Chloranilic acid: a redetermination at 100 K.

The crystal structure of chloranilic acid, C(6)H(2)Cl(2)O(4), was first described by Andersen in 1967 [Andersen, E. K. (1967). Acta Cryst. 22, 188-191] at room temperature using visually estimated intensities. Taking into account the importance of the title compound, we have redetermined the structure at 100 (1) K. The approximately planar mol-ecule [the maximum deviation from the mean plane through the ring is 0.0014 (9) Å for the ring atoms and 0.029 (3) Å for the other atoms] occupies a special position, lying across the center of symmetry. In the crystal structure, a two-dimensional hydrogen-bonded network sustained by O-H⋯O inter-actions runs approximately parallel to [101]. The two-dimensional layers are further packed in a parallel fashion, stabilized by Cl⋯Cl inter-actions [Cl⋯Cl = 3.2838 (8) Å, C-Cl⋯Cl = 152.96 (6)°].

Related literature

For charge-transfer complexes of chloranilic acid, see: Gotoh et al. (2006 ▶, 2007 ▶, 2008 ▶); Gotoh & Ishida (2009 ▶); Ishida (2004 ▶); Ishida & Kashino (1999 ▶). For a recent study of the formation of either salts or co-crystals by chloranilic acid with different organic bases, see: Molčanov & Kojić-Prodić (2010 ▶). For the previous determination of the title structure, see: Andersen (1967a ▶) and of its hydrate, see: Andersen (1967b ▶). For hydrogen-bond motifs, see: Bernstein et al. (1995 ▶). For a description of the Cambridge Structural Database, see: (Allen, 2002 ▶).

Experimental

Crystal data

C6H2Cl2O4

M = 208.98

Monoclinic,

a = 7.5338 (12) Å

b = 5.5225 (10) Å

c = 8.5720 (12) Å

β = 104.868 (11)°

V = 344.70 (10) Å3

Z = 2

Mo Kα radiation

μ = 0.90 mm−1

T = 100 K

0.3 × 0.1 × 0.1 mm

Data collection

Oxford Diffraction Xcalibur Eos diffractometer

Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction (2009 ▶)) T min = 0.857, T max = 1.000

6154 measured reflections

774 independent reflections

698 reflections with I > 2σ(I)

R int = 0.032

Refinement

R[F 2 > 2σ(F 2)] = 0.025

wR(F 2) = 0.056

S = 1.09

774 reflections

59 parameters

All H-atom parameters refined

Δρmax = 0.37 e Å−3

Δρmin = −0.27 e Å−3

Data collection: CrysAlis PRO (Oxford Diffraction, 2009 ▶); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO program(s) used to solve structure: SIR92 (Altomare et al., 1993 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: Stereochemical Workstation Operation Manual (Siemens, 1989 ▶); software used to prepare material for publication: SHELXL97.

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810003387/ds2017sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810003387/ds2017Isup2.hkl

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

C6H2Cl2O4	F(000) = 208
Mr = 208.98	Dx = 2.014 Mg m−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 4539 reflections
a = 7.5338 (12) Å	θ = 2.8–27.8°
b = 5.5225 (10) Å	µ = 0.90 mm−1
c = 8.5720 (12) Å	T = 100 K
β = 104.868 (11)°	Prism, red
V = 344.70 (10) Å3	0.3 × 0.1 × 0.1 mm
Z = 2

Oxford Diffraction Xcalibur Eos diffractometer	774 independent reflections
Radiation source: Enhance (Mo) X-ray Source	698 reflections with I > 2σ(I)
graphite	Rint = 0.032
Detector resolution: 16.1544 pixels mm-1	θmax = 27.9°, θmin = 3.2°
ω–scan	h = −9→9
Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction (2009))	k = −7→7
Tmin = 0.857, Tmax = 1.000	l = −11→10
6154 measured reflections

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.025	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.056	All H-atom parameters refined
S = 1.09	w = 1/[σ2(Fo2) + (0.0204P)2 + 0.3502P] where P = (Fo2 + 2Fc2)/3
774 reflections	(Δ/σ)max < 0.001
59 parameters	Δρmax = 0.37 e Å−3
0 restraints	Δρmin = −0.27 e Å−3

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 F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

	x	y	z	Uiso*/Ueq
C1	0.8496 (2)	−0.1699 (3)	0.47066 (18)	0.0102 (3)
Cl1	0.66487 (5)	−0.36207 (7)	0.44138 (4)	0.01295 (13)
C2	0.9798 (2)	−0.1990 (3)	0.38967 (18)	0.0101 (3)
O2	0.97189 (15)	−0.3741 (2)	0.28296 (13)	0.0132 (3)
H2	1.064 (3)	−0.381 (4)	0.249 (3)	0.034 (7)*
C3	1.14042 (19)	−0.0274 (3)	0.41584 (17)	0.0095 (3)
O3	1.25301 (15)	−0.0641 (2)	0.33789 (13)	0.0126 (2)

	U11	U22	U33	U12	U13	U23
C1	0.0081 (7)	0.0100 (8)	0.0122 (7)	−0.0022 (6)	0.0020 (6)	0.0014 (6)
Cl1	0.01094 (19)	0.0138 (2)	0.0150 (2)	−0.00495 (14)	0.00488 (13)	−0.00150 (14)
C2	0.0113 (7)	0.0081 (7)	0.0102 (7)	0.0005 (6)	0.0016 (6)	0.0013 (6)
O2	0.0121 (5)	0.0133 (6)	0.0163 (6)	−0.0014 (4)	0.0075 (5)	−0.0045 (4)
C3	0.0084 (7)	0.0103 (7)	0.0098 (7)	0.0010 (6)	0.0021 (6)	0.0041 (6)
O3	0.0121 (5)	0.0131 (6)	0.0147 (5)	0.0003 (4)	0.0072 (4)	0.0008 (4)

C1—C2	1.349 (2)	C2—C3	1.508 (2)
C1—C3i	1.450 (2)	O2—H2	0.82 (2)
C1—Cl1	1.7164 (15)	C3—O3	1.2240 (18)
C2—O2	1.3217 (19)
C2—C1—C3i	121.02 (14)	C1—C2—C3	120.71 (14)
C2—C1—Cl1	121.38 (12)	C2—O2—H2	112.9 (17)
C3i—C1—Cl1	117.59 (11)	O3—C3—C1i	124.53 (14)
O2—C2—C1	122.23 (14)	O3—C3—C2	117.19 (14)
O2—C2—C3	117.05 (13)	C1i—C3—C2	118.27 (13)
C3i—C1—C2—O2	−178.48 (14)	O2—C2—C3—O3	−0.8 (2)
Cl1—C1—C2—O2	0.7 (2)	C1—C2—C3—O3	−179.74 (14)
C3i—C1—C2—C3	0.4 (2)	O2—C2—C3—C1i	178.55 (13)
Cl1—C1—C2—C3	179.51 (11)	C1—C2—C3—C1i	−0.4 (2)

D—H···A	D—H	H···A	D···A	D—H···A
O2—H2···O3ii	0.82 (2)	2.00 (2)	2.7516 (15)	152 (2)

Table 1

Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H2⋯O3i	0.82 (2)	2.00 (2)	2.7516 (15)	152 (2)

Symmetry code: (i) .