7. Crystal structure of tetrabutylammonium bromide–1,2-diiodo-3,4,5,6-tetrafluorobenzene–dichloromethane (2/2/1)
   Viger-Gravel, J.; Korobkov, I.; Bryce, D. L.
   Acta Crystallogr., Sect. E: Crystallogr. Commun. 2015, 71, o286-o287

The crystallization of a 1:1 molar solution of 1,2-di­iodo-3,4,5,6-tetra­fluoro­benzene (o-DITFB) and tetra­butyl­ammonium bromide (n-Bu₄NBr) from di­chloro­methane yielded pure white crystals of a halogen-bonded compound, C₁₆H₃₆N⁺·Br^-·C₆F₄I₂·0.5CH₂Cl₂ or [(n-Bu₄NBr)(o-DITFB)]·0.5CH₂Cl₂. The compound may be described as a quaternary system and may be classified as a salt-cocrystal solvate. The asymmetric unit contains one mol­ecule of solvent, two o-DITFB mol­ecules, two cations (n-Bu₄N⁺) and two crystallographically distinct bromide ions [_IBr-I = 144.18 (1) and 135.35 (1)°]. The bromide ion is a bidentate halogen-bond acceptor which inter­acts with two covalently bonded iodines (i.e. halogen-bond donors), resulting in a one-dimensional polymeric zigzag chain network approximately along the a axis. The observed short contacts and angles are characteristic of the non-covalent inter­action [d_C-IBr = 3.1593 (4)-3.2590 (5) Å; _C-IBr = 174.89 (7) and 178.16 (7)°]. It is noted that iodine acts as both a halogen-bond donor and a weak CH hydrogen-bond acceptor, while the bromide ions act as acceptors for weak CH hydrogen bonds and halogen bonds.

DOI : 10.1107/S2056989015006593