Imidazolium-based ionic liquid salts: 3,3′-dimethyl-1,1′-(1,4- phenylenedimethylene)diimidazolium bis-(tetra-fluoro-borate) and 3,3′-di-n-butyl-1,1′-(1,4-phenylenedimethylene)diimidazolium bis-(trifluoromethanesulfonate)

Abstract

Crystallization of the ionic liquid 3,3′-dimethyl-1,1′-(1,4- phenyl-enedimethyl-ene)diimidazolium bis-(tetra-fluoro-borate), C16H20N4 2+·2BF4 -, (I), from its solution in water has permitted the first single-crystal study of an imidazolium-based ionic liquid having a tetra-fluoro-borate ion as counter-ion. Despite the expecta-tion that the anion would not participate in nonclassical hydrogen bonding, the ionic liquid features C - H⋯F hydrogen bonds. The dication lies about a center of inversion. The ionic liquid 3,3′-di-n-butyl-1,1′-(1,4-phenyl- enedimethyl-ene)diimidazolium bis-(trifluoro-methane-sulfonate), C 22H32N42+·2CF3SO3 -, (II), features both C - H⋯F and C - H⋯O hydrogen bonds. © 2008 International Union of Crystallography.