trans-4-Bromo-ONN-azoxy­benzene at 100 K

The crystal structure of the α isomer of trans-4-bromo­azoxy­benzene [systematic name: trans-1-(bromophenyl)-2-phenyl­diazene 2-oxide], C₁₂H₉BrN₂O, has been determined by X-ray dif­frac­tion. The geometries of the two mol­ecules in the asymmetric unit are slightly different and are within ∼0.02 Å for bond lengths, ∼2° for angles and ∼3° for torsion angles. The azoxy bridges in both mol­ecules have the typical geometry observed for trans-azoxy­benzenes. The crystal network contains two types of planar mol­ecules arranged in columns. The torsion angles along the Ar—N bonds are only 7 (2)°, on either side of the azoxy group.

S1. Comment

The commonly used methods for the preparation of unsymmetrical azoxybenzenes suffer from a lack of selectivity. Condensation and oxidation reactions provide, in every case, mixtures of isomers differing in the position of the O atom with respect to the substituents bound to the benzene rings. It has been claimed (Angeli & Valori, 1912) that bromination of azoxybenzene provides only one isomer, viz. α-4-bromoazoxybenzene (the title compound); at that time, the result was important evidence for the unsymmetrical structure of the azoxy bridge. Since then, the reaction has played an important role in mechanistic investigations of the Wallach rearrangement, since it was the only tool for recognizing the distribution of tracers with ¹⁵N– and ¹⁴C-labelled substrates (Shemyakin et al., 1958; Behr & Hendley, 1966). We now confirm the Angeli & Valori (1912) statement; bromination of azoxybenzene occurs with difficulty but selectively; another (β) isomer is not formed at all. α-4-Bromoazoxybenzene seems to be a good model compound for investigations of the structure of the azoxy bridge.

There are two independent molecules of the title compound in the unit cell (A and B; Fig. 1). The geometries of the molecules are similar; differences do not exceed 0.02 Å for bond lengths (e.g. N1A—C1A' and N1B—C1B'), 2° for valence angles (e.g. O1A—N1A—C1A' and O1B—N1B—C1B') and 3° for torsion angles (e.g. N1A—N2A—C1A—C2A and N1B—N2B—C1B—C2B). Both molecules are almost planar; this is the preferential conformation of the azoxybenzene molecules. However, the rotation energy barrier is only 13 kJ mol⁻¹ on the unoxidized side and 23 kJ mol⁻¹ on the other (Tsuji et al., 2000). In solution, the rotation is fast enough to make the C atoms at, for example, the C2A– and C6A-atom positions, magnetically equivalent (Domański & Kyzioł, 2001). The twist angles along the C_aryl—N bonds are −7.3 (4) and 5.9 (5)° for A, and 5.2 (4) and −8.7 (5)° for B. The planarity of the molecules can also be described by the dihedral angles of three planar fragments, viz. the benzene ring, I, connected to the oxidized N atom (N1A and N1B), the azoxy group, II, and the other benzene ring, III. The dihedral angles between these groups are 7.7 (5) (I/II), 5.2 (6) (II/III) and 2.5 (2)° (I/III) for A, and 6.2 (5), 7.3 (5) and 1.7 (2)° for B. Atom C1A (or C1B) lies in plane II. The C—N bond lengths on the oxidized side of the bridge are ca 0.03 (for A) and 0.07 Å (for B) longer than the C—N bond lengths on the unoxidized side. The valence angles of the bridge are typical for trigonal hybridization of the C and N atoms. Some deviations are observed for both molecules in the C—C—N angles on the unoxidized side of the azoxy group, as a result of steric hindrance around the azoxy group. Analogously, the N—N—O valence angles are widened to nearly 130° in order to keep atom O1A (O1B) far from the H atom bound to atom C2A (C2B). The non-valence O···H distances are 2.34 (to H2') and 2.15 (2) Å (to H2) in A, and 2.38 (to H22') and 2.19 Å (to H22) in B. These distances are shorter than the sum of the van der Waals radii (2.6 Å) given by Pauling (1967). These are typical features observed in the molecular structure of the trans-azoxybenzenes (Krigbaum & Barber, 1971; Krigbaum & Taga, 1974; Hoesch & Weber, 1977; Ejsmont et al., 2000; Domański et al., 2001; Ejsmont et al., 2002). All atoms bonded to N1A (N1B) lie in the same plane within 0.017 (5) Å for C1A' and 0.038 (6) Å for C1B'. The C—Br bond lengths are comparable to that found in the molecule of 4,4'-dibromoazobenzene (Howard et al., 1994).

It is well known that isomerization of cis-azoxybenzenes occurs with great ease, e.g. cis-4-methyl-azoxybenzenes are spontaneously transformed into trans isomers in the dark, at room temperature (Webb & Jaffé, 1964). This fact should be easily explicable if the N—N bond order is significantly lower than it is in azobenzenes. Such a difference should be reflected in the N—N bond lengths, but the estimation of this distance appears to be rather difficult. The symmetrically 4,4'-disubstituted azoxybenzenes were examined several times; the N—N distances reported varied between 1.155 (6) and 1.276 (6) Å (Krigbaum & Barber, 1971; Sciau et al., 1988), indicating high bond order, but the large differences make a comparison with azobenzenes unreliable. The results of measurements are influenced by the orientational disorder in the crystal networks, but librations within the azoxy bridge may also play a role, as observed in the case of trans-stilbenes. In mono-substituted azoxybenzenes, the N—N bond lengths do not differ significantly from that observed in A and B (e.g. Ejsmont et al., 2002). However, repeated measurements at room temperature gave lower values [1.221 (6) and 1.248 (5) Å] for 4-bromo-NNO-azoxybenzene. The apparent shortening of the N—N bond at higher temperature probably results from the molecular motions. Restricted rotation along the Ar—N bond in the crystal network may cause torsion vibrations within the azoxy group. In the crystal network, the molecules of compound (I) are arranged in columns (Fig. 2). The distance between neighbouring molecules in the column is 3.939 (4) Å. Strong intermolecular interactions were not found in the crystals, which fact may influence the planar conformation of trans-4-bromoazoxybenzene molecules.

Intramolecular hydrogen bonding and contact geometry

S2. Experimental

To a stirred solution of azoxybenzene (3.96 g, 0.02 mol) in acetic acid (50 ml), elemental bromine (2.14 ml, 0.04 mol) was added slowly. The mixture was stirred for 4 h at 323 K and left to stand overnight at room temperature. The solution was poured into cold water (250 ml). Sodium hydrogen sulphite (40% aqueous solution) was added dropwise until the colour changed from brown. A yellow precipitate was collected by filtration and crystallized twice from methanol. 4-Bromo-ONN-azoxybenzene (3.88 g, 70%) was obtained as colourless needles (m.p. 346–347 K) suitable for a X-ray diffraction studies. MS, m/z (int.): 278 (49), 276 (M⁺, 50), 249 (6), 247 (6), 169 (38), 157 (23), 155 (24), 145 (8), 143 (8), 91 (22), 90 (29), 77 (100); IR (KBr, cm⁻¹): 1480, 1324 (stretching vibrations of the azoxy group); ¹H-NMR (CDCl₃): δ 8.23–8.32 (m, 2H, aromatic protons of the mono-substituted ring), 8.07 (d³J = 8.5 Hz, 2H, 3,5-protons), 7.58 (d³J = 8.5 Hz, 2H, 2,6-protons), 7.24–7.49 (m, 3H, remaining aromatic protons); ¹³C NMR (DMSO-d₆): δ 147.6 (C1'), 142.5 (C1), 132.4 (C2', C6'), 131.9 (C3, C5), 129.3 (C3', C5'), 127.0 (C2, C6), 122.3 (C4), 122.0 (C4').

Computing details

Data collection: CrysAlis CCD (Oxford Diffraction, 2002); cell refinement: CrysAlis RED (Oxford Diffraction, 2002); data reduction: CrysAlis RED; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 1990); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. The molecular structures of two independent molecules (A and B) of trans-4-bromoazoxybenzene. Displacement ellipsoids are shown at the 50% probability level and H atoms are drawn as small spheres of arbitrary radii.
	Fig. 2. The columns formed in the ac plane by molecules of trans-4-bromo-ONN-azoxybenzene.

(I)

Crystal data

C12H9BrN2O	Dx = 1.696 Mg m^−3
Mr = 277.12	Melting point: 346 K
Orthorhombic, Pna21	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2c -2n	Cell parameters from 11971 reflections
a = 23.987 (2) Å	θ = 3.4–25.0°
b = 3.9394 (5) Å	µ = 3.77 mm^−1
c = 22.965 (2) Å	T = 90 K
V = 2170.1 (4) Å^3	Prisms, yellow
Z = 8	0.40 × 0.25 × 0.13 mm
F(000) = 1104

Data collection

'Xcalibur' diffractometer	3773 independent reflections
Radiation source: fine-focus sealed tube	3634 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.054
Detector resolution: 1024x1024 with blocks 2x2 pixels mm^-1	θmax = 25.0°, θmin = 3.4°
ω scans	h = −28→28
Absorption correction: empirical (using intensity measurements) CrysAlis RED (Oxford Diffraction, 2002)	k = −4→3
Tmin = 0.336, Tmax = 0.613	l = −27→27
11971 measured reflections

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.027	H-atom parameters not refined
wR(F^2) = 0.062	w = 1/[σ^2(Fo^2) + (0.0385P)^2] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max = 0.001
3773 reflections	Δρmax = 0.49 e Å^−3
289 parameters	Δρmin = −0.50 e Å^−3
1 restraint	Absolute structure: Flack (1983), 1806 Friedel pairs?
Primary atom site location: structure-invariant direct methods	Absolute structure parameter: −0.004 (7)

Special details

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 (Ų)

	x	y	z	Uiso*/Ueq
Br1A	0.432307 (13)	−0.31798 (9)	0.511092 (14)	0.02141 (9)
O1A	0.63431 (10)	0.1472 (6)	0.70629 (10)	0.0257 (6)
N1A	0.59561 (11)	0.2572 (7)	0.73806 (11)	0.0154 (6)
N2A	0.54333 (12)	0.2444 (7)	0.72842 (12)	0.0167 (6)
C1A	0.52374 (14)	0.0984 (8)	0.67629 (13)	0.0140 (7)
C2A	0.55340 (15)	−0.0701 (9)	0.63229 (15)	0.0177 (7)
H2A	0.5917	−0.0990	0.6357	0.021*
C3A	0.52566 (15)	−0.1936 (8)	0.58375 (14)	0.0178 (7)
H3A	0.5455	−0.3049	0.5546	0.021*
C4A	0.46905 (14)	−0.1520 (8)	0.57857 (14)	0.0175 (7)
C5A	0.43817 (15)	0.0070 (8)	0.62199 (14)	0.0174 (7)
H5A	0.3997	0.0286	0.6186	0.021*
C6A	0.46567 (14)	0.1320 (8)	0.67014 (14)	0.0168 (7)
H6A	0.4454	0.2408	0.6992	0.020*
C1A'	0.61273 (14)	0.4176 (8)	0.79325 (14)	0.0147 (7)
C2A'	0.66806 (15)	0.3941 (9)	0.80823 (15)	0.0192 (8)
H2A'	0.6933	0.2834	0.7841	0.023*
C3A'	0.68560 (15)	0.5403 (9)	0.86065 (16)	0.0194 (8)
H3A'	0.7230	0.5313	0.8713	0.023*
C4A'	0.64734 (15)	0.6980 (9)	0.89645 (14)	0.0215 (8)
H4A'	0.6589	0.7909	0.9317	0.026*
C5A'	0.59159 (16)	0.7187 (9)	0.88007 (16)	0.0205 (8)
H5A'	0.5662	0.8280	0.9042	0.025*
C6A'	0.57362 (14)	0.5780 (8)	0.82815 (15)	0.0164 (7)
H6A'	0.5364	0.5907	0.8170	0.020*
Br1B	0.310454 (14)	0.46241 (8)	0.696045 (17)	0.02305 (10)
O1B	0.22466 (10)	0.9609 (7)	0.42276 (11)	0.0268 (6)
N1B	0.18143 (11)	1.0674 (7)	0.44703 (13)	0.0178 (6)
N2B	0.16879 (12)	1.0492 (7)	0.50155 (13)	0.0177 (6)
C1B	0.20716 (14)	0.8990 (9)	0.54103 (15)	0.0159 (7)
C2B	0.25634 (13)	0.7222 (8)	0.53015 (15)	0.0187 (7)
H2B	0.2684	0.6894	0.4921	0.022*
C3B	0.28727 (14)	0.5951 (9)	0.57635 (15)	0.0201 (7)
H3B	0.3204	0.4799	0.5693	0.024*
C4B	0.26864 (14)	0.6402 (8)	0.63319 (15)	0.0178 (7)
C5B	0.21968 (13)	0.8152 (8)	0.64473 (14)	0.0183 (7)
H5B	0.2075	0.8469	0.6828	0.022*
C6B	0.18963 (14)	0.9401 (9)	0.59879 (15)	0.0172 (7)
H6B	0.1566	1.0558	0.6062	0.021*
C1B'	0.13985 (13)	1.2355 (8)	0.41100 (15)	0.0150 (7)
C2B'	0.14830 (15)	1.2344 (9)	0.35104 (15)	0.0201 (7)
H2B'	0.1801	1.1364	0.3351	0.024*
C3B'	0.10844 (15)	1.3820 (9)	0.31577 (15)	0.0206 (8)
H3B'	0.1134	1.3798	0.2756	0.025*
C4B'	0.06143 (15)	1.5323 (9)	0.33867 (15)	0.0201 (8)
H4B'	0.0350	1.6310	0.3143	0.024*
C5B'	0.05400 (15)	1.5342 (9)	0.39902 (16)	0.0205 (8)
H5B'	0.0224	1.6355	0.4148	0.025*
C6B'	0.09299 (14)	1.3873 (9)	0.43571 (15)	0.0200 (7)
H6B'	0.0880	1.3899	0.4759	0.024*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1A	0.03015 (18)	0.02275 (17)	0.01133 (14)	−0.00503 (14)	−0.00138 (17)	0.00048 (15)
O1A	0.0165 (13)	0.0447 (15)	0.0158 (13)	0.0021 (11)	0.0066 (10)	−0.0076 (11)
N1A	0.0178 (15)	0.0167 (14)	0.0118 (14)	0.0009 (12)	0.0014 (12)	0.0023 (11)
N2A	0.0159 (15)	0.0213 (15)	0.0129 (14)	0.0010 (11)	−0.0001 (12)	0.0008 (12)
C1A	0.0176 (17)	0.0164 (16)	0.0079 (15)	0.0000 (14)	0.0005 (13)	0.0042 (12)
C2A	0.0170 (18)	0.0169 (17)	0.0191 (17)	−0.0009 (15)	0.0027 (14)	0.0019 (15)
C3A	0.0264 (19)	0.0157 (16)	0.0114 (16)	−0.0009 (14)	0.0063 (14)	0.0002 (13)
C4A	0.0253 (19)	0.0158 (16)	0.0115 (15)	−0.0034 (14)	0.0007 (14)	0.0037 (14)
C5A	0.0195 (19)	0.0184 (18)	0.0142 (17)	−0.0006 (13)	−0.0012 (14)	0.0033 (13)
C6A	0.0223 (18)	0.0182 (17)	0.0100 (15)	−0.0013 (14)	0.0037 (13)	0.0014 (13)
C1A'	0.0189 (17)	0.0144 (16)	0.0109 (15)	−0.0015 (13)	−0.0008 (13)	0.0026 (13)
C2A'	0.023 (2)	0.0185 (17)	0.0165 (17)	0.0007 (15)	0.0005 (15)	0.0028 (14)
C3A'	0.019 (2)	0.0210 (18)	0.0181 (19)	−0.0007 (14)	−0.0075 (15)	0.0039 (14)
C4A'	0.030 (2)	0.0219 (18)	0.0127 (17)	−0.0041 (15)	−0.0052 (15)	0.0034 (14)
C5A'	0.028 (2)	0.0196 (18)	0.0139 (16)	0.0015 (15)	−0.0003 (15)	0.0015 (14)
C6A'	0.0178 (17)	0.0175 (17)	0.0139 (15)	−0.0019 (13)	−0.0020 (14)	0.0050 (14)
Br1B	0.02537 (18)	0.02402 (17)	0.01976 (16)	−0.00045 (14)	−0.00634 (16)	−0.00039 (18)
O1B	0.0204 (13)	0.0409 (16)	0.0191 (12)	0.0124 (12)	0.0088 (11)	0.0033 (11)
N1B	0.0178 (15)	0.0164 (14)	0.0192 (15)	0.0003 (12)	0.0017 (12)	−0.0016 (12)
N2B	0.0175 (15)	0.0222 (15)	0.0133 (15)	−0.0041 (11)	0.0029 (12)	−0.0015 (12)
C1B	0.0124 (16)	0.0185 (17)	0.0168 (17)	−0.0035 (14)	0.0021 (15)	−0.0036 (14)
C2B	0.0200 (18)	0.0194 (17)	0.0167 (16)	−0.0035 (14)	0.0026 (14)	−0.0027 (13)
C3B	0.0164 (17)	0.0216 (18)	0.0223 (18)	−0.0005 (14)	−0.0002 (15)	0.0005 (15)
C4B	0.0176 (17)	0.0172 (17)	0.0185 (16)	−0.0052 (14)	−0.0009 (14)	0.0003 (14)
C5B	0.0200 (18)	0.0177 (17)	0.0173 (17)	−0.0028 (14)	0.0029 (14)	−0.0023 (14)
C6B	0.0134 (18)	0.0206 (18)	0.0178 (18)	−0.0027 (14)	0.0032 (14)	−0.0011 (14)
C1B'	0.0125 (16)	0.0156 (16)	0.0169 (16)	−0.0003 (13)	−0.0028 (14)	0.0001 (13)
C2B'	0.0196 (19)	0.0211 (18)	0.0197 (17)	0.0007 (15)	0.0068 (15)	−0.0019 (14)
C3B'	0.0239 (19)	0.0225 (19)	0.0154 (18)	−0.0029 (16)	0.0006 (15)	0.0026 (14)
C4B'	0.0190 (18)	0.0172 (18)	0.024 (2)	−0.0028 (14)	−0.0023 (15)	−0.0006 (14)
C5B'	0.0158 (17)	0.0191 (18)	0.0267 (19)	0.0013 (15)	0.0033 (15)	−0.0030 (16)
C6B'	0.0223 (18)	0.0202 (18)	0.0174 (18)	−0.0018 (15)	0.0039 (15)	−0.0025 (14)

Geometric parameters (Å, º)

Br1A—C4A	1.899 (3)	Br1B—C4B	1.892 (3)
O1A—N1A	1.258 (4)	O1B—N1B	1.250 (4)
N1A—N2A	1.274 (4)	N1B—N2B	1.290 (4)
N1A—C1A'	1.475 (4)	N1B—C1B'	1.455 (4)
N2A—C1A	1.409 (4)	N2B—C1B	1.421 (5)
C1A—C2A	1.403 (5)	C1B—C2B	1.393 (5)
C1A—C6A	1.406 (5)	C1B—C6B	1.401 (5)
C2A—C3A	1.386 (5)	C2B—C3B	1.388 (5)
C2A—H2A	0.9300	C2B—H2B	0.9300
C3A—C4A	1.373 (5)	C3B—C4B	1.391 (5)
C3A—H3A	0.9300	C3B—H3B	0.9300
C4A—C5A	1.391 (5)	C4B—C5B	1.387 (5)
C5A—C6A	1.379 (5)	C5B—C6B	1.369 (5)
C5A—H5A	0.9300	C5B—H5B	0.9300
C6A—H6A	0.9300	C6B—H6B	0.9300
C1A'—C2A'	1.374 (5)	C1B'—C2B'	1.392 (5)
C1A'—C6A'	1.386 (5)	C1B'—C6B'	1.394 (5)
C2A'—C3A'	1.399 (5)	C2B'—C3B'	1.382 (5)
C2A'—H2A'	0.9300	C2B'—H2B'	0.9300
C3A'—C4A'	1.380 (5)	C3B'—C4B'	1.378 (5)
C3A'—H3A'	0.9300	C3B'—H3B'	0.9300
C4A'—C5A'	1.392 (5)	C4B'—C5B'	1.397 (5)
C4A'—H4A'	0.9300	C4B'—H4B'	0.9300
C5A'—C6A'	1.384 (5)	C5B'—C6B'	1.385 (5)
C5A'—H5A'	0.9300	C5B'—H5B'	0.9300
C6A'—H6A'	0.9300	C6B'—H6B'	0.9300
O1A—N1A—N2A	127.7 (3)	O1B—N1B—N2B	127.5 (3)
O1A—N1A—C1A'	116.1 (3)	O1B—N1B—C1B'	117.9 (3)
N2A—N1A—C1A'	116.1 (3)	N2B—N1B—C1B'	114.6 (3)
N1A—N2A—C1A	119.5 (3)	N1B—N2B—C1B	119.4 (3)
C2A—C1A—C6A	118.3 (3)	C2B—C1B—C6B	118.8 (3)
C2A—C1A—N2A	129.5 (3)	C2B—C1B—N2B	130.0 (3)
C6A—C1A—N2A	112.2 (3)	C6B—C1B—N2B	111.2 (3)
C3A—C2A—C1A	120.1 (3)	C3B—C2B—C1B	119.7 (3)
C3A—C2A—H2A	119.9	C3B—C2B—H2B	120.1
C1A—C2A—H2A	119.9	C1B—C2B—H2B	120.1
C4A—C3A—C2A	120.2 (3)	C2B—C3B—C4B	120.0 (3)
C4A—C3A—H3A	119.9	C2B—C3B—H3B	120.0
C2A—C3A—H3A	119.9	C4B—C3B—H3B	120.0
C3A—C4A—C5A	121.2 (3)	C5B—C4B—C3B	121.0 (3)
C3A—C4A—Br1A	119.3 (2)	C5B—C4B—Br1B	119.1 (3)
C5A—C4A—Br1A	119.5 (3)	C3B—C4B—Br1B	119.9 (3)
C6A—C5A—C4A	118.8 (3)	C6B—C5B—C4B	118.5 (3)
C6A—C5A—H5A	120.6	C6B—C5B—H5B	120.8
C4A—C5A—H5A	120.6	C4B—C5B—H5B	120.8
C5A—C6A—C1A	121.4 (3)	C5B—C6B—C1B	122.0 (3)
C5A—C6A—H6A	119.3	C5B—C6B—H6B	119.0
C1A—C6A—H6A	119.3	C1B—C6B—H6B	119.0
C2A'—C1A'—C6A'	122.7 (3)	C2B'—C1B'—C6B'	121.4 (3)
C2A'—C1A'—N1A	117.1 (3)	C2B'—C1B'—N1B	117.5 (3)
C6A'—C1A'—N1A	120.3 (3)	C6B'—C1B'—N1B	121.1 (3)
C1A'—C2A'—C3A'	118.6 (3)	C3B'—C2B'—C1B'	118.6 (3)
C1A'—C2A'—H2A'	120.7	C3B'—C2B'—H2B'	120.7
C3A'—C2A'—H2A'	120.7	C1B'—C2B'—H2B'	120.7
C4A'—C3A'—C2A'	119.9 (3)	C4B'—C3B'—C2B'	121.6 (3)
C4A'—C3A'—H3A'	120.1	C4B'—C3B'—H3B'	119.2
C2A'—C3A'—H3A'	120.1	C2B'—C3B'—H3B'	119.2
C3A'—C4A'—C5A'	120.3 (3)	C3B'—C4B'—C5B'	119.0 (3)
C3A'—C4A'—H4A'	119.9	C3B'—C4B'—H4B'	120.5
C5A'—C4A'—H4A'	119.9	C5B'—C4B'—H4B'	120.5
C6A'—C5A'—C4A'	120.6 (3)	C6B'—C5B'—C4B'	121.0 (3)
C6A'—C5A'—H5A'	119.7	C6B'—C5B'—H5B'	119.5
C4A'—C5A'—H5A'	119.7	C4B'—C5B'—H5B'	119.5
C5A'—C6A'—C1A'	118.0 (3)	C5B'—C6B'—C1B'	118.4 (3)
C5A'—C6A'—H6A'	121.0	C5B'—C6B'—H6B'	120.8
C1A'—C6A'—H6A'	121.0	C1B'—C6B'—H6B'	120.8
O1A—N1A—N2A—C1A	−1.2 (5)	O1B—N1B—N2B—C1B	1.3 (5)
C1A'—N1A—N2A—C1A	179.3 (3)	C1B'—N1B—N2B—C1B	−178.2 (3)
N1A—N2A—C1A—C2A	5.9 (5)	N1B—N2B—C1B—C2B	−8.7 (5)
N1A—N2A—C1A—C6A	−174.6 (3)	N1B—N2B—C1B—C6B	172.5 (3)
C6A—C1A—C2A—C3A	1.1 (5)	C6B—C1B—C2B—C3B	−0.9 (5)
N2A—C1A—C2A—C3A	−179.5 (3)	N2B—C1B—C2B—C3B	−179.6 (3)
C1A—C2A—C3A—C4A	−0.1 (5)	C1B—C2B—C3B—C4B	1.0 (5)
C2A—C3A—C4A—C5A	−1.4 (5)	C2B—C3B—C4B—C5B	−0.9 (5)
C2A—C3A—C4A—Br1A	179.1 (2)	C2B—C3B—C4B—Br1B	179.3 (3)
C3A—C4A—C5A—C6A	1.8 (5)	C3B—C4B—C5B—C6B	0.7 (5)
Br1A—C4A—C5A—C6A	−178.7 (2)	Br1B—C4B—C5B—C6B	−179.5 (2)
C4A—C5A—C6A—C1A	−0.7 (5)	C4B—C5B—C6B—C1B	−0.6 (5)
C2A—C1A—C6A—C5A	−0.7 (5)	C2B—C1B—C6B—C5B	0.7 (5)
N2A—C1A—C6A—C5A	179.8 (3)	N2B—C1B—C6B—C5B	179.7 (3)
O1A—N1A—C1A'—C2A'	−8.0 (4)	O1B—N1B—C1B'—C2B'	6.7 (4)
N2A—N1A—C1A'—C2A'	171.5 (3)	N2B—N1B—C1B'—C2B'	−173.8 (3)
O1A—N1A—C1A'—C6A'	173.2 (3)	O1B—N1B—C1B'—C6B'	−174.2 (3)
N2A—N1A—C1A'—C6A'	−7.3 (4)	N2B—N1B—C1B'—C6B'	5.2 (4)
C6A'—C1A'—C2A'—C3A'	−0.5 (5)	C6B'—C1B'—C2B'—C3B'	−1.3 (5)
N1A—C1A'—C2A'—C3A'	−179.3 (3)	N1B—C1B'—C2B'—C3B'	177.8 (3)
C1A'—C2A'—C3A'—C4A'	1.2 (5)	C1B'—C2B'—C3B'—C4B'	0.9 (5)
C2A'—C3A'—C4A'—C5A'	−1.4 (5)	C2B'—C3B'—C4B'—C5B'	−0.2 (5)
C3A'—C4A'—C5A'—C6A'	0.8 (5)	C3B'—C4B'—C5B'—C6B'	−0.1 (5)
C4A'—C5A'—C6A'—C1A'	−0.1 (5)	C4B'—C5B'—C6B'—C1B'	−0.3 (5)
C2A'—C1A'—C6A'—C5A'	−0.1 (5)	C2B'—C1B'—C6B'—C5B'	1.0 (5)
N1A—C1A'—C6A'—C5A'	178.7 (3)	N1B—C1B'—C6B'—C5B'	−178.0 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C2A—H2A···O1A	0.93	2.15	2.718 (4)	119
C2A′—H2A′···O1A	0.93	2.34	2.661 (4)	100
C2B—H2B···O1B	0.93	2.19	2.747 (4)	118
C2B′—H2B′···O1B	0.93	2.38	2.688 (5)	99