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The title mol­ecule, C12H8Cl2N2O, lacks a centre of symmetry. However, as a result of the positional disorder of the O atom, mol­ecules of the title compound lie across a crystallographic inversion centre in the centrosymmetric space group P21/n. The trans orientation of the aromatic rings around the N=N bond is confirmed.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536803012200/ci6229sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536803012200/ci6229Isup2.hkl
Contains datablock I

CCDC reference: 217453

Key indicators

  • Single-crystal X-ray study
  • T = 293 K
  • Mean [sigma](C-C) = 0.005 Å
  • R factor = 0.048
  • wR factor = 0.140
  • Data-to-parameter ratio = 12.5

checkCIF results

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ADDSYM reports no extra symmetry








Comment top

Diazine oxide derivatives, commonly known as azoxybenzenes, are useful in the preparation of liquid crystals (Tsuji et al., 2000). They are also used as ligands in coordination chemistry (Bassi & Scordamaglia, 1975). They are photochemically active (Rhee & Jaffe, 1973), like the related azo (Tamai & Miyasika, 2000) and nitrone derivatives (Hamer & Macaluso, 1964). Preparation of non-centrosymmetric azoxybenzene derivatives will be of interest to study their non-linear optical properties (Long, 1995) because of electron delocalization within the molecule. The structures of para-substituted azoxybenzenes are known, and most of them assume trans configurations of the benzene ring around the N=N bond in the solid state (Ejsmont et al., 2000). During our investigations of the use of tin(II) chloride for the reductive coupling of nitro compounds with aldehydes and ketones, the title compound, (I), was isolated. The structure determination was undertaken to assign its configuration and the space-group symmetry.

Molecules of the title compound lie across crystallographic inversion centres and the asymmetric unit therefore contains one-half of the molecule. Although the molecule lacks a centre of symmetry, it lies across the inversion centre in the centrosymmetric space group P21/n, due to the positional disorder of O atom. Further, the molecule adopts a thermodynamically stable configuration in which the two cholorophenyl groups are oriented trans to the N=N bond.

The C—C bond lengths in the phenyl ring vary from 1.368 (6) to 1.384 (5) Å. The N=N [1.267 (5) Å] bond distance is comparable to the corressponding bond distance of 1.27 Å observed in trans azoxybenzene through electron diffraction studies. The computed values for the above bond in the same molecule is 1.232 Å at the RHF/6–31G** level of calculation (Tsuji et al., 2000). The N=N bond distance in 5,5'-dichloro-2-hydroxy-2'-(phenylsulfonyl)azoxybenzene is 1.31 (1) Å (Cameron et al., 1976), which is different from that in the title compound. As a consequence of disorder in the title molecule, the N—O and C—N distances are elongated compared to the corresponding distances of 1.27 (1) Å and 1.43 (1) Å in p-azoxyanisole (Krigbaum et al., 1970).

In the crystal structure, the inversion-related molecules are linked by C6—H6···O1(2 − x, 2 − y, 1 − z) hydrogen bonds (Table 2) involving the disordered O atom, to form molecular chains along [1 1 0].

Experimental top

The compound was formed by the reduction of 1-chloro-3-nitrobenzene (2.0 g) by tin(II) chloride (2.5 g) in tetrahydrofuran. The product was isolated by the addition of dilute hydrochloric acid followed by extraction with diethyl ether. Yield was 45.5%. Diffraction quality crystals were obtained by recrystallization of the crude product in hexane.

Refinement top

The O atom is disordered over two centrosymmetric positions, O1 and O1i [symmetry code: (i) 1 − x, 1 − y, 1 − z]. H atoms were placed in geometrical positions and refined using a riding model, with U(H) = 1.2Ueq(C).

Computing details top

Data collection: CAD-4 Software (Enraf-Nonius, 1989); cell refinement: CAD-4 Software; data reduction: MolEN (Fair, 1990); program(s) used to solve structure: SIR92 (Atomare et al., 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2003); software used to prepare material for publication: SHELXL97 and PARST (Nardelli, 1983).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound, showing 30% probability displacement ellipsoids for non-hydrogen atoms. The O atom is disordered over two inversion related positions, O1 and O1i [symmetry code: (i) 1 − x, 1 − y, 1 − z.
[Figure 2] Fig. 2. Packing of the molecules, viewed down the a axis, showing the chain formation.
trans-Bis(3-chlorophenyl)diazine oxide top
Crystal data top
C12H8Cl2N2OF(000) = 272
Mr = 267.10Dx = 1.521 Mg m3
Monoclinic, P21/nMelting point: 367-368 K K
Hall symbol: -P 2ynMo Kα radiation, λ = 0.71069 Å
a = 3.911 (5) ÅCell parameters from 1179 reflections
b = 5.893 (5) Åθ = 3.2–24.6°
c = 25.367 (5) ŵ = 0.54 mm1
β = 94.155 (5)°T = 293 K
V = 583.1 (9) Å3Needle, pale yellow
Z = 20.3 × 0.2 × 0.2 mm
Data collection top
Enraf-Nonius CAD-4
diffractometer
807 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.015
Graphite monochromatorθmax = 25.0°, θmin = 3.2°
ω–2θ scansh = 04
Absorption correction: ψ scan
(North et al., 1968)
k = 07
Tmin = 0.813, Tmax = 0.898l = 3030
1179 measured reflections3 standard reflections every 100 reflections
1021 independent reflections intensity decay: neglible
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)] = 0.048Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.140H-atom parameters constrained
S = 1.11 w = 1/[σ2(Fo2) + (0.0644P)2 + 0.337P]
where P = (Fo2 + 2Fc2)/3
1021 reflections(Δ/σ)max < 0.001
82 parametersΔρmax = 0.21 e Å3
0 restraintsΔρmin = 0.23 e Å3
Crystal data top
C12H8Cl2N2OV = 583.1 (9) Å3
Mr = 267.10Z = 2
Monoclinic, P21/nMo Kα radiation
a = 3.911 (5) ŵ = 0.54 mm1
b = 5.893 (5) ÅT = 293 K
c = 25.367 (5) Å0.3 × 0.2 × 0.2 mm
β = 94.155 (5)°
Data collection top
Enraf-Nonius CAD-4
diffractometer
807 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)
Rint = 0.015
Tmin = 0.813, Tmax = 0.8983 standard reflections every 100 reflections
1179 measured reflections intensity decay: neglible
1021 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0480 restraints
wR(F2) = 0.140H-atom parameters constrained
S = 1.11Δρmax = 0.21 e Å3
1021 reflectionsΔρmin = 0.23 e Å3
82 parameters
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. The occupancy of O1 is fixed as 0.5 during refinement which resulted in an R value of 0.0477. Restricting the occupancy factor for oxygen to unity led to a higher R value of 0.077.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Cl10.3752 (2)0.3764 (2)0.29551 (3)0.0852 (4)
O10.7582 (14)0.7545 (8)0.52152 (16)0.0767 (14)0.50
N10.5810 (7)0.5880 (4)0.49375 (9)0.0594 (7)
C10.6025 (7)0.6347 (5)0.43800 (11)0.0525 (7)
C20.4869 (7)0.4899 (5)0.39766 (9)0.0462 (6)
H20.38630.35160.40500.055*
C30.5245 (7)0.5552 (5)0.34645 (10)0.0500 (7)
C40.6758 (8)0.7591 (7)0.33474 (15)0.0689 (10)
H40.70050.80040.29980.083*
C50.7886 (9)0.8994 (6)0.3753 (2)0.0815 (12)
H50.89041.03720.36780.098*
C60.7538 (9)0.8399 (6)0.42696 (16)0.0702 (10)
H60.83100.93660.45430.084*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cl10.0925 (7)0.1179 (9)0.0432 (5)0.0156 (6)0.0083 (4)0.0249 (5)
O10.116 (4)0.069 (3)0.045 (2)0.043 (3)0.003 (2)0.008 (2)
N10.0684 (17)0.0669 (17)0.0417 (13)0.0107 (13)0.0051 (11)0.0121 (13)
C10.0526 (16)0.0594 (18)0.0445 (15)0.0138 (15)0.0033 (12)0.0097 (13)
C20.0518 (15)0.0471 (15)0.0400 (14)0.0014 (13)0.0048 (11)0.0004 (12)
C30.0478 (15)0.0627 (18)0.0394 (14)0.0098 (13)0.0018 (11)0.0011 (13)
C40.0593 (18)0.077 (2)0.072 (2)0.0133 (17)0.0186 (16)0.0311 (19)
C50.066 (2)0.052 (2)0.126 (4)0.0037 (17)0.009 (2)0.021 (2)
C60.0617 (19)0.055 (2)0.091 (3)0.0027 (16)0.0122 (18)0.0190 (18)
Geometric parameters (Å, º) top
Cl1—C31.735 (3)C2—H20.93
O1—N11.367 (5)C3—C41.381 (5)
N1—N1i1.267 (5)C4—C51.368 (6)
N1—C11.449 (4)C4—H40.93
C1—C21.383 (4)C5—C61.372 (6)
C1—C61.384 (5)C5—H50.93
C2—C31.373 (4)C6—H60.93
N1i—N1—O1134.6 (3)C4—C3—Cl1119.6 (2)
N1i—N1—C1117.7 (3)C5—C4—C3118.9 (3)
O1—N1—C1107.7 (3)C5—C4—H4120.5
C2—C1—C6120.7 (3)C3—C4—H4120.5
C2—C1—N1124.5 (3)C4—C5—C6121.0 (3)
C6—C1—N1114.8 (3)C4—C5—H5119.5
C3—C2—C1118.4 (3)C6—C5—H5119.5
C3—C2—H2120.8C5—C6—C1119.3 (3)
C1—C2—H2120.8C5—C6—H6120.3
C2—C3—C4121.6 (3)C1—C6—H6120.3
C2—C3—Cl1118.8 (2)
N1i—N1—C1—C26.4 (5)C1—C2—C3—Cl1179.2 (2)
O1—N1—C1—C2172.5 (3)C2—C3—C4—C50.4 (5)
N1i—N1—C1—C6174.1 (3)Cl1—C3—C4—C5179.3 (3)
O1—N1—C1—C67.0 (4)C3—C4—C5—C60.1 (5)
C6—C1—C2—C30.3 (4)C4—C5—C6—C10.1 (5)
N1—C1—C2—C3179.8 (2)C2—C1—C6—C50.0 (5)
C1—C2—C3—C40.5 (4)N1—C1—C6—C5179.5 (3)
Symmetry code: (i) x+1, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H2···O1i0.932.082.735 (6)126
C6—H6···O10.932.052.450 (7)104
C6—H6···O1ii0.932.483.271 (7)144
Symmetry codes: (i) x+1, y+1, z+1; (ii) x+2, y+2, z+1.

Experimental details

Crystal data
Chemical formulaC12H8Cl2N2O
Mr267.10
Crystal system, space groupMonoclinic, P21/n
Temperature (K)293
a, b, c (Å)3.911 (5), 5.893 (5), 25.367 (5)
β (°) 94.155 (5)
V3)583.1 (9)
Z2
Radiation typeMo Kα
µ (mm1)0.54
Crystal size (mm)0.3 × 0.2 × 0.2
Data collection
DiffractometerEnraf-Nonius CAD-4
diffractometer
Absorption correctionψ scan
(North et al., 1968)
Tmin, Tmax0.813, 0.898
No. of measured, independent and
observed [I > 2σ(I)] reflections
1179, 1021, 807
Rint0.015
(sin θ/λ)max1)0.594
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.048, 0.140, 1.11
No. of reflections1021
No. of parameters82
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.21, 0.23

Computer programs: CAD-4 Software (Enraf-Nonius, 1989), CAD-4 Software, MolEN (Fair, 1990), SIR92 (Atomare et al., 1993), SHELXL97 (Sheldrick, 1997), ORTEP-3 for Windows (Farrugia, 1997) and PLATON (Spek, 2003), SHELXL97 and PARST (Nardelli, 1983).

Selected geometric parameters (Å, º) top
Cl1—C31.735 (3)C1—C61.384 (5)
O1—N11.367 (5)C2—C31.373 (4)
N1—N1i1.267 (5)C3—C41.381 (5)
N1—C11.449 (4)C4—C51.368 (6)
C1—C21.383 (4)C5—C61.372 (6)
N1i—N1—O1134.6 (3)C2—C3—C4121.6 (3)
N1i—N1—C1117.7 (3)C2—C3—Cl1118.8 (2)
O1—N1—C1107.7 (3)C4—C3—Cl1119.6 (2)
C2—C1—C6120.7 (3)C5—C4—C3118.9 (3)
C2—C1—N1124.5 (3)C4—C5—C6121.0 (3)
C6—C1—N1114.8 (3)C5—C6—C1119.3 (3)
C3—C2—C1118.4 (3)
N1i—N1—C1—C26.4 (5)N1i—N1—C1—C6174.1 (3)
O1—N1—C1—C2172.5 (3)O1—N1—C1—C67.0 (4)
Symmetry code: (i) x+1, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H2···O1i0.932.082.735 (6)126
C6—H6···O10.932.052.450 (7)104
C6—H6···O1ii0.932.483.271 (7)144
Symmetry codes: (i) x+1, y+1, z+1; (ii) x+2, y+2, z+1.
 

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