(1R,2R,5R,6R,9S,10S,13S,14S)-1,6,7,8,9,14,15,16,17,17-Decachloro­penta­cyclo­[12.2.1.16,9.02,13.05,10]octa­deca-7,15-diene

Riddell, N.; McCrindle, R.; Arsenault, G.; Lough, A.J.

doi:10.1107/S1600536808016231

organic compounds

CRYSTALLOGRAPHIC
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ISSN: 2056-9890

Volume 64| Part 7| July 2008| Page o1249

doi:10.1107/S1600536808016231

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(1R,2R,5R,6R,9S,10S,13S,14S)-1,6,7,8,9,14,15,16,17,17-Decachloropentacyclo[12.2.1.1^6,9.0^2,13.0^5,10]octadeca-7,15-diene

Nicole Riddell,^a Robert McCrindle,^b Gilles Arsenault ^a and Alan J Lough ^c ^*

^aWellington Laboratories, Research Division, Guelph, Ontario, Canada N1G 3M5, ^bDepartment of Chemistry, University of Guelph, Ontario, Canada N1G 2W1, and ^cDepartment of Chemistry, University of Toronto, Ontario, Canada M5S 3H6
^*Correspondence e-mail: alough@chem.utoronto.ca

(Received 20 May 2008; accepted 28 May 2008; online 13 June 2008)

The title compound, C₁₈H₁₄Cl₁₀, is a decachlorinated commercial flame retardant. The structure determination confirms the relative stereochemistry. The central eight-membered ring is in a chair-type conformation. In the crystal structure, there are no significant intermolecular interactions and molecules are separated by normal van der Waals distances.

Related literature

For related literature, see: Garcia et al. (1991 ); Hoh et al. (2006 ); Qiu et al. (2007 ); Sverko et al. (2008 ); Tomy et al. (2007 ).

Experimental

Crystal data

C₁₈H₁₄Cl₁₀
M_r = 584.79
Orthorhombic, P 2₁ 2₁ 2₁
a = 11.4341 (2) Å
b = 12.9704 (3) Å
c = 15.0389 (4) Å
V = 2230.34 (9) Å³
Z = 4
Mo Kα radiation
μ = 1.25 mm⁻¹
T = 150 (1) K
0.24 × 0.20 × 0.18 mm

Data collection

Bruker–Nonius KappaCCD diffractometer
Absorption correction: multi-scan (SORTAV; Blessing, 1995 ) T_min = 0.720, T_max = 0.804
17031 measured reflections
5087 independent reflections
4585 reflections with I > 2σ(I)
R_int = 0.036

Refinement

R[F² > 2σ(F²)] = 0.032
wR(F²) = 0.072
S = 1.04
5087 reflections
253 parameters
H-atom parameters constrained
Δρ_max = 0.34 e Å⁻³
Δρ_min = −0.32 e Å⁻³
Absolute structure: Flack (1983 ), 2207 Friedel pairs
Flack parameter: −0.01 (6)

Data collection: COLLECT (Nonius, 2002 ); cell refinement: DENZO–SMN (Otwinowski & Minor, 1997 ); data reduction: DENZO–SMN; program(s) used to solve structure: SIR92 (Altomare et al., 1994 ); program(s) used to refine structure: SHELXTL (Sheldrick, 2008 ); molecular graphics: PLATON (Spek, 2003 ); software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808016231/bt2716sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536808016231/bt2716Isup2.hkl

checkCIF report

Comment top

Dechlorane Plus (DP) is a commercial chlorinated flame retardant used in styrenic plastics (http://www.inchem.org/documents/ehc/ehc/ehc192.htm) to protect human life and property against fires. The two major components found in the commercial material are known as syn-DP (1R,2R,5S,6S,9R,10R,13S,14S)-[1,6,7,8,9,14,15,16,17,17,18,18- decachloropentacyclo[12.2.1.16,9.02,13.05,10]-octadeca-7,15-diene] and anti-DP (1R,2R,5R,6R,9S,10S,13S,14S)-[1,6,7,8,9,14,15,16,17,17,18,18- decachloropentacyclo[12.2.1.16,9.02,13.05,10]-octadeca-7,15-diene] (see (1) and (2) respectively, Fig. 1). X-ray structure determinations have already been completed on both compounds (Garcia et al., 1991). There is growing evidence that this flame retardant is becoming a significant environmental contaminant (Hoh et al., 2006; Qiu et al., 2007; Tomy et al., 2007). 3–5 Dechlorinated DP species have also been detected in the environment (Sverko et al., 2008) although very little is known about their identity. It is important to identify these compounds if analytical chemists wish to quantify the total presence of DP, including its dechlorinated homologues, in the environment.

We have synthesized the dechlorinated compound (1R,2R,5R,6R,9S,10S,13S,14S)-1,6,7,8,9,14,15,16,17,17-decachloropentacyclo[ 12.2.1.16,9.02,13.05,10]-octadeca-7,15-diene (compound (3); see Fig. 1). GC/MS and ¹H NMR spectroscopy have confirmed the basic structure of (3) as having the DP-like structure with only 10 chlorine atoms. X-ray structure determination of (3) was required to positively confirm the relative stereochemistry.

Related literature top

For related literature, see: Garcia et al. (1991); Hoh et al. (2006); Qiu et al. (2007); Sverko et al. (2008); Tomy et al. (2007).

Experimental top

The synthesis of compound (3) was carried out at Wellington Laboratories using proprietary methods. The compound was isolated and purified using chromatographic techniques. For single-crystal X-ray crystallography, colourless crystals were grown from a solution of (3) in toluene.

Computing details top

Data collection: COLLECT (Nonius, 2002); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top

	Fig. 1. Schematic representation of compounds (1), (2) and (3).
	Fig. 2. The molecular structure of the title compound. Displacement ellipsoids are at the 30% probability level. H atoms are not shown.

(1R,2R,5R,6R,9S,10S,13S,14S)- 1,6,7,8,9,14,15,16,17,17- Decachloropentacyclo[12.2.1.1^6,9.0^2,13.0^5,10]octadeca-7,15-diene top

Crystal data top

C₁₈H₁₄Cl₁₀	F(000) = 1168
M_r = 584.79	D_x = 1.742 Mg m⁻³
Orthorhombic, P2₁2₁2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2ab	Cell parameters from 17031 reflections
a = 11.4341 (2) Å	θ = 2.7–27.5°
b = 12.9704 (3) Å	µ = 1.26 mm⁻¹
c = 15.0389 (4) Å	T = 150 K
V = 2230.34 (9) Å³	Block, colourless
Z = 4	0.24 × 0.20 × 0.18 mm

Data collection top

Bruker–Nonius KappaCCD diffractometer	5087 independent reflections
Radiation source: fine-focus sealed tube	4585 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.036
Detector resolution: 9 pixels mm^-1	θ_max = 27.5°, θ_min = 2.7°
ϕ scans and ω scans with κ offsets	h = −14→14
Absorption correction: multi-scan (SORTAV; Blessing, 1995)	k = −16→16
T_min = 0.720, T_max = 0.804	l = −19→19
17031 measured reflections

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.032	H-atom parameters constrained
wR(F²) = 0.072	w = 1/[σ²(F_o²) + (0.03P)² + 1.117P] where P = (F_o² + 2F_c²)/3
S = 1.04	(Δ/σ)_max = 0.001
5087 reflections	Δρ_max = 0.34 e Å⁻³
253 parameters	Δρ_min = −0.32 e Å⁻³
0 restraints	Absolute structure: Flack (1983), 2207 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: −0.01 (6)

Crystal data top

C₁₈H₁₄Cl₁₀	V = 2230.34 (9) Å³
M_r = 584.79	Z = 4
Orthorhombic, P2₁2₁2₁	Mo Kα radiation
a = 11.4341 (2) Å	µ = 1.26 mm⁻¹
b = 12.9704 (3) Å	T = 150 K
c = 15.0389 (4) Å	0.24 × 0.20 × 0.18 mm

Data collection top

Bruker–Nonius KappaCCD diffractometer	5087 independent reflections
Absorption correction: multi-scan (SORTAV; Blessing, 1995)	4585 reflections with I > 2σ(I)
T_min = 0.720, T_max = 0.804	R_int = 0.036
17031 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.032	H-atom parameters constrained
wR(F²) = 0.072	Δρ_max = 0.34 e Å⁻³
S = 1.04	Δρ_min = −0.32 e Å⁻³
5087 reflections	Absolute structure: Flack (1983), 2207 Friedel pairs
253 parameters	Absolute structure parameter: −0.01 (6)
0 restraints

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	0.87131 (5)	0.78434 (5)	0.55246 (4)	0.02288 (14)
Cl2	1.07256 (5)	0.66212 (5)	0.43725 (5)	0.02523 (14)
Cl3	1.14507 (6)	0.81013 (6)	0.25760 (5)	0.03027 (16)
Cl4	0.97237 (6)	1.01756 (5)	0.25571 (5)	0.03129 (16)
Cl5	1.03310 (6)	0.98603 (5)	0.47707 (4)	0.02853 (16)
Cl6	0.78892 (6)	1.00833 (5)	0.44082 (5)	0.03032 (16)
Cl7	0.68597 (7)	0.61445 (6)	−0.03570 (5)	0.03760 (18)
Cl8	0.45590 (8)	0.74067 (6)	0.04705 (6)	0.0468 (2)
Cl9	0.36780 (6)	0.61715 (7)	0.23695 (6)	0.0441 (2)
Cl10	0.53873 (7)	0.41158 (6)	0.26610 (5)	0.0406 (2)
C1	0.7915 (2)	0.78678 (19)	0.37527 (16)	0.0184 (5)
H1A	0.7177	0.8161	0.4004	0.022*
C2	0.8244 (2)	0.8505 (2)	0.28950 (17)	0.0195 (5)
H2A	0.7614	0.9026	0.2790	0.023*
C3	0.8459 (2)	0.7930 (2)	0.20247 (17)	0.0205 (5)
H3A	0.8959	0.7325	0.2154	0.025*
H3B	0.8907	0.8389	0.1624	0.025*
C4	0.7364 (2)	0.75489 (19)	0.15180 (17)	0.0197 (5)
H4A	0.6656	0.7817	0.1818	0.024*
H4B	0.7378	0.7832	0.0907	0.024*
C5	0.7288 (2)	0.63674 (19)	0.14688 (17)	0.0190 (5)
H5A	0.8081	0.6103	0.1306	0.023*
C6	0.6879 (2)	0.57719 (19)	0.23264 (17)	0.0192 (5)
H6A	0.7506	0.5264	0.2479	0.023*
C7	0.6627 (2)	0.6394 (2)	0.31572 (17)	0.0220 (6)
H7A	0.6127	0.5982	0.3560	0.026*
H7B	0.6188	0.7023	0.2991	0.026*
C8	0.7757 (2)	0.6710 (2)	0.36566 (17)	0.0205 (5)
H8A	0.7746	0.6396	0.4257	0.025*
H8B	0.8440	0.6425	0.3335	0.025*
C9	0.8936 (2)	0.81438 (18)	0.43944 (18)	0.0186 (5)
C10	1.0060 (2)	0.77145 (19)	0.40053 (17)	0.0194 (5)
C11	1.0325 (2)	0.8277 (2)	0.32990 (17)	0.0213 (5)
C12	0.9372 (2)	0.9089 (2)	0.32037 (17)	0.0212 (5)
C13	0.9127 (2)	0.93046 (19)	0.42002 (18)	0.0213 (6)
C14	0.6406 (2)	0.5965 (2)	0.07546 (17)	0.0239 (6)
C15	0.5203 (2)	0.6380 (2)	0.09832 (19)	0.0258 (6)
C16	0.4856 (2)	0.5901 (2)	0.17161 (19)	0.0257 (6)
C17	0.5815 (2)	0.5147 (2)	0.19615 (19)	0.0237 (6)
C18	0.6255 (3)	0.4837 (2)	0.10393 (18)	0.0252 (6)
H18A	0.5664	0.4462	0.0683	0.030*
H18B	0.7000	0.4449	0.1056	0.030*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cl1	0.0260 (3)	0.0273 (3)	0.0153 (3)	−0.0008 (3)	0.0011 (3)	0.0010 (3)
Cl2	0.0230 (3)	0.0248 (3)	0.0278 (4)	0.0037 (3)	−0.0027 (3)	0.0018 (3)
Cl3	0.0259 (3)	0.0390 (4)	0.0259 (4)	−0.0050 (3)	0.0075 (3)	−0.0007 (3)
Cl4	0.0420 (4)	0.0240 (3)	0.0279 (4)	−0.0119 (3)	−0.0062 (3)	0.0095 (3)
Cl5	0.0351 (4)	0.0252 (3)	0.0253 (3)	−0.0091 (3)	−0.0081 (3)	−0.0011 (3)
Cl6	0.0369 (4)	0.0227 (3)	0.0313 (4)	0.0081 (3)	−0.0059 (3)	−0.0054 (3)
Cl7	0.0549 (5)	0.0391 (4)	0.0189 (3)	−0.0113 (4)	0.0010 (3)	−0.0043 (3)
Cl8	0.0578 (5)	0.0361 (4)	0.0465 (5)	0.0171 (4)	−0.0290 (4)	−0.0059 (4)
Cl9	0.0230 (3)	0.0645 (5)	0.0447 (5)	−0.0044 (4)	0.0035 (3)	−0.0276 (4)
Cl10	0.0526 (5)	0.0323 (4)	0.0367 (4)	−0.0228 (4)	−0.0016 (4)	0.0057 (3)
C1	0.0190 (12)	0.0201 (12)	0.0160 (13)	−0.0019 (10)	−0.0024 (10)	0.0008 (10)
C2	0.0224 (12)	0.0174 (12)	0.0188 (13)	0.0012 (10)	−0.0026 (10)	0.0015 (10)
C3	0.0218 (12)	0.0225 (13)	0.0172 (13)	−0.0028 (11)	−0.0007 (10)	0.0013 (11)
C4	0.0257 (13)	0.0186 (13)	0.0150 (13)	−0.0049 (10)	−0.0029 (10)	0.0019 (10)
C5	0.0192 (12)	0.0185 (12)	0.0193 (13)	0.0009 (10)	−0.0015 (10)	−0.0029 (10)
C6	0.0196 (11)	0.0190 (12)	0.0190 (13)	−0.0015 (10)	−0.0026 (10)	0.0016 (10)
C7	0.0190 (12)	0.0259 (14)	0.0210 (13)	−0.0058 (11)	−0.0003 (10)	0.0021 (11)
C8	0.0223 (13)	0.0207 (13)	0.0186 (13)	−0.0022 (11)	−0.0013 (11)	0.0016 (11)
C9	0.0220 (12)	0.0174 (12)	0.0163 (12)	0.0005 (9)	−0.0007 (10)	0.0028 (10)
C10	0.0191 (12)	0.0195 (12)	0.0197 (13)	−0.0007 (10)	−0.0037 (10)	−0.0010 (10)
C11	0.0195 (12)	0.0233 (13)	0.0210 (14)	−0.0045 (11)	0.0010 (11)	−0.0051 (11)
C12	0.0276 (14)	0.0182 (12)	0.0179 (13)	−0.0045 (11)	−0.0028 (11)	0.0036 (10)
C13	0.0235 (12)	0.0185 (13)	0.0220 (15)	−0.0008 (11)	−0.0020 (10)	−0.0028 (10)
C14	0.0306 (14)	0.0222 (13)	0.0190 (14)	0.0001 (12)	−0.0026 (11)	−0.0034 (11)
C15	0.0246 (13)	0.0214 (13)	0.0315 (16)	0.0026 (11)	−0.0145 (12)	−0.0078 (11)
C16	0.0179 (12)	0.0310 (15)	0.0282 (16)	−0.0047 (12)	−0.0035 (11)	−0.0109 (12)
C17	0.0262 (13)	0.0181 (12)	0.0267 (15)	−0.0055 (11)	0.0001 (11)	−0.0004 (11)
C18	0.0299 (14)	0.0196 (13)	0.0261 (14)	−0.0021 (12)	−0.0017 (12)	−0.0036 (11)

Geometric parameters (Å, º) top

Cl1—C9	1.762 (3)	C5—C14	1.563 (4)
Cl2—C10	1.701 (3)	C5—C6	1.574 (3)
Cl3—C11	1.700 (3)	C5—H5A	1.0000
Cl4—C12	1.758 (3)	C6—C7	1.515 (4)
Cl5—C13	1.775 (3)	C6—C17	1.562 (3)
Cl6—C13	1.766 (3)	C6—H6A	1.0000
Cl7—C14	1.766 (3)	C7—C8	1.550 (3)
Cl8—C15	1.706 (3)	C7—H7A	0.9900
Cl9—C16	1.704 (3)	C7—H7B	0.9900
Cl10—C17	1.771 (3)	C8—H8A	0.9900
C1—C8	1.519 (3)	C8—H8B	0.9900
C1—C9	1.557 (3)	C9—C10	1.518 (3)
C1—C2	1.577 (3)	C9—C13	1.549 (3)
C1—H1A	1.0000	C10—C11	1.324 (4)
C2—C3	1.526 (4)	C11—C12	1.522 (4)
C2—C12	1.567 (4)	C12—C13	1.550 (4)
C2—H2A	1.0000	C14—C15	1.517 (4)
C3—C4	1.547 (3)	C14—C18	1.534 (4)
C3—H3A	0.9900	C15—C16	1.326 (4)
C3—H3B	0.9900	C16—C17	1.514 (4)
C4—C5	1.537 (3)	C17—C18	1.529 (4)
C4—H4A	0.9900	C18—H18A	0.9900
C4—H4B	0.9900	C18—H18B	0.9900

C8—C1—C9	112.1 (2)	C10—C9—C13	99.5 (2)
C8—C1—C2	117.9 (2)	C10—C9—C1	108.2 (2)
C9—C1—C2	102.00 (19)	C13—C9—C1	102.2 (2)
C8—C1—H1A	108.1	C10—C9—Cl1	114.42 (17)
C9—C1—H1A	108.1	C13—C9—Cl1	114.65 (18)
C2—C1—H1A	108.1	C1—C9—Cl1	116.00 (18)
C3—C2—C12	110.9 (2)	C11—C10—C9	107.5 (2)
C3—C2—C1	118.9 (2)	C11—C10—Cl2	128.1 (2)
C12—C2—C1	101.96 (19)	C9—C10—Cl2	124.01 (19)
C3—C2—H2A	108.2	C10—C11—C12	107.0 (2)
C12—C2—H2A	108.2	C10—C11—Cl3	127.8 (2)
C1—C2—H2A	108.2	C12—C11—Cl3	125.06 (19)
C2—C3—C4	116.6 (2)	C11—C12—C13	99.4 (2)
C2—C3—H3A	108.1	C11—C12—C2	106.4 (2)
C4—C3—H3A	108.1	C13—C12—C2	103.0 (2)
C2—C3—H3B	108.1	C11—C12—Cl4	116.30 (19)
C4—C3—H3B	108.1	C13—C12—Cl4	115.59 (18)
H3A—C3—H3B	107.3	C2—C12—Cl4	114.32 (18)
C5—C4—C3	112.9 (2)	C9—C13—C12	91.88 (19)
C5—C4—H4A	109.0	C9—C13—Cl6	114.20 (18)
C3—C4—H4A	109.0	C12—C13—Cl6	114.79 (18)
C5—C4—H4B	109.0	C9—C13—Cl5	114.36 (18)
C3—C4—H4B	109.0	C12—C13—Cl5	113.56 (18)
H4A—C4—H4B	107.8	Cl6—C13—Cl5	107.68 (13)
C4—C5—C14	113.8 (2)	C15—C14—C18	100.0 (2)
C4—C5—C6	117.8 (2)	C15—C14—C5	108.1 (2)
C14—C5—C6	101.98 (19)	C18—C14—C5	101.5 (2)
C4—C5—H5A	107.6	C15—C14—Cl7	115.73 (19)
C14—C5—H5A	107.6	C18—C14—Cl7	115.04 (18)
C6—C5—H5A	107.6	C5—C14—Cl7	114.65 (19)
C7—C6—C17	114.7 (2)	C16—C15—C14	107.1 (2)
C7—C6—C5	118.1 (2)	C16—C15—Cl8	127.8 (2)
C17—C6—C5	101.4 (2)	C14—C15—Cl8	124.5 (2)
C7—C6—H6A	107.3	C15—C16—C17	106.8 (2)
C17—C6—H6A	107.3	C15—C16—Cl9	128.3 (2)
C5—C6—H6A	107.3	C17—C16—Cl9	124.4 (2)
C6—C7—C8	112.5 (2)	C16—C17—C18	100.8 (2)
C6—C7—H7A	109.1	C16—C17—C6	108.4 (2)
C8—C7—H7A	109.1	C18—C17—C6	101.5 (2)
C6—C7—H7B	109.1	C16—C17—Cl10	115.6 (2)
C8—C7—H7B	109.1	C18—C17—Cl10	115.51 (19)
H7A—C7—H7B	107.8	C6—C17—Cl10	113.47 (19)
C1—C8—C7	114.0 (2)	C17—C18—C14	92.2 (2)
C1—C8—H8A	108.8	C17—C18—H18A	113.2
C7—C8—H8A	108.8	C14—C18—H18A	113.2
C1—C8—H8B	108.8	C17—C18—H18B	113.2
C7—C8—H8B	108.8	C14—C18—H18B	113.2
H8A—C8—H8B	107.6	H18A—C18—H18B	110.6

Experimental details

Crystal data
Chemical formula	C₁₈H₁₄Cl₁₀
M_r	584.79
Crystal system, space group	Orthorhombic, P2₁2₁2₁
Temperature (K)	150
a, b, c (Å)	11.4341 (2), 12.9704 (3), 15.0389 (4)
V (Å³)	2230.34 (9)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	1.26
Crystal size (mm)	0.24 × 0.20 × 0.18

Data collection
Diffractometer	Bruker–Nonius KappaCCD diffractometer
Absorption correction	Multi-scan (SORTAV; Blessing, 1995)
T_min, T_max	0.720, 0.804
No. of measured, independent and observed [I > 2σ(I)] reflections	17031, 5087, 4585
R_int	0.036
(sin θ/λ)_max (Å⁻¹)	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.032, 0.072, 1.04
No. of reflections	5087
No. of parameters	253
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.34, −0.32
Absolute structure	Flack (1983), 2207 Friedel pairs
Absolute structure parameter	−0.01 (6)

Computer programs: COLLECT (Nonius, 2002), DENZO-SMN (Otwinowski & Minor, 1997), SIR92 (Altomare et al., 1994), SHELXTL (Sheldrick, 2008), PLATON (Spek, 2003).

Acknowledgements

The authors acknowledge NSERC Canada and the University of Toronto for funding.

References

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