(1S,3R,8R,9S,11R)-2,2-Di­bromo-10,10-di­chloro-3,7,7,11-tetra­methyl­tetra­cyclo­[6.5.0.01,3.09,11]trideca­ne

Ourhriss, N.; Benharref, A.; Saadi, M.; Berraho, M.; El Ammari, L.

doi:10.1107/S1600536813009070

organic compounds

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ISSN: 2056-9890

Volume 69| Part 5| May 2013| Page o724

https://doi.org/10.1107/S1600536813009070

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(1S,3R,8R,9S,11R)-2,2-Dibromo-10,10-dichloro-3,7,7,11-tetramethyltetracyclo[6.5.0.0^1,3.0^9,11]tridecane

Najia Ourhriss,^a ^* Ahmed Benharref,^a Mohamed Saadi,^b Moha Berraho ^a and Lahcen El Ammari ^b

^aLaboratoire de Chimie Biomoléculaire, Substances Naturelles et Réactivité "Unité Associée au CNRST (URAC16)", Université Cadi Ayyad, Faculté des Sciences Semlalia, BP 2390, Bd My Abdellah, 40000 Marrakech, Morocco, and ^bLaboratoire de Chimie du Solide Appliquée, Faculté des Sciences, Université Mohammed V-Agdal, Avenue Ibn Battouta, BP 1014, Rabat, Morocco
^*Correspondence e-mail: berraho@uca.ma

(Received 26 March 2013; accepted 3 April 2013; online 13 April 2013)

The title compound, C₁₇H₂₄Br₂Cl₂, was synthesized from β-himachalene (3,5,5,9-tetramethyl-2,4a,5,6,7,8-hexahydro-1H-benzocycloheptene), which was isolated from the essential oil of the Atlas cedar (Cedrus Atlantica). The molecule contains fused six-, seven- and two three-membered rings. The six-membered ring has a half-chair conformation, while the seven-membered ring displays a boat conformation. The absolute structure was unambiguously established from anomalous dispersion effects. The crystal packing exhibits no short intermolecular contacts.

Related literature

For the crystal structures of related compounds, see: Ourhriss et al. (2013 ); Oukhrib et al. (2013a ,b ). For puckering parameters, see: Cremer & Pople (1975 ).

Experimental

Crystal data

C₁₇H₂₄Br₂Cl₂
M_r = 459.08
Monoclinic, P 2₁
a = 9.0112 (6) Å
b = 11.6772 (8) Å
c = 9.0849 (6) Å
β = 108.045 (5)°
V = 908.94 (11) Å³
Z = 2
Mo Kα radiation
μ = 4.75 mm⁻¹
T = 296 K
0.45 × 0.34 × 0.29 mm

Data collection

Bruker X8 APEX diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2008 ) T_min = 0.739, T_max = 0.867
6676 measured reflections
3720 independent reflections
2910 reflections with I > 2σ(I)
R_int = 0.034

Refinement

R[F² > 2σ(F²)] = 0.038
wR(F²) = 0.092
S = 1.03
3720 reflections
190 parameters
1 restraint
H-atom parameters constrained
Δρ_max = 0.64 e Å⁻³
Δρ_min = −0.79 e Å⁻³
Absolute structure: Flack & Bernardinelli (2000 ), 1096 Friedel pairs
Flack parameter: 0.039 (10)

Data collection: APEX2 (Bruker, 2009 ); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012 ); software used to prepare material for publication: PLATON (Spek, 2009 ) and publCIF (Westrip, 2010 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S1600536813009070/cv5397sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536813009070/cv5397Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S1600536813009070/cv5397Isup3.cml

checkCIF report

Comment top

As a continuation of our structural study of β-himachalene derivatives isolated from the essential oil of the Atlas cedar (Cedrus Atlantica) (Ourhriss et al., 2013; Oukhrib et al., 2013a,b), we present here the crystal structure of the title compound, (1S,3R,8R,9S,11R)-2,2-dibromo-10,10-dichloro-3,7,7,11- tetramethyltetracyclo[6.5.0.0^1,3.0^9,11]tridecane, (I).

In (I) (Fig. 1), the molecule contains a fused six- and seven-membered rings, which are fused to two three-membered rings. The six-membered ring has a half chair conformation as indicated by the total puckering amplitude QT = 0.446 (5) Å and spherical polar angle θ = 140.8 (6)° and φ2 = 143 (1)°, whereas the seven-membered ring displays a boat conformation with QT = 1.122 (5) Å, θ2 = 87.4 (3)°, φ2 = -48.2 (3)° and φ3 = -118 (5)° (Cremer & Pople, 1975). The three-membered rings (C1/C2/C3) and (C9/C10/C11) are nearly perpendicular to the six and seven-membered rings (C1/C8–C13)and (C1/C3–C8), with a dihedral angles of 84.1 (4) and 80.6 (4), respectively. Owing to the presence of Br and Cl atoms, the absolute configuration could be fully confirmed from anomalous dispersion effects, by refining the Flack parameter as C1(S),C3(R),C8(R),C9(S), and C11(R). The crystal packing exhibits no short intermolecular contacts.

Related literature top

For the crystal structures of related compounds, see: Ourhriss et al. (2013); Oukhrib et al. (2013a,b). For puckering parameters, see: Cremer & Pople (1975).

Experimental top

A solution containing 4 g (10 mmol) of (1S,3R,8S)-2,2-dibromo- 3,7,7,10- tetramethyltricyclo[6.4.0.01,3]dodec-9-ene and 1 ml (12.4 mmol) of CHCl₃ in 40 ml of dichloromethane was added dropwise at 273 K over 30 min to 1 g (25 mmol) of pulverized sodium hydroxide and 40 mg of N–benzyltriethylam monium chloride placed in a 100 ml three–necked flask. After stirring at room temperature for 2 h, the mixture was filtered on celite and concentrated in vacuum. The residue obtained was chromatographed on silicagel column impregnated with silver nitrate (10%) with a mixture of hexane - ethyl acetate (96–4) used as eluent. The two diastereoisomers (1S,3R,8S,9S,11R)- 2,2-Dibromo-10,10-dichloro-3,7,7,11-tetramethyltetracyclo[6.5.0.0^1,3.0 ^9,11]tridecane(X) and its isomer (1S,3R,8S,9R,11S)-2,2-Dibromo-10,10- dichloro-3,7,7,11-tetramethyltetracyclo[6.5.0.0^1,3.0^9,11]tridecane(Y) were obtained by this procedure in a 80/20 ratio and a combined yield of 65% (3 g; 6.5 mmol). The title compound (isomer X) was recrystallized from hexane.

Structure description top

For the crystal structures of related compounds, see: Ourhriss et al. (2013); Oukhrib et al. (2013a,b). For puckering parameters, see: Cremer & Pople (1975).

Computing details top

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: PLATON (Spek, 2009) and publCIF (Westrip, 2010).

Figures top

Fig. 1. : Molecular structure of the title compound with the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability. level. H atoms are represented as small spheres of arbitrary radii.

(1S,3R,8R,9S,11R)-2,2-Dibromo-10,10-dichloro-3,7,7,11-tetramethyltetracyclo[6.5.0.0^1,3.0^9,11]tridecane top

Crystal data top

C₁₇H₂₄Br₂Cl₂	F(000) = 460
M_r = 459.08	D_x = 1.677 Mg m⁻³
Monoclinic, P2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2yb	Cell parameters from 3720 reflections
a = 9.0112 (6) Å	θ = 2.8–29.6°
b = 11.6772 (8) Å	µ = 4.75 mm⁻¹
c = 9.0849 (6) Å	T = 296 K
β = 108.045 (5)°	Block, colourless
V = 908.94 (11) Å³	0.45 × 0.34 × 0.29 mm
Z = 2

Data collection top

Bruker X8 APEX diffractometer	3720 independent reflections
Radiation source: fine-focus sealed tube	2910 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.034
φ and ω scans	θ_max = 29.6°, θ_min = 2.8°
Absorption correction: multi-scan (SADABS; Sheldrick, 2008)	h = −12→12
T_min = 0.739, T_max = 0.867	k = −16→15
6676 measured reflections	l = −12→12

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)] = 0.038	H-atom parameters constrained
wR(F²) = 0.092	w = 1/[σ²(F_o²) + (0.0333P)²] where P = (F_o² + 2F_c²)/3
S = 1.03	(Δ/σ)_max = 0.001
3720 reflections	Δρ_max = 0.64 e Å⁻³
190 parameters	Δρ_min = −0.79 e Å⁻³
1 restraint	Absolute structure: Flack & Bernardinelli (2000), 1096 Friedel pairs
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: 0.039 (10)

Crystal data top

C₁₇H₂₄Br₂Cl₂	V = 908.94 (11) Å³
M_r = 459.08	Z = 2
Monoclinic, P2₁	Mo Kα radiation
a = 9.0112 (6) Å	µ = 4.75 mm⁻¹
b = 11.6772 (8) Å	T = 296 K
c = 9.0849 (6) Å	0.45 × 0.34 × 0.29 mm
β = 108.045 (5)°

Data collection top

Bruker X8 APEX diffractometer	3720 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 2008)	2910 reflections with I > 2σ(I)
T_min = 0.739, T_max = 0.867	R_int = 0.034
6676 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.038	H-atom parameters constrained
wR(F²) = 0.092	Δρ_max = 0.64 e Å⁻³
S = 1.03	Δρ_min = −0.79 e Å⁻³
3720 reflections	Absolute structure: Flack & Bernardinelli (2000), 1096 Friedel pairs
190 parameters	Absolute structure parameter: 0.039 (10)
1 restraint

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
C1	0.8734 (5)	0.4080 (3)	0.7265 (5)	0.0211 (8)
C2	0.9989 (5)	0.3302 (4)	0.6990 (6)	0.0288 (10)
C3	1.0234 (4)	0.3775 (4)	0.8568 (5)	0.0275 (9)
C4	1.0081 (6)	0.2965 (4)	0.9812 (5)	0.0357 (11)
H4A	1.1102	0.2657	1.0363	0.043*
H4B	0.9413	0.2330	0.9329	0.043*
C5	0.9408 (6)	0.3542 (5)	1.0962 (6)	0.0442 (13)
H5A	1.0232	0.3954	1.1721	0.053*
H5B	0.9014	0.2960	1.1507	0.053*
C6	0.8095 (6)	0.4372 (5)	1.0187 (5)	0.0387 (12)
H6A	0.8567	0.5027	0.9849	0.046*
H6B	0.7670	0.4645	1.0981	0.046*
C7	0.6702 (5)	0.3992 (4)	0.8798 (5)	0.0301 (9)
C8	0.7181 (4)	0.3573 (3)	0.7345 (5)	0.0206 (8)
H8	0.7319	0.2741	0.7439	0.025*
C9	0.5812 (4)	0.3798 (4)	0.5883 (4)	0.0224 (8)
H9	0.4807	0.3749	0.6086	0.027*
C10	0.5657 (5)	0.3530 (4)	0.4239 (5)	0.0261 (9)
C11	0.5826 (5)	0.4755 (4)	0.4748 (5)	0.0278 (9)
C12	0.7378 (6)	0.5328 (4)	0.4939 (6)	0.0373 (11)
H12A	0.7190	0.6125	0.4639	0.045*
H12B	0.7856	0.4970	0.4234	0.045*
C13	0.8528 (5)	0.5277 (3)	0.6570 (5)	0.0277 (9)
H13A	0.9534	0.5556	0.6546	0.033*
H13B	0.8168	0.5784	0.7235	0.033*
C14	1.1485 (6)	0.4682 (5)	0.9207 (7)	0.0432 (13)
H14A	1.1495	0.4896	1.0230	0.065*
H14B	1.1262	0.5343	0.8546	0.065*
H14C	1.2486	0.4377	0.9247	0.065*
C15	0.5843 (6)	0.2992 (5)	0.9266 (6)	0.0453 (13)
H15A	0.4981	0.2763	0.8394	0.068*
H15B	0.5463	0.3228	1.0096	0.068*
H15C	0.6547	0.2360	0.9601	0.068*
C16	0.5593 (6)	0.5035 (5)	0.8432 (6)	0.0419 (12)
H16A	0.6113	0.5673	0.8140	0.063*
H16B	0.5305	0.5232	0.9333	0.063*
H16C	0.4673	0.4849	0.7596	0.063*
C17	0.4417 (7)	0.5546 (4)	0.4175 (7)	0.0479 (14)
H17A	0.4693	0.6299	0.4593	0.072*
H17B	0.3576	0.5255	0.4506	0.072*
H17C	0.4095	0.5581	0.3065	0.072*
Cl1	0.37818 (14)	0.30587 (10)	0.30591 (14)	0.0415 (3)
Cl2	0.70977 (16)	0.28463 (12)	0.36234 (14)	0.0429 (3)
Br1	1.11977 (6)	0.38295 (6)	0.57096 (7)	0.05382 (18)
Br2	0.97449 (6)	0.16666 (4)	0.66883 (6)	0.04537 (16)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.0167 (18)	0.022 (2)	0.023 (2)	−0.0038 (15)	0.0039 (16)	−0.0013 (15)
C2	0.019 (2)	0.034 (2)	0.033 (3)	−0.0019 (17)	0.0085 (19)	−0.0011 (18)
C3	0.0185 (18)	0.035 (2)	0.028 (2)	0.005 (2)	0.0054 (17)	0.004 (2)
C4	0.028 (2)	0.049 (3)	0.024 (2)	0.003 (2)	−0.0001 (19)	0.003 (2)
C5	0.044 (3)	0.066 (4)	0.021 (3)	−0.004 (3)	0.007 (2)	−0.002 (2)
C6	0.038 (3)	0.057 (3)	0.023 (3)	−0.001 (2)	0.013 (2)	−0.010 (2)
C7	0.029 (2)	0.038 (2)	0.028 (2)	0.0027 (19)	0.0153 (19)	−0.004 (2)
C8	0.0199 (18)	0.0217 (19)	0.022 (2)	0.0009 (15)	0.0096 (17)	0.0021 (15)
C9	0.0205 (18)	0.0241 (18)	0.024 (2)	−0.0013 (18)	0.0093 (16)	0.0001 (18)
C10	0.022 (2)	0.035 (2)	0.019 (2)	0.0020 (17)	0.0027 (17)	0.0016 (16)
C11	0.029 (2)	0.028 (2)	0.023 (2)	0.0031 (18)	0.0021 (19)	0.0076 (17)
C12	0.035 (3)	0.030 (2)	0.043 (3)	−0.006 (2)	0.007 (2)	0.011 (2)
C13	0.022 (2)	0.022 (2)	0.037 (3)	−0.0034 (17)	0.0067 (19)	0.0028 (18)
C14	0.023 (2)	0.054 (3)	0.047 (3)	−0.008 (2)	0.004 (2)	−0.005 (2)
C15	0.043 (3)	0.068 (3)	0.033 (3)	−0.005 (3)	0.024 (3)	0.004 (3)
C16	0.036 (3)	0.051 (3)	0.044 (3)	0.011 (2)	0.019 (3)	−0.008 (2)
C17	0.042 (3)	0.038 (3)	0.053 (3)	0.012 (2)	−0.001 (3)	0.003 (2)
Cl1	0.0330 (6)	0.0449 (7)	0.0341 (7)	−0.0066 (5)	−0.0077 (5)	−0.0011 (5)
Cl2	0.0438 (7)	0.0613 (8)	0.0262 (6)	0.0125 (6)	0.0144 (5)	−0.0040 (5)
Br1	0.0336 (3)	0.0840 (4)	0.0516 (3)	−0.0014 (3)	0.0244 (3)	0.0083 (3)
Br2	0.0452 (3)	0.0386 (2)	0.0525 (3)	0.0134 (3)	0.0156 (3)	−0.0033 (3)

Geometric parameters (Å, º) top

C1—C13	1.522 (6)	C9—C11	1.524 (6)
C1—C2	1.530 (6)	C9—H9	0.9800
C1—C3	1.537 (5)	C10—C11	1.496 (6)
C1—C8	1.542 (5)	C10—Cl2	1.756 (4)
C2—C3	1.488 (6)	C10—Cl1	1.785 (4)
C2—Br1	1.924 (4)	C11—C12	1.511 (6)
C2—Br2	1.932 (4)	C11—C17	1.525 (7)
C3—C4	1.513 (6)	C12—C13	1.524 (7)
C3—C14	1.524 (7)	C12—H12A	0.9700
C4—C5	1.519 (7)	C12—H12B	0.9700
C4—H4A	0.9700	C13—H13A	0.9700
C4—H4B	0.9700	C13—H13B	0.9700
C5—C6	1.523 (7)	C14—H14A	0.9600
C5—H5A	0.9700	C14—H14B	0.9600
C5—H5B	0.9700	C14—H14C	0.9600
C6—C7	1.544 (6)	C15—H15A	0.9600
C6—H6A	0.9700	C15—H15B	0.9600
C6—H6B	0.9700	C15—H15C	0.9600
C7—C15	1.531 (7)	C16—H16A	0.9600
C7—C16	1.545 (7)	C16—H16B	0.9600
C7—C8	1.587 (5)	C16—H16C	0.9600
C8—C9	1.529 (6)	C17—H17A	0.9600
C8—H8	0.9800	C17—H17B	0.9600
C9—C10	1.490 (6)	C17—H17C	0.9600

C13—C1—C2	118.6 (3)	C10—C9—H9	111.8
C13—C1—C3	119.8 (3)	C11—C9—H9	111.8
C2—C1—C3	58.1 (3)	C8—C9—H9	111.8
C13—C1—C8	112.1 (3)	C9—C10—C11	61.4 (3)
C2—C1—C8	120.5 (3)	C9—C10—Cl2	124.4 (3)
C3—C1—C8	118.0 (3)	C11—C10—Cl2	121.3 (3)
C3—C2—C1	61.2 (3)	C9—C10—Cl1	116.4 (3)
C3—C2—Br1	121.4 (3)	C11—C10—Cl1	117.8 (3)
C1—C2—Br1	119.6 (3)	Cl2—C10—Cl1	108.9 (2)
C3—C2—Br2	118.7 (3)	C10—C11—C12	117.4 (4)
C1—C2—Br2	123.5 (3)	C10—C11—C9	59.1 (3)
Br1—C2—Br2	106.9 (2)	C12—C11—C9	116.6 (4)
C2—C3—C4	117.9 (4)	C10—C11—C17	118.6 (4)
C2—C3—C14	119.7 (4)	C12—C11—C17	114.5 (4)
C4—C3—C14	112.2 (4)	C9—C11—C17	119.7 (4)
C2—C3—C1	60.7 (3)	C11—C12—C13	114.9 (4)
C4—C3—C1	117.3 (3)	C11—C12—H12A	108.5
C14—C3—C1	120.2 (4)	C13—C12—H12A	108.5
C3—C4—C5	112.6 (4)	C11—C12—H12B	108.5
C3—C4—H4A	109.1	C13—C12—H12B	108.5
C5—C4—H4A	109.1	H12A—C12—H12B	107.5
C3—C4—H4B	109.1	C1—C13—C12	113.5 (4)
C5—C4—H4B	109.1	C1—C13—H13A	108.9
H4A—C4—H4B	107.8	C12—C13—H13A	108.9
C4—C5—C6	112.5 (4)	C1—C13—H13B	108.9
C4—C5—H5A	109.1	C12—C13—H13B	108.9
C6—C5—H5A	109.1	H13A—C13—H13B	107.7
C4—C5—H5B	109.1	C3—C14—H14A	109.5
C6—C5—H5B	109.1	C3—C14—H14B	109.5
H5A—C5—H5B	107.8	H14A—C14—H14B	109.5
C5—C6—C7	120.9 (4)	C3—C14—H14C	109.5
C5—C6—H6A	107.1	H14A—C14—H14C	109.5
C7—C6—H6A	107.1	H14B—C14—H14C	109.5
C5—C6—H6B	107.1	C7—C15—H15A	109.5
C7—C6—H6B	107.1	C7—C15—H15B	109.5
H6A—C6—H6B	106.8	H15A—C15—H15B	109.5
C15—C7—C6	110.2 (4)	C7—C15—H15C	109.5
C15—C7—C16	108.2 (4)	H15A—C15—H15C	109.5
C6—C7—C16	104.9 (4)	H15B—C15—H15C	109.5
C15—C7—C8	106.7 (4)	C7—C16—H16A	109.5
C6—C7—C8	114.0 (3)	C7—C16—H16B	109.5
C16—C7—C8	112.8 (4)	H16A—C16—H16B	109.5
C9—C8—C1	113.2 (3)	C7—C16—H16C	109.5
C9—C8—C7	108.4 (3)	H16A—C16—H16C	109.5
C1—C8—C7	113.9 (3)	H16B—C16—H16C	109.5
C9—C8—H8	107.0	C11—C17—H17A	109.5
C1—C8—H8	107.0	C11—C17—H17B	109.5
C7—C8—H8	107.0	H17A—C17—H17B	109.5
C10—C9—C11	59.5 (3)	C11—C17—H17C	109.5
C10—C9—C8	129.4 (3)	H17A—C17—H17C	109.5
C11—C9—C8	122.7 (3)	H17B—C17—H17C	109.5

Experimental details

Crystal data
Chemical formula	C₁₇H₂₄Br₂Cl₂
M_r	459.08
Crystal system, space group	Monoclinic, P2₁
Temperature (K)	296
a, b, c (Å)	9.0112 (6), 11.6772 (8), 9.0849 (6)
β (°)	108.045 (5)
V (Å³)	908.94 (11)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	4.75
Crystal size (mm)	0.45 × 0.34 × 0.29

Data collection
Diffractometer	Bruker X8 APEX
Absorption correction	Multi-scan (SADABS; Sheldrick, 2008)
T_min, T_max	0.739, 0.867
No. of measured, independent and observed [I > 2σ(I)] reflections	6676, 3720, 2910
R_int	0.034
(sin θ/λ)_max (Å⁻¹)	0.694

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.038, 0.092, 1.03
No. of reflections	3720
No. of parameters	190
No. of restraints	1
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.64, −0.79
Absolute structure	Flack & Bernardinelli (2000), 1096 Friedel pairs
Absolute structure parameter	0.039 (10)

Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 2012), PLATON (Spek, 2009) and publCIF (Westrip, 2010).

Acknowledgements

The authors thank the Unit of Support for Technical and Scientific Research (UATRS, CNRST) for the X-ray measurements.

References

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