Download citation
Download citation
link to html
Crystals of the title compound, nitro­carbam­imidoyl azide, CH2N6O2, consist of two symmetry-independent mol­ecules and the structure is stabilized by intra- and intermolecular hydrogen bonds. The mol­ecule possesses a nitr­imine structure.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101002827/av1067sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270101002827/av1067Isup2.hkl
Contains datablock I

CCDC reference: 164674

Comment top

Nitroguanyl azide, or l-azido-N-nitroforamidine, (I), is an interesting high energy compound (Lieber et al., 1951). The question of whether (I) is a primary nitramine or nitrimine still remains open. In earlier work, (I) was considered to be a primary nitramine (Lieber et al., 1951; Henry & Boschan, 1954; Henry et al., 1955; Scott et al., 1956). As the reaction ability, in particular the thermal stability, varies greatly for nitrimines and primary nitramines (Astachov, 1999), the question of the molecular structure of (I) is key to understanding its thermal decomposition mechanism. In addition, if (I) is a primary nitramine, there is a complication in the definition of the reaction centre of thermal decomposition, since azide and primary nitramine groups are rather close in thermal stability. In order to elucidate the structure of (I), an X-ray crystal-structure analysis has been undertaken and the results are presented here. \sch

The structure of (I) consists of four molecules in a triclinic unit cell. Each of the two symmetrically independent molecules, A and B, has a planar conformation (Fig. 1), stabilized by an N2—H2···O2 intramolecular hydrogen bond and enhanced by the favourable π-orbital overlap. Deviations from the least-squares plane through the non-H atoms are 0.026 (1) Å (r.m.s.) and 0.055 (1) Å (max) for molecule A, and 0.046 (1) Å (r.m.s.) and 0.061 (1) Å (max) for molecule B.

The geometric parameters of the intramolecular hydrogen bonds (Table 1) are nearly equal to those of other nitroguanidine derivatives (Choi, 1981; Nordenson, 1981; Nordenson & Hvoslef, 1981; Oyumi et al., 1987; Gao et al., 1991). The intermolecular N2A—H1A···O1B and N2B—H1B···O1A hydrogen bonds form a one-dimensional molecular chain of the –A—B—A—B-type. Two adjacent such chains are connected by an intermolecular N2B—H2B···O2B' hydrogen bond (Table 1) to form ribbons along the cell b axis (Fig. 2). It is worth noting that the N2B—H2B group is involved in both inter- and intramolecular hydrogen bonding at the same time.

We conclude that, in the solid state, (I) is not a primary nitramine, as was considered earlier, but possesses a nitrimine structure. Similar to other nitrimines (Choi, 1981; Nordenson, 1981; Nordenson & Hvoslef, 1981; Oyumi et al., 1987; Gao et al., 1991), the values of the N—N and C—N bond lengths in the nitrimine fragment of the molecule of (I) are intermediate between the values characteristic of single or double bonds. This indicates a delocalization of the electron density of the nitrimine fragment of the molecule, resulting in a decrease of the N—NO2 bond distance, a lengthening of the N—O bonds and an averaging of the C—N bonds. The determination of a nitrimine structure for (I) allows us to consider unequivocally that the azide function is the reaction centre which is responsible for thermal decomposition of the compound. The C—N3 bond length [1.392 (2) and 1.389 (2) Å in molecules A and B, respectively] is much shorter than in the case of aliphatic azides (1.47 Å for CH3—N3) and indicates the conjugation of the azide group with the delocalized π-electron density of the nitrimine fragment of the molecule. The presence of such a conjugation promotes the thermal decomposition of the azide function (Manelis et al., 1996) and, consequently, the thermal stability of (I) is expected to be lower in comparison with aliphatic and even with aromatic azides, and this is observed in practice (Astachov, 2000).

Related literature top

For related literature, see: Astachov (1999, 2000); Choi (1981); Gao et al. (1991); Henry & Boschan (1954); Henry et al. (1955); Lieber et al. (1951); Manelis et al. (1996); Nordenson (1981); Nordenson & Hvoslef (1981); Oyumi et al. (1987); Scott et al. (1956).

Experimental top

Caution: the compound should be treated as dangerously explosive! Compound (I) was synthesized as described earlier by Lieber et al. (1951). Single crystals were obtained by evaporation in air of an aqueous solution of (I), which was acidified by HCl to pH < 1 (in a neutral aqueous environment, (I) is isomerized to 5-nitraminotetrazole).

Computing details top

Data collection: KM-4 Software (Kuma, 1991); cell refinement: KM-4 Software; data reduction: DATARED in KM-4 Software; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 1995); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The molecule of (I) showing the atom-numbering scheme and with displacement ellipsoids at the 50% probability level. H atoms are drawn as small spheres of arbitrary radii. Mol A or B?
[Figure 2] Fig. 2. The hydrogen-bonding scheme in (I).
nitrocarbamimidoyl azide top
Crystal data top
CH2N6O2Z = 4
Mr = 130.09F(000) = 264
Triclinic, P1Dx = 1.701 Mg m3
a = 9.9302 (8) ÅCu Kα radiation, λ = 1.5418 Å
b = 7.9433 (9) ÅCell parameters from 24 reflections
c = 7.1288 (8) Åθ = 26–34°
α = 98.31 (1)°µ = 1.37 mm1
β = 110.58 (1)°T = 293 K
γ = 75.108 (9)°Lump, colourless
V = 507.83 (9) Å30.32 × 0.30 × 0.29 mm
Data collection top
Kuma KM-4 four-circle
diffractometer
Rint = 0.015
Radiation source: fine-focus sealed tubeθmax = 70.0°, θmin = 4.9°
Graphite monochromatorh = 120
profile measured θ/2θ scansk = 99
1971 measured reflectionsl = 88
1851 independent reflections2 standard reflections every 50 reflections
1713 reflections with I > 2σ(I) intensity decay: none
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.034All H-atom parameters refined
wR(F2) = 0.095 w = 1/[σ2(Fo2) + (0.0537P)2 + 0.1095P]
where P = (Fo2 + 2Fc2)/3
S = 1.09(Δ/σ)max = 0.009
1851 reflectionsΔρmax = 0.21 e Å3
180 parametersΔρmin = 0.20 e Å3
0 restraintsExtinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0089 (14)
Crystal data top
CH2N6O2γ = 75.108 (9)°
Mr = 130.09V = 507.83 (9) Å3
Triclinic, P1Z = 4
a = 9.9302 (8) ÅCu Kα radiation
b = 7.9433 (9) ŵ = 1.37 mm1
c = 7.1288 (8) ÅT = 293 K
α = 98.31 (1)°0.32 × 0.30 × 0.29 mm
β = 110.58 (1)°
Data collection top
Kuma KM-4 four-circle
diffractometer
Rint = 0.015
1971 measured reflections2 standard reflections every 50 reflections
1851 independent reflections intensity decay: none
1713 reflections with I > 2σ(I)
Refinement top
R[F2 > 2σ(F2)] = 0.0340 restraints
wR(F2) = 0.095All H-atom parameters refined
S = 1.09Δρmax = 0.21 e Å3
1851 reflectionsΔρmin = 0.20 e Å3
180 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
C1A0.74742 (16)0.00130 (17)0.6997 (2)0.0376 (3)
N1A0.66238 (13)0.10530 (15)0.55232 (17)0.0378 (3)
N2A0.87682 (17)0.10340 (18)0.7291 (2)0.0512 (4)
H1A0.917 (3)0.160 (3)0.842 (4)0.071 (6)*
H2A0.923 (3)0.099 (3)0.645 (3)0.071 (6)*
N3A0.71542 (13)0.11576 (15)0.40460 (17)0.0373 (3)
N4A0.68901 (17)0.00020 (18)0.8506 (2)0.0516 (4)
N5A0.56250 (16)0.09674 (17)0.82266 (18)0.0453 (3)
N6A0.45205 (19)0.1744 (2)0.8220 (2)0.0592 (4)
O1A0.62908 (12)0.21175 (15)0.27048 (16)0.0494 (3)
O2A0.83855 (13)0.03785 (16)0.40061 (18)0.0558 (3)
C1B0.22185 (15)0.48405 (17)0.05571 (19)0.0347 (3)
N1B0.14663 (12)0.37780 (14)0.02858 (16)0.0342 (3)
N2B0.20705 (17)0.55960 (19)0.2144 (2)0.0495 (4)
H1B0.262 (3)0.626 (3)0.206 (3)0.074 (7)*
H2B0.144 (2)0.535 (3)0.328 (3)0.063 (6)*
N3B0.03547 (13)0.33446 (14)0.18819 (16)0.0372 (3)
N4B0.33450 (14)0.52520 (18)0.11267 (18)0.0448 (3)
N5B0.33850 (13)0.46870 (17)0.27080 (18)0.0433 (3)
N6B0.35467 (17)0.4289 (2)0.4216 (2)0.0621 (4)
O1B0.03604 (12)0.24662 (14)0.15028 (16)0.0481 (3)
O2B0.00660 (14)0.37831 (17)0.35940 (16)0.0603 (4)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C1A0.0448 (8)0.0351 (6)0.0353 (7)0.0093 (6)0.0144 (6)0.0050 (5)
N1A0.0404 (7)0.0422 (6)0.0348 (6)0.0084 (5)0.0151 (5)0.0089 (5)
N2A0.0534 (9)0.0501 (7)0.0495 (8)0.0026 (6)0.0198 (7)0.0194 (6)
N3A0.0396 (7)0.0417 (6)0.0343 (6)0.0124 (5)0.0126 (5)0.0066 (5)
N4A0.0597 (9)0.0551 (8)0.0431 (7)0.0013 (6)0.0247 (6)0.0180 (6)
N5A0.0582 (10)0.0483 (7)0.0374 (6)0.0154 (7)0.0224 (6)0.0038 (5)
N6A0.0574 (10)0.0678 (9)0.0597 (9)0.0113 (8)0.0310 (7)0.0010 (7)
O1A0.0499 (7)0.0594 (6)0.0415 (6)0.0087 (5)0.0131 (5)0.0222 (5)
O2A0.0456 (7)0.0729 (8)0.0532 (7)0.0001 (6)0.0258 (5)0.0157 (6)
C1B0.0339 (7)0.0376 (7)0.0337 (6)0.0046 (5)0.0132 (5)0.0059 (5)
N1B0.0353 (7)0.0382 (6)0.0294 (5)0.0088 (5)0.0086 (4)0.0071 (4)
N2B0.0559 (9)0.0619 (8)0.0384 (7)0.0244 (7)0.0122 (6)0.0143 (6)
N3B0.0397 (7)0.0368 (6)0.0335 (6)0.0074 (5)0.0097 (5)0.0052 (4)
N4B0.0396 (7)0.0592 (8)0.0394 (7)0.0182 (6)0.0101 (5)0.0087 (5)
N5B0.0329 (7)0.0589 (7)0.0361 (7)0.0129 (5)0.0063 (5)0.0042 (5)
N6B0.0520 (9)0.0948 (11)0.0374 (7)0.0200 (8)0.0065 (6)0.0118 (7)
O1B0.0505 (7)0.0478 (6)0.0517 (6)0.0227 (5)0.0159 (5)0.0011 (5)
O2B0.0718 (8)0.0753 (8)0.0321 (5)0.0312 (6)0.0006 (5)0.0157 (5)
Geometric parameters (Å, º) top
C1A—N1A1.3296 (18)C1B—N2B1.3024 (18)
C1A—N2A1.303 (2)C1B—N1B1.3343 (17)
C1A—N4A1.3921 (18)C1B—N4B1.3891 (18)
N1A—N3A1.3532 (15)N1B—N3B1.3531 (16)
N2A—H1A0.89 (2)N2B—H1B0.83 (2)
N2A—H2A0.89 (2)N2B—H2B0.87 (2)
N3A—O2A1.2284 (16)N3B—O1B1.2280 (15)
N3A—O1A1.2366 (16)N3B—O2B1.2324 (15)
N4A—N5A1.257 (2)N4B—N5B1.2566 (17)
N5A—N6A1.1104 (19)N5B—N6B1.1104 (18)
N2A—C1A—N1A131.75 (14)N2B—C1B—N1B131.03 (14)
N2A—C1A—N4A112.86 (13)N2B—C1B—N4B113.11 (13)
N1A—C1A—N4A115.38 (13)N1B—C1B—N4B115.86 (11)
C1A—N1A—N3A117.98 (12)C1B—N1B—N3B118.01 (11)
C1A—N2A—H1A117.9 (14)C1B—N2B—H1B119.2 (16)
C1A—N2A—H2A116.5 (15)C1B—N2B—H2B119.1 (14)
H1A—N2A—H2A125 (2)H1B—N2B—H2B122 (2)
O2A—N3A—O1A121.65 (11)O1B—N3B—O2B121.71 (12)
O2A—N3A—N1A123.97 (11)O1B—N3B—N1B114.80 (11)
O1A—N3A—N1A114.38 (12)O2B—N3B—N1B123.49 (11)
N5A—N4A—C1A113.99 (12)N5B—N4B—C1B113.28 (11)
N6A—N5A—N4A170.43 (14)N6B—N5B—N4B171.87 (15)
N2A—C1A—N1A—N3A3.0 (2)N2B—C1B—N1B—N3B0.9 (2)
N4A—C1A—N1A—N3A178.00 (12)N4B—C1B—N1B—N3B179.78 (11)
C1A—N1A—N3A—O2A1.6 (2)C1B—N1B—N3B—O1B175.06 (12)
C1A—N1A—N3A—O1A178.43 (12)C1B—N1B—N3B—O2B5.01 (19)
N2A—C1A—N4A—N5A178.20 (14)N2B—C1B—N4B—N5B172.47 (13)
N1A—C1A—N4A—N5A1.02 (19)N1B—C1B—N4B—N5B6.64 (19)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2A—H2A···O2A0.88 (3)1.99 (2)2.608 (2)126 (2)
N2B—H2B···O2B0.86 (2)2.01 (2)2.589 (2)123 (2)
N2A—H1A···O1Bi0.89 (3)2.21 (3)3.088 (2)167 (2)
N2B—H1B···O1Aii0.83 (3)2.07 (3)2.880 (2)164 (2)
N2B—H2B···O2Biii0.86 (2)2.29 (2)3.056 (2)148 (2)
Symmetry codes: (i) x+1, y, z+1; (ii) x+1, y+1, z; (iii) x, y+1, z1.

Experimental details

Crystal data
Chemical formulaCH2N6O2
Mr130.09
Crystal system, space groupTriclinic, P1
Temperature (K)293
a, b, c (Å)9.9302 (8), 7.9433 (9), 7.1288 (8)
α, β, γ (°)98.31 (1), 110.58 (1), 75.108 (9)
V3)507.83 (9)
Z4
Radiation typeCu Kα
µ (mm1)1.37
Crystal size (mm)0.32 × 0.30 × 0.29
Data collection
DiffractometerKuma KM-4 four-circle
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
1971, 1851, 1713
Rint0.015
(sin θ/λ)max1)0.609
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.034, 0.095, 1.09
No. of reflections1851
No. of parameters180
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)0.21, 0.20

Computer programs: KM-4 Software (Kuma, 1991), DATARED in KM-4 Software, SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), SHELXTL (Sheldrick, 1995), SHELXL97.

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N2A—H2A···O2A0.88 (3)1.99 (2)2.608 (2)126 (2)
N2B—H2B···O2B0.86 (2)2.01 (2)2.589 (2)123 (2)
N2A—H1A···O1Bi0.89 (3)2.21 (3)3.088 (2)167 (2)
N2B—H1B···O1Aii0.83 (3)2.07 (3)2.880 (2)164 (2)
N2B—H2B···O2Biii0.86 (2)2.29 (2)3.056 (2)148 (2)
Symmetry codes: (i) x+1, y, z+1; (ii) x+1, y+1, z; (iii) x, y+1, z1.
 

Follow Acta Cryst. C
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds