2,8-Dibromo-4,10-dichloro-6H,12H-5,11-methano­dibenzo[b,f][1,5]diazo­cine

Zhu, K.-X.; Craig, D.C.; Try, A.C.

doi:10.1107/S1600536808026226

organic compounds

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ISSN: 2056-9890

Volume 64| Part 9| September 2008| Page o1797

doi:10.1107/S1600536808026226

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2,8-Dibromo-4,10-dichloro-6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine

Kai-Xian Zhu,^a Donald C. Craig ^b and Andrew C. Try ^a ^*

^aDepartment of Chemistry and Biomolecular Sciences, Building F7B, Macquarie University, Sydney, NSW 2109, Australia, and ^bSchool of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
^*Correspondence e-mail: andrew.try@mq.edu.au

(Received 31 July 2008; accepted 14 August 2008; online 20 August 2008)

The title compound, C₁₅H₁₀Br₂Cl₂N₂, a 2,8-dibromo-4,10-dichloro Tröger's base analogue derived from 4-bromo-2-chloroaniline, has a dihedral angle of 110.9 (10)° between the two aryl rings, the largest yet measured for a simple dibenzo analogue.

Related literature

For related literature on the synthesis and crystal structures of dihalogenated Tröger's base analogues, see: Jensen & Wärnmark (2001 ); Faroughi et al. (2006a , 2007a ,b ). For Tröger's base analogues substituted with multiple electron-withdrawing groups, see: Faroughi et al. (2006b ); Bhuiyan et al. (2006 , 2007 ); Vande Velde et al. (2008 ). For reactions of halogenated Tröger's base analogues, see: Jensen et al. (2002 ); Hof et al. (2005 ). For literature on racemization of Tröger's base analogues and the effect of substituents ortho to the diazocine N atoms, see: Lenev et al. (2006 ).

Experimental

Crystal data

C₁₅H₁₀Br₂Cl₂N₂
M_r = 449.0
Orthorhombic, P c a 2₁
a = 7.910 (2) Å
b = 12.601 (3) Å
c = 15.230 (4) Å
V = 1518.0 (7) Å³
Z = 4
Mo Kα radiation
μ = 5.64 mm⁻¹
T = 294 K
0.30 × 0.12 × 0.07 mm

Data collection

Enraf–Nonius CAD-4 diffractometer
Absorption correction: analytical (de Meulenaer & Tompa, 1965 ) T_min = 0.52, T_max = 0.69
1394 measured reflections
1394 independent reflections
1028 reflections with I > 2σ(I)
1 standard reflection frequency: 30 min intensity decay: none

Refinement

R[F² > 2σ(F²)] = 0.056
wR(F²) = 0.061
S = 1.61
1394 reflections
189 parameters
H-atom parameters constrained
Δρ_max = 0.98 e Å⁻³
Δρ_min = −1.02 e Å⁻³
Absolute structure: Flack (1983 )
Flack parameter: 0.09 (2)

Data collection: CAD-4 (Schagen et al., 1989 ); cell refinement: CAD-4; data reduction: local program; program(s) used to solve structure: SIR92 (Altomare et al., 1994 ); program(s) used to refine structure: RAELS (Rae, 1996 ); molecular graphics: ORTEPII (Johnson, 1976 ); software used to prepare material for publication: local programs.

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808026226/tk2290sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536808026226/tk2290Isup2.hkl

checkCIF report

Comment top

Tröger's base analogues bearing electron-withdrawing groups were long thought to be difficult, if not impossible, to prepare. However, the synthesis of dihalogenated (Jensen & Wärnmark, 2001), octafluoro (Vande Velde et al., 2008) and tetranitro (Bhuiyan et al., 2007) Tröger's base analogues highlight the possiblities that now exist in terms of incorporating electron-withdrawing groups on the starting anilines. The synthetic utility of halogen-substituted Tröger's base analogue has been demonstrated with their conversion to alkyne- (Jensen & Wärnmark, 2001; Jensen et al., 2002) and functionalized phenyl- (Hof et al., 2005) substituted analogues, among others. It is noteworthy that crystal structures of several other 2,4,8,10-tetrasubstituted Tröger's base analogues exhibit large dihedral angles that are close to that in (I). Tröger's base analogues are known to undergo racemization in acidic solution, however the presence of a substituent at the ortho-position, relative to the bridge nitrogen atoms, has been shown to increase the racemization barrier (Lenev et al., 2006).

The molecular structure of (I) is shown in Fig. 1 and it was prepared as outlined in Fig. 2.

Related literature top

For related literature on the synthesis and crystal structures of dihalogenated Tröger's base analogues, see: Jensen & Wärnmark (2001); Faroughi et al. (2006a, 2007a,b). For Tröger's base analogues substituted with multiple electron-withdrawing groups, see: Faroughi et al. (2006b); Bhuiyan et al. (2006, 2007); Vande Velde et al. (2008). For reactions of halogenated Tröger's base analogues, see: Jensen et al. (2002); Hof et al. (2005). For literature on racemization of Tröger's base analogues and the effect of substituents ortho to the diazocine N atoms, see: Lenev et al. (2006).

Experimental top

4-Bromo-2-chloroaniline (1 g, 4.84 mmol) and paraformaldehyde (232 mg, 7.74 mmol) were added to an ice-cold solution of trifluoroacetic acid (10 ml). The reaction mixture was then stirred in dark at room temperature for 7 days under an atmosphere of argon. The ice-cold reaction mixture was basified by the dropwise addition of a mixture of ammonia (28%, 20 ml) and water (40 ml), followed by the additon of a saturated sodium hydrogen carbonate solution (20 ml). The resultant mixture was then extracted with dichloromethane (3 x 20 ml) and the combined organic layers were washed with brine (40 ml), dried over anhydrous sodium sulfate, filtered and evaporated to dryness. The crude product was chromatographed (silica gel, dichloromethane:hexane 8:2) to afford 2,8-dibromo-4,10-dichloro-6H,12H-5,11-methanodibenzo [b,f][1,5]diazocine (I) (613 mg, 56%) as a white solid and as a racemic mixture: m.p. 471–472 K; ¹H NMR (400 MHz, CDCl₃) δ 4.21–4.33 (4H, m), 4.55 (2H, d, J 17.3 Hz), 7.04 (2H, d, J 2.1 Hz), 7.41 (2H, d, J 2.1 Hz); ¹³C NMR (100 MHz, CDCl₃) δ 54.37, 67.32, 117.15, 128.49, 130.17, 131.02, 131.71, 142.33. Analysis found: C 40.46; H 2.22; N 6.46; C₁₅H₁₀Br₂Cl₂N₂ requires C 40.13; H 2.25; N 6.24. Single crystals were obtained from slow evaporation from dichloromethane solution of (I).

Computing details top

Data collection: CAD-4 (Schagen et al., 1989); cell refinement: CAD-4 (Schagen et al., 1989); data reduction: local program; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: RAELS (Rae, 1996); molecular graphics: ORTEPII (Johnson, 1976); software used to prepare material for publication: local programs.

Figures top

	Fig. 1. ORTEPII (Johnson, 1976) plot of (I), with ellipsoids at the 10% probability level. H atoms are drawn as spheres of arbitrary radius.
	Fig. 2. Synthetic scheme for the synthesis of (I) showing the numbering system used in naming the compound.

2,8-Dibromo-4,10-dichloro-6H,12H-5,11- methanodibenzo[b,f][1,5]diazocine top

Crystal data top

C₁₅H₁₀Br₂Cl₂N₂	D_x = 1.96 Mg m⁻³
M_r = 449.0	Melting point: 471 K
Orthorhombic, Pca2₁	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2c -2ac	Cell parameters from 11 reflections
a = 7.910 (2) Å	θ = 10–11°
b = 12.601 (3) Å	µ = 5.64 mm⁻¹
c = 15.230 (4) Å	T = 294 K
V = 1518.0 (7) Å³	Prism, colourless
Z = 4	0.30 × 0.12 × 0.07 mm
F(000) = 872.0

Data collection top

Enraf–Nonius CAD-4 diffractometer	θ_max = 25°
ω–2θ scans	h = 0→9
Absorption correction: analytical de Meulenaer & Tompa (1965)	k = 0→14
T_min = 0.52, T_max = 0.69	l = −18→0
1394 measured reflections	1 standard reflections every 30 min
1394 independent reflections	intensity decay: none
1028 reflections with I > 2σ(I)

Refinement top

Refinement on F	w = 1/[σ²(F) + 0.0004F²]
R[F² > 2σ(F²)] = 0.056	(Δ/σ)_max = 0.002
wR(F²) = 0.061	Δρ_max = 0.98 e Å⁻³
S = 1.61	Δρ_min = −1.02 e Å⁻³
1394 reflections	Absolute structure: Flack (1983), 0 Friedel pairs
189 parameters	Absolute structure parameter: 0.09 (2)
H-atom parameters constrained

Crystal data top

C₁₅H₁₀Br₂Cl₂N₂	V = 1518.0 (7) Å³
M_r = 449.0	Z = 4
Orthorhombic, Pca2₁	Mo Kα radiation
a = 7.910 (2) Å	µ = 5.64 mm⁻¹
b = 12.601 (3) Å	T = 294 K
c = 15.230 (4) Å	0.30 × 0.12 × 0.07 mm

Data collection top

Enraf–Nonius CAD-4 diffractometer	1394 independent reflections
Absorption correction: analytical de Meulenaer & Tompa (1965)	1028 reflections with I > 2σ(I)
T_min = 0.52, T_max = 0.69	1 standard reflections every 30 min
1394 measured reflections	intensity decay: none

Refinement top

R[F² > 2σ(F²)] = 0.056	H-atom parameters constrained
wR(F²) = 0.061	Δρ_max = 0.98 e Å⁻³
S = 1.61	Δρ_min = −1.02 e Å⁻³
1394 reflections	Absolute structure: Flack (1983), 0 Friedel pairs
189 parameters	Absolute structure parameter: 0.09 (2)

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

	x	y	z	U_iso*/U_eq
Br1	0.8061 (2)	0.6867 (1)	0.3991 (1)	0.0585 (5)
Br2	0.2324 (2)	0.0800 (1)	0.0428 (2)	0.0527 (5)
Cl1	0.9770 (5)	0.5167 (4)	0.0779 (3)	0.057 (1)
Cl2	0.5654 (5)	0.0565 (3)	0.3603 (3)	0.052 (1)
N1	0.9460 (14)	0.3064 (10)	0.1658 (8)	0.041 (3)
N2	0.8319 (15)	0.1842 (9)	0.2739 (8)	0.044 (3)
C1	0.9798 (19)	0.2123 (12)	0.2198 (10)	0.044 (4)
C2	0.8998 (18)	0.3929 (12)	0.2193 (10)	0.043 (4)
C3	0.8445 (18)	0.3790 (11)	0.3054 (8)	0.041 (4)
C4	0.817 (2)	0.2693 (12)	0.3414 (8)	0.049 (4)
C5	0.6842 (19)	0.1696 (11)	0.2226 (9)	0.039 (4)
C6	0.6740 (19)	0.2086 (11)	0.1360 (9)	0.036 (4)
C7	0.8206 (17)	0.2753 (12)	0.0978 (9)	0.040 (4)
C8	0.9155 (17)	0.4984 (13)	0.1855 (9)	0.043 (4)
C9	0.8825 (19)	0.5861 (12)	0.2397 (11)	0.048 (4)
C10	0.839 (2)	0.5684 (13)	0.3247 (11)	0.050 (4)
C11	0.818 (2)	0.4666 (13)	0.3570 (10)	0.056 (4)
C12	0.5565 (17)	0.1082 (10)	0.2538 (8)	0.031 (3)
C13	0.4158 (17)	0.0854 (10)	0.2036 (8)	0.035 (3)
C14	0.4117 (17)	0.1221 (11)	0.1168 (9)	0.040 (4)
C15	0.5433 (19)	0.1819 (10)	0.0853 (9)	0.034 (3)
H1C1	1.0780	0.2273	0.2593	0.044
H2C1	1.0078	0.1513	0.1804	0.044
H1C4	0.7008	0.2660	0.3674	0.049
H2C4	0.9027	0.2559	0.3883	0.049
H1C7	0.7726	0.3410	0.0708	0.040
H2C7	0.8794	0.2326	0.0517	0.040
HC9	0.8906	0.6600	0.2162	0.048
HC11	0.7825	0.4567	0.4195	0.056
HC13	0.3194	0.0438	0.2286	0.035
HC15	0.5411	0.2061	0.0228	0.034

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.060 (1)	0.060 (1)	0.0549 (9)	−0.0011 (8)	−0.001 (1)	−0.0138 (9)
Br2	0.0470 (9)	0.0650 (9)	0.0461 (8)	−0.0118 (8)	−0.0026 (9)	−0.0091 (9)
Cl1	0.061 (3)	0.066 (3)	0.044 (2)	−0.019 (2)	0.010 (2)	0.000 (2)
Cl2	0.063 (3)	0.056 (2)	0.037 (2)	0.000 (2)	0.006 (2)	0.018 (2)
N1	0.029 (7)	0.058 (8)	0.037 (7)	0.001 (6)	0.002 (6)	−0.003 (6)
N2	0.046 (7)	0.048 (7)	0.038 (7)	0.004 (6)	−0.009 (6)	0.020 (6)
C1	0.029 (9)	0.067 (9)	0.036 (8)	0.005 (8)	−0.016 (7)	0.012 (8)
C2	0.051 (9)	0.043 (9)	0.034 (8)	0.009 (8)	0.020 (8)	−0.006 (7)
C3	0.045 (9)	0.059 (9)	0.019 (8)	−0.012 (8)	−0.004 (7)	−0.005 (7)
C4	0.083 (9)	0.053 (8)	0.013 (7)	0.004 (9)	−0.006 (7)	0.007 (7)
C5	0.048 (9)	0.043 (9)	0.026 (7)	0.000 (7)	0.013 (7)	0.007 (7)
C6	0.039 (8)	0.042 (8)	0.026 (8)	0.010 (8)	0.002 (6)	−0.006 (7)
C7	0.037 (8)	0.052 (9)	0.030 (8)	−0.007 (8)	0.007 (7)	−0.002 (7)
C8	0.029 (8)	0.062 (9)	0.039 (9)	−0.002 (8)	−0.002 (7)	0.004 (9)
C9	0.047 (9)	0.038 (9)	0.059 (9)	−0.010 (8)	−0.001 (8)	−0.007 (8)
C10	0.047 (9)	0.057 (9)	0.046 (9)	−0.005 (8)	0.017 (8)	−0.007 (8)
C11	0.085 (9)	0.052 (9)	0.029 (8)	−0.011 (9)	0.009 (9)	−0.007 (8)
C12	0.037 (8)	0.032 (8)	0.024 (7)	0.009 (7)	0.010 (6)	−0.002 (6)
C13	0.046 (9)	0.043 (9)	0.016 (6)	0.014 (8)	0.001 (6)	0.000 (7)
C14	0.029 (8)	0.039 (8)	0.052 (9)	0.006 (7)	0.010 (7)	−0.015 (8)
C15	0.034 (8)	0.039 (8)	0.027 (7)	0.004 (7)	0.009 (7)	−0.004 (7)

Geometric parameters (Å, º) top

Br1—C10	1.890 (15)	C4—H2C4	1.000
Br2—C14	1.888 (14)	C5—C6	1.410 (18)
Cl1—C8	1.724 (14)	C5—C12	1.358 (18)
Cl2—C12	1.750 (13)	C6—C7	1.55 (2)
N1—C1	1.468 (18)	C6—C15	1.333 (19)
N1—C2	1.409 (17)	C7—H1C7	1.000
N1—C7	1.487 (18)	C7—H2C7	1.000
N2—C1	1.474 (19)	C8—C9	1.40 (2)
N2—C4	1.491 (18)	C9—C10	1.357 (19)
N2—C5	1.417 (18)	C9—HC9	1.000
C1—H1C1	1.000	C10—C11	1.39 (2)
C1—H2C1	1.000	C11—HC11	1.000
C2—C3	1.394 (18)	C12—C13	1.381 (17)
C2—C8	1.43 (2)	C13—C14	1.402 (18)
C3—C4	1.50 (2)	C13—HC13	1.000
C3—C11	1.37 (2)	C14—C15	1.371 (19)
C4—H1C4	1.000	C15—HC15	1.000

C1—N1—C2	110.4 (12)	N1—C7—C6	112.5 (11)
C1—N1—C7	107.4 (11)	N1—C7—H1C7	108.7
C2—N1—C7	115.7 (11)	N1—C7—H2C7	108.7
C1—N2—C4	106.0 (11)	C6—C7—H1C7	108.7
C1—N2—C5	112.2 (11)	C6—C7—H2C7	108.7
C4—N2—C5	114.1 (12)	H1C7—C7—H2C7	109.5
N1—C1—N2	111.3 (11)	Cl1—C8—C2	119.3 (11)
N1—C1—H1C1	109.0	Cl1—C8—C9	120.4 (12)
N1—C1—H2C1	109.0	C2—C8—C9	120.2 (12)
N2—C1—H1C1	109.0	C8—C9—C10	118.6 (15)
N2—C1—H2C1	109.0	C8—C9—HC9	120.7
H1C1—C1—H2C1	109.5	C10—C9—HC9	120.7
N1—C2—C3	121.9 (14)	Br1—C10—C9	118.5 (13)
N1—C2—C8	119.2 (12)	Br1—C10—C11	120.0 (11)
C3—C2—C8	118.8 (13)	C9—C10—C11	121.4 (15)
C2—C3—C4	120.3 (13)	C3—C11—C10	121.6 (14)
C2—C3—C11	119.1 (14)	C3—C11—HC11	119.2
C4—C3—C11	120.6 (12)	C10—C11—HC11	119.2
N2—C4—C3	113.5 (10)	Cl2—C12—C5	120.5 (12)
N2—C4—H1C4	108.4	Cl2—C12—C13	117.9 (10)
N2—C4—H2C4	108.4	C5—C12—C13	121.6 (13)
C3—C4—H1C4	108.4	C12—C13—C14	118.2 (13)
C3—C4—H2C4	108.4	C12—C13—HC13	120.9
H1C4—C4—H2C4	109.5	C14—C13—HC13	120.9
N2—C5—C6	121.2 (13)	Br2—C14—C13	119.2 (11)
N2—C5—C12	119.6 (13)	Br2—C14—C15	121.0 (11)
C6—C5—C12	118.9 (15)	C13—C14—C15	119.6 (13)
C5—C6—C7	119.8 (13)	C6—C15—C14	121.6 (13)
C5—C6—C15	119.9 (14)	C6—C15—HC15	119.2
C7—C6—C15	120.1 (12)	C14—C15—HC15	119.2

C2—N1—C1—N2	57.5 (15)	C2—C3—C11—C10	2 (2)
C2—N1—C1—H1C1	−62.8	C2—C3—C11—HC11	−177.7
C2—N1—C1—H2C1	177.8	C4—C3—C11—C10	−178.6 (16)
C7—N1—C1—N2	−69.4 (15)	C4—C3—C11—HC11	1.4
C7—N1—C1—H1C1	170.3	N2—C5—C6—C7	−4 (2)
C7—N1—C1—H2C1	50.8	N2—C5—C6—C15	171.2 (13)
C1—N1—C2—C3	−18.2 (18)	C12—C5—C6—C7	−177.9 (12)
C1—N1—C2—C8	159.5 (13)	C12—C5—C6—C15	−2 (2)
C7—N1—C2—C3	103.9 (16)	N2—C5—C12—Cl2	5.4 (18)
C7—N1—C2—C8	−78.3 (17)	N2—C5—C12—C13	−175.2 (12)
C1—N1—C7—C6	44.6 (15)	C6—C5—C12—Cl2	179.1 (10)
C1—N1—C7—H1C7	165.1	C6—C5—C12—C13	−2 (2)
C1—N1—C7—H2C7	−75.8	C5—C6—C7—N1	−10.2 (17)
C2—N1—C7—C6	−79.1 (15)	C5—C6—C7—H1C7	−130.7
C2—N1—C7—H1C7	41.3	C5—C6—C7—H2C7	110.2
C2—N1—C7—H2C7	160.4	C15—C6—C7—N1	174.2 (13)
C4—N2—C1—N1	−69.8 (13)	C15—C6—C7—H1C7	53.8
C4—N2—C1—H1C1	50.5	C15—C6—C7—H2C7	−65.3
C4—N2—C1—H2C1	169.9	C5—C6—C15—C14	4 (2)
C5—N2—C1—N1	55.3 (16)	C5—C6—C15—HC15	−176.1
C5—N2—C1—H1C1	175.6	C7—C6—C15—C14	179.5 (12)
C5—N2—C1—H2C1	−65.0	C7—C6—C15—HC15	−0.5
C1—N2—C4—C3	42.4 (15)	Cl1—C8—C9—C10	−178.1 (12)
C1—N2—C4—H1C4	163.0	Cl1—C8—C9—HC9	1.9
C1—N2—C4—H2C4	−78.2	C2—C8—C9—C10	1 (2)
C5—N2—C4—C3	−81.5 (16)	C2—C8—C9—HC9	−178.6
C5—N2—C4—H1C4	39.1	C8—C9—C10—Br1	176.8 (11)
C5—N2—C4—H2C4	157.9	C8—C9—C10—C11	−4 (3)
C1—N2—C5—C6	−17.3 (19)	HC9—C9—C10—Br1	−3.2
C1—N2—C5—C12	156.2 (13)	HC9—C9—C10—C11	176.3
C4—N2—C5—C6	103.2 (14)	Br1—C10—C11—C3	−178.6 (12)
C4—N2—C5—C12	−83.3 (16)	Br1—C10—C11—HC11	1.4
N1—C2—C3—C4	−6 (2)	C9—C10—C11—C3	2 (3)
N1—C2—C3—C11	173.3 (14)	C9—C10—C11—HC11	−178.1
C8—C2—C3—C4	176.4 (14)	Cl2—C12—C13—C14	−176.9 (10)
C8—C2—C3—C11	−4 (2)	Cl2—C12—C13—HC13	3.1
N1—C2—C8—Cl1	4.3 (19)	C5—C12—C13—C14	3.7 (19)
N1—C2—C8—C9	−175.2 (13)	C5—C12—C13—HC13	−176.3
C3—C2—C8—Cl1	−177.9 (11)	C12—C13—C14—Br2	173.5 (9)
C3—C2—C8—C9	3 (2)	C12—C13—C14—C15	−2.1 (18)
C2—C3—C4—N2	−8 (2)	HC13—C13—C14—Br2	−6.5
C2—C3—C4—H1C4	−128.1	HC13—C13—C14—C15	177.9
C2—C3—C4—H2C4	113.1	Br2—C14—C15—C6	−177.3 (11)
C11—C3—C4—N2	173.3 (14)	Br2—C14—C15—HC15	2.7
C11—C3—C4—H1C4	52.7	C13—C14—C15—C6	−2 (2)
C11—C3—C4—H2C4	−66.1	C13—C14—C15—HC15	178.3

Experimental details

Crystal data
Chemical formula	C₁₅H₁₀Br₂Cl₂N₂
M_r	449.0
Crystal system, space group	Orthorhombic, Pca2₁
Temperature (K)	294
a, b, c (Å)	7.910 (2), 12.601 (3), 15.230 (4)
V (Å³)	1518.0 (7)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	5.64
Crystal size (mm)	0.30 × 0.12 × 0.07

Data collection
Diffractometer	Enraf–Nonius CAD-4 diffractometer
Absorption correction	Analytical de Meulenaer & Tompa (1965)
T_min, T_max	0.52, 0.69
No. of measured, independent and observed [I > 2σ(I)] reflections	1394, 1394, 1028
R_int	?
(sin θ/λ)_max (Å⁻¹)	0.595

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.056, 0.061, 1.61
No. of reflections	1394
No. of parameters	189
No. of restraints	?
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.98, −1.02
Absolute structure	Flack (1983), 0 Friedel pairs
Absolute structure parameter	0.09 (2)

Computer programs: CAD-4 (Schagen et al., 1989), SIR92 (Altomare et al., 1994), RAELS (Rae, 1996), ORTEPII (Johnson, 1976), local programs.

Acknowledgements

The authors thank Macquarie University for the award of a Macquarie University Research Development Grant to ACT.

References

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