Bis(4-fluoroanilinium) tetrachloridocuprate(II)

The crystal structure of the title compound, (C6H7FN)2[CuCl4], consists of parallel two-dimensional perovskite-type layers of corner-sharing CuCl6 octahedra. These are bonded together via N—H⋯Cl hydrogen bonds from the 4-fluoroanilinium chains, which are almost perpendicular to the layers. The CuCl4 dianions have two short Cu—Cl bonds [2.2657 (15) and 2.2884 (13) Å] and two longer bonds [2.8868 (15) Å], giving highly Jahn–Teller-distorted CuCl6 octahedra. The Cu atoms are situated on crystallographic centers of inversion.


Bis(4-fluoroanilinium) tetrachloridocuprate(II)
M. M. Zhao and P. P. Shi Comment Copper(II) halides occur in a variety of geometrical conformations including tetrahedral, square-pyramidal, square-bipyramidal, square-planar and trigonal-bipyramidal (Bhattacharya et al., 2004;Yuan et al., 2004). The perovskite-layer copper chlorides have attracted a great deal of attention due to their magnetic properties and interesting structural phase transitions.
This study is a part of our systematic investigation of dielectric ferroelectric, phase transitions materials (Ye et al., 2009;Zhang et al., 2009), including organic ligands, metal-organic coordination compounds and organic inorganic hybrid compounds. Below the melting point (m.p. 440 K) of the 4-fluoroanilinium tetrachlorocuprate, the dielectric constant as a function of temperature also goes smoothly, and there is no dielectric anomaly observed (dielectric constant equaling to 6 to 11).
The asymmetric unit of the title compound is composed of a (C 6 H 7 FN + ) cation and one half of the anionic (CuCl the in-plane Cl2 atom of the next CuCl 4 2ion is approximately 2.9 Å and is significantly longer than the distances in the CuCl 4 2square due to the Jahn-Teller effect. The Cu atom is situated on a crystallographic center of inversion. In the bc plane, Cu atoms and Cl2 atoms form a puckered plane and the Cu-Cl3 bond is nearly perpendicular to this plane. The organic chains are arranged between the layers. NH 3 + groups fit into cavities of the CuCl 4 2layer and N-H···Cl hydrogen bonds bind the organic chains (Fig. 2). Details of the hydrogen-bonding geometry are given in Table 1.

Experimental
An excess of hydrogen chloride was slowly added to 20 ml of an ethanolic solution of 4-fluoroaniline (222 mg, 0.002 mol). Then copper dichloride dihydrate (170 mg, 0.001 mol) was added to the mixture. After several days, the title salt, , was formed and recrystallized from an ethanolic solution at room temperature to afford green prismatic crystals suitable for X-ray analysis.
Dielectric studies (capacitance and dielectric loss measurements) were performed on powder samples which have been pressed into tablets on the surfaces of which a conducting carbon glue was deposited. The automatic impedance TongHui2828 Analyzer has been used. In the measured temperature ranges (80 K to 430 K), the title structure showed no dielectric anomaly.
supplementary materials sup-2 Refinement All C-H hydrogen atoms were calculated geometrically and were refined using a riding model with C-H distances ranging from 0.93 to 0.97 Å and U iso (H) = 1.2 U eq (C). Hydrogen positions at nitrogen were also calculated geometrically and included into the refinement with N-H = 0.89 Å and U iso (H) = 1.5 U eq (N).
Figures Fig. 1. The molecular structure of one cation and one anion of the title compound, with 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.