Crystal structure of tetrabutylammonium bromide–1,2-diiodo-3,4,5,6-tetrafluorobenzene–dichloromethane (2/2/1)

Abstract

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 [θI...Br-...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 [dC—I...Br = 3.1593 (4)–3.2590 (5) Å; θC—I...Br = 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.

Keywords

• crystal structure
• halogen bonds
• short contacts
• noncovalent interaction