2,6-Dimethylpyridinium bromide

The asymmetric unit of the title salt, C7H10N+·Br−, comprises two 2,6-dimethylpyridinium cations and two bromide anions. One cation and one anion are situated in general positions, while the other cation and the other anion lie on a crystallographic mirror plane parallel to (010). Each pair of ions interact via N—H⋯Br and C—H⋯Br hydrogen bonding, generating motifs depending on the cation and anion involved. Thus, the cation and the anion on the mirror plane generate infinite chains along the c axis, while the other ionic pair leads to sheets parallel to the ac plane. In the overall crystal packing, both motifs alternate along the b axis, with a single layer of the chain motif sandwiched between two double layers of the sheet motif. The sheets and chains are further connected via aryl π–π interactions [centroid–centroid distances = 3.690 (2) and 3.714 (2) Å], giving a three-dimensional network.

The asymmetric unit of the title salt, C 7 H 10 N + ÁBr À , comprises two 2,6-dimethylpyridinium cations and two bromide anions. One cation and one anion are situated in general positions, while the other cation and the other anion lie on a crystallographic mirror plane parallel to (010). Each pair of ions interact via N-HÁ Á ÁBr and C-HÁ Á ÁBr hydrogen bonding, generating motifs depending on the cation and anion involved. Thus, the cation and the anion on the mirror plane generate infinite chains along the c axis, while the other ionic pair leads to sheets parallel to the ac plane. In the overall crystal packing, both motifs alternate along the b axis, with a single layer of the chain motif sandwiched between two double layers of the sheet motif. The sheets and chains are further connected via arylinteractions [centroid-centroid distances = 3.690 (2) and 3.714 (2) Å ], giving a threedimensional network.
The crystal structure of title salt present a supramolecular network, where a complex strong hydrogen-bonding scheme operates between the cations and the anions ( Table 1) with centroids distances of 3.690 Å for A(C g )···B(C g ) and 3.712 Å for A(Cg)···A(C g ) (1 -x, 1 -y, -z), giving a threedimensional network. These separation distances are in accordance with those of calculated and the experimentally observed stacked (offset-face-to-face) interaction modes (Gould et al., 1985, Hunter & Sanders, 1990, Hunter, 1994, Singh & Thornton, 1990

Experimental
In an attempt to crystallize a tetrahalomercurate with the 2,6-dimethylpyridinium cation, the title compound crystallized instead. To a warm solution of 2,6-Dimethylpyridine (1 mmol) and 1 ml 60% HBr dissolved in 95% EtOH (10 ml), a hot solution of HgCl 2 (1 mmol) dissolved in 95% EtOH (10 ml) was added. The resulting mixture was then treated with Br 2 (2-3 ml) and refluxed for 3 hrs. The resulting mixture was left undisturbed to evaporate at room temperature whereupon colorless block crystals are formed after three days.

Refinement
All hydrogen atoms constrained and assigned isotropic thermal parameters of 1.2 times that of the riding atoms (1.5 for methyl). Largest diff. peak and hole were 0.478 and -0.478 e.Å -3 with largest peak 1.035 Å from Br1.

Figure 1
The asymmetric unit of the title compound. Displacement ellipsoids are drawn at the 30% probability level.  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.