Nitroimino-tetrazolates and oxy-nitroimino-tetrazolates

Article abstract of DOI:10.1021/ja107729c

Highly energetic 1,1′-ethylenebis(oxy)bis(5-nitroimino-tetrazolate) salts were obtained by reacting equimolar quantities of the acidic 1,1′-ethylenebis(oxy)bis(5-nitroimino-tetrazole) and energetic bases in aqueous solution. Addtionally, metathesis of silver 1,1′-ethylenebis(oxy) bis(5-nitroimino-tetrazolate) with diaminoguanidinium chloride or triaminoguanidinium chloride gave the corresponding oxy-nitroimino-tetrazolate salt. These salts were fully characterized using IR and multinuclear NMR spectroscopy, elemental analysis, and differential scanning calorimetry (DSC), and, in some cases, 2?2H₂O, 8?2H₂O, 10, 13?2H₂O and 14, with single crystal X-ray structuring. The heats of formation for all compounds were calculated with Gaussian 03 and then combined with measured densities to determine detonation pressures (P) and velocities (D) of the energetic materials (Cheetah 5.0). The impact sensitivities of all salts were found to be less than those of the parent compounds. The physical and detonation properties of these oxy-nitroimino- tetrazolate salts are comparable to the analogous newly prepared diaminoguanidinium and triaminoguanidinium 1,1′-ethylenebis(5-nitroimino- tetrazolate)s.

Full text of DOI:10.1021/ja107729c

Published on Web 10/06/2010
Nitroimino-tetrazolates and Oxy-nitroimino-tetrazolates
Young-Hyuk Joo and Jean’ne M. Shreeve*
Department of Chemistry, UniVersity of Idaho, Moscow, Idaho 83844-2343, United States
Received September 3, 2010; E-mail: jshreeve@uidaho.edu
Abstract: Highly energetic 1,1′-ethylenebis(oxy)bis(5-nitroimino-tetrazolate) salts were obtained by reacting
equimolar quantities of the acidic 1,1′-ethylenebis(oxy)bis(5-nitroimino-tetrazole) and energetic bases in
aqueous solution. Addtionally, metathesis of silver 1,1′-ethylenebis(oxy)bis(5-nitroimino-tetrazolate) with
diaminoguanidinium chloride or triaminoguanidinium chloride gave the corresponding oxy-nitroimino-
tetrazolate salt. These salts were fully characterized using IR and multinuclear NMR spectroscopy, elemental
analysis, and differential scanning calorimetry (DSC), and, in some cases, 2·2H2O, 8·2H2O, 10, 13·2H2O
and 14, with single crystal X-ray structuring. The heats of formation for all compounds were calculated
with Gaussian 03 and then combined with measured densities to determine detonation pressures (P) and
velocities (D) of the energetic materials (Cheetah 5.0). The impact sensitivities of all salts were found to be
less than those of the parent compounds. The physical and detonation properties of these oxy-nitroimino-
tetrazolate salts are comparable to the analogous newly prepared diaminoguanidinium and triaminoguani-
dinium 1,1′-ethylenebis(5-nitroimino-tetrazolate)s.
Introduction
Nitroimino-tetrazole families,1 which are five-membered
aromatic heterocycles with a nitroimine substituent, are one
approach in the development of new energetic materials. They
are very useful as less toxic energetic materials. Most of the
compounds exhibit positive heats of formation owing to their
high nitrogen content and to their excellent thermal stabilities
arising from their aromaticity.1a 1-Methyl-5-nitroimino-tetrazole
was first prepared and characterized (pK ) 2.72, melting point
)158-160 °C) nearly 50 years ago.2 It was of interest to
examine the reactivity of the relatively acidic hydrogen of the
tetrazole ring. Recently, the Klapo¨tke group reported more
information about the calculated detonation properties of
1-methyl-5-nitroimino-tetrazole, confirmed a synthetic method
for preparing substituted nitroimino-tetrazoles in better yields,
and established structure by single-crystal X-ray diffraction
analysis.3 Moreover, synthesis and characterization of various
guanidinium nitroimino-tetrazolate salts, which can be prepared
from silver nitroimino-tetrazolate by metathesis, were reported
as high energy density materials.4
Figure 1. Bis(5-nitroimino-tetrazole) 1 and 2.
One high nitrogen system extensively studied by the Idaho
group is the substituted nitroimino-tetrazole. By employing an
alternate route, we reported the effective synthesis of the
disubstituted 5-nitroimino-tetrazoles, 1,1′-ethylenebis(5-nitroimino-
tetrazole) (1)5 and 1,1′-ethylenebis(oxy)bis(5-nitroimino-tetra-
zole) (2)6 (Figure 1). The development of disubstituted 5-ami-
notetrazole compounds was extended by the utilization of an
excellent in situ method which involved reactions of cyanogen
azide7 and primary amines. Nitration of these aminotetrazoles
using 100% nitric acid has been shown to form disubstituted
nitroimino-tetrazole derivatives. Compound 1 exhibits a high
measured density of 1.858 g cm-3; calculated heat of formation
of 3.63 kJ g-1; detonation pressure of 38.19 GPa; and a
detonation velocity of 9329 m s-1. The values of the detonation
properties of compound 2 (P ) 38.38 GPa, D ) 9200 m s-1
)
(1) (a) Klapo¨tke, T. M. in High Energy Density Materials, Klapo¨tke, T. M.
(Ed.), Springer, Berlin, Heidelberg, 2007, pp 85-121. (b) Klapo¨tke,
T. M.; Stierstorfer, J.; Weber, B. Inorg. Chim. Acta 2009, 362, 2311–
2320. (c) Gao, H.; Huang, Y.; Ye, C.; Twamley, B.; Shreeve, J. M.
Chem.sEur. J. 2008, 14, 5596–5603. (d) Xue, H.; Gao, H.; Twamley,
B.; Shreeve, J. M. Chem. Mater. 2007, 19, 1731–1739. (e) Geisberger,
G.; Klapo¨tke, T. M.; Stierstorfer, J. Eur. J. Inorg. Chem. 2007, 4743–
4750. (f) Klapo¨tke, T. M.; Radies, H.; Stierstorfer, J. Z. Naturforsch.
2007, 62b, 1343–1352. (g) Semenov, S. N.; Rogachev, A. Y.; Eliseeva,
S. V.; Belousov, Y. A.; Drozdov, A. A.; Troyanov, S. I. Polyhedron
2007, 26, 4899–4907. (h) Tappen, B. C.; Beal, R. W.; Brill, T. B.
Thermochim. Acta 2002, 388, 227–232.
are as high as for compound 1 and its oxygen percentage is
slightly improved. Impact sensitivity measurements on oxy-
nitroimino-tetrazole 2 indicate that it is very sensitive to shock;
accordingly it should be handled with caution and in small
amounts. For this reason, 2 needs to be desensitized perhaps
by salt formation. Recently we reported that reduced sensitivity
(5) Joo, Y.-H.; Shreeve, J. M. Angew. Chem., Int. Ed. 2009, 48, 564–
567.
(2) Garrison, J. A.; Herbst, R. M. J. Org. Chem. 1957, 22, 278–283.
(3) Klapo¨tke, T. M.; Stierstorfer, J. HelV. Chim. Acta 2007, 90, 2132–
2150.
(6) Joo, Y.-H.; Shreeve, J. M. Angew. Chem., Int. Ed. 2010, 49, 7320–
7323.
(4) Klapo¨tke, T. M.; Stierstorfer, J.; Wallek, A. U. Chem. Mater. 2008,
20, 4519–4530.
(7) (a) Marsh, F. D.; Hermes, M. E. J. Am. Chem. Soc. 1964, 86, 4506–
4507. (b) Marsh, F. D. J. Org. Chem. 1972, 37, 2966–2969.
9
10.1021/ja107729c  2010 American Chemical Society
J. AM. CHEM. SOC. 2010, 132, 15081–15090 15081

A R T I C L E S
Joo and Shreeve
Scheme 1. Synthesis of 1,1′-Ethylenebis(oxy)bis(5-nitroimino-tetrazolate) Salts
was obtained by making energetic salts of compound 1 and
energetic bases.8 The formation of salts of the nitroimino-
tetrazole led to an enhanced thermal stability and less or equal
impact sensitivity compared to those of a neutral compound.
The aim of this work was to prove the structures of important
crystalline energetic salts using X-ray diffraction analysis and
to discover new and potent nitroimino-tetrazolate salts. Oxy-
5-nitroimino-tetrazolate salts are of interest as ionic energetic
materials, which have good thermal stabilities and low impact
sensitivities, and which deserve closer attention by researchers
because they are closely linked with the safety of handling and
application of explosives. Here, we compare properties of the
new oxy-nitroimino-tetrazolate salts with new as well as our
previously reported nitroimino-tetrazolate salts.8
oxy-nitroimino-tetrazole 2 was prepared from oxy-aminotetra-
zole 4 in good yield by a nitration procedure from the literature.6
All attempts to remove water molecules in the crystal of 2·2H2O
to give 2 at 60 °C under high vacuum were successful. However,
violent detonations during attempted elemental analyses deter-
minations, compound 2 and 2·2H2O were not analyzed.
Fortunately, it was possible to perform single-crystal X-ray
diffraction analysis for 2·2H2O. The energetic salts 6-9 were
generally obtained by acid-base reactions between 2 and
energetic bases in aqueous solutions (Scheme 1).
Also, in Scheme 1 is shown the syntheses of the diami-
noguanidinium and triaminoguanidinium oxy-nitroimino-tetra-
zolate salts. Two energetic salts, 10 and 11, were synthesized
using silver 1,1′-ethylenebis(oxy)bis(5-nitroimino-tetrazolate)
(5), which was obtained by metathesis of sodium 1,1′-ethyl-
enebis(oxy)bis(5-nitroimino-tetrazolate) and silver nitrate, with
the corresponding chloride salts. After stirring for four hours,
silver chloride from the suspension was filtered and the filtrate
was dried. The structures of 1,1′-ethylenebis(oxy)bis(5-ni-
troimino-tetrazole) (2) and its salts are supported by IR, and
1H, 13C, and 15N NMR spectroscopic data as well as elemental
analysis.
Next similar successful attempts were made to prepare
bis(diaminoguanidinium) 1,1′-ethylenebis(5-nitroimino-tetra-
zolate) (13) and bis(triaminoguanidinium) 1,1′-ethylenebis(5-
nitroimino-tetrazolate) (14) in good yields by metathesis with
silver salt 12 (Scheme 2). The structures of 13 and 14 are
supported by IR, and 1H, 13C, and 15N NMR spectroscopic data
as well as elemental analysis. Salt 14 also could be prepared
by metathesis reactions of barium 1,1′-ethylenebis(oxy)bis(5-
aminotetrazolate) with the corresponding triaminoguanidinium
sulfate in a yield of 74%.
Results and Discussion
The reaction of ethylene(oxyphthalimide), which was pre-
pared via the treatment of 1,2-dibromoethane with N-hydrox-
yphthalimide according to the literature procedure, called Gabriel
Amine Synthesis, gave the ethylenebis(oxyamine) 3 by hydrazi-
nolysis.9 A convenient method for the synthesis of 1,1′-
ethylenebis(oxy)bis(5-aminotetrazole) 4 from 3 and cyanogen
azide without the intermediate isolation of imindoylazide was
developed and resulted in the preparation of the target oxy-
aminotetrazole 4 in 20% yield. The corresponding high energetic
(8) Joo, Y.-H.; Shreeve, J. M. Chem.sEur. J. 2009, 15, 3198–3203.
(9) (a) McDowell, C. S.; Barnes, M. W. U.S. Patent 3709920, 1973; Chem.
Abstr. 1973, 78, 71499. (b) McDowell, C. S.; Merrill, C. U.S. Patent
3714200, 1973; Chem. Abstr. 1973, 78, 135645. (c) McDowell, C. S.;
Merrill, C. U.S. Patent 3714199, 1973;Chem. Abstr. 1973, 78, 135644.
(d) Davydov, D. V.; Beletskaya, I. P. Russ. J. Org. Chem. 2004, 40,
124–126.
(10) (a) APEX2 V2.1-0, 2006, Bruker AXS Inc., Madison, Wisconsin,
USA. (b) SAINT V7.34 A, 2005, Bruker AXS Inc., Madison, Wisconsin,
USA. (c) XPREP V2005/2, 2004, Bruker AXS Inc., Madison,
Wisconsin, USA. (d) SADABS V2004/1, 2004, Bruker AXS Inc.,
Madison, Wisconsin, USA. (e) SHELXTL V6.12, 2000b, Bruker AXS
Inc., Madison, Wisconsin, USA.
Crystal Structure Analysis. Data collection was performed,
and the unit cell was initially refined using APEX2 [v2.1-0].10a
Data reduction was performed using SAINT [v7.34A]10b and
XPREP [v2005/2].10c Corrections were applied for Lorentz,
9
15082 J. AM. CHEM. SOC. VOL. 132, NO. 42, 2010

Nitroimino-tetrazolates and Oxy-nitroimino-tetrazolates
A R T I C L E S
Scheme 2. Synthesis of 1,1′-Ethylenebis(5-nitroimino-tetrazolate)
Salts by Metathesis
Compound 8·2H2O crystallized in a triclinic cell in the space
j
group P1 with two molecules in the unit cell. The tetrazole ring
of 8·2H2O is nearly planar and four similar bond lengths are
observed [N1-N2 ) 1.336(16) Å, N3-N4 ) 1.369(19) Å,
N4-C5 ) 1.326(16) Å, N1-C5 ) 1.349(18) Å], and shows
the delocalization of the negative charge from the ring (Figure
3). The main change observed is the bond length of N2-N3
which corresponds to the N4 nitrogen atom that undergoes
deprotonation in 1. Deprotonation results in a lengthening of
the N1-N2 and N3-N4 distances (∼0.01 Å) and a shortening
of the N2-N3 bond (∼0.02 Å). These distances are considerably
longer than N2-N3 double bonds (1.291(2) Å) but significantly
shorter than the O10-C11 [1.461(17) Å] or N1-O10 [1.363(14)
Å] single bond. The nitroimine unit lies in the plane of the
tetrazole ring as clearly shown by the C5-N6-N7-O9 torsion
angle of -0.57(18)° and C5-N6-N7-O8 torsion angle of
-179.27(11)°, in which the oxygen atoms O8 and O9 are
twisted slightly out of the plane. The ethoxy unit does not lie
intheplaneofthetetrazolering[torsionangleC5-N1-O10-C11
of 91.50(15)°]. The observed angle in the tetrazolate matches
the typical values found in the literature for oxy-nitroimino-
tetrazolate.6
polarization, and absorption effects using SADABS [v2004/
1].10d The structure was solved and refined with the aid of the
programs in the SHELXTL-plus [v6.12] system of programs.10e
The full-matrix least-squares refinement on F2 included atomic
coordinates and anisotropic thermal parameters for all non-H
atoms. The H atoms were included using a riding model.
Selected data and parameters of the X-ray determinations are
given in Table 1. Further information about crystal structure
determinations is given in the Supporting Information.
The colorless crystals of 10 were grown by slow evaporation
of an aqueous solution. The unit cell of 10, which crystallizes
with a calculated density of 1.675 g cm-3 (296(2) K) in the
j
monoclinic space group P1, contains two formula moieties. The
bond lengths and angles of the diaminoguanidinium cation
correspond to the values of diaminoguanidinium 1-methyl-5-
nitroimino-tetrazolate.4 Between the oxy-nitroimino-tetrazolates,
a torsion angle O10-C11-C12-O13 of -54.70(17)° is ob-
served (Figure 4).
The bond lengths in oxy-5-nitroimino-tetrazolate are very
similar to the values found and discussed for 8·2H2O. The
packing of 10 is also characterized by a three-dimensional
network (see Supporting Information), whereby several weak
hydrogen bonds are formed between the nitrogen atom of the
diaminoguanidinium cation and the nitrogen or oxygen atom
of the oxy-nitroimino-tetrazolate anion.
Diaminoguanidinium 1,1′-ethylenebis(5-nitroimino-tetra-
zolate) 13·2H2O crystallizes in the monoclinic crystal system
in the space group P21/c. By including four molecular moieties
in the unit cell, the calculated density is 1.636 g cm-3. In general,
the diaminoguanidine cations have geometries found in diami-
noguanidinium sulfate.11 This cation is nearly planar with torsion
angle (N26-C21-N22-N23 176.96(12)°) and C-N bond
lengths observed between 1.3284 and 1.3310 Å. Two nitroimino-
tetrazole anions in the molecule exhibit coplanar geometry with
torsion angle N1-C10-C11-N12 179.29(10) (Figure 5).
The geometry of the triaminoguanidine cation is comparable
to that observed for triaminoguanidinium sulfate in the litera-
ture.11 The positive charge is delocalized as supported by similar
C-N bond lengths C21-N22 ) 1.328(2) Å, C21-N24 )
1.323(2) Å, C21-N26 ) 1.324(2) Å and a planar system. The
hydrazine bonds of triaminoguanidine cation have similar
lengths between 1.401(2) and 1.413(2) (Figure 6). The constitu-
tion of the nitroimino-tetrazole anion is comparable to those
observed for 13·2H2O. However, the nitroimino-tetrazolate rings
are considerably twisted relative to each other with a torsion
angle N1-C10-C11-N12 at 57.2(2)°.
As expected and found in several selected structures inclu-
ding 1,1′-ethylenebis(oxy)bis(5-nitroimino-tetrazole) dihydrate
(2·2H2O) and its salts (8·2H2O and 10) and 1,1′-ethylenebis(5-
nitroimino-tetrazolate) salts (13·2H2O and 14) discussed in this
work, the nitroimino-tetrazole ring is nearly planar, building
an aromatic system, which can be seen at the torsion angle
N1-N2-N3-N4 of between 0.14(14)° and 0.71(15)°. The ring
moieties of 2·2H2O, 8·2H2O, 10, 13·2H2O, and 14 are in
agreement with the geometry observed for 5-nitroimino-tetra-
zoles and their salts.3-6,8 The N2-N3 bond lengths of all
structures of 2·2H2O, 8·2H2O, 10, 13·2H2O, and 14 lie between
1.271 and 1.294 Å, which are typical values observed for the
nitroimino-tetrazoles and their anions. We observed that, for
the N2-N3 bond lengths, neutral compounds 1 (1.271 Å) and
2·2H2O (1.271 Å) are slightly shorter than their salts (between
1.291 and 1.294 Å).
1,1′-Ethylenebis(oxy)bis(5-nitroimino-tetrazole) dihydrate
(2·2H2O) crystallizes in the monoclinic space group C2/c with
four molecules in the unit cell (Figure 2), and has a density of
1.684 g cm-3 (at 296 K) (Table 1). The C-N and N-N bonds
of the tetrazole ring are in a range similar to that observed in
1.5 The N1-O10 distances (1.3591 Å) in 2 are found to be
shorter than the N-C distances (1.460 Å) in compound 1. The
tetrazole ring [torsion angle N1-N2-N3-N4 0.71(15)°] is
planar, which is a condition of the 6π aromaticity, and the
nitroimine group [torsion angle N4-C5-N6-N7 1.3(2)°] is also
almost planar out of this ring. In contrast to this, the ethoxy
unit [torsion angle C5-N1-O10-C11 -84.65(14)°] is signifi-
cantly bent from the ring plane. The packing structure of
2·2H2O is strongly influenced by strong hydrogen bonds
between H2O and 2. These extensive hydrogen-bonding interac-
tions between oxygen atom O1S from water and N4 [N4 · · ·O1S
2.6854(16)] can be seen in Figure 2b along the b axis.
(11) Klapo¨tke, T. M.; Mayer, P.; Stierstorfer, J. Phosphorus, Sulfur Silicon
Relat. Elem. 2009, 184, 2393–2407.
(12) Joo, Y.-H.; Twamley, B.; Shreeve, J. M. Chem.sEur. J. 2009, 15,
9097–9104.
9
J. AM. CHEM. SOC. VOL. 132, NO. 42, 2010 15083

A R T I C L E S
Joo and Shreeve
Table 1. Crystallographic Data for 2·2H2O, 8·2H2O, 10, 13·2H2O, and 14
2·2H2O
8·2H2O
10
13 ·2H2O
14
formula
fw
space group
a (Å)
b (Å)
c (Å)
R (deg)
ꢀ (deg)
γ (deg)
V (Å3)
Z
C4H10N12O8
354.24
C2/c
26.767(6)
4.8803(10)
10.707(2)
90
92.639(3)
90
1397.2(5)
4
C5H16N16O9
444.34
P1
C6H20N22O6
496.44
P1
C6H24N22O6
500.47
P21/c
14.251(2)
12.9147(19)
11.0418(17)
90
91.008(2)
90
2031.9(5)
4
C6H24N24O5
512.49
P21/c
14.1339(17)
22.245(3)
6.8288(8)
90
94.726(2)
90
2139.7(4)
4
j
j
7.7035(3)
10.8458(4)
10.9203(4)
79.481(1)
76.778(1)
77.897(1)
859.74(6)
2
7.5429(5)
8.9642(6)
15.2214(11)
80.376(2)
82.322(2)
77.146(2)
984.31(12)
2
λ (Å)
0.71073
296(2)
1.684
0.157
0.0317
0.0880
0.71073
296(2)
1.716
0.157
0.0331
0.71073
296(2)
1.675
0.144
0.0383
0.71073
296(2)
1.639
0.140
0.0341
0.0875
0.71073
296(2)
1.591
0.134
0.0426
0.0951
T (K)
Dcalcd (g cm-3
)
µ (mm-1
)
R1 [I > 2σ(I)]a
wR2 [I > 2σ(I)]b
0.0853
0.0951
b
a R1 ) ∑|Fo| - |Fc|/∑|Fo|. wR2 ) {∑[w(Fo - Fc2)2]/∑[w(Fo )2]}1/2
.
2
2
Figure 2. (a) View of the molecular unit of 2·2H2O. Thermal ellipsoids represent 50% probability. (b) Unit cell view along the b axis. Selected bond
lengths [Å]: N1-N2 1.3479(18), N2-N3 1.2715(18), N3-N4 1.3605(17), N4-C5 1.3315(18), N1-C5 1.3553(17), C5-C6 1.3296(18), N6-N7 1.3472(16),
N1-O10 1.3618(15), O10-C11 1.4589(19).
The 15N NMR chemical shift data of the 1,1′ethylenebis(oxy)-
bis(5-nitroimino-tetrazolate) salts 6-11 and 1,1′-ethylenebis(5-
nitroimino-tetrazolatate) salts 13 and 14 are presented in Table
2. On the basis of the values of the chemical shifts of guanidine
or hydrazine moieties, NH, NH2, and NH3 groups can be
assigned to the resonances at highest field on the basis of
comparison with the literature4,11 (see Experimental Section).
The assignment of the resonance peaks between the coordinated
nitrogen atoms of nitroimino-tetrazoles 2 can be achieved mainly
on the basis of the fact that N1 has one oxygen, one carbon,
and one nitrogen atom as nearest neighbors, while N4 has one
carbon and one nitrogen. Dependency of the resonance shift in
+
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Nitroimino-tetrazolates and Oxy-nitroimino-tetrazolates
A R T I C L E S
Figure 3. View of the molecular unit of 8·2H2O. Thermal ellipsoids represent 50% probability. Selected torsion angles [deg]: C5-N6-N7-O9 -0.57
(18), C5-N6-N7-O8 -179.27(11), C5-N1-O10-C11 91.50(15).
N1 (-117 ppm) of 2 with an alkoxy substituent are observed
at a relatively lower field than the alkyl-substituted N1 of 1
(-170.6 ppm) in the tetrazole ring because of the strong
electronegativity effect. By comparison with neutral nitroimino-
tetrazole 1 and 2 (Table 2), the N4 resonance for the deproto-
nated nitroimino-tetrazole, 6-11, 13 and 14 is observed at
considerably lower field (50-80 ppm) than for the former
compounds, 1 and 2. The assignments are based on the values
of the chemical shifts reported for nitroimino-tetrazolate salts
in the literature.3-6,8
The 15N NMR spectra of nitroimino-tetrazolate salts were
measured in DMSO[D6] solution, and chemical shifts are given
with respect to CH3NO2 as external standard. In Figure 7,
selected 15N NMR spectra of 7, 9, 11, and 14 are shown.
In the case of compound 7, the signals for the NR (-317.5
ppm) from azide (R-N3: R-NRNꢀNγ) and ammonium cation
(-336.9 ppm) appear at the highest field. Nꢀ and Nγ are at
-134.9 ppm and -171.1 ppm, respectively. Comparison of the
resonances observed for the oxy-5-nitroimino-tetrazolate anion
in this study shows the expected shifts.13 Compound 9 signals
for the hydrazinium cation bonded to tetrazine appear at the
Figure 4. View of the molecular unit of 10. Thermal ellipsoids represent
50% probability.
highest field (NH and NH2). The chemical shift of N7 (-26.7
ppm) in the tetrazine ring,8 and those for the alkoxy-nitroimino-
tetrazolate anion were assigned on the basis of comparison with
literature values.6 The spectrum of 11 with eight signals at
-319.6 (NH2), -279.2 (NH), -151.0 (N5), -115.9 (N1), -64.1
(N4), -19.4 (N3), -4.4 (NO2), 3.5 (N2) is shown. The signals
for N1, which has oxygen as a neighbor in the tetrazole ring
appear as expected at lower field (-115.9 ppm) compared with
the Nl position (-166.7 ppm) of triaminoguanidinium 1,1′-
ethylene bis(5-nitroimino-tetrazolate) (14). The assignments are
based on the literature values of the remainder of the peaks
which are essentially unchanged for the nitroimino-tetrazole
group.3-6,8
Physical Properties. Heat of formation is one of the important
characteristics for energetic salts which is directly related to
the number of nitrogen-nitrogen bonds in an ionic species.14
All quantum chemical calculations were carried out using the
program package Gaussian 03 (Revision D.01).15 The geometric
optimization of the structures and frequency analyses was
accomplished by using the B3LYP with the 6-31+G** basis
Figure 5. View of the molecular unit of 13 · 2H2O. Thermal ellipsoids
set,16 and single-point energies were calculated at the MP2/6-
represent 50% probability. Selected bond lengths [Å]: N1-N2 1.3498(16),
N2-N3 1.2940(16), N3-N4 1.3590(16), N4-C5 1.3344(17), N1-C5
1.3614(16), N1-C10 1.4587(16), C5-N6 1.3631(17), C10-C11 1.5224(18).
(13) Joo, Y.-H.; Shreeve, J. M. Inorg. Chem. 2009, 48, 8431–8438.
Selected torsion angles [deg]: C5-N1-C10-C11 -97.99(15), N1-C10-
(14) Gao, H.; Ye, C.; Piekarski, C. M.; Shreeve, J. M. J. Phys. Chem. C
C11-N12 179.29(10).
2007, 111, 10718–10731.
(15) Frisch, M. J.; et al. Gaussian 03, Revision D.01; Gaussian, Inc.:
the 15N NMR can thus be used to assign the 15N signals in the
tetrazole ring and to distinguish from the substituted and
nonsubstituted nitrogen atoms. In Table 2, the resonance for
Wallingford, CT, 2004.
(16) Parr, R. G.; Yang, W. Density Functional Theory of Atoms and
Molecules; Oxford University Press: New York, 1989.
9
J. AM. CHEM. SOC. VOL. 132, NO. 42, 2010 15085

A R T I C L E S
Joo and Shreeve
Figure 6. View of the molecular unit of 14. Thermal ellipsoids represent 50% probability.
Table 2. Comparison of the 15N NMR Chemical Shifts (ppm) of
Nitroimino-tetrazole 1, Oxy-nitroimino-tetrazole 2, and Their Saltsa
Scheme 3. Isodesmic Reactions of the Bis(nitroimino-tetrazolate)
Anions
cmpd
N1
N2
N3
N4
N5
N6 (NO2)
1b
2
6
7
8
-170.6
-117.0
-125.5
-125.5
-118.6
-118.8
-116.1
-115.9
-166.7
-166.7
-20.1
-10.6
-6.3
-6.1
-0.1
-0.6
3.2
3.5
-21.5
-21.5
-24.7
-24.5
-28.7
-28.8
-21.6
-21.8
-19.5
-19.4
5.5
-154.3
-124.3
-74.4
-74.7
-71.2
-72.4
-64.6
-64.1
-73.2
-73.0
-156.8
-154.7
-160.0
-160.0
-152.9
-153.0
-150.9
-151.0
-157.7
-157.8
-15.5
-17.8
-14.3
-13.9
-6.9
9
-7.0
10
11
13
14
-4.7
-4.4
-14.5
-14.4
5.5
a All shifts were measured with [D6]DMSO at 30 °C. b At 55 °C.
to be true local energy minima on the potential-energy surface
without imaginary frequencies. The remaining task is to
determine the heats of formation of the cations and anions,
which are computed by using the method of isodesmic reactions
(Scheme 3).
The enthalpy of an isodesmic reaction (∆H°r298) is obtained
by combining the MP2/6-311++G** energy difference for the
reaction, the scaled zero-point energies (B3LYP/6-31+G**),
and other thermal factors (B3LYP/6-31+G**). Thus, the heats
of formation of the cations and anions being investigated can
be extracted readily (Table 3).
On the basis of Born-Haber energy cycles (Figure 8), the
heats of formation of ionic salts can be simplified by eq 1:
∆H°(ionic salt, 298 K) ) ∆H°(cation, 298 K) +
f
f
∆H°(anion, 298 K) - ∆HL (1)
f
The lattice potential energies (UPOT) and lattice enthalpies
(∆HL) were calculated according to the followed equations
provided by Jenkins and are summarized18 in which ∆HL is
the lattice energy of the ionic salt. The ∆HL value can be
predicted by the formula, eq 2,18 where UPOT is the lattice
potential energy, nM and nX depend on the nature of the ions
Figure 7. Selected 15N NMR spectra of nitroimino-tetrazolate salts.
-
Mp+ and Xq , respectively, and are equal to three for monatomic
311++G** level. Atomization energies were calculated by the
G2 method.17 All of the optimized structures were characterized
(18) Jenkins, H. D. B.; Tudeal, D.; Glasser, L. Inorg. Chem. 2002, 41,
(17) Suleimenov, O. M.; Ha, T. K. Chem. Phys. Lett. 1998, 290, 451–457.
2364–2367.
9
15086 J. AM. CHEM. SOC. VOL. 132, NO. 42, 2010

Nitroimino-tetrazolates and Oxy-nitroimino-tetrazolates
A R T I C L E S
Table 3. Physical Properties of Oxy-nitroimino-tetrazolate Salts 6-11 Compared with Nitroimino-tetrazolate Salts
c
]
f
]
compd
Tm [°C]a
Tdec [°C]b
density [g cm-3
P [GPa]e
D [m s-1
IS [J]g
OB [%]h
6
7
8
-
200
151
130, 146
156
147
147
131
164
162
220
218
195
255
186
203
203
230
1.602
1.597
1.695
1.716i
1.647
1.780
1.683
1.675i
1.607
1.577
1.639i
1.601
1.610
1.600
1.722
1.820
1.816
1029 (2.21)
2944 (4.14)
1134 (2.78)
-
26.78
26.56
32.20
-
8472
8377
8789
-
6
<1
6
2
8
-51
-63
-35
-35
-35
-42
-42
-52
-52
-62
-62
-61
-63
-73
-47
-52
-22
-
-
8·2H2O
8·4H2O
9
9·2H2O
10
11
13
127
71, 78, 129
-
-
-
-
1270 (2.76)
-
1254 (2.53)
1487 (2.82)
1233 (2.66)
-
1458 (2.95)
993 (2.29)
2922 (4.31)
1094 (2.91)
1231 (2.87)
92.6 (0.42)
33.25
-
28.72
29.36
26.51
-
28.64
26.27
26.45
31.98
34.25
35.17
9030
-
8741
8840
8568
-
8860
8531
8429
8957
9305
8977
2
72
160
95, 160
-
5
4
7
13·2H2O
202
132
-
>40
>40
10
5
10
15
7.4
14
AG I-8j
TAA I-8k
CH I-8l
TH I-8m
RDXn
-
-
-
-
b
a Melting point. Thermal decomposition temperature (onset) under nitrogen gas (DSC, 10 °C min-1). c From gas pycnometer (25 °C). d Heat of
formation (calculated via Gaussian 03). e Calculated detonation pressure (Cheetah 5.0). f Calculated detonation velocity (Cheetah 5.0). g Impact
sensitivity (BAM drophammer). h OB ) oxygen balance (%) for CaHbOcNd: 1600 × (c - 2a - b/2)/Mw, Mw ) molecular weight of salt. i X-ray density
(23 °C). j Bis(aminoguanidinium) 1,1′-ethylenebis(5-nitroimino-tetrazolate): ref 8. k Bis[1,3-diazido-2-(azidomethyl)-2-propylammonium] 1,1′-ethylenebis-
(5-nitroimino-tetrazolate): ref 13. l Carbohydrazinium 1,1′-ethylenebis(5-nitroimino-tetrazolate): ref 8. m 1,2,4,5-Tetrazino-3,6-bis(hydrazinium)
1,1′-ethylenebis(5-nitroimino-tetrazolate): ref 8. n Reference 22.
and 9 between 1 and 2 J. Compounds 13·2H2O and 14 are not
impact sensitive. Thermal stabilities of the energetic compounds
were studied with differential scanning calorimetry (DSC) at a
scan rate of 10 °C min-1. All nitroimino-tetrazolates decom-
posed between 130 and 220 °C (see DSC traces for all
compounds in the Supporting Information). As expected, the
thermal stabilities for all energetic salts are higher for the neutral
compounds 1 (194 °C) and 2 (125 °C). The most thermally
stable derivatives of 2 and 1 are the aminoguanidinium salts 6
and AG I-8 where decomposition occurred at 200 and 255 °C,
Figure 8. Born-Haber cycle for the formation of nitroimino-tetrazolate
salts.
respectively (Table 3). By using the calculated values of the
heats of formation and the experimental values for the densities
(gas pycnometer or X-ray values) of the new highly energetic
nitroimino-tetrazolate salts, 6-11, 13, and 14, the detonation
pressures (P) and detonation velocities (D) were calculated on
the basis of traditional Chapman-Jouget thermodynamic deto-
nation theory using Cheetah 5.0 (Table 3).20 The calculated
detonation pressures of nitroimino-tetrazolate salts lie in the
range between P ) 26.51 and P ) 33.25 GPa (comparable to
TATB ) 31.15, RDX ) 35.17 GPa). Detonation velocities lie
between D ) 8377 and D ) 9030 m s-1 (comparable to TATB
) 8114, RDX ) 8977 m s-1). These properties coupled with
the rather high thermal and hydrolytic stabilities make these
high-nitrogen materials attractive candidates for energetic ap-
plications. The oxygen balance (OB) is the index of the
deficiency or excess of oxygen in a compound required to
convert all carbon into carbon dioxide, and all hydrogen into
water; for a compound with the molecular formula of CaHbNcOd,
OB (%) ) 1600 × (d - 2a - b/2)/Mw (Table 3). The relatively
ions, five for linear polyatomic ions, and six for nonlinear
polyatomic ions.
∆HL ) UPOT + [p(nM/2 - 2) + q(nX/2 - 2)]RT
(2)
The equation for the lattice potential energy, UPOT, takes the
form of eq 3,
UPOT(kJ · mol-1) ) γ(Fm/Mm)1/3 + δ
(3)
where Fm is the density (g cm-3), Mm is the chemical formula
mass of the ionic material (g), and the coefficients γ (kJ mol-1
cm) and δ (kJ mol-1) are assigned literature values.18
In Table 3 it is shown that all nitroimino-tetrazolate salts are
highly endothermic compounds. The enthalpies of energetic
materials are controlled by the molecular structure of the
compounds. Consequently, heterocycles with higher nitrogen
content, especially tetrazole, show higher heats of formation.
All of the new compounds (6-11, 13, and 14) exhibit positive
heats of formation ranging between 2.21 and 4.14 kJ g-1
.
(19) (a) http://www.bam.de/en/index.htm. (b) A portion of 20 mg of
nitroimino-tetrazolate salts was subjected to a drop-hammer test using
a 5- or 10-kg weight. A range in impact sensitivities according to the
UN Recommendations (insensitive > 40 J; less sensitive g 35 J;
sensitive g 4 J; very sensitive e 3 J).
(20) Bastea, S.; Fried, L. E.; Glaesemann, K. R.; Howard, W. M.; Souers,
P. C.; Vitello, P. A. CHEETAH 5.0 User’s Manual, Lawrence
Livermore National Laboratory, 2007.
(21) Krause, H. H. In Energetic Materials; Teipel, U., Ed.; VCH: Weinheim,
2005; pp 1-25.
(22) Diaz, D. D.; Punna, S.; Holzer, P.; Mcpherson, A. K.; Sharpless, K. B.;
Fokin, V. V.; Finn, M. G. J. Polym. Sci., Part A: Polym. Chem. 2004,
42, 4392–4403.
Bis[1,3-diazido-2-(azidomethyl)-2-propylammonium] 1,1′-eth-
ylenebis(oxy)bis(5-nitroimino-tetrazolate) (9) has the highest
value at 4.14 kJ g-1 which is comparable to salt (TAA I-8)13
of the same cation and anion 12- with a high positive heat of
formation (4.31 kJ g-1). Impact sensitivity measurements were
made using standard BAM Fallhammer techniques.19 Listed in
Table 3 are impact sensitivities ranging from those of the
relatively less sensitive 6, 8, 8·4H2O, 9·2H2O, 10, 11, and 13,
between 4 and 8 J to the very sensitive compounds 7, 8·2H2O,
9
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A R T I C L E S
Joo and Shreeve
probe insertion (EI). Elemental analyses were carried out using an
Exeter CE-440 elemental analyzer. Details of the X-ray diffraction
analysis of compounds 2·2H2O, 8·2H2O, 10, 13 ·2H2O, and 14
are provided in Supporting Information. Data were collected on a
Bruker three-circle platform diffractometer equipped with a SMART
PLATINUM 135 CCD detector.
moderate oxygen balances of 8 and 9 are -35% and -42%,
respectively. Incorporation of one additional oxygen atom from
the oxyethylene link to the nitroimino-tetrazole moiety slightly
improves the oxygen balance of the corresponding compounds
and may eventually result in higher exothermicities of the
combustion and detonation processes.
1,1′-Ethylenebis(oxy)bis(5-nitroimino-tetrazole) (2).6 At 0 °C,
2 mmol 1,1′-ethylenebis(oxy)bis(5-aminotetrazole) was added in
small portions to 5 mL 100% HNO3. The reaction mixture was
stirred at ambient temperature for 18 h. The solution was poured
into ca. 20 g ice. After stirring for 3 h, the product was precipitated
(if not, water should be evaporated in air), filtered, washed with a
small amount of cold water, and dried in air at room temperature.
The crystal water of 2·3H2O could be removed under high vacuum
at 60 °C. 2·3H2O was recrystallized with water and formed 2·2H2O
as white crystals.
Conclusions
Oxy-5-nitroimino-tetrazolate salts (6-11) were synthesized
and characterized in order to develop new energetic materials.
Oxyamine and cyanogen azide were used as starting materials
for the preparation of the oxy-aminotetrazole. The latter was
converted into oxy-nitroimino-tetrazole 2 by nitration with 100%
nitric acid in a neat reaction. The 1,1′-ethylenebis(oxy)bis(5-
nitroimino-tetrazolate) salts were fully characterized using IR
and multinuclear NMR (1H, 13C, 15N) spectroscopy, elemental
analysis, and in some cases, single-crystal X-ray structuring was
done. Compound 2 is a very sensitive and highly energetic
compound which should be assigned to the class of primary
explosives and only be handled with appropriate precautions.
Although all of the energetic salts exhibit lower densities
(1.577-1.780 g cm-3) than the neutral nitroimino-tetrazole 2
(1.805 g cm-3), they have better thermal stabilities. Selected
oxy-nitroimino-tetrazolate salts 8, 9, and 11 show good heats
of formation (for 8: 2.78 kJ g-1, 9: 2.76 kJ g-1, 11: 2.82 kJ
g-1), good detonation pressures (for 8: 32.20 GPa, 9: 33.25 GPa,
Yield: 94%; White solid; Tdec 125 °C (onset); IR (KBr) ν˜ 3421,
3288, 3027, 1593, 1494, 1426, 1322, 1216, 1045, 1026, 1001, 978,
878, 842, 779, 694, 675, 631; 1H NMR δ 10.49 (s, 2H, H-tetrazole),
4.77 (s, 4H, CH2); 13C{1H} NMR δ 147.0, 76.9; 15N{1H} NMR δ
-10.6 (N2), -17.8 (N6), -24.5 (N3), -117.0 (N1), -124.3 (N4),
-154.7 (N5); MS (EI) m/z: 319 (0.2), 68 (8), 63 (2.4), 46 (100),
44 (61); Caution! During elemental analysis the compound exploded
and was not determinable. The structure of 2·2H2O is supported
by single crystal X-ray analysis.
1,1′-Ethylenebis(oxy)bis(5-nitroimino-tetrazole) (2) Trihydrate.6
White solid; Yield 94%, Tm 109 °C (H2O), Tdec 143 °C (onset); IR
(KBr) ν˜ 3419, 2898, 2727. 2645, 1592, 1498, 1425, 1333, 1247,
1053, 968, 916, 879, 840, 696, 681; 1H NMR δ 6.54 (8H,
H-tetrazole and 3H2O), 4.76 (s, 4H, CH2); 13C{1H} NMR δ 147.1,
76.9; Caution! during elemental analysis the compound exploded
and was not determinable.
11: 29.36 GPa), good detonation velocities (for 8: 8789 m s-1
,
9: 9030 m s-1, 11: 8840 m s-1). Calculated detonation values
of these compounds are comparable to those of explosives such
as RDX (P ) 35.17 GPa, D ) 8977 m s-1). To compare
properties, new energetic salts 13 and 14 based on 1,1′-
ethylenebis(5-nitroimino-tetrazole) 1 were synthesized and
characterized. While the detonation properties of salts derived
from precursors 1 and 2 are similar, for salts of 1 the thermal
stabilities and impact sensitivities are better than those for 2,
oxy-nitroimino-tetrazolate salts 6-11. Finally, all of the new
energetic salts are highly endothermic compounds, have high
performances and increased thermal or impact sensitivity values
in comparison to those of the neutral compounds 1 and 2 which
might be of interest for future applications as environmentally
friendly and high-performing nitrogen or oxygen-rich materials.
1,1′-Ethylenebis(oxy)bis(5-aminotetrazole) (4).6 At 0 °C, 10
mmol cyanogen bromide was dissolved in 50 mL dry acetonitrile
and 40 mmol dry sodium azide was added. The reaction mixture
was stirred at 0 °C for 4 h. The inorganic salt was filtered off (after
filtering, the salt must be dissolved in cold water quickly). The
cyanogen azide solution is added to a solution containing 2.5 mmol
bis(oxyamino)ethane9 in 20 mL water at 0 °C. After stirring
overnight at ambient temperature, the solvent was removed by
blowing air over the liquid surface. The product 4 was purified by
washing with water and acetonitrile.
Light-brown solid; yield 20%; Tdec 175 °C (onset); IR (KBr) ν˜
3331, 3150, 1661, 1603, 1449, 1314, 1263, 1106, 1032, 1014, 858;
1H NMR δ 7.10 (s, 4H, NH2), 4.65 (s, 4H, CH2); 13C{1H} NMR δ
149.3, 76.4; 15N{1H} NMR δ 1.3 (N3), -25.0 (N2), -87.7 (N4),
-127.2 (N1), -328.7 (NH2); EA (C4H8N10O2, 228.17) calcd: C,
21.06; H, 3.53; N, 61.39%. Found: C, 21.37; H, 3.55; N, 60.34%.
Impact sensitivity: 4 J.
Experimental Section
Safety Precautions. While we have experienced no difficulties
with the impact instability of the 1,1′-ethylenebis(5-nitroimino-
tetrazole) 1, 1,1′-ethylenebis(oxy)bis(5-aminotetrazole) 2, and their
salts (6-11, 13, and 14), they must be synthesized only in 1-2
mmol amounts. Manipulations must be carried out in a hood behind
a safety shield. Eye protection and leather gloves must be worn.
Caution should be exercised at all times during the synthesis,
characterization, and handling of any of these materials, and
mechanical actions involving scratching or scraping must be
avoided.
Silver 1,1′-Ethylenebis(oxy)bis(5-nitroimino-tetrazolate) (5).
Silver nitrate (680 mg, 4 mmol) was dissolved in 10 mL of water
and added to a solution of sodium 1,1-ethylenebis(oxy)bis(5-
nitroimino-tetrazolate), which was obtained from 636 mg (2.00
mmol) 1,1′-ethylenebis(oxy)bis(5-nitroimino-tetrazole) (2) and 160
mg (4.00 mmol) sodium hydroxide in 50 mL of water. The silver
salt precipitated immediately as a white powder. The suspension
was stirred for 5 h under ambient temperature. The product was
filtered off and dried with air overnight. White solid 5 was obtained
in a yield of 99% (1.05 mg, 1.97 mmol).
White solid; Tdec 200 °C (onset); IR (KBr) ν˜ 3433, 1518, 1464,
1430, 1400, 1333, 1265, 1095, 1009, 892, 847, 772, 583; EA
(C4H4Ag2N12O6, 531.89) calcd: C, 9.03; H, 0.76; N, 31.60%. Found:
C, 9.12; H, 0.81; N, 31.40%; Caution! During elemental analysis
the compound exploded.
General Methods. 1H, 13C, and 15N NMR spectra were recorded
on a 300 MHz (Bruker AVANCE 300) and 500 MHz (Bruker
AVANCE 500) nuclear magnetic resonance spectrometers operating
at 300.13, 75.48, and 50.69 MHz, respectively, by using DMSO[D6]
as solvent and locking solvent unless otherwise stated. The melting
and decomposition points were obtained on a differential scanning
calorimeter (TA Instruments Company, model Q10) at a scan rate
of 10 °C min-1. IR spectra were recorded using KBr pellets for
solids on BIORAD model 3000 FTS spectrometer. Densities of
the nitroimino-tetrazole and their salts were determined at 25 °C
by employing a Micromeritics AccuPyc 1330 gas pycnometer. Mass
spectra (Shimadzu GCMS-QP5050) were measured by using solid
Bis(aminoguanidinium)-1,1′-ethylenebis(oxy)bis(5-nitroimino-
tetrazolate) (6). The reaction of 318 mg (1.00 mmol) 1,1′-
ethylenebis(oxy)bis(5-nitroimino-tetrazole) 26 with 210 mg (2.00
9
15088 J. AM. CHEM. SOC. VOL. 132, NO. 42, 2010

Nitroimino-tetrazolates and Oxy-nitroimino-tetrazolates
A R T I C L E S
mmol) aminoguanidine bicarbonate in 10 mL water at 70 °C for
30 min gave a white solid (420 mg, 0.901 mmol, 90%) after air
drying.
Tdec 200 °C (onset); IR (KBr) ν˜ 3396, 3343, 3281, 3192, 3117,
1676, 1508, 1449, 1424, 1379, 1317, 1287, 1221, 1092, 1026, 1002,
1
889, 588, 509, 476; H NMR δ 8.54 (s, 2H, NH), 7.19 (br s, 4H,
NH2), 6.80 (br s, 4H, NH2), 4.64 (br s, 8H, NH2 and CH2 overlap);
13C{1H} NMR δ 158.8, 150.8, 76.2;14N NMR δ -13.6 (NO2);
15N{1H} NMR δ -14.3 (NO2), -6.3, -28.7, -74.4 (N-), -125.5,
-160.0, -283.4, -306.9 (br), -313.1 (br), -325.1; EA
(C6H18N20O6, 466.34) calcd: C, 15.45; H, 3.89; N, 60.07%. Found:
C, 15.41; H, 3.79; N, 59.91%.
Bis[1,3-diazido-2-(azidomethyl)-2-propylammonium]-1,1′-eth-
ylenebis(oxy)bis(5-nitroimino-tetrazolate) (7). The reaction of 318
mg (1.00 mmol) of 1,1′-ethylenebis(oxy)bis(5-nitroimino-tetrazole)
26 with 392 mg (2.00 mmol) 2-amino-1,3-diazido-2-(azidometh-
yl)propane22 in 10 mL water at ambient temperature gave colorless
crystals of 7 (640 mg, 0.943 mmol, 94%) after air drying.
Tdec 151 °C (onset); IR (KBr) ν˜ 3420, 3032, 2931, 2869, 2803,
2114 (N3), 1600, 1536, 1510, 1445, 1425, 1379, 1313, 1283, 1223,
Figure 9. Crystal structure of 1,2,4,5-tetrazino-3,6-bis(hydrazinium)-1,1′-
ethylenebis(oxy)bis(5-nitroimino-tetrazolate) (9)·2H2O: Because of the poor
quality of the crystals (it was not a single crystal), accurate structural data
were not obtained.
1
1080, 963, 880; H NMR δ 8.49 (br s, 6H, NH3+), 4.64 (s, 4H,
CH2), 3.74 (s, 12H, CH2); 13C{1H} NMR δ 150.8, 76.1, 57.7, 51.6;
15N{1H} NMR δ -6.1, -13.9 (NO2), -28.8, -74.7 (N-), -125.5,
-134.9 (Nꢀ), -160.0, -171.1 (Nγ), -317.5 (NR), -336.9 (NH3+);
EA (C12H22N32O6, 710.51) calcd: C, 20.29; H, 3.12; N, 63.08%.
Found: C, 20.72; H, 3.05; N, 62.03%. Caution! During elemental
analysis the compound exploded.
1099, 953, 906, 727; 1H NMR δ 10.63 (br s, 2H, NH), 6.14 (br s,
10H, NH3 and H2O), 4.64 (s, 4H, CH2); 13C{1H} NMR δ 161.2,
+
150.4, 76.2; EA (C6H16N20O8, 496.32) calcd: C, 14.52; H, 3.25; N,
56.44%. Found: C, 14.67; H, 3.16; N, 55.69%.
Carbohydrazinium 1,1′-ethylenebis(oxy)bis(5-nitroimino-tet-
razolate) (8) Tetrahydrate. The reaction of 318 mg (1.00 mmol)
1,1′-ethylenebis(oxy)bis(5-nitroimino-tetrazole) (2) with 90.0 mg
(1.00 mmol) carbohydrazide in 10 mL water at ambient temperature
for 20-min stirring precipitated a white solid, which was filtered
and dried. 8·4H2O (410 mg, 0.854 mmol, 85%). 8·4H2O was
recrystallized with water and formed 8·2H2O as colorless crystals.
Tm 71 (H2O), 78 (H2O), and 129 °C (H2O); Tdec 147 °C (onset);
IR (KBr) νν 3569, 3448, 3348, 3090, 3020, 2956, 2853, 2736, 1707,
1636, 1617, 1524, 1444, 1399, 1362, 1328, 1288, 1272, 1241, 1099,
1,2,4,5-Tetrazino-3,6-bis(hydrazinium)-1,1′-ethylenebis(oxy)-
bis(5-nitroimino-tetrazolate) (9). Light-red solid; Tdec 147 °C
(onset); IR (KBr) ν˜ 3434, 3223, 3080, 2970, 2899, 2633, 2484,
2033, 1624, 1595, 1545, 1518, 1459, 1400, 1319, 1281, 1229, 1094,
1
1053, 975, 944, 888, 774, 721, 571; H NMR δ 10.59 (br s, 2H,
NH), 10.41 (br s, 6H, NH3+), 4.64 (s, 4H, CH2); 13C{1H} NMR δ
161.2, 150.5, 76.2; 15N{1H} NMR δ -0.6 (N2), -7.0 (NO2), -21.8
(N3), -26.7 (N-tetrazine), -72.4 (N-), -118.8 (N1), -153.0 (N5),
-284.7 (NH), -314.8 (NH3+); EA (C6H12N20O6, 460.29) calcd:
C, 15.66; H, 2.63; N, 60.86%. Found: C, 15.77; H, 2.56; N, 60.52%.
Bis(diaminoguanidium) 1,1-ethylenebis(oxy)bis(5-nitroimino-
tetrazolate) (10). To an aqueous solution of 208 mg (1.65 mmol)
diaminoguanidine hydrochloride in 50 mL of H2O was added 440
mg (0.827 mmol) silver 1,1-ethylenebis(oxy)bis(5-nitroimino-
tetrazolate) (5). After stirring at ambient temperature for 4 h, the
silver salt was removed by 3 times filtration, and the solvent was
removed under air. A 410 mg portion (0.826 mmol, 99%) of white
solid 10 was obtained.
1
1044, 902; H NMR δ 9.63 (br s, 2H, NH), 4.64 (s, 4H, CH2),
4.57 (br s, 10H, NH3 and H2O); 13C{1H} NMR δ 157.0, 150.4,
+
76.2; EA (C5H20N16O11, 480.31) calcd: C, 12.50; H, 4.20; N,
46.66%. Found: C 12.52; H, 4.33; N, 46.73%.
Carbohydrazinium 1,1′-Ethylenebis(oxy)bis(5-nitroimino-tet-
razolate) (8) Dihydrate. Colorless crystals; Tm 127 °C (H2O); Tdec
156 °C (onset); IR (KBr) ν˜ 3447, 3235, 3038, 2959, 2923, 2691,
1729, 1634, 1597, 1559, 1524, 1439, 1393, 1341, 1320, 1282, 1240,
1185, 1088, 1027, 899, 853, 772, 621, 528, 441; EA (C5H16N16O9,
444.28) calcd: C, 13.52; H, 3.63; N, 50.44%. Found: C 13.43; H,
3.44; N, 50.23%; Impact sensitivity: 2 J. The structure of 8·2H2O
is supported by single-crystal X-ray analysis.
White solid; Tm 160 °C; Tdec. 164 °C (onset); IR (KBr) ∼ν 3442,
3331, 3274, 2971, 1678, 1512, 1424, 1373, 1319, 1286, 1219, 1088,
1
997, 888, 643, 524; H NMR δ 8.54 (s, 4H, NH2+), 7.13 (s, 4H,
NH), 4.65 (s, 4H, CH2), 4.58 (s, 8H, NH2); 13C{1H} NMR δ 159.9,
150.9, 76.4; 15N{1H} NMR δ 3.2 (N2), -4.7 (NO2), -19.5 (N3),
-64.6 (N-), -116.1 (N1), -150.9 (N5), -278.0 (NH2+), -302.5
(NH), -317.9 (NH2); EA (C6H20N22O6, 496.37) calcd: C, 14.52;
H, 4.06; N, 62.08%. Found: C, 14.58; H, 4.01; N, 61.54%.
Bis(triaminoguanidinium)-1,1-ethylenebis(oxy)bis(5-nitroimino-
tetrazolate) Hydrate (11). To an aqueous solution of 257 mg (2.00
mmol) triaminoguanidine hydrochloride in 50 mL of H2O was
added 532 mg (1.00 mmol) silver 1,1-ethylenebis(oxy)bis(5-
nitroimino-tetrazolate) (5). After stirring at ambient temperature
for 4 h, silver salt was removed by 3 times filtration, and the solvent
was removed under air. A 430 mg portion (0.790 mmol, 79%) of
white solid 11 was obtained.
Carbohydrazinium 1,1′-Ethylenebis(oxy)bis(5-nitroimino-tet-
razolate) (8). White solid; Tdec 130 °C (onset), 146 °C (onset); IR
(KBr) ν˜ 3435, 2967, 2706, 1730, 1612, 1597, 1519, 1438, 1376,
1
1321, 1287, 1093,1023; H NMR δ 9.62 (br s, 2H, NH), 8.63 (br
s, 6H, NH3+), 4.64 (s, 4H, CH2); 13C{1H} NMR δ 157.0, 150.4,
76.2; 15N{1H} NMR δ -0.1 (N2), -6.9 (NO2), -21.6 (N3), -71.1
(N-), -118.6 (N1), -152.9 (N5), -277.3 (NH), -317.1 (NH3+);
EA (C5H12N16O7, 408.25) calcd: C, 14.71; H, 2.96; N, 54.89%.
Found: C 14.64; H, 2.97; N, 54.12%.
1,2,4,5-Tetrazino-3,6-bis(hydrazinium)-1,1′-ethylenebis(oxy)-
bis(5-nitroimino-tetrazolate) (9) Dihydrate. The reaction of 318
mg (1.00 mmol) 1,1′-ethylenebis(oxy)bis(5-nitroimino-tetrazole) (2)
with 142 mg (1.00 mmol) 3,6-dihydrazino-1,2,4,5-tetrazine23 in 50
mL water at ambient temperature for 10 min gave light-red crystals
9·2H2O (410 mg, 0.826 mmol, 83%) after air drying (Figure 9).
Light-red crystals; Tm 72 °C (H2O); Tdec 131 °C (onset); IR (KBr)
ν˜ 3424, 3220, 2849, 1624, 1528, 1447, 1395, 1324, 1281, 1184,
White solid; Tm 95 °C (H2O), 160 °C, Tdec. 162 °C (onset); IR
(KBr) ν˜ 3424, 3342, 3269, 2964, 1686, 1518, 1426, 1316, 1133,
1
1017, 971, 891, 530; H NMR δ 8.56 (s, 6H), 4.63 (s, 4H, CH2),
4.48 (s, 12H); 13C{1H} NMR δ 159.1, 150.9, 76.2;15N{1H} NMR
δ 3.5 (N2), -4.4 (NO2), -19.4 (N3), -64.1 (N-), -115.9 (N1),
-151.0 (N5), -279.2 (NH), -319.6 (NH2); EA (C6H24N24O7,
544.41) calcd: C, 13.24; H, 4.44; N, 61.75%. Found: C, 13.39; H,
4.10; N, 61.37%.
(23) Chavez, D. E.; Hiskey, M. A. J. Heterocycl. Chem. 1998, 35, 1329–
1332.
9
J. AM. CHEM. SOC. VOL. 132, NO. 42, 2010 15089

A R T I C L E S
Joo and Shreeve
Silver 1,1′-Ethylenebis(5-nitroimino-tetrazolate) (12). Silver
nitrate (2.38 g, 14.0 mmol) was dissolved in 50 mL of water and
added to a solution of sodium 1,1-ethylenebis(5-nitroimino-tetra-
zolate), which was obtained 2.00 g (6.99 mmol) 1,1′-ethylenebis(5-
nitroimino-tetrazole) (1)5 and 560 mg (14.0 mmol) sodium hy-
droxide in 100 mL of water. The silver salt precipitated immediately
as a white powder. The suspension was stirred for 5 h under ambient
temperature. The product was filtered and dried with air overnight.
White solid 12 was obtained in a yield of 97% (3.40 g, 1.97 mmol).
White solid; Tdec 270 °C (onset); IR (KBr) ν˜ 3441, 3022, 1629,
1510, 1458, 1434, 1381, 1302, 1229, 1109, 1026, 884, 733, 708;
EA (C4H4Ag2N12O4, 499.89) calcd: C, 9.61; H, 0.81; N, 33.62%.
Bis(triaminoguanidinium)-1,1′-ethylenebis(5-nitroimino-tet-
razolate) Hydrate (14). Method 1. To an aqueous suspension of
1.50 g (3.00 mmol) silver 1,1′-ethylenebis(5-nitroimino-tetrazolate)
(12) in 60 mL H2O was added 843 mg (6.00 mmol) triaminoguani-
dine hydrochloride. After stirring at ambient temperature for 6 h,
silver salts were removed by 3 times filtration, and the solvent was
removed under air. A 1.51 g portion (2.95 mmol, 98%) of colorless
crystals 14 was obtained.
Method 2. The reaction of 572 mg (2.00 mmol) 1,1′-ethyl-
enebis(5-nitroimino-tetrazole) (1) with 316 mg (1.00 mmol) barium
hydroxide octahydrate in 100 mL water at ambient temperature gave
barium 1,1′-ethylenebis(5-nitroimino-tetrazolate) as a white solid
(810 mg, 1.92 mmol, 96%). To an aqueous suspension of 810 mg
(1.92 mmol) barium 1,1′-ethylenebis(5-nitroimino-tetrazolate) in 50
mL H2O was added 588 mg (1.92 mmol) triaminoguanidinium
sulfate. After stirring at 40 °C for 30 min, precipitated barium sulfate
were removed by filtration, and the filtrate was removed under air.
The white crystal 14 (730 mg, 1.42 mmol, 74%) was formed.
Found: C 9.44; H, 0.64; N, 33.01%. Density: 2.974 g cm-3
.
Bis(diaminoguanidinium)-1,1′-ethylenebis(5-nitroimino-tetra-
zolate) (13) Dihydrate. To an aqueous suspension of 1.50 g (3.00
mmol) silver 1,1′-ethylenebis(5-nitroimino-tetrazolate) (12) in 60
mL H2O was added 754 mg (6.01 mmol) diaminoguanidine
hydrochloride. After stirring at ambient temperature for 6 h, silver
salt was removed by 3 times filtration, and the solvent was removed
under air. A 1.37 g portion (2.74 mmol, 91%) of colorless crystal
13·2H2O was obtained.
Colorless crystals; Tm 131 °C (H2O); Tdec 195 °C (onset); IR
(KBr) ν˜ 3613, 3433, 3339, 3216, 3025, 1686, 1605, 1505, 1451,
1424, 1389, 1290, 1252, 1229, 1189, 1142, 1038, 991, 947, 882,
Colorless crystals; Tm 96 (H2O), 202 °C; Tdec 218 °C (onset); IR
(KBr) ν˜ 3557, 3437, 3358, 3314, 3258, 3178, 3074, 2968, 1677,
1636, 1504, 1456, 1436, 1385, 1345, 1303, 1260, 1165, 1105, 1036,
1
775, 741, 652, 596; H NMR δ 8.57 (s, 6H, NH), 4.47 (s, 16H,
CH2, NH2, and H2O); 13C{1H} NMR δ 159.2, 157.1, 44.1; 14N NMR
δ -13.8 (br s, NO2);15N{1H} NMR δ 5.5, -14.4 (NO2), -21.5,
-73.0 (N-), -157.8, -166.7, -288.4, -328.8; EA (C6H24N24O5,
512.41) calcd: C, 14.06; H, 4.72; N, 65.60%. Found: C, 14.10; H,
4.78; N, 65.22%. The structure of 14 is supported by single crystal
X-ray analysis.
1
961, 884, 775, 748, 694, 635, 525; H NMR δ 8.54 (s, 4H), 7.13
(s, 4H), 4.59 (s, 8H, NH2), 4.44 (s, 4H, CH2), 3.35 (s, 4H, H2O);
13C{1H} NMR δ 159.7, 157.0, 43.8; EA (C6H24N22O6, 500.40)
calcd: C, 14.40; H, 4.83; N, 61.58%. Found: C, 14.44; H, 4.63; N,
61.58%. The structure of 13·2H2O is supported by single crystal
X-ray analysis.
Acknowledgment. We gratefully acknowledge the support of
DTRA (HDTRA1-07-1-0024), and ONR (N00014-10-1-0097).
Bis(diaminoguanidinium)-1,1′-ethylenebis(5-nitroimino-tetra-
zolate) (13). White solid; Tm 202 °C; Tdec 220 °C (onset); IR (KBr)
ν˜ 3402, 3322, 3256, 3010, 1686, 1636, 1509, 1471, 1439, 1384,
1348, 1326, 1307, 1263, 1238, 1214, 1175, 1105, 1034, 1025, 965,
Supporting Information Available: X-ray crystallographic
files in CIF format for 2·2H2O, 8·2H2O, 10, 13·2H2O, and 14
1
891, 777, 741, 699, 591; H NMR δ 8.57 (s, 4H), 7.15 (s, 4H),
1
and H, 13C, and 15N NMR spectra of all products. DSC scans
4.60 (s, 8H, NH2), 4.48 (s, 4H, CH2); 13C{1H} NMR δ 159.9, 157.0,
44.1; 14N NMR δ -13.9 (br s, NO2);15N{1H} NMR δ 5.5, -14.5
(NO2), -21.5, -73.2 (N-), -157.7, -166.7, -287.3, -311.7,
-327.1; EA (C6H20N22O4, 464.37) calcd: C, 15.52; H, 4.34; N,
66.36%. Found: C, 15.49; H, 4.29; N, 66.11%.
of all compounds. Complete reference 15. This material is
available free of charge via the Internet at http://pubs.acs.org.
JA107729C
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15090 J. AM. CHEM. SOC. VOL. 132, NO. 42, 2010