The title compound, CH
3N
5O
4, is almost planar, and the conformation is fixed by two intramolecular N-H
O hydrogen bonds. Owing to the delocalization of
-electron density over the whole molecule, there is through-conjugation, with the C-N, N-N and N-O bond lengths having values intermediate between those typical for the corresponding single and double bonds.
Supporting information
CCDC reference: 224649
Compound (I) was synthesized as described previously by Astratiev et al. (2003). Single crystals were obtained by crystallization of (I) from ethyl acetate.
Because the Kα1 and Kα2 maxima are resolved for the cell measurement reflections, we used the Kα1 maximum in the process of exact determination of the unit-cell parameters. H atoms were found in a difference Fourier map and refined in an isotropic approximation. We did not attempt to define the absolute structure because of the absence of strong enough anomalous scatterers in the compound.
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, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 1995); software used to prepare material for publication: SHELXL97.
Crystal data top
CH3N5O4 | F(000) = 304 |
Mr = 149.08 | Dx = 1.884 Mg m−3 |
Orthorhombic, P212121 | Cu Kα radiation, λ = 1.5406 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 24 reflections |
a = 9.6465 (6) Å | θ = 22–25° |
b = 10.7694 (7) Å | µ = 1.65 mm−1 |
c = 5.0583 (3) Å | T = 293 K |
V = 525.49 (6) Å3 | Block, colourless |
Z = 4 | 0.38 × 0.36 × 0.34 mm |
Data collection top
Kuma KM-4 diffractometer | Rint = 0.000 |
Radiation source: fine-focus sealed tube | θmax = 79.9°, θmin = 6.2° |
Graphite monochromator | h = 0→12 |
θ/2θ scans | k = 0→13 |
702 measured reflections | l = 0→6 |
702 independent reflections | 2 standard reflections every 50 reflections |
672 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)] = 0.024 | All H-atom parameters refined |
wR(F2) = 0.066 | w = 1/[σ2(Fo2) + (0.0454P)2 + 0.0728P] where P = (Fo2 + 2Fc2)/3 |
S = 1.00 | (Δ/σ)max = 0.002 |
702 reflections | Δρmax = 0.18 e Å−3 |
103 parameters | Δρmin = −0.17 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: 0.026 (2) |
Crystal data top
CH3N5O4 | V = 525.49 (6) Å3 |
Mr = 149.08 | Z = 4 |
Orthorhombic, P212121 | Cu Kα radiation |
a = 9.6465 (6) Å | µ = 1.65 mm−1 |
b = 10.7694 (7) Å | T = 293 K |
c = 5.0583 (3) Å | 0.38 × 0.36 × 0.34 mm |
Data collection top
Kuma KM-4 diffractometer | Rint = 0.000 |
702 measured reflections | 2 standard reflections every 50 reflections |
702 independent reflections | intensity decay: none |
672 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.024 | 0 restraints |
wR(F2) = 0.066 | All H-atom parameters refined |
S = 1.00 | Δρmax = 0.18 e Å−3 |
702 reflections | Δρmin = −0.17 e Å−3 |
103 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 | |
N1 | 0.49686 (13) | 0.45377 (12) | 0.8359 (3) | 0.0319 (3) | |
O1 | 0.62378 (12) | 0.46342 (13) | 0.8205 (3) | 0.0433 (3) | |
O2 | 0.44102 (13) | 0.38905 (12) | 1.0082 (3) | 0.0428 (3) | |
N2 | 0.40686 (13) | 0.51317 (12) | 0.6751 (3) | 0.0328 (3) | |
C | 0.45874 (15) | 0.58503 (13) | 0.4824 (3) | 0.0283 (3) | |
N3 | 0.58624 (15) | 0.60217 (15) | 0.4057 (3) | 0.0363 (3) | |
H1 | 0.649 (3) | 0.562 (2) | 0.498 (6) | 0.051 (5)* | |
H2 | 0.605 (3) | 0.656 (2) | 0.262 (5) | 0.051 (5)* | |
N4 | 0.34907 (13) | 0.64644 (14) | 0.3658 (3) | 0.0365 (3) | |
H3 | 0.2632 (19) | 0.6277 (16) | 0.418 (4) | 0.025 (4)* | |
N5 | 0.35413 (14) | 0.71820 (14) | 0.1419 (3) | 0.0367 (3) | |
O3 | 0.46412 (13) | 0.73377 (13) | 0.0299 (3) | 0.0439 (3) | |
O4 | 0.24347 (15) | 0.76143 (17) | 0.0771 (3) | 0.0672 (5) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
N1 | 0.0271 (6) | 0.0336 (6) | 0.0351 (7) | 0.0014 (5) | −0.0032 (6) | −0.0032 (6) |
O1 | 0.0246 (5) | 0.0540 (7) | 0.0513 (7) | 0.0041 (5) | −0.0062 (5) | 0.0036 (7) |
O2 | 0.0418 (7) | 0.0471 (6) | 0.0394 (6) | −0.0007 (5) | −0.0025 (6) | 0.0104 (6) |
N2 | 0.0220 (5) | 0.0384 (6) | 0.0381 (7) | 0.0023 (5) | −0.0008 (5) | 0.0045 (6) |
C | 0.0231 (6) | 0.0306 (7) | 0.0314 (7) | −0.0012 (5) | −0.0014 (6) | −0.0045 (6) |
N3 | 0.0214 (5) | 0.0490 (7) | 0.0385 (7) | 0.0002 (6) | 0.0007 (6) | 0.0022 (7) |
N4 | 0.0211 (6) | 0.0458 (7) | 0.0427 (8) | 0.0006 (5) | 0.0015 (6) | 0.0105 (7) |
N5 | 0.0304 (6) | 0.0415 (6) | 0.0381 (7) | 0.0009 (5) | −0.0011 (6) | 0.0052 (6) |
O3 | 0.0343 (6) | 0.0585 (7) | 0.0389 (7) | −0.0022 (5) | 0.0058 (5) | 0.0072 (6) |
O4 | 0.0382 (7) | 0.0916 (11) | 0.0719 (12) | 0.0181 (7) | 0.0033 (7) | 0.0413 (10) |
Geometric parameters (Å, º) top
N1—O1 | 1.2312 (18) | N3—H1 | 0.88 (3) |
N1—O2 | 1.2391 (19) | N3—H2 | 0.94 (2) |
N1—N2 | 1.351 (2) | N4—N5 | 1.372 (2) |
N2—C | 1.341 (2) | N4—H3 | 0.893 (19) |
C—N3 | 1.303 (2) | N5—O4 | 1.2098 (19) |
C—N4 | 1.380 (2) | N5—O3 | 1.2142 (18) |
| | | |
O1—N1—O2 | 121.64 (14) | C—N3—H2 | 119.7 (16) |
O1—N1—N2 | 124.11 (15) | H1—N3—H2 | 125 (2) |
O2—N1—N2 | 114.24 (13) | N5—N4—C | 126.55 (13) |
C—N2—N1 | 118.10 (12) | N5—N4—H3 | 113.9 (12) |
N3—C—N2 | 130.57 (14) | C—N4—H3 | 118.4 (12) |
N3—C—N4 | 121.90 (15) | O4—N5—O3 | 126.27 (15) |
N2—C—N4 | 107.52 (13) | O4—N5—N4 | 114.14 (14) |
C—N3—H1 | 115.1 (16) | O3—N5—N4 | 119.59 (14) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N3—H1···O1 | 0.88 (3) | 1.97 (2) | 2.601 (2) | 128 (1) |
N3—H1···O1i | 0.88 (3) | 2.38 (2) | 2.917 (2) | 120 (1) |
N3—H2···O3 | 0.94 (2) | 1.98 (2) | 2.648 (2) | 126 (1) |
N3—H2···O4ii | 0.94 (2) | 2.35 (2) | 3.228 (2) | 154 (1) |
N4—H3···O2iii | 0.89 (2) | 2.03 (2) | 2.915 (2) | 171 (1) |
Symmetry codes: (i) −x+3/2, −y+1, z−1/2; (ii) x+1/2, −y+3/2, −z; (iii) −x+1/2, −y+1, z−1/2. |
Experimental details
Crystal data |
Chemical formula | CH3N5O4 |
Mr | 149.08 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 293 |
a, b, c (Å) | 9.6465 (6), 10.7694 (7), 5.0583 (3) |
V (Å3) | 525.49 (6) |
Z | 4 |
Radiation type | Cu Kα |
µ (mm−1) | 1.65 |
Crystal size (mm) | 0.38 × 0.36 × 0.34 |
|
Data collection |
Diffractometer | Kuma KM-4 diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 702, 702, 672 |
Rint | 0.000 |
(sin θ/λ)max (Å−1) | 0.639 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.024, 0.066, 1.00 |
No. of reflections | 702 |
No. of parameters | 103 |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.18, −0.17 |
Selected geometric parameters (Å, º) topN1—O1 | 1.2312 (18) | N3—H1 | 0.88 (3) |
N1—O2 | 1.2391 (19) | N3—H2 | 0.94 (2) |
N1—N2 | 1.351 (2) | N4—N5 | 1.372 (2) |
N2—C | 1.341 (2) | N4—H3 | 0.893 (19) |
C—N3 | 1.303 (2) | N5—O4 | 1.2098 (19) |
C—N4 | 1.380 (2) | N5—O3 | 1.2142 (18) |
| | | |
O1—N1—O2 | 121.64 (14) | N2—C—N4 | 107.52 (13) |
O1—N1—N2 | 124.11 (15) | N5—N4—C | 126.55 (13) |
O2—N1—N2 | 114.24 (13) | O4—N5—O3 | 126.27 (15) |
C—N2—N1 | 118.10 (12) | O4—N5—N4 | 114.14 (14) |
N3—C—N2 | 130.57 (14) | O3—N5—N4 | 119.59 (14) |
N3—C—N4 | 121.90 (15) | | |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N3—H1···O1 | 0.88 (3) | 1.97 (2) | 2.601 (2) | 128 (1) |
N3—H1···O1i | 0.88 (3) | 2.38 (2) | 2.917 (2) | 120 (1) |
N3—H2···O3 | 0.94 (2) | 1.98 (2) | 2.648 (2) | 126 (1) |
N3—H2···O4ii | 0.94 (2) | 2.35 (2) | 3.228 (2) | 154 (1) |
N4—H3···O2iii | 0.89 (2) | 2.03 (2) | 2.915 (2) | 171 (1) |
Symmetry codes: (i) −x+3/2, −y+1, z−1/2; (ii) x+1/2, −y+3/2, −z; (iii) −x+1/2, −y+1, z−1/2. |
The search for new explosives with more effective physicochemical properties than those of known compounds is one of the more urgent tasks of modern chemical science in most industrially developed countries (Agrawal, 1998; Pagoria et al., 2002). Recently, the synthesis of 1,2-dinitroguanidine, (I), was reported (Astratiev et al., 2003). The compound is of practical interest as an explosive as it has a positive oxygen balance, and it is able to produce salts which will also be explosives. From a chemical standpoint, the compound is interesting because it contains primary nitramine and nitroguanyl groups in the molecule simultaneously. In the present communication, the crystal structure and molecular conformation of (I) are considered. \sch
A general view of the geometry of (I) is shown in Fig. 1. The molecular guanidine frame is practically planar; deviations from the least-squares plane through atoms C, N2, N3 and N4 are 0.003 (1) (r.m.s.) and 0.005 (1) Å (maximum). However, the nitro-group planes are rotated by a small angle [7.9 (3)° for the nitro group of the nitrimine moiety and −7.3 (4)° for the nitro group of the nitramine fragment] in opposite directions with respect to the plane of the guanidine fragment. This leads to evident deviations from the common least-squares plane through all non-H atoms [r.m.s. deviation = 0.073 (1) Å; maximum deviation = 0.127 (1) Å for atoms O1 and O3, respectively].
As in other nitrimines (Allen, 2002), the C—N, N—N and N—O bond lengths in (I) have values intermediate between those typical for the corresponding single and double bonds (Table 1). The formal single bond C—N3 [1.303 (2) Å], not the formal double bond C═N2 [1.341 (2) Å], has the shortest C—N bond distance in the molecule. This peculiarity of the structure, associated with the possibility of conjugation and redistribution of the electron density and being in contradiction to the representation shown in the Scheme, has been pointed out in other nitrimines (Nordenson, 1981a,b; Bracuti, 1999; Astachov et al., 2002, 2003; Vasiliev et al., 2003a,b). The planar configuration of atom N4 (sum of valence angles 359.5°), the almost planar geometry of the whole molecule and the averaged bond-length values testify to through-conjugation in a molecule of (I), i.e. on the propagation of nitrimine-specific delocalization of π-electron density on the second nitro group [see Scheme below, showing (a) the delocalization of π-electron density in the nitroguanyl fragment of nitroguanidine and its alkyl derivatives and (b) the 1,2-dinitroguanyl fragment of 1,2-dinitroguanidine or 1-methyl-1,2-dinitroguanidine]. In this regard, the structure of (I) does not differ from the structure of recently reported substituted 1,2-dinitroguanidines (Astachov et al., 2002; Vasiliev et al., 2003b).
The nitro group, as a strong electron-acceptor substituent, reduces the electron density on atom N4. The possibility of its participation in the nitrimine conjugation is reduced and, as a consequence, the C—N4 bond length [1.380 (2) Å] increases in comparison with the analogous bond length [1.322 (2) Å] in a nitroguanidine (Bracuti, 1999). The same situation is found in other nitrimines with electron-acceptor substituents, viz. 1-methyl-1-nitroso-2-nitroguanidine (Nordenson & Hvoslef, 1981; Rice et al., 1984), nitroguanylazide (Vasiliev et al., 2001), and 1-methyl-1,2-dinitroguanidine and 1-nitro-2-nitriminoimidazolidine (Astachov et al., 2003; Vasiliev et al., 2003b). The lengths of the analogous C—N bond in the listed compounds are in the range 1.379–1.408 Å. Nevertheless, the C—N4 bond in (I) is distinctly shorter in comparison with the analogous C-NHNO2 bond in primary alkylnitramines, viz. 1.463 (4) Å in 1,2-ethylendinitramine (Turley, 1968), 1.461 (3) Å in 1,3,5-trinitrazapentane (Zhang et al., 1984) or 1.433–1.443 Å in 1,3-di(2-nitraminoethyl)urea (Vasiliev et al., 2002). This fact appreciably affects the reaction ability of (I) and, primarily, its thermal stability. It is known that thermal decomposition of primary nitramines in the condensed state proceeds along the path of the ionic autoprolitic mechanism, with initial breakage of the C—N bond (Pavlov et al., 1989; Stepanov et al., 1998, 1999; Astachov, 1999). The more strong an acid is the primary nitramine, the less is its thermal stability (Astachov et al., 2000). Compound (I) is a strong acid, with a pKa of 1.1 (Astratiev et al., 2003). In spite of this, because of presence of conjugation between the primary nitramine and nitroguanyl groups, the C-NHNO2 bond in (I) is stronger than in primary alkylnitramines and, consequently, the thermal stability is also higher. However, as a whole, the thermal stability of (I) is not high. The compound flash-decomposes in the solid phase without melting, at 428–438 K, depending on the heating rate. Thus, compound (I) is inferior to secondary nitramines in terms of thermal stability, an important characteristic in practice, for example, in the established explosive RDX.
Even in the presence of conjugation between the primary nitramine and the nitroguanyl groups, which strengthens the C—N4 bond, this bond is the least strong C—N bond observed (Table 1). In accordance with this fact, compound (I) and other nitrimines with electron-acceptor substituents (1-methyl-1-nitroso-2-nitroguanidine, 1-methyl-1,2-dinitroguanidine, nitroguanylazide and 1-nitro-2-nitriminoimidazolidine) readily enter into nucleophilic replacement reactions, which are accompanied by the breaking of the C—N4 bond (Astratiev et al., 2003; Astachov et al., 2003; Vasiliev et al., 2003b). Nitrimines which do not contain electron-acceptor substituents have an analogous C—N bond length not greater than 1.330 Å (Allen, 2002) and, consequently, an essentially diminished reaction ability in nucleophilic replacement reactions (McKay, 1951).
The molecule of (I) has two intramolecular hydrogen bonds, N3—H1···O1 and N3—H2···O3 (Fig. 1), which result in a flat molecular conformation. The geometrical parameters of these bonds (Table 2) are close to those in other nitrimines (Allen, 2002). The crystal structure contains an intermolecular N4—H3···O2 hydrogen bond between the H atom of the primary nitramine group and an O atom of the nitro group of the nitrimine part of a neighbouring molecule. In addition, there is a possible weak N3—H2···O4' hydrogen bond between the H atom which participates in the intramolecular hydrogen bond and an O atom of the nitramine group of another molecule. This bond length (Table 2) has an extreme value or even exceeds some geometrical criteria of hydrogen-bond limits (Zefirov & Zorky, 1989). Nevertheless, taking into account that the question of the definition of hydrogen-bond limits is debatable (Steiner, 2000), we consider that the presence of the bond is possible. This is supported by the observation that the N3—H2 bond length is greater than the other N—H bonds in the molecule. One may suppose that the fact is just concerned with the participation of atom H2 in two hydrogen bonds simultaneously. As a result, the interatomic contact O3···O4' is short [2.749 (2) Å]. Thus, all O and N atoms available in a molecule take part in the formation of hydrogen bonds which connect individual molecules in an infinite structure in the crystal. On the other hand, we can not affirm confidently that there is an intermolecular N3—H1···O1' hydrogen bond, because of poor geometry parameters (Table 2). At the same time, in the crystal structure, there are no N—H···N2 hydrogen bonds, which are present in nitroguanidine (Bryden et al., 1956; Choi, 1981; Bracuti, 1999) and some of its derivatives (Nordenson & Hvoslef, 1981; Nordenson, 1981a,b; Rice et al., 1984; Astachov et al., 2003; Vasiliev et al., 2003a). In general, the net of hydrogen bonds in the crystal of (I) is less developed than in nitroguanidine crystals. As a consequence, compound (I) has a less compact molecular packing in the crystal. The calculated value of the molecular packing coefficient (Kpack) for the crystal of (I) is 0.693 (Kuzmina et al., 1990; Kuzmin & Katser, 1992). In comparison, for nitroguanidine, Kpack = 0.727, for 1-methyl-2-nitroguanidine, Kpack = 0.681, and for 1-methyl-1,2-dinitroguanidine, which has no intermolecular hydrogen bonds, Kpack = 0.655 (Vasiliev et al., 2003b).
The density of (I), 1.884 Mg m−3, is large enough, but is less than the density of most known powerful explosives, which have densities in the range 1.9–2.07 Mg m−3 (Agrawal, 1998; Pagoria et al., 2002). This does not allow (I) to compete with the latter on energetic parameters.