Anomalous halogen bonds in the crystal structures of 1,2,3-tri­bromo-5-nitro­benzene and 1,3-di­bromo-2-iodo-5-nitro­benzene

Romero, J.A.; Aguirre Hernández, G.; Bernès, S.

doi:10.1107/S2056989015013377

research communications

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ISSN: 2056-9890

Volume 71| Part 8| August 2015| Pages 960-964

https://doi.org/10.1107/S2056989015013377

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Anomalous halogen bonds in the crystal structures of 1,2,3-tribromo-5-nitrobenzene and 1,3-dibromo-2-iodo-5-nitrobenzene

José A. Romero,^a Gerardo Aguirre Hernández ^a and Sylvain Bernès ^b ^*

^aCentro de Graduados e Investigación en Química, Instituto Tecnológico de Tijuana, Apdo. Postal 1166, 22510 Tijuana, B.C., Mexico, and ^bInstituto de Física, Benemérita Universidad Autónoma de Puebla, Av. San Claudio y 18 Sur, 72570 Puebla, Pue., Mexico
^*Correspondence e-mail: sylvain_bernes@hotmail.com

Edited by W. T. A. Harrison, University of Aberdeen, Scotland (Received 1 July 2015; accepted 12 July 2015; online 22 July 2015)

The title trihalogenated nitrobenzene derivatives, C₆H₂Br₃NO₂ and C₆H₂Br₂INO₂, crystallize in triclinic and monoclinic cells, respectively, with two molecules per asymmetric unit in each case. The asymmetric unit of the tribromo compound features a polarized Br^δ+⋯Br^δ- intermolecular halogen bond. After substitution of the Br atom in the para position with respect to the nitro group, the network of X⋯X halogen contacts is reorganized. Two intermolecular polarized halogen bonds are then observed, which present the uncommon polarization Br^δ+⋯I^δ-: the more electronegative site (Br) behaves as a donor and the less electronegative site (I) as an acceptor for the charge transfer.

Keywords: crystal structure; polyhalogenated benzene; halogen bond; bromine; iodine.

CCDC references: 1412444; 1412445

1. Chemical context

Within the large class of non-covalent interactions studied in chemical crystallography, halogen bonds are of special interest in crystal engineering. The stabilizing interaction between a halogen atom and a Lewis base, X⋯B, shares many aspects with classical hydrogen bonds, but is more directional. On the other hand, halogen contacts X⋯X are more difficult to conceptualize (Wang et al., 2014 ), for instance because the charge transfer in the Br⋯Br contact is not as obvious as in hydrogen bonds. Evidence supporting the importance of this topic is the recent organization of an international meeting dedicated to halogen bonding (Erdelyi, 2014 ).

In this context, we are engaged in the synthesis and structural characterization of a series of halogen-substituted nitrobenzenes. The present communication describes two closely related compounds in the series, which differ only by the halogen atom substituting at the ring position para to the nitro group. Despite the small chemical modification, the resulting crystal structures are very different, as a consequence of a different network of halogen bonds.

2. Structural commentary

Both compounds crystallize with two molecules in the asymmetric unit, but in different space groups. The tribromo derivative, (I, Fig. 1), is a P $[\overline{1}]$ crystal isomorphous to the chloro analogue (Bhar et al., 1995 ), although the unit-cell parameters are significantly larger for (I) compared to the chloro compound: the cell volume is increased by more than 7%. In the present work, we retained the Niggli reduced triclinic cell (a < b < c), while Bhar et al. used a non-reduced cell. Moreover, the asymmetric unit content was defined in order to emphasize the strongest Br⋯Br bond in (I). The bromo-iodo derivative (II, Fig. 2) crystallizes in the monoclinic system and, in that case, the standard setting was used for space group P2₁/c.

Figure 1
The asymmetric unit of (I)

, with displacement ellipsoids at the 30% probability level. The dashed bond connecting the independent molecules is a type-II halogen bond.

Figure 2
The asymmetric unit of (II)

, with displacement ellipsoids at the 30% probability level. The dashed bonds connecting the independent molecules are halogen contacts.

The C—halogen bond lengths are as expected. In (I), C—Br distances are in the range 1.821 (12)–1.886 (11) Å, slightly shorter than C—Br bond lengths observed in hexabromobenzene, 1.881 Å (T = 100 K; Reddy et al., 2006 ) or 1.871 Å (synchrotron study, T = 100 K; Brezgunova et al., 2012 ). In (II), C—Br bond lengths are longer, 1.875 (13) to 1.895 (14) Å, while the C—I bond lengths, 2.088 (12) and 2.074 (14) Å, may be compared to bonds in hexaiodobenzene, 2.109 Å (T = 100 K; Ghosh et al., 2007 ) or 1,2,3-triiodobenzene, 2.090 Å (T = 223 K, Novak & Li, 2007 ). Indeed, differences in bond lengths between perhalogenated and trihalogenated derivatives are within experimental errors, and the substitution of the 5-position by the nitro electron-withdrawing group in (I) and (II) has probably little influence on these bonds.

The important feature in these halogenated molecules is rather the possibility of steric repulsion between vicinal halogen atoms, which is related to the reduction of endocyclic angles. Regarding this point, it is worth reading the Acta E article about 1,2,3-triiodobenzene (Novak & Li, 2007). As in polyiodo derivatives, intramolecular steric crowding between the halogen atoms in (I) and (II) is offset by benzene ring distortion. As a consequence, the C1—C2—C3 and equivalent C11—C12—C13 angles are systematically less than 120°: 116.2 (11) and 118.8 (13)° in (I); 118.1 (12) and 117.3 (13)° in (II). Again, the nitro group has little influence on intramolecular halogen⋯halogen contacts. For instance, in 1,3-dibromo-2-iodobenzene, the C1—C2—C3 angle is 118.0° (Schmidbaur et al., 2004 ), very close to that observed in (II), which presents the same halogen substitution.

The 5-nitro substituent is almost conjugated with the benzene nucleus in (I): the dihedral angle between the NO₂ plane and the benzene ring is 6(2) and 1(2)° for each independent molecule. For (II), twisting of the NO₂ groups is more significant, with dihedral angles of 10 (1) and 7(1)°. This near planar conformation is identical to that observed for 1,2,3-trichloro-5-nitrobenzene (Bhar et al., 1995), but contrasts with the twisted conformation observed in perhalogenated nitrobenzene derivatives: pentachloronitrobenzene (twist angle of NO₂: 62°; Tanaka et al., 1974 ) and 1-bromo-2,3,5,6-tetrafluoro-4-nitrobenzene (twist angle of NO₂: 41.7 (3)°; Stein et al., 2011 ). It thus seems clear that twisting of the nitro group with respect to the benzene ring in nitrobenzene derivatives is a direct consequence of intramolecular crowding with ortho substituents. For 1,2,3-halogenated-5-nitrobenzenes such as (I) and (II), a planar conformation should be expected as a rule.

3. Supramolecular features

The crystal structures are directed by intermolecular weak halogen bonds, also known as type-II interactions in the Desiraju classification scheme (Reddy et al., 2006). Such a bond is present in the asymmetric unit of (I), between Br2 and Br11 (Fig. 3). The type-II arrangement is characterized by angles θ₁ = C2—Br2⋯Br11 and θ₂ = C11—Br11⋯Br2, which should be close to 180 and 90°, respectively. For (I), observed angles are θ₁ = 165.2 (5)° and θ₂ = 82.3 (5)°. The crystal packing thus polarizes the involved halogen atoms, forming the halogen bond Br2^δ+⋯Br11^δ-. This dimolecular polar unit is connected via inversion centers to neighboring units in the cell, forming C—H⋯Br hydrogen bonds, and O⋯Br contacts. This packing motif induces secondary halogen⋯halogen contacts, which are clearly unpolarized. These type-I interactions are characterized by angles θ₁ ≃ θ₂ (Table 1, entries 2 and 3) and display larger Br⋯Br separations compared to the polarized halogen bond (entry 1), in which electrostatic forces bring the atoms into close contact.

Table 1
Halogen-bond geometry (Å, °) for (I)

X₁⋯X₂	d	θ₁	θ₂	bond type
Br2⋯Br11	3.642 (3)	165.2 (5)	82.3 (5)	II-polarized
Br1⋯Br1ⁱ	3.731 (4)	133.3 (4)	133.3 (4)	I-unpolarized
Br2⋯Br13ⁱⁱ	3.781 (3)	126.8 (4)	129.6 (4)	I-unpolarized
Notes: d = separation X₁⋯X₂; θ₁ = angle C—X₁⋯X₂; θ₂ = angle X₁⋯X₂—C. For halogen bond types, see: Reddy et al. (2006). Symmetry codes: (i) −x, 1 − y, −z; (ii) −x, −y, 1 − z.

Figure 3
Part of the crystal structure of (I)

, emphasizing the halogen bonds (dashed lines). The green molecules correspond to the asymmetric unit.

The substitution of one Br atom by I, to form crystal (II), changes dramatically the packing structure, affording a more complex network of halogen contacts (Fig. 4 and Table 2). Within the asymmetric unit, the type-II polarized contact is Br1⋯I12 (Table 2, entry 1). However, θ angles for this bond deviate from ideal values, and, surprisingly, the bond is polarized in the wrong way, Br^δ+⋯I^δ-. The opposite polarization was expected for this bond, due to the lower electronegativity and higher polarizability of iodine compared to bromine. The other significant contact observed in the asymmetric unit is a Br⋯Br unpolarized contact. The network of halogen bonds is expanded in the [100] direction by Br11, which gives a bifurcated contact with I2 and Br3 (Table 2, entries 2 and 4). One contact is polarized, with the polarization, once again, oriented in the unexpected way, I2^δ-⋯Br11^δ+. These anomalous halogen bonds are not present in other mixed halogen derivatives. Indeed, in 1,3-dibromo-2-iodobenzene (Schmidbaur et al., 2004), the iodine atom is not engaged in halogen bonding.

Table 2
Halogen-bond geometry (Å, °) for (II)

X₁⋯X₂	d	θ₁	θ₂	bond type
Br1⋯I12	3.813 (2)	161.2 (4)	117.2 (4)	II-polarized
I2⋯Br11ⁱ	3.893 (2)	116.6 (4)	161.8 (4)	II-polarized
Br1⋯Br13	3.787 (2)	142.8 (4)	122.9 (4)	I-unpolarized
Br11⋯Br3ⁱⁱ	3.858 (2)	143.9 (4)	124.4 (4)	I-unpolarized
Notes: d = separation X₁⋯X₂; θ₁ = angle C—X₁⋯X₂; θ₂ = angle X₁⋯X₂—C. For halogen bond types, see: Reddy et al. (2006). Symmetry codes: (i) 1 + x, y, z; (ii) −1 + x, y, z.

Figure 4
Part of the crystal structure of (II)

, emphasizing the halogen bonds (dashed lines). The green molecules correspond to the asymmetric unit.

4. Database survey

The current release of the CSD (Version 5.36 with all updates; Groom & Allen, 2014 ), contains many structures of halogen-substituted nitrobenzene, with Cl (e.g. Bhar et al., 1995; Tanaka et al., 1974), Br (e.g. Olaru et al., 2014 ), and I (Thalladi et al., 1996 ). This series is completed with nitrophenol derivatives, for example 2,3-difluoro-4-iodo-6-nitrophenol (Francke et al., 2010 ). Structures of pentachlorophenol (Brezgunova et al., 2012) and pentabromophenol (Betz et al., 2008 ; Brezgunova et al., 2012) are also available.

Regarding poly- and per-halogenated benzene structures, an impressive series of 23 compounds has been described, including Cl, Br, I and Me as substituents, generating a variety of molecular symmetries (Reddy et al., 2006). The structure of D_6h-perhalogenated benzene has been reported with F (Shorafa et al., 2009 ), Cl (Brown & Strydom, 1974 ; Reddy et al., 2006), Br (Baharie & Pawley, 1979 ; Reddy et al., 2006; Brezgunova et al., 2012) and I (Ghosh et al., 2007). The former is a Z′ = 2 crystal, while others are Z′=1 crystals.

5. Synthesis and crystallization

Compounds (I) and (II) were synthesized from 2,6-dibromo-4-nitroaniline (Bryant et al., 1998 ), as depicted in Fig. 5.

Figure 5
Synthetic scheme for (I)

and (II)

Synthesis of (I). A solution of 2,6-dibromo-4-nitroaniline (1.0 g, 3.38 mmol) in acetic acid (3 ml) was cooled to 278 K, and concentrated H₂SO₄ (7 ml) was carefully added under stirring. While ensuring that the temperature was still below 278 K, NaNO₂ (0.708 g, 10.26 mmol) was added in one batch. The reaction was stirred at this temperature for 2 h to afford the diazonium salt. An aqueous solution (17.67 ml) of CuBr (4.95 g, 34.54 mmol) and 47% HBr (17.67 ml) was warmed to 343 K, and the diazotization solution previously prepared was added in one batch with stirring. The mixture was kept at 343 K for 1 h, and then left to cool overnight. The reaction was neutralized with NaOH and extracted with CH₂Cl₂ (3 × 30 ml). The resulting solution was concentrated under vacuum and the crude material was purified by flash chromatography (petroleum ether/CH₂Cl₂ 8/2, R_f = 0.49) to give (I). Crystals were obtained by slow evaporation of a methanol/ethyl ether solution (yield: 0.952 g, 2.65 mmol, 78%). m.p. 380–382 K. IR (KBr, cm⁻¹): 3090 (Ar—H); 1583 (C=C); 1526, 1342 (N=O); 738 (C—Br). ¹H-NMR (600 MHz, CDCl₃): δ 8.43 (s, H-4, H-6). ¹³C-NMR (150 MHz, CDCl₃): δ 146.8, 135.7, 127.0, 126.9, 126.8. EIMS m/z: [M⁺] 357 (34), [M⁺+2] 359 (7), [M⁺+4] 361 (100), [M⁺+6] 363 (36) [M⁺-NO₂] 311 (12).

Synthesis of (II). A solution of 2,6-dibromo-4-nitroaniline (1.0 g, 3.38 mmol) in acetic acid (3 ml) was cooled to 278 K in an ice-salt bath, and concentrated H₂SO₄ (3 ml) was carefully added under stirring. While ensuring that the temperature was still below 278 K, NaNO₂ (0.242 g, 3.516 mmol) was added in one batch. The reaction was stirred at this temperature for 30 min to afford the diazonium salt. An aqueous solution (10 ml) of KI (5.635 g, 33.95 mmol) was prepared, and the diazotization solution previously prepared was added in one batch. The mixture was then further stirred for 1 h. The reaction was neutralized with NaOH, extracted with CH₂Cl₂ (3 × 30 ml), and concentrated under vacuum. The crude material was purified by flash chromatography (petroleum ether/CH₂Cl₂ 4/1, R_f = 0.31) to give (II). Crystals were obtained by slow evaporation of an acetone/methanol/CH₂Cl₂ solution (yield: 1.21 g, 2.98 mmol, 88%). m.p. 415–417 K. IR (KBr, cm⁻¹): 3010 (Ar—H); 1620, 1516 (C=C); 1336 (N=O). ¹H-NMR (600 MHz, CDCl₃): δ 8.38 (s, H-4, H-6). ¹³C-NMR (150 MHz, CDCl₃): δ 146.1, 142.4, 127.4, 124.1. EIMS m/z: [M⁺] 405 (42), [M⁺+2] 407 (100), [M⁺+4] 409 (48).

6. Refinement

Crystal data, data collection and structure refinement details for (I) and (II) are summarized in Table 3. The absorption correction for (I) was challenging, and eventually carried out by applying DIFABS on the complete isotropic model (Walker & Stuart, 1983 ). In the case of (II), measured ψ-scans were used. H atoms were refined as riding to their carrier C atoms, with C—H bond lengths fixed at 0.93 Å and with U_iso(H) = 1.2U_eq(carrier atom).

Table 3
Experimental details

	(I)	(II)
Crystal data
Chemical formula	C₆H₂Br₃NO₂	C₆H₂Br₂INO₂
M_r	359.82	406.81
Crystal system, space group	Triclinic, P $[\overline{1}]$	Monoclinic, P2₁/c
Temperature (K)	298	298
a, b, c (Å)	7.641 (5), 8.040 (5), 14.917 (6)	13.548 (3), 20.037 (3), 9.123 (2)
α, β, γ (°)	83.91 (3), 79.86 (4), 81.49 (4)	90, 130.37 (2), 90
V (Å³)	889.2 (8)	1886.8 (8)
Z	4	8
Radiation type	Mo Kα	Mo Kα
μ (mm⁻¹)	13.57	11.82
Crystal size (mm)	0.42 × 0.40 × 0.30	0.50 × 0.22 × 0.12

Data collection
Diffractometer	Bruker P4	Bruker P4
Absorption correction	Part of the refinement model (ΔF) (Walker & Stuart, 1983)	ψ scan (XSCANS; Bruker, 1997 )
T_min, T_max	0.0002, 0.001	0.429, 0.988
No. of measured, independent and observed [I > 2σ(I)] reflections	6070, 3141, 1503	5716, 5407, 1968
R_int	0.120	0.058
(sin θ/λ)_max (Å⁻¹)	0.596	0.703

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.066, 0.196, 1.47	0.061, 0.153, 0.95
No. of reflections	3141	5407
No. of parameters	218	218
H-atom treatment	H-atom parameters constrained	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.79, −1.00	0.84, −0.84
Computer programs: XSCANS (Bruker, 1997), SHELXS2014 (Sheldrick, 2008 ), SHELXL2014 (Sheldrick, 2015 ) and Mercury (Macrae et al., 2008 ).

Supporting information

CCDC references: 1412444; 1412445

Crystal structure: contains datablocks I, II, global. DOI: https://doi.org/10.1107/S2056989015013377/hb7459sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989015013377/hb7459Isup2.hkl

Structure factors: contains datablock II. DOI: https://doi.org/10.1107/S2056989015013377/hb7459IIsup3.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2056989015013377/hb7459Isup4.cml

Supporting information file. DOI: https://doi.org/10.1107/S2056989015013377/hb7459IIsup5.cml

checkCIF report

Computing details top

For both compounds, data collection: XSCANS (Bruker, 1997); cell refinement: XSCANS (Bruker, 1997); data reduction: XSCANS (Bruker, 1997); program(s) used to solve structure: SHELXS2014 (Sheldrick, 2008); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: SHELXL2014 (Sheldrick, 2015).

(I) 1,2,3-Tribromo-5-nitrobenzene top

Crystal data top

C₆H₂Br₃NO₂	F(000) = 664
M_r = 359.82	D_x = 2.688 Mg m⁻³
Triclinic, P1	Melting point: 380 K
a = 7.641 (5) Å	Mo Kα radiation, λ = 0.71073 Å
b = 8.040 (5) Å	Cell parameters from 48 reflections
c = 14.917 (6) Å	θ = 4.8–12.4°
α = 83.91 (3)°	µ = 13.57 mm⁻¹
β = 79.86 (4)°	T = 298 K
γ = 81.49 (4)°	Irregular, colourless
V = 889.2 (8) Å³	0.42 × 0.40 × 0.30 mm
Z = 4

Data collection top

Bruker P4 diffractometer	1503 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.120
Graphite monochromator	θ_max = 25.1°, θ_min = 2.6°
ω scans	h = −8→9
Absorption correction: part of the refinement model (ΔF) (Walker & Stuart, 1983)	k = −9→9
T_min = 0.0002, T_max = 0.001	l = 0→17
6070 measured reflections	3 standard reflections every 97 reflections
3141 independent reflections	intensity decay: 1%

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)] = 0.066	H-atom parameters constrained
wR(F²) = 0.196	w = 1/[σ²(F_o²) + (0.050P)²] where P = (F_o² + 2F_c²)/3
S = 1.47	(Δ/σ)_max < 0.001
3141 reflections	Δρ_max = 0.79 e Å⁻³
218 parameters	Δρ_min = −1.00 e Å⁻³
0 restraints	Extinction correction: SHELXL2014 (Sheldrick, 2015), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 constraints	Extinction coefficient: 0.0063 (12)
Primary atom site location: structure-invariant direct methods

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

	x	y	z	U_iso*/U_eq
Br1	0.1438 (2)	0.3194 (2)	0.05082 (13)	0.0863 (6)
Br2	0.2958 (2)	0.0254 (2)	0.20089 (11)	0.0855 (6)
Br3	0.4312 (2)	−0.3604 (2)	0.13778 (10)	0.0791 (5)
C1	0.2177 (18)	0.1018 (19)	0.0215 (9)	0.070 (4)
C2	0.2831 (17)	−0.0235 (17)	0.0860 (9)	0.063 (3)
C3	0.3360 (14)	−0.1910 (16)	0.0555 (8)	0.056 (3)
C4	0.3227 (18)	−0.2259 (19)	−0.0296 (9)	0.069 (4)
H4	0.3573	−0.3355	−0.0465	0.083*
C5	0.2615 (17)	−0.1072 (16)	−0.0895 (10)	0.064 (3)
C6	0.2067 (16)	0.0562 (16)	−0.0661 (9)	0.059 (3)
H6	0.1619	0.1373	−0.1085	0.071*
N1	0.2502 (16)	−0.1453 (18)	−0.1809 (8)	0.075 (3)
O1	0.2967 (16)	−0.2925 (16)	−0.2012 (7)	0.094 (3)
O2	0.1923 (18)	−0.0342 (15)	−0.2318 (8)	0.105 (4)
Br11	0.3943 (2)	0.2012 (2)	0.39885 (13)	0.0891 (6)
Br12	0.1013 (2)	0.1170 (2)	0.58586 (10)	0.0795 (6)
Br13	−0.3231 (2)	0.2845 (2)	0.59130 (11)	0.0865 (6)
C11	0.151 (2)	0.2912 (18)	0.4092 (12)	0.077 (4)
C12	0.0303 (18)	0.2505 (18)	0.4860 (10)	0.064 (3)
C13	−0.150 (2)	0.323 (2)	0.4913 (9)	0.073 (4)
C14	−0.2002 (19)	0.4188 (19)	0.4208 (9)	0.070 (4)
H14	−0.3207	0.4619	0.4232	0.084*
C15	−0.079 (2)	0.4583 (18)	0.3427 (8)	0.068 (4)
C16	0.0943 (19)	0.3923 (18)	0.3375 (9)	0.068 (4)
H16	0.1756	0.4155	0.2850	0.082*
N11	−0.1327 (18)	0.5801 (16)	0.2644 (10)	0.076 (3)
O11	−0.2882 (14)	0.6432 (13)	0.2757 (7)	0.083 (3)
O12	−0.0224 (17)	0.5952 (18)	0.1956 (8)	0.110 (4)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.0776 (11)	0.0671 (10)	0.1094 (12)	−0.0047 (8)	−0.0022 (9)	−0.0140 (8)
Br2	0.0876 (11)	0.0974 (13)	0.0716 (9)	−0.0124 (9)	−0.0075 (8)	−0.0164 (8)
Br3	0.0765 (10)	0.0789 (11)	0.0793 (10)	−0.0043 (8)	−0.0186 (8)	0.0070 (8)
C1	0.062 (8)	0.078 (10)	0.072 (9)	−0.013 (7)	−0.022 (7)	0.001 (7)
C2	0.058 (8)	0.068 (9)	0.062 (8)	−0.006 (7)	0.004 (6)	−0.026 (7)
C3	0.034 (6)	0.064 (8)	0.060 (7)	−0.001 (6)	0.001 (6)	0.012 (6)
C4	0.063 (8)	0.072 (9)	0.071 (9)	0.022 (7)	−0.018 (7)	−0.030 (7)
C5	0.056 (8)	0.051 (8)	0.087 (10)	−0.015 (6)	−0.021 (7)	0.009 (7)
C6	0.062 (8)	0.052 (8)	0.073 (8)	−0.019 (6)	−0.033 (7)	0.003 (6)
N1	0.079 (8)	0.081 (9)	0.080 (8)	−0.016 (7)	−0.036 (7)	−0.026 (7)
O1	0.119 (9)	0.095 (9)	0.071 (6)	−0.005 (7)	−0.017 (6)	−0.032 (6)
O2	0.151 (11)	0.087 (9)	0.089 (7)	−0.010 (8)	−0.061 (8)	0.004 (6)
Br11	0.0644 (10)	0.0993 (13)	0.1026 (12)	0.0018 (9)	−0.0185 (9)	−0.0137 (10)
Br12	0.0955 (12)	0.0701 (10)	0.0769 (9)	−0.0090 (8)	−0.0294 (9)	−0.0017 (7)
Br13	0.0785 (11)	0.0945 (13)	0.0808 (10)	−0.0202 (9)	0.0012 (8)	0.0067 (9)
C11	0.084 (10)	0.050 (8)	0.102 (11)	−0.013 (7)	−0.021 (9)	−0.015 (8)
C12	0.060 (8)	0.062 (8)	0.073 (9)	−0.018 (7)	−0.012 (8)	−0.008 (7)
C13	0.081 (10)	0.082 (10)	0.060 (8)	−0.020 (8)	−0.024 (7)	0.009 (7)
C14	0.056 (8)	0.080 (10)	0.065 (8)	−0.010 (7)	0.011 (7)	−0.007 (7)
C15	0.088 (10)	0.077 (10)	0.040 (6)	0.019 (8)	−0.034 (7)	−0.004 (6)
C16	0.070 (9)	0.072 (9)	0.062 (8)	−0.028 (8)	0.006 (7)	−0.003 (7)
N11	0.067 (8)	0.065 (8)	0.093 (10)	−0.005 (6)	−0.017 (7)	0.011 (7)
O11	0.074 (7)	0.079 (7)	0.099 (7)	0.003 (6)	−0.032 (6)	−0.014 (6)
O12	0.097 (8)	0.144 (12)	0.077 (7)	−0.012 (8)	−0.011 (7)	0.028 (7)

Geometric parameters (Å, º) top

Br1—C1	1.831 (15)	Br11—C11	1.877 (15)
Br2—C2	1.821 (12)	Br12—C12	1.854 (14)
Br3—C3	1.886 (11)	Br13—C13	1.842 (15)
C1—C6	1.415 (18)	C11—C16	1.368 (19)
C1—C2	1.416 (18)	C11—C12	1.38 (2)
C2—C3	1.445 (18)	C12—C13	1.410 (19)
C3—C4	1.353 (17)	C13—C14	1.313 (18)
C4—C5	1.328 (17)	C14—C15	1.39 (2)
C4—H4	0.9300	C14—H14	0.9300
C5—C6	1.381 (19)	C15—C16	1.347 (19)
C5—N1	1.448 (18)	C15—N11	1.515 (16)
C6—H6	0.9300	C16—H16	0.9300
N1—O2	1.194 (15)	N11—O11	1.211 (15)
N1—O1	1.238 (16)	N11—O12	1.216 (16)

C6—C1—C2	119.0 (13)	C16—C11—C12	120.4 (14)
C6—C1—Br1	119.9 (9)	C16—C11—Br11	118.6 (13)
C2—C1—Br1	121.0 (10)	C12—C11—Br11	120.9 (11)
C1—C2—C3	116.2 (11)	C11—C12—C13	118.8 (13)
C1—C2—Br2	121.3 (10)	C11—C12—Br12	122.1 (10)
C3—C2—Br2	122.5 (9)	C13—C12—Br12	118.9 (10)
C4—C3—C2	121.8 (11)	C14—C13—C12	118.8 (14)
C4—C3—Br3	120.6 (10)	C14—C13—Br13	118.0 (11)
C2—C3—Br3	117.6 (9)	C12—C13—Br13	123.1 (10)
C5—C4—C3	121.5 (13)	C13—C14—C15	122.5 (13)
C5—C4—H4	119.3	C13—C14—H14	118.8
C3—C4—H4	119.3	C15—C14—H14	118.8
C4—C5—C6	120.7 (13)	C16—C15—C14	119.2 (11)
C4—C5—N1	121.1 (13)	C16—C15—N11	117.9 (13)
C6—C5—N1	118.2 (11)	C14—C15—N11	122.8 (12)
C5—C6—C1	120.8 (11)	C15—C16—C11	120.0 (14)
C5—C6—H6	119.6	C15—C16—H16	120.0
C1—C6—H6	119.6	C11—C16—H16	120.0
O2—N1—O1	123.6 (12)	O11—N11—O12	127.0 (13)
O2—N1—C5	118.3 (13)	O11—N11—C15	114.7 (13)
O1—N1—C5	118.1 (12)	O12—N11—C15	118.1 (12)

C6—C1—C2—C3	0.6 (19)	C16—C11—C12—C13	−4 (2)
Br1—C1—C2—C3	179.5 (9)	Br11—C11—C12—C13	179.1 (11)
C6—C1—C2—Br2	−178.5 (10)	C16—C11—C12—Br12	−178.9 (11)
Br1—C1—C2—Br2	0.3 (16)	Br11—C11—C12—Br12	4.0 (17)
C1—C2—C3—C4	−0.3 (19)	C11—C12—C13—C14	4 (2)
Br2—C2—C3—C4	178.8 (11)	Br12—C12—C13—C14	179.4 (12)
C1—C2—C3—Br3	178.0 (9)	C11—C12—C13—Br13	−178.0 (11)
Br2—C2—C3—Br3	−2.8 (14)	Br12—C12—C13—Br13	−2.7 (18)
C2—C3—C4—C5	1 (2)	C12—C13—C14—C15	−3 (2)
Br3—C3—C4—C5	−177.8 (11)	Br13—C13—C14—C15	178.7 (12)
C3—C4—C5—C6	−1 (2)	C13—C14—C15—C16	2 (2)
C3—C4—C5—N1	179.1 (13)	C13—C14—C15—N11	−174.8 (15)
C4—C5—C6—C1	1 (2)	C14—C15—C16—C11	−2 (2)
N1—C5—C6—C1	−178.8 (12)	N11—C15—C16—C11	175.4 (13)
C2—C1—C6—C5	−1 (2)	C12—C11—C16—C15	3 (2)
Br1—C1—C6—C5	−180.0 (10)	Br11—C11—C16—C15	179.8 (11)
C4—C5—N1—O2	179.2 (14)	C16—C15—N11—O11	−175.5 (13)
C6—C5—N1—O2	−1 (2)	C14—C15—N11—O11	1 (2)
C4—C5—N1—O1	1 (2)	C16—C15—N11—O12	10 (2)
C6—C5—N1—O1	−178.8 (13)	C14—C15—N11—O12	−173.5 (15)

(II) 1,3-Dibromo-2-iodo-5-nitrobenzene top

Crystal data top

C₆H₂Br₂INO₂	D_x = 2.864 Mg m⁻³
M_r = 406.81	Melting point: 415 K
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
a = 13.548 (3) Å	Cell parameters from 43 reflections
b = 20.037 (3) Å	θ = 5.7–12.5°
c = 9.123 (2) Å	µ = 11.82 mm⁻¹
β = 130.37 (2)°	T = 298 K
V = 1886.8 (8) Å³	Prism, brown
Z = 8	0.50 × 0.22 × 0.12 mm
F(000) = 1472

Data collection top

Bruker P4 diffractometer	1968 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.058
Graphite monochromator	θ_max = 30.0°, θ_min = 2.2°
2θ/ω scans	h = −14→19
Absorption correction: ψ scan (XSCANS; Bruker, 1997)	k = 0→28
T_min = 0.429, T_max = 0.988	l = −12→0
5716 measured reflections	3 standard reflections every 97 reflections
5407 independent reflections	intensity decay: 1%

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)] = 0.061	H-atom parameters constrained
wR(F²) = 0.153	w = 1/[σ²(F_o²) + (0.053P)²] where P = (F_o² + 2F_c²)/3
S = 0.95	(Δ/σ)_max < 0.001
5407 reflections	Δρ_max = 0.84 e Å⁻³
218 parameters	Δρ_min = −0.84 e Å⁻³
0 restraints	Extinction correction: SHELXL2014 (Sheldrick, 2015), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 constraints	Extinction coefficient: 0.00093 (11)
Primary atom site location: structure-invariant direct methods

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

	x	y	z	U_iso*/U_eq
Br1	0.30362 (13)	0.43988 (8)	0.2401 (2)	0.0615 (4)
I2	0.54556 (10)	0.36925 (4)	0.26460 (13)	0.0583 (3)
Br3	0.73278 (12)	0.49074 (7)	0.26614 (18)	0.0561 (4)
C1	0.4175 (11)	0.4967 (7)	0.2453 (16)	0.035 (3)
C2	0.5191 (11)	0.4723 (6)	0.2535 (13)	0.033 (3)
C3	0.5960 (11)	0.5182 (6)	0.2557 (17)	0.038 (3)
C4	0.5754 (12)	0.5862 (6)	0.2478 (17)	0.040 (3)
H4A	0.6264	0.6171	0.2474	0.048*
C5	0.4763 (13)	0.6050 (7)	0.2405 (15)	0.046 (4)
C6	0.3965 (12)	0.5642 (7)	0.2397 (18)	0.048 (4)
H6A	0.3307	0.5809	0.2355	0.057*
N1	0.4555 (13)	0.6807 (6)	0.2380 (17)	0.065 (3)
O1	0.5145 (11)	0.7161 (5)	0.2088 (17)	0.085 (4)
O2	0.3795 (15)	0.6989 (5)	0.2557 (18)	0.105 (4)
Br11	−0.18918 (13)	0.30721 (8)	0.2488 (2)	0.0620 (4)
I12	0.04866 (10)	0.37922 (4)	0.26639 (13)	0.0593 (3)
Br13	0.24427 (12)	0.25893 (8)	0.2825 (2)	0.0588 (4)
C11	−0.0736 (11)	0.2509 (7)	0.2562 (17)	0.039 (3)
C12	0.0237 (12)	0.2769 (7)	0.2619 (14)	0.035 (3)
C13	0.1046 (11)	0.2312 (6)	0.2672 (18)	0.039 (3)
C14	0.0869 (13)	0.1639 (6)	0.2665 (18)	0.045 (4)
H14A	0.1429	0.1344	0.2736	0.054*
C15	−0.0137 (13)	0.1391 (8)	0.2553 (16)	0.045 (4)
C16	−0.0922 (13)	0.1829 (6)	0.2507 (18)	0.043 (4)
H16A	−0.1596	0.1668	0.2437	0.052*
N11	−0.0302 (15)	0.0681 (6)	0.2483 (17)	0.066 (4)
O11	0.0350 (12)	0.0323 (6)	0.2418 (18)	0.099 (4)
O12	−0.1106 (14)	0.0493 (6)	0.2609 (17)	0.099 (4)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.0558 (8)	0.0680 (9)	0.0684 (9)	−0.0167 (7)	0.0437 (7)	−0.0035 (7)
I2	0.0737 (6)	0.0268 (4)	0.0723 (7)	0.0048 (5)	0.0464 (5)	0.0017 (4)
Br3	0.0484 (7)	0.0636 (9)	0.0654 (9)	0.0047 (7)	0.0409 (7)	0.0002 (7)
C1	0.041 (7)	0.035 (7)	0.033 (6)	−0.012 (6)	0.027 (5)	−0.007 (5)
C2	0.043 (7)	0.017 (6)	0.035 (8)	0.002 (5)	0.024 (6)	0.000 (4)
C3	0.042 (6)	0.033 (7)	0.041 (7)	0.003 (5)	0.028 (6)	−0.004 (5)
C4	0.037 (7)	0.036 (8)	0.048 (8)	−0.005 (6)	0.027 (6)	−0.003 (6)
C5	0.046 (7)	0.023 (7)	0.040 (8)	0.005 (6)	0.015 (6)	−0.002 (5)
C6	0.036 (7)	0.064 (10)	0.045 (8)	−0.003 (7)	0.027 (6)	−0.016 (7)
N1	0.066 (8)	0.031 (7)	0.075 (9)	0.010 (7)	0.036 (7)	−0.001 (6)
O1	0.091 (8)	0.030 (6)	0.108 (9)	−0.003 (6)	0.053 (7)	0.003 (6)
O2	0.163 (12)	0.050 (7)	0.137 (11)	0.050 (8)	0.112 (10)	0.016 (6)
Br11	0.0522 (8)	0.0681 (9)	0.0685 (9)	0.0108 (7)	0.0404 (7)	−0.0033 (7)
I12	0.0755 (6)	0.0283 (4)	0.0735 (7)	−0.0069 (5)	0.0479 (5)	−0.0038 (4)
Br13	0.0488 (7)	0.0631 (9)	0.0703 (9)	−0.0088 (7)	0.0412 (7)	−0.0014 (7)
C11	0.043 (7)	0.035 (7)	0.041 (7)	−0.002 (6)	0.028 (6)	0.002 (6)
C12	0.041 (7)	0.033 (8)	0.039 (8)	0.007 (6)	0.030 (6)	0.004 (4)
C13	0.033 (6)	0.037 (8)	0.042 (7)	−0.005 (5)	0.022 (6)	−0.005 (6)
C14	0.051 (8)	0.029 (7)	0.044 (8)	0.008 (6)	0.025 (6)	0.000 (6)
C15	0.063 (9)	0.028 (7)	0.056 (9)	−0.015 (6)	0.045 (8)	−0.006 (5)
C16	0.046 (7)	0.031 (7)	0.042 (7)	−0.021 (6)	0.024 (6)	−0.015 (5)
N11	0.096 (10)	0.034 (7)	0.073 (9)	−0.018 (7)	0.057 (8)	−0.006 (6)
O11	0.101 (9)	0.029 (6)	0.147 (11)	−0.010 (6)	0.072 (8)	−0.005 (7)
O12	0.144 (11)	0.061 (7)	0.130 (10)	−0.042 (8)	0.106 (9)	−0.012 (6)

Geometric parameters (Å, º) top

Br1—C1	1.894 (12)	Br11—C11	1.895 (14)
I2—C2	2.088 (12)	I12—C12	2.074 (14)
Br3—C3	1.875 (13)	Br13—C13	1.888 (13)
C1—C6	1.375 (18)	C11—C12	1.387 (17)
C1—C2	1.416 (17)	C11—C16	1.381 (18)
C2—C3	1.380 (17)	C12—C13	1.405 (17)
C3—C4	1.384 (16)	C13—C14	1.370 (16)
C4—C5	1.353 (18)	C14—C15	1.390 (19)
C4—H4A	0.9300	C14—H14A	0.9300
C5—C6	1.35 (2)	C15—C16	1.359 (19)
C5—N1	1.539 (18)	C15—N11	1.435 (19)
C6—H6A	0.9300	C16—H16A	0.9300
N1—O2	1.199 (17)	N11—O11	1.168 (19)
N1—O1	1.221 (19)	N11—O12	1.226 (18)

C6—C1—C2	120.8 (13)	C12—C11—C16	121.2 (14)
C6—C1—Br1	116.4 (11)	C12—C11—Br11	121.4 (11)
C2—C1—Br1	122.8 (10)	C16—C11—Br11	117.3 (11)
C3—C2—C1	118.1 (12)	C11—C12—C13	117.3 (13)
C3—C2—I2	123.6 (10)	C11—C12—I12	120.7 (11)
C1—C2—I2	118.4 (10)	C13—C12—I12	122.0 (10)
C2—C3—C4	122.0 (13)	C14—C13—C12	120.8 (13)
C2—C3—Br3	121.2 (10)	C14—C13—Br13	117.0 (11)
C4—C3—Br3	116.8 (11)	C12—C13—Br13	122.2 (10)
C5—C4—C3	115.9 (13)	C13—C14—C15	120.8 (14)
C5—C4—H4A	122.0	C13—C14—H14A	119.6
C3—C4—H4A	122.0	C15—C14—H14A	119.6
C4—C5—C6	126.6 (14)	C16—C15—C14	118.8 (14)
C4—C5—N1	116.2 (15)	C16—C15—N11	122.8 (14)
C6—C5—N1	117.2 (15)	C14—C15—N11	118.3 (15)
C5—C6—C1	116.7 (13)	C15—C16—C11	121.0 (14)
C5—C6—H6A	121.7	C15—C16—H16A	119.5
C1—C6—H6A	121.7	C11—C16—H16A	119.5
O2—N1—O1	126.4 (14)	O11—N11—O12	124.2 (16)
O2—N1—C5	117.6 (14)	O11—N11—C15	120.6 (18)
O1—N1—C5	115.9 (17)	O12—N11—C15	115.0 (15)

C6—C1—C2—C3	0.0 (16)	C16—C11—C12—C13	−1.7 (16)
Br1—C1—C2—C3	179.7 (9)	Br11—C11—C12—C13	180.0 (9)
C6—C1—C2—I2	179.4 (9)	C16—C11—C12—I12	179.2 (9)
Br1—C1—C2—I2	−1.0 (12)	Br11—C11—C12—I12	0.8 (13)
C1—C2—C3—C4	−0.8 (17)	C11—C12—C13—C14	0.1 (17)
I2—C2—C3—C4	179.9 (9)	I12—C12—C13—C14	179.2 (9)
C1—C2—C3—Br3	−179.9 (9)	C11—C12—C13—Br13	−178.2 (9)
I2—C2—C3—Br3	0.7 (14)	I12—C12—C13—Br13	0.9 (14)
C2—C3—C4—C5	0.9 (18)	C12—C13—C14—C15	1.7 (19)
Br3—C3—C4—C5	−179.9 (9)	Br13—C13—C14—C15	−179.9 (10)
C3—C4—C5—C6	−0.2 (18)	C13—C14—C15—C16	−1.9 (18)
C3—C4—C5—N1	178.2 (11)	C13—C14—C15—N11	177.8 (12)
C4—C5—C6—C1	−0.5 (19)	C14—C15—C16—C11	0.3 (18)
N1—C5—C6—C1	−178.9 (10)	N11—C15—C16—C11	−179.5 (12)
C2—C1—C6—C5	0.6 (17)	C12—C11—C16—C15	1.6 (19)
Br1—C1—C6—C5	−179.1 (9)	Br11—C11—C16—C15	180.0 (10)
C4—C5—N1—O2	−171.0 (13)	C16—C15—N11—O11	175.7 (14)
C6—C5—N1—O2	7.6 (18)	C14—C15—N11—O11	−4 (2)
C4—C5—N1—O1	12.4 (17)	C16—C15—N11—O12	−8.3 (19)
C6—C5—N1—O1	−169.1 (12)	C14—C15—N11—O12	171.9 (13)

Halogen-bond geometry (Å, °) for (I) top

X₁···X₂	d	θ₁	θ₂	bond type
Br2···Br11	3.642 (3)	165.2 (5)	82.3 (5)	II-polarized
Br1···Br1ⁱ	3.731 (4)	133.3 (4)	133.3 (4)	I-unpolarized
Br2···Br13ⁱⁱ	3.781 (3)	126.8 (4)	129.6 (4)	I-unpolarized

Notes: d = separation X₁···X₂; θ₁ = angle C—X₁···X₂; θ₂ = angle X₁···X₂—C. For halogen bond types, see: Reddy et al. (2006). Symmetry codes: (i) -x, 1 - y, -z; (ii) -x, -y, 1 - z.

Halogen-bond geometry (Å, °) for (II) top

X₁···X₂	d	θ₁	θ₂	bond type
Br1···I12	3.813 (2)	161.2 (4)	117.2 (4)	II-polarized
I2···Br11ⁱ	3.893 (2)	116.6 (4)	161.8 (4)	II-polarized
Br1···Br13	3.787 (2)	142.8 (4)	122.9 (4)	I-unpolarized
Br11···Br3ⁱⁱ	3.858 (2)	143.9 (4)	124.4 (4)	I-unpolarized

Notes: d = separation X₁···X₂; θ₁ = angle C—X₁···X₂; θ₂ = angle X₁···X₂—C. For halogen bond types, see: Reddy et al. (2006). Symmetry codes: (i) 1 + x, y, z; (ii) -1 + x, y, z.

Acknowledgements

We acknowledge the contribution of Angélica Navarrete to the synthesis of the reported compounds.

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Volume 71| Part 8| August 2015| Pages 960-964

https://doi.org/10.1107/S2056989015013377

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research communications\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Anomalous halogen bonds in the crystal structures of 1,2,3-tri­bromo-5-nitro­benzene and 1,3-di­bromo-2-iodo-5-nitro­benzene

1. Chemical context

2. Structural commentary

3. Supra­molecular features

4. Database survey

5. Synthesis and crystallization

6. Refinement

Supporting information

Acknowledgements

References

research communications

Anomalous halogen bonds in the crystal structures of 1,2,3-tribromo-5-nitrobenzene and 1,3-dibromo-2-iodo-5-nitrobenzene

3. Supramolecular features