Halogen bonding with the halogenabenzene bird structure, halobenzene, and halocyclopentadiene

The ability of the “bird‐like” halogenabenzene molecule, referred to as X‐bird (XCl to At), to form halogen‐bonded complexes with the nucleophiles H 2 O and NH 3 was investigated using double‐hybrid density functional theory and the aug‐cc‐pVTZ/aug‐cc‐pVTZ‐PP basis set. The structures and interaction energies were compared with 5‐halocyclopenta‐1,3‐diene (halocyclopentadiene; an isomer of halogenabenzene) and halobenzene, also complexed with H 2 O and NH 3 . The unusual structure of the X‐bird, with the halogen bonded to two carbon atoms, results in two distinct σ‐holes, roughly at the extension of the C‐X bonds. Based on the behavior of the interaction energy (which increases for heavier halogens) and van der Waals (vdW) ratio (which decreases for heavier halogens), it is concluded that the X‐bird forms proper halogen bonds with H 2 O and NH 3 . The interaction energies are larger than those of the halogen‐bonded complexes involving halobenzene and halocyclopentadiene, presumably due to the presence of a secondary interaction. © 2019 Wiley Periodicals, Inc.