Acta Cryst. (2007). E63, o2783 [ doi:10.1107/S1600536807015802 ]
In the title compound, C7H5O2-·CH6N3+, the cation and anion lie on crystallographic mirror planes. The bond length in the deprotonated carboxyl group is intermediate between normal single and double Csp2=O bond lengths, indicating delocalization of the charge over both O atoms of the COO- group. Hydrogen bonds assemble the ions into layers in the bc plane.
The title compound was prepared by adding benzoic acid (Aldrich 99.5%; 1.1 mmol) to guanidinium carbonate (Aldrich 99%; 0.55 mmol) dissolved in water (60 ml). The solution was warmed slowly and then left to evaporate under ambient conditions. After a few days, small colourless transparent single crystals of (I) were deposited.
All H atoms were located in a difference Fourier synthesis. The guanidinium H-atom coordinates were refined, with Uiso(H) = 1.2Ueq(N). The H atoms of the anion were placed in calculated positions and refined as riding on their parent atoms, with C—H = 0.93 Å and Uiso(H) = 1.2Ueq(C).
Data collection: APEX2 (Bruker, 2005); cell refinement: APEX2; data reduction: APEX2; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97.
![[Figure 1]](./bt2327fig1thm.gif)
| Fig. 1. A plot of the title compound. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (a) x, 1/2 - y, z; (b) x, 3/2 - y, z.] |
![[Figure 2]](./bt2327fig2thm.gif)
| Fig. 2. A packing diagram for (I), viewed down the b axis, showing the layer formation. Hydrogen bonds are shown as dashed lines. |
![[Figure 3]](./bt2327fig3thm.gif)
| Fig. 3. A packing diagram for (I), viewed down the c axis, with the hydrogen bonds depicted by dashed lines. |
| CH6N3+·C7H5O2− | F(000) = 384 |
| Mr = 181.20 | Dx = 1.194 Mg m−3 |
| Orthorhombic, Pnma | Mo Kα radiation, λ = 0.71073 Å |
| Hall symbol: -P 2ac 2n | Cell parameters from 6505 reflections |
| a = 15.7347 (8) Å | θ = 2.9–23.6° |
| b = 8.1216 (4) Å | µ = 0.09 mm−1 |
| c = 7.8885 (4) Å | T = 293 K |
| V = 1008.08 (9) Å3 | Block, colourless |
| Z = 4 | 0.25 × 0.13 × 0.07 mm |
| Bruker APEX2 CCD area-detector diffractometer | 960 independent reflections |
| Radiation source: fine-focus sealed tube | 735 reflections with I > 2σ(I) |
| graphite | Rint = 0.035 |
| φ and ω scans | θmax = 25.1°, θmin = 2.6° |
| Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | h = −18→18 |
| Tmin = 0.927, Tmax = 0.994 | k = −9→9 |
| 27265 measured reflections | l = −9→9 |
| Refinement on F2 | Primary atom site location: structure-invariant direct methods |
| Least-squares matrix: full | Secondary atom site location: difference Fourier map |
| R[F2 > 2σ(F2)] = 0.035 | Hydrogen site location: inferred from neighbouring sites |
| wR(F2) = 0.101 | H atoms treated by a mixture of independent and constrained refinement |
| S = 1.04 | w = 1/[σ2(Fo2) + (0.0512P)2 + 0.1512P] where P = (Fo2 + 2Fc2)/3 |
| 960 reflections | (Δ/σ)max < 0.001 |
| 76 parameters | Δρmax = 0.09 e Å−3 |
| 0 restraints | Δρmin = −0.16 e Å−3 |
| CH6N3+·C7H5O2− | V = 1008.08 (9) Å3 |
| Mr = 181.20 | Z = 4 |
| Orthorhombic, Pnma | Mo Kα radiation |
| a = 15.7347 (8) Å | µ = 0.09 mm−1 |
| b = 8.1216 (4) Å | T = 293 K |
| c = 7.8885 (4) Å | 0.25 × 0.13 × 0.07 mm |
| Bruker APEX2 CCD area-detector diffractometer | 960 independent reflections |
| Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | 735 reflections with I > 2σ(I) |
| Tmin = 0.927, Tmax = 0.994 | Rint = 0.035 |
| 27265 measured reflections | θmax = 25.1° |
| R[F2 > 2σ(F2)] = 0.035 | H atoms treated by a mixture of independent and constrained refinement |
| wR(F2) = 0.101 | Δρmax = 0.09 e Å−3 |
| S = 1.04 | Δρmin = −0.16 e Å−3 |
| 960 reflections | Absolute structure: ? |
| 76 parameters | Flack parameter: ? |
| 0 restraints | Rogers parameter: ? |
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 | ||
| O1 | 0.14899 (6) | 0.11435 (12) | 0.01484 (12) | 0.0621 (4) | |
| C1 | 0.21113 (11) | 0.7500 | 0.1719 (2) | 0.0487 (5) | |
| C2 | 0.11899 (11) | 0.2500 | 0.0607 (2) | 0.0466 (5) | |
| C3 | 0.04384 (11) | 0.2500 | 0.1780 (2) | 0.0509 (5) | |
| C4 | 0.00836 (10) | 0.1032 (2) | 0.2325 (2) | 0.0684 (5) | |
| H4 | 0.0313 | 0.0038 | 0.1962 | 0.082* | |
| C5 | −0.06091 (10) | 0.1034 (3) | 0.3405 (2) | 0.0913 (6) | |
| H5 | −0.0842 | 0.0044 | 0.3773 | 0.110* | |
| C6 | −0.09507 (17) | 0.2500 | 0.3930 (3) | 0.0990 (10) | |
| H6 | −0.1419 | 0.2500 | 0.4650 | 0.119* | |
| N1 | 0.23780 (9) | 0.60957 (15) | 0.23598 (18) | 0.0634 (4) | |
| H1A | 0.2775 (10) | 0.6096 (19) | 0.323 (2) | 0.076* | |
| H1B | 0.2182 (9) | 0.521 (2) | 0.191 (2) | 0.076* | |
| N2 | 0.15725 (12) | 0.7500 | 0.0424 (2) | 0.0648 (5) | |
| H2 | 0.1368 (10) | 0.848 (2) | 0.0030 (19) | 0.078* |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| O1 | 0.0749 (7) | 0.0404 (6) | 0.0709 (7) | 0.0054 (4) | 0.0148 (5) | 0.0038 (5) |
| C1 | 0.0506 (10) | 0.0433 (10) | 0.0520 (11) | 0.000 | −0.0003 (9) | 0.000 |
| C2 | 0.0538 (10) | 0.0399 (11) | 0.0462 (10) | 0.000 | −0.0039 (8) | 0.000 |
| C3 | 0.0517 (11) | 0.0592 (12) | 0.0418 (10) | 0.000 | −0.0069 (8) | 0.000 |
| C4 | 0.0633 (9) | 0.0781 (11) | 0.0638 (9) | −0.0054 (7) | 0.0006 (7) | 0.0148 (8) |
| C5 | 0.0696 (11) | 0.1285 (17) | 0.0757 (12) | −0.0177 (11) | 0.0059 (9) | 0.0298 (12) |
| C6 | 0.0653 (16) | 0.170 (3) | 0.0618 (16) | 0.000 | 0.0113 (12) | 0.000 |
| N1 | 0.0737 (9) | 0.0417 (7) | 0.0748 (9) | 0.0040 (6) | −0.0205 (7) | −0.0017 (6) |
| N2 | 0.0758 (12) | 0.0506 (11) | 0.0680 (11) | 0.000 | −0.0234 (10) | 0.000 |
| O1—C2 | 1.2519 (13) | C4—H4 | 0.9300 |
| C1—N1i | 1.3162 (15) | C5—C6 | 1.371 (2) |
| C1—N1 | 1.3162 (15) | C5—H5 | 0.9300 |
| C1—N2 | 1.328 (3) | C6—C5ii | 1.371 (2) |
| C2—O1ii | 1.2519 (13) | C6—H6 | 0.9300 |
| C2—C3 | 1.502 (3) | N1—H1A | 0.931 (18) |
| C3—C4 | 1.3846 (17) | N1—H1B | 0.860 (17) |
| C3—C4ii | 1.3846 (17) | N2—H2 | 0.915 (18) |
| C4—C5 | 1.383 (2) | ||
| N1i—C1—N1 | 120.12 (18) | C3—C4—H4 | 119.7 |
| N1i—C1—N2 | 119.94 (9) | C6—C5—C4 | 119.7 (2) |
| N1—C1—N2 | 119.94 (9) | C6—C5—H5 | 120.1 |
| O1ii—C2—O1 | 123.29 (17) | C4—C5—H5 | 120.1 |
| O1ii—C2—C3 | 118.35 (9) | C5ii—C6—C5 | 120.6 (2) |
| O1—C2—C3 | 118.35 (9) | C5ii—C6—H6 | 119.7 |
| C4—C3—C4ii | 118.83 (19) | C5—C6—H6 | 119.7 |
| C4—C3—C2 | 120.58 (10) | C1—N1—H1A | 119.9 (10) |
| C4ii—C3—C2 | 120.59 (10) | C1—N1—H1B | 117.1 (11) |
| C5—C4—C3 | 120.54 (17) | H1A—N1—H1B | 123.0 (15) |
| C5—C4—H4 | 119.7 | C1—N2—H2 | 119.1 (10) |
| Symmetry codes: (i) x, −y+3/2, z; (ii) x, −y+1/2, z. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| N1—H1A···O1iii | 0.931 (18) | 1.902 (19) | 2.8309 (17) | 175.1 (14) |
| N2—H2···O1iv | 0.915 (18) | 2.171 (19) | 2.9700 (10) | 145.4 (14) |
| N1—H1B···O1ii | 0.860 (17) | 2.081 (17) | 2.8816 (17) | 154.7 (15) |
| Symmetry codes: (iii) −x+1/2, y+1/2, z+1/2; (iv) x, y+1, z; (ii) x, −y+1/2, z. |
| O1—C2 | 1.2519 (13) | C1—N2 | 1.328 (3) |
| C1—N1 | 1.3162 (15) | ||
| O1i—C2—O1 | 123.29 (17) |
| Symmetry codes: (i) x, −y+1/2, z. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| N1—H1A···O1ii | 0.931 (18) | 1.902 (19) | 2.8309 (17) | 175.1 (14) |
| N2—H2···O1iii | 0.915 (18) | 2.171 (19) | 2.9700 (10) | 145.4 (14) |
| N1—H1B···O1i | 0.860 (17) | 2.081 (17) | 2.8816 (17) | 154.7 (15) |
| Symmetry codes: (ii) −x+1/2, y+1/2, z+1/2; (iii) x, y+1, z; (i) x, −y+1/2, z. |
This work was supported by Fundação para a Ciência e a Tecnologia (FCT), under project No. POCI/FIS/58309/2004.
Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19.
Bruker (2005). APEX2. Version 2.0-2. Bruker AXS Inc., Madison, Wisconsin, USA.
Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.
Sheldrick, G. M. (2003). SADABS. Version 2.10. University of Göttingen, Germany.
Spek, A. L. (2003). J. Appl. Cryst. 36, 7–13.
Zyss, J., Pecaut, J., Levy, J. P. & Masse, R. (1993). Acta Cryst. B49, 334–342.
Guanidine is a strong base (pKa = 13.5) and readily reacts with all types of organic acids to give salts with good crystallinity, largely because of the presence of six potential donor sites for hydrogen-bonding interactions. From the point of view of their physical properties, guanidine compounds are potentially interesting for non-linear optics applications (Zyss et al., 1993). We are currently engaged in a research project aimed at investigating the structures and dielectric and optical properties of guanidine and guanidine derivative compounds.
Both ions of the title compound, (I) (Fig. 1), possess mirror symmetry, with atoms Cl and N2 of the cation situated in the mirror plane, as well as the carboxylate group C, the ipso-C and the para-C atoms of the anion.
The benzoate anion is almost in a planar conformation, with a dihedral angle of 0.41 (18)° between the phenyl ring and the carboxylate group.
The O—C—O angle of the carboxylate group is greater than 120° because of the steric effect of lone-pair electrons on both O atoms. The bond length in the deprotonated carboxyl group is intermediate between normal single Csp2—O (1.308–1.320 Å) and double Csp2═O bond lengths (1.214–1.224 Å) (Allen et al., 1987), indicating delocalization of the charge over both O atoms of the COO- group.
The three C—N bond lengths in the propeller-shaped CH6N3+ cation are similar (Table 1), the symmetry of the cation being C3 h. The usual model of electron delocalization in this species, leading to a C—N bond order of 1.33, is applicable here.
All H atoms of the guanidinium cation are involved in N—H···O interactions with the anion (Fig. 2, Table 2) forming layers in the bc plane, each carboxylate O atom accepting three H atoms. In each layer, the cation is bonded to three anions, two approximately perpendicular and one approximately coplanar (Fig. 3).