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The title compound (Z)-2-nitro­ethen­amine, C2H4N2O2, is a small energetic compound composed of only C, H, N and O, with a density of 1.513 g cm-3. The mol­ecules of this crystal structure have bond lengths and angles that are characteristic of a type of push-pull ethyl­enes. The overall molecular organization in stacks of almost planar parallel layers is a result of intermolecular amine-to-nitro hydrogen bonding.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536801015124/om6046sup1.cif
Contains datablocks mx02cum, 1

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536801015124/om60461sup2.hkl
Contains datablock 1

CCDC reference: 175365

Key indicators

  • Single-crystal X-ray study
  • T = 293 K
  • Mean [sigma](C-C) = 0.002 Å
  • R factor = 0.044
  • wR factor = 0.119
  • Data-to-parameter ratio = 9.6

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


Yellow Alert Alert Level C:
REFLT_03 From the CIF: _diffrn_reflns_theta_max 66.68 From the CIF: _reflns_number_total 650 TEST2: Reflns within _diffrn_reflns_theta_max Count of symmetry unique reflns 691 Completeness (_total/calc) 94.07% Alert C: < 95% complete
0 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
1 Alert Level C = Please check

Comment top

Several olefins with nitro and amino substituents have been studied by X-ray crystal structure analysis (Gate et al., 1985; Hazell et al., 1980; Bemm & Östmark, 1998), spectroscopy and theoretical chemistry (Karafiloglou & Marcos, 1992) because of their importance in synthetic chemistry and their biological activity (Gate et al., 1992). The X-ray crystal structure of the simplest member of the nitroethenamine family, (Z)-2-nitroethenamine, (1), has not been reported yet and is the subject of this article. This type of ethylene is commonly referred to as a push–pull ethylene because of the effects of the nitro and amino substituents on the π-electron distribution, as illustrated by the resonance structures of (1a), (1 b), and (1c). In common with other members of this group, the combined effects of the electron-withdrawing nitro group and the electron-donating amino group serve to lengthen the central olefin bond of the title compound from a `normal' value of 1.317 Å (Allen et al., 1987) to the observed value of 1.363 Å. In a similar molecule (1,1-diaminodinitroethylene), the central bond is lengthened to 1.456 Å (Bemm & Östmark, 1998). This is substantially longer than the distance in the title compound, due to the stronger push–pull effect and increased steric crowding. In addition to the lengthening of the central bond, the terminal bonds to the amino and the nitro substituents in these compounds are shortened. In the title compound, the amino C—N distance is 1.311 Å and the nitro C—N distance is 1.372 Å. These values are similar to those observed in the Cambridge Structural Database (CSD; Allen et al., 1987) for three RNH-CC—NO2 molecules; the reported CSD amino C—N distances range from 1.303 to 1.335 Å (Gate et al., 1985; Hazell & Mukhopadhyay, 1980; Dianez et al., 1985; Schlueter & Cook, 1989) and the nitro C—N distances range from 1.378 to 1.395 Å. Thus, the observed terminal distances are always shorter than the expected (Allen et al., 1987) Csp2-amino and Csp2-nitro distances of 1.336 and 1.468 Å, respectively. The push–pull effect also plays a role in reducing the barrier to rotation of the olefin bond. This barrier, which is normally very high, is lowered, permitting large distortions from `olefinic' planarity when bulky groups are substituted on the amine (e.g., see Baum et al., 1992). The title molecule, (Z)-2-nitroethenamine, is almost entirely planar. (The mean deviation from the plane through the molecule is 0.01 Å with a range of 0.00–0.02 Å.) The cis arrangement of amino and nitro in this molecule also enables an intramolecular hydrogen bond. In addition, there are two unique intermolecular NH—-NO2 hydrogen bonds which tie the molecules into sheets that are almost flat; the mean deviation of the atoms in each sheet from a plane is 0.133 Å. These slightly wavy sheets (see Fig. 2) extend throughout the crystal in two dimensions and form a parallel stack. This packing is similar to that seen in the crystals of the 1,1-diaminodinitroethylene (Bemm & Östmark, 1998).

Experimental top

Dr Mao-Xi Zhang of the University of Chicago Chemistry Department supplied crystals of the title compound.

Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 1997); software used to prepare material for publication: SHELXTL.

Figures top
[Figure 1] Fig. 1. View of (Z)-2-nitroethenamine.
[Figure 2] Fig. 2. A view of the packing down the b axis showing sheets of molecules, which occupy the (102) crystallographic planes. The hydrogen-bonded sheets are not quite planar, but are slightly wavy; the mean deviation of the atoms from the best plane through each sheet is 0.133 Å.
(Z)-2-nitroethenamine top
Crystal data top
C2H4N2O2F(000) = 184
Mr = 88.07Dx = 1.513 Mg m3
Monoclinic, P21/cCu Kα radiation, λ = 1.54178 Å
a = 5.5459 (2) ÅCell parameters from 1596 reflections
b = 10.3058 (3) Åθ = 7.8–66.8°
c = 6.8702 (3) ŵ = 1.18 mm1
β = 100.131 (2)°T = 293 K
V = 386.54 (2) Å3Plate, pale yellow
Z = 40.39 × 0.27 × 0.03 mm
Data collection top
CCD area-detector
diffractometer
650 independent reflections
Radiation source: fine-focus sealed tube593 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.029
ϕ and ω scansθmax = 66.7°, θmin = 7.8°
Absorption correction: multi-scan
(SADABS; Bruker, 2001)
h = 66
Tmin = 0.75, Tmax = 0.97k = 1111
1860 measured reflectionsl = 87
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.044Only H-atom coordinates refined
wR(F2) = 0.119 w = 1/[σ2(Fo2) + (0.0824P)2 + 0.0213P]
where P = (Fo2 + 2Fc2)/3
S = 1.09(Δ/σ)max < 0.001
650 reflectionsΔρmax = 0.18 e Å3
68 parametersΔρmin = 0.24 e Å3
0 restraintsExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.144 (15)
Crystal data top
C2H4N2O2V = 386.54 (2) Å3
Mr = 88.07Z = 4
Monoclinic, P21/cCu Kα radiation
a = 5.5459 (2) ŵ = 1.18 mm1
b = 10.3058 (3) ÅT = 293 K
c = 6.8702 (3) Å0.39 × 0.27 × 0.03 mm
β = 100.131 (2)°
Data collection top
CCD area-detector
diffractometer
650 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2001)
593 reflections with I > 2σ(I)
Tmin = 0.75, Tmax = 0.97Rint = 0.029
1860 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0440 restraints
wR(F2) = 0.119Only H-atom coordinates refined
S = 1.09Δρmax = 0.18 e Å3
650 reflectionsΔρmin = 0.24 e Å3
68 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.8749 (2)0.79870 (13)0.40604 (19)0.0630 (5)
H1A1.011 (4)0.8389 (14)0.466 (3)0.076*
H1B0.754 (3)0.850 (2)0.354 (3)0.076*
C10.8617 (2)0.67328 (15)0.4003 (2)0.0613 (5)
H10.998 (3)0.6280 (15)0.461 (2)0.074*
C20.6720 (2)0.59581 (14)0.3149 (2)0.0609 (5)
H20.688 (3)0.509 (2)0.317 (2)0.073*
N20.45367 (18)0.64422 (12)0.21808 (15)0.0569 (5)
O2A0.28745 (17)0.56588 (11)0.14658 (18)0.0782 (5)
O2B0.41900 (18)0.76326 (10)0.20014 (16)0.0665 (5)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0529 (8)0.0575 (9)0.0717 (9)0.0015 (5)0.0081 (6)0.0036 (5)
C10.0517 (8)0.0577 (9)0.0678 (9)0.0071 (6)0.0076 (6)0.0008 (6)
C20.0555 (8)0.0462 (8)0.0741 (10)0.0070 (6)0.0077 (6)0.0025 (6)
N20.0502 (7)0.0500 (8)0.0659 (8)0.0007 (5)0.0029 (5)0.0004 (4)
O2A0.0570 (7)0.0570 (8)0.1083 (10)0.0059 (4)0.0192 (6)0.0020 (5)
O2B0.0565 (7)0.0469 (8)0.0881 (9)0.0058 (4)0.0093 (5)0.0031 (4)
Geometric parameters (Å, º) top
N1—C11.295 (2)N1—H1A0.90 (2)
C1—C21.368 (2)N1—H1B0.88 (2)
C2—N21.3688 (16)C1—H10.925 (18)
N2—O2B1.2445 (15)C2—H20.90 (2)
N2—O2A1.2584 (14)
N1—C1—C2129.10 (13)C1—N1—H1B123.4 (13)
C1—C2—N2122.92 (14)H1A—N1—H1B115.7 (17)
O2B—N2—O2A120.26 (11)N1—C1—H1116.9 (11)
O2B—N2—C2121.03 (12)C2—C1—H1114.0 (11)
O2A—N2—C2118.71 (12)C1—C2—H2120.6 (10)
C1—N1—H1A120.9 (11)N2—C2—H2116.5 (10)
N1—C1—C2—N20.5 (2)C1—C2—N2—O2A178.87 (13)
C1—C2—N2—O2B1.26 (19)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1B···O2B0.88 (2)2.161 (19)2.6959 (16)118.8 (16)
N1—H1A···O2Ai0.90 (2)2.04 (2)2.9299 (16)169.0 (14)
N1—H1B···O2Aii0.88 (2)2.24 (2)2.8997 (19)131.9 (16)
Symmetry codes: (i) x+1, y+3/2, z+1/2; (ii) x+1, y+1/2, z+1/2.

Experimental details

Crystal data
Chemical formulaC2H4N2O2
Mr88.07
Crystal system, space groupMonoclinic, P21/c
Temperature (K)293
a, b, c (Å)5.5459 (2), 10.3058 (3), 6.8702 (3)
β (°) 100.131 (2)
V3)386.54 (2)
Z4
Radiation typeCu Kα
µ (mm1)1.18
Crystal size (mm)0.39 × 0.27 × 0.03
Data collection
DiffractometerCCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 2001)
Tmin, Tmax0.75, 0.97
No. of measured, independent and
observed [I > 2σ(I)] reflections
1860, 650, 593
Rint0.029
(sin θ/λ)max1)0.596
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.044, 0.119, 1.09
No. of reflections650
No. of parameters68
H-atom treatmentOnly H-atom coordinates refined
Δρmax, Δρmin (e Å3)0.18, 0.24

Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2001), SAINT, SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), SHELXTL (Sheldrick, 1997), SHELXTL.

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1B···O2B0.88 (2)2.161 (19)2.6959 (16)118.8 (16)
N1—H1A···O2Ai0.90 (2)2.04 (2)2.9299 (16)169.0 (14)
N1—H1B···O2Aii0.88 (2)2.24 (2)2.8997 (19)131.9 (16)
Symmetry codes: (i) x+1, y+3/2, z+1/2; (ii) x+1, y+1/2, z+1/2.
 

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