Low-temperature redetermination of benzofurazan 1-oxide

Ng, S.W.

doi:10.1107/S1600536809017036

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 65| Part 6| June 2009| Page o1275

doi:10.1107/S1600536809017036

Open

access

Low-temperature redetermination of benzofurazan 1-oxide

Seik Weng Ng ^a ^*

^aDepartment of Chemistry, University of Malaya, 50603 Kuala Lumpur, Malaysia
^*Correspondence e-mail: seikweng@um.edu.my

(Received 3 May 2009; accepted 6 May 2009; online 14 May 2009)

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 ) [Acta Cryst. B35, 3076–3078].

Related literature

For the room-temperature structure in the P $[\overline{1}]$ setting [6.772 (3), 7.515 (4), 7.759 (4) Å, 99.08 (3), 114.94 (3), 112.67 (3) °], see: Britton & Olson (1979). For the geometry-optimized structure, see: Friedrichsen, 1995 ; Ponder et al. (1994 ); Rauhut (1996 ). For details of the synthesis, see: Terrian et al. (1992 ); Wolthius (1979 ). For work mentioning the original structure, see: Ammon & Bhattacharjee (1982 ); Bird (1993 ); Cerecetto & González (2007 ); Ojala et al. (1999 ); Ramm et al. (1991 ).

Experimental

Crystal data

C₆H₄N₂O₂
M_r = 136.11
Triclinic, $[P \overline 1]$
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[F² > 2σ(F²)] = 0.035
wR(F²) = 0.110
S = 1.03
1276 reflections
108 parameters
4 restraints
All H-atom parameters refined
Δρ_max = 0.33 e Å⁻³
Δρ_min = −0.21 e Å⁻³

Table 1
Selected bond lengths (Å)

O1—N1	1.230 (1)
O2—N2	1.381 (1)
O2—N1	1.443 (2)
N1—C6	1.336 (2)
N2—C1	1.327 (2)
C1—C6	1.409 (2)
C1—C2	1.430 (2)
C2—C3	1.357 (2)
C3—C4	1.436 (2)
C4—C5	1.366 (2)
C5—C6	1.420 (2)

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

Supporting information

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

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

checkCIF report

Comment top

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.

Related literature top

For the room-temperature structure in the P1 setting [6.772 (3), 7.515 (4), 7.759 (4) Å, 99.08 (3), 114.94 (3), 112.67 (3) °], see: Britton & Olson (1979). For the geometry-optimized structure, see: Friedrichsen, 1995; Ponder et al. (1994); Rauhut (1996). For details of the synthesis, see: Terrian et al. (1992); Wolthius (1979). For work mentioning the original structure, see: Ammon & Bhattacharjee (1982); Bird (1993); Cerecetto & González (2007); Ojala et al. (1999); Ramm et al. (1991).

Experimental top

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

Computing details top

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

Figures top

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.

(I) top

Crystal data top

C₆H₄N₂O₂	Z = 2
M_r = 136.11	F(000) = 140
Triclinic, P1	D_x = 1.550 Mg m⁻³
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 6.6751 (2) Å	Cell parameters from 1320 reflections
b = 7.3256 (2) Å	θ = 3.2–28.3°
c = 7.6842 (2) Å	µ = 0.12 mm⁻¹
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 top

Bruker SMART APEX diffractometer	1110 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	R_int = 0.012
Graphite monochromator	θ_max = 27.5°, θ_min = 3.2°
ω scans	h = −7→8
1952 measured reflections	k = −9→9
1276 independent reflections	l = −9→9

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.035	All H-atom parameters refined
wR(F²) = 0.110	w = 1/[σ²(F_o²) + (0.0685P)² + 0.0855P] where P = (F_o² + 2F_c²)/3
S = 1.03	(Δ/σ)_max = 0.001
1276 reflections	Δρ_max = 0.33 e Å⁻³
108 parameters	Δρ_min = −0.21 e Å⁻³
4 restraints	Extinction correction: SHELXL, Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.03 (1)

Crystal data top

C₆H₄N₂O₂	γ = 111.747 (2)°
M_r = 136.11	V = 291.71 (1) Å³
Triclinic, P1	Z = 2
a = 6.6751 (2) Å	Mo Kα radiation
b = 7.3256 (2) Å	µ = 0.12 mm⁻¹
c = 7.6842 (2) Å	T = 100 K
α = 100.710 (2)°	0.30 × 0.25 × 0.10 mm
β = 114.265 (2)°

Data collection top

Bruker SMART APEX diffractometer	1110 reflections with I > 2σ(I)
1952 measured reflections	R_int = 0.012
1276 independent reflections

Refinement top

R[F² > 2σ(F²)] = 0.035	4 restraints
wR(F²) = 0.110	All H-atom parameters refined
S = 1.03	Δρ_max = 0.33 e Å⁻³
1276 reflections	Δρ_min = −0.21 e Å⁻³
108 parameters

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

	x	y	z	U_iso*/U_eq
O1	0.1183 (2)	0.2141 (2)	−0.0082 (1)	0.0274 (3)
O2	0.5178 (2)	0.2611 (2)	0.1146 (1)	0.0271 (3)
N1	0.3061 (2)	0.2329 (2)	0.1385 (2)	0.0211 (3)
N2	0.7112 (2)	0.2839 (2)	0.2955 (2)	0.0257 (3)
C1	0.6232 (2)	0.2701 (2)	0.4219 (2)	0.0188 (3)
C2	0.7496 (3)	0.2863 (2)	0.6308 (2)	0.0202 (3)
C3	0.6182 (3)	0.2669 (2)	0.7284 (2)	0.0207 (3)
C4	0.3643 (3)	0.2321 (2)	0.6312 (2)	0.0209 (3)
C5	0.2382 (3)	0.2174 (2)	0.4325 (2)	0.0199 (3)
C6	0.3750 (2)	0.2377 (2)	0.3296 (2)	0.0181 (3)
H2	0.919 (2)	0.310 (3)	0.693 (3)	0.030 (4)*
H3	0.701 (3)	0.278 (3)	0.867 (2)	0.037 (5)*
H4	0.281 (3)	0.221 (3)	0.706 (2)	0.027 (4)*
H5	0.072 (2)	0.197 (3)	0.369 (2)	0.031 (4)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1	0.0242 (5)	0.0333 (6)	0.0172 (5)	0.0139 (4)	0.0039 (4)	0.0130 (4)
O2	0.0270 (6)	0.0398 (6)	0.0190 (5)	0.0172 (5)	0.0137 (4)	0.0157 (4)
N1	0.0213 (6)	0.0237 (6)	0.0158 (5)	0.0105 (5)	0.0077 (5)	0.0098 (4)
N2	0.0237 (6)	0.0361 (7)	0.0202 (6)	0.0155 (5)	0.0120 (5)	0.0144 (5)
C1	0.0198 (6)	0.0199 (6)	0.0171 (6)	0.0096 (5)	0.0095 (5)	0.0090 (5)
C2	0.0187 (6)	0.0231 (6)	0.0175 (6)	0.0109 (5)	0.0072 (5)	0.0103 (5)
C3	0.0240 (7)	0.0215 (6)	0.0147 (6)	0.0109 (5)	0.0083 (5)	0.0093 (5)
C4	0.0246 (7)	0.0228 (6)	0.0192 (6)	0.0120 (5)	0.0137 (6)	0.0102 (5)
C5	0.0188 (6)	0.0213 (6)	0.0200 (6)	0.0104 (5)	0.0096 (5)	0.0096 (5)
C6	0.0200 (6)	0.0175 (6)	0.0136 (5)	0.0086 (5)	0.0066 (5)	0.0073 (4)

Geometric parameters (Å, º) top

O1—N1	1.230 (1)	C3—C4	1.436 (2)
O2—N2	1.381 (1)	C4—C5	1.366 (2)
O2—N1	1.443 (2)	C5—C6	1.420 (2)
N1—C6	1.336 (2)	C2—H2	0.956 (9)
N2—C1	1.327 (2)	C3—H3	0.948 (9)
C1—C6	1.409 (2)	C4—H4	0.946 (9)
C1—C2	1.430 (2)	C5—H5	0.947 (9)
C2—C3	1.357 (2)

N2—O2—N1	109.4 (1)	N1—C6—C1	106.9 (1)
O1—N1—C6	136.0 (1)	N1—C6—C5	129.7 (1)
O1—N1—O2	117.7 (1)	C1—C6—C5	123.5 (1)
C6—N1—O2	106.3 (1)	C3—C2—H2	124 (1)
C1—N2—O2	105.0 (1)	C1—C2—H2	119 (1)
N2—C1—C6	112.5 (1)	C2—C3—H3	117 (1)
N2—C1—C2	128.0 (1)	C4—C3—H3	120 (1)
C6—C1—C2	119.5 (1)	C5—C4—H4	118 (1)
C3—C2—C1	116.8 (1)	C3—C4—H4	120 (1)
C2—C3—C4	122.9 (1)	C4—C5—H5	122 (1)
C5—C4—C3	121.9 (1)	C6—C5—H5	122 (1)
C4—C5—C6	115.4 (1)

N2—O2—N1—O1	178.7 (1)	O1—N1—C6—C1	−178.3 (1)
N2—O2—N1—C6	−0.4 (1)	O2—N1—C6—C1	0.6 (1)
N1—O2—N2—C1	0.1 (1)	O1—N1—C6—C5	1.2 (2)
O2—N2—C1—C6	0.3 (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—C3	179.9 (1)	C2—C1—C6—N1	178.9 (1)
C6—C1—C2—C3	0.6 (2)	N2—C1—C6—C5	179.9 (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—C6	0.3 (2)	C4—C5—C6—C1	0.2 (2)

Experimental details

Crystal data
Chemical formula	C₆H₄N₂O₂
M_r	136.11
Crystal system, space group	Triclinic, P1
Temperature (K)	100
a, b, c (Å)	6.6751 (2), 7.3256 (2), 7.6842 (2)
α, β, γ (°)	100.710 (2), 114.265 (2), 111.747 (2)
V (Å³)	291.71 (1)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	0.12
Crystal size (mm)	0.30 × 0.25 × 0.10

Data collection
Diffractometer	Bruker SMART APEX diffractometer
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	1952, 1276, 1110
R_int	0.012
(sin θ/λ)_max (Å⁻¹)	0.650

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.035, 0.110, 1.03
No. of reflections	1276
No. of parameters	108
No. of restraints	4
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.33, −0.21

Computer programs: APEX2 (Bruker, 2008), SAINT (Bruker, 2008), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), X-SEED (Barbour, 2001), publCIF (Westrip, 2009).

Selected bond lengths (Å) top

O1—N1	1.230 (1)	C1—C2	1.430 (2)
O2—N2	1.381 (1)	C2—C3	1.357 (2)
O2—N1	1.443 (2)	C3—C4	1.436 (2)
N1—C6	1.336 (2)	C4—C5	1.366 (2)
N2—C1	1.327 (2)	C5—C6	1.420 (2)
C1—C6	1.409 (2)

Acknowledgements

I thank the University of Malaya for supporting this study.

References

Ammon, H. L. & Bhattacharjee, S. K. (1982). Acta Cryst. B38, 2498–2502. CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
Barbour, L. J. (2001). J. Supramol. Chem. 1, 189–191. CrossRef CAS Google Scholar
Bird, C. W. (1993). Tetrahedron, 49, 8441–8448. CrossRef CAS Web of Science Google Scholar
Britton, D. & Olson, J. M. (1979). Acta Cryst. B35, 3076–3078. CSD CrossRef CAS IUCr Journals Web of Science Google Scholar
Bruker (2008). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Cerecetto, H. & González, M. (2007). Topics Heterocycl. Chem. 10, 265–308. CrossRef CAS Google Scholar
Friedrichsen, W. (1995). J. Mol. Struct. (Theochem), 342, 23–31. CrossRef CAS Google Scholar
Ojala, C. R., Ojala, W. H., Britton, D. & Gougoutas, J. Z. (1999). Acta Cryst. B55, 530–542. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
Ponder, M., Fowler, J. E. & Schaeffer, H. F. (1994). J. Org. Chem. 59, 6431–6436. CrossRef CAS Web of Science Google Scholar
Ramm, M., Schultz, B., Rudert, R., Göhrmann, B. & Niclas, H.-J. (1991). Acta Cryst. C47, 1700–1702. CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
Rauhut, G. (1996). J. Comput. Chem. 17, 1848–1856. CAS Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Terrian, D. L., Houghtaling, M. A. & Ames, J. R. (1992). J Chem. Educ. 69, 589–590. CrossRef CAS Google Scholar
Westrip, S. P. (2009). publCIF. In preparation. Google Scholar
Wolthius, E. (1979). J. Chem. Educ. 56, 343–344. Google Scholar