Insensitive nitrogen-rich energetic compounds based on the 5,5'-dinitro-3,3'-bi-1,2,4-triazol-2-ide anion

Article abstract of DOI:10.1002/ejic.201200221

In this contribution the improvements achieved in the synthesis of the thermally stable energetic heterocycle 5,5'-dinitro-2H,2'H-3,3'-bi-1,2,4- triazole (DNBT) are described. The main goal was the synthesis of at least equally stable but more powerful energetic compounds based on the DNBT ^2- anion in combination with nitrogen-rich cations. A complete structural and spectroscopic characterization, including IR, Raman, and multinuclear NMR analyses of the uncharged compound is presented. In addition, X-ray crystallographic measurements on DNBT revealed a very high density of 1.903 g cm^-3. To increase both performance and stability, highly nitrogen-rich salts of DNBT formed from ammonium, hydroxyammonium, hydrazinium, guanidinium, aminoguanidinium and triaminoguanidinium cations were prepared and fully characterized by vibrational and multinuclear NMR spectroscopy, DSC, and X-ray diffraction measurements. The standard enthalpies of formation were calculated for selected compounds at the CBS-4M level of theory and the detonation parameters were calculated by using the EXPLO5.5 program. In addition, the impact as well as friction sensitivities and sensitivity against electrostatic discharge were determined. The main goal was to synthesize high thermally stable and powerful energetic compounds based on the DNBT^2- anion in combination with nitrogen-rich cations. A complete structural and spectroscopic characterization of all compounds by IR, Raman, and NMR spectroscopy is presented. The compounds exhibit low sensitivities, high positive heats of formation, and excellent detonation parameters. Copyright

Full text of DOI:10.1002/ejic.201200221

FULL PAPER
DOI: 10.1002/ejic.201200221
Insensitive Nitrogen-Rich Energetic Compounds Based on the 5,5Ј-Dinitro-3,3Ј-
bi-1,2,4-triazol-2-ide Anion
[a]
[a]
[a]
Alexander A. Dippold, Thomas M. Klapötke,* and Nils Winter
Keywords: Nitrogen heterocycles / Energetic materials / Explosives / Thermodynamics
In this contribution the improvements achieved in the syn-
thesis of the thermally stable energetic heterocycle 5,5Ј-dini-
tro-2H,2ЈH-3,3Ј-bi-1,2,4-triazole (DNBT) are described. The
main goal was the synthesis of at least equally stable but
more powerful energetic compounds based on the DNBT2
anion in combination with nitrogen-rich cations. A complete
structural and spectroscopic characterization, including IR,
Raman, and multinuclear NMR analyses of the uncharged
compound is presented. In addition, X-ray crystallographic
measurements on DNBT revealed a very high density of
highly nitrogen-rich salts of DNBT formed from ammonium,
hydroxyammonium, hydrazinium, guanidinium, aminoguan-
idinium and triaminoguanidinium cations were prepared and
fully characterized by vibrational and multinuclear NMR
spectroscopy, DSC, and X-ray diffraction measurements. The
standard enthalpies of formation were calculated for selected
compounds at the CBS-4M level of theory and the detonation
parameters were calculated by using the EXPLO5.5 pro-
gram. In addition, the impact as well as friction sensitivities
and sensitivity against electrostatic discharge were deter-
mined.
–
–3
1.903 gcm . To increase both performance and stability,
Introduction
catenated nitrogen atoms in one chain, which generally
makes them more stable to external stimuli. Many energetic
compounds that combine the triazole backbone with ener-
getic moieties such as nitro groups have been synthesized
The synthesis of energetic materials has attracted interest
worldwide over the last decade.[1] Nitrogen-rich com-
pounds, which mainly generate environmentally friendly
molecular nitrogen as an end-product of propulsion or ex-
over the last few decades. Examples of such molecules are
[6]
5
-amino-3-nitro-1,2,4-triazole (ANTA),
3-nitro-5-triaz-
plosion, have been the focus of research into energetic mate-
[7]
olone (NTO), and azo-bridged compounds like 5,5Ј-dini-
tro-3,3Ј-azo-1,2,4-triazole (DNAT). The thermal stabili-
rials across the globe.[
1f,2]
Modern heterocyclic energetic
[8]
compounds derive their energy not only from the oxidation
of their backbone but also from ring or cage strain. Owing
to the high positive heats of formation resulting from the
ties of these materials are remarkably high with decomposi-
tion taking place well above 200 °C and they have low sensi-
tivity values. In particular, the anionic species with nitro-
gen-rich cations show excellent properties as future high ex-
[3]
large number of N–N and C–N bonds and their high level
of environmental compatibility, we have studied these com-
pounds over the last couple of years with growing interest.
Azole-based compounds are a prominent family of novel
energetic materials because they are generally highly endo-
thermic with high densities and low sensitivities towards ex-
ternal stimuli. In particular, triazoles show a perfect balance
between the thermal stability and high positive heat of for-
mation required for applications as prospective high energy
density material (HEDM). Even though the heats of forma-
[9]
plosives. In general, the deprotonation of triazole species
positively influences their thermal stability as well as their
sensitivity. In addition, the nitrogen content and perform-
ance are increased by the introduction of nitrogen-rich cat-
ions.
5,5Ј-Dinitro-2H,2ЈH-3,3Ј-bi-1,2,4-triazole as well as its
ammonium and guanidinium salts have been described in
the literature previously, but they have only been charac-
[10]
[11]
terized by UV absorption
and IR spectroscopy
–1 [4]
tion are larger for tetrazoles (Δ H° = +237.2 kJmol ) as
f
(
DNBT) or investigated for use in gas-generating propel-
–
1 [5a]
well as 1,2,3-triazoles (Δ H° = +272 kJmol ),
1,2,4-tri-
are better suited to the
development of energetic materials because they have less
[12]
f
lants (ammonium and guanidinium salts).
The com-
–
1 [5b]
azoles (Δ H° = +109 kJmol )
f
pounds presented in this contribution have not previously
been characterized structurally or in terms of their energetic
properties.
The focus of this study was on the full structural and
spectroscopic characterization of the title compound 5,5Ј-
dinitro-2H,2ЈH-3,3Ј-bi-1,2,4-triazole as well as the forma-
tion and complete characterization of nitrogen-rich salts
formed with ammonium, hydrazinium, hydroxylammo-
[
a] Department of Chemistry, Ludwig-Maximilians Universität
München,
Butenandtstr. 5–13, Haus D, 81377 München, Germany
Fax: +49-89-2180-77492
E-mail: tmk@cup.uni-muenchen.de
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201200221.
3474
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Eur. J. Inorg. Chem. 2012, 3474–3484

Nitrogen-Rich Energetic Compounds
nium, guanidinium, aminoguanidinium, and triaminoguan- of DNBT and the low solubility of compounds 3a–f in eth-
idinium as counterions. The potential application of the anol, all ionic compounds could be isolated in excellent
synthesized compounds as energetic materials will be yields and with high purity.
studied and evaluated by using the experimentally obtained All the energetic compounds were fully characterized by
values for thermal decomposition as well as the sensitivity IR, Raman, and multinuclear NMR spectroscopy, mass
data and the calculated performance characteristics.
spectrometry, and differential scanning calorimetry (DSC).
Selected compounds were additionally characterized by
low-temperature single-crystal X-ray spectroscopy.
Results and Discussion
Synthesis
The starting material 5,5Ј-diamino-1H,1ЈH-3,3Ј-bi-1,2,4-
triazole (DABT, 1) was first synthesized in a moderate yield
of 56% by Shreve and Charlesworth using oxalic acid and
Molecular Structures
Single-crystal X-ray diffraction studies were undertaken
for compounds 2, 3a, 3c, 3e, and 3f. All these compounds
were recrystallized from water as colorless plates or blocks.
Selected crystallographic data for all the compounds are
compiled in Table S1 in the Supporting Information.
During the course of this study we were only able to ob-
tain water-free crystal structures of compound 2 and the
nitrogen-rich salts 3c and 3f. In the other cases, even though
we used different solvents and crystallization methods, crys-
tals too small for measurement (3b,d) or structures includ-
ing crystal water (3a,e) were obtained. Selected bond
lengths, bond angles, and torsion angles of compounds 2,
aminoguanidine hydrochloride in water.[
13]
We have devel-
oped a straightforward synthetic procedure yielding DABT
as a pure compound in a yield of up to 70%. The modified
procedure starts by reacting oxalic acid with aminoguanid-
inium bicarbonate in concentrated hydrochloric acid at
70 °C followed by isolation of the intermediate product by
filtration. While heating under reflux in basic media, the
molecule undergoes cyclization, which leads to the forma-
tion of DABT (Scheme 1).
3a, 3c, 3e, and 3f are compiled in Table S2 in the Supporting
Information.
Detailed examination of the crystal structure of the un-
charged compound showed no difference between the 1,2,4-
[
8,9b,15]
triazole system and other triazole ring systems.
The
bond lengths in the triazole ring in the molecular structure
of 2 all lie between the lengths of formal C–N and N–N
single and double bonds (C–N: 1.47, 1.22 Å; N–N: 1.48,
[
16]
1.20 Å).
5,5Ј-Dinitro-2H,2ЈH-3,3Ј-bi-1,2,4-triazole (2)
Scheme 1. Synthesis of DNBT (2).
crystallizes in the monoclinic space group P2 /n with a cell
1
DABT was oxidized by the well-known Sandmeyer reac-
tion by diazotization in sulfuric acid and subsequent reac-
tion with sodium nitrite.[ The formation of 5,5Ј-dinitro-
3
volume of 394.73(8) Å and two molecular moieties in the
–3
unit cell. The calculated density at 173 K is 1.902 gcm
14]
and hence much higher than the density of the dihydrate
2
H,2ЈH-3,3Ј-bi-1,2,4-triazole (DNBT, 2) was first reported
–3 [15b]
(
1.764 gcm ).
As expected, the molecule shows a com-
[11]
by Russian scientists in a low yield of 31%. We were able
to optimize the process by adding a suspension of DABT
in 20% sulfuric acid to a solution of sodium nitrite in water
at 40 °C, which led to a remarkable increase in the yield to
pletely planar assembly with a torsion angle between the
nitro group and the triazole ring of 2.9(2)°. The formula
unit of 2 together with the atom labeling is presented in
Figure 1.
82%.
The formation of the nitrogen-rich salts 3a–f was
straightforward. An ethanolic solution of compound 2 was
prepared and 2 equiv. of the corresponding nitrogen-rich
bases were added (Scheme 2). Owing to the high solubility
Figure 1. Crystal structure of 2. Thermal ellipsoids are shown at
the 50% probability level. Symmetry operators: (i) –x, 1 – y, 2 – z.
The structure contains only one individual hydrogen
bond N1–H1···O1. The D–H···A angle at 171.9(2)° is close
to 180° and the D···A length is shorter than the sum of the
[16a]
van der Waals radii [r (O) + r (N) = 3.07 Å]
2
at
.902(2) Å (Figure 2, a). The nitrogen atoms of the triazole
ring do not participate as acceptor atoms in any hydrogen
w
w
Scheme 2. Synthesis of the nitrogen-rich salts of 2 with the corre-
sponding bases.
Eur. J. Inorg. Chem. 2012, 3474–3484
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3475

A. A. Dippold, T. M. Klapötke, N. Winter
FULL PAPER
Figure 2. a) Hydrogen-bonding scheme in the crystal structure of 2. b) Wave-like arrangement of the infinite rows in the crystal structure
of 2 (layer distance d = 2.96 Å). Thermal ellipsoids are drawn at the 50% probability level. Symmetry operators: (i) 1/2 + x, 1/2 – y, 1/2
+
z.
bond. As shown in Figure 2, the crystal structure of 3 con- structures obtained for compounds 3a and 3e are presented
sists of infinite zig-zag chains along the b axis at an angle in the Supporting Information.
of 60.5°. The layers are stacked above each other with a
Hydroxylammonium 5,5Ј-dinitro-3,3Ј-bi-1,2,4-triazol-2-
layer distance of d = 2.96 Å. The layers are connected by ide (3c) crystallizes in the monoclinic space group P2 /c
1
two short contacts: N2···N4(ii) and C1···O1(iii) [symmetry with two molecular moieties in the unit cell and a density
–3
operators: (ii) 3/2 – x, 1/2 + y, 1/2 – z; (iii) 3/2 – x, –1/2 + of 1.836 gcm . An illustration of the formula unit is shown
y, 1/2 – z]. Both contacts are shorter than the sum of the in Figure S2 in the Supporting Information. As shown in
van der Waals radii[
[
16a]
with N2···N4 being the shortest Figure 3, each DNBT anion within the crystal structure
2.922(2) Å] and C1···O1 being the longest [3.051(2) Å]. The is surrounded by six hydroxylammonium cations linked by
stacking of the layers is displayed in Figure 2 (b) together strong hydrogen bonds to the nitrogen atoms of the triazole
with the distance d between the layers. ring and the oxygen O2 of the nitro group (Table 1). It is
2–
In the case of the nitrogen-rich salts, only the crystal remarkable that all nitrogen atoms of the triazole ring act as
structures of compounds 3c and 3f will be discussed in de- acceptor atoms for hydrogen bonds, which is only possible
tail. Illustrations as well as crystallographic details of the because of the surrounding hydroxylammonium cations. All
Figure 3. Environment of the DNBT2– anion in the crystal structure of 3c, hydrogen bonds towards hydroxylammonium cations are
marked as dotted lines. Thermal ellipsoids are drawn at the 50% probability level. Symmetry operators: (i) 1 – x, 1 – y, –z; (ii) 1 – x,
1/2 + y, 1/2 – z; (iii) 1 + x, 1/2 – y, 1/2 + z; (iv) x, 1/2 – y, –1/2 + z; (v) –x, 1/2 + y, –1/2 – z.
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Eur. J. Inorg. Chem. 2012, 3474–3484

Nitrogen-Rich Energetic Compounds
three contacts are short with a D···A length of 2.706(2), one formula unit in the unit cell. The molecular structure
2.862(3), and 2.880(3) Å, but only the hydrogen bonds O3– together with the labeling scheme is presented in Figure 5.
H3···N1(i) and N5–H5a···N2 are strongly directed with D–
H···A angles of 172(3) and 173(3)°, respectively. In addition,
the oxygen atom O2 acts as an acceptor in the moderately
strong hydrogen bond N5–H5b···O2(ii), which has a D···A
length of 2.965(3) Å and a relatively small D–H···A angle
of 164(3)°. Owing to this strong network of hydrogen
bonds, with O1 being the only potential hydrogen-bond ac-
ceptor that does not participate in any short contact or
other electrostatic interaction, the compound shows a re-
–
3
markably high density of 1.836 gcm .
Table 1. Hydrogen bond lengths and angles in 3c.
D–H···A
d(D–H)
Å]
d(H···A)
[Å]
d(D–
H···A) [Å]
Є(D–H···A)
[
[°]
O3–H3···N1(i)
N5–H5a···N2
N5–H5c···N3(iv)
N5–H5b···O2(ii)
N5–H5c···O3(iii)
0.90(4)
1.00(4)
0.90(3)
0.92(3)
0.90(3)
1.81(4)
1.87(4)
2.04(3)
2.07(3)
2.55(3)
2.706(2)
2.862(3)
2.880(3)
2.965(3)
3.018(2)
172(3)
173(3)
157(3)
164(3)
113(2)
Figure 5. Crystal structure of 3f. Thermal ellipsoids are drawn at
the 50% probability level. Symmetry operators: (i) 1 – x, 1 – y, –z.
As expected for ionic compounds, the structure is con-
structed of strong hydrogen bonds between the cations and
anions. The structure-determining motive are the infinite
Symmetry operators: (i) x, 1/2 – y, 1/2 + z; (ii) –1 + x, 1/2 – y, –1/2 + z;
iii) 1 + x, y, z; (iv) 1 – x, –1/2 + y, 1/2 – z.
(
2–
rows of DNBT anions along the b axis. The layers of the
DNBT2– anions stack with a distance of 3.307 Å and are
The interaction of the DNBT2– anions with hydroxylam- connected through hydrogen bonds to the TAG molecules
monium cations leads to the formation of layers in the bc (Figure 6).
plane (Figure 4). The hydroxylammonium cations build up
All the hydrogen-bond lengths lie well within the sum of
rw(N) 3.07 Å,
with lengths of 3.0443(16)
is supported by a short contact O1···O2 with a contact dis- [N5–H5a···O1(i)], 3.0652(17) [N6–H6a···N3(ii)], and
tance of 3.030(3) Å. 2.9147(17) Å (N9–H9···N1), but they are not strongly di-
The triaminoguanidinium salt (3f) crystallizes in the tri- rected, with angles of 147.0(14), 158.3(14), and 143.4(15)°,
infinite rows along the a axis and the layers are connected the van der Waals radii [r (O)
+
=
w
16a]
[
by strong hydrogen bonds. This structure of stacked layers r (N) + r (N) = 3.20 Å]
w
w
¯
–3
clinic space group P1 with a density of 1.664 gcm and respectively (Table 2).
Figure 4. Hydrogen-bonding scheme in the crystal structure of 3c with layers forming in the bc plane. Thermal ellipsoids are drawn at
the 50% probability level. Symmetry operators: (i) 1 – x, 1 – y, –z; (ii) 1 – x, 1/2 + y, 1/2 – z; (iii) x, 1/2 – y, –1/2 + z.
Eur. J. Inorg. Chem. 2012, 3474–3484
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3477

A. A. Dippold, T. M. Klapötke, N. Winter
FULL PAPER
Figure 6. Hydrogen-bonding scheme in the crystal structure of 3f showing the connection of the infinite rows of DNBT anions by TAG
cations. Thermal ellipsoids are drawn at the 50% probability level. Symmetry operators: (i) 1 – x, 2 – y, 1 – z; (ii) x, y, 1 + z; (iii) 1 – x,
1
– y, –z; (iv) 1 – x, 1 – y, 1 – z; (v) x, 1 + y, z; (vi) x, –1 + y, –1 + z; (vii) 1 – x, 1 – y, –1 – z; (viii) x, y, –1 + z; (ix) 1 – x, 2 – y, –z.
Table 2. Hydrogen bond lengths and angles in 3f.
pound and can be found at 1410–1380 (IR) and 1407–
383 cm–1 (Raman). The combined stretching and defor-
mation modes as well as torsion modes for the triazole rings
are again observed between 1200 and 600 cm–1 for the ni-
trogen-rich salts.
1
D–H···A
d(D–H)
Å]
d(H···A)
[Å]
d(D–H···A) Є(D–H···A)
[
[Å]
[°]
N5–H5a···O1(i)
N6–H6a···N3(ii)
N9–H9···N1
0.851(16)
0.890(16)
0.800(15)
2.295(16)
2.221(16)
2.233(15)
3.0443(16)
3.0652(17)
2.9147(17)
147.0(14)
158.3(14)
143.4(15)
Multinuclear NMR Spectroscopy
Symmetry operators: (i) 1 – x, 2 – y, 1 – z; (ii) x, y, 1 + z.
All the compounds were investigated by H, 13C, and 14
1
N
NMR spectroscopy. In addition, 15N NMR spectra were
recorded for compounds 2 and 3e. The two signals of the
uncharged compounds 1 and 2 differ only slightly in the
Spectroscopic Data
Vibrational Spectroscopy
13
1
[8,9c]
C{ H} NMR spectra and are in the expected range.
IR and Raman spectra were recorded for all the com-
pounds and the frequencies assigned according to the litera-
One singlet arising from the bridging carbon atoms appears
at δ = 149.3 ppm for DABT (1) and at δ = 145.6 ppm for
DNBT (2). The oxidation of the amino group leads to a
downfield shift of the signal of the other carbon atoms from
[
17]
ture. The Raman spectrum of compound 1 is dominated
–1
by the deformation mode of the amino groups at 1579 cm .
The valence stretching mode of the N–H bond is observed
157.3 ppm for 1 to 162.7 ppm for 2. The protons in the
–
1
at 3116 (IR) and 3107 cm (Raman). After oxidation of the
amino groups, the deformation modes of the amine groups
disappear. Instead, the symmetric and asymmetric stretch-
ing modes of the nitro groups of compound 2 are observed.
The vibrational frequencies of the νas stretching mode of
the nitro groups are observed at 1551 (IR) and 1546 cm–1
triazole rings of DNBT can be observed at δ = 9.68 ppm.
14
1
In the N{ H} NMR spectra, the nitro groups of com-
pound 2 appear as a broad singlet at δ = –26 ppm. The
NMR signals of all energetic the compounds are summa-
rized in Table 3.
(
Raman), and the ν stretching modes are located at a lower
s
Table 3. NMR signals of compounds 2, 3a–f.
δ [ppm]
–
1
energy at 1410 (IR) and 1393 cm (Raman). The valence
stretching mode of the N–H bond can be observed at 3189
(
cyclic compound, many combined stretching, deformation,
and torsion stretching modes can be observed in the finger-
print region between 1200 and 600 cm .
–
1
DNBT2–[a]
C{ H}
IR) and 3191 cm (Raman). In addition, as for any hetero-
Cation14
1
3
1
14
1
1H
1
N{ H}
N{ H}
2
162.7, 145.6
165.5, 157.4
165.0, 156.5
165.1, 155.5
–26
–18
–22
–14
–
–
–
1 [17b]
3a
7.16
7.24
5.52
–359
–359
–
3
3
b
c
The nitrogen-rich salts of 2 also show absorption bands
–
1
in the region between 3100 and 3500 cm for the N–H val-
13
1
C{ H}
ence stretching modes of the cations (ammonium, hydrazin- 3d
165.2, 156.6
165.4, 157.1
165.6, 157.8
–23
–17
–16
7.57
7.60, 4.73
7.61, 4.56
158.2
157.8
159.0
3
e
f
ium, and guanidines). The νas stretching modes of the nitro
groups are shifted to higher energy compared with 2 and
3
–
1
are observed between 1582 and 1562 cm in the Raman [a] DNBT in the case of 2.
–
1
spectra and between 1521 and 1508 cm in the IR spectra,
respectively. The symmetric stretching modes of the nitro
groups are in the same range as for the uncharged com- pounds,
As described in previous publications on triazole com-
[
9b,18]
the deprotonation of DNBT with nitrogen-
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Eur. J. Inorg. Chem. 2012, 3474–3484

Nitrogen-Rich Energetic Compounds
rich bases shifts the signals in the 13C{ H} NMR spectra Theoretical Calculations, Performance Characteristics, and
1
downfield. The carbon atoms connecting the two triazole Stabilities
rings can be found in the range 155.5–157.8 ppm and the
All calculations of energies of formation were carried out
carbon atoms connected to the nitro groups are in the range
[
20]
by using the Gaussian G09W program package. Because
very detailed descriptions of the calculation process have
of 165.0–165.6 ppm. A trend in the shift of the nitro group
1
4
1
signal in the N{ H} NMR spectra could not be observed;
all the signals are found in the range of –18 to –23 ppm.
[
9c]
been published earlier
and can be found in specialized
[
1b]
books,
only a short summary of the computational
1
4
1
The N{ H} NMR spectra of 3a and 3b also show the
signal of the corresponding cation at δ = –359 ppm. The
methods will be given here. The enthalpies (H) and Gibbs
free energies (G) were calculated by using the complete basis
set method (CBS) of Petersson and co-workers to obtain
very accurate energies. In this contribution, we used the
modified CBS-4M method with M referring to the use of
minimal population localization, which is a reparametrized
version of the original CBS-4 computational method and
1
signals of all the nitrogen-rich cations in the H NMR
spectra are found in the expected range and have been
assigned on the basis of similar countercations of
[
9c]
triazolide anions.
Four well-resolved resonances for the four nitrogen
atoms of compounds 2 and 3f are observed in the 15
N
[
21]
also includes additional empirical calculations.
The en-
NMR spectra (Figure 7). In addition, two signals from the
triaminoguanidinium cation are observed for compound 3f.
The signals have been assigned by comparison with litera-
thalpies of formation for the gas-phase species were com-
puted by the atomization energy method using NIST[ val-
ues as standardized values for the standard heats of forma-
22]
[
17a,19]
ture values.
[
23]
tion (Δ H°) according to Equation (1).
f
f f
Δ H°(g,Molecule,298) = H(Molecule) – ΣH°(Atoms) + ΣΔ H°(Atoms,NIST) (1)
The solid-state enthalpies of formation for uncharged
compounds were estimated from the computational results
[
24]
using Troutons rule
[Equation (2), in which Tm is the
decomposition temperature].
ΔH
m
= Δ
f
H°(g,Molecule,298) – ΔHsub = Δ
f
H°(g,Molecule,298) –
–
1
–1
(
188 [Jmol K ]ϫT
m
)
(2)
The solid-state enthalpies of formation for the ionic com-
pounds were derived from the calculation of the corre-
sponding lattice energies (U ) and enthalpies (H ), calcu-
L
L
lated from the corresponding molecular volumes using the
[
25]
equations provided by Jenkins and co-workers. The mo-
lar standard enthalpies of formation determined for the so-
lid state (ΔH ) were used to calculate the solid-state ener-
m
gies of formation (ΔU ) according to Equation (3) with Δn
m
being the change in the number of moles of gaseous compo-
[
1b]
nents.
ΔU
m
= ΔH
m
– ΔnRT
(3)
The calculated standard energies of formation were used
to predict the detonation parameters with the program
[
26]
package EXPLO5.5. The program is based on the chemi-
cal equilibrium, steady-state model of detonation. It uses
the Becker–Kistiakowsky–Wilson equation of state (BKW
EOS) for gaseous detonation products together with the
Cowan–Fickett equation of state for solid carbon.[ The
equilibrium composition of the detonation products was
27]
Figure 7. 15N NMR spectra of 5,5Ј-dinitro-2H,2ЈH-3,3Ј-bi-1,2,4- calculated by using the modified free-energy minimization
triazole (2, top) and bis(triaminoguanidinium) 5,5Ј-dinitro-3,3Ј-bi- technique of White, Johnson, and Dantzig. The program
1
,2,4-triazol-2-ide (3e, bottom); the x axis represents the chemical
was designed to enable calculations of the detonation pa-
rameter at the Chapman–Jouguet point. The BKW equa-
tion (4) as implemented in the EXPLO5.5 program was
shift δ in ppm.
As expected, the nitrogen atoms N1, N2, and N4 are used with the BKW-G set of parameters (α, β, κ, θ) given
shifted to a lower field upon deprotonation. The largest ef- below Equation (4) in which X is the mol fraction of the
i
th
fect can be observed for the nitrogen atom N1, which is
found at δ = –55.3 ppm (δ = –156.1 ppm for 2).
i
gaseous detonation product and k is the molar co-vol-
ume of the i gaseous detonation product.
i
th
[26,27]
Eur. J. Inorg. Chem. 2012, 3474–3484
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3479

A. A. Dippold, T. M. Klapötke, N. Winter
FULL PAPER
(
4)
The results of the detonation runs, together with the cal-
culated energies of formation and the corresponding sensi-
tivities are compiled in Table 4.
Compound 2 shows a remarkably high thermal stability
up to 251 °C together with an insensitivity towards friction
and a moderate sensitivity towards impact (10 J). In com-
parison, 5,5Ј-dinitrimino-4,4Ј,5,5Ј-tetrahydro-1H,1ЈH-3,3Ј-
bi-1,2,4-triazole, recently reported by Shreeve and co-
workers, decomposes at 165 °C.[ The beneficial detona-
29]
–
1
tion parameters of DNBT with Vdet. = 8413 ms mainly
–1
stem from the high positive heat of formation (285 kJmol )
–
3
and the remarkably high density of 1.902 gcm (X-ray
measurement).
Because salts of energetic compounds tend to be more
stable than the uncharged compound, the nitrogen-rich
salts of DNBT are expected to show improved stability. The
decomposition temperatures of the ammonium (3a) and
aminoguanidinium (3e) salts are similar to that of the un-
charged compound, whereas the decomposition tempera-
ture of the guanidinium compound (3d) is higher (335 °C).
As shown in Figure 8, the decomposition temperature de-
creases along the series 3a–c with the ammonium salt 3a
showing the highest value of 252 °C and the hydroxylam-
monium salt 3c showing decomposition onset at 204 °C.
The same trend can be observed for the guanidinium deriv-
+)
DNBT2– (3a), (N
+
Figure 8. DSC plots of DNBT (2), (NH
4
2
+
2
H
5
)
2
-
-
2
+
2–
2–
+
3 2 2
DNBT (3b), (NH OH ) DNBT (3c), (G ) DNBT (3d), (AG )
+ 2–
2
2
–
atives 3e,f. The guanidinium salt 3d shows the highest de- DNBT (3e), and (TAG ) DNBT (3f). DSC plots were recorded
composition temperature with 335 °C, followed by the am-
2
–1
at a heating rate of 5 °Cmin .
minoguanidinium salt 3e at 253 °C, and the triaminoguanid-
inium salt 3f with a decomposition onset at 201 °C. Nearly and electrostatic discharge; only the hydrazinium salt is
all the compounds are insensitive towards friction, impact, moderately sensitive towards impact (15 J).
Table 4. Physicochemical properties of compounds 2 and 3a–f in comparison with hexogen (RDX).
2
3a
3b
3c
3d
3e
3f
RDX[o]
Formula
Molecular mass [gmol ]
C
226.1
10
360
0.1
49.45
–35.4
251
1.902
285
4
H
N
2 8
O
4
C
261.0
40
360
0.5
53.84
–49.2
252
1.7
109
522
4
H
N O
8 10 4
C
290.2
15
4
H
10
N
12
O
4
C
292.1
40
360
0.5
47.94
–49.2
204
1.836
189
4
H
N O
8 10 6
C
344.2
40
6
H
12
N
14
O
4
C
374.2
40
360
1.0
59.88
–64.1
253
1.7
355
6
H
14
N
16
O
4
6 18 20 4 3 6 6 6
C H N O C H N O
–1
434.3
40
360
222.1
7
120
–
[
a]
Impact sensitivity [J]
[b]
Friction sensitivity [N]
ESD test [J]
360
360
0.15
57.92
–49.6
237
1.7
412
0.75
56.96
–65.1
335
1.7
125
470
0.5
[
c]
N [%]
64.50
–62.6
201
1.664
828
37.8
–21.6
210
1.80
70
[d]
Ω [%]
[
e]
T
dec. [°C]
–
3 [f]
[n]
[n]
[n]
[n]
ρ [gcm ]
° [kJmol ]
–
1 [g]
Δ
f
H
m
–
1 [h]
Δ
f
U° [kJkg ]
EXPLO5 values, v. 5.05
1338
1530
617
1060
2027
417
–
1 [i]
–Δ
E
[K]
U° [kJkg ]
4888
3890
320
8413
642
4176
3121
248
7938
771
4914
3399
281
8400
798
4277
3111
299
8477
771
3419
2596
225
7699
760
3839
2782
248
8020
780
4538
3045
271
8365
811
6125
4236
349
8748
739
[
j]
T
E
[
k]
p
V
C–J [kbar]
–
1 [l]
det. [ms ]
–
1 [m]
Gas volume [Lkg ]
[
=
a] BAM drop hammer. [b] BAM friction tester. [c] Nitrogen content. [d] Oxygen balance. [e] Temperature of decomposition by DSC (β
5 °C, onset values). [f] Derived from the X-ray structure. [g] Molar enthalpy of formation. [h] Energy of formation. [i] Energy of
explosion. [j] Explosion temperature. [k] Detonation pressure. [l] Detonation velocity. [m] Assumes only gaseous products. [n] Density
values of 3a, 3b, 3d, and 3e were estimated based on additional pycnometer measurements and in relation to 3f and trends in the triazolide
[
9c]
[28]
salts (see ref. ). [o] Values based on ref. and the EXPLO5.5 database.
3480
www.eurjic.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 3474–3484

Nitrogen-Rich Energetic Compounds
The nitrogen-rich salts of DNBT all exhibit highly posi-
Energetic ionic compounds were synthesized from 2 by
tive heats and energies of formation in the range of the sim- using nitrogen-rich cations. All the reactions were carried
[29]
ilar ionic nitrimino compound. The detonation velocities out with the free bases or their corresponding carbonates.
were calculated to be in the range of 7699 (3d) to 8477 ms–1 The energetic ionic compounds 3a–f were characterized by
(3b). The best performances were calculated for the hydraz- the same techniques as used for the uncharged compounds.
inium salt (3b), which has a detonation velocity of Crystal structures were obtained for selected compounds
–
1
8
400 ms , and the hydroxylammonium salt 3c, which has and have been discussed in detail for compounds 2, 3c, and
–
1
a detonation velocity of 8477 ms and is around 4% lower 3f. All the ionic compounds have positive heats of forma-
than that of RDX.
tion in the range of 109 (3a) to 828 kJmol–1 (3f). The most
Because the focus of this study was the evaluation of po- interesting compounds with regard to energetic properties
tential replacements for commonly used secondary explos- are the hydroxylammonium (3c), triaminoguanidinium (3f),
ives, only three compounds show suitable values regarding and hydrazinium (3b) salts. All of these compounds exhibit
detonation parameters, sensitivities, and thermal stabilities. decomposition temperatures above 200 °C and performance
The best compounds for replacing RDX, taking into ac- values in the range of RDX [8477 ms–1 (3c), 8365 ms
count the performance values and sensitivities, would be the (3f)]. Worth mentioning is the guanidinium salt 3d, which
triaminoguanidinium and hydroxylammonium salts. Com- has a remarkably high decomposition temperature of
pound 3c displays the best performance with a calculated 335 °C and an insensitivity towards friction and impact.
–1
–
1
detonation velocity of 8477 ms , a detonation pressure of These compounds could find applications because they are
2
99 kbar, and a decomposition temperature of 204 °C. The easy to obtain, safe to handle, and show performance char-
triaminoguanidinium compound exhibits energetic proper- acteristics in the range of modern secondary explosives.[
ties in the same range with a detonation velocity of
2e]
–
1
8365 ms , a detonation pressure of 271 kbar, and a decom-
position temperature of 201 °C. In addition, both com- Experimental Section
pounds are, in contrast to RDX, insensitive towards friction
and impact.
Caution: Although all the nitroazoles are rather stable against ex-
ternal stimuli, proper safety precautions should be taken when
handling the dry materials. All the derivatives of DNBT are ener-
getic materials and tend to explode under the influence of heat,
The performance characteristics of the hydrazinium com-
pound 3b are even better than those of 3f with a calculated
–
1
detonation velocity of 8400 ms and a detonation pressure impact, or friction. Laboratory personnel and equipment should
of 281 kbar. Unfortunately, the compound is sensitive be properly grounded and protective equipment such as earthed
towards impact (15 J). Although the guanidinium salt 3d shoes, leather coat, Kevlar® gloves, ear protection, and face shield
–
1
is recommended.
shows lower performance values (Vdet. = 7699 ms , p
=
C–J
225 kbar) than 3c and 3f, it has an excellent decomposition
General: All chemical reagents and solvents were obtained from
temperature of 335 °C together with an insensitivity Sigma–Aldrich or Acros Organics (analytical grade) and were used
1
13
1
14
1
towards friction and impact and therefore it could be a po- as supplied without further purification. H, C{ H}, N{ H},
1
5
tential replacement for hexanitrostilbene (HNS). Although and N NMR spectra were recorded with a JEOL Eclipse 400
6
instrument in [D ]DMSO at 25 °C. The chemical shifts are given
not all the compounds perform better than RDX by calcu-
lations, they can probably find use in certain applications
in civilian use or as burn-rate modifiers in military applica-
tions.
1
13
14
15
relative to tetramethylsilane ( H, C) or nitromethane ( N, N)
as external standards and coupling constants are given in Hz. IR
spectra were recorded with a Perkin–Elmer Spectrum BX FT-IR
spectrometer equipped with an ATR unit at 25 °C. Transmittance
values are qualitatively described as “very strong” (vs), “strong”
(
s), “medium” (m), “weak” (w), and “very weak” (vw). Raman
Conclusions
spectra were recorded with a Bruker RAM II spectrometer
The starting material DABT (1) has been synthesized fol- equipped with a Nd:YAG laser (200 mW) operating at 1064 nm
lowing a modified literature procedure[ resulting in an in- and a reflection angle of 180°. The intensities are reported as per-
crease in the yield from 56 to 70%. Optimization of the centages of the most intense peak and are given in parentheses.
13]
Elemental analyses (CHNO) were performed with a Netzsch Simul-
reaction conditions for the oxidation of the amine to 5,5Ј-
dinitro-2H,2ЈH-3,3Ј-bi-1,2,4-triazole (DNBT, 2)[11] resulted
in an improvement in the yield from 31 to 82%. Compound
taneous Thermal Analyzer STA 429 instrument. Melting and de-
composition points were determined by differential scanning calo-
rimetry (Linseis PT 10 DSC, calibrated with standard pure indium
2
can therefore be considered as a low-cost starting material
–
1
and zinc). Measurements were made at a heating rate of 5 °Cmin
for new energetic materials and it has been fully charac-
terized by IR, Raman, and multinuclear NMR spec-
troscopy, mass spectrometry, and DSC. The uncharged
in closed aluminium sample pans with a 1 μm hole in the lid for
gas release to avoid an unsafe increase in pressure under a flow of
–1
nitrogen (20 mLmin ) with an empty identical aluminium sample
compound 2 shows thermal stability up to 251 °C together pan as reference.
with an insensitivity towards friction and a moderate sensi-
For the initial safety testing, the impact and friction sensitivities,
tivity towards impact (10 J). As a result of the calculated
and the electrostatic sensitivities were determined. The impact sen-
–
1
positive heat of formation (285 kJmol ), the detonation
[30]
sitivity tests were carried out according to STANAG 4489, modi-
parameters (Vdet. = 8413 ms ) are in the range of those of fied according to WIWEB instruction 4-5.1.02 using a BAM[32]
–
1
[31]
RDX.
drop hammer. The friction sensitivity tests were carried out accord-
3481
Eur. J. Inorg. Chem. 2012, 3474–3484
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org

A. A. Dippold, T. M. Klapötke, N. Winter
FULL PAPER
[33]
(m), 1183 (m), 1024 (m), 953 (s), 837 (s), 690 (w), 690 (w) cm–1.
Raman (200 mW): ν˜ = 3192 (3), 1641 (100), 1546 (28), 1519 (5),
1485 (75), 1468 (43), 1458 (95), 1413 (18), 1393 (97), 1365 (6), 1362
(6), 1345 (13), 1325 (27), 1306 (35), 1172 (58), 1062 (67), 1015 (31),
855 (4), 774 (8), 744 (5), 619 (4), 511 (4), 452 (5), 452 (5), 399
ing to STANAG 4487
and modified according to WIWEB in-
[
34]
[32]
struction 4-5.1.03 using the BAM friction tester. The electro-
static sensitivity tests were accomplished according to STANAG
35]
4
490[ using an electric spark testing device ESD 2010EN (OZM
Research) operating with the “Winspark 1.15 software package”.
–
1
–
(
9), 297 (9), 203 (6) cm . MS (FAB–): m/z = 225.1 [C
(226.11): calcd. C 21.25, H 0.89, N 49.56; found C
1.44, H 0.95, N 49.19. Sensitivities (grain size: Ͻ100 μm): friction:
4 8 4
HN O ] .
Crystallographic Measurements: Single-crystal X-ray diffraction
data for 2, 3a, 3e, and 3f were collected with an Oxford Xcalibur3
diffractometer equipped with a Spellman generator (voltage 50 kV,
current 40 mA) and a KappaCCD detector. Data collection was
4 2 8 4
C H N O
2
3
2
–
1
60 N, impact: 10 J, ESD: 0.1 J; DSC (onset, 5 °Cmin ): TDec.
=
51 °C.
[36]
undertaken by using the CrysAlis CCD software
and the data
reduction with the CrysAlis Red software.[ Crystals of compound
c were investigated with a Bruker Nonius–Kappa CCD dif-
37]
Ammonium 5,5Ј-Dinitro-3,3Ј-bi-1,2,4-triazol-2-ide (3a): 5,5Ј-Dini-
tro-2H,2ЈH-3,3Ј-bi-1,2,4-triazole (2; 250 mg, 1.1 mmol) was dis-
solved in ethanol (50 mL). Ammonia was passed through the solu-
tion for 5 min. Collection of the precipitate by filtration afforded
3
fractometer equipped with a rotating molybdenum anode and
Montel-graded multilayered X-ray optics. The structures were
[
38]
[39]
solved with Sir-92 or SHELXS-97 and refined with SHELXL-
ammonium 5,5Ј-dinitro-3,3Ј-bi-1,2,4-triazol-2-ide (3a; 374 mg,
[
40]
[41]
9
7
implemented in the program package WinGX and finally
1
1
.0 mmol, 91%) as a yellow solid. H NMR ([D
6
]DMSO): δ = 7.16
]DMSO): δ = 165.4, 159.1
]DMSO): δ = –18 (NO ),
]DMSO): δ = –20.0 (N4), –58.6
[42]
checked by using Platon.
CCDC-864398 (for 2), -864400 (for 3a), -864399 (for 3c), -864397
for 3e), and -864401 (for 3f) contains the supplementary crystallo-
+
13
(s, 8 H, NH
4
) ppm. C NMR ([D
6
+
14
(
–
(
(
1
1
CH
359 (NH
N1), –59.2 (N2), –147.3 (N3), –358.5 (NH
m), 2999 (m), 2890 (m), 2852 (m), 2786 (m), 1704 (w), 1671 (m),
7
N
4
), 157.1 ppm. N NMR ([D
6
2
+
) ppm. 15N NMR ([D
4
6
(
+
4
) ppm. IR: ν˜ = 3265
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
521 (s), 1457 (s), 1438 (s), 1408 (s), 1390 (vs), 1306 (s), 1244 (s),
–
1
090 (s), 1036 (m), 984 (m), 841 (s), 714 (m), 661 (m) cm . Raman
5,5Ј-Diamino-1H,1ЈH-3,3Ј-bi-1,2,4-triazole (DABT, 1): According
(
1
200 mW): ν˜ = 1572 (58), 1555 (7), 1541 (1), 1523 (7), 1480 (10),
472 (24), 1427 (3), 1405 (39), 1399 (51), 1352 (45), 1314 (1), 1300
[13]
to a modified literature procedure,
hydrochloric acid (60 mL)
was added to a stirred mixture of oxalic acid (20.0 g, 159 mmol)
and aminoguanidinium bicarbonate (45.4 g, 332 mmol). The reac-
tion mixture was stirred at 70 °C for 1 h and the precipitate was
collected by filtration. The colorless solid was dissolved in water
(
(
3), 1109 (76), 1101 (100), 1072 (6), 1032 (9), 850 (13), 779 (2), 765
2), 521 (1), 472 (2), 420 (2), 298 (2), 298 (2), 206 (2) cm .
–1
4 8 10 4
C H N O (260.17): calcd. C 18.47, H 3.10, N 53.84; found C
+
1
(
8.79, H 3.04, N 53.28. MS (FAB+): m/z = 18 [NH
FAB–): m/z = 225.1 [C HN O
4 8 4
4
] . MS
] . Sensitivities (grain size:
Ͻ100 μm): friction: 360 N, impact: 40 J, ESD: 0.5 J; DSC (onset,
(240 mL), which was made alkaline with sodium hydroxide to pH
–
=
14. The reaction mixture was heated at reflux for 1 h and sub-
sequently acidified with acetic acid to pH = 4. The resulting pre-
cipitate was collected by filtration, washed with water (ca. 200 mL),
–1
5
°Cmin ): Tdec. = 252 °C.
Hydrazinium 5,5Ј-Dinitro-3,3Ј-bi-1,2,4-triazol-2-ide (3b): 5,5Ј-Dini-
tro-2H,2ЈH-3,3Ј-bi-1,2,4-triazole (2; 250 mg, 1.1 mmol) was dis-
solved in ethanol (50 mL) and hydrazine hydrate (0.11 mL,
and dried in air to yield 5,5Ј-diamino-1H,1ЈH-3,3Ј-bi-1,2,4-triazole
1
(
1; 18.6 g, 112 mmol, 70%) as a colorless solid. H NMR ([D
6
]-
) ppm. 1 C NMR ([D
3
DMSO): δ = 6.46 (s, 2 H, NH
2
6
]DMSO): δ =
2.2 mmol) was then added. Collection of the precipitate by fil-
1
1
1
57.3, 149.3 ppm. IR: ν˜ = 3325 (m), 3116 (m), 2863 (m), 2784 (m),
tration afforded hydrazinium 5,5Ј-dinitro-3,3Ј-bi-1,2,4-triazol-2-ide
706 (s), 1668 (s), 1654 (s), 1618 (m), 1606 (m), 1484 (m), 1457 (m),
267 (m), 1104 (vs), 1061 (s), 987 (w), 956 (w), 769 (w), 721
1
(
6
3b; 263 mg, 0.9 mmol, 83%) as a yellow solid. H NMR ([D ]-
+
13
–1
DMSO): δ = 7.24 (s, N H ) ppm. C NMR ([D ]DMSO): δ =
(
1
(
(
s) cm . Raman (200 mW): ν˜ = 1636 (62), 1614 (100), 1591 (67),
575 (57), 1495 (13), 1439 (21), 1432 (21), 1361 (9), 1152 (24), 1143
23), 1059 (23), 1042 (34), 1022 (22), 980 (27), 772 (18), 554 (7), 413
2
5
6
1
65.0, 156.5 ppm. 14N NMR ([D
6
2
]DMSO): δ = –22 (NO ), –359
) ppm. IR: ν˜ = 3346 (w), 3258 (w), 2648 (m), 1642 (w), 1586
+
(
N
2
H
5
–1
+
(w), 1509 (s), 1455 (vs), 1392 (vs), 1306 (s), 1263 (s), 1135 (m), 1110
11), 328 (12), 249 (16) cm . MS (DEI+): m/z = 166.1 [C
10 (194.16): calcd. C 28.92, H 3.64, N 67.44; found C 28.72,
H 3.58, N 66.11.
4 7 8
H N ] .
(
(
(
s), 1104 (s), 1043 (m), 990 (m), 968 (s), 836 (vs), 709 (m), 652
m) cm . Raman (200 mW): ν˜ = 1575 (30), 1554 (3), 1525 (4), 1516
5), 1485 (16), 1400 (61), 1355 (44), 1305 (4), 1113 (100), 1032 (6),
4 6
C H N
–
1
5,5Ј-Dinitro-2H,2ЈH-3,3Ј-bi-1,2,4-triazole (DNBT, 2): A solution of
5,5Ј-diamino-1H,1ЈH-3,3Ј-bi-1,2,4-triazole (1; 11.9 g, 72 mmol) in
20% sulfuric acid (140 mL) was added dropwise to a solution of
9
70 (2), 845 (12), 778 (2), 765 (3), 473 (2), 408 (2), 293 (1), 210
–1
(
4 10 12 4
4) cm . C H N O (290.20): calcd. C 16.56, H 3.47, N 57.92;
found C 16.89, H 3.44, N 57.28. Sensitivities (grain size: Ͻ100 μm):
sodium nitrite (10 equiv., 98.8 g, 1.4 mol) in water (140 mL) at
0 °C. The mixture was stirred at 50 °C for 1 h. After cooling to
room temperature the mixture was acidified with sulfuric acid
20%) until no evolution of nitrogen dioxide could be observed.
–1
friction: 360 N, impact: 15 J, ESD: 0.15 J; DSC (onset, 5 °Cmin ):
4
Tdec. = 237 °C.
(
Hydroxylammonium 5,5Ј-Dinitro-3,3Ј-bi-1,2,4-triazol-2-ide (3c):
5,5Ј-Dinitro-2H,2ЈH-3,3Ј-bi-1,2,4-triazole (2; 250 mg, 1.1 mmol)
was dissolved in ethanol (50 mL) and hydroxylamine (50% in H O,
2
145 mg, 2.2 mmol) was then added. The mixture was heated at re-
flux for 30 min and allowed to cool to room temperature. Collec-
tion of the precipitate by filtration afforded hydroxylammonium
The precipitate was collected by filtration and dissolved in boiling
water. The hot solution was filtered and allowed to cool to room
temperature. Collection of the pale-green precipitate afforded 5,5Ј-
dinitro-2H,2ЈH-3,3Ј-bi-1,2,4-triazole dihydrate (15.5 g, 59 mmol,
1
8
2%) as a crystalline solid. H NMR ([D
6
]DMSO): δ = 9.68 (s, 2
H, HTriazole) ppm. 13C NMR ([D
1
]DMSO): δ = 162.7, 145.6 ppm.
5,5Ј-dinitro-3,3Ј-bi-1,2,4-triazol-2-ide (3c; 273 mg, 0.9 mmol, 93%)
6
4N NMR ([D
]DMSO): δ = –26 (NO
) ppm. N NMR ([D
15
]- as
NH
a
yellow solid.
1
H
NMR ([D
6
2
6
6
]DMSO): δ = 5.52 (s,
+
13
DMSO): δ = –27.8 (N4), –88.8 (N2), –141.7 (N3), –156.1
3
OH ) ppm. C NMR ([D
N NMR ([D ]DMSO): δ = –14 (NO
w), 2670 (m), 2621 (m), 2574 (m), 2530 (m), 2488 (m), 2419 (m), DMSO): δ = –22.5 (N4), –64.0 (N1), –75.3 (N2), –155.8 (N3),
6
]DMSO): δ = 165.1, 155.5 ppm.
1
4
15
(N1) ppm. IR: ν˜ = 3599 (m), 3499 (m), 3052 (w), 2849 (w), 2747
6
2 6
) ppm. N NMR ([D ]-
(
+
1844 (w), 1609 (m), 1532 (vs), 1466 (w), 1416 (vs), 1314 (vs), 1245
4
–296.9 (NH OH ) ppm. IR: ν˜ = 3174 (w), 2915 (w), 2668 (w), 2510
3482
www.eurjic.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 3474–3484

Nitrogen-Rich Energetic Compounds
(
1
w), 1614 (w), 1537 (w), 1508 (m), 1483 (w), 1473 (w), 1454 (s),
401 (vs), 1310 (s), 1266 (m), 1248 (m), 1218 (w), 1119 (s), 1050 (NO
(CH
9
2
N
6
+), 157.8 ppm. 14N NMR ([D
6
]DMSO):
δ = –16
1
5
) ppm. N NMR ([D ]DMSO): δ = –19.4 (N4), –55.3 (N1),
6
+
+
(
(
1
w), 998 (m), 843 (s), 801 (m), 766 (w), 710 (w), 656 (w), 656 –56.3 (N2), –145.7 (N3), –289.4 (CH
w) cm . Raman (200 mW): ν˜ = 1582 (37), 1526 (5), 1480 (14), NH
408 (58), 1363 (43), 1311 (2), 1117 (100), 1041 (5), 1003 (3), 851
9
N
6
, NH), –329.8 (CH
9 6
N ,
–1
2
) ppm. IR: ν˜ = 3343 (m), 3308 (s), 3184 (m), 1671 (vs), 1585
(m), 1520 (s), 1446 (s), 1380 (s), 1347 (m), 1295 (s), 1236 (s), 1194
(m), 1132 (s), 1088 (s), 1034 (s), 978 (vs), 962 (s), 838 (s), 739 (w),
714 (m) cm . Raman (200 mW): ν˜ = 1573 (10), 1563 (49), 1555
–
1
+
(
(
7) cm . MS (FAB+): m/z = 126.1 [Matrix + NH
3
O] . MS
–
–1
FAB–): m/z = 224.9 [C
4
HN
8
O
4
] . C
4
H
8
N
10
O
6
(292.17): calcd. C
16.44, H 2.76, N 47.94; found C 17.03, H 2.74, N 47.90. Sensitivi- (31), 1542 (4), 1514 (16), 1461 (26), 1384 (67), 1340 (41), 1293 (4),
ties (grain size: Ͻ100 μm): friction: 360 N, impact: 40 J, ESD: 0.5 J;
DSC (onset, 5 °Cmin ): Tdec. = 204 °C.
1083 (100), 1018 (6), 990 (2), 894 (2), 841 (2), 765 (2), 464 (3), 412
–1
–1
+
(2) cm . MS (FAB+): m/z = 105.1 [CH
9
N
6
] . MS (FAB–): m/z =
–
2
6
25.1 [C
4
HN
8
O
4
] .C
6
H
18
N
20
O
4
(434.34): calcd. C 16.59, H 4.18, N
Guanidinium 5,5Ј-Dinitro-3,3Ј-bi-1,2,4-triazol-2-ide (3d): 5,5Ј-Dini-
tro-2H,2ЈH-3,3Ј-bi-1,2,4-triazole (2; 250 mg, 1.1 mmol) was dis-
solved in ethanol (50 mL) and guanidinium carbonate (198 mg,
4.50; found C 17.58, H 3.98, N 63.30. Sensitivities (grain size:
Ͻ100 μm): friction: 360 N, impact: 40 J, ESD: 0.5 J; DSC (onset,
–1
5
°Cmin ): Tdec. = 201 °C.
1
3
.1 mmol) was then added. The mixture was heated at reflux for
0 min and the precipitate was collected by filtration to afford
Supporting Information (see footnote on the first page of this arti-
cle): Additional crystallographic data and parameters as well as
selected bond lengths, bond angles and torsion angles of com-
pounds 2 and 3a–f.
guanidinium 5,5Ј-dinitro-3,3Ј-bi-1,2,4-triazol-2-ide (3d; 331 mg,
1
1
.0 mmol, 87%) as a yellow solid. H NMR ([D
6
]DMSO): δ = 7.57
]DMSO): δ = 165.2, 158.2
]DMSO): –23
+
13
(
(
(
(
(
(
s, 12 H, CH
CH
NO
6
N
3
) ppm. C NMR ([D
6
+
14
6
N
3
), 156.6 ppm.
N
NMR ([D
6
δ =
2
) ppm. IR: ν˜ = 3467 (m), 3357 (w), 3143 (m), 1663 (s), 1560
w), 1510 (s), 1447 (s), 1387 (vs), 1302 (s), 1246 (m), 1105 (s), 1036
w), 990 (w), 843 (s), 716 (m), 689 (w), 655 (w) cm . Raman
200 mW): ν˜ = 1568 (44), 1554 (8), 1540 (3), 1525 (5), 1516 (7),
Acknowledgments
–1
Financial support of this work by the Ludwig-Maximilians Univer-
sity (LMU) of Munich, the U. S. Army Research Laboratory
1
1
470 (25), 1401 (56), 1389 (43), 1348 (71), 1298 (4), 1099 (100),
088 (77), 1065 (14), 1060 (20), 1029 (12), 1008 (28), 849 (16), 778
(
ARL), the Armament Research, Development and Engineering
Center (ARDEC), the Strategic Environmental Research and De-
velopment Program (SERDP) and the Office of Naval Research
–1
(2), 764 (3), 536 (7), 472 (5), 419 (3), 207 (3) cm . MS (FAB+): m/z
+
–
=
6 3 4 8 4 6 12 14 4
60.1 [CH N ] . MS (FAB–): m/z = 225 [C HN O ] .C H N O
[ONR Global, title: “Synthesis and Characterization of New High
(344.25): calcd. C 20.93, H 3.51, N 56.96; found C 19.88, H 4.95,
Energy Dense Oxidizers (HEDO), NICOP Effort)] under contract
numbers W911NF-09-2-0018 (ARL), W911NF-09-1-0120 (AR-
DEC), W011NF-09-1-0056 (ARDEC) and 10 WPSEED01-002/W-
1765 (SERDP) is gratefully acknowledged. The authors acknow-
ledge collaborations with Dr. Mila Krupka (OZM Research, Czech
Republic) in the development of new testing and evaluation meth-
ods for energetic materials and with Dr. Muhamed Sucesca (Brod-
arski Institute, Croatia) in the development of new computational
codes to predict the detonation and propulsion parameters of novel
explosives. We are indebted to and thank Dr. Betsy M. Rice and
N 47.06. Sensitivities (grain size: Ͻ100 μm): friction: 360 N, im-
pact: 40 J, ESD: 0.75 J; DSC (onset, 5 °Cmin ): Tdec. = 335 °C.
–1
Aminoguanidinium 5,5Ј-Dinitro-3,3Ј-bi-1,2,4-triazol-2-ide (3e): 5,5Ј-
Dinitro-2H,2ЈH-3,3Ј-bi-1,2,4-triazole (2; 250 mg, 1.1 mmol) was
dissolved in ethanol (50 mL) and aminoguanidinium hydrogen
carbonate (299 mg, 2.2 mmol) was then added. The mixture was
heated at reflux for 30 min and allowed to cool to room tempera-
ture. Collection of the precipitate by filtration afforded amino-
guanidinium 5,5Ј-dinitro-3,3Ј-bi-1,2,4-triazol-2-ide (3e; 374 mg,
1
1
.0 mmol, 91%) as a yellow solid. H NMR ([D
6
]DMSO): δ = 9.38 Dr. Brad Forch (ARL, Aberdeen, Proving Ground, MD) and Mr.
+
+
+
(
s, 2 H, AG ), 7.60 (s, 4 H, CH
7
N
4
), 4.73 (s, 8 H, CH
7
N
4
) ppm. Gary Chen (ARDEC, Picatinny Arsenal, NJ) for many helpful and
), 157.1 ppm. inspired discussions and support of our work. We are also indebted
2
) ppm. IR: ν˜ = 3265 (m),
to and thank Stefan Huber for measuring all sensitivity values and
1
3
+
C NMR ([D
N NMR ([D
6
]DMSO): δ = 165.4, 159.1 (CH
]DMSO): δ = –17 (NO
7 4
N
14
6
1
5
2999 (m), 2890 (m), 2852 (m), 2786 (m), 1704 (w), 1671 (m), 1521
Dr. Burkhard Krumm for assistance in N NMR spectroscopy.
(
(
(
s), 1457 (s), 1438 (s), 1408 (s), 1390 (vs), 1306 (s), 1244 (s), 1090
The authors would like to thank one reviewer for stimulating criti-
s), 1036 (m), 984 (m), 841 (s), 714 (m), 661 (m) cm . Raman cism concerning thermodynamic approximations.
–1
200 mW): ν˜ = 1572 (58), 1555 (7), 1541 (1), 1523 (7), 1480 (10),
1
472 (24), 1427 (3), 1405 (39), 1399 (51), 1352 (45), 1314 (1), 1300
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Eur. J. Inorg. Chem. 2012, 3474–3484
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
3483

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Received: March 5, 2012
Published Online: June 19, 2012
3484
www.eurjic.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 3474–3484