2,6-Di­bromo-4-nitro­benzo­nitrile

Noland, W.E.; Tritch, K.J.

doi:10.1107/S2414314617016170

organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 2| Part 11| November 2017| x171617

https://doi.org/10.1107/S2414314617016170

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2,6-Dibromo-4-nitrobenzonitrile

Wayland E. Noland ^a ^* and Kenneth J. Tritch ^a

^aDepartment of Chemistry, University of Minnesota, 207 Pleasant St SE, Minneapolis, MN 55455, USA
^*Correspondence e-mail: nolan001@umn.edu

Edited by J. Simpson, University of Otago, New Zealand (Received 2 November 2017; accepted 9 November 2017; online 17 November 2017)

Molecules of the title compound, C₇H₂Br₂N₂O₂, have C_2v symmetry and each lie on a twofold axis that bisects the benzene ring and its nitro and cyano substituents. The cyano N atom is bisected by two CN⋯Br contacts, and the nitro O atoms participate in weak C—H⋯O hydrogen bonds. These interactions form a planar sheet structure that stacks about a glide plane. This stacking mode has not been previously reported with cyano-halo-derived sheets of this type.

Keywords: crystal structure; nitrile; CN⋯Br contacts; C—H⋯O hydrogen bonds.

CCDC reference: 1580005

Structure description

The title nitrile (I) is presented as part of an ongoing packing study of 2,6-dihalobenzonitriles. Molecules of (I) have typical geometry (Fig. 1). The major axis of each molecule (connecting N4 and N7) lies on a twofold axis, two orthogonal mirror planes, and a glide plane. Thus, molecules have C_2v point symmetry and are planar. The cyano groups are bisected by two symmetry-related C7≡N7⋯Br2 contacts (Table 1), forming ribbons of R₂²(10) inversion dimers along [001]. Adjacent ribbons are related by an [010] translation, giving a planar sheet structure parallel to (100) (Fig. 2a). This sheet is similar to those reported for 2,4,6-tribromobenzonitrile (II) (Fig. 2b; Britton et al., 2016 ) and 2,6-dibromo-4-chlorobenzonitrile (III), (Fig. 2c; Britton, 2005 ). The relative displacement of molecules in the different sheets is consistent with the geometries of the 4-substituents. In (II) and (III), there are no short contacts between adjacent ribbons. By contrast, adjacent ribbons in (I) are connected by weak C3—H3A⋯O1 hydrogen bonds that form chains of R₂²(10) inversion dimers along [001], informally mirroring the CN⋯Br contacts (Table 1). In the crystal of (I), sheets stack about glide planes (Fig. 3a), a stacking mode not yet observed in this series. Three polytypes of (II) were reported with combinations of centric (Fig. 3b) and translational stacking. Crystals of (III) had only translational (Fig. 3c) stacking.

Table 1
Contact geometry (Å, °).

A—B⋯C	A—B	B⋯C	A⋯C	A—B⋯C
C7≡N7⋯Br2ⁱ	1.151 (3)	3.1508 (9)	3.8640 (1)	120.49 (3)
C3—H3A⋯O1ⁱⁱ	0.95	2.493	3.409 (2)	161.82
Symmetry codes: (i) −x + 1, −y + 2, −z + 1; (ii) x, −y + 1, −z + 1.

Figure 1
The molecular structure of (I), showing the atomic numbering and displacement ellipsoids at the 50% probability level. Unlabelled atoms are related by twofold and mirror symmetry.

Figure 2
Space-filling drawings of the sheet structures in (a) 4-nitro nitrile (I), viewed along [100]; (b) the Z = 8 polytype of 4-bromo nitrile (II), viewed along [100]; (c) 4-chloro nitrile (III), viewed along [ $[\overline{1}]$ 02].

Figure 3
The three stacking modes observed for the given sheet structure: (a) glide stacking between adjacent sheets in (I), viewed along [100]; (b) centric stacking between alternating sheet pairs in the Z = 8 polytype of (II), viewed along [100]; (c) translational stacking between adjacent sheets in (III), viewed along [ $[\overline{1}]$ 02]. Dashed magenta lines represent short contacts in the front layer. Molecules in the rear layer are drawn with smaller balls and sticks, lower opacity, and green dashed lines representing short contacts.

Synthesis and crystallization

4-Nitroaniline (2.57 g; Acros Organics Co., No. 12837) was brominated (Br₂, 2.1 ml) in acetic acid (100 ml) at 350 K for 6 h. The resulting mixture was cooled to room temperature. A precipitate was collected by filtration, and then neutralized in a mixture of saturated aqueous NaHSO₃ (20 ml) and Na₂CO₃ (100 ml), water (50 ml), and ethyl acetate (300 ml). The organic portion was concentrated on a rotary evaporator, and then recrystallized from chloroform, giving 2,6-dibromo-4-nitroaniline as yellow needles [84% yield, m.p. 480–481 K (lit. 476–477 K; Podgoršek et al., 2009 )]. A portion (570 mg) was cyanated according to the Sandmeyer procedure described by Britton et al. (2016), giving (I) as an off-white powder (35% yield, m.p. 466–467 K). ¹H NMR (400 MHz, DMSO-d₆) δ 8.68 (s, H3A); ¹³C NMR (101 MHz, DMSO-d₆) δ 150.0 (C4), 127.3 (C2), 126.8 (C3), 122.9 (C1), 115.5 (C7); IR (KBr, cm⁻¹) 3098, 2232, 1525, 1345, 1278, 1095, 903, 783, 751, 621. Crystals were prepared by slow evaporation of a solution in chloroform, followed by decantation, and then washing with pentane.

Refinement

Crystal data, data collection, and structure refinement details are summarized in Table 2.

Table 2
Experimental details

Crystal data
Chemical formula	C₇H₂Br₂N₂O₂
M_r	305.93
Crystal system, space group	Orthorhombic, Cmcm
Temperature (K)	100
a, b, c (Å)	6.4256 (2), 12.3231 (5), 11.1117 (4)
V (Å³)	879.86 (6)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	9.18
Crystal size (mm)	0.22 × 0.15 × 0.11

Data collection
Diffractometer	Bruker VENTURE PHOTON-II
Absorption correction	Multi-scan (SADABS; Sheldrick, 1996 )
T_min, T_max	0.249, 0.344
No. of measured, independent and observed [I > 2σ(I)] reflections	10626, 1195, 1060
R_int	0.027
(sin θ/λ)_max (Å⁻¹)	0.835

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.014, 0.035, 1.08
No. of reflections	1195
No. of parameters	46
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.64, −0.43
Computer programs: APEX3 and SAINT (Bruker, 2012 ), SHELXT2014 (Sheldrick, 2015a ), SHELXL2014 (Sheldrick, 2015b ), Mercury (Macrae et al., 2008 ) and publCIF (Westrip, 2010 ).

Structural data

CCDC reference: 1580005

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314617016170/sj4146sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314617016170/sj4146Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314617016170/sj4146Isup3.cml

checkCIF report

Computing details top

Data collection: APEX3 (Bruker, 2012); cell refinement: SAINT (Bruker, 2012); data reduction: SAINT (Bruker, 2012); program(s) used to solve structure: SHELXT2014 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: Mercury (Macrae et al., 2008); software used to prepare material for publication: publCIF (Westrip, 2010).

2,6-Dibromo-4-nitrobenzonitrile top

Crystal data top

C₇H₂Br₂N₂O₂	D_x = 2.309 Mg m⁻³
M_r = 305.93	Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, Cmcm	Cell parameters from 2992 reflections
a = 6.4256 (2) Å	θ = 3.3–36.1°
b = 12.3231 (5) Å	µ = 9.18 mm⁻¹
c = 11.1117 (4) Å	T = 100 K
V = 879.86 (6) Å³	Square bipyramid, colorless
Z = 4	0.22 × 0.15 × 0.11 mm
F(000) = 576

Data collection top

Bruker VENTURE PHOTON-II diffractometer	1060 reflections with I > 2σ(I)
Radiation source: micro-focus	R_int = 0.027
φ and ω scans	θ_max = 36.4°, θ_min = 3.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −10→10
T_min = 0.249, T_max = 0.344	k = −20→20
10626 measured reflections	l = −18→18
1195 independent reflections

Refinement top

Refinement on F²	Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: full	H-atom parameters constrained
R[F² > 2σ(F²)] = 0.014	w = 1/[σ²(F_o²) + (0.0108P)² + 0.7137P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.035	(Δ/σ)_max = 0.001
S = 1.08	Δρ_max = 0.64 e Å⁻³
1195 reflections	Δρ_min = −0.43 e Å⁻³
46 parameters	Extinction correction: SHELXL2014 (Sheldrick, 2015b), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0055 (4)

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

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

	x	y	z	U_iso*/U_eq
Br2	0.5000	0.83929 (2)	0.49434 (2)	0.01475 (5)
O1	0.5000	0.43194 (8)	0.65277 (9)	0.0238 (2)
N4	0.5000	0.47860 (12)	0.7500	0.0148 (3)
N7	0.5000	1.03098 (14)	0.7500	0.0193 (3)
C1	0.5000	0.82086 (13)	0.7500	0.0118 (3)
C2	0.5000	0.76354 (9)	0.64089 (10)	0.01227 (19)
C3	0.5000	0.65122 (9)	0.63981 (10)	0.01287 (19)
H3A	0.5000	0.6119	0.5663	0.015*
C4	0.5000	0.59809 (13)	0.7500	0.0120 (3)
C7	0.5000	0.93761 (15)	0.7500	0.0146 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br2	0.01902 (7)	0.01452 (6)	0.01072 (6)	0.000	0.000	0.00282 (4)
O1	0.0424 (6)	0.0139 (4)	0.0150 (4)	0.000	0.000	−0.0038 (3)
N4	0.0189 (6)	0.0118 (6)	0.0136 (6)	0.000	0.000	0.000
N7	0.0246 (8)	0.0154 (6)	0.0178 (6)	0.000	0.000	0.000
C1	0.0124 (6)	0.0099 (6)	0.0130 (6)	0.000	0.000	0.000
C2	0.0140 (4)	0.0128 (4)	0.0100 (4)	0.000	0.000	0.0010 (3)
C3	0.0153 (5)	0.0128 (5)	0.0105 (4)	0.000	0.000	−0.0002 (3)
C4	0.0142 (6)	0.0106 (6)	0.0110 (6)	0.000	0.000	0.000
C7	0.0140 (7)	0.0167 (7)	0.0130 (6)	0.000	0.000	0.000

Geometric parameters (Å, º) top

Br2—C2	1.8770 (11)	C1—C2ⁱ	1.4031 (14)
O1—N4	1.2239 (12)	C1—C7	1.439 (2)
N4—O1ⁱ	1.2239 (12)	C2—C3	1.3842 (17)
N4—C4	1.473 (2)	C3—C4	1.3884 (13)
N7—C7	1.151 (3)	C3—H3A	0.9500
C1—C2	1.4031 (14)	C4—C3ⁱ	1.3885 (13)

O1ⁱ—N4—O1	123.96 (16)	C1—C2—Br2	119.95 (9)
O1ⁱ—N4—C4	118.02 (8)	C2—C3—C4	117.63 (11)
O1—N4—C4	118.02 (8)	C2—C3—H3A	121.2
C2—C1—C2ⁱ	119.55 (15)	C4—C3—H3A	121.2
C2—C1—C7	120.23 (7)	C3—C4—C3ⁱ	123.74 (15)
C2ⁱ—C1—C7	120.23 (7)	C3—C4—N4	118.13 (7)
C3—C2—C1	120.72 (11)	C3ⁱ—C4—N4	118.13 (7)
C3—C2—Br2	119.32 (8)	N7—C7—C1	180.0

C2ⁱ—C1—C2—C3	0.000 (1)	C2—C3—C4—C3ⁱ	0.000 (1)
C7—C1—C2—C3	180.000 (1)	C2—C3—C4—N4	180.000 (1)
C2ⁱ—C1—C2—Br2	180.000 (1)	O1ⁱ—N4—C4—C3	180.000 (1)
C7—C1—C2—Br2	0.000 (1)	O1—N4—C4—C3	0.000 (1)
C1—C2—C3—C4	0.000 (1)	O1ⁱ—N4—C4—C3ⁱ	0.000 (1)
Br2—C2—C3—C4	180.000 (1)	O1—N4—C4—C3ⁱ	180.000 (1)

Symmetry code: (i) x, y, −z+3/2.

Contact geometry (Å, °). top

A—B···C	A—B	B···C	A···C	A—B···C
C7≡N7···Br2ⁱ	1.151 (3)	3.1508 (9)	3.8640 (1)	120.49 (3)
C3—H3A···O1ⁱⁱ	0.95	2.493	3.409 (2)	161.82

Symmetry codes: (i) -x + 1, -y + 2, -z + 1; (ii) x, -y + 1, -z + 1.

Acknowledgements

The authors thank Victor G. Young, Jr (X-Ray Crystallographic Laboratory, University of Minnesota) for assistance with the crystallographic determination, the Wayland E. Noland Research Fellowship Fund at the University of Minnesota Foundation for generous financial support of this project, and Doyle Britton (deceased July 7, 2015) for providing the basis of this project.

References

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