Octakis(3-methylanilinium) hexachloridocadmate tetrachloride

The asymmetric unit of the title compound, (C7H10N)8[CdCl6]Cl4, contains four 3-methylanilinium cations, two chloride anions and half an octahedral hexachloridocadmate(II) anion, which lies on an inversion centre. In the crystal, numerous N—H⋯Cl and bifurcated N—H⋯(Cl,Cl) hydrogen bonds link the components.


Comment
Recently much attention has been devoted to simple molecular-ionic compounds containing inorganic and organic ions due to the tunability of their special structural features and their potential ferroelectrics property. Ferroelectric materials that exhibit reversible electric polarization in response to an external electric field have found many applications such as nonvolatile memory storage, electronics and optics. The freezing of a certain functional group at low temperature forces significant orientational motions of the guest molecules and thus induces the formation of the ferroelectric phase. (Zhang et al. 2009;Ye et al. 2009;Zhang et al. 2010.). In our laboratory, the title compound, (I), has been synthesized and its crystal structure is herein reported.
The title compound, [(C 7 H 10 N) 8 CdCl 6 ]Cl 4 , has an asymmertic unit that consists of four 3-methylanilinium cations, two chloride anions and one hexachloridocadmiumate anion (Fig 1), which lies in a symmetrical center. The non-hydrogen atoms of C 7 H 10 N cations are nearly coplanar, the cadmium atom is coordinated by six chloride ions, forming a distorted octahedron, the average Cd-Cl bond distances range from 2.5425 (12) Å to 2.6760 (15) Å, the Cl-Cd-Cl angles range from 88.87 (5)°to 180°.The existence of N-H···Cl hydrogen-bonding interactions makes great contribution to the stability of the crystal structure (Fig 2).

Experimental
3.21 g (0.03 mol) of 3-methylbenzenamine was firstly dissolved in 30 ml ethanol, to which 1.1 g (0.03 mol) of hydrochloric acid was then added to afford the solution, then the 0.83 g (0.01 mol) cadmium chloride was dissolved in 20 ml e thanol which was added hydrochloric acid, at last, mixed the above solution without any precipitation under stirring at the ambient temperature. Single crystals suitable for X-ray structure analysis were obtained by the slow evaporation of the above solution after 4 days in air.
The dielectric constant of the compound as a function of temperature indicates that the permittivity is basically temperature-independent (ε = C/(T-T 0 )), suggesting that this compound is not ferroelectric or there may be no distinct phase transition occurring within the measured temperature within the measured temperature (below the melting point).

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.