2-Cyanoanilinium bromide

In the cation of the title compound, C7H7N2 +·Br−, the nitrile group and the benzene ring are almost coplanar (r.m.s. deviation = 0.0043 Å). In the crystal, the cations and anions are connected by intermolecular N—H⋯Br hydrogen bonds, forming a two-dimensional network parallel to (010).

In the cation of the title compound, C 7 H 7 N 2 + ÁBr À , the nitrile group and the benzene ring are almost coplanar (r.m.s. deviation = 0.0043 Å ). In the crystal, the cations and anions are connected by intermolecular N-HÁ Á ÁBr hydrogen bonds, forming a two-dimensional network parallel to (010).

Comment
The construction of metal-organic coordination compounds has attracted much attention owing to potential functions, such as permittivity, fluorescence, magnetism and optical properties (Fu et al., 2007;Chen et al., 2000;Xie et al., 2003;Zhang et al., 2001;Xiong et al., 1999). Nitrile derivatives are a class of excellent ligands for the construction of novel metal-organic frameworks (Wang et al., 2002;. We report here the crystal structure of the title compound. In the 2-cyanoanilinium cation ( Fig.1), the nitrile group and the benzene ring are almost coplanar. The nitrile group C7≡N2 bond length of 1.142 (4) Å is within the normal range.
In the crystal structure, all the amine group H atoms are involved in N-H···Br hydrogen bonds (Table 1) with Branions.
These hydrogen bonds along with N-H···Br hydrogen bonds link the ionic units into a two-dimensional network (Fig. 2) parallel to the (0 1 0) plane.

Experimental
The commercial 2-aminobenzonitrile (3 mmol, 0.55 g) and HBr (0.5 ml) were dissolved in ethanol (20 ml). Colourless needle-shaped crystals of the title compound suitable for X-ray analysis were obtained by slow evaporation at room temperature.

Refinement
All H atoms attached to C and N atoms were positioned geometrically and treated as riding, with C-H = 0.93 Å, N-H = 0.89 Å and U iso (H) = 1.2U eq (C) and U iso (H) = 1.5U eq (N). A rotating-group model was used for the -NH 3 group.

Special details
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 F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.