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

The title compound, 6C(5)H(9)N(2) (+)·3SiF(6) (2−)·CH(3)OH, (I), was prepared by recrystallization of the crude salt from methanol along with solvent-free 2C(5)H(9)N(2) (+)·SiF(6) (2−) (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 SiF(6) (2–) 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 SiF(6) (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 inter­linked through SiF(6) (2–) 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 SiF(6) (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 mol­ecule disordered about the 622 inversion centre.