organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2056-9890

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

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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.

[Scheme 1]

Fig. 1[link] 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[link]).

[Figure 1]
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]
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

  • Mr = 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

  • Dx = 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[Sheldrick, G. M. (2003). SADABS. Version 2.10. University of Göttingen, Germany.])Tmin = 0.101, Tmax = 0.289

  • 10287 measured reflections

  • 1199 independent reflections

  • 1047 reflections with I > 2σ(I)

  • Rint = 0.039

  • θmax = 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(Fo2) + (0.0366P)2 + 1.2866P] where P = (Fo2 + 2Fc2)/3

  • (Δ/σ)max < 0.001

  • Δρmax = 0.72 e Å−3

  • Δρmin = −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 Uiso(H) values of 1.2Ueq(C) for aromatic and 1.5Ueq(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[Hooft, R. W. W. (1998). COLLECT. Nonius BV, Delft, The Netherlands.]); cell refinement: DENZO (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]) and COLLECT; data reduction: DENZO and COLLECT; program(s) used to solve structure: OSCAIL (McArdle, 2003[McArdle, P. (2003). OSCAIL for Windows. Version 10. Crystallography Centre, Chemistry Department, NUI Galway, Ireland.]) and SHELXS97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); program(s) used to refine structure: OSCAIL and SHELXL97 (Sheldrick, 1997[Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.]); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997[Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.]); software used to prepare material for publication: SHELXL97.

Supporting information


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·C9H9Br2NO2F(000) = 608
Mr = 631.96Dx = 2.149 Mg m3
Orthorhombic, PnmaMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2nCell parameters from 1315 reflections
a = 8.9730 (3) Åθ = 2.9–27.5°
b = 7.1165 (2) ŵ = 8.27 mm1
c = 15.2972 (5) ÅT = 120 K
V = 976.82 (5) Å3Rod, colourless
Z = 20.60 × 0.15 × 0.15 mm
Data collection top
Nonius KappaCCD
diffractometer
1199 independent reflections
Radiation source: Bruker-Nonius FR591 rotating anode1047 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.039
Detector resolution: 9.091 pixels mm-1θmax = 27.5°, θmin = 3.5°
φ and ω scansh = 1111
Absorption correction: multi-scan
(SADABS; Sheldrick, 2003)
k = 98
Tmin = 0.101, Tmax = 0.289l = 1719
10287 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.030Hydrogen site location: difference Fourier map
wR(F2) = 0.073H-atom parameters constrained
S = 1.11 w = 1/[σ2(Fo2) + (0.0366P)2 + 1.2866P]
where P = (Fo2 + 2Fc2)/3
1199 reflections(Δ/σ)max < 0.001
84 parametersΔρmax = 0.72 e Å3
0 restraintsΔρmin = 0.82 e Å3
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
xyzUiso*/UeqOcc. (<1)
C10.6963 (5)0.25000.4618 (3)0.0192 (8)
N10.8300 (4)0.25000.4048 (2)0.0323 (9)
O10.8807 (3)0.0978 (4)0.38353 (17)0.0532 (8)
C20.5567 (5)0.25000.4221 (2)0.0189 (8)
Br20.54155 (5)0.25000.29954 (3)0.03157 (15)
C30.4341 (4)0.25000.4764 (3)0.0213 (8)
Br30.23875 (5)0.25000.42946 (3)0.03008 (15)
C40.4506 (5)0.25000.5661 (3)0.0239 (9)
H40.36440.25000.60210.029*0.50
C410.3033 (12)0.25000.6320 (8)0.043 (2)0.50
H41A0.21190.25000.59690.065*0.50
H41B0.30630.36160.66950.065*0.50
C50.5912 (5)0.25000.6050 (3)0.0226 (8)
C510.6091 (6)0.25000.7037 (3)0.0331 (11)
H51A0.66040.13500.72200.050*
H51B0.51060.25000.73130.050*
C60.7192 (5)0.25000.5512 (3)0.0207 (8)
C610.8780 (5)0.25000.5900 (3)0.0255 (9)
H61A0.88470.15450.63600.038*0.50
H61B0.89980.37390.61480.038*0.50
H61C0.95020.22160.54380.038*0.50
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.014 (2)0.0232 (19)0.0200 (18)0.0000.0002 (15)0.000
N10.0165 (19)0.059 (3)0.0216 (17)0.0000.0007 (15)0.000
O10.0462 (16)0.0744 (19)0.0391 (13)0.0353 (15)0.0170 (12)0.0122 (14)
C20.019 (2)0.0188 (18)0.0186 (18)0.0000.0043 (16)0.000
Br20.0290 (3)0.0456 (3)0.0201 (2)0.0000.00710 (17)0.000
C30.0109 (19)0.0193 (18)0.034 (2)0.0000.0014 (17)0.000
Br30.0140 (2)0.0289 (2)0.0473 (3)0.0000.00640 (19)0.000
C40.022 (2)0.022 (2)0.028 (2)0.0000.0064 (18)0.000
C410.034 (6)0.044 (6)0.051 (6)0.0000.008 (5)0.000
C50.025 (2)0.0222 (19)0.0210 (19)0.0000.0010 (17)0.000
C510.040 (3)0.040 (3)0.019 (2)0.0000.0057 (19)0.000
C60.018 (2)0.0199 (18)0.024 (2)0.0000.0012 (16)0.000
C610.030 (2)0.027 (2)0.0199 (18)0.0000.0119 (17)0.000
Geometric parameters (Å, º) top
C1—C61.383 (5)C4—H40.9500
C1—C21.392 (6)C41—H41A0.9799
C1—N11.483 (6)C41—H41B0.9800
N1—O1i1.219 (3)C5—C61.413 (6)
N1—O11.219 (3)C5—C511.519 (6)
C2—C31.378 (6)C51—H51A0.9800
C2—Br21.880 (4)C51—H51B0.9793
C3—C41.380 (6)C6—C611.543 (6)
C3—Br31.894 (4)C61—H61A0.9800
C4—C51.394 (6)C61—H61B0.9800
C4—C411.662 (11)C61—H61C0.9800
C6—C1—C2124.4 (4)C4—C41—H41A109.5
C6—C1—N1117.5 (4)C4—C41—H41B109.5
C2—C1—N1118.1 (3)H41A—C41—H41B110.0
O1i—N1—O1125.4 (4)C4—C5—C6119.1 (4)
O1i—N1—C1117.3 (2)C4—C5—C51121.3 (4)
O1—N1—C1117.3 (2)C6—C5—C51119.5 (4)
C3—C2—C1117.1 (4)C5—C51—H51A109.5
C3—C2—Br2122.9 (3)C5—C51—H51B109.4
C1—C2—Br2120.0 (3)H51A—C51—H51B107.5
C2—C3—C4120.8 (4)C1—C6—C5117.1 (4)
C2—C3—Br3120.7 (3)C1—C6—C61121.1 (4)
C4—C3—Br3118.5 (3)C5—C6—C61121.8 (4)
C3—C4—C5121.4 (4)C6—C61—H61A109.5
C3—C4—C41121.1 (5)C6—C61—H61B109.5
C5—C4—C41117.4 (5)H61A—C61—H61B109.5
C3—C4—H4119.3C6—C61—H61C109.5
C5—C4—H4119.3H61A—C61—H61C109.5
C41—C4—H41.9H61B—C61—H61C109.5
C6—C1—N1—O1i89.7 (3)C2—C3—C4—C41180.000 (2)
C2—C1—N1—O1i90.3 (3)Br3—C3—C4—C410.000 (2)
C6—C1—N1—O189.7 (3)C3—C4—C5—C60.000 (1)
C2—C1—N1—O190.3 (3)C41—C4—C5—C6180.0
C6—C1—C2—C30.000 (1)C3—C4—C5—C51180.000 (1)
N1—C1—C2—C3180.0C41—C4—C5—C510.000 (2)
C6—C1—C2—Br2180.0C2—C1—C6—C50.000 (1)
N1—C1—C2—Br20.0N1—C1—C6—C5180.0
C1—C2—C3—C40.000 (1)C2—C1—C6—C61180.0
Br2—C2—C3—C4180.0N1—C1—C6—C610.000 (1)
C1—C2—C3—Br3180.0C4—C5—C6—C10.000 (1)
Br2—C2—C3—Br30.0C51—C5—C6—C1180.000 (1)
C2—C3—C4—C50.000 (1)C4—C5—C6—C61180.000 (1)
Br3—C3—C4—C5180.0C51—C5—C6—C610.000 (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[Fletcher, D. A., McMeeking, R. F. & Parkin, D. (1996). J. Chem. Inf. Comput. Sci. 36, 746-749.]), 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.

References

First citationFarrugia, L. J. (1997). J. Appl. Cryst. 30, 565.  CrossRef IUCr Journals Google Scholar
First citationFletcher, D. A., McMeeking, R. F. & Parkin, D. (1996). J. Chem. Inf. Comput. Sci. 36, 746–749.  CrossRef CAS Web of Science Google Scholar
First citationHooft, R. W. W. (1998). COLLECT. Nonius BV, Delft, The Netherlands.  Google Scholar
First citationMcArdle, P. (2003). OSCAIL for Windows. Version 10. Crystallography Centre, Chemistry Department, NUI Galway, Ireland.  Google Scholar
First citationOtwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307–326. New York: Academic Press.  Google Scholar
First citationSheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.  Google Scholar
First citationSheldrick, G. M. (2003). SADABS. Version 2.10. University of Göttingen, Germany.  Google Scholar

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