The crystal structures of 1-(4-bromo-2,3,5,6-tetrafluorophenyl)-3-benzyl-methylimidazolium bromides

Abstract

The crystal structures of 1-(4-bromo-2,3,5,6-tetrafluorophenyl)-2-methyl-3-benzylimidazolium bromide (8) and 1-(4-bromo-2,3,5,6-tetrafluorophenyl)-3-benzyl-4-methylimidazolium bromide (9) have been determined by single crystal X-ray diffraction. Both crystal structures possess C(2)─H•••Brhydrogen bonding and C─Br•••Brhalogen bonding. That of 8 also contains π-π stacking between bromotetrafluorophenyl and phenyl rings, and that of 9 also contains C(1)─H•••Brhydrogen bonding and anion- interactions. The crystal structure of 9 is similar to that of the non-methylated salt, 1-(4-bromo-2,3,5,6-tetrafluorophenyl)-3-benzylimidazolium bromide (4), with columns of alternating parallel bromotetrafluorophenyl rings and bromide.

The Influence of the Halide in the Crystal Structures of 1-(2,3,5,6-Tetrafluoro-4-pyridyl)-3-benzylimidazolium Halides

“…The crystal structures of 1-polyfluoroaryl-3-benzylimidazolium bromide salts [ 1 , 2 , 3 , 4 , 5 , 6 ] have proved useful for studying a number of non-covalent interactions with importance in crystal engineering: charge-assisted hydrogen bonding [ 7 , 8 ], π–π stacking between polyfluoroaryl and aryl rings [ 9 ], lone pair–π interactions [ 10 ] and C–X∙∙∙Br − halogen bonding [ 11 ]. It is evident from these studies that a number of interactions are common to all the crystal structures, but also that the nature of the cation has a large impact on which interactions control the crystal structure.…”

The crystal structures of 1-(polyfluorophenylmethyl)-3-methylimidazolium bromide salts

“…The majority of crystal structures of fluoroaryl-substituted imidazolium bromide salts possess a N 2 C─HꞏꞏꞏBrhydrogen bond [2,3,[9][10][11], unless this position is blocked, as is the case for 2-methyl substituted imidazolium cations [12]. Typically this charge-assisted hydrogen bonding is the strongest inter-ion interaction [3,8,[11][12][13]. Most structures also possess weaker C─HꞏꞏꞏBrhydrogen bonding involving one or both of the other hydrogen atoms of the imidazolium ring.…”