3,3′-Dimethyl-1,1′-(butane-1,4-diyl)diimidazolium bis(tetrafluoroborate)

The title compound, C12H20N42+center dot 2BF(4)(-), was prepared by the anion exchange of a dibromide ionic liquid with sodium tetrafluoroborate. The asymmetric unit contains one half of the imidazolium cation, which lies about an inversion centre at the mid-point of the central C-C bond of the linking butyl chain. The two planar imidazole rings (r.m.s. deviation = 0.0013 angstrom) are strictly parallel and separated by 2.625 (7) angstrom [vertical distance between the centroids of two imidazole rings], giving the molecule a stepped appearance. In the crystal structure, intermolecular C-H center dot center dot center dot F hydrogen bonds link the cations and anions, generating a three-dimensional network.