Secondary interactions in the isomorphous compounds 2,6-bis(chloromethyl)pyridinium chloride and 2,6-bis(bromomethyl)pyridinium bromide.

The title compounds, C 7 H 8 Cl 2 N + .Cl - and C 7 H 8 Br 2 N + .Br - , are isomorphous. In the crystal packing, layers parallel to the ac plane are formed by a classical N + -H...X - hydrogen bond (X = halogen) and two X...X contacts. A third X...X contact links the layers, and a fourth, which is however very long, completes a ladder-like motif of halogen atoms. Hydrogen bonds of the form C-H...X play at best a subordinate role in the packing.