Halogen Bonding Interactions of <i>sym</i>-Triiodotrifluorobenzene with Halide Anions: A Combined Structural and Theoretical Study

Cocrystallization of 1,3,5-trifluoro-2,4,6-triiodobenzene (sym-TFTIB) with nBu4NX or Ph4PX (X = Cl−, Br−) afforded the 1:1 complex salts formulated as (sym-TFTIB)(nBu4NCl), (sym-TFTIB)(nBu4NBr), (sym-TFTIB)(Ph4PCl)(H2O)0.5 or (sym-TFTIB)(Ph4PBr). In all four salts, each halide anion is halogen bonded to three iodine atoms from three different sym-TFTIB molecules, affording a recurrent polymeric two-dimensional anionic network, characterized by short I···X distances and linear C−I···X but acute I···X−···I angles (X− = Cl−, Br−). Topological analysis of the electron localization function (ELF) shows a perfect match between the iodine valence shell electrons, with a “belt”-shape arrangement around the C−I axis, and the spherical halide anions. The lack of covalent character for the halogen bond allows the simultaneous participation of one X− anion in three halogen bonds.