3,3-Dimethyl-1,1-(propane-1,3-diyl)diimidazol-1-ium tetrabromidocadmate(II)

The title compound, (C11H18N4)[CdBr4], was prepared by an anion exchange. The dihedral angle between the two planar imidazolium rings in the cation is 74.4 (4)°. The crystal packing is stabilized by weak intermolecular C—H⋯Br hydrogen bonds between the cation and the tetrahedral anion, building up a three-dimensionnal network.

The title compound, (C 11 H 18 N 4 ) [CdBr 4 ], was prepared by an anion exchange. The dihedral angle between the two planar imidazolium rings in the cation is 74.4 (4) . The crystal packing is stabilized by weak intermolecular C-HÁ Á ÁBr hydrogen bonds between the cation and the tetrahedral anion, building up a three-dimensionnal network.  Liang et al. (2008). For bond-length data, see: Allen et al. (1987).

Comment
Ionic liquids (ILs) are generally formed by an organic cation and a weakly coordinating anion. They have enjoyed considerable research interests in recent years because of their unique properties such as high thermal stability, non-volatility, non-flammability, high ionic conductivity, wide electrochemical window and miscibility with organic compounds (Welton, 1999;Nicholas et al., 2004;Yu et al., 2007). Geminal dicationic ionic liquids have been shown to possess superior physical properties in terms of thermal stability and volatility compared to traditional ionic liquids (ILs) (Jared et al., 2005;Liang et al., 2008;Song et al., 2009). As part of our ongoing studies on new Geminal dicationic ionic liquids (Geng et al., 2010), we report here the crystal structure of the title compound (I).
Crystals of (I) suitable for X-ray diffraction were obtained by slow evaporation of methanol. or 0.93 Å (aromatic) with U iso (H) = 1.2U eq (C) or U iso (H) = 1.5U eq (Cmethyl). Fig. 1. A view of the molecular structure of (I) showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. Hydrogen are represented as small spheres of arbitrary radii. Hydrogen bond is shown as dashed line.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.