1-Benzylimidazolium hexafluorophosphate–1-benzylimidazole (1/1)

In the title compound, C10H11N2 +·PF6 −·C10H10N2, the H atom involved in protonation is disordered equally between the cation and the neutral molecule. The dihedral angle between the phenyl and imidazole rings is 82.6 (2)°. In the crystal structure, there are head-to-tail π–π stacking interactions between imidazole rings; the interplanar separation is 3.295 (1) Å and the centroid–centroid separation is 3.448 (3) Å. In the centrosymmetric anion, two F atoms are disordered over two positions; the refined site-occupancy factors are 0.855 (11) and 0.145 (11).

In the title compound, C 10 H 11 N 2 + ÁPF 6 À ÁC 10 H 10 N 2 , the H atom involved in protonation is disordered equally between the cation and the neutral molecule. The dihedral angle between the phenyl and imidazole rings is 82.6 (2) . In the crystal structure, there are head-to-tailstacking interactions between imidazole rings; the interplanar separation is 3.295 (1) Å and the centroid-centroid separation is 3.448 (3) Å . In the centrosymmetric anion, two F atoms are disordered over two positions; the refined site-occupancy factors are 0.855 (11) and 0.145 (11).
In the crystal structure of the title compound (Fig. 2), there are head-to-tail π-π stacking interactions between imidazole rings; the interplanar separation is 3.295 (1) Å and the centroid-to-centroid separation is 3.448 (3) Å.

Experimental
A 1,4-dioxane solution (20 ml) of imidazole (1.420 g, 20.8 mmol) was added to a suspension of oil-free sodium hydride (0.500 g, 20.8 mmol) in 1,4-dioxane (20 ml) and stirred for 1 h at 90°C. A 1,4-dioxane (20 ml) solution of benzyl bromide (3.240 g, 19 mmol) was then added dropwise to the above solution. The mixture was stirred for 22 h at 90°C, and a brown solution was obtained. The solvent was removed with a rotary evaporator and H 2 O (50 ml) was added to the residue. The solution was then extracted with CH 2 Cl 2 (50 ml), and the solution was dried with anhydrous MgSO 4 . After removing CH 2 Cl 2 , 1-benzylimidazole, as a pale yellow liquid was obtained yield: 2.7 g (89.7%).
supplementary materials sup-2 Refinement All H atoms were initially located in a difference Fourier map. They were then placed in geometrically idealized positions and constrained to ride on their parent atoms, with Csp 3 -H = 0.97 Å, Csp 2 -H = 0.93 Å and N-H = 0.86 Å and U iso (H) = 1.2U eq (C,N). In the centrosymmetric anion, atoms F2 and F3 are disordered over two positions; the refined site occupancy factors are 0.855 (11) and 0.145 (11). Atom H2 is disordered equally between the cation and the neutral molecule.

Figures
Fig . 1. Perspective view of the title compound, with displacement ellipsoids drawn at the 30% probability level. The organic moiety with A atom labels is the cation; that with B atom labels is the centrosymmetrically related neutral molecule. In the centrosymmetric anion, only one disorder component is shown. Fig. 2. The π-π stacking interaction between imidazole rings in the title compound.