1,3-Bis(2,4,6-trimethylphenyl)imidazolium perchlorate

The title compound, C21H25N2+·ClO4-, arose as an unexpected oxidation product of the carbene 1,3-bis(2,4,6-trimethylphenyl)-1,3-dihydro-2H-imidazol-2-ylidine in methanol. It crystallizes with two unique cations and anions in the P-type monoclinic unit cell. The five-membered cationic imidazolium rings are essentially planar and in each imidazolium cation the phenyl rings of the 2,4,6-trimethylphenyl groups are staggered with respect to the imidazolium ring [dihedral angles ranging from 60.9(3) to 86.3(3)°]. In the crystal, a hydrogen-bonding network is created via C - H⋯O interactions between the imidazolium ring H atoms and the perchlorate-anion oxygen atoms. The crystal studied was refined as an inversion twin.