Disorder in 2-bromoimidazolium hexafluorophosphate salts: the role of halogen bonds

Abstract

X-ray crystallographic analyses of mono- and di-2-bromoimidazolium cations as salts with bromide, hexafluorophosphate, or as double salts of the two, have indicated a tendency for disorder around the imidazolium nitrogen–carbon bond in the absence of the bromide anion as a halogen bond acceptor. Halogen bonding is the primary organising interaction, and the disordered structures show many interactions between the bromo group of 2-bromoimidazolium and fluorine atoms of the hexafluorophosphate anions. Interrogation of bond lengths and angles in the Cambridge Structural Database has revealed a broader tendency for the disorder of 2-haloimidazole and 2-haloimidazolium salts in the absence of strong halogen bonding interactions.