2-Bromo-1,3-diisopropyl-4,5-dimethyl-1H-imidazol-3-ium dicyanidoargentate

The title structure, (C11H20BrN2)[Ag(CN)2)], is built up from an approximately C 2v-symmetric imidazolium cation and a nearly linear dicyanidoargentate anion [N—Ag—N = 176.6 (9)° and Ag—C—N = 178.8 (9) and 177.2 (11)°]. These two constituents are linked by a remarkably short interaction between the Br atom of the imidazolium cation [C—Br = 1.85 (3) Å] and one N atom of the cyanidoargentate anion [Br⋯N = 2.96 (2) Å], which is much less than the sum of the van der Waals radii (3.40 Å). The crystal studied was twinned by merohedry.

The title structure, (C 11 H 20 BrN 2 )[Ag(CN) 2 )], is built up from an approximately C 2v -symmetric imidazolium cation and a nearly linear dicyanidoargentate anion  and Ag-C-N = 178.8 (9) and 177.2 (11) ]. These two constituents are linked by a remarkably short interaction between the Br atom of the imidazolium cation [C-Br = 1.85 (3) Å ] and one N atom of the cyanidoargentate anion [BrÁ Á ÁN = 2.96 (2) Å ], which is much less than the sum of the van der Waals radii (3.40 Å ). The crystal studied was twinned by merohedry.

Experimental
The title compound was prepared by addition of silver cyanide (1.3 g, 9.7 mmol) to a solution of 2-bromo-1,3-diisopropyl-4,5-dimethylimidazoliumbromide, see: Kuhn et al. (2004), (1.1 g, 3.2 mmol) in 30 ml of acetonitrile. The mixture was stirred for 48 hr at room temperature, then the solvent was removed in vacuo and 20 ml of dichloromethane was added.
The resulting solution was filtered off and solvent was removed in vacuo. Yield after recrystallisation from dichloromethane/diethyl ether 0.98 g (73 %), as colorless crystals.

Refinement
There are no Friedel pairs because only the minimal data set was measured with the CAD4 instrument (±h, +k, +l). Hydrogen atoms were included at calculated positions with C-H = 0.95-1.00 Å and 1.5U eq (aliphatic C), using a riding-model approximation. Fig. 1. The molecular structure the cation-anion pair of the title compound showing 20% probability displacement ellipsoids for non-H atoms. The symmetry transformation for the depicted dicyanoargentate anion is x-1, y, z.

Figures
Crystal data (C 11 H 20  supplementary materials sup-3

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 > 2sigma(F 2 ) is used only for calculating R-factors(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.