N-diazo-bridged nitroazoles: Catenated nitrogen-atom chains compatible with nitro functionalities

Article abstract of DOI:10.1002/chem.201402762

N-diazo-bridged azoles were synthesized based on oxidative coupling of N-aminoazoles. Incorporation of extended catenated nitrogen-atom chains with nitro groups led to compounds with favorable functional compatibilities. This combination gives rise to a series of high-density energetic materials (HEDMs) with high heats of formation, enhanced densities, positive oxygen balances, and good detonation properties while retaining excellent thermal stabilities and relatively low impact sensitivities. Calculated and experimental studies showed the delicate balance between the length of the nitrogen atom chain, energetic performance, and inherent stability, thus, providing a promising strategy for designing advanced energetic materials.

Full text of DOI:10.1002/chem.201402762

DOI: 10.1002/chem.201402762
Full Paper
&
Energetic Materials
N-Diazo-Bridged Nitroazoles: Catenated Nitrogen-Atom Chains
Compatible with Nitro Functionalities
[a]
[b]
[a]
Ping Yin, Damon A. Parrish, and Jean’ne M. Shreeve*
Abstract: N-diazo-bridged azoles were synthesized based on
oxidative coupling of N-aminoazoles. Incorporation of ex-
tended catenated nitrogen-atom chains with nitro groups
led to compounds with favorable functional compatibilities.
This combination gives rise to a series of high-density ener-
getic materials (HEDMs) with high heats of formation, en-
hanced densities, positive oxygen balances, and good deto-
nation properties while retaining excellent thermal stabilities
and relatively low impact sensitivities. Calculated and experi-
mental studies showed the delicate balance between the
length of the nitrogen atom chain, energetic performance,
and inherent stability, thus, providing a promising strategy
for designing advanced energetic materials.
Introduction
Recently, the value of the diazo functionality in nitrogen-rich
heterocycles was demonstrated, thereby providing another
viable strategy toward the synthesis of high-nitrogen com-
The chemistry of nitrogen-rich compounds continues to attract
[
1]
[6]
increasing attention in the field of material science. Because
the synthesis of environmentally friendly compounds has
become the goal, the design of materials tends to focus more
on molecules that will degrade or decompose to species meet-
pounds. Oxidative coupling of amino groups results in the
formation of a nitrogen–nitrogen double bond, which acts as
a bridge between energetic heterocycles. Although the majori-
ty of investigations focus on the coupling of CꢁNH heterocy-
2
[
2]
ing that target. With this in mind, the study of high-nitrogen
compounds has become an important effort, because the
cles, compounds with the NꢁNH moiety are also favorable
2
[7]
precursors to diazo-bridged energetic materials. Compared
[
3]
combustion products are largely dinitrogen compounds. Ad-
ditionally, molecules with high nitrogen content typically have
high heats of formation, implying large energy release originat-
ing from formation of NꢀN bonds.
with the former type, oxidative coupling of NꢁNH substrates
2
enables the formation of longer catenated nitrogen-atom
chains, which contribute markedly to higher heats of forma-
tion. Additionally, N-diazo functionalization of acidic nitroazoles
tends to reduce their molecular acidity thus enhancing their
compatibility with other energetic ingredients and making
them more conducive to storage.
Reflecting on the developments in this field, it is seen that
synthetic strategies have been focused mainly on the poly-
[
4]
azido functionality of the smallest possible carbon or nitro-
[
5]
[1b]
gen-rich backbones, for example, tetrazole, tetrazine, and
Accompanying the growing interest in nitrogen-rich com-
pounds, there is an enthusiasm for studying azo coupling reac-
[
1c]
triazine. Considering overall properties, insensitivity toward
destructive stimuli is also an important criterion for energetic
materials. However, most azido-functionalized compounds are
sensitive to heat, impact, and friction, which makes them diffi-
cult to handle safely and restricts their further applications.
Dealing with the conflict between high energy and inherent
instability requires a deeper understanding of nitrogen-rich
compounds and thus makes this research area challenging.
[8]
tions in the pursuit of long catenated nitrogen-atom chains.
1,1’-Azobis-1,2,3-triazole, a structure which contains eight
catenated nitrogen atoms (N , 1), was synthesized successfully
8
by using 1-amino-1,2,3-triazole with sodium dichloroisocyanu-
rate (SDCl) and exhibits relatively better thermal stability in
[9]
comparison with other N compounds (Scheme 1). Similarly,
8
another example of an N compound, 2,2’-azobis(5-nitrotetra-
8
zole) (2), was synthesized from NꢁNH nitrotetrazole, but could
2
[10]
not be stabilized during isolation. To pursue longer nitrogen-
atom chains, this oxidative coupling route was extensively
studied to give 1,1’-azobis-tetrazole with ten catenated nitro-
[
a] Dr. P. Yin, Prof. Dr. J. M. Shreeve
Department of Chemistry, University of Idaho
Moscow, Idaho, 83844-2343 (USA)
Fax: (+1)208-885-9146
E-mail: jshreeve@uidaho.edu
[b] Dr. D. A. Parrish
Naval Research Laboratory, Code 6030
Washington, D.C. 20375-5001 (USA)
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201402762.
Scheme 1. Examples of reported N-diazo-bridged azoles.
Chem. Eur. J. 2014, 20, 1 – 7
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[
11]
gen atoms (N , 3). Recently, coupling of 1,5-diami-
10
notetrazole involving diazotization and nucleophilic
substitution resulted in the formation of a co-crystal
[
12]
with the longest nitrogen chain to date.
Although these investigations have forged a new
pathway leading to nitrogen-rich compounds, the
contradiction between energetic performance and
stability still exists in the catenated nitrogen-atom-
based energetic materials. There are a few such ma-
terials exhibiting good densities and detonation
properties, but their further applications are limited
by their greatly reduced stabilities. The challenge
may originate from the existing strategy for improv-
ing energetic properties, which mainly relies on the
increasing heat of formation arising from long caten-
ated nitrogen-atom chains. In comparison, less atten-
tion has been devoted to the oxidation of the organ-
ic framework. In general, the energy properties of en-
ergetic materials are not only related to the heat of
formation, but also to the oxygen balance, which re-
flects oxidative capacity to consume carbon and hy-
drogen in the molecule. We now report a study of N-
diazo-bridged nitroazoles with enhanced oxygen bal- Scheme 2. Synthesis of N-diazo-bridged nitroazoles.
ance and detonation performance. This new family of
energetic materials also shows excellent thermal sta-
bilities and relatively low impact sensitivities, which supports
good functional compatibilities in the combination of catenat-
ed nitrogen-atom chains with nitro groups.
Results and Discussion
Nitroazoles, including nitropyrazoles, nitroimidazoles, and 3-
[13]
nitro-1,2,4-triazole, were synthesized based on the literature.
Further reactions involving neutralization with ammonia and
Scheme 3. Azidation of an N-diazo-bridged compound.
amination by using O-tosylhydroxylamine (TsONH ) gave rise to
2
N-amino nitroazoles in good yields. Although oxidative cou-
pling of NꢁNH2 azoles have been reported, substrates with
ed from the reaction. These compounds were fully character-
ized by NMR and IR spectroscopies and elemental analyses.
Structural confirmation of 4, 7, and 9 by single-crystal X-ray dif-
fraction analyses is given in Figure 1, and crystal structure data
[8–11]
varying functionalities were not extensively investigated.
Optimization of oxidative coupling reactions of nitroazoles in-
dicates that temperature and oxidant used are very important
for the isolated yield and purity of the product (see the Sup-
porting Information). Modified conditions, by using an
[14]
for 8 may be found in the Supporting Information.
N-Azo bridged nitropyrazole 4 crystallizes in the monoclinic
C2/c space group. In the structure of 4 (Figure 1a), the pyr-
azole rings and the diazo group are nearly planar to form
a conjugated system, which is verified by the N(6)-N(1)-N(2)-
C(3) and N(6)-N(1)-C(5)-C(4) torsion angles of ꢁ174.82(9) and
174.71(9)8, respectively. The nitrogen atoms of the nitro
groups lie in the plane of the pyrazole ring as is clearly shown
by the N(1)-N(2)-C(3)-N(7) and N(2)-N(1)-C(5)-N(10) torsion
angles of 179.84(9) and 175.60(10)8, respectively; however, the
oxygen atoms are twisted out of the plane. Similar to 4,
a planar structure was also found in 7, which crystallizes in the
0.5 equivalent of sodium dichloroisocyanurate (SDCl) and
acetic acid at ꢁ108C, gave N-diazo-bridged azoles (4–9) in
moderate to good yields. Employing the same conditions, oxi-
dative coupling of chloro-substituted nitroazoles resulted in N-
diazo-bridged compounds 10 and 11 (Scheme 2).
In the oxidative coupling of 4,5-dinitro-1H-imidazol-1-amine,
10 was obtained as the only product when the azo coupling
reaction was performed with one equivalent of SDCl at room
temperature (Scheme 3). Because the preparation of 5-chloro-
4
-nitroimidazole required multistep syntheses, this one-pot
synthetic method provided to be a more convenient route to
0 from 4,5-dinitroimidazole. Reaction of 10 with sodium
monoclinic P2 /c space group (Figure 1b). The nitro groups of
1
1
7 lie within the plane of the parent rings, which is somewhat
different from 4 and is supported by the O1-N1-C1-N3 torsion
angle of ꢁ0.28(17)8 and N2-C3-N4-O4 torsion angle of
6.20(19)8.
azide led to 12, which has a higher nitrogen content. Similar
attempts to introduce azide into 11 produced an extremely
unstable azido-substituted product, which could not be isolat-
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Table 1. Properties of the N-functionalized energetic compounds.
[
a]
[b]
[c]
[d]
[e]
[f]
[g]
[h]
Comp. Tdecomp
d
DH
f
P
v
D
IS
[J]
FS
[N]
OB
[%]
o
ꢁ3
ꢁ1
ꢁ1
[
C]
[gcm ] [kJg
]
[GPa] [ms ]
4
5
6
7
8
9
1
240
223
195
258
232
247
271
251
154
194
80
1.81
1.82
1.80
1.85
1.83
1.80
1.86
1.92
1.77
1.620
1.774
1.65
1.80
2.01
2.01
1.61
1.73
1.79
2.83
1.80
1.62
3.77
5.87
6.29
ꢁ0.30
0.42
34.8 8928
35.1 8964
34.6 8834
35.6 8979
35.1 8932
33.5 8825
24.9 7632
30.6 8255
31.4 8702
25.2 7764
36.1 9185
19.5 6881
35.2 8977
5
5
2
60
80
40
4.67
4.67
3.27
4.67
4.67
15 160
10 120
10 160
ꢁ6.30
0
25 360 ꢁ14.95
1
1
4
2
4.2
40
40 ꢁ14.37
ꢁ58.53
7.79
1
1
3
2
(N
(N10
8
)
–
)
<1 <5 ꢁ28.92
TNT
RDX
300
230
15
–
ꢁ18.60
7.4 120
0
[
[
a] Decomposition temperature. [b] Density measured by gas pycnometer.
c] Heat of formation. [d] Detonation pressure (calculated with Explo5
[
15]
[15]
v6.01).
[e] Detonation velocity (calculated with Explo5 v6.01 ).
[
f] Impact sensitivity. [g] Friction sensitivity. [h] Oxygen balance (based on
CO) for C , M =molecular weight.
a
H
b
O
c
N
d
, 1600(cꢁaꢁb/2)/M
W
W
Moreover, oxygen balances (OB), a significant index indicat-
ing the deficiency or excess of oxygen, are also improved by
the introduction of nitro groups. Compounds 4, 5, 6, 7, 8, and
11 possess positive OB values ranging between 3.27 and
7.79%, whereas 9, 10, and 12 exhibit negative OB values rang-
ing from ꢁ14.37 to ꢁ6.30%.
With a large number of N=N and NꢁN bonds, the heats of
formation of N-diazo bridged compounds are higher than
those of unsubstituted nitroazoles, ranging from 1.62 to
ꢁ
1
3
.77 kJg . Of these, 12 with a azido functionalization has the
Figure 1. a) Single-crystal X-ray structure of 4. b) Single-crystal X-ray struc-
ture of 7. c) Single-crystal X-ray structure of 9.
most positive heat of formation.
Impact and friction-sensitivity measurements were made by
using standard BAM Fallhammer techniques. Although impact
sensitivities of N derivatives (4–6, 9, and 11) are relatively high
6
Compound 9 crystallizes in the monoclinic P2 /c space
(2–10 J), some N compounds (7, 8, and 10) have moderate
1
4
group (Figure 1c). The two triazole rings bridged by the diazo
group are nearly co-planar, thus holding the six catenated ni-
trogen atoms in the same plane. In the catenated nitrogen-
atom chains of 4, 7, and 9, the lengths of the single nitrogen–
nitrogen bonds are nearly the same, that is, longer than the
N(6)ꢁN(6A) double bond (4 1.242; 7 1.237; 9 1.234 ꢁ). The azo
double bond is slightly shorter than that of N8 compound
sensitivities (10–25 J). Friction sensitivity of these compounds
range from very sensitive to insensitive (40–360 N).
Based on the densities and heats of formation, energetic
[15]
properties were calculated with EXPLO5 v6.01. The detona-
tion pressures (P) and velocities (D) of 4–12 range from 24.9 to
ꢁ
1
35.6 GPa and from 7632 to 8979 ms , respectively (compara-
ꢁ
1
ꢁ1
ble to 1 25.2 GPa, 7764 ms ; 3 36.1 Gpa, 9185 ms ; RDX
ꢁ
1
1
(1.250 ꢁ), but longer than that of N10 compound 3 (1.178 ꢁ).
35.2 GPa, 8997 ms ). The combination of good densities and
high heats of formation, originating from both nitro and
N-diazo functionalization, contributes significantly to the ener-
getic performance. Among them, imidazole-based compound
8 exhibited good detonation properties, good thermal stabili-
ties, and relatively low impact and friction sensitivities, which
exceed those of RDX and suggests promising energetic
materials.
The physical properties of these diazo-bridged compounds
are given in Table 1. All of the compounds, except for 12,
namely, 4–11 decompose at temperatures (Tdecomp) greater than
1958C, and with the exception of 6, the thermal behavior of
most of the compounds is comparable to RDX (Tdecomp 2308C)
and superior to the derivatives with more catenated nitrogen
atoms (1 194; 3 808C). Arising from the introduction of polyni-
tro groups, these diazo compounds exhibit high densities
ꢁ
3
ꢁ3
ranging from 1.77 to 1.92 gcm (1 1.620; 3 1.774 gcm ; trini-
Conclusion
trotoluene (TNT) 1.65; cyclotrimethylenetrinitramine (RDX)
ꢁ3
1
.80 gcm ). Several of these new diazo bridged compounds
A family of N-diazo-bridged nitroazoles was prepared and fully
characterized. Oxidative coupling of various N-amino nitro-
azoles led to a series of energetic materials with four to six
are of interest because of their enhanced densities with favora-
ble thermal stabilities.
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catenated nitrogen atom structures. X-ray diffraction analysis
of 4, 7, 8, and 9 demonstrated their unique planar structure,
which may contribute to their inherent stabilities. Compared
to the predominant study pursuing longer catenated nitrogen
chains, the assembly of nitro groups and nitrogen-atom chains
with suitable length shows better functional compatibility and
provides a more favorable pathway toward high-performance
catenated nitrogen-atom-based energetic materials. Addition-
ally, detailed properties of these compounds with diverse
catenated nitrogen-atom-chain lengths may provide an intrin-
sic view for the future design of energetic materials.
Theoretical studies
Computations were performed by using the Gaussian 03 (Revi-
sion D.01) suite of programs. The geometric optimization of the
structures and frequency analyses were carried out by using the
[21]
[21]
B3-LYP functional with the 6–31+G** basis set, and single-point
energies were calculated at the MP2/6–311++G** level. The opti-
mized structures were characterized to be true local-energy
minima on the potential-energy surface without imaginary fre-
quencies. According to the method of isodesmic reactions, the
gas-phase enthalpies of formation were computed and the enthal-
py of reaction is obtained by combining the MP2/6–311++G**
energy difference for the reactions, the scaled zero-point energies
(ZPE), and other thermal factors. Thus, the gas-phase enthalpy of
the species being investigated can be extracted.
Experimental Section
Solid-state heats of formation of the resulting compounds were
calculated with Equation (1):
Safety precautions
2
Although we have encountered no difficulties in preparing the
compounds in this work, manipulations must be carried out by
using appropriate standard safety precautions. Eye protection and
leather gloves must be worn at all times. Mechanical actions of
these energetic materials, involving scratching or scraping, must
be avoided.
DH ¼ DH ðgÞꢁDH ¼ DH ðgÞꢁ½0:000267 ꢂ A þ
f
f
sub
f
ð1Þ
0:5
1
:65 ꢂ ðvs2 totÞ þ 2:966ꢃ
The heat of sublimation was correlated with molecular surface area
[
22]
and the electrostatic interaction index vs2 tot. A presents the
ꢁ
3
surface area of the 0.001 electrons bohr isosurface of electronic
density of the molecule, v is the degree of balance between posi-
tive potential and negative potential on the isosurface, and vs2 tot
is a measure of variability of the electrostatic potential on the mo-
lecular surface. These descriptors A, v, and s2 tot were calculated
General methods
1
13
H and C NMR spectra were recorded on a Bruker 300 and
1
13
[23]
5
00 MHz NMR spectrometer. Chemical shifts for H and C NMR
by the reported method.
spectra are reported relative to Me Si or deuterated solvents. Ele-
4
mental analyses (C, H, N) were performed on a CE-440 Elemental
Analyzer. Melting and decomposition points were recorded on
a differential scanning calorimeter (DSC, TA Instruments Q10) at
a scan rate of 58Cmin . Impact and friction-sensitivity measure-
ments were made by using a standard BAM Fallhammer and
a BAM friction tester. IR spectra were recorded by using KBr pellets
with a Biorad Model 3000 FTS spectrometer. Densities were deter-
mined at RT by employing a Micromeritics AccuPyc 1330 gas
pycnometer.
General procedure for diazo-bridged nitroazoles (4–11)
ꢁ
1
N-Amino nitroazoles were prepared based on the literature proce-
[24]
dure. Nitroazoles (1 mmol) in acetonitrile (5 mL) were cooled in
an ice–salt bath. To this solution, a mixture of sodium dichloroiso-
cyanurate (SDCl, 0.5 mmol) and AcOH (0.2 mL) in water (10 mL)
was added dropwise at ꢁ108C. After addition the reaction was
stirred for 30 min at ꢁ108C. Then the reaction was neutralized to
pH 7–8 with sodium bicarbonate solution. The precipitate was iso-
lated by filtering the final mixture and washed by cold water, dried
in vacuum to give the desired product. Due to poor solubility, the
X-Ray crystallography
13
3
C NMR spectra for 6 and 12 could not be recorded.
A yellow prism of dimensions 0.84ꢂ0.52ꢂ0.34 mm for 4, a color-
3
less chunk crystal with dimensions 0.22ꢂ0.18ꢂ0.06 mm for 7,
a translucent light yellow colorless prism of dimensions 0.245ꢂ
3
0
0
.269ꢂ0.343 mm for 8, and a colorless prism of dimensions 0.31ꢂ
1
,2-Bis(3,5-dinitro-1H-pyrazol-1-yl)diazene (4)
3
.25ꢂ0.07 mm for 9 were mounted on a MiteGen MicroMesh by
1
using a small amount of Cargille Immersion oil. Data were collect-
ed on a Bruker three-circle platform diffractometer equipped with
a SMART APEX II CCD detector. The crystals were irradiated by
using graphite monochromated MoKa radiation (l=0.71073). An
Oxford Cobra low-temperature device was used to maintain the
crystals at a constant 150(2) K during data collection. Data collec-
tion was performed, and the unit cell was initially refined by using
White solid (105 mg, 62%); H NMR (300 MHz, CD
3
CN): d=
CN): d=154.7, 147.0,
106.5 ppm; IR (KBr pellet): u˜ =3152, 2886, 1573, 1531, 1453, 1389,
13
8.06 ppm (s, 2H); C NMR (75 MHz, CD
3
ꢁ1
1333, 1217, 1132, 1086, 986, 867, 739 cm ; elemental analysis (%)
calcd for C (342.14): C 21.06, H 0.59, N 40.94; found: C
21.01, H 0.60, N 40.55.
H N O
2 10 8
6
[16]
APEX2 [v2010.3–0]. Data reduction was performed using SAINT
[17]
[18]
[
v7.68 A] and XPREP [v2008/2]. Corrections were applied for
1
,2-Bis(3,4-dinitro-1H-pyrazol-1-yl)diazene (5)
Lorentz, polarization, and absorption effects by using SADABS
[
19]
1
[
v2008/1]. The structure was solved and refined with the aid of
Yellow solid (87 mg, 51%); H NMR (300 MHz, CD CN): d=
3
[20]
13
the programs in the SHELXTL-plus [v2008/4] system of programs.
9.31 ppm (s, 2H); C NMR (125 MHz, [D ]acetone): d=149.1, 132.8,
130.1 ppm; IR (KBr pellet): u˜ =3138, 1563, 1528, 1405, 1364, 1331,
1233, 1135, 975, 860, 804, 750 cm ; elemental analysis (%) calcd
for C H N O (342.14): C 21.06, H 0.59, N 40.94; found: C 21.09, H
6
2
The full-matrix least-squares refinement on F included atomic co-
ordinates and anisotropic thermal parameters for all nonhydrogen
atoms. The hydrogen atoms were included by using a riding
model.
ꢁ1
6
2
10
8
0.52, N 40.39.
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N,N’-(1,1’-(Diazene-1,2-diyl)bis(3,5-dinitro-1H-pyrazole-4,1-
diyl))bis(N-methylnitramide) (6)
reduce pressure, and the residue was washed with water to obtain
1
1
2. White solid (113 mg, 68%); H NMR (300 MHz, CD CN): d=
3
8
.19 ppm (s, 2H); IR (KBr pellet): u˜ =3131, 2162, 1561, 1488, 1387,
1
Yellow solid (120 mg, 41%); H NMR (300 MHz, CD CN): d=
ꢁ1
3
1273, 1248, 1188, 1098, 832 cm ; elemental analysis (%) calcd for
C H N O (334.17): C 21.57, H 0.60, N 58.68; found: C 21.92, H 0.57,
3
1
.76 ppm (s, 3H); IR (KBr pellet): u˜ =1605, 1547, 1445, 1329, 1294,
210, 1067, 892, 824, 790 cm ; elemental analysis (%) calcd for
6
2
14
4
ꢁ1
N 54.33. To prevent explosion, less than 0.3 mg of sample was
used, which caused a large relative error in the nitrogen value.
C H N O (490.22): C 19.60, H 1.23, N 40.00; found: C 19.81, H
8
6
14 12
1
.24, N 39.05.
Acknowledgements
1,2-Bis(2,4-dinitro-1H-imidazol-1-yl)diazene (7)
1
White solid (92 mg, 54%); H NMR (300 MHz, CD CN): d=8.80 ppm
(
3
We are grateful to Dr. Clifford Bedford, ONR (NOOO14–12–1–
1
3
s, 2H); C NMR (125 MHz, [D ]acetone): d 144.1, 141,4, 114.5 ppm;
6
0536).
IR (KBr pellet): u˜ =3147, 1649, 1571, 1502, 150.2, 1360, 1317, 1246,
ꢁ
1
1
125, 833 cm ; elemental analysis (%) calcd for C H N O (342.14):
6 2 10 8
C 21.06, H 0.59, N 40.94; found: C 21.37; H 0.58, N 40.32.
Keywords: catenated nitrogen chains · energetic properties ·
explosives · nitroazoles · nitrogen
1,2-Bis(4,5-dinitro-1H-imidazol-1-yl)diazene (8)
[
1] a) D. E. Chavez, M. A. Hiskey, R. D. Gilardi, Angew. Chem. 2000, 112,
861–1863; Angew. Chem. Int. Ed. 2000, 39, 1791–1793; b) M. H. V.
1
White solid (96 mg, 56%); H NMR (300 MHz, CD CN): d=8.48 ppm
3
1
1
3
(
(
s, 2H); C NMR (125 MHz, CD CN): d=139.7, 130.4, 129.4 ppm; IR
KBr pellet): u˜ =3138, 2924, 1691, 1544, 1468, 1359, 1318, 1259,
206, 1132, 922, 846, 810; elemental analysis (%) calcd for
C H N O (342.14): C 21.06, H 0.59, N 40.94; found: C 21.28, H 0.53,
3
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7262–7265; d) M. H. V. Huynh, M. A. Hiskey, D. E. Chavez, D. L. Naud,
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Joo, B. Twamley, S. Garg, J. M. Shreeve, Angew. Chem. 2008, 120, 6332–
6335; Angew. Chem. Int. Ed. 2008, 47, 6236–6239.
1
6
2
10
8
N 40.52.
1
,2-Bis(3-nitro-1H-1,2,4-triazol-1-yl)diazene (9)
1
White solid (89 mg, 70%); H NMR (300 MHz, CD CN): d=9.26 ppm
3
1
3
[2] J. Giles, Nature 2004, 427, 580–581.
[
(
s, 2H); C NMR (125 MHz, CD CN): d=162.7, 148.5 ppm; IR (KBr
3
pellet): u˜ =3123, 1737, 1559, 1510, 1437, 1350, 1300, 1188, 1021,
97, 837, 749 cm ; elemental analysis (%) calcd for C H N O
4 2 10 4
254.12): C 18.91; H 0.79, N 55.12; found: C 18.91, H 0.75, N 54.25.
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564–567.
ꢁ
1
9
(
1
,2-Bis(3-chloro-4-nitro-1H-pyrazol-1-yl)diazene (10)
Reaction using the general procedure from 5-chloro-4-nitro-1H-im-
idazol-1-amine gave 10. White solid (107 mg, 69%); alternative
method from 4,5-dinitro-1H-imidazol-1-amine was also studied:
[
4] K. Banert, Y. H. Joo, T. Rueffer, B. Wlafort, H. Lang, Angew. Chem. 2007,
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5] a) A. Hammerl, T. M. Klapçtke, P. Mayer, J. J. Weigand, Propellants Explos.
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4
,5-dinitro-1H-imidazol-1-amine (1 mmol) in acetonitrile (5 mL) was
cooled in an ice bath. To this solution, a mixture of sodium di-
chloroisocyanurate (1 mmol) and AcOH (0.5 mL) in water (10 mL)
was added dropwise at 0–58C. After addition, the reaction was
stirred for 12 h at RT. Then the reaction was neutralized to pH 7–8
with sodium bicarbonate solution. The precipitate was isolated by
filtering the final mixture and washed with cold water, dried in
vacuum to afford 10 (120 mg, 75%). H NMR (300 MHz, CD CN):
d=8.51 ppm (s, 2H); C NMR (125 MHz, [D ]acetone): d=128.3,
20.7 ppm; IR (KBr pellet): u˜ =3129, 1553, 1499, 1477, 1358, 1306,
[
6] a) L. Naud, M. A. Hiskey, H. H. Harry, J. Energ. Mater. 2003, 21, 57–62;
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2677; d) V. O. Kulagina, T. S. Novikova, L. I. Khmelnistky, Khim. Geterotsikl.
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1
3
13
[7] Q. Zhang, J. M. Shreeve, Angew. Chem. 2013, 125, 8954–8956; Angew.
Chem. Int. Ed. 2013, 52, 8792–8794.
6
1
1
[
8] a) C. Qi, S. H. Li, Y. C. Li, Y. A. Wang, X. K. Chen, S. P. Pang, J. Mater. Chem.
011, 21, 3221–3225; b) C. Qi, S. H. Li, Y. C. Li, Y. Wang, X. X. Zhao, S. P.
ꢁ1
257, 1194, 1099, 1011, 828 cm ; elemental analysis (%) calcd for
C H Cl N O (321.04): C 22.45, H, 0.63, N 34.90; found: C 22.41, H
2
6
2
2
8
4
Pang, Chem. Eur. J. 2012, 18, 16562–16570; c) Y. Tang, H. Yang, J. Shen,
B. Wu, X. Ju, C. Lu, G. Cheng, New J. Chem. 2012, 36, 2447–2450.
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Chem. Soc. 2010, 132, 12172–12173.
0
.71, N 34.95.
[
1
,2-Bis(4-chloro-3,5-dinitro-1H-pyrazol-1-yl)diazene (11)
[
[
10] T. M. Klapçtke, D. G. Piercey, J. Stierstorfer, Dalton Trans. 2012, 41,
9451–9459.
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Russ. Chem. Bull. 2010, 59, 1631–1638.
13
White solid (72 mg, 35%); C NMR (125 MHz, CD CN): d=150.7,
43.2, 111.2 ppm; IR (KBr pellet): u˜ =1569, 1523, 1426, 1322, 1221,
144, 1059, 888 cm ; elemental analysis (%) calcd for C Cl N O
411.03): C 17.53, H 0.00, N 34.08; found: C 17.97, H 0.15, N 32.97.
3
1
1
ꢁ
1
6 2 10 8
4
(
[
1
,2-Bis(5-azido-4-nitro-1H-imidazol-1-yl)diazene (12)
NaN3 (260 mg, 4 mmol) was added to the suspension of 10
161 mg, 0.5 mmol) in CH CN (20 mL) and H O (2 mL); the reaction
3 2
mixture was stirred for 24 h at RT. The solvent was removed under
(
Chem. Eur. J. 2014, 20, 1 – 7
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5
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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These are not the final page numbers! ÞÞ

Full Paper
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16] Bruker, APEX2 v2010.3–0. Bruker AXS Inc. Madison, Wisconsin, USA,
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kajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P.
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Received: March 25, 2014
Published online on && &&, 0000
&
&
Chem. Eur. J. 2014, 20, 1 – 7
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FULL PAPER
Explosive guys: Polynitro groups were
introduced as an oxidative source for
long catenated nitrogen-atom chains
&
Energetic Materials
P. Yin, D. A. Parrish, J. M. Shreeve*
& – &&
(see figure). These moieties have good
&
functional compatibility providing high-
performance energetic materials while
retaining molecular stability.
N-Diazo-Bridged Nitroazoles:
Catenated Nitrogen-Atom Chains
Compatible with Nitro Functionalities
Chem. Eur. J. 2014, 20, 1 – 7
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7
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
&
&
These are not the final page numbers! ÞÞ