Dimethylammonium tetrachloridoferrate(III) 18-crown-6 clathrate

The reaction of dimethylamine hydrochloride, 18-crown-6 and ferric chloride in ethanol yields the title compound, (C2H8N)[FeCl4]·C12H24O6, which exhibits an unusual supramolecular structure. The protonated dimethylamine contains one NH2 + group, resulting in a 1:1 supramolecular rotator–stator structure (CH3—NH2 +—CH3)(18-crown-6), through N—H⋯O hydrogen-bonding interactions between the ammonium group of the cation and the O atoms of the crown ether. In the crystal, all three components lie on a common crystallographic mirror plane normal to [010].

The reaction of dimethylamine hydrochloride, 18-crown-6 and ferric chloride in ethanol yields the title compound, (C 2 H 8 N) [FeCl 4 ]ÁC 12 H 24 O 6 , which exhibits an unusual supramolecular structure. The protonated dimethylamine contains one NH 2 + group, resulting in a 1:1 supramolecular rotatorstator structure (CH 3 -NH 2 + -CH 3 )(18-crown-6), through N-HÁ Á ÁO hydrogen-bonding interactions between the ammonium group of the cation and the O atoms of the crown ether. In the crystal, all three components lie on a common crystallographic mirror plane normal to [010].

Comment
There is currently a great deal of interest in crown ethers because of their ability to form non-covalent, H-bonding complexes with ammonium cations, both in solid and in solution (Akutagawa et al., 2002;Fender et al., 2002). Not only the size of the crown ether, but also the nature of the ammonium cation (NH 4 + , RNH 3 + , R 2 NH 2 + , etc.) can influence on the stoichiometry and stability of these host-guest complexes. The host molecules combine with the guest species by intermolecular interactions, and, if the host molecule contains some specific sites, it is easy to realise high selectivity in ion or molecular recognition. 18-Crown-6 has the highest affinity for ammonium cations RNH 3 + . While most studies of 18-crown-6 and its derivatives invariably showed a 1:1 stoichiometry with RNH 3 + cations, some structurally characterized complexes of crown ethers include R 2 NH 2 + cations.
The present study is a part of systematic investigation of ferroelectric, phase transitions materials (Ye et al., 2009;Zhang et al., 2009) that include metal-organic coordination compounds with organic ligands, or are related to the structures with both organic and inorganic building fragments. In the measured temperature range from 80 to 420 K (m.p. > 430 K), the temperature dependence of the relative permittivity at 1 MHz varied smoothly from 4.6 to 7.2 in the title compound. No dielectric anomaly has been observed. This suggests that this compound is not an actual ferroelectric, or that no distinct phase transition occurred within the probed temperature range.  supplementary materials sup-2 Experimental CH 3 -NH-CH 3 .HCl (2 mmol, 0.163 g) and 18-crown-6 (2 mmol, 0.528 g) were dissolved in ethanol. Then, trivalent ferric chloride (2 mmol, 0.54 g) was added to the mixture in concentrated hydrochloric acid medium, the precipitate was filtered and washed with a small amount of ethanol. Five days later, single crystals suitable for X-ray diffraction analysis were obtained from slow evaporation of ethanol and DMF solution at room temperature.

Refinement
All C-bonded H atoms were calculated geometrically with C-H distances fixed to 0.96 Å, and were allowed to ride on the C atoms to which they are bonded, with U iso (H) = 1.2U eq (C) or U iso (H) = 1.5U eq (C) (methyl groups). The ammonium H atom (H1C) was calculated geometrically and refined using a riding model with N-H = 0.90 Å and U iso (H) = 1.2U eq (N). Fig. 1. The title compound, with the atomic numbering scheme. The displacement ellipsoids are drawn at the 30% probability level. Dimethylammonium tetrachloridoferrate(III)-1,4,7,10,13,16-hexaoxacyclooctadecane (1/1)

Figures
Crystal data (C 2