Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101010125/av1078sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270101010125/av1078Isup2.hkl |
CCDC reference: 173386
Single crystals of (I) were obtained by crystallization from ethanol (m.p. 408 K with decomposition).
Data collection: KM-4 Software (Kuma Diffraction, 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.
Fig. 1. The molecule of (I) showing the atom-numbering scheme and displacement ellipsoids at the 50% probability level. H atoms are drawn as small spheres of arbitrary radii. |
C2H2N6O4 | F(000) = 352 |
Mr = 174.10 | Dx = 1.800 Mg m−3 |
Monoclinic, P21/c | Cu Kα radiation, λ = 1.5418 Å |
a = 9.213 (3) Å | Cell parameters from 25 reflections |
b = 7.761 (1) Å | θ = 20–28° |
c = 10.180 (2) Å | µ = 1.52 mm−1 |
β = 118.04 (2)° | T = 293 K |
V = 642.5 (3) Å3 | Lump, colourless |
Z = 4 | 0.27 × 0.25 × 0.24 mm |
Kuma KM-4 four-circle diffractometer | Rint = 0.023 |
Radiation source: fine-focus sealed tube | θmax = 69.9°, θmin = 5.4° |
Graphite monochromator | h = 0→10 |
profile measured θ/2θ scans | k = −5→9 |
1254 measured reflections | l = −12→10 |
1177 independent reflections | 2 standard reflections every 50 reflections |
978 reflections with I > 2σ(I) | intensity decay: none |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.038 | All H-atom parameters refined |
wR(F2) = 0.108 | w = 1/[σ2(Fo2) + (0.0666P)2 + 0.0898P] where P = (Fo2 + 2Fc2)/3 |
S = 1.09 | (Δ/σ)max = 0.002 |
1177 reflections | Δρmax = 0.20 e Å−3 |
118 parameters | Δρmin = −0.26 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: 0.0097 (16) |
C2H2N6O4 | V = 642.5 (3) Å3 |
Mr = 174.10 | Z = 4 |
Monoclinic, P21/c | Cu Kα radiation |
a = 9.213 (3) Å | µ = 1.52 mm−1 |
b = 7.761 (1) Å | T = 293 K |
c = 10.180 (2) Å | 0.27 × 0.25 × 0.24 mm |
β = 118.04 (2)° |
Kuma KM-4 four-circle diffractometer | Rint = 0.023 |
1254 measured reflections | 2 standard reflections every 50 reflections |
1177 independent reflections | intensity decay: none |
978 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.038 | 0 restraints |
wR(F2) = 0.108 | All H-atom parameters refined |
S = 1.09 | Δρmax = 0.20 e Å−3 |
1177 reflections | Δρmin = −0.26 e Å−3 |
118 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
N2 | 0.78114 (16) | 0.06306 (16) | 0.14153 (14) | 0.0380 (3) | |
N1 | 0.68669 (16) | −0.04660 (17) | 0.16623 (14) | 0.0401 (3) | |
C5 | 0.79818 (19) | −0.12610 (19) | 0.28404 (17) | 0.0396 (4) | |
N4 | 0.95226 (16) | −0.07072 (18) | 0.33079 (16) | 0.0461 (4) | |
N3 | 0.94009 (16) | 0.05169 (17) | 0.23875 (16) | 0.0446 (4) | |
N6 | 0.75872 (19) | −0.26157 (17) | 0.35885 (16) | 0.0487 (4) | |
O1 | 0.61480 (17) | −0.30129 (18) | 0.30911 (16) | 0.0617 (4) | |
O2 | 0.87374 (19) | −0.3256 (2) | 0.46669 (17) | 0.0715 (5) | |
C7 | 0.7208 (2) | 0.1880 (2) | 0.02458 (18) | 0.0441 (4) | |
H1 | 0.803 (2) | 0.206 (3) | −0.009 (2) | 0.054 (5)* | |
H2 | 0.615 (3) | 0.156 (3) | −0.052 (3) | 0.068 (6)* | |
N8 | 0.69709 (16) | 0.35816 (18) | 0.08235 (16) | 0.0474 (4) | |
O3 | 0.7142 (2) | 0.36613 (18) | 0.20688 (17) | 0.0666 (4) | |
O4 | 0.66258 (18) | 0.47800 (19) | −0.00477 (18) | 0.0713 (5) |
U11 | U22 | U33 | U12 | U13 | U23 | |
N2 | 0.0288 (7) | 0.0396 (7) | 0.0376 (6) | −0.0011 (5) | 0.0089 (5) | −0.0008 (5) |
N1 | 0.0311 (7) | 0.0424 (7) | 0.0414 (7) | −0.0015 (5) | 0.0125 (5) | 0.0007 (5) |
C5 | 0.0354 (9) | 0.0369 (8) | 0.0421 (8) | 0.0026 (6) | 0.0146 (6) | −0.0017 (6) |
N4 | 0.0317 (8) | 0.0453 (7) | 0.0502 (8) | 0.0033 (5) | 0.0102 (6) | 0.0033 (6) |
N3 | 0.0291 (7) | 0.0464 (8) | 0.0477 (7) | −0.0002 (5) | 0.0093 (6) | 0.0009 (6) |
N6 | 0.0532 (10) | 0.0403 (7) | 0.0522 (8) | 0.0036 (6) | 0.0244 (7) | 0.0031 (6) |
O1 | 0.0534 (9) | 0.0543 (8) | 0.0789 (9) | −0.0096 (6) | 0.0324 (7) | 0.0009 (6) |
O2 | 0.0679 (10) | 0.0717 (9) | 0.0657 (8) | 0.0097 (7) | 0.0236 (8) | 0.0290 (7) |
C7 | 0.0367 (9) | 0.0489 (9) | 0.0377 (8) | −0.0044 (7) | 0.0100 (7) | 0.0035 (6) |
N8 | 0.0320 (8) | 0.0482 (8) | 0.0577 (9) | 0.0033 (5) | 0.0175 (6) | 0.0101 (6) |
O3 | 0.0801 (11) | 0.0589 (9) | 0.0695 (9) | 0.0124 (7) | 0.0423 (8) | 0.0004 (7) |
O4 | 0.0572 (9) | 0.0594 (9) | 0.0924 (11) | 0.0143 (6) | 0.0311 (8) | 0.0356 (8) |
N2—N1 | 1.3230 (19) | N6—O1 | 1.216 (2) |
N2—N3 | 1.330 (2) | N6—O2 | 1.217 (2) |
N2—C7 | 1.430 (2) | C7—N8 | 1.503 (2) |
N1—C5 | 1.310 (2) | C7—H1 | 0.97 (2) |
C5—N4 | 1.338 (2) | C7—H2 | 0.95 (2) |
C5—N6 | 1.441 (2) | N8—O3 | 1.203 (2) |
N4—N3 | 1.302 (2) | N8—O4 | 1.2196 (18) |
N1—N2—N3 | 114.10 (12) | O2—N6—C5 | 116.45 (15) |
N1—N2—C7 | 124.16 (13) | N2—C7—N8 | 109.95 (13) |
N3—N2—C7 | 121.71 (13) | N2—C7—H1 | 109.1 (12) |
C5—N1—N2 | 100.04 (13) | N8—C7—H1 | 106.8 (12) |
N1—C5—N4 | 114.73 (15) | N2—C7—H2 | 110.8 (13) |
N1—C5—N6 | 122.91 (15) | N8—C7—H2 | 105.5 (14) |
N4—C5—N6 | 122.36 (14) | H1—C7—H2 | 114.6 (18) |
N3—N4—C5 | 105.10 (13) | O3—N8—O4 | 125.95 (16) |
N4—N3—N2 | 106.03 (13) | O3—N8—C7 | 119.10 (13) |
O1—N6—O2 | 126.07 (16) | O4—N8—C7 | 114.95 (14) |
O1—N6—C5 | 117.48 (14) | ||
N3—N2—N1—C5 | −0.34 (16) | N1—C5—N6—O1 | −0.4 (2) |
C7—N2—N1—C5 | −178.42 (14) | N4—C5—N6—O1 | 179.01 (14) |
N2—N1—C5—N4 | 0.06 (17) | N1—C5—N6—O2 | 179.66 (16) |
N2—N1—C5—N6 | 179.50 (13) | N4—C5—N6—O2 | −0.9 (2) |
N1—C5—N4—N3 | 0.24 (18) | N1—N2—C7—N8 | 95.14 (17) |
N6—C5—N4—N3 | −179.21 (14) | N3—N2—C7—N8 | −82.79 (18) |
C5—N4—N3—N2 | −0.42 (16) | N2—C7—N8—O3 | −6.9 (2) |
N1—N2—N3—N4 | 0.51 (17) | N2—C7—N8—O4 | 172.56 (14) |
C7—N2—N3—N4 | 178.64 (14) |
Experimental details
Crystal data | |
Chemical formula | C2H2N6O4 |
Mr | 174.10 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 293 |
a, b, c (Å) | 9.213 (3), 7.761 (1), 10.180 (2) |
β (°) | 118.04 (2) |
V (Å3) | 642.5 (3) |
Z | 4 |
Radiation type | Cu Kα |
µ (mm−1) | 1.52 |
Crystal size (mm) | 0.27 × 0.25 × 0.24 |
Data collection | |
Diffractometer | Kuma KM-4 four-circle diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 1254, 1177, 978 |
Rint | 0.023 |
(sin θ/λ)max (Å−1) | 0.609 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.038, 0.108, 1.09 |
No. of reflections | 1177 |
No. of parameters | 118 |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.20, −0.26 |
Computer programs: KM-4 Software (Kuma Diffraction, 1991), DATARED in KM-4 Software, SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), SHELXTL (Sheldrick, 1995), SHELXL97.
Derivatives of tetrazole attract the attention of chemists in the field of explosives thanks to their large endothermicity and high nitrogen content and, at the same time, the relative stability of the tetrazole heterocycle. In principle, by the use of a combination of the tetrazole cycle with the usual explosophoric groups (–NO2, –N3, ═NNO2 etc.), the creation of new high-explosives is possible (Ostrovskii & Koldobskii, 1997). The structure of the title compound, (I), of this new high-explosive tetrazole class, has been investigated using single-crystal X-ray techniques. \sch
Earlier, we investigated the structure of 3-nitro-1-nitromethyl-1H-triazole, (II) (Vasiliev et al., 2000). Compound (I) differs from (II) in replacement of the ═CH– fragment in the 1,2,4-triazole ring by a ═N– fragment; the result is another heterocycle ring, tetrazole. One can expect that, after this replacement, the energetic and detonation parameters will increase at the expense of density, oxygen balance and an increase in the heat of explosive formation. At the same time, it is not absolutely clear how the transition from the triazole cycle to tetrazole will affect the thermal stability of the compound. Therefore, the first aim of the present work is to clarify how the replacement of the ═ CH– molecular fragment by ═N– will affect the geometric parameters of the molecule, especially the lengths of the C—NO2 bonds, the strength of which determines the thermal stability of nitro compounds (Manelis et al., 1996).
The geometric conformation of molecule (I) is close to that of (II). Similar to (II), the molecule of (I) (Fig. 1) consists of three planar fragments, namely a tetrazole ring, a nitromethylene group and a nitro group (H atoms are omitted from the present consideration). The tetrazole cycle is practically planar [r.m.s. deviation 0.0018 (9) Å and maximum deviation 0.0025 (9) Å]. The interatomic distances in the cycle are not equal, ranging from 1.302 (2) to 1.338 (2) Å. The nitro group bonded to the tetrazole cycle is rotated by 0.9 (3)° with respect to the ring plane. The nitromethylene group is strictly planar and is located nearly orthogonal [86.02 (7)°] to the tetrazole ring, while the O3—N8—C7—N2 torsion angle is -6.9 (2)°.
The C—NO2 bond lengths are not equal [1.441 (2) and 1.503 (2) Å]; the greater value corresponds to the bond in the nitroalkyl fragment of the molecule. Thus, the C—NO2 bonds in (I) are slightly stronger than those in (II) [1.450 (2) and 1.509 (2) Å; Vasiliev et al., 2000]. However, there is no evidence to suggest a similar or greater thermal stability of (I) in comparison with (II). The thermal decomposition of (II) begins with the breaking of the weaker C—NO2 bond, whereas for (I), an alternate path of thermal decomposition, typical for 2,5-substituted tetrazole derivatives (Manelis et al., 1996; Ostrovskii & Koldobskii, 1997), is possible, namely, the breaking of the N2—N3 bond. At the same time, it is known that a series of nitroalkyl 2,5-substituted tetrazoles decompose with a primary breaking of the C—NO2 bond (Stepanov et al., 2000). The X-ray data for bond lengths for (I) do not indicate a preference for one of the probable thermolysis paths. We are now carrying out an experimental study of the kinetics and mechanism of the thermal decomposition of (I), which will give an answer to the problems discussed above.
As expected, the density of (I) is greater than that of (II) (1.80 versus 1.76 Mg m-3). The density of (I) allows the consideration of its detonation parameters as being close to those of such a well known explosive as RDX, the former slightly exceeding the latter in the heat of explosion, at the expense of a greater heat of formation and better oxygen balance.