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
CCDC reference: 164674
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).
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.
nitrocarbamimidoyl azide
top
Crystal data top
CH2N6O2 | Z = 4 |
Mr = 130.09 | F(000) = 264 |
Triclinic, P1 | Dx = 1.701 Mg m−3 |
a = 9.9302 (8) Å | Cu Kα radiation, λ = 1.5418 Å |
b = 7.9433 (9) Å | Cell parameters from 24 reflections |
c = 7.1288 (8) Å | θ = 26–34° |
α = 98.31 (1)° | µ = 1.37 mm−1 |
β = 110.58 (1)° | T = 293 K |
γ = 75.108 (9)° | Lump, colourless |
V = 507.83 (9) Å3 | 0.32 × 0.30 × 0.29 mm |
Data collection top
Kuma KM-4 four-circle diffractometer | Rint = 0.015 |
Radiation source: fine-focus sealed tube | θmax = 70.0°, θmin = 4.9° |
Graphite monochromator | h = −12→0 |
profile measured θ/2θ scans | k = −9→9 |
1971 measured reflections | l = −8→8 |
1851 independent reflections | 2 standard reflections every 50 reflections |
1713 reflections with I > 2σ(I) | intensity decay: none |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.034 | All 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 reflections | Δρmax = 0.21 e Å−3 |
180 parameters | Δρmin = −0.20 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 1997), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0089 (14) |
Crystal data top
CH2N6O2 | γ = 75.108 (9)° |
Mr = 130.09 | V = 507.83 (9) Å3 |
Triclinic, P1 | Z = 4 |
a = 9.9302 (8) Å | Cu Kα radiation |
b = 7.9433 (9) Å | µ = 1.37 mm−1 |
c = 7.1288 (8) Å | T = 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 reflections | 2 standard reflections every 50 reflections |
1851 independent reflections | intensity decay: none |
1713 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.034 | 0 restraints |
wR(F2) = 0.095 | All H-atom parameters refined |
S = 1.09 | Δρmax = 0.21 e Å−3 |
1851 reflections | Δρmin = −0.20 e Å−3 |
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 | x | y | z | Uiso*/Ueq | |
C1A | 0.74742 (16) | 0.00130 (17) | 0.6997 (2) | 0.0376 (3) | |
N1A | 0.66238 (13) | 0.10530 (15) | 0.55232 (17) | 0.0378 (3) | |
N2A | 0.87682 (17) | −0.10340 (18) | 0.7291 (2) | 0.0512 (4) | |
H1A | 0.917 (3) | −0.160 (3) | 0.842 (4) | 0.071 (6)* | |
H2A | 0.923 (3) | −0.099 (3) | 0.645 (3) | 0.071 (6)* | |
N3A | 0.71542 (13) | 0.11576 (15) | 0.40460 (17) | 0.0373 (3) | |
N4A | 0.68901 (17) | 0.00020 (18) | 0.8506 (2) | 0.0516 (4) | |
N5A | 0.56250 (16) | 0.09674 (17) | 0.82266 (18) | 0.0453 (3) | |
N6A | 0.45205 (19) | 0.1744 (2) | 0.8220 (2) | 0.0592 (4) | |
O1A | 0.62908 (12) | 0.21175 (15) | 0.27048 (16) | 0.0494 (3) | |
O2A | 0.83855 (13) | 0.03785 (16) | 0.40061 (18) | 0.0558 (3) | |
C1B | 0.22185 (15) | 0.48405 (17) | −0.05571 (19) | 0.0347 (3) | |
N1B | 0.14663 (12) | 0.37780 (14) | −0.02858 (16) | 0.0342 (3) | |
N2B | 0.20705 (17) | 0.55960 (19) | −0.2144 (2) | 0.0495 (4) | |
H1B | 0.262 (3) | 0.626 (3) | −0.206 (3) | 0.074 (7)* | |
H2B | 0.144 (2) | 0.535 (3) | −0.328 (3) | 0.063 (6)* | |
N3B | 0.03547 (13) | 0.33446 (14) | −0.18819 (16) | 0.0372 (3) | |
N4B | 0.33450 (14) | 0.52520 (18) | 0.11267 (18) | 0.0448 (3) | |
N5B | 0.33850 (13) | 0.46870 (17) | 0.27080 (18) | 0.0433 (3) | |
N6B | 0.35467 (17) | 0.4289 (2) | 0.4216 (2) | 0.0621 (4) | |
O1B | −0.03604 (12) | 0.24662 (14) | −0.15028 (16) | 0.0481 (3) | |
O2B | 0.00660 (14) | 0.37831 (17) | −0.35940 (16) | 0.0603 (4) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
C1A | 0.0448 (8) | 0.0351 (6) | 0.0353 (7) | −0.0093 (6) | 0.0144 (6) | 0.0050 (5) |
N1A | 0.0404 (7) | 0.0422 (6) | 0.0348 (6) | −0.0084 (5) | 0.0151 (5) | 0.0089 (5) |
N2A | 0.0534 (9) | 0.0501 (7) | 0.0495 (8) | 0.0026 (6) | 0.0198 (7) | 0.0194 (6) |
N3A | 0.0396 (7) | 0.0417 (6) | 0.0343 (6) | −0.0124 (5) | 0.0126 (5) | 0.0066 (5) |
N4A | 0.0597 (9) | 0.0551 (8) | 0.0431 (7) | 0.0013 (6) | 0.0247 (6) | 0.0180 (6) |
N5A | 0.0582 (10) | 0.0483 (7) | 0.0374 (6) | −0.0154 (7) | 0.0224 (6) | 0.0038 (5) |
N6A | 0.0574 (10) | 0.0678 (9) | 0.0597 (9) | −0.0113 (8) | 0.0310 (7) | 0.0010 (7) |
O1A | 0.0499 (7) | 0.0594 (6) | 0.0415 (6) | −0.0087 (5) | 0.0131 (5) | 0.0222 (5) |
O2A | 0.0456 (7) | 0.0729 (8) | 0.0532 (7) | −0.0001 (6) | 0.0258 (5) | 0.0157 (6) |
C1B | 0.0339 (7) | 0.0376 (7) | 0.0337 (6) | −0.0046 (5) | 0.0132 (5) | 0.0059 (5) |
N1B | 0.0353 (7) | 0.0382 (6) | 0.0294 (5) | −0.0088 (5) | 0.0086 (4) | 0.0071 (4) |
N2B | 0.0559 (9) | 0.0619 (8) | 0.0384 (7) | −0.0244 (7) | 0.0122 (6) | 0.0143 (6) |
N3B | 0.0397 (7) | 0.0368 (6) | 0.0335 (6) | −0.0074 (5) | 0.0097 (5) | 0.0052 (4) |
N4B | 0.0396 (7) | 0.0592 (8) | 0.0394 (7) | −0.0182 (6) | 0.0101 (5) | 0.0087 (5) |
N5B | 0.0329 (7) | 0.0589 (7) | 0.0361 (7) | −0.0129 (5) | 0.0063 (5) | 0.0042 (5) |
N6B | 0.0520 (9) | 0.0948 (11) | 0.0374 (7) | −0.0200 (8) | 0.0065 (6) | 0.0118 (7) |
O1B | 0.0505 (7) | 0.0478 (6) | 0.0517 (6) | −0.0227 (5) | 0.0159 (5) | 0.0011 (5) |
O2B | 0.0718 (8) | 0.0753 (8) | 0.0321 (5) | −0.0312 (6) | −0.0006 (5) | 0.0157 (5) |
Geometric parameters (Å, º) top
C1A—N1A | 1.3296 (18) | C1B—N2B | 1.3024 (18) |
C1A—N2A | 1.303 (2) | C1B—N1B | 1.3343 (17) |
C1A—N4A | 1.3921 (18) | C1B—N4B | 1.3891 (18) |
N1A—N3A | 1.3532 (15) | N1B—N3B | 1.3531 (16) |
N2A—H1A | 0.89 (2) | N2B—H1B | 0.83 (2) |
N2A—H2A | 0.89 (2) | N2B—H2B | 0.87 (2) |
N3A—O2A | 1.2284 (16) | N3B—O1B | 1.2280 (15) |
N3A—O1A | 1.2366 (16) | N3B—O2B | 1.2324 (15) |
N4A—N5A | 1.257 (2) | N4B—N5B | 1.2566 (17) |
N5A—N6A | 1.1104 (19) | N5B—N6B | 1.1104 (18) |
| | | |
N2A—C1A—N1A | 131.75 (14) | N2B—C1B—N1B | 131.03 (14) |
N2A—C1A—N4A | 112.86 (13) | N2B—C1B—N4B | 113.11 (13) |
N1A—C1A—N4A | 115.38 (13) | N1B—C1B—N4B | 115.86 (11) |
C1A—N1A—N3A | 117.98 (12) | C1B—N1B—N3B | 118.01 (11) |
C1A—N2A—H1A | 117.9 (14) | C1B—N2B—H1B | 119.2 (16) |
C1A—N2A—H2A | 116.5 (15) | C1B—N2B—H2B | 119.1 (14) |
H1A—N2A—H2A | 125 (2) | H1B—N2B—H2B | 122 (2) |
O2A—N3A—O1A | 121.65 (11) | O1B—N3B—O2B | 121.71 (12) |
O2A—N3A—N1A | 123.97 (11) | O1B—N3B—N1B | 114.80 (11) |
O1A—N3A—N1A | 114.38 (12) | O2B—N3B—N1B | 123.49 (11) |
N5A—N4A—C1A | 113.99 (12) | N5B—N4B—C1B | 113.28 (11) |
N6A—N5A—N4A | 170.43 (14) | N6B—N5B—N4B | 171.87 (15) |
| | | |
N2A—C1A—N1A—N3A | −3.0 (2) | N2B—C1B—N1B—N3B | 0.9 (2) |
N4A—C1A—N1A—N3A | 178.00 (12) | N4B—C1B—N1B—N3B | 179.78 (11) |
C1A—N1A—N3A—O2A | −1.6 (2) | C1B—N1B—N3B—O1B | −175.06 (12) |
C1A—N1A—N3A—O1A | 178.43 (12) | C1B—N1B—N3B—O2B | 5.01 (19) |
N2A—C1A—N4A—N5A | −178.20 (14) | N2B—C1B—N4B—N5B | 172.47 (13) |
N1A—C1A—N4A—N5A | 1.02 (19) | N1B—C1B—N4B—N5B | −6.64 (19) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N2A—H2A···O2A | 0.88 (3) | 1.99 (2) | 2.608 (2) | 126 (2) |
N2B—H2B···O2B | 0.86 (2) | 2.01 (2) | 2.589 (2) | 123 (2) |
N2A—H1A···O1Bi | 0.89 (3) | 2.21 (3) | 3.088 (2) | 167 (2) |
N2B—H1B···O1Aii | 0.83 (3) | 2.07 (3) | 2.880 (2) | 164 (2) |
N2B—H2B···O2Biii | 0.86 (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, −z−1. |
Experimental details
Crystal data |
Chemical formula | CH2N6O2 |
Mr | 130.09 |
Crystal system, space group | Triclinic, 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) |
V (Å3) | 507.83 (9) |
Z | 4 |
Radiation type | Cu Kα |
µ (mm−1) | 1.37 |
Crystal size (mm) | 0.32 × 0.30 × 0.29 |
|
Data collection |
Diffractometer | Kuma KM-4 four-circle diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 1971, 1851, 1713 |
Rint | 0.015 |
(sin θ/λ)max (Å−1) | 0.609 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.034, 0.095, 1.09 |
No. of reflections | 1851 |
No. of parameters | 180 |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.21, −0.20 |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N2A—H2A···O2A | 0.88 (3) | 1.99 (2) | 2.608 (2) | 126 (2) |
N2B—H2B···O2B | 0.86 (2) | 2.01 (2) | 2.589 (2) | 123 (2) |
N2A—H1A···O1Bi | 0.89 (3) | 2.21 (3) | 3.088 (2) | 167 (2) |
N2B—H1B···O1Aii | 0.83 (3) | 2.07 (3) | 2.880 (2) | 164 (2) |
N2B—H2B···O2Biii | 0.86 (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, −z−1. |
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).