·2H2O | F000 = 1192 |
| Mr = 644.63 | Dx = 2.524 Mg m−3 |
| Monoclinic, C2/c | Mo Kα radiation λ = 0.71073 Å |
| Hall symbol: -C 2yc | Cell parameters from 25 reflections |
| a = 13.895 (1) Å | θ = 9–13º |
| b = 5.7176 (2) Å | µ = 13.82 mm−1 |
| c = 21.8753 (7) Å | T = 294 (2) K |
| β = 102.544 (2)º | Block, green |
| V = 1696.42 (15) Å3 | 0.4 × 0.2 × 0.2 mm |
| Z = 4 |
| Enraf–Nonius CAD-4 diffractometer | Rint = 0.062 |
| Radiation source: fine-focus sealed tube | θmax = 25.1º |
| Monochromator: graphite | θmin = 1.9º |
| T = 294(2) K | h = −16→8 |
| ω/2θ scans | k = −6→5 |
| Absorption correction: ψ scan (North et al., 1968) | l = −20→26 |
| Tmin = 0.048, Tmax = 0.063 | 3 standard reflections |
| 2775 measured reflections | every 200 reflections |
| 1480 independent reflections | intensity decay: none |
| 1287 reflections with I > 2σ(I) |
| 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)] = 0.070 | H atoms treated by a mixture of independent and constrained refinement |
| wR(F2) = 0.150 | w = 1/[σ2(Fo2) + (0.1015P)2 + 4.7441P] where P = (Fo2 + 2Fc2)/3 |
| S = 1.12 | (Δ/σ)max < 0.001 |
| 1480 reflections | Δρmax = 2.85 e Å−3 |
| 112 parameters | Δρmin = −3.62 e Å−3 |
| 2 restraints | Extinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
| Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0045 (4) |
| [HgBr2(C5H4N2O2)2]·2H2O | V = 1696.42 (15) Å3 |
| Mr = 644.63 | Z = 4 |
| Monoclinic, C2/c | Mo Kα |
| a = 13.895 (1) Å | µ = 13.82 mm−1 |
| b = 5.7176 (2) Å | T = 294 (2) K |
| c = 21.8753 (7) Å | 0.4 × 0.2 × 0.2 mm |
| β = 102.544 (2)º |
| Enraf–Nonius CAD-4 diffractometer | 1287 reflections with I > 2σ(I) |
| Absorption correction: ψ scan (North et al., 1968) | Rint = 0.062 |
| Tmin = 0.048, Tmax = 0.063 | 3 standard reflections |
| 2775 measured reflections | every 200 reflections |
| 1480 independent reflections | intensity decay: none |
| R[F2 > 2σ(F2)] = 0.070 | 2 restraints |
| wR(F2) = 0.150 | H atoms treated by a mixture of independent and constrained refinement |
| S = 1.12 | Δρmax = 2.85 e Å−3 |
| 1480 reflections | Δρmin = −3.62 e Å−3 |
| 112 parameters |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 | 1.0000 | 1.10939 (9) | 0.7500 | 0.0355 (4) | |
| Br1 | 1.16422 (12) | 1.2057 (6) | 0.73701 (9) | 0.0525 (6) | |
| C1 | 0.8717 (5) | 0.6941 (4) | 0.6566 (4) | 0.039 (4) | |
| H1 | 0.8234 | 0.7561 | 0.6754 | 0.047* | |
| C2 | 0.8499 (5) | 0.5080 (4) | 0.6166 (4) | 0.041 (4) | |
| H2 | 0.7871 | 0.4427 | 0.6093 | 0.050* | |
| C3 | 1.0047 (6) | 0.5069 (4) | 0.6006 (6) | 0.030 (3) | |
| C4 | 1.0302 (6) | 0.6941 (6) | 0.6411 (6) | 0.043 (5) | |
| H4 | 1.0940 | 0.7538 | 0.6490 | 0.051* | |
| C5 | 1.0825 (6) | 0.4040 (4) | 0.5701 (5) | 0.029 (3) | |
| N1 | 0.9628 (7) | 0.7881 (7) | 0.6688 (6) | 0.033 (3) | |
| N2 | 0.9161 (7) | 0.4188 (7) | 0.5885 (5) | 0.034 (3) | |
| O1 | 1.1642 (8) | 0.4862 (6) | 0.5761 (6) | 0.046 (3) | |
| O2 | 1.0514 (10) | 0.2121 (5) | 0.5379 (6) | 0.060 (4) | |
| H2A | 1.0954 | 0.1606 | 0.5221 | 0.090* | |
| O3 | 0.8315 (9) | 0.0042 (3) | 0.5179 (6) | 0.051 (3) | |
| H3A | 0.794 (2) | −0.090 (3) | 0.531 (2) | 0.077* | |
| H3B | 0.857 (2) | 0.123 (2) | 0.537 (2) | 0.077* |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Hg1 | 0.0234 (5) | 0.0443 (7) | 0.0442 (6) | 0.000 | 0.0149 (3) | 0.000 |
| Br1 | 0.0263 (10) | 0.0587 (14) | 0.0617 (13) | −0.0056 (8) | 0.0225 (9) | 0.0088 (10) |
| C1 | 0.029 (9) | 0.045 (10) | 0.047 (10) | 0.007 (8) | 0.017 (7) | −0.011 (8) |
| C2 | 0.031 (8) | 0.050 (11) | 0.045 (10) | 0.000 (9) | 0.014 (7) | −0.004 (9) |
| C3 | 0.027 (7) | 0.044 (10) | 0.021 (7) | −0.011 (7) | 0.005 (6) | 0.003 (7) |
| C4 | 0.029 (8) | 0.051 (13) | 0.027 (8) | 0.004 (9) | 0.020 (7) | −0.009 (8) |
| C5 | 0.035 (9) | 0.032 (8) | 0.033 (7) | 0.001 (7) | 0.012 (6) | 0.006 (7) |
| N1 | 0.037 (7) | 0.034 (8) | 0.032 (7) | 0.000 (6) | 0.012 (6) | −0.012 (6) |
| N2 | 0.033 (6) | 0.053 (9) | 0.028 (6) | −0.012 (6) | 0.002 (5) | −0.008 (6) |
| O1 | 0.030 (6) | 0.054 (8) | 0.051 (7) | −0.011 (6) | 0.016 (5) | −0.020 (6) |
| O2 | 0.050 (8) | 0.061 (9) | 0.057 (9) | −0.010 (7) | 0.033 (7) | −0.039 (8) |
| O3 | 0.039 (7) | 0.052 (9) | 0.052 (9) | −0.014 (7) | 0.033 (6) | −0.030 (7) |
| Hg1—Br1 | 2.4234 (15) | C3—C4 | 1.381 (6) |
| Hg1—Br1i | 2.4234 (15) | C3—C5 | 1.510 (7) |
| Hg1—N1 | 2.528 (13) | C4—N1 | 1.334 (10) |
| Hg1—N1i | 2.528 (13) | C4—H4 | 0.9300 |
| C1—N1 | 1.351 (7) | C5—O1 | 1.209 (18) |
| C1—C2 | 1.369 (8) | C5—O2 | 1.327 (19) |
| C1—H1 | 0.9300 | O2—H2A | 0.8200 |
| C2—N2 | 1.310 (6) | O3—H3A | 0.84 (2) |
| C2—H2 | 0.9300 | O3—H3B | 0.84 (2) |
| C3—N2 | 1.303 (8) | ||
| Br1—Hg1—Br1i | 153.72 (12) | C4—C3—C5 | 118.4 (6) |
| Br1—Hg1—N1 | 97.8 (3) | N1—C4—C3 | 119.6 (7) |
| Br1i—Hg1—N1 | 101.2 (3) | N1—C4—H4 | 120.2 |
| Br1—Hg1—N1i | 101.2 (3) | C3—C4—H4 | 120.2 |
| Br1i—Hg1—N1i | 97.8 (3) | O1—C5—O2 | 124.8 (7) |
| N1—Hg1—N1i | 86.9 (6) | O1—C5—C3 | 123.1 (8) |
| N1—C1—C2 | 120.3 (8) | O2—C5—C3 | 112.1 (6) |
| N1—C1—H1 | 119.8 | C1—N1—C4 | 118.1 (7) |
| C2—C1—H1 | 119.8 | C1—N1—Hg1 | 118.0 (10) |
| N2—C2—C1 | 121.3 (8) | C4—N1—Hg1 | 123.7 (11) |
| N2—C2—H2 | 119.4 | C2—N2—C3 | 118.7 (8) |
| C1—C2—H2 | 119.4 | C5—O2—H2A | 109.5 |
| N2—C3—C4 | 122.0 (7) | H3A—O3—H3B | 125 (4) |
| N2—C3—C5 | 119.6 (8) | ||
| N1—C1—C2—N2 | −1.0 (12) | C3—C4—N1—Hg1 | 175.2 (12) |
| N2—C3—C4—N1 | −0.3 (13) | Br1—Hg1—N1—C1 | −174.8 (12) |
| C5—C3—C4—N1 | −179.9 (15) | Br1i—Hg1—N1—C1 | −13.0 (13) |
| N2—C3—C5—O1 | 175.2 (15) | N1i—Hg1—N1—C1 | 84.4 (13) |
| C4—C3—C5—O1 | −4.8 (12) | Br1—Hg1—N1—C4 | 10.9 (13) |
| N2—C3—C5—O2 | −7.1 (11) | Br1i—Hg1—N1—C4 | 172.7 (13) |
| C4—C3—C5—O2 | 173.3 (15) | N1i—Hg1—N1—C4 | −89.9 (14) |
| C2—C1—N1—C4 | 0.3 (9) | C1—C2—N2—C3 | 1.8 (12) |
| C2—C1—N1—Hg1 | −175.1 (5) | C4—C3—N2—C2 | −1.1 (11) |
| C3—C4—N1—C1 | 1.2 (9) | C5—C3—N2—C2 | 178.5 (14) |
| Symmetry codes: (i) −x+2, y, −z+3/2. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| O2—H2A···O3ii | 0.82 | 1.75 | 2.56 (2) | 166 |
| O3—H3A···O1iii | 0.84 (2) | 2.28 (3) | 2.89 (2) | 130 (2) |
| O3—H3B···N2 | 0.84 (2) | 2.09 (3) | 2.93 (2) | 177 (3) |
| Symmetry codes: (ii) −x+2, −y, −z+1; (iii) x−1/2, y−1/2, z. |
| Hg1—Br1 | 2.4234 (15) | Hg1—N1 | 2.528 (13) |
| Br1—Hg1—Br1i | 153.72 (12) | Br1i—Hg1—N1 | 101.2 (3) |
| Br1—Hg1—N1 | 97.8 (3) | N1—Hg1—N1i | 86.9 (6) |
| Symmetry codes: (i) −x+2, y, −z+3/2. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| O2—H2A···O3ii | 0.82 | 1.75 | 2.56 (2) | 166 |
| O3—H3A···O1iii | 0.84 (2) | 2.28 (3) | 2.89 (2) | 130 (2) |
| O3—H3B···N2 | 0.84 (2) | 2.09 (3) | 2.93 (2) | 177 (3) |
| Symmetry codes: (ii) −x+2, −y, −z+1; (iii) x−1/2, y−1/2, z. |
The authors thank the Center for Testing and Analysis, Nanjing University for support.
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Functional materials built up by organic ligands and metal ions, especially transition metals, have potential applications in optics, electronics, magnetics, biology, catalyst and medicine (Zhang, 2005; O'Conner et al., 1982). Pyrazine-2,3-dicarboxylic acid, having six possible coordination sites, is a good ligand with versatile coordination types, which is widely used in the self-assembled polymeric coordination synthesis (Zou et al., 1999; Wang et al., 2007). The title compound, (I), was obtained unintentionally as the product of a hydrothermal synthesis of pyrazine-2,3-dicarboxylic acid and mercury(II) bromide. Under high temperature as 413 K and mercury(II) ion catalyst, pyrazine-2,3-dicarboxylic acid is likely to decarboxylate as 2-pyrazine carboxylic acid. We report herein the crystal structure of (I), a complex containing the ligand of 2-pyrazine carboxylic acid.
The asymmetric unit of (I), (Fig. 1), contains one half-molecule and one water molecule, in which the bond lengths and angles are within normal ranges (Allen et al., 1987). The HgII ion lying on a twofold rotation axis, is four -coordinated (Table 1) by two N atoms of pyrazine carboxylic acid ligands and two bromide atoms. The two pyrazine rings are oriented at a dihedral angle of 78.4 (9)°.
The Hg—N [2.528 (13) Å] bond is slightly longer, while Hg—Br [2.4234 (15) Å] bond is slightly shorter than the corresponding values [2.270 (5) Å and 2.5269 (7) Å, respectively] in [Hg(bib)Br2]0.5THF (where bib is 1-bromo-3,5 -bis(imidazol-1-ylmethyl)benzene) (Wang et al., 2007).
In the crystal structure, intermolecular O—H···O and O—H···N hydrogen bonds (Table 2, Fig. 2) link the molecules, in which they seem to be effective in the stabilization of the structure.