Bistetrazolylamines - Synthesis and characterization

Article abstract of DOI:10.1039/b811273h

The acid-catalyzed cyclization reaction of sodium dicyanamide and sodium azide in the ratio of 1: 2 afforded 5,5′-bis(1H-tetrazolyl)amine (H ₂bta, 2) in high yield (88%) as the monohydrate. Dehydration of 2·H₂O at elevated temperatur

Full text of DOI:10.1039/b811273h

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PAPER
www.rsc.org/materials | Journal of Materials Chemistry
Bistetrazolylamines—synthesis and characterization†
a
a
a
b
Thomas M. Klap o¨ tke,* Peter Mayer, J o¨ rg Stierstorfer and Jan J. Weigand
Received 2nd July 2008, Accepted 16th August 2008
First published as an Advance Article on the web 1st October 2008
DOI: 10.1039/b811273h
The acid-catalyzed cyclization reaction of sodium dicyanamide and sodium azide in the ratio of 1 : 2
0
afforded 5,5 -bis(1H-tetrazolyl)amine (H
2
bta, 2) in high yield (88%) as the monohydrate. Dehydration
of 2$H
DMSO yielded 2$H
) in two steps. In the first step, 2 was twice deprotonated with sodium hydroxide and alkylated with
2
O at elevated temperature and reduced pressure gave anhydrous 2, while recrystallization from
0
2
O$DMSO. 2 was converted into 5,5 -bis(2-methyltetrazolyl)methylamine (Me bta,
3
6
0
MeI producing 5,5 -bis(2-methyltetrazolyl)amine (Me bta, 5) in moderate yield (55%). The second step
2
involved the alkylation of 5 with dimethyl sulfate in alkaline solution (72%). In all cases, the obtained
colorless, crystalline compounds were fully characterized by vibrational (IR, Raman) spectroscopy,
multinuclear NMR spectroscopy, mass spectrometry, elemental analysis, X-ray structure
determination, and initial safety testing (impact, friction and electrical spark sensitivity). According to
the UN Recommendations for the ‘‘Transport of Dangerous Goods’’, compounds 2$H
2
O, 5, and 6 are
classified as ‘‘insensitive’’ while 2 is described as ‘‘sensitive’’. The thermal behaviors were investigated
ꢁ1
ꢀ
using differential scanning calorimetry (DSC). The heats of formation (D Hm (2*H O) ¼ 203 kJ mol ,
f
2
ꢀ
ꢁ1
ꢀ
ꢁ1
ꢀ
m
ꢁ1
D H (2) ¼ 633 kJ mol , D H (5) ¼ 350 kJ mol , D H (6) ¼ 583kJ mol ) were calculated using
f
m
f
m
f
ꢁ1
ꢁ1
heats of combustion (D
H (2$H O) ¼ ꢁ1714 kJ mol , D
H (2) ¼ ꢁ1858 kJ mol , D
H
comb.
comb.
2
comb.
ꢁ1
ꢁ1
(
5) ¼ ꢁ2932 kJ mol , Dcomb.H (6) ¼ ꢁ3843 kJ mol ) obtained from oxygen bomb calorimetry.
ꢁ1
In addition, explosion parameters such as the detonation velocity (D(2$H
ꢁ1
2
O) ¼ 7792 m s ,
ꢁ1
ꢁ1
D(2) ¼ 9120 m s , D(5) ¼ 7291 m s , D(6) ¼ 7851 m s ) and detonation pressure (P(2$H O) ¼
2
2
20 kbar, P(2) ¼ 343 kbar, P(5) ¼ 172 kbar, P(6) ¼ 205 kbar) were calculated using the program
EXPLO5. ‘‘Koenen tests’’ were successfully performed for compound 2 using critical diameters of 8 mm
and 10 mm.
Introduction
hydrazinium, and guanidinium derivatives were recently
20
published as energetic materials. The parent compound has
21
only been sparingly described in the literature. To date, there
1
In the continuous search for novel, green, energetic materials
2,3
with high nitrogen but low carbon content, several groups
3
are no reports on tris(tetrazolyl)amine (3, H tta). This may be
around the world are currently investigating HEDMs (High
4
Energy Dense Materials), based on tetrazoles. These energetic
due to the influence of electronic and/or steric factors which
prohibit a viable synthesis.
materials are applicable in low-smoke producing pyrotechnic
8
Two synthesis protocols are used for the preparation of 1: the
17
conversion of aminoguanidinium salts with nitrous acid and the
5
6
7
compositions, gas generators, propellants, high explosives,
9
and primers in primer charges (PC). Tetrazoles,
10,11
tetrazo-
acid-catalyzed cycloaddition of hydrazoic acid with dicyano-
22
diamide. The latter reaction is a general protocol for the
12,13
late,
14,15
and tetrazolium
salts are of special interest. In
particular, certain derivatives of tetrazolylamines display low
sensitivities and high thermal stabilities.
formation of tetrazole derivatives since both neutral azides and
the azide anion can undergo cycloaddition with cyano groups. In
this way, a broad range of different tetrazole derivatives have
The mono-substituted tetrazole 5-aminotetrazole (1, 5-at)
represents a valuable building-block for the preparation of
23
been achieved. A suitable precursor for the synthesis of 2 is the
ꢁ
16
tetrazole-based high energetic materials and was first described
0
non-linear pseudohalide dicyanamide anion (N(CN)
2
). The first
17
by Thiele in 1892. Metal salts of 5,5 -bis(1H-tetrazolyl)amines
synthesis of 2, obtained as a monohydrate, was described by
(
2, H bta) were described as useful colorants in pyrotechnic
2
Norris and Henry by refluxing sodium dicyanamide, sodium
24
azide, and trimethylammonium chloride in water. Currently,
18
19
compositions by Highsmith et al. and Hiskey et al. In
addition, several nitrogen-rich salts such as ammonium,
a
Energetic Materials Research, Ludwig-Maximilian University of Munich,
Department of Chemistry and Biochemistry, Butenandtstr. 5-13, 81377
Munich, Germany. E-mail: tmk@cup.uni-muenchen; Fax: +49 89 2180
7
7491
b
WWU M u¨ nster, IAAC, Corrensstr. 28/30, D-48149 M u¨ nster, Germany
CCDC reference numbers 299051 (2), 687771 (2$H O), 687768
2$H O$DMSO), 687770 (5) and 687769 (6). For crystallographic data
in CIF or other electronic format see DOI: 10.1039/b811273h
†
2
(
2
5
248 | J. Mater. Chem., 2008, 18, 5248–5258
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ꢀ
Scheme 2 Preparative route to 2; i) EtOH–H
ꢀ
2
O, 2 M HCl. 80 C; ii) 120
ꢁ3
C, 10 Torr.
Scheme 1 Protocols for the synthesis of 2.
there are three synthesis procedures for 2: (1) the in situ reaction
of hydrazoic acid (prepared from sodium azide and a weak
acid like trimethylammonium chloride, boric acid, ammonium
2
Scheme 3 Preparative route to 5 and 6; i) NaOH, H O, MeI–acetone, 60
ꢀ
2 2 4
C; ii) NaOH, H O, Me SO , reflux.
25
chloride) with sodium dicyanamide, (2) the reaction of sodium
dicyanamide with sodium azide in the presence of a catalyst
like zinc chloride, bromide or perchlorate, followed by an
MeOH or EtOH when heated. 2$H O is soluble in water or
2
26
acidic work-up, and (3) the reaction of 1 with cyanogen
mineral acids (e.g. HCl or HClO ) when warmed. Anhydrous 2 is
4
bromide under base-catalyzed conditions forming the 5-cyani-
24,27
ꢁ3
obtained when 2$H O is dehydrated under vacuum (24 h, 10
2
2ꢁ
minotetrazolinediide anion (4, cit ),
followed by a subse-
ꢀ
Torr) at elevated temperature (120 C).
quent cycloaddition of hydrazoic acid under acidic conditions
2
Our two-step synthesis of 6 starts from 2$H O (Scheme 3). In
(
Scheme 1).
the first step, neutralization of an aqueous solution of 2 with two
ꢀ
Surprisingly, 2 has only been poorly characterized and the
equiv. sodium hydroxide at 60 C and addition of two equiv. MeI
chemistry of methyl derivatives of 2 has not been investigated.
in acetone yields the dimethylated product 5 after 12 h of
ꢀ
Therefore, we wish to report a modified synthesis and full
0
refluxing and further cooling to 4 C. The obtained precipitate
characterization of 5,5 -bistetrazolylamine 2 and its mono-
was recrystallized from dilute HCl affording pure 5. Interest-
ingly, when the methylation was performed with dimethyl
sulfate in lieu of MeI, a mixture of 1- and 2-methylated isomers
hydrate 2$H
2
O. Furthermore, the recrystallization of 2$H
2
O in
DMSO resulted in the formation of 2$H
presenting the results of the methylation reaction of 2 with MeI
2
O$DMSO. We are also
0
0
0
was obtained. However, the 1,1 -, 1,2 -, and 2,2 -isomers were
13
detected in the C NMR spectrum of the reaction mixture. In the
0
under basic conditions yielding 5,5 -bis(2-methyltetrazolyl)amine
2
8
(
5, Me
2
bta) as the main product. The subsequent reaction of 5
0
second step, 6 was obtained in 62% yield through methylation of
5 with an excess of dimethyl sulfate in refluxing aqueous sodium
hydroxide solution. 6 is soluble in common solvents, e.g.,
ethanol, acetone, and acetonitrile, and was recrystallized from
hot water yielding colorless needles.
with Me SO under basic conditions afforded 5,5 -bis(2-meth-
2
4
yltetrazolyl)methylamine (6, Me bta) in good yields. All
3
compounds were obtained in high purities as colorless, crystal-
line materials. The molecular structures of all compounds were
confirmed by means of X-ray investigations at low temperature.
Initial safety testing and energetic properties are reported. The
cheap and facile synthesis route, high thermal stability, and low
sensitivities of 2 and its derivatives bode well for the application
of these compounds for use in novel propellant systems, pyro-
0
The 5,5 -bistetrazolylamines 2, 5, and 6 were characterized and
identified by IR, Raman, and NMR spectroscopies and by
1
elemental analysis. The H and C NMR experiments were
13
1
measured in [d ]-DMSO at RT. The H NMR spectrum for 2
6
depicts a broad resonance (due to fast proton exchange)
32
appearing at 11.92 ppm, a typical value for tetrazole protons.
29
technic formulations and/or in high-energy-capacity transition
30
metal complexes.
The proton of the secondary amine is deshielded due to electronic
effects of the tetrazole substituent and appears at 9.53 ppm. After
methylation of 2, the proton of the secondary amine in 5 is
further deshielded and appears at 10.91 ppm. The range of
resonances for methyl substituents is consistent with literature
Results and discussion
Synthesis and characterization
33
data and these protons are more deshielded for the methyl-
In contrast to the previously reported synthesis of 2$H
O is obtained in high yields and high
2
O by
azoles (4.27 (5) and 4.29 (6) ppm) than for the tertiary amine in 6
13
(3.60 ppm). The C chemical shift can be used to distinguish
2
4
Norris and Henry, 2$H
2
purity by the reaction of sodium dicyanamide with two equiv. of
sodium azide and hydrochloric acid (Scheme 2). The reaction
was performed in an aqueous ethanolic solution by slow addition
between 1,5- and 2,5-disubstituted tetrazoles. The chemical shift
for the tetrazole carbon atom in the 2,5-isomers is found at
a higher frequency, typically with values greater than 160 ppm
(162.7 (5) and 164.6 (6) ppm) for methyl derivatives. The
resonances of C-5 for the corresponding 1,5-isomers are expected
to range from 145 to 160 ppm. Similar results are observed for
the methyl group shifts. Once again, the 2,5-isomers display
ꢀ
of diluted hydrochloric acid at 80 C over the course of 4 h and
31
subsequent refluxing of the reaction mixture for a further 48h.
Compound 2$H O is insoluble in common organic solvents such
as CH Cl , diethyl ether or THF and dissolves only poorly in
2
2
2
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J. Mater. Chem., 2008, 18, 5248–5258 | 5249

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1
5
15
N NMR chemical shifts (d, ppm) and N– H NMR coupling
1
Table 1
constants (Hz) for compounds 2, 5 and 6
N-1
N-2
N-3
N-4
N-5
a
b
2
5
ꢁ123.8
ꢁ17.9
—
ꢁ11.3 q,
—
ꢁ109.2
ꢁ315.7
ꢁ316.4
ꢁ110.2 q,
ꢁ111.5 q,
3
2
3
J ¼ 1.9
J ¼ 2.1
J ¼ 1.9
a
6
ꢁ104.0 q,
ꢁ110.5 q,
ꢁ5.2 q,
ꢁ76.2
ꢁ324.5 q,
3
2
3
2
J ¼ 1.9
J ¼ 2.2
J ¼ 1.9
J ¼ 2.2
a
b
6 3
In [d ]-DMSO. In CF COOH.
higher resonances (40.1 (5) and 40.3 (6) ppm) compared to those
34
expected for the more shielded 1,5-isomers.
15
15
1
The N NMR shifts and the absolute values of the N, H
NMR coupling constants are presented in Table 1. The spectra of
compounds 2, 5, and 6 are depicted in Fig. 1. Our assignments
15
1
were mainly based on the analysis of the N– H NMR coupling
2
Fig. 2 Raman spectra of compounds 2$H O, 2, 5 and 6.
patterns and on previous investigations. In agreement with the
15
correlations between N NMR chemical shifts and electron
1
5
densities at the nitrogen atoms, the N NMR chemical shifts
38
$H O. The IR and Raman spectra of the investigated
2
2
become increasingly more negative for 2,5-disubstituted tetra-
compounds have in common the bands for the stretching
ꢁ1
1
4,16,34,35
zoles: N-3 < N-4 < N-1 < N-2.
In the proton-coupled
and bending modes of the C–H (2950–3150 cm ) and N–H
ꢁ1
spectra of 5 and 6, the N-1, N-2, and N-3 signals appear as
(
3300–3450 cm ) groups from the protons of the tetrazole ring
15
quartets with N–H coupling constants that are similar in
magnitude, resulting from coupling to protons of the N-Me
group. For 6, the N-5 signal also appears as a quartet due to
coupling to protons of the C-Me group.
and of the secondary amino group.
Molecular structures
Vibrational spectroscopy is another suitable method for
identifying bistetrazolylamines. The IR and Raman spectra
Crystallographic and structural refinement data for compounds
2 2
2$H O, 2$H O$DMSO, 2, 5, and 6 are listed in Table 2 and
(
Fig. 2) of the investigated compounds are characteristic for
selected bond lengths and angles are included in Table 3. Tables
of atomic coordinates, thermal displacement parameters, and
a complete list of bond angles and distances can be obtained from
ESI†. Suitable crystals for the X-ray investigations were
36
5
-aminotetrazoles. Assignments were performed with the help
of a frequency analysis after calculating (B3LYP/cc-pVDZ) the
37
optimal geometry with the Gaussian03 software. Compared to
ꢁ1
the characteristic bands located at 1656 and 1556 cm , assigned
produced by recrystallization of 2$H
aqueous HClO solutions (20%). X-Ray quality crystals of
$H O$DMSO were acquired from warm DMSO solution and
2
O and 5 from warm
to the nasym(Ctet–N–Ctet) and nsym(Ctet–N–Ctet) stretching vibra-
4
2
tions in 2$H O, the corresponding bands are shifted to lower
frequencies in the methylated compounds by approximately 8 to
2
2
from water for 6. Single crystals of 2 were obtained from an
organic tetranitromethane solution through a failed attempt to
nitrate the secondary amine.
ꢁ
1
1
2 cm . Further bands can be attributed to the stretching
ꢁ1
ꢁ1
vibrations of the N]N (1454 cm ), C]N (1352, 1337 cm ),
ꢁ1
and N–N (1282, 1268 cm ) bonds in the vibrational spectra of
2 1
2$H O (Fig. 3) crystallizes in the monoclinic space group P2 /c
with four molecules in the unit cell. Interestingly, the biste-
trazolylamine molecules are planar (torsion angle C1–N1–C2–
ꢀ
N9 ¼ ꢁ179.6(1) ). The C–N bond distances to the amine
˚
nitrogen show lengths of N1–C1 ¼ 1.370(2) A and N1–C2 ¼
˚
.360(2) A and are significantly shorter than C–N single bonds
1
˚
1.47 A) suggesting that, in addition to the planar geometry,
(
there is a delocalization of the amine lone pair. The bond
distances in the tetrazole rings are in the typical range of
˚ ˚
1
.29–1.36 A between N–N single bonds (1.45 A) and N]N
˚
39
double bonds (1.25 A) and are given in Table 2.
$H O forms a layer structure involving several hydrogen
bonds (Fig. 4). The strongest hydrogen bond is found between
2
2
the water oxygen atom and the ring nitrogen (N2–H1/O1,
˚
˚
D–H ¼ 0.94(2), H–A ¼ 1.69(2) A, D–A ¼ 2.623(2) A, D–H–A ¼
ꢀ
1
77(2) ). Both water hydrogen atoms are directed to further
bistetrazolylamine molecules with ‘‘D–A hydrogen bond
˚
distances’’ of about 2.8 A. The distance between the layers is
˚
ca. 3.35 A.
15
Fig. 1
N NMR spectra of compounds 2, 5 and 6.
5
250 | J. Mater. Chem., 2008, 18, 5248–5258
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Table 2 Crystallographic data and parameters
2
2$H
2
O
2$H
2
O$DMSO
OS
5
6
Formula
C
153.13
2
H
3
N
9
C
2
H
5
N
9
O
C
249.54
4
H
11
N
9
C
4
H
N
7 9
C
5 9 9
H N
ꢁ
1
Formula weight/g mol
Crystal system
Space group
Color/habit
171.15
Monoclinic
P2 /c (14)
181.19
Monoclinic
P2 /c (14)
colorless needles
0.08 ꢂ 0.16 ꢂ 0.23
10.279(2)
11.338(2)
6.772(1)
90
195.21
Monoclinic
P2 /m (11)
colorless rods
0.12 ꢂ 0.15 ꢂ 0.26
3.852(1)
19.395(5)
5.769 (2)
90
Orthorhombic
Pbca (61)
colorless needles
0.05 ꢂ 0.06 ꢂ 0.19
11.109(2)
9.227(2)
21.327(4)
90
Monoclinic
C2/c (15)
colorless rods
0.04 ꢂ 0.11 ꢂ 0.11
15.933(1)
6.8863(6)
19.920(2)
90
1
1
1
colorless plates
0.04 ꢂ 0.10 ꢂ 0.15
9.367(2)
10.531(2)
6.808(1)
90
Size/mm
˚
a/A
˚
b/A
˚
c/A
ꢀ
a/
ꢀ
b/
90
90
2186.1(7)
16
1.861
0.147
1248
0.71073
200
90.42(3)
90
671.6(2)
4
1.693
0.140
352
0.71073
200
104.227(7)
90
2118.6(3)
8
1.563
0.312
1040
0.71073
200
4.3, 25.5
ꢁ19 : 19; ꢁ8 : 8;
ꢁ24 : 24
9776
1965
0.029
1846
165
0.0406
0.1067
1.11
94.74(3)
90
786.5(3)
4
1.530
0.115
376
0.71073
200
95.60(3)
90
428.9(2)
2
1.512
0.112
204
0.71073
200
ꢀ
˚
g/
V/A
3
Z
r
ꢁ
3
calc./g cm
m/mm
F(000)
lMoKa/A
T/K
Min,qMax
ꢁ
1
˚
ꢀ
q
/
3.5, 26.5
ꢁ13 : 13; ꢁ11 : 11;
3.6, 27.4
ꢁ12 : 12; ꢁ13 : 13;
ꢁ8 : 8
3.5, 27.5
ꢁ13 : 13; ꢁ14 : 14;
ꢁ8 : 8
4.1, 26.0
ꢁ4 : 4; ꢁ17 : 23;
ꢁ6 : 7
Dataset
ꢁ
26 : 26
4201
2257
Reflections collected
Independent reflections
2966
1529
0.019
3457
1803
0.023
2226
862
0.033
R
int
0.026
1618
223
0.0396
0.1022
1.06
ꢁ0.28, 0.25
Nonius
Kappa CCD
SHELXS-97
SHELXL-97
none
Observed reflections
Parameters
1257
129
0.0367
0.0998
1.08
ꢁ0.28, 0.19
Nonius
Kappa CCD
SIR-92
SHELXL-97
none
1383
146
0.0407
0.1171
1.14
ꢁ0.26, 0.19
Nonius
Kappa CCD
SHELXS-97
SHELXL-97
None
724
86
0.0570
0.1353
1.18
ꢁ0.23, 0.22
Oxford
Xcalibur3 CCD
SIR-92
SHELXL-97
multi-scan
687769
R
1
(obs)
(all data)
GooF
wR
2
˚
ꢁ3
Resd. Dens./e A
Device type
ꢁ0.34, 0.34
Oxford
Xcalibur3 CCD
SIR-92
SHELXL-97
multi-scan
687768
Solution
Refinement
Absorption correction
CCDC
299051
687771
687770
˚
ꢀ
2
3 Bond lengths [A] and bond angles [ ] of 2, 2$H O,
O$DMSO, 5 and 6
Table
$H
2
2
2
2$H
2
O
2$H
2
O$DMSO
5
6
N1–C1
N1–C2
C1–N2
C1–N5
N2–N3
N3–N4
N4–N5
C2–N6
C2–N9
N6–N7
N7–N8
N8–N9
N3–C3
N7–C4
N1–C5
1.365(2) 1.370(2) 1.351(2)
1.366(2) 1.360(2) 1.358(2)
1.339(2) 1.330(2) 1.326(2)
1.317(2) 1.320(2) 1.316(2)
1.350(2) 1.353(2) 1.346(2)
1.287(2) 1.290(2) 1.278(2)
1.368(2) 1.360(2) 1.360(2)
1.339(2) 1.338(2) 1.322(3)
1.319(2) 1.323(2) 1.312(2)
1.352(2) 1.358(2) 1.348(2)
1.287(2) 1.286(2) 1.284(2)
1.371(2) 1.364(2) 1.361(2)
1.366(2) 1.381(2)
1.371(2) 1.381(2)
1.329(2) 1.326(3)
1.354(2) 1.354(3)
1.347(2) 1.342(3)
1.307(2) 1.307(3)
1.329(2) 1.328(3)
1.327(2) 1.326(3)
1.349(2) 1.354(3)
1.344(2) 1.342(3)
1.312(2) 1.307(3)
1.327(2) 1.328(3)
1.457(2) 1.454(3)
1.451(2) 1.454(3)
1.468(4)
C1–N1–C2 123.3(2) 122.5(1) 123.6(2)
N2–C1–N1 122.5(2) 124.4(1) 127.7(2)
N2–C1–N5 109.5(2) 110.2(1) 108.9(2)
N1–C2–N6 122.1(2) 126.8(1) 124.2(2)
N6–C2–N9 109.3(2) 109.1(1) 110.1(2)
126.4(1) 122.5(3)
127.0(1) 126.6(2)
113.1(1) 113.1(2)
127.0(1) 126.6(2)
113.7(1) 113.1(2)
Fig. 3 Molecular structure of 2$H
2
O. Hydrogen atoms are shown as
spheres of arbitrary radii and thermal displacements are set at 50%
probability.
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i
Fig. 6 Selected hydrogen bonds in 2: (N1–H1–N9 , 0.90(2), 2.18(2),
˚
ꢀ
i
˚
ꢀ
2
.977(2) A, 147(2) ; N1–H1–N5 , 0.90(2), 2.39(2), 3.090(2) A, 135(2) ;
ii
N6–H6–N14 , 0.87(2), 2.09(2), 2.914 (2) A, 159(2) ; N2–H2–N15 ,
˚
ꢀ
iii
˚
ꢀ
iii
.92(2), 2.02(2), 2.871(2) A, 152(2) ; N2–H2–N19 , 0.92(2), 2.48(2),
0
3
0
˚
ꢀ
.141(2) A, 128(2) (i: 1.5 ꢁ x, 0.5 + y, z; ii: 1.5 ꢁ x, 0.5 + y, z; iii: 2 ꢁ x,
.5 + y, 0.5 ꢁ z).
Fig. 4 Hydrogen bonding of one H
2
bta (2) molecule within the layers (i:
2
ꢁ x, ꢁy, ꢁz; ii: 1 ꢁ x, 0.5 + y, 0.5 ꢁ z; iii: 1 ꢁ x, ꢁ0.5 + y, 0.5 ꢁ z).
‘‘Water-free’’ 2 crystallizes in the orthorhombic space group
Pbca with 16 molecules in the unit cell. The density of 1.861 g
ꢁ3
cm is the highest of the investigated compounds in this work
and is also higher in comparison to densities of other tetrazoles.
The molecular geometry shows a significant difference to that
observed in 2$H O and can be seen in Fig. 5. In the structure of 2,
2
all hydrogen atoms are directed to one side of the molecule. This
structure is anomalous and could not be achieved as a minimum
in theoretical structure optimization. Once again, all hydrogen
atoms participate in hydrogen bonds (Fig. 6) and the molecule
ꢀ
is nearly planar (torsion angle C1–N1–C2–N9 ¼ ꢁ4.4(3) . The
bonds to the tetrazole carbon atoms have lengths of C1–N1 ¼
˚
˚
1
.365(2) A and N1–C2 ¼ 1.366(2) A.
Fig. 7 Molecular structure of 2$H O$DMSO. Thermal ellipsoids are
2
Recrystallization of 2$H
colorless crystals containing, besides the bta molecule, one
crystal water and one DMSO molecule, abbreviated as
2
O from dimethyl sulfoxide yields
drawn at the 50% probability level and hydrogen atoms are shown as
spheres of arbitrary radii.
2$H O$DMSO. This compound crystallizes in the monoclinic
2
space group C2/c with eight molecules in the unit cell and can be
seen in Fig. 7. The DMSO solvent molecule participates in
a strong hydrogen bridge to the N2 atom through its oxygen
˚
ꢀ
atom (N2–H2–O2, 0.85(3), 1.89(3), 2.645(2) A, 148(2) ). The
distances and angles within the bistetrazolylamine are compa-
rable to those found in the previously described H
2
bta structures
and are given in Table 3.
5
crystallizes in the monoclinic space group P2 /c with four
1
ꢁ
3
molecules in the unit cell and a lower density of 1.530 g cm in
comparison to the structures of 2. The molecular unit is shown in
Fig. 8.
Both methyl groups are directed in the same direction. On the
Fig. 5 Molecular structure of 2. For clarity, only one molecule of the
asymmetric unit is shown. Thermal ellipsoids are drawn at the 50%
probability level and hydrogen atoms are shown as spheres of arbitrary
radii.
other side, a hydrogen bond between the nitrogen atoms N1
i
˚
ꢀ
and N5 (N9–H7–N4 : 0.92(2), 2.03(2), 2.946(2) A, 174(2) ; i: ꢁx,
2 ꢁ y, 2 ꢁ z.) results in dimer formation (Fig. 9). Once again, the
5
252 | J. Mater. Chem., 2008, 18, 5248–5258
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Fig. 8 Molecular structure of 5. Thermal ellipsoids are drawn at the 50%
probability level and hydrogen atoms shown as spheres of arbitrary radii.
Fig. 10 Molecular structure of 6. Thermal ellipsoids are drawn at the
5
0% probability level and hydrogen atoms shown as spheres of arbitrary
radii (i: x, 1.5 ꢁ y, z).
2
Fig. 9 Formation of dimers in the layer structure of Me bta (5).
molecules are packed in layers with a larger distance of
˚
approximately 3.65 A in comparison to those of 2$H
2
O.
Me bta (6) crystallizes in the monoclinic space group P2 /m
1
3
with 2 molecules in the unit cell. The atoms N1, C1, and H2 on
3
x, ⁄ , z are divided by the mirror plane generating the molecular
4
unit shown in Fig. 10.
The bond lengths and angles are in the same range as the
previously discussed molecules, whereby the molecule is not
0
Fig. 11 View along the a-axis on the Me bta molecules in the b–c layers.
3
ꢀ
observed to be planar (torsion angle N2–C2–N1–C2 ¼ 14.6(4) ).
Me bta crystallizes in a layer structure (Fig. 11), with only weak
3
Temperatures are given as onset temperatures. The loss of
ꢀ
interactions between and within the layers. There are no
hydrogen bonds since there are no N–H or O–H groups in these
water in 2$H
show the same decomposition temperatures of about 250 C.
2
O starts at around 145 C. However, 2 and 2$H
2
ꢀ
O
ꢁ3
molecules, resulting in the lowest density of 1.51 g cm observed
in this work.
ꢀ
5
is temperature-stable up to 263 C, whereupon it melts
ꢀ
under decomposition. 6 melts at 138 C and starts to decompose
ꢀ
at 236 C.
Differential scanning calorimetry (DSC)
Bomb calorimetry
DSC measurements to determine the melt and decomposition
temperatures of 2, 2$H O 5, and 6 were performed in covered
2
The heats of combustion of compounds 2$H O, 2, 5, and 6 were
2
Al containers containing a hole in the lid with a nitrogen flow of
determined experimentally using a Parr 1356 bomb calorimeter
41
(static jacket) equipped with a Parr 1108CL oxygen bomb. To
ꢁ
1
40
0 mL min on a Perkin-Elmer Pyris 6 DSC, calibrated by
2
ꢀ
ꢁ1
standard pure indium and zinc at a heating rate of 5 C min .
achieve better combustion, the samples (ca. 200 mg) were pressed
with a defined amount of benzoic acid (ca. 800 mg) forming
a tablet, and a Parr 45C10 alloy fuse wire was used for ignition.
The DSC plots in Fig. 12 show the thermal behavior of 1.0 mg
ꢀ
of 2, 2$H
2
O, 5, and 6 in the 50–400 C temperature range.
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Table 4 Physico-chemical properties
$H
2
2
O
2
5
6
Formula
Molecular mass/g mol
C
2
H
5
N
9
O
C
153.13
>30
>360
7.5
2
H
3
N
9
C
181.19
>45
>360
10
4
H
7
N
9
5 9 9
C H N
195.21
>70
>360
20
ꢁ
1
171.15
>100
>360
12
a
Impact sensitivity/J
Friction sensitivity/N
b
Electrical spark
discharge/J
c
d
N (%)
U (%)
73.67
ꢁ51.42
poor
250
1.693
2392
1714
203
82.34
ꢁ57.47
69.6
64.59
e
ꢁ101.57 ꢁ118.85
Combustion
ꢀ
very good good
263
poor
236
1.512
4702
3843
583
f
T
dec./ C
Density/g cm
250
ꢁ
3
g
1.861
2898
1858
633
1.530
3865
2932
350
ꢁ
1
h
ꢁ
D
D
H
comb.U/cal g
comb.H/kJ mol
ꢁ
1
i
ꢁ
ꢀ
ꢁ1
j
D
f
m
/kJ mol
Calculated values by EXPLO5:
ꢀ
ꢁ1
k
ꢁ
D
E
U /J g
2985
2555
220
7792
808
4537
3449
343
9120
753
2684
2184
172
7291
754
3853
2602
205
7851
752
l
2
Fig. 12 DSC thermograms of compounds 2$H O, 2, 5, and 6 (heating
T
E
/K
ꢀ
ꢁ1
m
rate of 5 C min ).
p/kbar
D/m s
Gas vol./L kg
ꢁ
1
n
ꢁ
1
o
ꢁ
1
In all measurements, a correction of 2.3 cal cm wire burned
was applied and the bomb was examined for evidence of
noncombusted carbon after each run. A Parr 1755 printer was
furnished with the Parr 1356 calorimeter to produce a permanent
record of all activities within the calorimeter. The reported values
are the average of three separate measurements. The calorimeter
was calibrated by combustion of certified benzoic acid (SRM,
a
b
BAM methods, see ref. 46, 47. BAM methods, see ref. 46, 47. OZM
c
d
electric spark tester, see ref. 51. Nitrogen content. Oxygen balance.
e
f
ꢀ
ꢁ1
g
Decomposition temperature from DSC (5 C min ). Estimated
h
from X-ray diffraction. Experimental (constant volume) combustion
i
energy. Experimental molar enthalpy of combustion. Molar enthalpy
j
k
of formation. Energy of explosion, EXPLO5 V5.02. Explosion
l
m
n
o
temperature. Detonation pressure. Detonation velocity. Assuming
only gaseous products.
3
9i, NIST) in an oxygen atmosphere at a pressure of 3.05 MPa.
The experimental results of the constant volume combustion
energy (Dcomb.U) of the salts are summarized in Table 4. The
ꢀ
standard molar enthalpy of combustion (Dcomb.H ) was derived
ꢀ
from Dcomb.H ¼ Dcomb.U + DnRT (Dn ¼ Dn
i
(products, g) ꢁ
Dn (reactants, g); Dn
i
i
is the total molar amount of gases in the
ꢀ
products or reactants). The enthalpy of formation, D
f
H , for
each of the compounds was calculated at 298.15 K using Hess’
law and the combustion reactions shown in Scheme 4. All
investigated tetrazoles are strongly endothermic, which was
Scheme 4 Combustion reactions.
ꢀ
expected by comparison with the literature (D H 2$H O: +203,
f
2
ꢁ1
2
: +633, 5: +350, 6: +586 kJ mol ). The influence of crystal water
ꢀ
50
according to instruction using the BAM friction tester.
can be seen at the lower D
f
H of 2$H
2
O, in comparison to 2.
Powdered 2$H
(
2
O and 5 are sensitive towards neither impact
The enthalpies of energetic materials are governed by the
molecular structures of the compounds and, therefore,
heterocycles with a higher nitrogen content (e.g. imidazole
<100 J) nor friction (<360 N), while 2 shows a moderate
impact (30 J) and friction sensitivity (300 N). 6 is only moderately
impact sensitive (30 J), but not friction sensitive. According to the
51
UN Recommendations on the Transport of Dangerous Goods,
ꢀ
ꢁ1 42
ꢀ
(
D
f
H
cryst ¼ 14.0 kcal mol ); 1,2,4-triazole (D
f
H
cryst
¼
ꢁ1
ꢀ
ꢁ1 43
2
6.1 kcal mol ); (D
f
H
cryst ¼ 56.7 kcal mol )) show higher
compounds 2$H O, 5, and 6 are classified as ‘‘insensitive’’, while 2
2
heats of formation. From the experimentally determined heats
of formation and densities obtained from single crystal structure
X-ray diffraction, various thermochemical properties have been
calculated using the EXPLO5 software (see below) and are
summarized in Table 4.
is described as ‘‘sensitive’’ and should only be handled with care
and appropriate precautions.
The electrostatic sensitivity tests were carried out using an
electric spark tester ESD 2010EN (OZM Research) operating
52
with the ‘‘Winspark 1.15 software package’’. The electrical
spark sensitivities were determined to be 7.5 J (2), 12 J (2$H
1
2
O),
0 J (5), and 20 J (6).
Sensitivities
Since the investigated tetrazoles are energetic compounds
with high nitrogen contents, the sensitivities toward friction
Detonation parameters
44
and impact were tested. The impact sensitivity tests were carried
Some detonation parameters such as pressure, temperature,
velocity, the heat of explosion, and the amount of gaseous
45
out according to STANAG 4489 and were modified according
46
to instruction using a BAM (Bundesanstalt f u¨ r Material-
decomposition products were calculated with the EXPLO5
53,54
47
48
forschung ) drophammer. The friction sensitivity tests were
V5.02 software.
This program is based on the steady-state
49
carried out according to STANAG 4487 and were modified
model of equilibrium detonation and uses BKW E.O.S. for
5
254 | J. Mater. Chem., 2008, 18, 5248–5258
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gaseous detonation products and Cowan–Fickett E.O.S. for
solid carbon. The calculations were performed using the BKWN
set of constants, the maximum densities according to the crystal
structures, the molecular masses and the experimentally
determined heats of formations. The results are given in Table 4.
The most useful values for classifying new explosives are the
detonation pressure and detonation velocity. In comparison with
common explosives such as TNT (trinitrotoluene, p ¼ 202 kbar,
ꢁ
1
D ¼ 7150 m s ), compounds 2$H
2
O, 2, and 6 show higher
detonation pressures (2$H O: 220, 2: 343, 6: 205 kbar) while
2
that of compound 5 is lower (172 kbar). Due to the correlation of
the detonation pressure and velocity, the same trend can be
found in the detonation velocities (2$H O: 7792, 2: 9120, 5: 7291,
2
ꢁ
1
6
: 7851 m s ). The calculated values of 2 are even higher
ꢁ
1
than those of RDX (hexogen, p ¼ 340 kbar, D ¼ 8882 m s ).
Therefore, the experimental explosion performance of 2 was
tested using a ‘‘Koenen’’ steel sleeve test.
Koenen test
The explosion performance, under confinement of compound 2
ignited thermally, was investigated using a ‘‘Koenen test’’ steel
55
sleeve apparatus. Data obtained from the Koenen test can be
related to the performance of the compound and can be used
to determine the shipping classification of a substance. This
information can also be used in evaluating the degree of venting
required to avoid an explosion during processing operations.
This test uses a non-reusable open-ended flanged steel tube,
a closing device with a variable orifice of 0–10 mm (through
which gases formed on decomposition are vented), an industrial
propane cylinder, and four Bunsen burners. For the test,
a defined volume of 25 mL of the compound is loaded into
a flanged steel tube and a threaded collar is slipped onto the tube
from below. The closing plate with the orifice is fitted over the
flanged tube and secured with a nut. Heating is provided by four
propane burners that are ignited simultaneously. The test is
completed when either rupture of the tube is observed or when
no reaction is observed after heating the tube for a minimum of
Fig. 13 ‘‘Koenen test’’ of compound 2 (a: filled steel sleeve; b: Koenen
test setup; c: collected fragments using a hole width of 8 mm; d: collected
fragments using a hole width of 10 mm).
15
coupled and decoupled N NMR spectra (with full NOE)
were recorded. Infrared (IR) spectra were recorded using a Per-
kin-Elmer Spektrum ‘‘One FT-IR’’ instrument. Raman spectra
were measured using a Perkin-Elmer Spektrum 2000R NIR
FT-Raman instrument equipped with
a Nd:YAG laser
(
1064 nm). The intensities are reported as percentages relative to
the most intense peak and are given in parentheses. Elemental
analyses were performed with a Netsch STA 429 Simultaneous
Thermal Analyzer. Bomb calorimetry was performed using
a Parr 1356 Bomb calorimeter with a Parr 1108CL oxygen bomb.
The sensitivity data were obtained using a BAM drophammer
and a BAM friction tester.
5
min. After each trial, the fragments of the tube, if any, are
collected and weighed. The reaction is evaluated as an explosion
if the tube is fragmented into three or more pieces. TNT destroys
the steel tube to a hole of width 6 mm and RDX achieves this
with a hole of width 8 mm. The result of the Koenen test can be
seen in Fig. 13. Compound 2 destroyed the steel tube into more
than 20 fragments using hole widths of 8 mm and 10 mm, and it
can therefore be assumed that compound 2 offers a greater
explosion performance than RDX, which is in accordance with
the calculated detonation values.
CAUTION!
Tetrazole derivatives are considered energetic materials and
tend to explode under certain conditions. Although we have not
experienced any problems during the synthesis of the reported
compounds, appropriate safety precautions should be taken at all
times, especially when manipulating 2. Laboratories and personnel
should be properly grounded and safety equipment such as Kevlarª
gloves, leather coats, face shields, and ear plugs are necessary.
Experimental
All reagents and solvents were used as received (Sigma-Aldrich,
Fluka, Acros Organics) if not stated otherwise. Melting points
were measured with a Perkin-Elmer Pyris 6 DSC, using heating
0
5
,5 -Bis(1H-tetrazolyl)amine monohydrate (2$H
2
O)
To a 2000 mL three-neck reaction flask containing a refluxing
suspension of sodium dicyanamide (44.5 g, 0.5 mol), sodium
azide (65.0 g, 1.0 mol), ethanol (400 mL), and water (250 mL)
was added 2 M HCl (750 mL) over the course of five hours. The
ꢀ
ꢁ1
rates of 5 C min and were checked using a B u¨ chi Melting Point
1
13
15
B-450 apparatus. H, C, and N spectra were recorded with
a Jeol Eclipse 270, a Jeol EX 400, or a Jeol Eclipse 400 instru-
ment. All chemical shifts are quoted in ppm relative to TMS
reaction mixture was refluxed for a further 48 h. After cooling to
ꢀ
1
13
15
(
H, C), CH
3
NO
2
( N). For compounds 2, 5, and 6 the proton
0 C in an ice bath and addition of conc. HCl (80 mL) 2$H O was
2
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obtained as a fine colorless precipitate. The precipitate was
filtered off and washed with small amounts of ethanol and
diethyl ether and dried under vacuum. Yield: 75 g (0.43 mol,
1346 (11), 1204 (22), 1098 (14), 1084 (30), 1065 (24), 1011 (55),
1
748 (5), 680 (38), 446 (8), 386 (8), 348 (20), 247 (30), 222 (20); H
ꢀ
13
NMR ([d ]-DMSO, 25 C) d: 10.91 (s, NH), 4.27 (s, CH );
6
C
3
ꢀ
15
8
8%). The product can be recrystallized from dilute acids such
ꢁ1
NMR ([d
6
]-DMSO, 25 C) d: 162.7 (CN ), 40.1 (CH
4
3
);
N
ꢀ
ꢀ
ꢀ
3
as HCl or HClO
4
. Mp 250 C (dec.), (DSC, 5 C min ); IR
NMR (CF
3
-COOH, 25 C) d: ꢁ11.3 (N3, q, JNH ¼ 1.86 Hz),
ꢁ1
3
(
KBr, cm ): ~n ¼ 3456 (s), 3028 (s), 2932 (s), 2858 (s), 2671 (m),
438 (m), 1796 (w), 1656 (vs), 1611 (s), 1556 (s), 1454 (m), 1352
m), 1337 (m), 1282 (m), 1263 (m), 1154 (w), 1110 (m), 1072 (s),
ꢁ109.2 (N4, s), ꢁ110.2 (N1, q, JNH ¼ 1.9 Hz), ꢁ111.5 (N2, q,
NH ¼ 2.1 Hz), ꢁ316.4 (N5, s); m/z (DEI ): 181 (M , 11) 153
(11), 96 (2), 82 (3), 67 (5), 56 (4), 53 (10), 43 (100), 42 (63),
39 (4), 28 (42), 27 (12), 15 (54); EA (C , 181.17) calcd:
2
J
+
+
2
(
1
6
3
1
1
501 (s), 1036 (m), 1003 (m), 899 (m), 819 (m), 790 (m), 738 (m),
4 7 9
H N
ꢀ
ꢁ1
90 (m), 503 (m), 406 (w); Raman (200 mW, 25 C, cm ): ~n ¼
328 (11), 3120 (8, br), 1649 (9), 1618 (34), 1552 (54), 1480 (22),
455 (17), 1370 (17), 1346 (15), 1267 (25), 1226 (26), 1151 (15),
128 (15), 1073 (100), 1039 (42), 838 (7), 794 (17), 736 (9), 670 (7),
21 (22), 409 (48), 381 (9), 348 (20), 321 (48), 172 (100), 147 (46);
C 26.52, H 3.89, N 69.59%; found: C 26.50, H 3.93, N 69.27%;
impact sensitivity: >45 J; friction sensitivity: >360 N;
ꢁ1
Dcomb.U: ꢁ3865 cal g .
4
0
5
,5 -Bis(2-methyltetrazolyl)methylamine (6)
1
ꢀ
13
H NMR ([d ]-DMSO, 25 C) d: 11.92 (s, br), 9.53 (s, br); C
6
ꢀ
15
]-DMSO, 25 C) d: 154.7 (C); N{ H} NMR ([d
1
NMR ([d
6
6
]-
Dimethyl sulfate (0.95 mL, 10 mmol) was slowly added to
ꢀ
ꢀ
DMSO, 25 C) d: ꢁ17.9 (N2), ꢁ123.8 (N1), ꢁ315.7 (NH); m/z
a stirred, warm (65 C) solution of 5 (1.81 g, 10 mmol) and
+
+
(
(
(
DEI ): 153 (M ꢁ H
35), 69 (34), 68 (36), 57 (33), 53 (23), 43 (33), 42 (81), 41 (39), 29
39), 28 (100); EA (C O, 171.15) calcd: C 14.04, H 2.95, N
3.67%; found: C 14.10, H 2.61, N 73.19%; impact sensitivity:
2
O, 66), 128 (18), 127 (9), 97 (16), 96 (20), 70
NaOH (0.40 g, 10 mmol) in H O (15 mL). The colorless mixture
2
was heated for 2 h from which after cooling to RT the product 6
separated as a colorless precipitate. After filtration, 6 was washed
with cold water and recrystallized. Yield: 1.41 g (7.2 mmol, 72%).
2 5 9
H N
7
ꢁ1
ꢀ
ꢀ
ꢁ1-
>
100 J; friction sensitivity: >360 N; Dcomb.U: 2392 cal g .
Mp 137–139 C, 236 C (dec.); IR (KBr, cm ): ~n ¼ 3109 (w),
038 (w), 2957 (w), 2576 (w), 2421 (w), 1968 (w), 1585 (s), 1553
vs), 1471 (m), 1421 (m), 1385 (w), 1364 (w), 1293 (w), 1210 (m),
167(m), 1147 (m), 1061 (w), 1009 (m), 745 (m), 735 (s), 697 (w),
3
(
0
5
,5 -Bis(1H-tetrazolyl)amine (2)
1
ꢁ
3
ꢀ
ꢁ1
Compound 2$H O was dehydrated under vacuum (24 h, 10
2
666 (w), 580 (w); Raman (200 mW, 25 C, cm ): ~n ¼ 3038 (17),
3018 (18), 2961 (67), 1614 (11), 1553 (91), 1463 (13), 1425 (14),
1383 (27), 1366 (23), 1295 (8), 1202 (19), 1148 (15), 1060 (15),
1010 (100), 736 (15), 582 (42), 390 (19), 341 (16), 250 (16),
ꢀ
ꢀ
Torr) at elevated temperature (120 C). Mp 250 C (dec.); IR
ꢁ1
(
KBr, cm ) ~n ¼ 3267 (m), 3136 (m), 3080 (m), 2934 (m), 1654
(
vs), 1618 (s), 1607 (s), 1570 (s), 1547 (m), 1481 (m), 1445 (w),
1
ꢀ
1
384 (w), 1321 (w), 1288 (w), 1228 (w), 1174 (w), 1133 (m), 1078
145 (27); H NMR ([d
6
]-DMSO, 25 C) d: 4.29 (CH , s), 3.60
3
13
ꢀ
(
(
(
(
(
w), 1057 (m), 1042 (m), 1014 (w), 835 (w), 806 (w), 749 (w), 719
(N
s
CH
3
, s); C NMR ([d
15
(C3), 36.8 (C1); N NMR ([d
6
]-DMSO, 25 C) d: 164.6 (C2), 40.3
ꢀ
ꢀ
ꢁ1
w), 600 (w); Raman (200 mW, 25 C, cm ) ~n ¼ 2986 (58), 1606
47), 1595 (48), 1568 (22), 1550 (83), 1450 (32), 1422 (20), 1381
37), 1322 (38), 1287 (27), 1243 (17), 1186 (57), 1132 (100), 1078
50), 1057 (53), 1014 (38), 810 (13), 397 (81), 339 (32), 312 (26),
]-DMSO, 25 C) d: ꢁ5.2 (N3, q,
6
3
J
3
N–HH ¼ 1.9 Hz), ꢁ76.2 (N4, s), ꢁ104.0 (N1, q, JN–H ¼ 1.9 Hz),
2
2
ꢁ110.5 (N2, q, JN–H ¼ 2.2 Hz), ꢁ324.5 (N5, q, JN–H ¼ 2.2 Hz;
EA (C , 195.22): calcd: C 30.77, H 4.65, N 64.59%; found:
5
9 9
H N
+
2
01 (41), 167 (47); EA (C
2
H N
3 9
, 181.17) calcd: C 15.69, H 1.97, N
C 30.62, H 4.50, N 64.51%; m/z (DEI): 195 [(M ) (22)], 167 (9),
68 (8), 96 (48), 56 (21), 53 (12), 43 (100), 42 (37), 28 (34), 27 (8);
impact sensitivity: >70 J; friction sensitivity: >360 N.
8
2.34%; found: C 15.61, H 2.07, N 81.62%; impact sensitivity:
ꢁ
1
>
30 J; friction sensitivity: >300 N; Dcomb.U: ꢁ2898 cal g .
ꢁ1
Dcomb.U: ꢁ4702 cal g .
0
5
,5 -Bis(2-methyltetrazolyl)amine (5)
X-Ray diffraction studies
In a 500 mL three neck round bottom flask, 2$H O (17.1 g,
2
0
0
.1 mol) was neutralized with an aqueous NaOH solution (8.0 g,
ꢀ
Suitable single crystal of 2$H O$DMSO and 6 were picked from
2
.2 mol in 100 mL water) and warmed to 60 C until a clear dark-
the crystallization mixture and mounted in Kel-F oil and trans-
red solution was obtained. Methyl iodide (12.5 mL, 0.21 mol) in
acetone (50 mL) was then added drop-wise to the reaction
ferred to the N stream of an Oxford Xcalibur3 diffractometer
2
with a Spellman generator (voltage 50 kV, current 40 mA) and
a KappaCCD detector. The data collections were performed
56
mixture. Afterwards the solution was heated under reflux for
ꢀ
1
2 h. After cooling the reaction mixture (4 C) compound 5 was
using the CrysAlis CCD software, the data reduction with the
5
7
obtained as a colorless precipitate. The precipitate was filtered
off and washed with acetone (2 ꢂ 30 mL) and dried under
vacuum. Yield: 9.1 g (55 mmol, 55%). The product can be
CrysAlis RED software. The data for compounds 2, 2$H
and 5 were collected on a Nonius Kappa CCD diffractometer
under an N stream as well. Data collection and reduction was
2
O
2
recrystallized from dilute mineral acids such as HCl or HClO
4
.
done by the Bruker ‘‘Collect’’ and the ‘‘HKL Denzo and Scale-
58
ꢀ
ꢁ1
Mp 263 C (dec.); IR (KBr, cm ): ~n ¼ 3417 (w), 3278 (m), 3194
m), 3097 (m), 3049 (m), 2949 (w), 2890 (w), 2862 (w), 1644 (vs),
565 (s), 1540 (s), 1465 (w), 1434 (w), 1417 (w), 1329 (w), 1202
m), 1097 (w), 1055 (w), 1010 (w), 885 (w), 837 (w), 744 (m), 702
pack’’ software. The structures were solved with SIR-92
60
59
(
(2$H O, 2$H O$DMSO and 6), and SHELXS-97 (2 and 5),
2 2
61
1
refined with SHELXL-97 and finally checked using the PLA-
62
(
(
(
TON software. The non-hydrogen atoms were refined aniso-
tropically and the hydrogen atoms were located and freely
ꢀ
ꢁ1
w), 679 (w); Raman (200 mW, 25 C, cm ): ~n ¼ 3269 (4), 3197
4), 3047(22), 3031(21), 2963 (81), 2821 (4), 1631 (7), 1563 (100),
2
refined. The absorptions of 2$H O$DMSO and 6 were corrected
63
1
395 (8), 1455 (14), 1438 (14), 1419 (14), 1396 (33), 1381 (23),
by a SCALE3 ABSPACK multi-scan method. All relevant data
5
256 | J. Mater. Chem., 2008, 18, 5248–5258
This journal is ª The Royal Society of Chemistry 2008

View Online
and parameters of the X-ray measurements and refinements are
given in Table 2. Further information on the crystal-structure
determinations is available as ESI.†
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0
–
5,5 -(Bis-1H-tetrazolyl)amine
monohydrate
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(2$H O,
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ꢀ
–
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–
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Acknowledgements
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