N,N,2,4,6-Penta-methyl-anilinium hexa-fluoro-phosphate.

In the crystal structure of the title salt, C11H18N(+)·PF6(-), the cation and anion are connected via an N-H⋯F hydrogen bond; weak C-H⋯F hydrogen bonding also occurs between the cations and anions.

In the crystal structure of the title salt, C 11 H 18 N + ÁPF 6 À , the cation and anion are connected via an N-HÁ Á ÁF hydrogen bond; weak C-HÁ Á ÁF hydrogen bonding also occurs between the cations and anions.  Table 1 Hydrogen-bond geometry (Å , ). At present, much attention in ferroelectric material field is focused on developing ferroelectric pure organic or inorganic compounds (Haertling et al. 1999;Homes et al. 2001). In order to find more dielectric ferroelectric materials, we investigate the physical properties of the title compound (Fig. 1). The dielectric constant of the title compound as a function of temperature indicates that the permittivity is basically temperature-independent (dielectric constant equaling to 3.7 to 5.2), suggesting that this compound should be not a real ferroelectrics or there may be no distinct phase transition occurred within the measured temperature range. Similarly, below the melting point (453 K) of the compound, the dielectric constant as a function of temperature also goes smoothly, and there is no dielectric anomaly observed (dielectric constant equaling to 3.7 to 5.2). Herein, we report the synthesis and crystal structure of the title compound.

D-HÁ
Molecules of the title compound have normal geometric parameters. The bond lengths and angles are within their normal ranges. In the crystal, the cation and anion are connected via N-H···F and weak C-H···F hydrogen bonds (Table   1).

Experimental
A mix of N,N,2,4,6-pentamethylbenzenamine (1.36 g, 0.01 mol) and hexafluorophosphoric acid (1.90 g, 0.01 mol) in methanol (20 ml) was stirred until clear. After several days, the title compound was formed and recrystallized from methanol solution to afford colourless prismatic crystals suitable for X-ray analysis.

Refinement
H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93-0.96 and N-H = 0.91 Å and U iso (H) = 1.2 eq (C,N).  Perspective structure of the title compound, showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.

Figure 2
The crystal packing of the title compound viewed along theb axis showing the hydrogen bondings network.  where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max = 0.001 Δρ max = 0.21 e Å −3 Δρ min = −0.27 e Å −3 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 > 2sigma(F 2 ) is used only for calculating R-factors(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.