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ISSN: 2414-3146

2,6-Di­bromo-4-nitro­benzo­nitrile

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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 C2v 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.

3D view (loading...)
[Scheme 3D1]
Chemical scheme
[Scheme 1]

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[link]). 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 C2v point symmetry and are planar. The cyano groups are bis­ected by two symmetry-related C7≡N7⋯Br2 contacts (Table 1[link]), 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. 2[link]a). This sheet is similar to those reported for 2,4,6-tri­bromo­benzo­nitrile (II) (Fig. 2[link]b; Britton et al., 2016[Britton, D., Noland, W. E. & Tritch, K. J. (2016). Acta Cryst. E72, 178-183.]) and 2,6-di­bromo-4-chloro­benzo­nitrile (III), (Fig. 2[link]c; Britton, 2005[Britton, D. (2005). Acta Cryst. E61, o1726-o1727.]). 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[link]). In the crystal of (I), sheets stack about glide planes (Fig. 3[link]a), a stacking mode not yet observed in this series. Three polytypes of (II) were reported with combinations of centric (Fig. 3[link]b) and translational stacking. Crystals of (III) had only translational (Fig. 3[link]c) stacking.

Table 1
Contact geometry (Å, °).

ABC AB BC AC ABC
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]
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]
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]
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[Podgoršek, A., Stavber, S., Zupan, M. & Iskra, J. (2009). Tetrahedron, 65, 4429-4439.])]. A portion (570 mg) was cyanated according to the Sandmeyer procedure described by Britton et al. (2016[Britton, D., Noland, W. E. & Tritch, K. J. (2016). Acta Cryst. E72, 178-183.]), 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[link].

Table 2
Experimental details

Crystal data
Chemical formula C7H2Br2N2O2
Mr 305.93
Crystal system, space group Orthorhombic, Cmcm
Temperature (K) 100
a, b, c (Å) 6.4256 (2), 12.3231 (5), 11.1117 (4)
V3) 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[Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.])
Tmin, Tmax 0.249, 0.344
No. of measured, independent and observed [I > 2σ(I)] reflections 10626, 1195, 1060
Rint 0.027
(sin θ/λ)max−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
Δρmax, Δρmin (e Å−3) 0.64, −0.43
Computer programs: APEX3 and SAINT (Bruker, 2012[Bruker (2012). APEX2 and SAINT. Bruker AXS, Inc., Madison, Wisconsin, USA.]), SHELXT2014 (Sheldrick, 2015a[Sheldrick, G. M. (2015a). Acta Cryst. A71, 3-8.]), SHELXL2014 (Sheldrick, 2015b[Sheldrick, G. M. (2015b). Acta Cryst. C71, 3-8.]), Mercury (Macrae et al., 2008[Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466-470.]) and publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Structural data


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
C7H2Br2N2O2Dx = 2.309 Mg m3
Mr = 305.93Mo Kα radiation, λ = 0.71073 Å
Orthorhombic, CmcmCell parameters from 2992 reflections
a = 6.4256 (2) Åθ = 3.3–36.1°
b = 12.3231 (5) ŵ = 9.18 mm1
c = 11.1117 (4) ÅT = 100 K
V = 879.86 (6) Å3Square bipyramid, colorless
Z = 40.22 × 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-focusRint = 0.027
φ and ω scansθmax = 36.4°, θmin = 3.3°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 1010
Tmin = 0.249, Tmax = 0.344k = 2020
10626 measured reflectionsl = 1818
1195 independent reflections
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH-atom parameters constrained
R[F2 > 2σ(F2)] = 0.014 w = 1/[σ2(Fo2) + (0.0108P)2 + 0.7137P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.035(Δ/σ)max = 0.001
S = 1.08Δρmax = 0.64 e Å3
1195 reflectionsΔρmin = 0.43 e Å3
46 parametersExtinction correction: SHELXL2014 (Sheldrick, 2015b), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction 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
xyzUiso*/Ueq
Br20.50000.83929 (2)0.49434 (2)0.01475 (5)
O10.50000.43194 (8)0.65277 (9)0.0238 (2)
N40.50000.47860 (12)0.75000.0148 (3)
N70.50001.03098 (14)0.75000.0193 (3)
C10.50000.82086 (13)0.75000.0118 (3)
C20.50000.76354 (9)0.64089 (10)0.01227 (19)
C30.50000.65122 (9)0.63981 (10)0.01287 (19)
H3A0.50000.61190.56630.015*
C40.50000.59809 (13)0.75000.0120 (3)
C70.50000.93761 (15)0.75000.0146 (3)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br20.01902 (7)0.01452 (6)0.01072 (6)0.0000.0000.00282 (4)
O10.0424 (6)0.0139 (4)0.0150 (4)0.0000.0000.0038 (3)
N40.0189 (6)0.0118 (6)0.0136 (6)0.0000.0000.000
N70.0246 (8)0.0154 (6)0.0178 (6)0.0000.0000.000
C10.0124 (6)0.0099 (6)0.0130 (6)0.0000.0000.000
C20.0140 (4)0.0128 (4)0.0100 (4)0.0000.0000.0010 (3)
C30.0153 (5)0.0128 (5)0.0105 (4)0.0000.0000.0002 (3)
C40.0142 (6)0.0106 (6)0.0110 (6)0.0000.0000.000
C70.0140 (7)0.0167 (7)0.0130 (6)0.0000.0000.000
Geometric parameters (Å, º) top
Br2—C21.8770 (11)C1—C2i1.4031 (14)
O1—N41.2239 (12)C1—C71.439 (2)
N4—O1i1.2239 (12)C2—C31.3842 (17)
N4—C41.473 (2)C3—C41.3884 (13)
N7—C71.151 (3)C3—H3A0.9500
C1—C21.4031 (14)C4—C3i1.3885 (13)
O1i—N4—O1123.96 (16)C1—C2—Br2119.95 (9)
O1i—N4—C4118.02 (8)C2—C3—C4117.63 (11)
O1—N4—C4118.02 (8)C2—C3—H3A121.2
C2—C1—C2i119.55 (15)C4—C3—H3A121.2
C2—C1—C7120.23 (7)C3—C4—C3i123.74 (15)
C2i—C1—C7120.23 (7)C3—C4—N4118.13 (7)
C3—C2—C1120.72 (11)C3i—C4—N4118.13 (7)
C3—C2—Br2119.32 (8)N7—C7—C1180.0
C2i—C1—C2—C30.000 (1)C2—C3—C4—C3i0.000 (1)
C7—C1—C2—C3180.000 (1)C2—C3—C4—N4180.000 (1)
C2i—C1—C2—Br2180.000 (1)O1i—N4—C4—C3180.000 (1)
C7—C1—C2—Br20.000 (1)O1—N4—C4—C30.000 (1)
C1—C2—C3—C40.000 (1)O1i—N4—C4—C3i0.000 (1)
Br2—C2—C3—C4180.000 (1)O1—N4—C4—C3i180.000 (1)
Symmetry code: (i) x, y, z+3/2.
Contact geometry (Å, °). top
AB···CABB···CA···CAB···C
C7N7···Br2i1.151 (3)3.1508 (9)3.8640 (1)120.49 (3)
C3—H3A···O1ii0.952.4933.409 (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

First citationBritton, D. (2005). Acta Cryst. E61, o1726–o1727.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationBritton, D., Noland, W. E. & Tritch, K. J. (2016). Acta Cryst. E72, 178–183.  CSD CrossRef IUCr Journals Google Scholar
First citationBruker (2012). APEX2 and SAINT. Bruker AXS, Inc., Madison, Wisconsin, USA.  Google Scholar
First citationMacrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466–470.  Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
First citationPodgoršek, A., Stavber, S., Zupan, M. & Iskra, J. (2009). Tetrahedron, 65, 4429–4439.  Google Scholar
First citationSheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.  Google Scholar
First citationSheldrick, G. M. (2015a). Acta Cryst. A71, 3–8.  Web of Science CrossRef IUCr Journals Google Scholar
First citationSheldrick, G. M. (2015b). Acta Cryst. C71, 3–8.  Web of Science CrossRef IUCr Journals Google Scholar
First citationWestrip, S. P. (2010). J. Appl. Cryst. 43, 920–925.  Web of Science CrossRef CAS IUCr Journals Google Scholar

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