Weak interionic interactions in 2-bromoimidazolium derivatives

The 2-bromoimidazolium bromide [ImBr]Br (5, Im=2,3-dihydro-1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene) is prepared from Im (4) and bromine. From 4 and CBr4, the adduct [ImBr]Br · CBr4 (6) is obtained. 5 reacts with TeBr4 to give the salt [ImBr][TeBr5] (7). The crystal structures of 5–7 reveal the presence of weak interionic Br to Br interactions which are discussed on comparison with the structure of [ImI]I (8) and similar compounds.