2-Phenylimidazolium acetate

There are two 2-phenylimidazole cations and two acetate anions in the asymmetric unit of the title molecular salt, C9H9N2 +·C2H3O2 −. The dihredral angles between the five- and six-membered rings are 5.50 (2) and 6.90 (2)° in the two molecules. The structure is stabilized by N—H⋯O and weak C—H⋯O hydrogen-bonding interactions between the cations and anions, resulting in chains propagating in [110].

Continuing our research in this important field (Xia et al., 2009), we now report the preparation and crystal structure of the title compound, (I).
There are two 2-phenylimidazole cations and two acetate anions in the asymmetric unit of the title compound (Fig. 1). In the crystal, the cations and anions are linked into chains along [110] by the N-H···O H-bonding interactions (Table 1) thus stabilizing the structure. The structure is further stabilized by rather weak non-classical interactions of the type C-H···O.

Refinement
All H atoms on C and N atoms were positioned geometrically (N-H = 0.86 Å and C-H = 0.93 and 0.96 Å for aryl and methyl H-atoms, respectively) and refined as riding, with U iso (H) = 1.5U eq (methyl-C atoms) and 1.2U eq (the rest of the carrier C/N atoms). Fig. 1. The structure of (I), showing the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger. (2) 162 Symmetry codes: (i) −x, −y+1, −z+1; (ii) −x+1, −y, −z+1; (iii) −x+1/2, y+1/2, −z+3/2.