1,3,4,6-Tetra­chloro-7,7-bis­(4-chloro­phen­yl)bicyclo­[4.2.0]oct-3-ene-2,5-dione

Hu, H.; Li, L.; Ji, J.-F.; Shen, Z.-G.

doi:10.1107/S1600536808031139

organic compounds

CRYSTALLOGRAPHIC
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ISSN: 2056-9890

Volume 64| Part 11| November 2008| Page o2151

doi:10.1107/S1600536808031139

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1,3,4,6-Tetrachloro-7,7-bis(4-chlorophenyl)bicyclo[4.2.0]oct-3-ene-2,5-dione

Huayou Hu,^a ^* Lei Li,^a Jun-Feng Ji ^a and Zhi-Guo Shen ^a

^aSchool of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189, People's Republic of China
^*Correspondence e-mail: huayouhu@seu.edu.cn

(Received 24 September 2008; accepted 26 September 2008; online 22 October 2008)

The title compound, C₂₀H₁₀Cl₆O₂, a quinone derivative, was obtained by the irradiation of 2,3,5,6-tetrachlorobenzoquinone and 4,4′-(ethene-1,1-diyl)bis(chlorobenzene). The six- and four-membered rings are fused in a cis configuration. The dihedral angle between them is 53.4 (3)°.

Related literature

For related literature, see: Eckert & Goez (1994 ); Miyashi et al. (1985 ); Schenk (1960 ); Xu, Song et al. (1994 ); Xu, Wang et al. 1994 ); Xue et al. (2000 ). For a related structure, see: Braun et al. (1999 )

Experimental

Crystal data

C₂₀H₁₀Cl₆O₂
M_r = 494.98
Triclinic, $[P \overline 1]$
a = 8.6710 (17) Å
b = 9.6850 (19) Å
c = 12.864 (3) Å
α = 105.49 (3)°
β = 97.11 (3)°
γ = 102.68 (3)°
V = 996.4 (3) Å³
Z = 2
Mo Kα radiation
μ = 0.88 mm⁻¹
T = 293 (2) K
0.30 × 0.20 × 0.10 mm

Data collection

Enraf–Nonius CAD-4 diffractometer
Absorption correction: ψ scan (SHELXTL; Sheldrick, 2008 ) T_min = 0.779, T_max = 0.917
3879 measured reflections
3619 independent reflections
2787 reflections with I > 2σ(I)
R_int = 0.049
3 standard reflections every 200 reflections intensity decay: none

Refinement

R[F² > 2σ(F²)] = 0.066
wR(F²) = 0.192
S = 1.00
3619 reflections
253 parameters
H-atom parameters constrained
Δρ_max = 0.66 e Å⁻³
Δρ_min = −0.57 e Å⁻³

Data collection: CAD-4 Software (Enraf–Nonius, 1989 ); cell refinement: CAD-4 Software; data reduction: XCAD4 (Harms, 1993 ); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808031139/bt2797sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536808031139/bt2797Isup2.hkl

checkCIF report

Comment top

The reactions of the high potential 2,3,5,6-tetrachlorobenzoquinone with alkenes display varied reaction sites and regioselectivity, depending on the structure of the alkenes and reaction conditions (Schenk 1960; Miyashi et al. 1985; Eckert & Goez 1994; Xu, Song et al. 1994; Xu, Wang et al. 1994). While irradiation of a benzene solution of 2,3,5,6-tetrachlorobenzoquinone and 4,4'-(ethene-1,1-diyl)bis(chlorobenzene) with light of wavelength longer than 400 nm resulted in formation products of the title compound as a yellow solid (Xue et al. 2000). The yellow crystals were obtained by recrystallization of these solids from petroleum ether-chloroform.

The title compound, C₂₀H₁₀Cl₆O₂, is a quinone derivative. In the quinone, the distances of the C=O bonds are 1.191 (7) and 1.199 (7) Å, which are considered to to have full double-bond character. Meanwhile, the distances of C1—C2 and C5—C6 are, respectively, 1.478 (9) and 1.475 (8) Å, which are a little longer than that of C1=C6 (1.354 (9) Å), but shorter than those of C—C bonds (1.527 (8)–1.560 (7) Å). This shows that C1—C2 and C5—C6 bonds both have part double-bond character.

Related literature top

For related literature, see: Eckert & Goez (1994); Miyashi et al. (1985); Schenk (1960); Xu, Song et al. (1994); Xu, Wang et al. 1994); Xue et al. (2000). For a related structure, see: Braun et al. (1999)

Experimental top

Irradiation of a benzene solution of 2,3,5,6-tetrachlorobenzoquinone (0.05 mol L_-1) and 4,4'-(ethene-1,1-diyl)bis(chlorobenzene) (0.10 mol L_-1) with light of wavelength longer than 400 nm for 10 h resulted in complete consumption of 2,3,5,6-tetrachlorobenzoquinone and the formation of products 1,3,4,6-tetrachloro-7,7-bis(4-chlorophenyl)bicyclo[4.2.0]oct-3-ene-2,5-dione. Recrystallization from petroleum ether (bp 60–90 °) and chloroform gave a slightly yellow crystal.

Computing details top

Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software (Enraf–Nonius, 1989); data reduction: XCAD4 (Harms, 1993); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top

Fig. 1. The molecular structure of the title compound with 30% displacement ellipsoids.

1,3,4,6-Tetrachloro-7,7-bis(4-chlorophenyl)bicyclo[4.2.0]oct-3-ene-2,5-dione top

Crystal data top

C₂₀H₁₀Cl₆O₂	Z = 2
M_r = 494.98	F(000) = 496
Triclinic, P1	D_x = 1.650 Mg m⁻³
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 8.6710 (17) Å	Cell parameters from 25 reflections
b = 9.6850 (19) Å	θ = 10–13°
c = 12.864 (3) Å	µ = 0.88 mm⁻¹
α = 105.49 (3)°	T = 293 K
β = 97.11 (3)°	Block, yellow
γ = 102.68 (3)°	0.30 × 0.20 × 0.10 mm
V = 996.4 (3) Å³

Data collection top

Enraf–Nonius CAD-4 diffractometer	2787 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.049
Graphite monochromator	θ_max = 25.3°, θ_min = 1.7°
ω/2θ scans	h = −10→10
Absorption correction: ψ scan (SHELXTL; Sheldrick, 2008)	k = −11→11
T_min = 0.779, T_max = 0.917	l = 0→15
3879 measured reflections	3 standard reflections every 200 reflections
3619 independent reflections	intensity decay: none

Refinement top

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)] = 0.066	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.192	H-atom parameters constrained
S = 1.01	w = 1/[σ²(F_o²) + (0.06P)² + 6P] where P = (F_o² + 2F_c²)/3
3619 reflections	(Δ/σ)_max < 0.001
253 parameters	Δρ_max = 0.66 e Å⁻³
0 restraints	Δρ_min = −0.58 e Å⁻³

Crystal data top

C₂₀H₁₀Cl₆O₂	γ = 102.68 (3)°
M_r = 494.98	V = 996.4 (3) Å³
Triclinic, P1	Z = 2
a = 8.6710 (17) Å	Mo Kα radiation
b = 9.6850 (19) Å	µ = 0.88 mm⁻¹
c = 12.864 (3) Å	T = 293 K
α = 105.49 (3)°	0.30 × 0.20 × 0.10 mm
β = 97.11 (3)°

Data collection top

Enraf–Nonius CAD-4 diffractometer	2787 reflections with I > 2σ(I)
Absorption correction: ψ scan (SHELXTL; Sheldrick, 2008)	R_int = 0.049
T_min = 0.779, T_max = 0.917	3 standard reflections every 200 reflections
3879 measured reflections	intensity decay: none
3619 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.066	0 restraints
wR(F²) = 0.192	H-atom parameters constrained
S = 1.01	Δρ_max = 0.66 e Å⁻³
3619 reflections	Δρ_min = −0.58 e Å⁻³
253 parameters

Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Cl1	0.3758 (2)	0.1746 (2)	0.61309 (16)	0.0752 (6)
Cl2	0.0143 (2)	−0.07268 (16)	0.83090 (14)	0.0527 (4)
Cl3	0.4819 (2)	0.4713 (2)	0.81185 (19)	0.0761 (6)
Cl4	0.25830 (19)	0.20039 (18)	1.01117 (12)	0.0524 (4)
Cl5	−0.2014 (3)	0.5682 (2)	0.53637 (17)	0.0788 (6)
Cl6	−0.7475 (2)	−0.30216 (19)	0.73595 (17)	0.0653 (5)
O1	0.0754 (6)	−0.0161 (5)	0.6230 (4)	0.0625 (12)
O2	0.2265 (5)	0.4901 (4)	0.9419 (4)	0.0574 (11)
C1	0.2697 (7)	0.2059 (7)	0.7168 (5)	0.0444 (13)
C2	0.1230 (7)	0.0867 (6)	0.7046 (4)	0.0409 (13)
C3	0.0404 (6)	0.1008 (6)	0.8037 (4)	0.0365 (11)
C4	0.1223 (7)	0.2309 (6)	0.9110 (4)	0.0382 (12)
C5	0.2210 (6)	0.3667 (6)	0.8877 (4)	0.0384 (12)
C6	0.3165 (6)	0.3339 (6)	0.8013 (5)	0.0422 (13)
C7	−0.0468 (6)	0.2385 (6)	0.9327 (4)	0.0385 (12)
H7A	−0.0851	0.1819	0.9806	0.046*
H7B	−0.0580	0.3389	0.9577	0.046*
C8	−0.1175 (6)	0.1593 (6)	0.8105 (4)	0.0337 (11)
C9	−0.1295 (6)	0.2656 (6)	0.7408 (4)	0.0360 (11)
C10	−0.1477 (7)	0.2165 (6)	0.6274 (5)	0.0449 (13)
H10A	−0.1463	0.1193	0.5932	0.054*
C11	−0.1680 (9)	0.3087 (7)	0.5634 (5)	0.0554 (16)
H11A	−0.1766	0.2747	0.4876	0.067*
C12	−0.1752 (7)	0.4491 (6)	0.6133 (5)	0.0445 (13)
C13	−0.1599 (7)	0.5022 (6)	0.7252 (5)	0.0452 (13)
H13A	−0.1630	0.5991	0.7585	0.054*
C14	−0.1399 (7)	0.4087 (6)	0.7877 (5)	0.0459 (14)
H14A	−0.1332	0.4432	0.8633	0.055*
C15	−0.2792 (6)	0.0423 (6)	0.7864 (4)	0.0341 (11)
C16	−0.3207 (7)	−0.0869 (6)	0.6989 (5)	0.0441 (13)
H16A	−0.2506	−0.1029	0.6505	0.053*
C17	−0.4660 (7)	−0.1935 (7)	0.6820 (5)	0.0493 (14)
H17A	−0.4930	−0.2801	0.6229	0.059*
C18	−0.5684 (7)	−0.1687 (6)	0.7538 (5)	0.0431 (13)
C19	−0.5304 (7)	−0.0393 (7)	0.8409 (5)	0.0487 (14)
H19A	−0.6005	−0.0232	0.8893	0.058*
C20	−0.3883 (7)	0.0644 (6)	0.8548 (4)	0.0421 (13)
H20A	−0.3642	0.1527	0.9122	0.050*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cl1	0.0764 (12)	0.0926 (14)	0.0673 (11)	0.0278 (10)	0.0554 (10)	0.0190 (10)
Cl2	0.0647 (10)	0.0394 (8)	0.0665 (10)	0.0226 (7)	0.0264 (8)	0.0234 (7)
Cl3	0.0535 (10)	0.0653 (11)	0.1098 (16)	0.0045 (8)	0.0405 (10)	0.0250 (10)
Cl4	0.0565 (9)	0.0623 (9)	0.0436 (8)	0.0229 (7)	0.0147 (6)	0.0167 (7)
Cl5	0.1310 (18)	0.0587 (10)	0.0781 (12)	0.0495 (11)	0.0479 (12)	0.0402 (10)
Cl6	0.0518 (9)	0.0553 (10)	0.0947 (13)	0.0112 (7)	0.0326 (9)	0.0267 (9)
O1	0.080 (3)	0.054 (3)	0.049 (3)	0.019 (2)	0.038 (2)	−0.003 (2)
O2	0.069 (3)	0.037 (2)	0.064 (3)	0.014 (2)	0.032 (2)	0.003 (2)
C1	0.050 (3)	0.052 (3)	0.043 (3)	0.025 (3)	0.031 (3)	0.015 (3)
C2	0.048 (3)	0.049 (3)	0.039 (3)	0.030 (3)	0.026 (2)	0.014 (3)
C3	0.048 (3)	0.034 (3)	0.036 (3)	0.019 (2)	0.023 (2)	0.011 (2)
C4	0.047 (3)	0.034 (3)	0.035 (3)	0.013 (2)	0.018 (2)	0.005 (2)
C5	0.036 (3)	0.038 (3)	0.039 (3)	0.010 (2)	0.014 (2)	0.005 (2)
C6	0.032 (3)	0.047 (3)	0.052 (3)	0.014 (2)	0.015 (2)	0.017 (3)
C7	0.047 (3)	0.048 (3)	0.029 (3)	0.023 (2)	0.019 (2)	0.011 (2)
C8	0.042 (3)	0.038 (3)	0.031 (2)	0.021 (2)	0.021 (2)	0.012 (2)
C9	0.044 (3)	0.035 (3)	0.040 (3)	0.020 (2)	0.026 (2)	0.014 (2)
C10	0.067 (4)	0.037 (3)	0.040 (3)	0.028 (3)	0.023 (3)	0.010 (2)
C11	0.091 (5)	0.045 (3)	0.044 (3)	0.033 (3)	0.034 (3)	0.016 (3)
C12	0.047 (3)	0.036 (3)	0.058 (4)	0.014 (2)	0.023 (3)	0.018 (3)
C13	0.055 (3)	0.025 (3)	0.055 (3)	0.013 (2)	0.023 (3)	0.005 (2)
C14	0.060 (4)	0.039 (3)	0.046 (3)	0.021 (3)	0.031 (3)	0.010 (2)
C15	0.041 (3)	0.035 (3)	0.031 (3)	0.012 (2)	0.015 (2)	0.013 (2)
C16	0.048 (3)	0.043 (3)	0.044 (3)	0.015 (2)	0.029 (3)	0.006 (2)
C17	0.046 (3)	0.042 (3)	0.054 (4)	0.011 (3)	0.019 (3)	0.003 (3)
C18	0.038 (3)	0.047 (3)	0.051 (3)	0.014 (2)	0.013 (2)	0.022 (3)
C19	0.049 (3)	0.057 (4)	0.054 (3)	0.024 (3)	0.035 (3)	0.021 (3)
C20	0.050 (3)	0.043 (3)	0.039 (3)	0.020 (3)	0.021 (2)	0.011 (2)

Geometric parameters (Å, º) top

Cl1—C1	1.712 (5)	C9—C14	1.384 (7)
Cl2—C3	1.779 (5)	C9—C10	1.385 (7)
Cl3—C6	1.693 (6)	C10—C11	1.390 (8)
Cl4—C4	1.766 (6)	C10—H10A	0.9300
Cl5—C12	1.740 (6)	C11—C12	1.359 (8)
Cl6—C18	1.734 (6)	C11—H11A	0.9300
O1—C2	1.190 (7)	C12—C13	1.372 (8)
O2—C5	1.200 (6)	C13—C14	1.385 (8)
C1—C6	1.354 (8)	C13—H13A	0.9300
C1—C2	1.478 (8)	C14—H14A	0.9300
C2—C3	1.528 (7)	C15—C20	1.382 (7)
C3—C4	1.560 (7)	C15—C16	1.383 (7)
C3—C8	1.596 (7)	C16—C17	1.393 (8)
C4—C5	1.526 (7)	C16—H16A	0.9300
C4—C7	1.540 (7)	C17—C18	1.370 (8)
C5—C6	1.474 (7)	C17—H17A	0.9300
C7—C8	1.532 (7)	C18—C19	1.383 (8)
C7—H7A	0.9700	C19—C20	1.365 (8)
C7—H7B	0.9700	C19—H19A	0.9300
C8—C15	1.534 (7)	C20—H20A	0.9300
C8—C9	1.545 (7)

C6—C1—C2	123.4 (5)	C14—C9—C10	117.1 (5)
C6—C1—Cl1	121.3 (5)	C14—C9—C8	121.3 (5)
C2—C1—Cl1	115.2 (4)	C10—C9—C8	121.2 (5)
O1—C2—C1	121.5 (5)	C9—C10—C11	121.7 (5)
O1—C2—C3	122.3 (5)	C9—C10—H10A	119.1
C1—C2—C3	116.1 (5)	C11—C10—H10A	119.1
C2—C3—C4	118.3 (5)	C12—C11—C10	119.0 (6)
C2—C3—C8	123.0 (4)	C12—C11—H11A	120.5
C4—C3—C8	86.8 (4)	C10—C11—H11A	120.5
C2—C3—Cl2	106.0 (3)	C11—C12—C13	121.4 (5)
C4—C3—Cl2	110.3 (4)	C11—C12—Cl5	120.6 (5)
C8—C3—Cl2	111.5 (3)	C13—C12—Cl5	118.0 (4)
C5—C4—C7	115.4 (4)	C12—C13—C14	118.8 (5)
C5—C4—C3	112.4 (4)	C12—C13—H13A	120.6
C7—C4—C3	88.4 (4)	C14—C13—H13A	120.6
C5—C4—Cl4	103.3 (4)	C9—C14—C13	121.9 (5)
C7—C4—Cl4	118.9 (4)	C9—C14—H14A	119.0
C3—C4—Cl4	118.7 (4)	C13—C14—H14A	119.0
O2—C5—C6	123.6 (5)	C20—C15—C16	117.9 (5)
O2—C5—C4	121.0 (5)	C20—C15—C8	119.4 (5)
C6—C5—C4	115.2 (5)	C16—C15—C8	122.6 (4)
C1—C6—C5	122.0 (5)	C15—C16—C17	121.0 (5)
C1—C6—Cl3	122.7 (4)	C15—C16—H16A	119.5
C5—C6—Cl3	115.2 (4)	C17—C16—H16A	119.5
C8—C7—C4	89.8 (4)	C18—C17—C16	119.0 (5)
C8—C7—H7A	113.7	C18—C17—H17A	120.5
C4—C7—H7A	113.7	C16—C17—H17A	120.5
C8—C7—H7B	113.7	C17—C18—C19	120.9 (5)
C4—C7—H7B	113.7	C17—C18—Cl6	119.6 (5)
H7A—C7—H7B	110.9	C19—C18—Cl6	119.5 (4)
C7—C8—C15	114.9 (4)	C20—C19—C18	119.0 (5)
C7—C8—C9	114.1 (4)	C20—C19—H19A	120.5
C15—C8—C9	109.7 (4)	C18—C19—H19A	120.5
C7—C8—C3	87.4 (4)	C19—C20—C15	122.0 (5)
C15—C8—C3	117.2 (4)	C19—C20—H20A	119.0
C9—C8—C3	112.1 (4)	C15—C20—H20A	119.0

C6—C1—C2—O1	171.0 (6)	C4—C3—C8—C7	−20.4 (4)
Cl1—C1—C2—O1	−6.9 (8)	Cl2—C3—C8—C7	90.1 (4)
C6—C1—C2—C3	−11.0 (8)	C2—C3—C8—C15	100.7 (6)
Cl1—C1—C2—C3	171.1 (4)	C4—C3—C8—C15	−137.3 (4)
O1—C2—C3—C4	173.7 (5)	Cl2—C3—C8—C15	−26.7 (5)
C1—C2—C3—C4	−4.3 (7)	C2—C3—C8—C9	−27.4 (7)
O1—C2—C3—C8	−80.5 (7)	C4—C3—C8—C9	94.6 (4)
C1—C2—C3—C8	101.6 (6)	Cl2—C3—C8—C9	−154.9 (4)
O1—C2—C3—Cl2	49.4 (7)	C7—C8—C9—C14	−25.0 (7)
C1—C2—C3—Cl2	−128.6 (4)	C15—C8—C9—C14	105.5 (6)
C2—C3—C4—C5	29.4 (6)	C3—C8—C9—C14	−122.4 (5)
C8—C3—C4—C5	−96.7 (4)	C7—C8—C9—C10	162.0 (5)
Cl2—C3—C4—C5	151.6 (4)	C15—C8—C9—C10	−67.4 (6)
C2—C3—C4—C7	146.4 (5)	C3—C8—C9—C10	64.7 (7)
C8—C3—C4—C7	20.3 (4)	C14—C9—C10—C11	2.9 (9)
Cl2—C3—C4—C7	−91.5 (4)	C8—C9—C10—C11	176.2 (6)
C2—C3—C4—Cl4	−91.2 (5)	C9—C10—C11—C12	−2.1 (10)
C8—C3—C4—Cl4	142.7 (4)	C10—C11—C12—C13	1.2 (10)
Cl2—C3—C4—Cl4	30.9 (5)	C10—C11—C12—Cl5	−179.7 (5)
C7—C4—C5—O2	44.0 (7)	C11—C12—C13—C14	−1.2 (9)
C3—C4—C5—O2	143.4 (5)	Cl5—C12—C13—C14	179.7 (5)
Cl4—C4—C5—O2	−87.4 (6)	C10—C9—C14—C13	−3.0 (9)
C7—C4—C5—C6	−140.6 (5)	C8—C9—C14—C13	−176.2 (5)
C3—C4—C5—C6	−41.2 (6)	C12—C13—C14—C9	2.2 (9)
Cl4—C4—C5—C6	88.0 (5)	C7—C8—C15—C20	34.1 (7)
C2—C1—C6—C5	−1.7 (9)	C9—C8—C15—C20	−96.0 (5)
Cl1—C1—C6—C5	176.1 (4)	C3—C8—C15—C20	134.7 (5)
C2—C1—C6—Cl3	−178.1 (4)	C7—C8—C15—C16	−145.2 (5)
Cl1—C1—C6—Cl3	−0.3 (8)	C9—C8—C15—C16	84.8 (6)
O2—C5—C6—C1	−155.5 (6)	C3—C8—C15—C16	−44.6 (7)
C4—C5—C6—C1	29.3 (8)	C20—C15—C16—C17	−1.8 (9)
O2—C5—C6—Cl3	21.2 (8)	C8—C15—C16—C17	177.4 (5)
C4—C5—C6—Cl3	−154.1 (4)	C15—C16—C17—C18	0.0 (9)
C5—C4—C7—C8	93.0 (5)	C16—C17—C18—C19	1.0 (9)
C3—C4—C7—C8	−21.1 (4)	C16—C17—C18—Cl6	−178.5 (5)
Cl4—C4—C7—C8	−143.4 (4)	C17—C18—C19—C20	−0.1 (9)
C4—C7—C8—C15	139.6 (4)	Cl6—C18—C19—C20	179.4 (5)
C4—C7—C8—C9	−92.5 (5)	C18—C19—C20—C15	−1.8 (9)
C4—C7—C8—C3	20.7 (4)	C16—C15—C20—C19	2.8 (8)
C2—C3—C8—C7	−142.4 (5)	C8—C15—C20—C19	−176.5 (5)

Experimental details

Crystal data
Chemical formula	C₂₀H₁₀Cl₆O₂
M_r	494.98
Crystal system, space group	Triclinic, P1
Temperature (K)	293
a, b, c (Å)	8.6710 (17), 9.6850 (19), 12.864 (3)
α, β, γ (°)	105.49 (3), 97.11 (3), 102.68 (3)
V (Å³)	996.4 (3)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.88
Crystal size (mm)	0.30 × 0.20 × 0.10

Data collection
Diffractometer	Enraf–Nonius CAD-4 diffractometer
Absorption correction	ψ scan (SHELXTL; Sheldrick, 2008)
T_min, T_max	0.779, 0.917
No. of measured, independent and observed [I > 2σ(I)] reflections	3879, 3619, 2787
R_int	0.049
(sin θ/λ)_max (Å⁻¹)	0.601

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.066, 0.192, 1.01
No. of reflections	3619
No. of parameters	253
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.66, −0.58

Computer programs: CAD-4 Software (Enraf–Nonius, 1989), XCAD4 (Harms, 1993), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Acknowledgements

The authors thank the Program for Young Excellent Talents in Southeast University for financial support.

References

Braun, M., Christl, M., Peters, E.-M. & Peters, K. (1999). J. Chem. Soc. Perkin Trans. 1, pp. 2813–2820. Web of Science CSD CrossRef Google Scholar
Eckert, G. & Goez, M. (1994). J. Am. Chem. Soc. 116, 11999–12009. CrossRef CAS Web of Science Google Scholar
Enraf–Nonius (1989). CAD-4 Software. Enraf–Nonius, Delft, The Netherlands. Google Scholar
Harms, K. (1993). XCAD4. University of Marburg, Germany. Google Scholar
Miyashi, T., Takahashi, Y., Mukai, T., Roth, H. D. & Schilling, M. L. M. (1985). J. Am. Chem. Soc. 107, 1079–1080. CrossRef CAS Web of Science Google Scholar
Schenk, G. O. Z. (1960). Electrochemistry, 64, 997–1011. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Xu, J. H., Song, Y. L., Zhang, Z. G., Wang, L. C. & Xu, J. W. (1994). Tetrahedron, 50, 1199–1210. CrossRef CAS Web of Science Google Scholar
Xu, J. H., Wang, L. C., Xu, J. W., Yan, B. Z. & Yuan, H. C. (1994). J. Chem. Soc. Perkin Trans. 1, pp. 571–577. CrossRef Web of Science Google Scholar
Xue, J., Xu, J.-W., Yang, L. & Xu, J.-H. (2000). J. Org. Chem. 65, 30–40. Web of Science CrossRef PubMed CAS Google Scholar

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