2,6-Di­bromo-4-chloro­phenyl isocyanide

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

doi:10.1107/S2414314617018193

organic compounds

IUCrDATA

ISSN: 2414-3146

Volume 3| Part 1| January 2018| x171819

https://doi.org/10.1107/S2414314617018193

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2,6-Dibromo-4-chlorophenyl isocyanide

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 17 December 2017; accepted 19 December 2017; online 9 January 2018)

Molecules of the title compound, C₇H₂Br₂ClN (RNC), are bisected by a mirror plane that passes through the chloro and isocyano groups. The isocyano C atom is bisected by two NC⋯Br contacts, one per Br atom. The resulting centric R²₂(10) rings form ribbons along [010], which align to form a nearly planar sheet structure that is very similar to the sheets observed in several related 2,6-dibromophenyl cyanides and isocyanides. The crystal of RNC is isomorphous with the corresponding cyanide, with solely translational stacking between sheets. This is in contrast to the 2,4,6-tribromophenyl cyanide and isocyanide, which occur as different polytypes.

Keywords: crystal structure; isocyanide; NC⋯Br contacts.

CCDC reference: 1812522

Structure description

The title isocyanide (RNC) is presented to add to the library of corresponding cyanide/isocyanide pairs in the study of cyano/isocyano–halo short contacts. The molecular structure of RNC (Fig. 1) has typical geometry, with the largest distortion being displacement of C14 toward the center of the benzene ring such that the C13—C14—C13′ angle is 122.2 (2)°. RNC is nearly planar, with a mean deviation of 0.002 (2) Å from the best-fit benzene plane for ring atoms (C11–C14), and 0.026 (3) Å for substituent atoms (Br11/Cl11/N11/C15). Centric N11≡C15⋯Br11 contacts are the main supramolecular interaction (Table 1). Two such contacts bisect each C15 atom, forming ribbons of R₂²(10) rings along [010]. Adjacent ribbons translate along [201], forming nearly-planar sheets parallel to ( $[\overline{1}]$ 02), with no short contacts between ribbons (Fig. 2). Adjacent sheets stack translationally. RNC is isomorphous with 2,6-dibromo-4-chlorobenzonitrile (RCN; Britton, 2005 ). This outcome answers a question about the polytypism observed in this series of 2,6-dibromo compounds. The most common (Z = 2) polytpe of 2,4,6-tribromobenzonitrile (Britton et al., 2016 ) is isomorphous with RCN and RNC. However, 2,4,6-tribromophenyl isocyanide is exclusively reported as a Z = 8 polytype with mixed translational and centric stacking. It was therefore postulated that RNC might also occur mainly or exclusively as the Z = 8 polytype, however, that structure has not yet been observed.

Table 1
Contact geometry (Å, °)

N≡C⋯Br	N≡C	C⋯Br	N≡C⋯Br
N11≡C15⋯Br11ⁱ	1.161 (4)	3.125 (2)	135.95 (3)
Symmetry code: (i) −x, 1 − y, 1 − z

Figure 1
The molecular structure of RNC, showing the atomic numbering and displacement ellipsoids at the 50% probability level. Unlabelled atoms are related by the (x, $[{3\over 2}]$ − y, z) symmetry operation.

Figure 2
The sheet structure of RNC, viewed along [20 $[\overline{1}]$ ]. For the four upper molecules, two adjacent layers are shown, illustrating the translational stacking mode. 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

RNC was prepared over 3 steps (Fig. 3). 4-Chloroaniline (3.50 g; Acros Organics Co., No. 10859) was brominated according to the procedure described by Noland & Tritch (2017 ), giving 2,6-dibromo-4-chloroaniline (RNH2) as colourless needles [61% yield, m.p. 364–366 K (lit. 366–368 K; Miura et al., 1998 )]; ¹H NMR (500 MHz, CDCl₃) δ 7.39 (s, 2H), 4.54 (s, 2H); ¹³C NMR (126 MHz, CDCl₃) δ 141.1, 131.4, 122.8, 108.6. A portion of the RNH2 (1.15 g) was formylated according to the procedure described by Britton et al. (2016), with dichloromethane in the place of tetrahydrofuran, giving 2,6-dibromo-4-chloroformanilide (RFA) as colourless needles (90% yield, m.p. 485–487 K dec.); ¹H NMR (500 MHz, DMSO-d6, 2 conformers obs.) δ 10.12 (s, 1H, major), 9.89 (s, 1H, minor), 8.30 (s, 1H, major), 8.10 (s, 1H, minor), 7.93 (s, 2H, both); ¹³C NMR (126 MHz, DMSO-d6) δ 159.6, 134.1, 133.2, 131.7, 124.2. A portion of the RFA (313 mg) was dehydrated according to the procedure described by Britton et al. (2016), with dichloromethane in the place of 1,2-dichloroethane, giving RNC as a brown powder. 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 (78% yield, m.p. 377–378 K); ¹H NMR (500 MHz, CD₂Cl₂) δ 7.69 (s, H13A); ¹³C NMR (126 MHz, CD₂Cl₂) δ 174.7 (C15), 136.4 (C14), 132.6 (C13), 127.4 (C11), 121.7 (C12); IR (KBr, cm⁻¹) 3074, 2132, 1578, 1561, 1540, 1433, 1375, 1117, 857, 840, 749, 661.

Figure 3
The synthesis of RNC.

Refinement

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

Table 2
Experimental details

Crystal data
Chemical formula	C₇H₂Br₂ClN
M_r	295.37
Crystal system, space group	Monoclinic, P2₁/m
Temperature (K)	100
a, b, c (Å)	4.7215 (4), 10.0181 (9), 8.7689 (8)
β (°)	93.023 (4)
V (Å³)	414.20 (6)
Z	2
Radiation type	Mo Kα
μ (mm⁻¹)	10.03
Crystal size (mm)	0.20 × 0.20 × 0.12

Data collection
Diffractometer	Bruker VENTURE PHOTON-II
Absorption correction	Multi-scan (SADABS; Sheldrick, 1996 )
T_min, T_max	0.057, 0.156
No. of measured, independent and observed [I > 2σ(I)] reflections	7071, 1334, 1239
R_int	0.037
(sin θ/λ)_max (Å⁻¹)	0.715

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.021, 0.050, 1.08
No. of reflections	1334
No. of parameters	58
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.51, −0.90
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: 1812522

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2414314617018193/sj4150sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2414314617018193/sj4150Isup2.hkl

Supporting information file. DOI: https://doi.org/10.1107/S2414314617018193/sj4150Isup3.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-chlorophenyl isocyanide top

Crystal data top

C₇H₂Br₂ClN	D_x = 2.368 Mg m⁻³
M_r = 295.37	Melting point: 377 K
Monoclinic, P2₁/m	Mo Kα radiation, λ = 0.71073 Å
a = 4.7215 (4) Å	Cell parameters from 2922 reflections
b = 10.0181 (9) Å	θ = 2.3–30.5°
c = 8.7689 (8) Å	µ = 10.03 mm⁻¹
β = 93.023 (4)°	T = 100 K
V = 414.20 (6) Å³	Needle, colourless
Z = 2	0.20 × 0.20 × 0.12 mm
F(000) = 276

Data collection top

Bruker VENTURE PHOTON-II diffractometer	1239 reflections with I > 2σ(I)
Radiation source: micro-focus	R_int = 0.037
φ and ω scans	θ_max = 30.5°, θ_min = 2.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −6→5
T_min = 0.057, T_max = 0.156	k = −14→14
7071 measured reflections	l = −12→12
1334 independent reflections

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.021	H-atom parameters constrained
wR(F²) = 0.050	w = 1/[σ²(F_o²) + (0.0194P)² + 0.2636P] where P = (F_o² + 2F_c²)/3
S = 1.08	(Δ/σ)_max = 0.001
1334 reflections	Δρ_max = 0.51 e Å⁻³
58 parameters	Δρ_min = −0.90 e Å⁻³

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
Br11	0.34536 (4)	0.46686 (2)	0.69204 (2)	0.01601 (7)
Cl11	1.09879 (12)	0.7500	1.06960 (7)	0.01600 (12)
C11	0.3949 (5)	0.7500	0.7040 (3)	0.0141 (4)
N11	0.1793 (5)	0.7500	0.5901 (2)	0.0153 (4)
C12	0.5017 (3)	0.62936 (17)	0.76251 (19)	0.0136 (3)
C13	0.7193 (3)	0.62865 (17)	0.87580 (19)	0.0140 (3)
H13A	0.7934	0.5469	0.9156	0.017*
C14	0.8258 (5)	0.7500	0.9296 (3)	0.0140 (4)
C15	0.0001 (6)	0.7500	0.4941 (3)	0.0195 (5)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br11	0.02047 (10)	0.01162 (10)	0.01577 (10)	−0.00213 (6)	−0.00046 (7)	−0.00098 (6)
Cl11	0.0151 (3)	0.0176 (3)	0.0150 (3)	0.000	−0.0022 (2)	0.000
C11	0.0153 (10)	0.0157 (11)	0.0113 (10)	0.000	0.0019 (8)	0.000
N11	0.0185 (10)	0.0140 (9)	0.0134 (9)	0.000	0.0000 (8)	0.000
C12	0.0156 (7)	0.0125 (7)	0.0130 (7)	−0.0016 (6)	0.0030 (6)	−0.0017 (6)
C13	0.0155 (7)	0.0127 (7)	0.0139 (8)	0.0011 (6)	0.0014 (6)	0.0003 (6)
C14	0.0136 (10)	0.0149 (11)	0.0136 (10)	0.000	0.0016 (8)	0.000
C15	0.0253 (13)	0.0139 (10)	0.0189 (12)	0.000	−0.0036 (10)	0.000

Geometric parameters (Å, º) top

Br11—C12	1.8785 (17)	N11—C15	1.161 (4)
Cl11—C14	1.733 (3)	C12—C13	1.391 (3)
C11—N11	1.388 (3)	C13—C14	1.389 (2)
C11—C12ⁱ	1.397 (2)	C13—H13A	0.9500
C11—C12	1.397 (2)	C14—C13ⁱ	1.389 (2)

N11—C11—C12ⁱ	120.09 (11)	C14—C13—C12	118.60 (17)
N11—C11—C12	120.09 (11)	C14—C13—H13A	120.7
C12ⁱ—C11—C12	119.8 (2)	C12—C13—H13A	120.7
C15—N11—C11	179.6 (3)	C13ⁱ—C14—C13	122.2 (2)
C13—C12—C11	120.38 (17)	C13ⁱ—C14—Cl11	118.90 (11)
C13—C12—Br11	119.55 (13)	C13—C14—Cl11	118.90 (11)
C11—C12—Br11	120.06 (14)

N11—C11—C12—C13	179.51 (19)	C11—C12—C13—C14	0.4 (3)
C12ⁱ—C11—C12—C13	−1.8 (3)	Br11—C12—C13—C14	−178.03 (15)
N11—C11—C12—Br11	−2.1 (3)	C12—C13—C14—C13ⁱ	1.1 (3)
C12ⁱ—C11—C12—Br11	176.61 (11)	C12—C13—C14—Cl11	−179.48 (14)

Symmetry code: (i) x, −y+3/2, z.

Contact geometry (Å, °). top

N≡C···Br	N≡C	C···Br	N≡C···Br
N11≡C15···Br11ⁱ	1.161 (4)	3.125 (2)	135.95 (3)

Symmetry code: (i) -x, 1 - 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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