Energetic Metal and Nitrogen-Rich Salts of the Pentaerythritol Tetranitrate Analogue Pentaerythritol Tetranitrocarbamate

Article abstract of DOI:10.1021/acs.inorgchem.8b03540

The tetravalent pentaerythritol tetranitrocarbamate (PETNC) is deprotonated by nitrogen-rich, alkaline, alkaline earth metal, and silver bases to form the corresponding salts. Thorough analysis and characterization by multinuclear NMR, vibrational spectroscopy, elemental analysis, thermoanalytical techniques, and single crystal X-ray diffraction was performed. Furthermore, the energies of formation for the nitrogen-rich salts were calculated utilizing the Gaussian program package. The detonation performances were calculated with the Explo5 (V6.03) computer code, and the sensitivities toward impact and friction were determined and compared to the neutral PETNC and pentaerythritol tetranitrate (PETN). Ecotoxicological studies of the ammonium and guanidinium salt using Vibrio fischeri bacteria complete this study.

Full text of DOI:10.1021/acs.inorgchem.8b03540

Article
pubs.acs.org/IC
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
Energetic Metal and Nitrogen-Rich Salts of the Pentaerythritol
Tetranitrate Analogue Pentaerythritol Tetranitrocarbamate
̈
Thomas M. Klapotke,* Burkhard Krumm,* and Cornelia C. Unger
Energetic Materials Research, Department of Chemistry, Ludwig-Maximilian University Munich, Butenandtstr. 5−13 (D), 81377
Munich, Germany
S
* Supporting Information
ABSTRACT: The tetravalent pentaerythritol tetranitrocarbamate
(PETNC) is deprotonated by nitrogen-rich, alkaline, alkaline earth
metal, and silver bases to form the corresponding salts. Thorough
analysis and characterization by multinuclear NMR, vibrational
spectroscopy, elemental analysis, thermoanalytical techniques, and
single crystal X-ray diffraction was performed. Furthermore, the
energies of formation for the nitrogen-rich salts were calculated
utilizing the Gaussian program package. The detonation perform-
ances were calculated with the Explo5 (V6.03) computer code, and
the sensitivities toward impact and friction were determined and
compared to the neutral PETNC and pentaerythritol tetranitrate
(PETN). Ecotoxicological studies of the ammonium and
guanidinium salt using Vibrio fischeri bacteria complete this study.
detonation velocity and experimental small-scale reactivity test,
PETN is the superior compound. Though PETNC was
investigated with underwater explosion tests and showed
acceptable performance values.14 In this work, new nitrogen-
rich salts, as well as selected metal salts of PETNC, are
presented. These salts allow the determination of the aquatic
toxicity of the PETNC anion. Furthermore, some alkali and
alkaline earth metal salts may serve as potential flame
colorants.
INTRODUCTION
■
Pentaerythritol is a commercially available tetravalent alcohol
with a neopentane backbone. It is a common source for
energetic materials, such as pentaerythritol tetranitrate (PETN,
Nitropenta),1 which is used in detonators and, along with
RDX, is the main ingredient in SEMTEX.2 More recently,
silicon-based pentaerythritol derivatives [Si(CH2N3)4 and
Si(CH2ONO2)4] were synthesized but are too sensitive for
practical application.3 The less sensitive sila-nitrocarbamate
derivative of PETN was also very recently investigated in our
group, however its performance data are not favorable.4
Nitrocarbamates in general gained more attention in the field
of energetic materials chemistry.5−9 Due to their resonance
effects, which lead to a reduction in the electrophilicity of the
carbonyl group, they are relatively stable toward acid
hydrolysis.10 The high stability allows the nitration of
carbamates using rough reaction conditions, like fuming nitric
acid and concentrated sulfuric acid. Also, salt formation is
possible, taking into account the increase of the acidity of the
amino-hydrogen next to the electron withdrawing nitro group.
Pentaerythritol tetranitrocarbamate (PETNC) combines the
easy availability of pentaerythritol and the valuable properties
of nitrocarbamates.11 After our reports on trinitroethyl
nitrocarbamate (TNENC),7,8 others were very quick to
prepare the first organic salts of TNENC and examine their
properties, however with low thermal stability.12,13 Up to now,
PETNC and its ammonium salt were investigated, whereby
PETNC shows better thermal stability, better sensitivity values,
and density comparable to that of PETN. The ammonium salt
is even less sensitive than PETNC, however its density is lower.
Concerning the energetic parameters, such as the calculated
RESULTS AND DISCUSSION
■
Synthesis. The previously described synthesis of primary
carbamates was based on two steps, starting from a reaction of
the respective alcohol with toxic phosgene to the chlor-
oformate and subsequent treatment with ammonia.15 A more
convenient route is using the reactive chlorosulfonyl isocyanate
(CSI) in a one-step synthesis, followed by feasible aqueous
workup.16 CSI was discovered in Germany in 1956; nowadays,
it is a commercially available reagent giving easier access to the
corresponding carbamate.17,18 Using CSI, pentaerythritol
tetracarbamate was synthesized in high yield and purity and
subsequently nitrated to pentaerythritol tetranitrocarbamate
(PETNC) with mixed acid as outlined in Scheme 1.
PETNC has four acidic nitramine hydrogen atoms which
can easily be deprotonated. Analoguous to the tetraammonium
salt,11 nitrogen-rich, alkaline, and alkaline earth metal and
silver salts were obtained by the reaction of the free bases with
Received: December 21, 2018
© XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.8b03540
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Article
Scheme 1. Synthesis of Pentaerythritol Tetranitrocarbamate (PETNC) Starting from Pentaerythritol
a
Scheme 2. Synthesis of Various Salts of PETNC
a
Bases used: (a) ammonia, (b) guanidinium carbonate, (c) aminoguanidinium bicarbonate, hydroxides of (d) lithium, (e) sodium, (f) potassium,
(g) calcium, (h) strontium and (i) barium.
Scheme 3. Synthesis of the Silver Salt of PETNC (10)
PETNC in aqueous solution (Scheme 2). However, attempts
to prepare hydrazinium or hydroxylammonium salts failed.
The salt formation proceeds conveniently in aqueous
solution at ambient temperature (except the guanidinium salt
2 had to be heated to reflux), and colorless solids are obtained
in 63% up to quantitative yields. The metal salts form hydrates;
their water content was calculated from the elemental analysis
values, except for the sodium salt 5 (extremely hygroscopic and
viscous). In addition, the water content was confirmed in most
cases using thermal gravimetric analysis (TGA, Figure 2). Due
to the general low solubility of silver salts in water, silver salt
10 was synthesized with acetonitrile as solvent. Ag+ is known
B
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Article
to form a stable diacetonitrile cationic complex [Ag-
(CH3CN)2]+. However, it was not possible to determine the
exact solvate content; therefore, this is denoted accordingly as
shown in Scheme 3.19,20
NMR and Vibrational Spectroscopy. In the NMR
1
spectra, some trends are observed. In the H NMR spectra
the resonances of the CH2 groups of the tetranitrocarbamates
are found at 3.81−3.91 ppm and therefore shifted upfield
compared to PETNC (δ = 4.15 ppm) due to deprotonation.11
This is consistent with the CH2-signal of the ammonium salt
which is shifted to 3.88 ppm. Comparable tendencies are
observed in the 13C NMR spectra. The resonance of the
carbonyl carbon atom in neutral PETNC is located at 148.9
ppm and the resonances for the salts are found at lower field
between 158.8−160.5 ppm. The 13C NMR resonances of the
neopentane skeleton remain unaffected upon deprotonation of
PETNC. The resonances of the cations guanidinium and
aminoguanidinium are detected at 158.0 ppm (2) and 158.9
ppm (3). In the 14N NMR spectra the resonances for the nitro
groups of salts 2−8 can be detected as broadened signals
between −2 and −13 ppm. The resonances for the nitrile
solvate of 10 are found at δ = 2.07 ppm in the 1H NMR, at δ =
118.1 ppm in the 13C{1H} NMR and at −134.9 ppm in the
14N NMR spectra. The resonance of the silver-acetonitrile
cation was detected at 255 ppm in the 109Ag NMR spectrum
with DMSO-d6 as solvent. A comparison with a previous 109Ag
NMR study of solvate-free silver nitroformate solutions in
various solvents revealed, that the shift of 255 ppm is in
between those of 181 ppm (DMSO) and 430 ppm
(acetonitrile) of Ag[C(NO2)3].21 This deviation can be
explained by solvate exchange between Ag+−acetonitrile and
the DMSO solvent.
Figure 1. Crystal structure of tetrakis-aminoguanidinium pentaery-
thritol tetranitrocarbamate 3. Selected distances [Å] and angles [°]:
C3−N1 1.370(2), C3−O2 1.215(2), C3−O1 1.366(2), C2−C1
1.536(2), C2−O1 1.438(2), C2−H7 0.98(2), C2−H8 0.96(2), N1−
N2 1.344(2), N2−O3 1.243(2), N2−O4 1.238(2), N2−C3−O2
132.1(1), N2−C3−O1 105.0(1), O2−C3−O1 122.8(1), C1−C2−
O1 113.5(1), N1−N2−O3 114.1(1), N1−N2−O4 124.9(1), O3−
N2−O4 120.9(1), C3−N1−N2 117.4(1), C3−O1−C2 118.1(1).
energetic properties of the nonmetal salts 1−3, amino-
guanidinium salt 3 is in the range of TNT in terms of
detonation velocity (Vdet = 6950 m s−1).2 Nevertheless, PETN
and PETNC are still superior in terms of these properties.
With decomposition temperatures of 136 °C (1), 180 °C
(2), 149 °C (3), 186 °C (4), 156 °C (5), 177 °C (6) 161 °C
(7), 152 °C (8), and 176 °C (9), the salts 2, 4, 6, 7, and 9
show an appropriate thermal stability. The thermally most
stable salt was the lithium salt 4 with a decomposition
temperature of 186 °C. The neutral PETNC is still the
thermally most stable compound. The sensitivities toward
impact and friction were determined with a BAM Drop-
hammer24 and a BAM Friction Tester.25 The salts were then
classified according the UN recommendations on the transport
of dangerous goods;26 therefore, we considered 1−3 as
insensitive and 7−9 as less sensitive. Only the lithium (4)
and potassium (6) salts show impact sensitivities in the range
of sensitive compounds (20 and 7 J).
In the vibrational spectra (IR and Raman, see the
Supporting Information), the characteristic strong carbonyl
stretching vibrations are located in the range of ν = 1688−
̃
1651 cm−1, which are in range of the NH4 salt.11 For the
+
metal salts no N−H vibrations can be found in the Raman
spectra in the range of ν
̃
= 3450−3200 cm−1, due to
deprotonation. Because of the predominant hydrate water
which overlaps this particular region, no statement can be
made throughout the IR spectra. The N−H stretching
vibrations for hydrate-free guanidinium salt 2 and amino-
guanidinium salt 3 are located at ν
̃
= 3415−3208 cm−1.
Single-Crystal Structure Analysis. Single crystals suitable
for X-ray diffraction measurements were obtained for amino-
guanidinium salt 3 by recrystallization from water. The
molecular structure of 3 is shown in Figure 1, which crystallizes
When comparing the room-temperature densities of the
synthesized salts, 1 (ρ = 1.62 g cm−3) and 3 (ρ = 1.64 g cm−3)
show acceptable values; however, only the density of PETNC
(ρ = 1.76 g cm−3) is in the range of PETN (ρ = 1.78 g
cm−3).11
TGA measurements of salts 4−9 at a heating rate of 5 °C
min−1 revealed a starting weight loss in a temperature range of
103−108 °C, which was not observed in the TGA measure-
ment of PETNC (Figure 2). This leaving hydrate water is
consistent with the hydrate water calculated from elemental
analysis.
Additionally, the flame colors of the alkaline and alkaline
earth salts were tested with a small-scale setup in a Bunsen
burner flame, as these metals are known to show visible flame
colors and could be useful in terms of pyrotechnical
applications. Thereby, PETNC salts 4−8 combusted with a
visible flame color as expected (see the Supporting
Information), except for low solubility barium salt 9. Further
efforts are conducted to establish the potential use in
pyrotechnical formulations.
̅
as a colorless block in the triclinic space group P1 with two
molecules per unit cell and a density of 1.65 g cm−3 at 123 K.
The structure of 3 is similar to that of the ammonium salt.11
The nitro groups are rotated out of plane of the nitrocarbamate
moiety, as demonstrated by the torsion angle O3−N2−O1−
C3 (−12.5°). For the nitramine moiety, the N1−N2 bond
length is 1.344 Å, which is shorter than the neutral compound
(1.379 Å) and more comparable to the N1−N2 bond length of
the NH4 salt (1.332 Å).11 For PETNC, this indicates a
+
substantial double-bond character, achieved by delocalization
of the nitrogen lone pair of N1, which is more substantial for
the salts.
Physical and Energetic Properties. The physical and
energetic properties of the salts 2−9 were determined and are
summarized in Tables 1 and 2. PETNC and 1 were
recalculated using version 6.03 of Explo5.22 Concerning the
C
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Table 1. Physical and Energetic Properties of Salts 1−3 Compared to PETNC and PETN
111
2
3
PETNC
PETN
formula
C9H24N12O16
556.36
136
>40
>360
>1.0
1.64
30.2
46.1
−14.4
−40.3
C13H32N20O16
724.52
180
>40
>360
>1.5
1.49 (pyc.)
38.7
34.6
−28.7
−57.4
C13H36N24O16
784.58
149
>40
>360
>1.5
1.62
42.9
54.5
C9H12N8O16
488.24
196
8
360
0.75
1.76
23.0
3.3
C5H8N4O12
316.14
165
3
60
0.50
1.78
17.7
60.7
M [g mol−1
]
a
Tdec [°C]
b
IS [J]
c
FS [N]
d
ESD [J]
e
ρ [g cm−3
]
f
N [%]
O [%]
g
h
i
ΩCO [%]
−30.6
−57.1
3.3
−26.2
15.2
−10.1
ΩCO [%]
2
j
ΔHf° [kJ mol−1
]
−2378
−2306
−1882
−1311
−561
Explo5 v6.03
k
−ΔExU° [kJ kg−1
]
1996
174
7028
1735
134
6336
2219
181
3826
242
5980
319
k
PCJ [kbar]
k
Vdet [m s−1
]
7307
7686
8405
k
Vo [L kg−1
]
856
866
890
718
743
a
b
c
Onset decomposition point Tdec from DSC measurement carried out at a heating rate of 5 °C min−1. Impact sensitivity. Friction sensitivity.
d
e
f
Sensitivity toward electrostatic discharge. RT densities are recalculated from X-ray densities or measured by gas pycnometer (pyc.). Nitrogen
g
h
i
j
content. Oxygen content. Oxygen balance assuming the formation of CO and CO2. Enthalpy and of formation calculated by the CBS-4 M
method using Gaussian 09.23 Predicted heat of combustion, detonation pressure, detonation velocity, and volume of gaseous products calculated
k
by using the Explo5 (version 6.03) program package.22
Table 2. Physical Properties of Metal Salts 4−9
4
5
6
7
8
9
formula
Li4C9H8N8O16·2.5 H2O Na4C9H8N8O16·xH2O K4C9H8N8O16·2H2O Ca2C9H8N8O16·7H2O Sr2C9H8N8O16·7H2O Ba2C9H8N8O16·4H2O
M [g mol−1
]
557.00
186
20
d
156
d
676.63
177
7
690.46
161
40
785.55
152
40
830.92
176
35
a
Tdec [°C]
b
IS [J]
c
FS [N]
360
d
360
360
360
360
a
b
c
Onset decomposition point Tdec from DSC measurement carried out at a heating rate of 5 °C min−1. Impact sensitivity. Friction sensitivity.
The values of the sodium salt 5 were not determined, because of its high hygroscopicity.
d
Figure 2. TGA measurements of PETNC (left) and the tetralithium salt 4 (right) at a heating rate of 5 °C min−1.
Toxicity Assessment. In order to determine the
ecotoxicological impact of water-insoluble PETNC, the EC50
(effective concentration) values of ammonium salt 1 and
guanidinium salt 2 were measured. EC50 refers to the
concentration of a toxicant which induces a response of 50%
after a specific exposure time. The method used herein was
based on bioluminescent Vibrio fischeri NRRL-B-11177 marine
bacteria strains whose luminescent is inhibited when exposed
to a toxicant. Therefore, the EC50 is defined as the
concentration level where the bioluminescence is halfway
decreased. All measurements started with the determination of
the bioluminescence of untreated reactivated bacteria. After
exposure times of 15 and 30 min, the bioluminescence was
determined. The resulting effective concentration leads to a
D
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software package34 and finally checked with the Platon software.35 All
non-hydrogen atoms were refined anisotropically. The hydrogen atom
positions were located on a difference Fourier map. Diamond plots
are shown with thermal ellipsoids at the 50% probability level.
The theoretical calculations were carried out by using the program
package Gaussian 0923 and were visualized by GaussView 5.08.36
Structural optimizations and frequency analyzed were performed at
the B3LYP level of theory (Becke’s BE three parameter hybrid
functional using the LYP correlation functional). For C, H, N, and O,
a correlation-consistent polarized double-ζ basis set cc-pVDZ was
used. The enthalpies (H) and free energies (G) were calculated on
the CBS-4 M level of theory (complete basis set). CBS-4 M starts
with a HF/3-21G(d) geometry optimization, an initial guess for the
following SCF calculation as base energy. This finishes with a final
MP2/6-31+G calculation with a CBS extrapolation to correct the
energy in second order. For an approximation of higher order
contributions, implementations of MP4(SDQ)/6-31+(d,p) and
additional empirical corrections are required. The enthalpies of the
gas-phase species were estimated according to the atomization energy
method.37 The gas-phase enthalpies of formation were converted into
the solid-state values using the lattice energy equation provided by
Jenkins.38−41 All calculations affecting the detonation parameters were
based on condensed phase enthalpies of formation and carried out by
using the program package Explo5 V6.03.22
classification of the compounds as nontoxic (>1.00 g L−1),
toxic (0.10−1.00 g L−1), and very toxic (<0.10 g L−1).27 Our
own previous results on RDX28 proved that the half-maximum
effective concentration of RDX [EC50 (30 min) = 0.24 g L−1]
is in the range of toxic compounds [lit.: EC50 (30 min) = 0.27
g L−1].29 Ammonium salt 1 did not lead to an inhibition of the
bioluminescence up to 10% after 15 and 30 min using a
solution with c = 2.02 g L−1. Guanidinium salt 2 was measured
in higher concentrations and revealed an EC50 value of 2.86 g
L−1 at 15 min and of 1.42 g L−1 at 30 min. Therefore, the
PETNC anion can be considered nontoxic according to Vibrio
fischeri.
CONCLUSIONS
■
New nitrogen-rich, alkaline, alkaline earth metal, and silver
salts of PETNC were synthesized and thoroughly characterized
by various analytical methods. The thermal stability of
guanidinium salt 2 is in a promising range (180 °C), and the
detonation velocity of aminoguanidinium salt 3 is almost in the
range of PETNC. All salts are of remarkably low sensitivity
against impact, friction and electrostatic discharge. The
burning behavior of metal salts 4−8 show a combustion with
a visible flame color, as to be expected for alkali and alkaline
earth metal salts. Nevertheless, more efforts are necessary to
find a practical application for salts 4−8 in pyrotechnic
formulations based on their visible flame color. The tested
ammonium and guanidinium salt are considered nontoxic
according to Vibrio fischeri. Further tests should show if
PETNC could have a potential application as nontoxic and
stable safe-handling PETN alternative.
Caution! Pentaerythritol tetranitrocarbamate (PETNC) and poten-
tially the metal salts are considered as sensitive materials and therefore
should be handled with caution during synthesis or manipulation, and
additional protective equipment (leather jacket, face shield, ear protection,
Kevlar gloves) is strongly recommended.
General Procedure for the Salt Preparation (2−9). Various
amounts of PETNC (0.5−1 mmol) in 5−10 mL water are stirred and
to this suspension equimolar amounts of the base (guanidinium
carbonate; aminoguanidinium bicarbonate; hydroxides of lithium,
sodium, potassium, calcium, strontium, and barium) was added at
ambient temperature. The resulting mixture is further stirred for 1−2
h (additionally 1 h at 100 °C for guanidinium carbonate) or 12 h (Ca,
Sr, Ba). In the case of Ca/Sr/Ba the precipitate is filtered and dried. In
all other cases, the water is removed in vacuo and the PETNC salts
isolated (2 83%, 3 100%, 4 65%, 5 100%, 6 93%, 7 82%, 8 63%, 9
79%).
EXPERIMENTAL SECTION
■
General. Solvents, deuterated solvents of NMR experiments, and
all further chemicals were used as received from the suppliers, without
further purification. NMR spectra were recorded with a Bruker 400 or
Bruker 400 TR at ambient temperature. The chemical shifts were
determined with respect to external standards, Me4Si (1H 399.8 MHz;
13C 100.5 MHz), MeNO2 (14N 28.9 MHz), and AgNO3 (109Ag 18.6
MHz).
1
Tetrakis(guanidinium) PETNC (2). H NMR ([D6]DMSO): δ =
7.08 (s, 24H, NH2), 3.84 (s, 8H, CH2) ppm. 13C NMR
([D6]DMSO): δ = 159.4 (CO), 158.0 (C(NH2)2), 63.5 (CH2),
41.3 (C) ppm. 14N NMR ([D6]DMSO): δ = −7 (NO2) ppm. EA:
C13H32N20O16 (724.52): calcd C 21.55, H 4.45, N 38.66%. Found C
21.56, H 4.35, N 38.57%. IS: 40 J (grain size <100 μm). FS: 360 N
(grain size < 100 μm). ESD: 1.50 J (grain size < 100 μm). DSC (5 °C
min−1): 180 °C (dec.).
Infrared spectra were measured with a PerkinElmer Spectrum BX-
FTIR spectrometer equipped with a Smiths DuraSamplIR ATR
device. Raman spectra were recorded in a glass tube with a Bruker
MultiRAM FT-Raman spectrometer with ND:YAG laser with
excitation up to 1000 mW at 1064 nm in the range 4000−400
cm−1. All spectra were recorded at ambient temperature.
Analyses of C/H/N contents were performed with an Elementar
vario EL or Elementar vario micro cube. Melting and decomposition
points were measured with a Linseis DSC-PT10 apparatus with a
heating rate of 5 °C min−1 in a temperature range 25−400 °C and
partly by thermal gravimetric analysis (TGA) with a PerkinElmer
TGA4000.
The sensitivities toward impact and friction were determined with a
BAM drophammer24 and a BAM friction tester.25 The sensitivity
toward electrostatic discharge was determined with an electric spark
tester from OZM.
The toxicity assessments were carried out as described by the
provider using a LUMI-Stox 300 spectrometer, obtained by HACH
LANGE GmbH. According to DIN/EN/ISO 11348, a 10-point
dilution series was prepared (without G1 level) with a known weight
of the salts and a 2% NaCl stock solution.29
Tetrakis(aminoguanidinium) PETNC (3). 1H NMR ([D6]DMSO):
δ = 8.60 (br, 4H, NHNH2), 7.14 (br, 16H, C(NH2)2), 4.68 (s, 8H,
NHNH2), 3.84 (s, 8H, CH2) ppm. 13C NMR ([D6]DMSO): δ =
159.7 (CO), 158.9 (C(NH2)), 63.1 (CH2), 41.7 (C) ppm. 14N NMR
([D6]DMSO): δ = −2 (NO2) ppm. EA: C13H36N24O16 (784.58): calc.
C 19.90, H 4.62, N 42.85%. Found C 20.03, H 4.51, N 42.61%. IS: 40
J (grain size < 100 μm). FS: 360 N (grain size < 100 μm). ESD: 1.50 J
(grain size < 100 μm). DSC (5 °C min−1): 149 °C (dec.).
Tetralithium PETNC·2.5 hydrate (4). 1H NMR ([D6]DMSO): δ =
3.81 (s, 8H, CH2) ppm. 13C NMR ([D6]DMSO): δ = 159.8 (CO),
62.0 (CH2), 42.0 (C) ppm. 14N NMR ([D6]DMSO): δ = −7 (NO2)
ppm. EA: Li4C9H8N8O16·2.5 H2O (557.00): calc. C 19.41, H 2.35, N
20.12%. Found C 19.56, H 2.39, N 19.98%. IS: >20 J (grain size < 100
μm). FS: 360 N (grain size < 100 μm). ESD: 1.50 J (grain size < 100
μm). DSC (5 °C min−1): 186 °C (dec.).
1
Tetrasodium PETNC·x hydrate (5). H NMR ([D6]DMSO): δ =
3.88 (s, 8H, CH2) ppm. 13C NMR ([D6]DMSO): δ = 159.8 (CO),
62.2 (CH2), 42.1 (C) ppm. 14N NMR ([D6]DMSO): δ = −13 (NO2)
ppm. DSC (5 °C min−1): 156 °C (dec.).
Single crystal X-ray diffraction studies were performed on an
Oxford Diffraction XCalibur3 diffractometer with a generator (voltage
50 kV, current 40 mA) and a KappaCCD area detector operating with
Mo Kα radiation (λ = 0.7107 Å). The solution of the structure was
performed by direct methods using SIR9730,31 and refined by full-
matrix least-squares on F2 (ShelXL)32,33 implemented in the WinGX
1
Tetrapotassium PETNC·2 hydrate (6). H NMR ([D6]DMSO): δ
= 3.88 (s, 8H, CH2) ppm. 13C NMR ([D6]DMSO): δ = 158.8 (CO),
62.3 (CH2), 42.1 (C) ppm. 14N NMR ([D6]DMSO): δ = −12 (NO2)
E
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ppm. EA: K4C9H8N8O16·2 H2O (676.63): calc. C 15.98, H 1.79, N
16.56%. Found C 16.51, H 2.15, N 16.77%. IS: 7 J (grain size 100−
250 μm). FS: 360 N (grain size 100−250 μm). DSC (5 °C min−1):
177 °C (dec.).
ACKNOWLEDGMENTS
■
Financial support of this work by the Ludwig-Maximilian
University of Munich (LMU), the Office of Naval Research
(ONR) under grant no. ONR.N00014-16-1-2062, is gratefully
acknowledged. Furthermore, we acknowledge Ms. Teresa
Dicalcium PETNC·7 hydrate (7). 1H NMR ([D6]DMSO): δ = 3.86
(s, 8H, CH2) ppm. 13C NMR ([D6]DMSO): δ = 160.4 (CO), 62.3
(CH2), 42.1 (C) ppm. 14N NMR ([D6]DMSO): δ = −8 (NO2) ppm.
EA: Ca2C9H8N8O16·7 H2O (690.46): calc. C 15.66, H 3.21, N
16.23%. Found C 15.88, H 3.24, N 16.16%. IS: 40 J (grain size < 100
μm). FS: 360 N (grain size < 100 μm). ESD: 1.50 J (grain size < 100
μm). DSC (5 °C min−1): 167 °C (dec.).
Kublbock for her help with some calculations, Mr. Marcel
̈
̈
Holler for the excellent collaboration with the burning
behavior tests, and Mr. Florian Freund for working in part
on this project. This paper is dedicated to Mrs. Irene
Scheckenbach on the occasion of her 70th birthday.
1
Distrontium PETNC·7 hydrate (8). H NMR ([D6]DMSO): δ =
3.91 (s, 8H, CH2) ppm. 13C NMR ([D6]DMSO): δ = 160.5 (CO),
62.5 (CH2), 42.1 (C) ppm. 14N NMR ([D6]DMSO): δ = −7 (NO2)
ppm. EA: Sr2C9H8N8O16·7 H2O (785.55): calc. C 13.76, H 2.82, N
14.26%. Found C 13.29, H 2.41, N 12.43%. IS: 40 J (grain size < 100
μm). FS: 360 N (grain size < 100 μm). ESD: 1.50 J (grain size < 100
μm). DSC (5 °C min−1): 152 °C (dec.).
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1
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AUTHOR INFORMATION
■
Corresponding Authors
*E-mail: tmk@cup.uni-muenchen.de.
*E-mail: bkr@cup.uni-muenchen.de.
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̈
Thomas M. Klapotke: 0000-0003-3276-1157
Burkhard Krumm: 0000-0002-2100-4540
Cornelia C. Unger: 0000-0002-4950-1004
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Notes
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