5-(4-Fluorophenyl)-2H-pyrazol-1-ium 2,2,2-trifluoroacetate

The title salt, C9H8FN2 +·C2F3O2 −, crystallizes with two independent cations (A and B) and two independent anions (C and D) in the asymmetric unit. In the cations, the dihedral angles between the benzene and pyrazolium rings are 23.7 (3)° in cation A and 1.8 (8)° in cation B. In the crystal, each anion links to the two cations via N—H⋯O hydrogen bonds, forming a U-shaped unit with an R 4 4(14) ring motif. These U-shaped units stack along the a axis and are linked via C—H⋯O and C—H⋯F hydrogen bonds, forming slabs lying parallel to (100). Within the slabs there are π–π interactions between the pyrazolium rings [inter-centroid distance = 3.6326 (15) Å] and between the benzene rings [inter-centroid distance = 3.7244 (16) Å]. In the anions, the F atoms of the trifluoromethyl groups are disordered over two sets of sites, with refined occupancy ratios of 0.58 (3):0.42, 0.540 (14):0.46 (14), and 0.55 (2):0.45 (2) for anion C, and 0.73 (5):0.27 (5), 0.63 (5):0.37 (5), and 0.57 (8):0.43 (8) for anion D.

The title salt, C 9 H 8 FN 2 + ÁC 2 F 3 O 2 À , crystallizes with two independent cations (A and B) and two independent anions (C and D) in the asymmetric unit. In the cations, the dihedral angles between the benzene and pyrazolium rings are 23.7 (3) in cation A and 1.8 (8) in cation B. In the crystal, each anion links to the two cations via N-HÁ Á ÁO hydrogen bonds, forming a U-shaped unit with an R 4 4 (14) ring motif. These Ushaped units stack along the a axis and are linked via C-HÁ Á ÁO and C-HÁ Á ÁF hydrogen bonds, forming slabs lying parallel to (100). Within the slabs there areinteractions between the pyrazolium rings [inter-centroid distance = 3.6326 (15) Å ] and between the benzene rings [inter-centroid distance = 3.7244 (16) Å ]. In the anions, the F atoms of the trifluoromethyl groups are disordered over two sets of sites, with refined occupancy ratios of 0.58 (3)
The title salt crystallizes with two independent cations (A and B) and two independent anions (C and D) in the asymmetric unit (Fig 1). In the cations, the dihedral angles between the benzene and pyrazolium rings is 23.7 (3)° in cation A and 1.8 (8)° in cation B. The bond lengths are in normal ranges (Allen et al., 1987).

Experimental
3-(4-Fluoro-phenyl)-1H-pyrazole (0.2 g, 3.0833 mmol; Sigma-Aldrich) was dissolved in a mixture of trifluoroacetic and methanol (1:3 v/v) and stirred for 10 minutes at 313 K. The resulting solution was allowed to cool slowly at room temperature, yielding colourless block-like crystals of the title compound after a few days (M.p: 353-358 K).

Refinement
The NH H atoms were located in a difference Fourier map and freely refined. The C-bound H atoms were placed in calculated positions and refined using a riding model: C-H = 0.93 and 0.97Å for CH and CH 2 H atoms, respectively, with U iso (H) = 1.2U eq (C). In the anions, disorder was modeled for the fluorine atoms of the trifluoromethyl groups over two sets of sites with occupancy ratios of 0.58 (3)  A view of the molecular structure of the title salt, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level.

Figure 2
A view along the a axis of the crystal packing of the title compound. The N-H···O, C-H···F and C-H···O hydrogen bonds are shown as dashed lines (see Table 1   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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (