3,5-Di­bromo­benzo­nitrile

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

doi:10.1107/S2414314618000597

organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 3| Part 1| January 2018| x180059

https://doi.org/10.1107/S2414314618000597

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3,5-Dibromobenzonitrile

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 8 January 2018; accepted 9 January 2018; online 12 January 2018)

Molecules of the title compound (I), C₇H₃Br₂N, lie on a crystallographic mirror plane that bisects the benzene ring and the cyano group. In the crystal, no C≡N⋯Br or Br⋯Br short contacts are observed. Head-to-tail C(7) chains form based on weak hydrogen bonding between the the para H atom and the cyano N atom. Although molecules of (I) pack differently than 3,5-difluorobenzonitrile, both compounds have similarly distorted benzene rings. For (I), the endocyclic bond angles are 121.16 (16)° and 117.78 (16)° about the ipso and para C atoms, respectively.

Keywords: crystal structure; nitrile; C—H⋯N hydrogen bonds; C≡N⋯H contacts.

CCDC reference: 1580004

Structure description

Cyano–halo (C≡N⋯X) short contacts are commonly observed in crystals of halogenated benzonitriles, especially when X = Br or I. The strength of these contacts correlates with halogen polarizability (Desiraju & Harlow, 1989 ). Depending on the nature of the 4-substituent, 2,6-dibromo-3,5-unsubstituted benzonitriles usually form sheet structures based on each cyano group being bisected by two C≡N⋯Br contacts (Noland & Tritch, 2017 ), or have Br⋯Br contacts as the primary supramolecular interaction (Noland et al., 2017 ). As of the most recent update of the Cambridge Structural Database (Version 5.37, May 2017; Groom et al., 2016 ), 3,5-difluorobenzonitrile is the only example with the X and H atoms transposed from the former arrangement (Britton, 2002 ). Our objective was to determine whether the title nitrile (I) would be isomorphous with 3,5-difluorobenzonitrile, or if a packing motif based on C≡N⋯Br or Br⋯Br interactions would be observed.

Although the planarity of molecules of (I) (Fig. 1) is not crystallographically imposed, the mean deviation of ring atoms (C1–C4) from the best-fit plane is less than 0.001 (1) Å. Interestingly, neither C≡N⋯Br nor Br⋯Br short contacts are observed in the crystal of (I). Instead, C(7) head-to-tail chains of weak C4—H4⋯N7 hydrogen bonds form (Table 1). Chains of this type are commonly observed from 4-halobenzonitriles as C≡N⋯X contacts (Desiraju & Harlow, 1989). In the title crystal, the C(7) chains form along [10 $[\overline{1}]$ ] and align to form translationally stacked sheets parallel to (101) (Fig. 2a). Adjacent chains within each sheet are antiparallel (Fig. 3), whereas corresponding chains in adjacent sheets are parallel. This differs greatly from the packing of 3,5-difluorobenzonitrile (Fig. 2b), in which a sheet structure forms based on cyano N atoms bisected by weak C—H⋯N hydrogen bonds with ortho H atoms. Weak F⋯F contacts were observed in the difluoro analog, adding to the surprise that (I) does not form Br⋯Br short contacts. Even though (I) and the difluoro analog pack differently, the benzene rings in both molecules are similarly distorted (Fig. 2), supporting Britton's hypothesis that these distortions are mainly due to intramolecular substituent effects, rather than supramolecular effects in the crystals (Britton, 2002).

Table 1
Contact geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C4—H4⋯N7ⁱ	0.95	2.51	3.443 (3)	168
Symmetry code: (i) 1 + x, y, −1 + z.

Figure 1
The molecular structure of (I), showing the atomic numbering and displacement ellipsoids at the 50% probability level. Unlabelled atoms are related by the (x, $[{1\over 2}]$ − y, z) symmetry operation.

Figure 2
The sheet structures in crystals of (a) compound (I), viewed along [301]; (b) 3,5-difluorobenzonitrile, viewed roughly along [100]. Bond angles about the ortho and meta C atoms are denoted in light blue. Dashed magenta lines represent short contacts.

Figure 3
The arrangement of C(7) chains in the crystal of (I), viewed roughly along [101]. Dashed magenta lines represent short contacts.

Synthesis and crystallization

3,5-Dibromobenzonitrile (I): 3,5-Dibromobenzamide [(II), Fig. 4] (Sigma–Aldrich, Inc. No. 680389; 962 mg), dichloromethane (30 ml), and triethylamine (1.4 ml) were combined in a round-bottomed flask. The resulting mixture was stirred at 290 K. POCl₃ (320 µL) was added dropwise. After 4 h, the reaction mixture was washed with hydrochloric acid (1 M, 2 × 25 ml), and then NaHCO₃ solution (0.5 M, 50 ml). The organic portion was filtered through basic alumina (4 cm × 2 cm, length × diameter). The filter was washed with dichloromethane (20 ml). The combined filtrate was concentrated in a rotary evaporator, giving an off-white powder (750 mg, 83%). Crystals suitable for X-ray diffraction (colourless needles) were prepared by slow evaporation of a solution in chloroform and cyclohexane, followed by decantation, and then washing with pentane. M.p. 367–368 K (lit. 368–369 K; Ishii et al., 2013 ); ¹H NMR (500 MHz, CDCl₃) δ 7.917 (t, J = 1.8 Hz, 1H, H4), 7.739 (d, J = 1.8 Hz, 2H, H2); ¹³C NMR (126 MHz, CDCl₃) δ 139.0 (1 C, C4), 133.6 (2 C, C2), 123.7 (2 C, C3), 116.0 (1 C, C7), 115.6 (1 C, C1); IR (KBr, cm⁻¹) 3072, 2961, 2922, 2236, 1551, 1418, 1198, 1109, 864, 759, 666; MS (EI, m/z) M⁺ calculated for C₇H₃⁸¹Br⁷⁹BrN 260.8606, found 260.8605.

Figure 4
The synthesis of (I).

Refinement

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

Table 2
Experimental details

Crystal data
Chemical formula	C₇H₃Br₂N
M_r	260.92
Crystal system, space group	Monoclinic, P2₁/m
Temperature (K)	100
a, b, c (Å)	4.0047 (2), 13.2585 (8), 7.3356 (4)
β (°)	97.440 (3)
V (Å³)	386.21 (4)
Z	2
Radiation type	Mo Kα
μ (mm⁻¹)	10.41
Crystal size (mm)	0.20 × 0.07 × 0.05

Data collection
Diffractometer	Bruker AXS VENTURE PHOTON-II
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.231, 0.625
No. of measured, independent and observed [I > 2σ(I)] reflections	8873, 1945, 1696
R_int	0.036
(sin θ/λ)_max (Å⁻¹)	0.834

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.024, 0.058, 1.07
No. of reflections	1945
No. of parameters	53
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.98, −0.49
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: 1580004

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314618000597/sj4154sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314618000597/sj4154Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314618000597/sj4154Isup3.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).

3,5-Dibromobenzonitrile top

Crystal data top

C₇H₃Br₂N	D_x = 2.244 Mg m⁻³
M_r = 260.92	Melting point: 367 K
Monoclinic, P2₁/m	Mo Kα radiation, λ = 0.71073 Å
a = 4.0047 (2) Å	Cell parameters from 2765 reflections
b = 13.2585 (8) Å	θ = 2.8–36.4°
c = 7.3356 (4) Å	µ = 10.41 mm⁻¹
β = 97.440 (3)°	T = 100 K
V = 386.21 (4) Å³	Needle, colourless
Z = 2	0.20 × 0.07 × 0.05 mm
F(000) = 244

Data collection top

Bruker AXS VENTURE PHOTON-II diffractometer	1696 reflections with I > 2σ(I)
Radiation source: micro-focus	R_int = 0.036
φ and ω scans	θ_max = 36.4°, θ_min = 2.8°
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	h = −6→6
T_min = 0.231, T_max = 0.625	k = −20→22
8873 measured reflections	l = −12→12
1945 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)] = 0.024	w = 1/[σ²(F_o²) + (0.0202P)² + 0.2462P] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.058	(Δ/σ)_max = 0.001
S = 1.07	Δρ_max = 0.98 e Å⁻³
1945 reflections	Δρ_min = −0.49 e Å⁻³
53 parameters	Extinction correction: SHELXL2014 (Sheldrick, 2015b), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0102 (18)

Special details top

Experimental. Dr. K. J. Tritch / Prof. W. E. Noland

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
Br3	0.84613 (4)	0.46259 (2)	0.21614 (2)	0.02026 (6)
N7	0.2774 (5)	0.2500	0.8775 (3)	0.0261 (4)
C1	0.5455 (5)	0.2500	0.5751 (2)	0.0136 (3)
C2	0.6134 (3)	0.34183 (11)	0.49387 (18)	0.0148 (2)
H2	0.5664	0.4041	0.5495	0.018*
C3	0.7512 (3)	0.33975 (11)	0.32980 (18)	0.0143 (2)
C4	0.8227 (5)	0.2500	0.2449 (3)	0.0150 (3)
H4	0.9172	0.2500	0.1326	0.018*
C7	0.3995 (5)	0.2500	0.7444 (3)	0.0175 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br3	0.02244 (8)	0.01753 (8)	0.02213 (8)	−0.00043 (5)	0.00792 (5)	0.00604 (5)
N7	0.0229 (9)	0.0394 (12)	0.0169 (8)	0.000	0.0062 (7)	0.000
C1	0.0129 (7)	0.0181 (8)	0.0105 (6)	0.000	0.0039 (5)	0.000
C2	0.0148 (5)	0.0158 (6)	0.0141 (5)	0.0004 (4)	0.0036 (4)	−0.0005 (4)
C3	0.0139 (5)	0.0159 (6)	0.0136 (5)	−0.0001 (4)	0.0035 (4)	0.0021 (4)
C4	0.0151 (7)	0.0180 (8)	0.0123 (7)	0.000	0.0036 (6)	0.000
C7	0.0167 (8)	0.0213 (9)	0.0147 (8)	0.000	0.0031 (6)	0.000

Geometric parameters (Å, º) top

Br3—C3	1.8906 (13)	C2—C3	1.3878 (18)
N7—C7	1.147 (3)	C2—H2	0.9500
C1—C2ⁱ	1.3977 (16)	C3—C4	1.3898 (17)
C1—C2	1.3977 (16)	C4—C3ⁱ	1.3898 (17)
C1—C7	1.439 (3)	C4—H4	0.9500

C2ⁱ—C1—C2	121.16 (16)	C2—C3—Br3	119.38 (11)
C2ⁱ—C1—C7	119.42 (8)	C4—C3—Br3	118.37 (10)
C2—C1—C7	119.42 (8)	C3ⁱ—C4—C3	117.78 (16)
C3—C2—C1	118.28 (13)	C3ⁱ—C4—H4	121.1
C3—C2—H2	120.9	C3—C4—H4	121.1
C1—C2—H2	120.9	N7—C7—C1	178.8 (2)
C2—C3—C4	122.25 (13)

C2ⁱ—C1—C2—C3	−0.1 (3)	C1—C2—C3—Br3	180.00 (12)
C7—C1—C2—C3	−179.38 (17)	C2—C3—C4—C3ⁱ	0.1 (3)
C1—C2—C3—C4	0.0 (2)	Br3—C3—C4—C3ⁱ	−179.91 (9)

Symmetry code: (i) x, −y+1/2, z.

Contact geometry (Å, °) top

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4···N7ⁱ	0.95	2.51	3.443 (3)	168

Symmetry code: (i) 1 + x, y, -1 + z.

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.

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