The 1,4,5-triaminotetrazolium cation (CN7H6 +): A highly nitrogen-rich moiety

Article abstract of DOI:10.1002/ejic.201200964

The amination of 1,5-diamino-1,2,3,4-tetrazole with tosylhydroxylamine yielded 1,4,5-triaminotetrazolium tosylate. Metathesis reactions yielded energetic bromide, nitrate, and nitrotetrazolate 2-oxide salts. Owing to the exceedingly high nitrogen content

Full text of DOI:10.1002/ejic.201200964

FULL PAPER
DOI: 10.1002/ejic.201200964
+
The 1,4,5-Triaminotetrazolium Cation (CN7H6 ): A Highly Nitrogen-Rich
Moiety
Thomas M. Klapötke,*[a] Davin G. Piercey,[a] and Jörg Stierstorfer[a]
Dedicated to the memory of Professor Dr. Detlef Schröder
Keywords: Nitrogen heterocycles / Amination / Energetic materials / Structure elucidation
The amination of 1,5-diamino-1,2,3,4-tetrazole with tosyl-
hydroxylamine yielded 1,4,5-triaminotetrazolium tosylate.
Metathesis reactions yielded energetic bromide, nitrate, and
nitrotetrazolate 2-oxide salts. Owing to the exceedingly high
nitrogen content of the cation (Ͼ84% !), the calculated heats
of formation and the experimental explosive and thermal
sensitivities are exceedingly high. For the first time, the X-
ray structure of this energetic cation is reported, as are the
standard multinuclear NMR, infrared, and Raman spectro-
scopic data. Explosive performances (detonation velocity and
pressure) have also been calculated for a sample compound.
lecular nitrogen. In singly and doubly bonded nitrogen sys-
tems, this is especially true, where the more contiguous ni-
trogen atoms in the system leads to higher heats of forma-
tion and, as such, higher performances.[7,8]
Introduction
Many scientists are attracted to this field as a result of
the unique challenges encountered in synthesis and charac-
terization of these prospective replacements for currently
used energetic materials. Within the field of energetic mate-
rials, nitrogen-rich compounds are extensively looked at as
replacements for currently used energetics because they are
higher performing and are more environmentally friendly
alternatives.[1–5]
Traditional energetic materials including TNT (2,4,6-tri-
nitrotoluene) and RDX (1,3,5-trinitro1,3,5-triazinane) ob-
tain the majority of their energy content by oxidation of
their carbon backbones through the presence of an oxidizer
in the molecule. With new research in the development of
novel energetics, two new classes of explosive materials have
been introduced: those containing either ring or cage strain
(e.g., energetic cubanes) and those with high heats of forma-
tion that are nitrogen rich (e.g., tetrazoles and tetrazines).
These strategies have also been combined to make strained,
nitrogen-rich heterocycles a promising and well-investigated
area of research.[6–11]
Nitrogen-rich heterocycles, especially tetrazoles, have
been the backbones of various new explosive compounds,
as the carbon position can be easily tailored. This allows
the introduction of various substituents to create com-
pounds that span a range of sensitivities from highly sensi-
tive primary explosives to insensitive secondary explos-
ives.[11,12] However, the tailoring of substituents on the ni-
trogen atoms of tetrazole rings is far less investigated. Alk-
ylation reactions are well known;[13–15] however, the ad-
dition of carbon atoms often has negative effects on explos-
ive performance. In our recent work, we reported on a series
of N-aminated energetic tetrazoles that were the result of
aminating energetic anions with hydroxylamine-O-sulfonic
acid.[16] The N-amination of energetic anions gave neutral
N-amino species with very high performances, and in this
work, we extended this methodology to the amination of a
well-known neutral tetrazole species (1,5-diaminotetrazole)
to yield the first energetic tetrazolium cation containing
three amino groups on the same tetrazole ring.
Among the elements, nitrogen occupies a unique posi-
tion; the strong, short triple bond means that there is a
large energetic driving force towards the formation of mo-
The 1,4,5-triaminotetrazolium cation, at over 84% nitro-
gen, belongs to the unique class of compounds containing
over 80% nitrogen.[8,17,18] Beyond use in explosive materials,
compounds containing such high nitrogen contents are im-
portant in propellant formulations, as lower reaction tem-
peratures and higher N2/CO ratios in the combustion prod-
ucts result in lower erosivity. It has been shown that lower
[a] Department of Chemistry, Energetic Materials Research,
Ludwig-Maximilian University,
Butenandtstr. 5–13 (D), 81377 München, Germany
Fax: +49-89-2180-77492
E-mail: tmk@cup.uni-muenchen.de
Homepage: http://www.cup.uni-muenchen.de/ac/klapoetke/
5694
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Eur. J. Inorg. Chem. 2012, 5694–5700

The 1,4,5-Triaminotetrazolium Cation: A Highly Nitrogen-Rich Moiety
erosivity results from the presence of higher concentrations
of nitrogen in the combustion gasses of a propellant leading
to surface formation of iron nitride instead of iron carbide
on the inside of the barrel.[18]
In this work, we have aminated 1,5-diaminotetrazole
with O-tosylhydroxylamine to yield 1,4,5-triaminotetrazol-
ium tosylate. Through metathesis reactions, the bromide, ni-
trate, and nitrotetrazolate 2-oxide salts were all prepared.
The compounds were characterized by X-ray diffraction, in-
frared and Raman spectroscopy, multinuclear NMR spec-
troscopy, elemental analysis, and differential scanning calo-
rimetry (DSC). Computational calculations confirming the
high energetic performance were also performed.
Scheme 3. Metathesis reactions of the 1,4,5-triaminotetrazolium
cation.
Spectroscopy
Results and Discussion
Multinuclear NMR spectroscopy proved to be a useful
tool for the characterization of the energetic cation and its
salts. In the 1H NMR spectrum, the 1,4,5-triaminotetrazol-
ium cation shows two resonances. The first at δ ≈ 8.9 ppm
for the amino group attached to the carbon atom of the
tetrazole ring, and another at δ ≈ 6.9 ppm for the N-amino
groups, which is double the intensity of the previous reso-
nance. In the 13C NMR spectrum, a single peak for the lone
carbon atom is observed at δ = 147 ppm.
The IR and Raman spectra of all compounds were col-
lected and assigned by using frequency analysis from an
optimized structure (B3LYP/cc-pVDZ using Gaussian09
software[19]). All calculations were performed at the DFT
level of theory; the gradient-corrected hybrid three-param-
eter B3LYP[20,21] functional theory has been used with a
correlation consistent p-VDZ basis set.[22–25] The infrared
spectra of the triaminotetrazolium cation possesses five
strong intensity bands that are easily rendered to medium
or low intensity when paired with an anion with strong ab-
sorbances. As bromide salt 2 only has resonances resulting
from the triaminotetrazolium cation, this spectrum was
used extensively for comparison. The calculated spectrum
shows a strong absorbance at 922 cm–1 resulting from N–
NH2 wagging. In the spectrum of the bromide salt, this
peak is visible at 867 cm–1, and in nitrate salt 3, it appears
at 825 cm–1. In the spectra of tosylate 1 and nitrotetrazolate
2-oxide 4, the presence of other peaks in the area makes
assignment unclear. The next high-intensity band occurs at
1787 cm–1 in the calculated spectrum and arises from C–N
Synthesis
O-Tosylhydroxylamine is not stable in storage, so it was
prepared from ethyl O-p-tolylsulfonylacetohydroximate by
hydrolysis with 60% perchloric acid (Scheme 1) before each
reaction. After hydrolysis, it was then poured into ice water
and extracted with dichloromethane, and the dichlorometh-
ane solution was dried with sodium sulfate.[16] A solution
of O-tosylhydroxylamine (THA) was then added to an ace-
tonitrile solution/suspension of 1,5-diaminotetrazole. After
reaction for 3 d, the crude 1,4,5-triaminotetrazolium tosyl-
ate was obtained (Scheme 2).
Scheme 1. Synthesis of O-tosylhydroxylamine (THA) from ethyl-
O-p-tolylsulfonylacetohydroximate.
Scheme 2. Synthesis of triaminotetrazolium tosylate.
The as-prepared 1,4,5-triaminotetrazolium tosylate (1) stretching with symmetric C1–N1/C1–N4 ring deformation.
was then dissolved in a minimal amount of ethanol, con- In the observed spectra, this band occurs at 1722, 1715,
centrated hydrobromic acid was added, and 1,4,5-triamino- 1726, and 1717 cm–1 for compounds 1–4, respectively. The
tetrazolium bromide (2) was precipitated by the addition of remaining strong bands result from symmetric N–NH2,
diethyl ether. Through metathesis reactions with either sil- symmetric C–NH2, asymmetric N–NH2, and asymmetric
ver nitrate or silver nitrotetrazolate 2-oxide, 1,4,5-triaminot- C–NH2 N–H stretching at calculated wavenumbers of 3449,
etrazolium nitrate (3) and 1,4,5-triaminotetrazolium nitro- 3535, 3537, and 3670 cm–1, respectively. In the observed
tetrazolate 2-oxide (4) were obtained, respectively spectra, these all occur in the range from 3400 to 3000 cm–1
(Scheme 3). Crystals were grown of all salts, with the excep- and show a greater deviation between the experimental and
tion of 4, by diffusing ether into a methanolic solution of calculated values compared to the previous bands. The cal-
the salt. Compound 4 was unable to be crystallized despite culated Raman spectrum of the triaminotetrazolium cation
repeated attempts.
contains one very high-intensity peak at 779 cm–1 resulting
Eur. J. Inorg. Chem. 2012, 5694–5700
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T. M. Klapötke, D. G. Piercey, J. Stierstorfer
FULL PAPER
from tetrazole ring breathing. In the spectra of 2 and 3, this Table 2. Crystallographic bond lengths and angles of the 1,4,5-tri-
signal occurs at 789 and 791 cm–1, respectively. In the spec-
aminotetrazolium cations in the structures of 1 and 3.
tra of 1 and 4, the presence of multiple peaks in this region
1a
1b
3
precludes exact assignment.
A–B length [Å]
C1–N1
C1–N4
C1–N5
N1–N2
N2–N3
N3–N4
N1–N6
N4–N7
1.344(2)
1.332(2)
1.314(2)
1.376(2)
1.277(3)
1.376(2)
1.386(2)
1.384(2)
1.334(2)
1.339(2)
1.313(2)
1.376(2)
1.277(3)
1.375(2)
1.381(2)
1.392(2)
1.338(4)
1.342(3)
1.308(4)
1.381(3)
1.271(3)
1.374(3)
1.385(3)
1.374(3)
Single-Crystal X-ray Analysis
With the exception of nitrotetrazolate 2-oxide salt 4, all
compounds were characterized by X-ray crystallography.
Table 1 summarizes a selection of crystallographic data and
refinement details. Exact bond lengths and angles of the
1,4,5-triaminotetrazolium cations are given in Table 2. The
bond lengths and angles within the tetrazole moiety are
comparable to those in 1,5-diaminotetrazole,[26] with several
small changes. We will discuss the changes based on bond
lengths and angles from salt 1; however, the trend also
holds for salt 3. The tetrazole ring within 1,5-diaminotetra-
zole is not symmetric; C1–N1 is longer than C1–N4: 1.345
vs. 1.327 Å, respectively. After amination, these bond
lengths, while they become similar at 1.344 and 1.332 Å,
respectively, they do not become equivalent, leaving the
tetrazole ring slightly distorted. Concurrently, N2–N3 and
N3–N4 increase in length from 1.363 to 1.376 Å. Finally, of
note is that only the protons of the C1–NH2 are planar with
the ring, indicating electronic communication between the
π system of the ring and the p electrons on the N5 amino
group. The process of amination reduces electron density
within the tetrazole ring, easily explaining why the C1–N5
bond length decreases to 1.314 Å from the 1.334 Å seen in
1,5-diaminotetrazole. The N–NH2 bond lengths, N1–N6
and N4–N7, do not change appreciably from the N–NH2
bond length in 1,5-diaminotetrazole.
A–B–C angle [°]
C1–N1–N2
C1–N4–N3
C1–N1–N6
C1–N4–N7
N1–C1–N4
N5–C1–N1
N5–C1–N4
110.33(16)
110.85(16)
124.36(17)
123.82(17)
103.79(17)
128.60(19)
127.61(19)
110.30(17)
110.40(17)
124.23(17)
123.45(17)
104.14(17)
128.38(19)
127.47(19)
110.1(2)
110.5(2)
122.8(2)
124.1(2)
103.9(2)
127.4(2)
128.7(3)
Table 1. Crystallographic data and structure refinement details for
triaminotetrazolium salts.
1·0.5MeOH
3
Formula
FW [gmol–1]
Crystal system
Space Group
a [Å]
b [Å]
c [Å]
C17H30N14O7S2
606.67
CH6N8O3
320.23
orthorhombic
Pna21
7.7144(18)
17.605(4)
5.2393(13)
90
90
90
711.6(3)
4
1.663
triclinic
Figure 1. View of the asymmetric unit in the structure of
1·0.5MeOH. Ellipsoids are drawn at the 50% probability level.
¯
P1
6.5993(2)
13.6361(5)
15.9896(6)
90.705(3)
95.737(3)
98.577(3)
1415.12(9)
2
1.424
173
0.0549/0.0969
0.0381/0.0881
1.048
α [°]
β [°]
The crystal structure of 2 could not be determined suffi-
ciently due to a hard twinning problem. By using a twin
data reduction, two species could be detected and sepa-
rated. One of them[27] could be solved and refined to yield
a final wR2 value of 23.2%. However, it was not possible to
locate any electron density for the hydrogen atoms.
Salt 3 crystallizes in the non-centrosymmetric ortho-
rhombic space group Pna21 with four formula units in the
unit cell. The molecular moiety is shown in Figure 2. Al-
γ [°]
V [Å3]
Z
ρcalcd. [gcm–3]
T [K]
173
R1/wR2 (all data)
R1/wR2 (I Ͼ 2σ)
Sc
0.0440/0.0736
0.0360/0.0696
1.049
Salt 1·0.5MeOH crystallizes in the triclinic space group though an intensive hydrogen-bonding network is formed,
P1 with four formula units in the unit cell and a density of the density is only 1.663 gcm–3. This is quite low in com-
1.424 gcm–3. The asymmetric unit consists of two anion– parison to other tetrazolium compounds, especially the cor-
cation pairings and one methanol molecule that is shown responding 5-aminotetrazolium nitrate (1.847 gcm–3)[28]
¯
in Figure 1.
and 1,5-diaminotetrazolium nitrate (1.727 gcm–3).[29] Inter-
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Eur. J. Inorg. Chem. 2012, 5694–5700

The 1,4,5-Triaminotetrazolium Cation: A Highly Nitrogen-Rich Moiety
estingly, the density decreases by increasing the number of Table 3. CBS-4M results and gas-phase enthalpies.
amino groups connected to the tetrazolium ring nitrogen
atoms.
Formula
–H298
[a.u.]
ΔfH(g)
[kJmol–1]
1,4,5-TAT+ CH6N7
424.051319
2572.763437
280.080446
536.798772
1129.0
–239.5
–313.6
83.0
+
Br–
Br–
–
–
NO3
NO3
NTX–
CN5O3
–
2
3
4
CH6N7Br
CH6N8O3
C2H6N12O3
889.5[a]
815.4[a]
1212.0[a]
[a] Gas-phase enthalpies of formation of the ionic compounds are
taken as the respective sums of the non-interacting component ions.
These molar standard enthalpies of formation (ΔHm)
were used to calculate the molar solid-state energies of for-
mation (ΔUm) according to Equation (2) (Table 3).
Figure 2. Molecular unit of 3. Ellipsoids are drawn at the 50%
probability level.
ΔUm = ΔHm – ΔnRT
(2)
Hydrogen bonding takes place at all oxygen atoms of the
nitrate anion and all hydrogen atoms of the 1,4,5-triamino-
tetrazolium cations, which is indicated in Figure 3.
where Δn is the change of mol of gaseous components.
As it can be seen from Table 4, compounds 2–4 are
formed endothermically. The most positive value of
722.6 kJmol–1 is obtained for 4 as a result of its highly ener-
getic and endothermic anion. The calculation of the deto-
nation parameters was performed with the program EX-
PLO5.05[33] by using the X-ray density for 3 and a helium
gas pycnometer density for 4. The results for 3 and 4 in
comparison to those of RDX are gathered in Table 5.
Table 4. Calculation of the solid-state energies of formation (ΔfU°).
2
3
4
VM [nm3]
0.167
606.7
607.9
0.178
520.9
525.9
289.5
8.5
0.234[a]
484.5
489.5
722.6
10.5
UL [kJmol–1]
ΔHL [kJmol–1]
ΔfH°(s) [kJmol–1] 281.6
Δn
6.5
1518.4
ΔfU°(s) [kJkg–1]
1743.2
3040.6
Figure 3. The unit cell of 4, depicting the important hydrogen
bonds of the nitrate anion.
[a] The molecular volume of 4 was recalculated from the X-ray
structure of ammonium 5-nitrotetrazolate N-oxide[5] and a litera-
ture value for the nitrate anion.[29]
The detonation parameters of 3 and 4 are slightly lower
than those of RDX, which is due to their lower densities.
However, the detonation velocities (Vdet) of 8779 ms–1 (for
3) and 8872 ms–1 (for 4) are much higher than those of
TNT (Vdet = 7459 ms–1) and also PETN (pentaerythritol
tetranitrate) (Vdet = 8561 ms–1) calculated by using the
same approaches. With respect to a potential use as propel-
lant ingredients, 3 and 4 show very high values for the spe-
cific impulse (using 60 bar chamber pressure isobaric rocket
conditions) of 260 s (for 3) and 259 s (for 4).
Energetic Properties
Calculation of the heats of formation of compounds 2–4
was performed by using the atomization method based on
CBS-4M calculated gas-phase enthalpies and Equation (1)
described recently in detail.[5]
ΔfH°(g,M,298) = H(molecule,298) – ΣH°(atoms,298) + ΣΔfH°(atoms,298) (1)
In addition, the sensitivities towards shock, friction, and
electrostatic discharge were carried out for all compounds.
The results are depicted in Table 3. The gas-phase heat Generally, tosylate salt 1 was found to be the least sensitive
of formation [ΔfH°(g,M)] was converted into the solid-state with 10 J and 240 N friction and impact sensitivities,
heat of formation [ΔfH°(s)] (Table 3) by using the Jenkins respectively, classifying it as a “less sensitive”[36] energetic
and Glasser equations for the lattice energies and enthalp- material. For remaining compounds 2–4, all impact ener-
ies.[30] The gas-phase enthalpies of formation of Br– gies were 2 J or less and all friction sensitivities were below
–
(–239.5 kJmol–1) and NO3 (–313.6 kJmol–1) fit very well 10 N. Of interest is the very high sensitivities of bromide
to experimentally obtained values published in the literature salt 2, uncharacteristic for an energetic cation paired with
–
(Br– –233.9 kJmol–1)[31] and NO3 (–300.2 kJmol–1).[32]
a non-energetic anion; for example, triaminoguanidinium
Eur. J. Inorg. Chem. 2012, 5694–5700
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T. M. Klapötke, D. G. Piercey, J. Stierstorfer
FULL PAPER
Table 5. Energetic properties of 3 and 4 in comparison to those of
RDX.
Experimental Section
General Methods: All reagents and solvents were used as received
(Sigma–Aldrich, Fluka, Acros Organics) if not stated otherwise. O-
p-Tolylsulfonylacetohydroximate was prepared according to a lit-
erature procedure.[12] Melting and decomposition points were mea-
sured with a Linseis PT10 DSC by using heating rates of
5 °Cmin–1. 1H NMR and 13C NMR spectra were measured with a
JEOL instrument. All chemical shifts are quoted in ppm relative
to TMS (1H, 13C). Infrared spectra were measured with a Perkin–
Elmer FTIR Spektrum BXII instrument equipped with a Smith
Dura SampIIR II ATR-unit. Transmittance values are described as
strong (s), medium (m), and weak (w). Mass spectra were measured
with a JEOL MStation JMS 700 instrument. Raman spectra were
measured with a Perkin–Elmer Spektrum 2000R NIR FT-Raman
instrument equipped with a Nd:YAG laser (1064 nm). The inten-
sities are reported as percentages of the most intensive peak and
are given in parentheses. Elemental analyses were performed with
a Netsch STA 429 simultaneous thermal analyzer. Sensitivity data
were determined by using a BAM drophammer and a BAM fric-
tion tester. The electrostatic sensitivity tests were carried out by
using an Electric Spark Tester ESD 2010 EN (OZM Research) op-
erating with the “Winspark 1.15” software package.
3
4
RDX
Formula
CH6N8O3
178.11
2
C2H6N12O3
246.15
1
C3H6N6O6
222.12
7.5[34]
FW [gmol–1]
Impact sensitivity [J][a]
Friction sensitivity [N][b]
ESD-test [J][c]
N [%][d]
5
7
120[34]
0.050
62.91
–17.96
78
1.663
1743.2
0.100
68.28
–26.00
84
1.71
3040.6
0.2
37.84
Ω [%][e]
–21.61
210
Tdec [°C][f]
Density [gcm–3][g]
ΔfUo [kJkg–1][h]
EXPLO5.05 Values
–ΔExU°[kJkg–1][i]
Tdet [K][j]
1.858 (90 K)[35]
489.0
5745
4006
311
8779
876
5910
4221
326
8872
815
6190
4232
380
8983
734
PCJ [kbar][k]
Vdet [ms–1][l]
Vo [Lkg–1][m]
IS [s][n]
260
259
258
[a] Impact sensitivity [BAM drophammer (1 of 6)]. [b] Friction sen-
sitivity [BAM friction tester (1 of 6)]. [c] Electrostatic discharge de-
vice (OZM research). [d] Nitrogen content. [e] Oxygen balance
[Ω = (xO – 2yC – 1/2zH)M/1600]. [f] Decomposition temperature
from DSC (β = 5 °C). [g] From X-ray diffraction. [h] Calculated
energy of formation. [i] Energy of explosion. [j] Explosion tempera-
ture. [k] Detonation pressure. [l] Detonation velocity. [m] Volume of
detonation gases (assuming only gaseous products). [n] Specific im-
pulse using isobaric (60 bar) conditions.
CCDC-896690 (for 1·0.5MeOH) and -896691 (for 3) contain the
supplementary crystallographic 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.
CAUTION! The described compounds are energetic materials with
sensitivity to various stimuli. Although we encountered no issues in
the handling of these materials, proper protective measures (face
shield, ear protection, body armor, Kevlar gloves, and earthened
equipment) should be used at all times.
bromide is insensitive.[37] Bromide salt 2 is highly sensitive
towards mechanical stimuli (impact, friction), but with
15 mJ electrostatic sensitivity it is also capable of being ini-
tiated by a static charge created by the human body. All
these results indicate that the 1,4,5-triaminotetrazolium cat-
ion is far too sensitive towards mechanical and electrostatic
stimuli to find any practical use as an energetic material.
Finally, compounds 2–4 all decompose in the range from
102 to 78 °C. These thermal stabilities are too low for a
practical energetic material; however, it does provide insight
that there is a limit on the thermal stability as heats of for-
mation and associated nitrogen content increase.
1,4,5-Triaminotetrazolium Tosylate (1): Ethyl O-p-tolylsulfonyl-
acetohydroximate (3.5 g, 13.6 mmol) was slurried in 60% perchloric
acid (40 mL) and stirred for 2 h. The mixture was then poured into
ice water (500 mL) and once the ice had melted the solution was
extracted with dichloromethane (5ϫ50 mL). The dichloromethane
solutions were combined and dried with sodium sulfate. This was
then added to a solution of 1,5-diaminotetrazole (1.0 g, 9.99 mmol)
in acetonitrile (100 mL), and the mixture was stirred for 3 d. The
solution was then evaporated to yield the crude triaminotetrazol-
ium tosylate (2.74 g, 95%). IR: ν = 3348 (w), 3278 (m), 3186 (m),
˜
3047 (m), 2861 (w), 1722 (m), 1652 (w), 1625 (w), 1602 (w), 1496
(w), 1403 (w), 1340 (w), 1177 (s), 1123 (s), 1136 (m), 1010 (m), 898
(m), 821 (m), 793 (m), 712 (w), 682 (m) cm–1. Raman (1064 nm) =
3277 (4), 3190 (7), 3066 (49), 3032 (4), 2986 (5), 2924 (15), 2870
(4), 2739 (4), 2698 (4), 2575 (5), 1734 (4), 1599 (34), 1575 (4), 1524
(5), 1495 (3), 1456 (1), 1446 (3), 1391 (20), 1309 (4), 1212 (12), 1192
(20), 1128 (84), 1042 (39), 1015 (16), 902 (4), 802 (98), 687 (9), 638
(38), 616 (11), 555 (9), 492 (6), 400 (14), 367 (3), 348 (7), 314 (3),
296 (35), 230 (17) cm–1. 1H NMR (400 MHz, [D6]DMSO): δ = 8.95
Conclusions
The amination of 1,5-diaminotetrazole with O-tosyl-
hydroxylamine is an effective method of preparing the new
energetic 1,4,5-tetrazolium cation. Metathesis reactions al-
lowed easy preparation of the bromide, nitrate, and nitrotet-
razolate 2-oxide salts. The crystal structure of this unique
cation was determined for the first time, as were its spectral
properties. The energetic performances of the nitrate and
nitrotetrazolate 2-oxide salts were calculated, illustrating
3
(s, 2 H, C-NH2), 7.47 (d, JH,H = 8 Hz, 2 H, Ar C-H OTs-), 7.11
3
(d, JH,H = 8 Hz, 2 H, Ar C-H OTs-) 6.94 (s, 4 H, N-NH2), 2.28
(s, 3 H, CH3) ppm. 13C NMR (68 MHz, [D6]DMSO): δ = 147.1
(s, 1 C, CN7H6), 146.1, 138.3, 128.6, 126.0, 21.3 (tosylate carbon
atoms) ppm. MS (FAB+): m/z = 116.1 [CN7H6]. MS (FAB–): m/z
the ability of the triaminotetrazolium cation to form high- = 170.0 [C7H7SO3]. BAM impact: 10 J. BAM friction: 240 N.
performance energetic materials almost on par with RDX.
However, the major limitations of the triaminotetrazolium
1,4,5-Triaminotetrazolium Bromide (2): To a solution of triamino-
tetrazolium tosylate (0.25 g, 0.87 mmol) dissolved in a minimal
cation are its sensitivities; the mechanical, electrostatic, and
thermal sensitivities of this new energetic cation are all far
too low to be used in practical energetic materials.
amount of ethanol was added 47% hydrobromic acid (0.21 g). The
mixture was stirred for 5 min and then diethyl ether (50 mL) was
added, which resulted in the precipitation of triaminotetrazolium
5698
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© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 5694–5700

The 1,4,5-Triaminotetrazolium Cation: A Highly Nitrogen-Rich Moiety
bromide(0.15 g, 88%). DSC: 102 °C (dec.). IR: ν = 3350 (w), 3210 (ARDEC), W011NF-09-1-0056 (ARDEC), and 10 WPSEED01-
˜
¯
(m), 3067 (m), 1715 (s), 1685 (m), 1654 (w), 1600 (m), 1576 (w),
1560 (m), 1541 (w), 1394 (w), 1214 (m), 1192 (m), 1134 (w), 1091
(m), 1015 (m), 927 (w), 867 (s), 789 (w), 769 (w), 700 (w), 671
002/WP1765 (SERDP) is gratefully acknowledged. The authors
acknowledge collaborations with Dr. Mila Krupka (OZM Re-
search, Czech Republic) in the development of new testing and
(w) cm–1. Raman (1064 nm) = 3250 (11), 3218 (1), 3202 (1), 3180 evaluation methods for energetic materials and with Dr. Muhamed
(1), 3147 (1), 3117 (1), 1731 (2), 1599 (9), 1521 (2), 1412 (2), 1384
(25), 1319 (1), 1223 (3), 1136 (4), 1093 (12), 1010 (5), 790 (100),
636 91), 617 (20), 545 (3), 474 (3), 351 (2), 303 (22) cm–1. 1H NMR
Sucesca (Brodarski Institute, Croatia) in the development of new
computational codes to predict the detonation and propulsion pa-
rameters of novel explosives. We are indebted to and thank Drs.
(400 MHz, [D6]DMSO): δ = 8.96 (s, 2 H, C-NH2), 6.99 (s, 4 H, N- Betsy M. Rice and Brad Forch (ARL, Aberdeen, Proving Ground,
NH2) ppm. 13C NMR (68 MHz, [D6]DMSO): δ = = 147.2 (s, 1 C,
CN7H6) ppm. MS (FAB+): m/z = 116.1 [CN7H6]. MS (FAB–): m/z
= 78.9 [Br]. CN7H6Br (196.01): calcd: C 6.13, H 3.09, N 50.02;
found too sensitive for measurement. BAM impact: Ͻ1 J. BAM
friction: Ͻ5 N. ESD: 0.015 J.
MD) and Mr. Gary Chen (ARDEC, Picatinny Arsenal, NJ) for
many helpful and inspired discussions and support of our work.
The authors want to thank St. Huber for measuring the sensitivi-
ties.
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1,4,5-Triaminotetrazolium Nitrate (3): To a solution of triamino-
tetrazolium bromide (0.300 g, 1.53 mmol) dissolved in distilled
water (10 mL) was added a solution of silver nitrate (0.260 g,
1.53 mmol) in distilled water (10 mL). The solution was stirred in
the dark at 100 °C for 3 h. After filtration of silver bromide and
evaporation of the aqueous filtrate, triaminotetrazolium nitrate
(0.250 g, 92%) was obtained. DSC: 78 °C (dec.). IR: ν = 3325 (m),
˜
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3200 (m), 3088 (m), 1726 (m), 1645 (m), 1621 (m), 1374 (s), 1311
(s), 1220 (m), 1125 (w), 1086 (m) 1048 (w), 1033 (w), 1009 (w),
949 (w), 863 (w), 825 (m), 791 (w), 719 (w), 683 (w) cm–1. Raman
(1064 nm) = 3325 (1), 3214 (10), 1734 (2), 1620 (6), 1583 (2), 1521
(2), 1413 (1), 1384 (31), 1332 (1), 1231 (1), 1128 (3), 1088 (11), 1050
(100), 1009 (2), 792 (84), 722 (5), 617 (20), 543 (1), 323 (11), 291
(2) cm–1. 1H NMR (400 MHz, [D6]DMSO): δ = 8.97 (s, 2 H, C–
NH2), 7.00 (s, 4 H, N–NH2) ppm. 13C NMR (68 MHz, [D6]-
DMSO): δ = 147.2 (s, 1C, CN7H6) MS (FAB+): m/z = 116.1
[CN7H6]. MS (FAB–): m/z = 62.0 [NO3]. CN7H6NO3 (178.11):
calcd: C 6.74, H 3.40, N 62.91; found too sensitive for measure-
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1,4,5-Triaminotetrazolium Nitrotetrazolate 2-Oxide (4): To a solu-
tion of triaminotetrazolium bromide (0.200 g, 1.02 mmol) dissolved
in distilled water (10 mL) was added silver nitrotetrazolate 2-oxide
(0.243 g, 1.02 mmol). The solution was stirred in the dark at 100 °C
for 3 h. After filtration of silver bromide and evaporation of the
aqueous filtrate, triaminotetrazolium nitrotetrazolate 2-oxide
(0.668 g, 67%) was obtained. DSC: 84 °C (dec.). IR: ν = 3384 (m),
˜
3338 (m), 3188 (m), 2951 (m), 1717 (m), 1636 (w), 1535 (s), 1466
(m), 1457 (m), 1419 (s), 1391 (s), 1311 (s), 1234 (m), 1185 (w), 1129
(w), 1114 (w), 1085 (w), 1051 (w), 1001 (w), 917 (w), 846 (w), 785
(s), 759 (w), 693 (w) cm–1. Raman (1064 nm): = 3382 (1), 3313 (1),
3251 (5), 1831 (1), 1599 (1), 1544 (5), 1522 (2), 1430 (100), 1407
(37), 1317 (19), 1237 (3), 1087 (77), 1059 (21), 1004 (94), 851 (1),
797 (11), 762 (2), 617 (6), 491 (4), 429 (2), 399 (1), 340 (8), 239
(7) cm–1. MS (FAB+): m/z = 116.1 [CN7H6]. MS (FAB–): m/z =
62.0 [NO3]. CN7H6CN5O3 (246.15): calcd: C 9.76, H 2.46, N 68.28;
found too sensitive for measurement. BAM impact: 1 J; BAM fric-
tion: 7 N; ESD: 0.100 J.
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Acknowledgments
Financial support of this work by the Ludwig-Maximilian Univer-
sity of Munich (LMU), the U.S. Army Research Laboratory
(ARL), the Armament Research, Development and Engineering
Center (ARDEC), the Strategic Environmental Research and De-
velopment Program (SERDP), and the Office of Naval Research
(ONR Global, title: “Synthesis and Characterization of New High
Energy Dense Oxidizers (HEDO) - NICOP Effort “) under
contract nos. W911NF-09-2-0018 (ARL), W911NF-09-1-0120
Eur. J. Inorg. Chem. 2012, 5694–5700
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
5699

T. M. Klapötke, D. G. Piercey, J. Stierstorfer
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Received: August 22, 2012
Published Online: October 5, 2012
5700
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© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 5694–5700