4,5-Dibromo-1,2-dimethyl-1H-imidazol-3-ium bromide

In the title salt, C5H7Br2N2 +·Br−, the cation and anion are connected by an N—H⋯Br hydrogen bond. In the crystal, there are intercalated layers parallel to (10-2) in which bromide ions are located between the cations. Weak intermolecular C—H⋯Br hydrogen bonds are also observed.

In the title salt, C 5 H 7 Br 2 N 2 + ÁBr À , the cation and anion are connected by an N-HÁ Á ÁBr hydrogen bond. In the crystal, there are intercalated layers parallel to (102) in which bromide ions are located between the cations. Weak intermolecular C-HÁ Á ÁBr hydrogen bonds are also observed.
We are grateful to all personel of the PHYSYNOR Laboratory, Université Mentouri-Constantine, Algeria, for their assistance. Thanks are due to the MESRS (Ministé re de l'Enseignement Supé rieur et de la Recherche Scientifique -Algé rie) for financial support. Imidazole is an important synthon for the synthesis of diverse derivatives and various condensed heterocycles. The C,Nsubstituted haloimidazole derivatives have shown a high pharmacological activity (Zamora et al., 2003;Schmidt et al., 2003) and some have found practical use in medicine (Mashkovskii, 2005;Amini et al., 2007;Reepmeyer et al., 1975).
Halo-and dihaloimidazoles form salts with mineral acids and picrates. The nitrates and picrates, which crystallize readily from water and alcohols, are quite often used for the additional characterization of compounds being studied. In this paper, we report the structure determination of 4,5-dibromo-1,2-dimethyl-1H-imidazolium bromide (I) resulting from an unexpected reaction of 1,2-dimethyl-1H-imidazole with bromine in acetone in a modified Ortoleva-King conditions reaction (King, 1944).
The crystal packing can be described as intercalated layers parallel to (102) in which bromide ions are located between cations (Fig. 2). Further stabilization is provided by weak intermoleculer C-H···Br hydrogen bonds (Fig. 3).

Experimental
Compound (I) was obtained from reaction of 4,5-dibromo-1,2-dimethyl-1H-imidazole dissolved in acetone with 1 eq. of bromine. After stirring at 303K during 1 h, a colorless suspension was obtained and a white solid was filtered off. A suitable crystal was obtained by slow evaporation at room temperature of a solution of (I) in a MeOH/CHCl 3 mixture.

Refinement
H atoms were located in difference Fourier maps but introduced in calculated positions and treated as riding on their parent C or N atom (with C-H = 0.96 Å, N-H = 0.88 Å and U iso (H) = 1.5U eq (C) or 1.2U eq (N).

Special details
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 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 > σ(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.