3,3'-Dimethyl-1,1'-(methyl-enedi-p-phenyl-ene)diimidazolium bis-(hexa-fluoro-phosphate)

The title N-heterocyclic carbene compound, C(21)H(22)N(4) (2+)·2PF(6) (-), crystallizes as an inversion twin. There are two independent N-heterocyclic carbene dications (A and B) and four independent hexa-fluoro-phosphate anions in the asymmetric unit. The cations are L-shaped with the benzene rings being inclined to one another by 88.82 (16)° in cation A and 87.03 (16)° in cation B. The imidazole rings make dihedral angles of 35.7 (2) and 32.83 (18)° with the attached benzene rings in cation A, and 30.14 (19) and 31.96 (18)° in cation B. In the crystal, the cations are linked via C-H⋯F hydrogen bonds, forming a three-dimensional network. π-π inter-actions involving the benzene and imidazole rings [centroid-centroid distances = 3.602 (2) and 3.723 (2) Å] and C-H⋯π inter-actions are also present.