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Acta Cryst. (2013). E69, o1216-o1217  [ doi:10.1107/S1600536813018230 ]

Bis(1,3-dimethyl-1H-imidazolium) hexafluorosilicate methanol 0.33-solvate

C. Tian, W. Nie and M. V. Borzov

Abstract: The title compound, 6C5H9N2+·3SiF62-·CH3OH, (I), was prepared by recrystallization of the crude salt from methanol along with solvent-free 2C5H9N2+·SiF62- (II). Crystals of these solvatomorphs can be separated manually. The solvate (I) crystallizes in a rare hexagonal space group P6/mcc. Its asymmetric unit comprises one half of an imidazolium cation bisected by the crystallographic m-plane, one-sixth and one-twelfth of two crystallographically independent SiF62- dianions (Si atoms are located on the 3.2 and 6/m inversion centres), and one-twelfth of a methanol molecule (C atoms are situated on the 622 inversion centres, other atoms are disordered between general positions). In (I), all F atoms of 3.2-located SiF62- dianions participate in the formation of symmetry-equivalent contacts to the H atoms of imidazolium fragments, thus forming rod-type ensembles positioned on the -6 axes. These `pillar' rods are, in turn, F...H interlinked through SiF62- dianions disordered around the 6/m centres. The twelvefold disordered methanol molecules are appended to this array by O-H...F hydrogen bonds to the 6/m located SiF62- dianions. In terms of graph-set notation, the first and second level networks in (I) are N1 = C22(7)[3R44(14)]D22(4) and N2 = D22(5) (C-H...O hydrogen bonds are not considered). After locating all symmetrically independent atoms in the cation and anions, there remained a strong (> 3 e Å-3) residual electron density peak located at the 622 inversion centre. Treatment of this pre-refined model with the SQUEEZE procedure in PLATON [Spek (2009). Acta Cryst. D65, 148-155] revealed two voids per unit cell, indicative of the presence of the solvent methanol molecule disordered about the 622 inversion centre.

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