Experimental

R factor = 0.040; wR factor = 0.096; data-to-parameter ratio = 24.2. In the title salt, C6H9N2 +Br2I, the cation is essentially planar (r.m.s. deviation = 0.0062 A ̊ for the non-H atoms) while the anion is almost linear with a Br—I—Br angle of 177.67 (2). The crystal packing shows two anions and two cations connected via N—H Br and (pyridine)N—H Br hydrogen-bonding interactions, forming centrosymmetric tetramers with R4 4(16) ring motifs. Very weak offset aromatic – stacking interactions [centroid-centroid separation = 4.038 (4), slippage = 1.773 Å] also occur. Related literature For background to this study, see: Al-Far et al. (2012); Kochel (2006). For comparison bond lengths and angles, see: Gard-berg et al. (2002); Hemamalini & Fun (2010). For graph-set notation, see: Bernstein et al. (1995)