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Acta Crystallogr Sect E Struct Rep Online. 2009 June 1; 65(Pt 6): o1275.
Published online 2009 May 14. doi:  10.1107/S1600536809017036
PMCID: PMC2969705

Low-temperature redetermination of benzofurazan 1-oxide

Abstract

In the six-membered ring of the low-temperature crystal structure of benzofurazan 1-oxide, C6H4N2O2, the two C atoms adjacent to the N atoms are linked by a delocalized aromatic bond [1.402 (2) Å]; each is connected to its neighbour by a longer, more localized, bond [1.420 (2), 1.430 (2) Å]. However, the next two bonds in the ring approximate double bonds [1.357 (2), 1.366 (2) Å]. As such, the six-membered ring is better described as a cyclo­hexa­diene system, in contrast to the description in the room-temperature structure reported by Britton & Olson (1979 [triangle]) [Acta Cryst. B35, 3076–3078].

Related literature

For the room-temperature structure in the P An external file that holds a picture, illustration, etc.
Object name is e-65-o1275-efi1.jpg setting [6.772 (3), 7.515 (4), 7.759 (4) Å, 99.08 (3), 114.94 (3), 112.67 (3) °], see: Britton & Olson (1979 [triangle]). For the geometry-optimized structure, see: Friedrichsen, 1995 [triangle]; Ponder et al. (1994 [triangle]); Rauhut (1996 [triangle]). For details of the synthesis, see: Terrian et al. (1992 [triangle]); Wolthius (1979 [triangle]). For work mentioning the original structure, see: Ammon & Bhattacharjee (1982 [triangle]); Bird (1993 [triangle]); Cerecetto & González (2007 [triangle]); Ojala et al. (1999 [triangle]); Ramm et al. (1991 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-65-o1275-scheme1.jpg

Experimental

Crystal data

  • C6H4N2O2
  • M r = 136.11
  • Triclinic, An external file that holds a picture, illustration, etc.
Object name is e-65-o1275-efi2.jpg
  • a = 6.6751 (2) Å
  • b = 7.3256 (2) Å
  • c = 7.6842 (2) Å
  • α = 100.710 (2)°
  • β = 114.265 (2)°
  • γ = 111.747 (2)°
  • V = 291.71 (1) Å3
  • Z = 2
  • Mo Kα radiation
  • μ = 0.12 mm−1
  • T = 100 K
  • 0.30 × 0.25 × 0.10 mm

Data collection

  • Bruker SMART APEX diffractometer
  • Absorption correction: none
  • 1952 measured reflections
  • 1276 independent reflections
  • 1110 reflections with I > 2σ(I)
  • R int = 0.012

Refinement

  • R[F 2 > 2σ(F 2)] = 0.035
  • wR(F 2) = 0.110
  • S = 1.03
  • 1276 reflections
  • 108 parameters
  • 4 restraints
  • All H-atom parameters refined
  • Δρmax = 0.33 e Å−3
  • Δρmin = −0.21 e Å−3

Data collection: APEX2 (Bruker, 2008 [triangle]); cell refinement: SAINT (Bruker, 2008 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: X-SEED (Barbour, 2001 [triangle]); software used to prepare material for publication: publCIF (Westrip, 2009 [triangle]).

Table 1
Selected bond lengths (Å)

Supplementary Material

Crystal structure: contains datablocks I, New_Global_Publ_Block. DOI: 10.1107/S1600536809017036/tk2443sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809017036/tk2443Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

I thank the University of Malaya for supporting this study.

supplementary crystallographic information

Comment

Researchers have used the published structure of benzofurazan 1-oxide (Britton & Olson, 1979) in, for example, studies on packing (Ammon & Bhattacharjee, 1982; Ojala et al., 1999; Ramm et al., 1991), influence of N-oxide formation on heteroaromaticity (Bird, 1993), and reactivity and biology (Cerecetto & González, 2007). Bond dimensions from geometry-optimization calculations (Friedrichsen, 1995; Ponder et al.,1994; Rauhut, 1996) have also been compared with values taken from the solid-state structure.

The present low-temperature structure (Fig. 1 & Table 1) reveals features quite distinct from those disclosed in the original, room-temperature, analysis (Britton & Olson, 1979). In the six-membered ring, the two carbon atoms adjacent to the nitrogen atoms are linked by a delocalized aromatic bond [1.402 (2) Å]; each is connected to its neighbor by a longer, more localized, bond [1.420 (2), 1.430 (2) Å]. However, the next two bonds in the ring approximate double-bonds [1.357 (2), 1.366 (2) Å]. As such, the six-membered ring is better described as a cyclohexadiene system.

Experimental

The compound was synthesized according to a reported procedure (Terrian et al., 1992; Wolthius, 1979). Crystals were grown with THF as solvent.

Refinement

The carbon-bound H-atoms were restrained to C—H 0.95±0.01 Å; their temperature factors were freely refined.

Figures

Fig. 1.
The molecular structure of the title compound. Displacement ellipsoids are drawn at the 70% probability level, and hydrogen atoms are drawn as spheres of arbitrary radius.

Crystal data

C6H4N2O2Z = 2
Mr = 136.11F(000) = 140
Triclinic, P1Dx = 1.550 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 6.6751 (2) ÅCell parameters from 1320 reflections
b = 7.3256 (2) Åθ = 3.2–28.3°
c = 7.6842 (2) ŵ = 0.12 mm1
α = 100.710 (2)°T = 100 K
β = 114.265 (2)°Irregular block, yellow-orange
γ = 111.747 (2)°0.30 × 0.25 × 0.10 mm
V = 291.71 (1) Å3

Data collection

Bruker SMART APEX diffractometer1110 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.012
graphiteθmax = 27.5°, θmin = 3.2°
ω scansh = −7→8
1952 measured reflectionsk = −9→9
1276 independent reflectionsl = −9→9

Refinement

Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.035All H-atom parameters refined
wR(F2) = 0.110w = 1/[σ2(Fo2) + (0.0685P)2 + 0.0855P] where P = (Fo2 + 2Fc2)/3
S = 1.03(Δ/σ)max = 0.001
1276 reflectionsΔρmax = 0.33 e Å3
108 parametersΔρmin = −0.21 e Å3
4 restraintsExtinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.03 (1)

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

xyzUiso*/Ueq
O10.1183 (2)0.2141 (2)−0.0082 (1)0.0274 (3)
O20.5178 (2)0.2611 (2)0.1146 (1)0.0271 (3)
N10.3061 (2)0.2329 (2)0.1385 (2)0.0211 (3)
N20.7112 (2)0.2839 (2)0.2955 (2)0.0257 (3)
C10.6232 (2)0.2701 (2)0.4219 (2)0.0188 (3)
C20.7496 (3)0.2863 (2)0.6308 (2)0.0202 (3)
C30.6182 (3)0.2669 (2)0.7284 (2)0.0207 (3)
C40.3643 (3)0.2321 (2)0.6312 (2)0.0209 (3)
C50.2382 (3)0.2174 (2)0.4325 (2)0.0199 (3)
C60.3750 (2)0.2377 (2)0.3296 (2)0.0181 (3)
H20.919 (2)0.310 (3)0.693 (3)0.030 (4)*
H30.701 (3)0.278 (3)0.867 (2)0.037 (5)*
H40.281 (3)0.221 (3)0.706 (2)0.027 (4)*
H50.072 (2)0.197 (3)0.369 (2)0.031 (4)*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
O10.0242 (5)0.0333 (6)0.0172 (5)0.0139 (4)0.0039 (4)0.0130 (4)
O20.0270 (6)0.0398 (6)0.0190 (5)0.0172 (5)0.0137 (4)0.0157 (4)
N10.0213 (6)0.0237 (6)0.0158 (5)0.0105 (5)0.0077 (5)0.0098 (4)
N20.0237 (6)0.0361 (7)0.0202 (6)0.0155 (5)0.0120 (5)0.0144 (5)
C10.0198 (6)0.0199 (6)0.0171 (6)0.0096 (5)0.0095 (5)0.0090 (5)
C20.0187 (6)0.0231 (6)0.0175 (6)0.0109 (5)0.0072 (5)0.0103 (5)
C30.0240 (7)0.0215 (6)0.0147 (6)0.0109 (5)0.0083 (5)0.0093 (5)
C40.0246 (7)0.0228 (6)0.0192 (6)0.0120 (5)0.0137 (6)0.0102 (5)
C50.0188 (6)0.0213 (6)0.0200 (6)0.0104 (5)0.0096 (5)0.0096 (5)
C60.0200 (6)0.0175 (6)0.0136 (5)0.0086 (5)0.0066 (5)0.0073 (4)

Geometric parameters (Å, °)

O1—N11.230 (1)C3—C41.436 (2)
O2—N21.381 (1)C4—C51.366 (2)
O2—N11.443 (2)C5—C61.420 (2)
N1—C61.336 (2)C2—H20.956 (9)
N2—C11.327 (2)C3—H30.948 (9)
C1—C61.409 (2)C4—H40.946 (9)
C1—C21.430 (2)C5—H50.947 (9)
C2—C31.357 (2)
N2—O2—N1109.4 (1)N1—C6—C1106.9 (1)
O1—N1—C6136.0 (1)N1—C6—C5129.7 (1)
O1—N1—O2117.7 (1)C1—C6—C5123.5 (1)
C6—N1—O2106.3 (1)C3—C2—H2124 (1)
C1—N2—O2105.0 (1)C1—C2—H2119 (1)
N2—C1—C6112.5 (1)C2—C3—H3117 (1)
N2—C1—C2128.0 (1)C4—C3—H3120 (1)
C6—C1—C2119.5 (1)C5—C4—H4118 (1)
C3—C2—C1116.8 (1)C3—C4—H4120 (1)
C2—C3—C4122.9 (1)C4—C5—H5122 (1)
C5—C4—C3121.9 (1)C6—C5—H5122 (1)
C4—C5—C6115.4 (1)
N2—O2—N1—O1178.7 (1)O1—N1—C6—C1−178.3 (1)
N2—O2—N1—C6−0.4 (1)O2—N1—C6—C10.6 (1)
N1—O2—N2—C10.1 (1)O1—N1—C6—C51.2 (2)
O2—N2—C1—C60.3 (2)O2—N1—C6—C5−179.9 (1)
O2—N2—C1—C2−179.1 (1)N2—C1—C6—N1−0.5 (2)
N2—C1—C2—C3179.9 (1)C2—C1—C6—N1178.9 (1)
C6—C1—C2—C30.6 (2)N2—C1—C6—C5179.9 (1)
C1—C2—C3—C4−0.1 (2)C2—C1—C6—C5−0.7 (2)
C2—C3—C4—C5−0.4 (2)C4—C5—C6—N1−179.2 (1)
C3—C4—C5—C60.3 (2)C4—C5—C6—C10.2 (2)

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: TK2443).

References

  • Ammon, H. L. & Bhattacharjee, S. K. (1982). Acta Cryst. B38, 2498–2502.
  • Barbour, L. J. (2001). J. Supramol. Chem.1, 189–191.
  • Bird, C. W. (1993). Tetrahedron, 49, 8441–8448.
  • Britton, D. & Olson, J. M. (1979). Acta Cryst. B35, 3076–3078.
  • Bruker (2008). APEX2 and SAINT Bruker AXS Inc., Madison, Wisconsin, USA.
  • Cerecetto, H. & González, M. (2007). Topics Heterocycl. Chem.10, 265–308.
  • Friedrichsen, W. (1995). J. Mol. Struct. (Theochem), 342, 23–31.
  • Ojala, C. R., Ojala, W. H., Britton, D. & Gougoutas, J. Z. (1999). Acta Cryst. B55, 530–542. [PubMed]
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  • Westrip, S. P. (2009). publCIF In preparation.
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