Bis(1,3-dimethyl-1H-imidazolium) hexa-fluoro-silicate methanol 0.33-solvate

The title compound, 6C5H9N2 (+)·3SiF6 (2-)·CH3OH, (I), was prepared by recrystallization of the crude salt from methanol along with solvent-free 2C5H9N2 (+)·SiF6 (2-) (II). Crystals of these solvatomorphs can be separated manually. The solvate (I) crystallizes in a rare hexa-gonal space group P6/mcc. Its asymmetric unit comprises one half of an imidazolium cation bis-ected by the crystallographic m-plane, one-sixth and one-twelfth of two crystallographically independent SiF6 (2-) dianions (Si atoms are located on the 3.2 and 6/m inversion centres), and one-twelfth of a methanol mol-ecule (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 SiF6 (2-) 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 inter-linked through SiF6 (2-) dianions disordered around the 6/m centres. The twelvefold disordered methanol mol-ecules are appended to this array by O-H⋯F hydrogen bonds to the 6/m located SiF6 (2-) dianions. In terms of graph-set notation, the first and second level networks in (I) are N 1 = C 2 (2)(7)[3R 4 (4)(14)]D 2 (2)(4) and N 2 = D 2 (2)(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 mol-ecule disordered about the 622 inversion centre.