Bis(2-trifluoro­methyl-1H-benzimidazol-3-ium) tetra­chloridomercurate dihydrate

Ming-Liang Liu

doi:10.1107/S1600536812018855

. 2012 May 2;68(Pt 6):m716. doi: 10.1107/S1600536812018855

Bis(2-trifluoromethyl-1H-benzimidazol-3-ium) tetrachloridomercurate dihydrate

Ming-Liang Liu ^a,^*

PMCID: PMC3379063 PMID: 22719284

Abstract

In the title compound, (C₈H₆F₃N₂)₂[HgCl₄]·2H₂O, the Hg^II cation is coordinated by four Cl⁻ anions in a distorted tetrahedral geometry. In the crystal, the 2-trifluoromethyl-1H-benzimidazolium cations link to the [HgCl₄]²⁻ complex anions and lattice water molecules via N—H⋯Cl and N—H⋯O hydrogen bonds, and the lattice water molecules further link to the Hg complex anion and the organic cations via O—H⋯Cl and O—H⋯F hydrogen bonding. One of the trifluoromethyl groups is disordered over two orientations in a 0.59 (4):0.41 (4) ratio.

Related literature

For background to ferroelectric complexes, see: Fu et al. (2011 ▶); Ye et al. (2009 ▶). Zhang et al. (2009 ▶, 2010 ▶, 2012 ▶). For related structures, see: Liu (2011a ▶,b ▶, 2012a ▶,b ▶,c ▶).

Experimental

Crystal data

(C₈H₆F₃N₂)₂[HgCl₄]·2H₂O
M _r = 752.72
Triclinic,
a = 9.2485 (18) Å
b = 10.029 (2) Å
c = 14.754 (3) Å
α = 79.40 (3)°
β = 75.79 (3)°
γ = 67.74 (3)°
V = 1221.4 (4) Å³
Z = 2
Mo Kα radiation
μ = 6.81 mm⁻¹
T = 293 K
0.36 × 0.32 × 0.28 mm

Data collection

Rigaku SCXmini diffractometer
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005 ▶) T _min = 0.095, T _max = 0.152
12786 measured reflections
5564 independent reflections
4040 reflections with I > 2σ(I)
R _int = 0.061

Refinement

R[F ² > 2σ(F ²)] = 0.053
wR(F ²) = 0.119
S = 1.08
5564 reflections
326 parameters
9 restraints
H-atom parameters constrained
Δρ_max = 0.57 e Å⁻³
Δρ_min = −1.28 e Å⁻³

Data collection: CrystalClear (Rigaku, 2005 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536812018855/xu5519sup1.cif

e-68-0m716-sup1.cif^{(29.6KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812018855/xu5519Isup2.hkl

e-68-0m716-Isup2.hkl^{(272.4KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1A⋯Cl2ⁱ	0.86	2.23	3.081 (6)	170
N2—H2A⋯O1ⁱⁱ	0.86	1.80	2.656 (8)	174
N3—H3A⋯O2	0.86	1.76	2.608 (9)	166
N4—H4A⋯Cl1	0.86	2.21	3.069 (6)	175
O1—H1C⋯F3ⁱⁱⁱ	0.85	2.25	2.994 (18)	146
O1—H1B⋯Cl2^iv	0.85	2.55	3.279 (6)	144
O2—H2B⋯F5^v	0.85	2.41	3.224 (13)	160
O2—H2D⋯Cl3^vi	0.85	2.50	3.339 (10)	172

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) ; (vi) .

Acknowledgments

The author thanks an anonymous advisor from the Ordered Matter Science Research Centre, Southeast University, for great help in the revision of this paper.

supplementary crystallographic information

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. (Fu et al, 2011; Ye et al. 2009; Zhang et al. 2009; Zhang et al. 2012; Zhang et al. 2010). In our laboratory, the title compound has been synthesized to investigate to its potentialferroelectric properties. However, it was found that the dielectric constant of the compound as a function of temperature indicates that the permittivity is basically temperature-independent (ε = C/(T–T₀)), suggesting that this compound is not ferroelectric or there may be no distinct phase transition occurring within the measured temperature (below the melting point).

The title compound,(C₈H₆F₃N₂)₂⁺.HgCl₄^2-.2H₂O, has an asymmetric unit that consists of two 2-trifluoromethyl-1H-benzimidazol cations, one tetrachloridomercuriate anion and two water molecules (Fig 1). The atoms of the benzimidazole ring are nearly coplanar and the triflouromethyl group lies out of this plane. The mercury cation is coordinated by six Cl^- anions in distorted tetrahedral geometry.the average Hg—Cl bond distances range from 2.364 (2) Å to 2.564 (2) Å, the Cl—Hg—Cl angles range from 102.24 (8)°to 120.36 (9)°. In the crystal structure, the 2-trifluoromethyl-1H-benzimidazolecations are linked to adjacent tetrachloridomercuriate anions and watermolecules by N—H···O, N—H···Cl and O—H···Cl hydrogen bonds to form one dimensional chains parallel to ac plane (Fig 2). One of the trifluoromethyl is disordered.

Experimental

0.144 g (1 mmol) of 2-trifluoromethyl-1H-benzimidazol was firstly dissolved in 30 ml of ethanol which was added hydrochloric acid, to which 0.271 g (1 mmol) of mercuric chloride was added to give a solution at the ambient temperature. Single crystals suitable for X-ray structure analysis were obtained by the slow evaporation of the above solution after 5 days in air.