Energetic nitrogen-rich derivatives of 1,5-diaminotetrazole

Article abstract of DOI:10.1002/anie.200801886

High-energy-density materials can be obtained by reaction of monosubstituted hydrazines with cyanogen azide to generate 1,5-diaminotetrazole derivatives. Azidohydrazones are postulated as intermediates in this reaction (see scheme). (Chemical Equation Pre

Full text of DOI:10.1002/anie.200801886

Communications
DOI: 10.1002/anie.200801886
Nitrogen-Rich Compounds
Energetic Nitrogen-Rich Derivatives of 1,5-Diaminotetrazole**
Young-Hyuk Joo, Brendan Twamley, Sonali Garg, and Jeanꢀne M. Shreeve*
In recent years 1,5-diamino-1H-tetrazole (1), ditetrazoles 2–5
(Scheme 1), and salt derivatives thereof have been prepared
and characterized in order to determine the properties of
In our continuing interest in the development of energetic
materials, we have now synthesized derivatives of 1,5-
diaminotetrazole in situ by reaction of cyanogen azide[7,8]
with monosubstituted hydrazine derivatives (Scheme 2).
Scheme 1. Examples of reported tetrazoles.
Scheme 2. Synthesis of monosubstituted diamino tetrazoles.
these high-energy-density materials (HEDM).[1] Surprisingly,
substitution of the heterocyclic tetrazole ring with amino
groups is one of the simplest methods to enhance thermal
stability,[2] even though 1 contains 84.0% nitrogen.
The commercially available hydrazine derivatives were
treated with 2 equiv of cyanogen azide dissolved in acetoni-
trile/water (4/1) for 2–24 h to initially give the azidohydra-
zones as intermediate, cyclization of which led to substituted
1,5-diaminotetrazoles 1 and 6–9 in good yields (1: 79, 6: 70, 7:
67, 8: 74, 9: 56%). We emphasize that the synthesis of
cyanogen azide from cyanogen bromide and sodium azide in
dry acetonitrile must be carried out with extreme care (see
Safety Precautions).[7]
Nearly 80 years ago 1 was prepared by treatment of
thiosemicarbazide with lead(II) oxide and sodium azide.[3] In
1984, further investigation into its synthesis and properties
gave 1 in 59% yield.[4] Later, 1 was synthesized by using
aminoguanidinium chloride and HNO2.[5] The reaction mix-
ture was carefully brought to pH 8 with sodium carbonate in
order to deprotonate the amino-substituted azido guanyl
chloride intermediate, which cyclized to form 1 in 58% yield.
However, a further report[6] that appeared in the same year
recommended special caution in the synthesis of 1. This stated
that 1 was pure following ethanol extraction; however, during
extraction by ethanol a very shock sensitive alkali metal salt
of tetrazolyl azide[7] often was observed as a byproduct,
produced by double diazotization of diaminoguanidine with
HNO2.
Cyanogen azide, a colorless oil, was first isolated from the
reaction of sodium azide and cyanogen chloride.[8a] In 1972,
the synthesis of cyanogen azide from sodium azide and
cyanogen bromide, as well as its reactivity, characterization,
and handling, were reported.[8b] During the reaction, traces of
moisture led to the byproducts sodium 5-azidotetrazolate[5,7]
and diazidomethylenecyanamide,[9] which were subsequently
isolated as highly explosive and shock-sensitive solids.
It is noteworthy that the current method can be efficiently
applied to bis(1,5-diaminotetrazole) derivatives (Scheme 3).
Reactions of dihydrazines with 5–6 equiv of cyanogen bro-
mide and an excess of sodium azide led to good yields of
diaminotetrazoles 10–13 (10: 79, 11: 64, 12: 74, 13: 65%).[10]
Removal of the acetonitrile/water solvent (which must be
accomplished by air drying only) from the reaction mixture
was followed by additional washing with small amounts of
acetonitrile and water. The structures of all diamino tetrazole
[*] Dr. Y.-H. Joo, Dr. B. Twamley, S. Garg, Prof. Dr. J. M. Shreeve
Department of Chemistry, University of Idaho
Moscow, ID 83844-2343 (USA)
Fax: (+1)208-885-9146
E-mail: jshreeve@uidaho.edu
[**] The authors gratefully acknowledge the support of DTRA (HDTRA1-
07-1-0024), NSF (CHE-0315275), and ONR (N00014-06-1-1032).
The Bruker (Siemens) SMART APEX diffraction facility was estab-
lished at the University of Idaho with the assistance of the NSF-
EPSCoR program and the M. J. Murdock Charitable Trust, Vancou-
ver, WA (USA). The authors thank Dr. A. Blumenfeld for 15N NMR
spectroscopy measurements.
1
derivatives are supported by IR and H, 13C, and 15N NMR
spectroscopic data as well as elemental analysis (Table 1).
Diamino tetrazoles 8 and 13 were characterized by the
usual spectroscopic methods and by single-crystal X-ray
diffraction analyses.[11] Molecular structures of 8 and 13 are
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/anie.200801886.
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Chemie
Scheme 3. Synthesis of bis(1,5-diaminotetrazole) derivatives.
Table 1: Selected physical data of diamino tetrazole derivatives.[a]
10: colorless crystal; IR (KBr): n˜ =3331, 3146, 1707, 1659 cmÀ1; 1H NMR
([D6]DMSO): d=7.01 (s, 4H; NH2), 11.09 ppm (brs, 2H; NH);
13C NMR ([D6]DMSO): d=152.5 (s), 154.8 ppm (s); 15N NMR
([D6]DMSO): d=À331.9 (t, 1JNH =89.3 Hz; NH2), À269.3 (brs; NH),
À172.8 (N1), À94.6 (N4), À19.4 (N3), 4.2 ppm (N2); elemental analysis
(%): calcd for C3H6N12O (226.16): C 15.93, H 2.67, N 74.32; found
C 16.27, H 2.77, N 72.71.
Figure 1. Molecular structures (hydrogen atoms shown as spheres of
arbitrary radius and thermal displacement set at 30% probability) of 8
(top) and 13 (bottom). Solvent molecules in 13 have been omitted for
clarity and only symmetry unique atoms are labeled. Selected bond
11: white solid; IR (KBr): n˜ =3402, 3339, 3283, 3223, 3183, 1738, 1661,
1
1452, 1115, 1075, 672 cmÀ1; H NMR ([D6]DMSO): d=7.13 (s, 4H;
NH2), 12.71 ppm (s, 2H; NH); 13C NMR ([D6]DMSO): d=154.3 (s),
156.9 ppm (s); elemental analysis (%): calcd for C4H6N12O2 (254.17):
C 18.90, H 2.38, N 66.13; found C 19.21, H 2.36, N 65.65.
À
À
À
lengths [ꢀ] and angles [8]: 8: C2 N3 1.332(2), N3 N4 1.384(2), N4
À
À
À
N5 1.284(2), N5 N6 1.369(2), N6 N7 1.3654(19), N7 C8 1.394(2),
À
À
C8 N9 1.337(2), N9 N10 1.409(2); N6-N7-C8 117.51(14), C8-N9-N10
119.21(15); 13: C2 N3 1.3250(16), N3 N4 1.3739(16), N4 N5
1.2835(16), N5 N6 1.3681(14), N6 N7 1.3807(14), N7 C8
1.3843(16), C8 N9 1.3403(16), N9 N10 1.3225(15); N6-N7-C8
115.13(10).
12: white solid; IR (KBr): n˜ =3412, 3327, 3291, 3213, 3000, 1717, 1649,
1
1584, 1518, 1331, 1254, 598 cmÀ1; H NMR ([D6]DMSO): d=6.80 (s,
À
À
À
4H; NH2), 9.13 (s, 2H; NH), 10.75 ppm (brs, 2H; NH); 13C NMR
([D6]DMSO): d=154.9 (s), 155.4 ppm (s); 15N NMR ([D6]DMSO):
d=À332.9 (t, 1JNH =89.1 Hz, NH2), À276.0 (d, 1JNH =91.3 Hz, NH),
À270.4 (brs, NH), À172.1 (N1), À96.2 (N4), À18.2 (N3), 1.7 ppm (N2);
elemental analysis (%): calcd for C4H8N14O2 (284.20): C 16.90, H 2.84,
N 69.00; found C 16.88, H 2.95, N 67.21.
À
À
À
À
À
In the 15N NMR spectrum of 13 seven signals were
observed (Figure 2). A broad signal assigned to NH appeared
at d = À279.6 ppm, due to the positive nuclear Overhauser
effect resulting from the directly bonded protons in the H-
decoupled 15N NMR spectrum. By using heteronuclear single
quantum correlation (HSQC), the coupling constant of NH2
(1J(15N,1H) = 85.5 Hz) was determined; however, because the
13: orange solid; IR (KBr): n˜ =3385, 3298, 3256, 3192, 3026, 2936, 2843,
1
1655, 1558, 1483, 1431, 1332, 1112, 1061, 953, 560 cmÀ1; H NMR
([D6]DMSO): d=7.06 (s, 4H; NH2), 11.98 ppm (brs, 2H; NH);
13C NMR ([D6]DMSO): d=154.9 (s), 161.1 ppm (s); 15N NMR
1
([D6]DMSO): d=À332.24 (t, JNH =85.5 Hz; NH2), À279.6 (brs; NH),
À171.7 (N1), À93.0 (N4), À30.0 (N-tetrazine), À19.7 (N3), 6.2 ppm
(N2); elemental analysis (%): calcd for C4H6N16 (278.20): C 17.27,
H 2.17, N 80.56; found: not determinable (explodes).
[a] 1H, 13C and 15N NMR (CH3NO2 as external standard) spectra were
recorded at 300.1 MHz, 75.5 MHz and 50.7 MHz, respectively. The data
for 6, 7, 8, 9, 11·2H2O and 12·4H2O are summarized in the Supporting
Information.
shown in Figure 1. Structural details are given in the
Supporting Information.
The extended structure of compound 8 is a complex 3D
network formed by H-bonding (N9···N3_#1 2.968(2),
N10···O1_#2 2.993(2) Š; symmetry transformation #1 x + 1/
2, Ày + 1/2, z + 1/2; #2 = x + 1/2, y + 1/2, z). Compound 13
forms a hydrogen-bonded chain involving amino H atoms and
the cocrystallized DMSO solvent molecule (N1···O2_#3
2.969(1), N7···O1_#4 2.700(1); symmetry transformation
#3 = x + 1, Ày + 1, Àz + 1; #4 = Àx + 1, Ày + 1, Àz). Addition
of DMSO was necessary to produce a crystal of 13 for
structural analysis.
Figure 2. 15N NMR spectra of 13. Top: decoupled (delay of 10 s
between pulses). Bottom: coupled (delay of 60 s between pulses).
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NH proton signal is very broad, the value of its 15N,1H
coupling constant was not determined. The assignments are
based on the 15N NMR data and comparison with phenyl-
diaminotetrazole 7.[5,12]
Keywords: azides · cyclization · energetic materials ·
nitrogen heterocycles
.
Density is one of the most important physical properties
of energetic materials. The densities of most of the new
diamino tetrazoles range between 1.44 and 1.65 gcmÀ3
(Table 2). The decomposition temperatures lie in the range
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Levchik, A. I. Balabanovich, P. N. Gaponik, A. A. Kulak,
Thermochim. Acta 2002, 388, 233 – 251.
Table 2: Physical properties of diamino tetrazole derivatives.
[c]
Compd Td[a] Density[b] DfH2ꢀ98
DfHꢀ298 P[d,e]
vD[e,f]
IS[g]
[J]
[8C] [gcmÀ3
]
[kJmolÀ1
]
[kJgÀ1
]
[GPa]
[msÀ1
]
6
7
8
195 1.44
193 1.44
209 1.65
214 1.58
223 1.65
232 1.65
215 1.63
209 1.62
374.2
497.7
283.1
134.7
639.1
498.6
523.4
1289.1
3.28
2.82
1.79
0.72
2.83
1.96
1.84
4.63
19.00
14.17
23.86
7600
6739
8364
>60
>60
>60
9
18.19[h] 7285[h] >60
10
11
12
13
24.06
21.15
21.49
24.98
8255
7767
7886
8331
25
25
25
[3] R. StollØ, E. Gaertner, J. Prakt. Chem. 1931, 132, 209 – 226.
[4] P. N. Gaponik, V. P. Karavai, Chem. Hetetrocycl. Compd. 1984,
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1.5
[a] Thermal decomposition temperature under nitrogen gas (DSC,
108CminÀ1). [b] Gas pycnometer (258C). [c] Heat of formation (calcu-
lated with Gaussian03). [d] Detonation pressure. [e] Using
83.68 kJmolÀ1 for the enthalpy of sublimation for each compound.
[f] Detonation velocity. [g] Impact sensitivity (BAM Fallhammer).
[h] Using CHEETAH 4.0.
[5] J. C. Galvez-Ruiz, G. Holl, K. Karaghiosoff, T. M. Klapötke, K.
Loehnwitz, P. Mayer, H. Noeth, K. Polborn, C. J. Rohbogner, M.
Suter, J. J. Weigand, Inorg. Chem. 2005, 44, 4237 – 4253.
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Loehnwitz, P. Mayer, H. Noeth, K. Polborn, C. J. Rohbogner, M.
Suter, J. J. Weigand, Inorg. Chem. 2005, 44, 5192.
[7] F. D. Marsh, J. Org. Chem. 1972, 37, 2966 – 2969.
[8] a) F. D. Marsh, M. E. Hermes, J. Am. Chem. Soc. 1964, 86, 4506 –
4507; b) J. E. McMurry, A. P. Coppolino, J. Org. Chem. 1973, 38,
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Lang, Angew. Chem. 2007, 119, 1187 – 1190; Angew. Chem. Int.
Ed. 2007, 46, 1168 – 1171.
193–2328C, and compounds 10, 11, and 13 explode at their
decomposition temperatures (differential scanning calorim-
etry, DSC). The heats of formation of 6–13 were calculated
with Gaussian03[13] (Table 2) by using the method of isodes-
mic reactions (Supporting Information). The enthalpy of an
isodesmic reaction (DHr298) is obtained by combining the
MP2/6-311 + + G** energy difference for the reaction, the
scaled zero-point energies, and other thermal factors.
All of the diamino tetrazole derivatives have positive
heats of formation, and that of 13 is the highest
(1289 kJmolÀ1). By using the calculated heats of formation
and the experimental densities of new substituted diamino
tetrazoles 6–13, the detonation pressures P and detonation
velocities D were calculated by means of traditional Chap-
man–Jouget thermodynamic detonation theory by using
Cheetah 5.0.[14] Impact sensitivities of the diamino tetrazoles,
tested with a BAM Fallhammer (Table 2), range from
insensitive (6–9: > 60 J) through sensitive (10–12: 25 J) to
very sensitive (13: 1.5 J).[15]
[9] a) C. V. Hart, J. Am. Chem. Soc. 1928, 50, 1922 – 1930; b) A.
Hantzsch, Chem. Ber. 1933, 66, 1349 – 1354.
[10] Preparation of cyanogen azide was based on
a modified
literature method.[7,8a] At 08C, cyanogen bromide (1.30 g,
12.3 mmol) was dissolved in dry acetonitrile (20 mL) and
sodium azide (3.82 g, 58.8 mmol) was added. The reaction
mixture was stirred at 0–158C for 4 h. The inorganic salt was
filtered off (Caution! After filtering, the salt must be quickly
dissolved in cold water). The solution was added to a suspension
containing
3,6-dihydrazinyl-1,2,4,5-tetrazine[10b]
(100 mg
(0.704 mmol) in water (10 mL) at 08C. After 4 d[10c] of stirring
at ambient temperature, the suspension was filtered to leave an
orange filter cake, which was dried in air. Compound 13 was
obtained (127 mg, 0.457 mmol, 65%). a) The unknown salt
which is formed is likely the azidotetrazolate salt.[7] b) Synthesis
of 3,6-dihydrazinyl-1,2,4,5-tetrazine: D. E. Chavez, M. A.
Hiskey, J. Heterocycl. Chem. 1998, 35, 1329 – 1332. c) Each
compound required a different reaction time (1: 4 h, 6: 2 h, 7:
2 h, 8: 24 h, 9: 3 d, 10: 2 d, 11: 4 d, 12: 24 h, 13: 4 d).
[11] Crystallographic data: 8: (C2H6N8O): Mr = 158.15; crystal size
0.28 ” 0.25 ” 0.13 mm; monoclinic, space group Cc, a =
11.2323(7), b = 4.6153(3), c = 11.9898(7) Š, b = 91.413(1)8, V=
621.37(7) Š3, Z = 4, 2qmax = 588, 829 independent reflections,
R1 = 0.0281 for 814 reflections with I > 2s(I) and wR2 = 0.0766,
100 parameters. 13: (C12H30N16O4S4): Mr = 590.76; crystal size
Safety Precautions
Pure cyanogen azide is extremely dangerous.[7] Therefore, when
utilizing the substance as a reactant, it must always be dissolved in a
solvent to give a dilute solution. Manipulations must be carried out in
a hood behind a safety shield. Leather gloves must be worn. While we
have experienced no difficulties with the shock instability of the 1,5-
diaminotetrazole derivatives, they should be synthesized only in
amounts of 1–2 mmol, and extreme care is necessary, particularly for
compound 13.
¯
0.44 ” 0.23 ” 0.14 mm; triclinic, space group P1, a = 8.6351(5),
b = 9.0007(5), c = 9.5097(6) Š, a = 92.8441(8), b = 111.4645(7),
g = 103.7774(8)8, V= 660.37(7) Š3, Z = 1, 2qmax = 528, 2606
independent reflections, R1 = 0.0258 for 2482 reflections with
I > 2s(I) and wR2 = 0.0747, 179 parameters. CCDC-684330 and
CCDC-684331 contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge from
Received: April 22, 2008
Published online: July 9, 2008
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Angewandte
Chemie
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[14] S. Bastea, L. E. Fried, K. R. Glaesemann, W. M. Howard, P. C.
Souers, P. A. Vitello, CHEETAH 5.0 Userꢀs Manual, Lawrence
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[15] Classification of impact sensitivities from reference [5] (insensi-
tive: > 40 J; less sensitive: ꢁ 35 J; sensitive: ꢁ 4 J; very sensitive:
ꢂ 3 J).
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