Cocrystallized 1,2-dibromo-4,5-dimethyl-3-nitro­benzene and 1,2-dibromo-4,5,6-trimethyl-3-nitro­benzene

Skakle, J.M.S.; Gojdka, B.; Wardell, J.L.

doi:10.1107/S1600536806003631

organic compounds

CRYSTALLOGRAPHIC
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ISSN: 2056-9890

Volume 62| Part 3| March 2006| Pages o1001-o1002

https://doi.org/10.1107/S1600536806003631

Cocrystallized 1,2-dibromo-4,5-dimethyl-3-nitrobenzene and 1,2-dibromo-4,5,6-trimethyl-3-nitrobenzene

Janet M. S. Skakle,^a,^b ^* Björn Gojdka ^b,^c and James L. Wardell ^d

^aDepartment of Chemistry, College of Physical Sciences, University of Aberdeen, Meston Walk, Aberdeen AB24 3UE, Scotland, ^bDepartment of Physics, University of Aberdeen, Fraser Noble Building, Aberdeen AB24 3UE, Scotland, ^cChristian Albrechts Universität, Sektion Physik, Leibnitzstrasse 19, 24098 Kiel, Germany, and ^dDepartamento de Química Inorgânica, Instituto de Química, Universidade Federal do Rio de Janeiro, 21945-970 Rio de Janeiro, RJ, Brazil
^*Correspondence e-mail: j.skakle@abdn.ac.uk

(Received 11 January 2006; accepted 30 January 2006; online 10 February 2006)

In the crystal structure of the title compound, C₈H₇Br₂NO₂·C₉H₉Br₂NO₂, the 1,2-dibromo-4,5-dimethyl-3-nitrobenzene and 1,2-dibromo-4,5,6-trimethyl-3-nitrobenzene molecules occupy the same crystallographic position, such that the aromatic H atom of the former compound is superimposed on the methyl group of the latter. The structure is thus best modelled by a 50:50 disorder of the two compounds. All non-H atoms are located on a mirror plane except the O atoms of the nitro group.

Comment

1,2-Dibromo-4,5-dimethyl-3-nitrobenzene was required as a reagent for the synthesis of 1,2-bis(mercapto)-4,5-dimethyl-3-nitrobenzene, which can be used as a 1,2-dithiolate ligand. However, melting point measurements revealed that this compound melts over a wide temperature range and NMR spectra were more complex than expected. Therefore, a single-crystal structure determination was performed, which shows that the sample is a cocrystallized mixture of the expected material and 1,2-dibromo-4,5,6-trimethyl-3-nitrobenzene.

Fig. 1 shows the superimposed molecules within the crystal structure, the only difference lying in the replacement of the H atom at C4 by a methyl group. All non-H atoms are located on a crystallographic mirror plane, except the O atoms of the nitro group, which occupy general positions. The H atoms of one of the three crystallographically independent methyl groups are disordered over two orientations.

In the crystal structure, the molecules are stacked in the direction of the crystallographic b axis, but shifted in such a way that one C atom of the six-membered ring is located above and below the centroids of the six-membered rings of the neighbouring molecules (Fig. 2).

Figure 1
The molecular structure of the title compound, showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are shown as circles of arbitrary radii. [Symmetry code: (i) x, $[{1\over 2}]$ − y, z.] Disorder of the C6 methyl group is indicated.

Figure 2
Part of the crystal structure of the title compound, showing the packing of molecules along [010]. Displacement ellipsoids are shown at the 30% level and H atoms have been omitted for clarity. Only one component is shown for each disordered group.

Experimental

A donated sample of 1,2-dibromo-4,5-dimethyl-3-nitrobenzene was recrystallized from ethanol (m.p. 381–390 K). ¹H NMR (300 MHz, CDCl₃, δ, p.p.m.): 1,2-dibromo-4,5-dimethyl-3-nitrobenzene: 2.26 (s, 3H), 2.29 (s, 3H) (both Me), 7.54 (s, 1H, aryl-H); 1,2-dibromo-4,5,6-trimethyl-3-nitrobenzene: 2.25 (s, 3H), 2.29 (s, 3H), 2.53 (s, 3H). ¹³C NMR (75 MHz, CDCl₃): δ 14.7, 16.7, 19.8, 22.7, 112.5, 114.1, 122.9, 128.7, 131.5, 135.1, 139.5,151.1 and 153.8. IR (cm⁻¹, KBr): 3094, 3026–2701, 1765, 1537, 1544, 1370, 1340, 1265, 1065, 895, 841, 738, 651, 532, 466.

Crystal data

C₈H₇Br₂NO₂·C₉H₉Br₂NO₂
M_r = 631.96
Orthorhombic, P n m a
a = 8.9730 (3) Å
b = 7.1165 (2) Å
c = 15.2972 (5) Å
V = 976.82 (5) Å³
Z = 2
D_x = 2.149 Mg m⁻³
Mo Kα radiation
Cell parameters from 1315 reflections
θ = 2.9–27.5°
μ = 8.27 mm⁻¹
T = 120 (2) K
Rod, colourless
0.60 × 0.15 × 0.15 mm

Data collection

Nonius KappaCCD diffractometer
φ and ω scans
Absorption correction: multi-scan(SADABS; Sheldrick, 2003 )T_min = 0.101, T_max = 0.289
10287 measured reflections
1199 independent reflections
1047 reflections with I > 2σ(I)
R_int = 0.039
θ_max = 27.5°
h = −11 → 11
k = −9 → 8
l = −17 → 19

Refinement

Refinement on F²
R[F² > 2σ(F²)] = 0.030
wR(F²) = 0.073
S = 1.11
1199 reflections
84 parameters
H-atom parameters constrained
w = 1/[σ²(F_o²) + (0.0366P)² + 1.2866P] where P = (F_o² + 2F_c²)/3
(Δ/σ)_max < 0.001
Δρ_max = 0.72 e Å⁻³
Δρ_min = −0.82 e Å⁻³

The space groups Pnma and Pna2₁ were permitted by the systematic absences; Pnma was selected and confirmed by the structure analysis. To check that the disorder was not an artefact of the selected space group, the structure was also solved in Pna2₁ and in the triclinic spacegroup P $[\overline{1}]$ . In both space groups the disorder was also evident. In addition, no superstructure reflections were found. All H atoms were located in difference maps and then treated as riding atoms, with C—H distances of 0.95 Å (aromatic) or 0.98 Å (methyl), and U_iso(H) values of 1.2U_eq(C) for aromatic and 1.5U_eq(C) for methyl H atoms. The occupancy of the disordered methyl (C41) group was initially refined freely, and converged to a low value (0.27) but with non-positive displacement parameters for this atom, so the occupancy was gradually increased to give displacement parameters similar to those of the other methyl groups, Finally, they were fixed at $[{1 \over 2}]$ , representing a 50:50 mixture of the cocrystallized molecules. The H atoms of one of the three methyl groups are disordered over two orientations with equal occupancies.

Data collection: COLLECT (Hooft, 1998 ); cell refinement: DENZO (Otwinowski & Minor, 1997 ) and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: OSCAIL (McArdle, 2003 ) and SHELXS97 (Sheldrick, 1997 ); program(s) used to refine structure: OSCAIL and SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536806003631/nc6061sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536806003631/nc6061Isup2.hkl

Computing details top

Data collection: COLLECT (Hooft, 1998); cell refinement: DENZO (Otwinowski & Minor, 1997) and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: OSCAIL (McArdle, 2003) and SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: OSCAIL and SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97.

1,2-dibromo-4,5-dimethyl-3-nitrobenzene– 1,2-dibromo-4,5,6-trimethyl-3-nitrobenzene (1/1) top

Crystal data top

C₈H₇Br₂NO₂·C₉H₉Br₂NO₂	F(000) = 608
M_r = 631.96	D_x = 2.149 Mg m⁻³
Orthorhombic, Pnma	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2n	Cell parameters from 1315 reflections
a = 8.9730 (3) Å	θ = 2.9–27.5°
b = 7.1165 (2) Å	µ = 8.27 mm⁻¹
c = 15.2972 (5) Å	T = 120 K
V = 976.82 (5) Å³	Rod, colourless
Z = 2	0.60 × 0.15 × 0.15 mm

Data collection top

Nonius KappaCCD diffractometer	1199 independent reflections
Radiation source: Bruker-Nonius FR591 rotating anode	1047 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.039
Detector resolution: 9.091 pixels mm^-1	θ_max = 27.5°, θ_min = 3.5°
φ and ω scans	h = −11→11
Absorption correction: multi-scan (SADABS; Sheldrick, 2003)	k = −9→8
T_min = 0.101, T_max = 0.289	l = −17→19
10287 measured reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.030	Hydrogen site location: difference Fourier map
wR(F²) = 0.073	H-atom parameters constrained
S = 1.11	w = 1/[σ²(F_o²) + (0.0366P)² + 1.2866P] where P = (F_o² + 2F_c²)/3
1199 reflections	(Δ/σ)_max < 0.001
84 parameters	Δρ_max = 0.72 e Å⁻³
0 restraints	Δρ_min = −0.82 e Å⁻³

Special details top

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

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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

	x	y	z	U_iso*/U_eq	Occ. (<1)
C1	0.6963 (5)	0.2500	0.4618 (3)	0.0192 (8)
N1	0.8300 (4)	0.2500	0.4048 (2)	0.0323 (9)
O1	0.8807 (3)	0.0978 (4)	0.38353 (17)	0.0532 (8)
C2	0.5567 (5)	0.2500	0.4221 (2)	0.0189 (8)
Br2	0.54155 (5)	0.2500	0.29954 (3)	0.03157 (15)
C3	0.4341 (4)	0.2500	0.4764 (3)	0.0213 (8)
Br3	0.23875 (5)	0.2500	0.42946 (3)	0.03008 (15)
C4	0.4506 (5)	0.2500	0.5661 (3)	0.0239 (9)
H4	0.3644	0.2500	0.6021	0.029*	0.50
C41	0.3033 (12)	0.2500	0.6320 (8)	0.043 (2)	0.50
H41A	0.2119	0.2500	0.5969	0.065*	0.50
H41B	0.3063	0.3616	0.6695	0.065*	0.50
C5	0.5912 (5)	0.2500	0.6050 (3)	0.0226 (8)
C51	0.6091 (6)	0.2500	0.7037 (3)	0.0331 (11)
H51A	0.6604	0.1350	0.7220	0.050*
H51B	0.5106	0.2500	0.7313	0.050*
C6	0.7192 (5)	0.2500	0.5512 (3)	0.0207 (8)
C61	0.8780 (5)	0.2500	0.5900 (3)	0.0255 (9)
H61A	0.8847	0.1545	0.6360	0.038*	0.50
H61B	0.8998	0.3739	0.6148	0.038*	0.50
H61C	0.9502	0.2216	0.5438	0.038*	0.50

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
C1	0.014 (2)	0.0232 (19)	0.0200 (18)	0.000	0.0002 (15)	0.000
N1	0.0165 (19)	0.059 (3)	0.0216 (17)	0.000	−0.0007 (15)	0.000
O1	0.0462 (16)	0.0744 (19)	0.0391 (13)	0.0353 (15)	0.0170 (12)	0.0122 (14)
C2	0.019 (2)	0.0188 (18)	0.0186 (18)	0.000	−0.0043 (16)	0.000
Br2	0.0290 (3)	0.0456 (3)	0.0201 (2)	0.000	−0.00710 (17)	0.000
C3	0.0109 (19)	0.0193 (18)	0.034 (2)	0.000	−0.0014 (17)	0.000
Br3	0.0140 (2)	0.0289 (2)	0.0473 (3)	0.000	−0.00640 (19)	0.000
C4	0.022 (2)	0.022 (2)	0.028 (2)	0.000	0.0064 (18)	0.000
C41	0.034 (6)	0.044 (6)	0.051 (6)	0.000	0.008 (5)	0.000
C5	0.025 (2)	0.0222 (19)	0.0210 (19)	0.000	0.0010 (17)	0.000
C51	0.040 (3)	0.040 (3)	0.019 (2)	0.000	0.0057 (19)	0.000
C6	0.018 (2)	0.0199 (18)	0.024 (2)	0.000	−0.0012 (16)	0.000
C61	0.030 (2)	0.027 (2)	0.0199 (18)	0.000	−0.0119 (17)	0.000

Geometric parameters (Å, º) top

C1—C6	1.383 (5)	C4—H4	0.9500
C1—C2	1.392 (6)	C41—H41A	0.9799
C1—N1	1.483 (6)	C41—H41B	0.9800
N1—O1ⁱ	1.219 (3)	C5—C6	1.413 (6)
N1—O1	1.219 (3)	C5—C51	1.519 (6)
C2—C3	1.378 (6)	C51—H51A	0.9800
C2—Br2	1.880 (4)	C51—H51B	0.9793
C3—C4	1.380 (6)	C6—C61	1.543 (6)
C3—Br3	1.894 (4)	C61—H61A	0.9800
C4—C5	1.394 (6)	C61—H61B	0.9800
C4—C41	1.662 (11)	C61—H61C	0.9800

C6—C1—C2	124.4 (4)	C4—C41—H41A	109.5
C6—C1—N1	117.5 (4)	C4—C41—H41B	109.5
C2—C1—N1	118.1 (3)	H41A—C41—H41B	110.0
O1ⁱ—N1—O1	125.4 (4)	C4—C5—C6	119.1 (4)
O1ⁱ—N1—C1	117.3 (2)	C4—C5—C51	121.3 (4)
O1—N1—C1	117.3 (2)	C6—C5—C51	119.5 (4)
C3—C2—C1	117.1 (4)	C5—C51—H51A	109.5
C3—C2—Br2	122.9 (3)	C5—C51—H51B	109.4
C1—C2—Br2	120.0 (3)	H51A—C51—H51B	107.5
C2—C3—C4	120.8 (4)	C1—C6—C5	117.1 (4)
C2—C3—Br3	120.7 (3)	C1—C6—C61	121.1 (4)
C4—C3—Br3	118.5 (3)	C5—C6—C61	121.8 (4)
C3—C4—C5	121.4 (4)	C6—C61—H61A	109.5
C3—C4—C41	121.1 (5)	C6—C61—H61B	109.5
C5—C4—C41	117.4 (5)	H61A—C61—H61B	109.5
C3—C4—H4	119.3	C6—C61—H61C	109.5
C5—C4—H4	119.3	H61A—C61—H61C	109.5
C41—C4—H4	1.9	H61B—C61—H61C	109.5

C6—C1—N1—O1ⁱ	−89.7 (3)	C2—C3—C4—C41	180.000 (2)
C2—C1—N1—O1ⁱ	90.3 (3)	Br3—C3—C4—C41	0.000 (2)
C6—C1—N1—O1	89.7 (3)	C3—C4—C5—C6	0.000 (1)
C2—C1—N1—O1	−90.3 (3)	C41—C4—C5—C6	180.0
C6—C1—C2—C3	0.000 (1)	C3—C4—C5—C51	180.000 (1)
N1—C1—C2—C3	180.0	C41—C4—C5—C51	0.000 (2)
C6—C1—C2—Br2	180.0	C2—C1—C6—C5	0.000 (1)
N1—C1—C2—Br2	0.0	N1—C1—C6—C5	180.0
C1—C2—C3—C4	0.000 (1)	C2—C1—C6—C61	180.0
Br2—C2—C3—C4	180.0	N1—C1—C6—C61	0.000 (1)
C1—C2—C3—Br3	180.0	C4—C5—C6—C1	0.000 (1)
Br2—C2—C3—Br3	0.0	C51—C5—C6—C1	180.000 (1)
C2—C3—C4—C5	0.000 (1)	C4—C5—C6—C61	180.000 (1)
Br3—C3—C4—C5	180.0	C51—C5—C6—C61	0.000 (1)

Symmetry code: (i) x, −y+1/2, z.

Acknowledgements

We are indebted to the EPSRC for the use of both the Chemical Database Service at Daresbury (Fletcher et al., 1996 ), primarily for access to the Cambridge Structural Database, and the X-ray service at the University of Southampton for data collection. We thank CNPq, Brazil, for financial support.

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