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

Abstract

Cocrystallization of 1,3,5-trifluoro-2,4,6-triiodobenzene ( sym -TFTIB) with n Bu 4 NX or Ph 4 PX (X = Cl −, Br − ) afforded the 1:1 complex salts formulated as ( sym -TFTIB)( n Bu 4 NCl), ( sym -TFTIB)( n Bu 4 NBr), ( sym -TFTIB)(Ph 4 PCl)(H 2 O) 0.5 or ( sym -TFTIB)(Ph 4 PBr). 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.