3,4,5-Trinitropyrazole-based energetic salts

Article abstract of DOI:10.1002/chem.201001243

High-density energetic salts that are comprised of nitrogen-rich cations and the 3,4,5-trinitropyrazolate anion were synthesized in high yield by neutralization or metathesis reactions. The resulting salts were fully characterized by ¹H, ¹³C NMR, and IR spectroscopy; differential scanning calorimetry; and elemental analysis. Additionally, the structures of the 3,5-diaminotriazolium and triaminoguanidinium 3,4,5-trinitropyrazolates were confirmed by single-crystal X-ray diffraction. Based on the measured densities and calculated heats of formation, the detonation performances (pressure: 23.74-31.89 GPa; velocity: 7586-8543 ms ^-1; Cheetah 5.0) of the 3,4,5-trinitropyrazolate salts are comparable with 1,3,5triamino-2,4,6-trinitrobenzene (TATB; 31.15GPa and 8114 ms ^-1). Impact sensitivities were determined to be no less than 35 J by hammer tests, which places these salts in the insensitive class.

Full text of DOI:10.1002/chem.201001243

DOI: 10.1002/chem.201001243
3,4,5-Trinitropyrazole-Based Energetic Salts
Yanqiang Zhang,[a] Yong Guo,[a] Young-Hyuk Joo,[a] Damon A. Parrish,[b] and
Jeanꢀne M. Shreeve*[a]
Abstract: High-density energetic salts
that are comprised of nitrogen-rich cat-
ions and the 3,4,5-trinitropyrazolate
anion were synthesized in high yield by
neutralization or metathesis reactions.
The resulting salts were fully character-
nitropyrazolates were confirmed by
single-crystal X-ray diffraction. Based
on the measured densities and calculat-
ed heats of formation, the detonation
31.89 GPa; velocity: 7586–8543 msꢀ1
;
Cheetah 5.0) of the 3,4,5-trinitropyra-
zolate salts are comparable with 1,3,5-
triamino-2,4,6-trinitrobenzene (TATB;
31.15 GPa and 8114 msꢀ1). Impact sen-
sitivities were determined to be no less
than 35 J by hammer tests, which
places these salts in the insensitive
class.
performances
(pressure:
23.74–
1
ized by H, 13C NMR, and IR spectros-
Keywords: detonation
perfor-
copy; differential scanning calorimetry;
and elemental analysis. Additionally,
the structures of the 3,5-diaminotriazo-
lium and triaminoguanidinium 3,4,5-tri-
mance · energetic salts · heterocy-
cles · polynitro compounds · struc-
ture–property relationships
Introduction
Both the oxygen balance and density of energetic com-
pounds are enhanced by the presence of the nitro group,
which improves the detonation performances (pressure and
velocity) that are related to the square of and proportional
to the density.[8] Azoles, the five-membered nitrogen-con-
taining heterocycles, can be N-deprotonated, and nitroazo-
lates are excellent anions for energetic salts. A large number
of nitroazolate salts have been reported, including fully C-
nitrated azolates, for example, 2,4,5-trinitroimidazolate
(TNI), 3,5-dinitrotriazolate (DNT), and 5-nitrotetrazolate
(NT) salts.[9] Based on calculations, the 3,4,5-trinitropyrazo-
late (TNP, ꢀ63.1 kJmolꢀ1) has a less negative heat of forma-
Energetic nitrogen-rich salts, as families of environmentally
benign high energy density materials (HEDM), have attract-
ed considerable interest due to the lower vapor pressures,
higher heats of formation, and enhanced thermal stabilities
than their atomically similar nonionic analogues.[1–3] They
are often prepared by neutralization or metathesis reactions,
with N-protonated cations such as ammonium, hydrazinium,
guanidium, azolium, azinium, and so forth, and C-, N-, or
O-deprotonated anions, for example, nitroformate, azolate,
or picrate.[4–5] In pursuit of higher detonation performance
and lower sensitivity, many energetic salts with nitrogen-rich
cations or nitrogen-containing heterocyclic anions, have
been obtained through combination of carefully selected
ions.[6–7] Their full characterization provides knowledge of
the structure–property relationships in energetic salts.
tion
than
its
isomer,
2,4,5-trinitroimidazolate
ꢀ
ꢀ
(ꢀ148.5 kJmolꢀ1), NO3 (ꢀ307.9 kJmolꢀ1), and ClO4
(ꢀ277.8 kJmolꢀ1). 3,4,5-Trinitropyrazole with a calculated
density of 1.867 gcmꢀ3 is stable up to 2008C, making its salts
potential energetic materials.[10,11] However, 3,4,5-trinitropyr-
azolate salts were only mentioned in patents without charac-
terization and properties.[10] In our work, a series of high-ni-
trogen 3,4,5-trinitropyrazolate salts have now been prepared
and characterized. Their thermal stabilities, detonation per-
formances, and impact sensitivities were also investigated.
[a] Dr. Y. Zhang, Dr. Y. Guo, Dr. Y.-H. Joo, 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
[b] Dr. D. A. Parrish
Results and Discussion
Naval Research Laboratory, Code 6030
Washington, D.C. 20375-5001 (USA)
3,4,5-Trinitropyrazole (HTNP) was prepared from the nitra-
tion of pyrazole with fuming nitric acid, followed by thermal
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201001243.
10778
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 10778 – 10784

FULL PAPER
rearrangement of N-nitropyrazole in benzonitrile, amination
with 1,1,1-trimethylhydrazinium iodide, and finally oxidation
with 30% hydrogen peroxide (Scheme 1).[11,12]
aminotetrazolium, and 1,5-diamino-4-methyltetrazolium io-
dides, and diaminoguanidium and triaminoguanidinium
chlorides with AgACTHNUGTRENNUG(TNP) (or AgHCATUNGTRENN(UGN TNI), silver trinitroimidazo-
late), which was obtained from treatment of KTNP (or
KTNI) with an equivalent amount of aqueous silver nitrate.
All of the salts, which were isolated as crystalline materials
in good yields, are nonhygroscopic and stable in air. Un-
fortunately attempts to isolate the corresponding trinitropyr-
azolate salt of 1,5-diaminotetrazole (DAT) were unsuccess-
ful due to the extreme hygroscopicity of the product which
became a highly sticky material when exposed to air for sev-
eral seconds. The structures of the salts 1–14 were deter-
mined by 1H and 13C NMR spectroscopy (some with
15N NMR spectroscopy), IR spectroscopy, and elemental
1
analysis. In the H NMR spectra, the hydrogen signals of the
cations were observed and easily assigned, since there is no
proton associated with the TNP anion. In the 13C NMR
spectra, except for two very weak signals (d= ꢁ122 and
147 ppm) assigned to the TNP anion, the other signals are
associated with the cations.
Scheme 1. Synthesis of 3,4,5-trinitropyrazole.
Reactions of HTNP with ammonia, tri
ACHTUNGTRENNUNGazole, 4-aminotrizole, 3,5-diaminotriazole, guanidine carbon-
ACHTUNGTRENaNUGN zole, 3-aminotri-
ate, aminoguanidine bicarbonate, and 3,6-diguanidinotetra-
zine, resulted in the formation of salts 1–8 (Scheme 2).
Other salts 9–14 were readily synthesized by metathesis re-
actions of 3,4,5-triaminotriazolium chloride, 1,4-dimethyl-5-
In the IR spectra, several main absorption bands at
around 1520, 1360, 1320, and 850 cmꢀ1 are attributed to the
TNP anion. The intense absorption bands in the range of
3100–3500 cmꢀ1 can be assigned to the N H bonds of the ni-
ꢀ
trogen-rich cations. The structures of salts 5 and 13 were
confirmed with single-crystal X-ray diffraction.
In the 15N NMR spectra of salts, three signals (d=ꢁꢀ9.0,
ꢀ9.5, and ꢀ44.0 ppm) are assigned to the TNP anion, the
other signals are associated with the cations. HTNP, 9, 13,
and 14 taken as examples were measured in CD3CN or
[D6]DMSO with respect to CH3NO2 as external standard
(Figure 1). Comparing the TNP anion with HTNP, the sig-
nals of pyrazole ring and nitro groups shift downfield with a
difference of about 74 and 8 ppm. In comparison with the
TNP anion, the TNI anion has a similar chemical shift of
the nitro groups, and much lower chemical shift (d=
ꢁ69 ppm) of the ring nitrogen atoms. Interestingly, at 308C
in ([D6]DMSO), there are only five signals (d=ꢀ8.9, ꢀ9.5,
ꢀ43.0, ꢀ225.8, and ꢀ310.1 ppm) for 9, but all signals (seven)
are resolved at 808C.
Properties of TNP salts: The thermal stabilities of the TNP
salts were determined by differential scanning calorimetric
(DSC) measurements (Table 1). When the decomposition
peak in the DSC scan was not sharp, the salts were exam-
ined by using thermogravimetric analysis (TGA). While
salts 1 and 8 decomposed without melting at 224 and 2438C,
respectively, the other salts have melting and decomposition
temperatures ranging from 120 (11) to 2068C (9) and 167 (2
and 11) to 2438C (8). Densities for the TNP salts were mea-
sured with a gas pycnometer, and found in the range be-
tween 1.61 (10) and 1.77 gcmꢀ3 (4). The triazolium salts ex-
hibit a higher density than their guanidinium analogues, and
4-aminotriazolium TNP (4) has the highest density of
1.77 gcmꢀ3. Among the four guanidinium salts (6, 7, 12, and
13), diaminoguanidinium TNP (12) has the lowest density at
1.62 gcmꢀ3. The two tetrazolium salts (10 and 11) have low
Scheme 2. Synthesis of 3,4,5-trinitropyrazolate and triaminoguanidinium
2,4,5-trinitroimidazolate salts.
Chem. Eur. J. 2010, 16, 10778 – 10784
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
10779

J. M. Shreeve et al.
densities of 1.61 and 1.64 gcmꢀ3, respectively. These relative-
ly high densities are presumably caused by the high symme-
try of the anion and the extensive intra- and intermolecular
hydrogen bonds found in these salts. The oxygen balances
(OB) of the TNP salts were calculated to fall between ꢀ50.6
(10) and ꢀ14.5% (1).
The heats of formation (DHf) of the cations and anions
were calculated by using the Gaussian 03 (Revision D. 01)
suite of programs. The calculated DHf of nitrogen-rich cat-
ions varies between 575.9 (guanidinium, 6) and
1903.6 kJmolꢀ1 (diguanidinotetrazinium, 8). Compared with
2,4,5-trinitroimidazolate anion (ꢀ148.5 kJmolꢀ1),[9a] the cal-
culated DHf of the TNP anion is less negative
(ꢀ63.1 kJmolꢀ1). The heats of formation (DHf) of the TNP
salts are calculated by using Born–Haber energy cycles (see
the Experimental Section). They are positive, and fall in the
range 0.11 (6) to 1.45 kJgꢀ1 (11).
With the data of density, heat of formation, and oxygen
balance in hand, the detonation pressure (P) and velocity
(vD), and specific impulse (Isp) values of the TNP salts were
calculated with Cheetah 5.0. Just as for 13 and 14, the TNP
salts have weaker detonation properties than the corre-
sponding TNI salts arising mainly from lower densities.[9a]
Based on the data in Table 1, the calculated detonation pres-
sures and velocities lie in the range of 23.74–31.89 GPa and
7586–8543 msꢀ1, which are superior to that of trinitroben-
zene (TNT, 19.5 GPa and 6881 msꢀ1). Salt 4, with a detona-
tion pressure and velocity of 31.89 GPa and 8543 msꢀ1, is
comparable
with
1,3,5-triamino-2,4,6-trinitrobenzene
(TATB, 31.15 GPa and 8114 msꢀ1). The specific impulse
values of the TNP salts ranging between 228.9 and 269.6 s
suggest application of these energetic materials as propel-
lants. Impact sensitivities of the TNP salts were measured
by using a BAM Fallhammer apparatus with a 10 kg drop
weight and found to be no less than 35 J, which places them
in the insensitive class.
Figure 1. 15N NMR spectra of compounds HTNP, 9, 13, and 14.
It is interesting to compare
the impact of salt formation on
the properties, such as density
and heat of formation (and thus
detonation properties), of two
insensitive explosives (HTNP
(1.86 gcmꢀ3) and 3-nitro-1,2,4-
Table 1. Properties of trinitropyrazolate salts compared with triaminoguanidium TNI (14), TNT, and TATB.
[a]
[b]
[d]
[h]
Salt
Tm
Td
1[c]
[gcmꢀ3
DHL
[kJmolꢀ1
DHf[d]
DHf[d] (salt)
[kJmolꢀ1]/[kJgꢀ1
OB[e] P[f]
[%] [Gpa]
nD[g] Isp
IS[i]
[J]
[8C] [8C]
G
]
G
]
(cation)
E
G
]
G
A
]
[s]
AHCTUNGTERNNUNG ]
[kJmolꢀ1
1
2
3
4
5
6
7
8
–
158
171
168
188
163
136
–
206
166
120
122
125
125
224 1.73
167 1.69
171 1.71
168 1.77
196 1.76
235 1.66
222 1.69
243 1.68
206 1.76
219 1.61
167 1.64
197 1.62
184 1.65
214 1.71
502.7
473.1
468.0
471.9
465.2
476.5
470.9
1324.6
459.5
449.6
451.3
459.4
455.9
459.9
–
626.4
835.0
804.5
936.3
764.0
575.9
667.4
1903.6
877.6
887.7
974.3
769.0
871.5
871.5
–
60.5/0.28
299.0/1.10
273.5/0.95
401.2/1.40
235.6/0.78
28.3/0.11
133.6/0.48
452.3/0.75
355.0/1.12
375.0/1.19
459.8/1.45
246.5/0.84
352.7/1.15
263.1/0.86
–
ꢀ14.5 29.92 8461
ꢀ35.3 25.64 7871
ꢀ36.2 26.00 7972
ꢀ36.2 31.89 8543
ꢀ37.1 27.67 8216
ꢀ30.5 24.74 7865
ꢀ31.8 26.85 8134
ꢀ34.5 24.30 7817
ꢀ37.8 28.83 8359
ꢀ50.6 23.74 7586
ꢀ37.8 25.20 7922
ꢀ32.9 25.34 7983
ꢀ33.9 27.20 8236
ꢀ33.9 28.89 8441
263.0
40
245.0 >40
237.9 >40
269.6 >40
230.2 >40
235.6 >40
240.9 >40
228.9 >40
236.5 >40
230.5 >40
triazolate-5-one
(NTO,
1.93 gcmꢀ3)). Salts 2, 3, and 4
have lower densities than the
parent at 1.69. 1.71, and
1.77 gcmꢀ3, while the densities
of the analogous NTO salts are
also markedly reduced to 1.67,
1.71 and 1.68 gcmꢀ3, although it
would appear that strong hy-
drogen bonding should contrib-
ute to enhancing the densi-
ties.[13] While both parent explo-
sives have slightly negative
heats of formation (ꢀ0.07 kJgꢀ1
9
10
11
12
13
14
TNT
TATB
245.2
35
246.3 >40
250.5 >40
243.2 >40
–
–
80.4 295 1.65
318 1.94
ꢀ74.0 19.5
6881
15
50
–
–
–
–
ꢀ55.8 31.15 8114
[a] Melting temperature (nitrogen gas: DSC, 108Cminꢀ1). [b] Decomposition temperature (nitrogen gas: DSC
or TGA, 108C minꢀ1). [c] Density (258C). [d] Heat of formation. [e] Oxygen balance for CaHbOcNd, 1600-
ACHTUNGTRENNUNG
10780
www.chemeurj.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 10778 – 10784

3,4,5-Trinitropyrazole-Based Energetic Salts
FULL PAPER
and ꢀ0.78 kJgꢀ1, respectively), the salts have increased posi-
tive values in the 0.95 to 1.40 kJgꢀ1 and 1.70 to 2.33 kJgꢀ1
ranges, respectively. However, while the salts have good
thermal stabilities, none have detonation properties equiva-
lent to the parent.
X-ray crystallography: Crystals of both 5 and 13, suitable
for single-crystal X-ray diffraction, were obtained by slow
evaporation of aqueous solutions at room temperature.
Their structures are shown in Figures 2 and 3, and crystallo-
Figure 3. a) Thermal ellipsoid plot (30%) and labeling scheme for triami-
noguanidium TNP (13). Hydrogen atoms included but are unlabelled for
clarity. b) Ball and stick packing diagram of 13 viewed down the a axis.
Dashed lines indicate strong hydrogen bonding.
Table 2. Crystallographic data for 5 and 13.
5
13
formula
C5H6N10O6
768959
C4H9N11O6
768960
CCDC number[a]
Mr
302.20
307.18
crystal size [mmꢀ3
crystal system
space group
a [ꢀ]
]
0.21ꢁ0.14ꢁ0.03
triclinic
0.50ꢁ0.17ꢁ0.11
triclinic
¯
¯
P1
P1
5.1125(17)
10.676(4)
11.579(4)
66.294(5)
78.501(5)
84.852(5)
567.1(3)
2
7.4774(17)
9.402(2)
9.848(2)
65.955(3)
81.813(3)
70.094(3)
594.5(2)
2
b [ꢀ]
c [ꢀ]
a [8]
b [8]
g [8]
V [ꢂ3]
Z
T [K]
293(2)
1.770 (208C)
0.160
100(2)
1.660 (208C)
0.155
1calcd [mgmꢀ3
]
m [mmꢀ1
(000)
q [8]
index ranges
]
F
A
308
314
1.95 to 26.35
ꢀ6ꢂhꢂ6
ꢀ12ꢂkꢂ13
ꢀ14ꢂlꢂ14
5161
2312 (0.0206)
2312/0/190
1.033
2.26 to 28.42
ꢀ9ꢂhꢂ9
ꢀ12ꢂkꢂ12
ꢀ11ꢂlꢂ13
6292
2911 (0.0123)
2911/12/237
1.056
Figure 2. a) Thermal ellipsoid plot (30%) and labeling scheme for 3,5-di-
aminotriazolium TNP (5). Hydrogen atoms included but are unlabelled
for clarity. b) Ball and stick packing diagram of 5 viewed down the a axis.
Dashed lines indicate strong hydrogen bonding.
reflections collected
independent reflections (Rint
data/restraints/parameters
GOF on F2
)
R1 (I>2d(I))[b]
0.0536
0.1414
0.0827
0.0313,
0.0838
0.0344
wR2 (I>2d(I))[c]
R1 (all data)
graphic data are summarized in Table 2. Both of them crys-
tallize in the triclinic P1 space group with one cation per
TNP anion. The transfer of each proton from the NH group
of HTNP to the ring nitrogen of 3,5-diaminotriazole and tri-
aminoguanidine is confirmed in Figures 2a and 3a. For 5,
wR2 (all data)
0.1618
0.0862
¯
Largest diff. peak and hole [eꢂꢀ3
]
0.244 and ꢀ0.249 0.349 and 0.331
[a] These data can be obtained free of charge from The Cambridge Crys-
tallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
ꢀ
P
ꢁ
P
P
P
1
=
2
2
wðFo2 ꢀ Fc2Þ = wðFo2Þ
.
2
[b] R1
¼
jjFoj ꢀ jFcjj= jFoj. [c] wR2 ¼
Chem. Eur. J. 2010, 16, 10778 – 10784
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
10781

J. M. Shreeve et al.
tra were recorded by using KBr pellets on a Bio-Rad model 3000 FTS
spectrometer. Densities were measured at room temperature with a Mi-
cromeritics Accupyc 1330 gas pycnometer. Elemental analyses were ob-
tained by using a CE-440 elemental analyzer (EAI Exeter Analytical).
the pyrazole and the triazole rings are in the same plane. In
the TNP anion, 3(5)-nitro groups are in the plane of the pyr-
azole ring, and the 4-nitro group is twisted out of the plane
of the pyrazole ring (116.28). Each cation in 5 can form a va-
riety of hydrogen bonds (N1···O18, 2.911(3); N4···N8,
2.777(3); N6···N2, 2.995(3); N7···N9, 3.029(3) ꢂ). For 13, all
three nitro groups are tilted to the plane of the pyrazole
(19.7, 43.3, and 22.68). Its packing structure is configured by
hydrogen bonds (N17···N1, 2.965(3); N17···O11, 3.172(3);
N18···N2, 2.8997(15); N19···O14, 2.960(5); N21···O7,
3.169(4); N21···O10, 3.141(4); N16B···O10, 2.995(6);
N18B···N2, 3.121(6); N20B···O11, 3.259(6) ꢂ). The extensive
hydrogen-bonding interactions between cations and anions
form a complex 3D network. Further details are provided in
the Supporting Information.
X-ray crystallography: An orange plate of dimensions 0.21ꢁ0.14ꢁ
0.03 mm3 (5) and a yellow prism of dimensions 0.50ꢁ0.17ꢁ0.11 mm3 (13)
were mounted on a MiteGen MicroMesh by using a small amount of Car-
gille immersion oil. Data were collected on a Bruker three-circle plat-
form diffractometer equipped with a SMART APEX II CCD detector.
The crystals were irradiated by using graphite monochromated MoKa ra-
diation (l=0.71073). An Oxford Cobra low-temperature device was used
to keep the crystals at a constant 293(2) and 100(2) K during data collec-
tion. Data collection was performed and the unit cell was initially refined
by using APEX2 [v2009.3-0].[14] Data reduction was performed by using
SAINT [v7.60 A][15] and XPREP [v2008/2].[16] Corrections were applied
for Lorentz, polarization, and absorption effects by using SADABS
[v2008/1].[17] The structure was solved and refined with the aid of the pro-
grams in the SHELXTL-plus [v2008/4] system of programs.[18] The full-
matrix least-squares refinement on F2 included atomic coordinates and
anisotropic thermal parameters for all non-hydrogen atoms. The hydro-
gen atoms were included by using a riding model.
Conclusion
Theoretical study: Calculations were performed with the Gaussian 03
(Revision D.01) suite of programs.[19] The geometric optimization of the
structures based on single-crystal structures, where available, and fre-
quency analyses were carried out by using the B3LYP functional with 6-
31+G** basis set,[20] and single energy points were calculated at the
MP2/6-311++G** level. All of the optimized structures were character-
ized to be true local energy minima on the potential energy surface with-
A family of energetic salts based on nitrogen-rich cations
and the TNP anion was prepared and fully characterized.
The structures of 5 and 13 were confirmed by single-crystal
X-ray diffraction, which showed that there are extensive hy-
drogen-bonding interactions between the cation and anion
in these salts. Densities for the TNP salts, measured with a
gas pycnometer, were found to fall in the range between
1.61 (10) and 1.77 gcmꢀ3 (4), which places them in a class of
relatively dense compounds. By using Cheetah 5, their deto-
nation pressures and velocities were calculated to fall in the
range of 23.74–31.9 GPa and 7586–8543 msꢀ1. Salt 4, with a
detonation pressure and velocity of 31.89 GPa and
8543 msꢀ1, is comparable with TATB (31.15 GPa and
8114 msꢀ1). The specific impulse values of the TNP salts
range between 228.9 and 269.6 s. Except for 1 (40 J) and 11
(35 J), the impact sensitivities of the TNP salts are more
than 40 J. Based on rather high detonation properties, low
impact sensitivities, and high stabilities, the TNP salts have
potential as energetic materials.
out imaginary frequencies. Based on
a Born–Haber energy cycle
(Scheme 3), the heat of formation of a salt can be simplified by the for-
mula given in Equation (1):
DHf0ðsalt; 298KÞ ¼ DHf0ðcation; 298KÞ þ DHf0ðanion; 298KÞ ꢀ DHL
ð1Þ
Scheme 3. Born–Haber cycle for the formation of energetic salts.
Experimental Section
in which DHL is the lattice energy of the salts, which could be predicted
by using the formula suggested by Jenkins et al. [Eq. (2)]:[21]
Caution! Although none of the compounds described herein have ex-
ploded or detonated in the course of this research, these materials should
be handled with extreme care using the best safety practices.
DHL ¼ Upot þ ½pðnM=2 ꢀ 2Þ þ qðnX=2 ꢀ 2ÞꢃRT
ð2Þ
Reactants: Pyrazole (98%, Alfa Aesar), aqueous ammonia (28–30%,
EMD), 1,2,4-1H-triazole (99.5%), 3-amino-1,2,4-1H-triazole (95%), 4-
amino-1,2,4-4H-triazole (99%), 3,5-diamino-1,2,4-1H-triazole (98%),
guanidinium carbonate (99%), aminoguanidinium bicarbonate (98.5%),
(all from Acros), and silver nitrate (99.95%, Salt Lake Metals) were
used as received.
General methods: 1H, 13C, and 15N NMR spectra were recorded on a 300
(Brucker AVANCE 300) and 500 MHz (Brucker AVANCE 500) NMR
spectrometer operating at 300.13, 75.48, and 50.69 MHz, respectively,
using [D6]DMSO as a locking solvent unless otherwise stated. Chemical
shifts were reported relative to Me4Si. The melting and decomposition
points were recorded on a differential scanning calorimeter at a scan rate
of 108C minꢀ1 in closed aluminum containers. TGA measurements were
carried out by heating samples at 108Cminꢀ1 from 25 to 6008C. IR spec-
in which nM and nX depend on the nature of the ions Mp+ and Xqꢀ, re-
spectively, and are equal to three for monoatomic ions, five for linear
polyatomic ions, and six for nonlinear polyatomic ions. The equation for
lattice potential energy UPOT [Eq. (3)] has the form:
1=3
UPOT ½kJ molꢀ1ꢃ ¼ gð1m=MmÞ þ d
ð3Þ
in which 1m [gcmꢀ3] is the density, Mm is the chemical formula mass of
the ionic material, and values for g and the coefficients g [kJmolꢀ1 cm]
and d [kJmolꢀ1] are taken from the literature.
The heats of formation of the cations were computed by using the
method of isodesmic reactions. The enthalpy of reaction (DHr2988) is ob-
tained by combining the MP2/6-311++G** energy difference for the re-
10782
www.chemeurj.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 10778 – 10784

3,4,5-Trinitropyrazole-Based Energetic Salts
FULL PAPER
action, the scaled zero-point energies, and other thermal factors. Thus,
the heats of formation of the species being investigated can be readily ex-
tracted. With values of the heats of formation and densities, the detona-
tion pressure (P) and velocity (nD), and specific impulse (Isp) were calcu-
lated based on the traditional Chapman–Jouget thermodynamic detona-
tion theory by using Cheetah 5.0.[22]
Aminoguanidinium 3,4,5-trinitropyrazolate (7): Light yellow plates
(258 mg, 93%); 1H NMR: d=8.53 (s, 1H; NH), 7.12 (s, 2H; NH2), 6.75
(s, 2H; NH2), 4.67 ppm (s, 2H; NH2); 13C NMR: d=158.7, 147.0,
122.1 ppm; IR (KBr pellet): 3500, 3468, 3372, 1663, 1513, 1455, 1361,
; elemental analysis calcd (%) for
C4H7N9O6 (277.16): C 17.33, H 2.55, N 45.48; found: C 17.26; H 2.47; N
45.24.
1313, 1128, 959, 844, 646 cmꢀ1
3,4,5-Trinitropyrazole: 4-Amino-3,5-dinitropyrazole[12c] (0.50 g, 2.6 mmol,
H2O monosolvate) was added to a mixture of 30% H2O2 (3.5 mL) and
concentrated H2SO4 (6.8 mL), with stirring and cooling in an ice bath.
After 24 h, the reaction mixture was poured into cold water (35 mL) and
extracted with diethyl ether (3 x15 mL). The organic solution was dried
over anhydrous MgSO4. The solvent was removed under vacuum and the
product was isolated as a light yellow solid (0.49 g, 2.4 mmol, 93%),
which can be recrystallized from diethyl ether and benzene. 1H NMR:
d=9.42 ppm (s, 1H); 13C NMR: d=147.2, 122.5 ppm; 15N NMR
(CD3CN): d=ꢀ26.6, ꢀ26.7, ꢀ129.6 ppm; IR (KBr pellet): 3147, 1595,
1554, 1494, 1455, 1359, 1334, 1202, 1128, 1024, 843, 790, 763, 558,
3,6-Diguanidino-1,2,4,5-tetrazine di-3,4,5-trinitropyrazolate (8): Red
plates (306 mg, 96%); 1H NMR: d=8.17 ppm (s); 13C NMR: d=122.1,
147.0, 154.3, 158.5 ppm; IR (KBr pellet): 601, 846, 1035, 1075, 1320, 1358,
1518, 1541, 1616, 1698, 3431 cmꢀ1; elemental analysis calcd (%) for
C10H10N20O12·2H2O (638.34): C 18.82, H 2.21, N 43.88; found: C 18.81, H
2.03, N 43.73.
General procedure for synthesis of the salts 9–13: A solution of 3,4,5-tri-
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
505 cmꢀ1
.
silver 3,4,5-trinitropyrazolate (1 mmol) suspension in water (25 mL).
After the mixture was stirred at room temperature for 6 h, silver chloride
was removed by filtration, and washed with water. The filtrate was slowly
evaporated to leave the solid product in a good yield.
Ammonium 3,4,5-trinitropyrazolate (1): 3,4,5-Trinitropyrazole (203 mg,
1 mmol) and aqueous ammonia (61 mg, 1 mmol) were placed in water
(5 mL). The mixture was stirred at room temperature for 0.5 h; water
was removed under reduced pressure. The residual solid was crystallized
3,4,5-Triaminotriazolium 3,4,5-trinitropyrazolate (9): Light yellow needles
(304 mg, 96%); 1H NMR: d=5.57 (s, 2H, NH2), 7.06 ppm (brs, 4H,
NH2); 13C NMR: d=122.1, 147.0, 150.0 ppm; 15N NMR (308C): d=ꢀ8.9,
ꢀ9.5, ꢀ43.0, ꢀ225.7, ꢀ310.0 ppm; 15N NMR (808C): d=ꢀ8.9, ꢀ9.0,
ꢀ43.3, ꢀ188.5, ꢀ225.2, ꢀ310.0, ꢀ317.5 ppm; IR (KBr pellet): 3458, 3418,
1
with ethyl acetate (white plates, 187 mg, 85%). H NMR: d=7.09 ppm (t,
J=98.76 Hz, 4H); 13C NMR: d=122.1, 147.0 ppm; IR (KBr pellet): 765,
806, 849, 1026, 1128, 1165, 1318, 1355, 1421, 1456, 1512, 1527, 2812, 3262,
3318 cmꢀ1; elemental analysis calcd (%) for C3H4N6O6 (220.10): C 16.37,
H 1.83, N 38.18; found: C 16.39, H 1.67, N 37.90.
3365, 3328, 1677, 1631, 1554, 1519, 1455, 1354, 1319, 1172, 962, 848 cmꢀ1
;
General procedure for synthesis of the salts 2–8: Triazole (1 mmol), 3-
aminotriazole (1 mmol), 4-aminotriazole (1 mmol), 3,5-diaminotriazole
(1 mmol), or aminoguanidinium bicarbonate (1 mmol), or guanidinudium
carbonate (0.5 mmol) or 3,6-diguanidino-1,2,4,5-tetrazine (0.5 mmol) was
added to a solution of 3,4,5-trinitropyrazole (1 mmol) in water (10 mL).
The mixtures were stirred at room temperature until transparent solu-
tions were formed. If not, more water was added to the mixtures. Then,
water was slowly evaporated to leave the solid product in good yield.
elemental analysis calcd (%) for C5H7N11O6 (317.18): C 18.93, H 2.22, N
48.58; found: C 18.94, H 2.07, N 48.49.
1,4-Dimethyl-5-aminotetrazolium 3,4,5-trinitropyrazolate (10): Light
1
yellow needles (297 mg, 94%); H NMR: d=3.86 (s, 6H, CH3), 9.09 ppm
(brs, 2H, NH2); 13C NMR: d=33.9, 122.1, 146.8, 148.4 ppm; IR (KBr
pellet): 504, 847, 1309, 1350, 1452, 1510, 1545, 1699, 3017, 3376,
3392 cmꢀ1; elemental analysis calcd (%) for C6H8N10O6 (316.19): C 22.79,
H 2.55, N 44.30; found: C 22.95, H 2.55, N 43.96.
1,2,4–1H-Triazolium 3,4,5-trinitropyrazolate (2): Light yellow plates
1
(253 mg, 93%); H NMR: d=9.39 (s, 2H), 14.75 ppm (s, 2H); 13C NMR:
1,5-Diamino-4-methyltetrazolium 3,4,5-trinitropyrazolate (11): Light
yellow plates (292 mg, 92%); 1H NMR: d=3.86 (s, 3H, CH3), 7.01 (s,
2H, NH2), 8.99 ppm (s, 2H, NH2); 13C NMR: d=34.5, 122.0, 146.9,
147.5 ppm; IR (KBr pellet): 507, 767, 846, 1301, 1327, 1365, 1455, 1515,
1709, 2957, 3184, 3336, 3435 cmꢀ1; elemental analysis calcd (%) for
C5H7N11O6 (317.18): C 18.93, H 2.22, N 48.58; found: C 19.24, H 2.26, N
48.48.
d=122.1, 142.9, 147.0 ppm; 15N NMR: d=ꢀ9.0, ꢀ9.6, ꢀ43.8, ꢀ113.3,
ꢀ181.5 ppm; IR (KBr pellet): 628, 846, 941, 1126, 1323, 1353, 1462, 1525,
1555, 2638, 2904, 3154 cmꢀ1; elemental analysis calcd (%) for C5H4N8O6
(272.14): C 22.07, H 1.48, N 41.18; found: C 22.10, H 1.35, N 40.69.
3-Amino-1,2,4–1H-Triazolium 3,4,5-trinitropyrazolate (3): Yellow plates
(261 mg, 91%); 1H NMR: d=8.27 ppm (s, 1H; CH); 13C NMR: d=
122.1, 139.1, 147.0, 150.7 ppm; 15N NMR: d=ꢀ9.2, ꢀ9.8, ꢀ45.1, ꢀ97.4,
ꢀ192.5, ꢀ221.7, ꢀ310.2 ppm; IR (KBr pellet): 470, 615, 678, 847, 947,
1132, 1323, 1349, 1456, 1520, 1672, 3120, 3365, 3429 cmꢀ1; elemental anal-
ysis calcd (%) for C5H5N9O6 (287.15): C 20.91, H 1.76, N 43.90; found: C
20.90, H 1.62, N 43.66.
Diaminoguanidinium 3,4,5-trinitropyrazolate (12): Light yellow plates
(277 mg, 95%); 1H NMR: d=4.54 (s, 4H; NH2), 7.13 (s, 2H; NH2),
8.54 ppm (s, 2H, NH); 13C NMR: d=122.1, 147.1, 159.9 ppm; IR (KBr
pellet): 677, 846, 924, 1201, 1320, 1357, 1451, 1516, 1678, 3212, 3385,
3503 cmꢀ1; elemental analysis calcd (%) for C4H8N10O6 (292.17): C 16.44,
H 2.76, N 47.94; found: C 16.48, H 2.63, N 47.83.
4-Amino-1,2,4–4H-triazolium 3,4,5-trinitropyrazolate (4): Light yellow
needles (273 mg, 95%); 1H NMR: d=6.71 (brs, 3H), 9.50 ppm (s, 2H;
CH); 13C: d=122.0, 143.9, 146.9 ppm; 15N NMR: d=ꢀ9.1, ꢀ9.8, ꢀ44.9,
ꢀ113.6, ꢀ175.3, ꢀ295.0 ppm; IR (KBr pellet): 615, 762, 845, 927, 1020,
1203, 1327, 1365, 1454, 1523, 3170, 3297, 3426 cmꢀ1; elemental analysis
calcd (%) for C5H5N9O6 (287.15): C 20.91, H 1.76, N 43.90; found: C
20.92, H 1.59, N 43.60.
Triaminoguanidinium 3,4,5-trinitropyrazolate (13): Light yellow plates
(261 mg, 85%); 1H NMR: d=4.47 (s, 6H, NH2), 8.58 ppm (s, 3H, NH);
13C NMR: d=122.1, 147.0, 159.0 ppm; 15N NMR (CD3CN): d=ꢀ17.9,
ꢀ18.8, ꢀ286.2, ꢀ327.9 ppm; IR (KBr pellet): 545, 636, 798, 844, 951,
1129, 1296, 1324, 1364, 1452, 1509, 1684, 3211, 3362 cmꢀ1; elemental anal-
ysis calcd (%) for C4H9N11O6 (307.18): C 15.64, H 2.95, N 50.16; found: C
15.70, H 2.82, N 49.85.
3,5-Diamino-1,2,4–1H- triazolium 3,4,5-trinitropyrazolate (5): Orange
plates (278 mg, 92%); 1H NMR: d=6.58 ppm (brs, 4H; NH2); 13C: d=
122.1, 147.1, 151.4 ppm; 15N NMR: d=ꢀ9.1, ꢀ9.8, ꢀ44.7, ꢀ187.2, ꢀ231.6,
ꢀ314.9 ppm; IR (KBr pellet): 765, 800, 846, 1128, 1322, 1361, 1451, 1510,
1668, 1691, 3261, 3440 cmꢀ1; elemental analysis calcd (%) for C5H6N10O6
(302.16): C 19.87, H 2.00, N 46.35; found: C 19.85, H 1.87, N 46.02.
Triaminoguanidinium 2,4,5-trinitroimidazolate (14): A solution of triami-
noguanidinium chloride (1 mmol) was added dropwise to a silver 2,4,5-
trinitroimidazolate (1 mmol) suspension in water (25 mL). After the mix-
ture was stirred at room temperature for 6 h, silver chloride was filtered
off and washed with water. The filtrate was slowly evaporated to leave
light yellow plates (267 mg, 87%). 1H NMR: d=4.48 (s, 6H, NH2),
8.58 ppm (s, 3H, NH); 13C NMR: d=137.8, 146.4, 159.0 ppm; 15N NMR
(CD3CN): d=ꢀ16.3, 16.9, ꢀ125.4, ꢀ286.3, ꢀ328.0 ppm; IR (KBr pellet):
648, 806, 864, 943, 1014, 1139, 1290, 1325, 1462, 1536, 1686, 3334,
3379 cmꢀ1; elemental analysis calcd (%) for C4H9N11O6 (307.18): C 15.64,
H 2.95, N 50.16; found: C 15.73, H 2.87, N 49.83.
Guanidinium 3,4,5-trinitropyrazolate (6): Light yellow plates (246 mg,
1
94%); H NMR: d=6.89 ppm (s); 13C NMR: d=122.1, 147.0, 158.0 ppm;
IR (KBr pellet): 579, 677, 761, 849, 1024, 1128, 1315, 1353, 1452, 1514,
1546, 1655, 3177, 3427, 3477 cmꢀ1; elemental analysis calcd (%) for
C4H6N8O6 (262.14): C 18.33, H 2.31, N 42.75; found: C 18.39, H 2.17, N
42.48.
Chem. Eur. J. 2010, 16, 10778 – 10784
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
10783

J. M. Shreeve et al.
[7] a) H. X. Gao, Y. H. Joo, B. Twamley, Z. Q. Zhou, J. M. Shreeve,
Angew. Chem. 2009, 121, 2830–2833; Angew. Chem. Int. Ed. 2009,
48, 2792–2795; b) Y. G. Huang, H. X. Gao, B. Twamley, J. M.
Shreeve, Chem. Eur. J. 2009, 15, 917–923; c) Y. H. Joo, J. M.
Shreeve, Chem. Eur. J. 2009, 15, 3198–3203; d) R. H. Wang, Y. Guo,
Z. Zeng, J. M. Shreeve, Chem. Commun. 2009, 2697–2699; e) Y. H.
Joo, B. Twamley, J. M. Shreeve, Chem. Eur. J. 2009, 15, 9097–9104;
f) R. H. Wang, Y. Guo, Z. Zeng, B. Twamley, J. M. Shreeve, Chem.
Eur. J. 2009, 15, 2625–2634.
[8] a) M. J. Kamlet, S. J. Jacobs, J. Chem. Phys. 1968, 48, 23–35; b) M. J.
Kamlet, J. E. Ablard, J. Chem. Phys. 1968, 48, 36–42; c) M. J.
Kamlet, Dickinso. C, J. Chem. Phys. 1968, 48, 43–50.
[9] a) H. X. Gao, C. F. Ye, O. D. Gupta, J. C. Xiao, M. A. Hiskey, B.
Twamley, J. M. Shreeve, Chem. Eur. J. 2007, 13, 3853–3860; b) H.
Xue, B. Twamley, J. M. Shreeve, J. Mater. Chem. 2005, 15, 3459–
3465; c) C. Darwich, T. M. Klapçtke, J. M. Welch, M. Suceska, Pro-
pellants Explos. Pyrotech. 2007, 32, 235–243; d) T. M. Klapçtke, P.
Mayer, C. M. Sabate, J. M. Welch, N. Wiegand, Inorg. Chem. 2008,
47, 6014–6027.
[10] a) G. Hervꢃ, FR Patent 2917409, 2008; b) G. Hervꢃ, WO Patent
2008152525, 2008; c) G. Hervꢃ, US Patent 20090186931, 2009.
[11] G. Hervꢃ, C. Roussel, H. Graindorge, Angew. Chem. 2010, 122,
3245–3249; Angew. Chem. Int. Ed. 2010, 49, 3177–3181.
[12] a) J. W. A. Janssen, C. L. Habraken, J. Org. Chem. 1971, 36, 3081–
3084; b) J. W. A. Janssen, H. J. Koeners, C. G. Kruse, C. L. Habrak-
en, J. Org. Chem. 1973, 38, 1777–1782; c) R. D. Schmidt, G. S. Lee,
P. R. Pagoria, A. R. Mitchell, R. Gilardi, J. Heterocycl. Chem. 2001,
38, 1227–1230.
Acknowledgements
The authors gratefully acknowledge the support of DTRA (HDTRA1-
07-1-0024), and ONR (N00014-10-1-0097).
[1] a) K. O. Christe, W. W. Wilson, J. A. Sheehy, J. A. Boatz, Angew.
Chem. 1999, 111, 2112–2118; Angew. Chem. Int. Ed. 1999, 38, 2004–
2009; b) D. E. Chavez, M. A. Hiskey, R. D. Gilardi, Angew. Chem.
2000, 112, 1861–1863; Angew. Chem. Int. Ed. 2000, 39, 1791–1793;
c) J. Giles, Nature 2004, 427, 580–581; d) M. H. V. Huynh, M. A.
Hiskey, E. L. Hartline, D. P. Montoya, R. Gilardi, Angew. Chem.
2004, 116, 5032–5036; Angew. Chem. Int. Ed. 2004, 43, 4924–4928.
[2] a) T. M. Klapçtke, C. M. Rienacker, Propellants Explos. Pyrotech.
2001, 26, 43–47; b) A. Hammerl, G. Holl, M. Kaiser, T. M. Kla-
pçtke, P. Mayer, H. Noth, M. Warchhold, Z. Anorg. Allg. Chem.
2001, 627, 1477–1482; c) A. Hammerl, G. Holl, M. Kaiser, T. M.
Klapçtke, H. Piotrowskia, Z. Anorg. Allg. Chem. 2003, 629, 2117–
2121; d) T. M. Klapçtke, C. Kuffer, P. Mayer, K. Polborn, A. Schulz,
J. J. Weigand, Inorg. Chem. 2005, 44, 5949–5958; e) T. M. Klapçtke,
P. Mayer, A. Schulz, J. J. Weigand, J. Am. Chem. Soc. 2005, 127,
2032–2033; f) T. M. Klapçtke, K. Karaghiosoff, P. Mayer, A.
Penger, J. M. Welch, Propellants Explos. Pyrotech. 2006, 31, 188–
195.
[3] a) H. Xue, S. W. Arritt, B. Twalmley, J. M. Shreeve, Inorg. Chem.
2004, 43, 7972–7977; b) C. M. Jin, C. F. Ye, C. Piekarski, B. Twam-
ley, J. M. Shreeve, Eur. J. Inorg. Chem. 2005, 3760–3767; c) H. Xue,
J. M. Shreeve, Adv. Mater. 2005, 17, 2142- 2146; d) H. X. Gao, C. F.
Ye, R. W. Winter, G. L. Gard, M. E. Sitzmann, J. M. Shreeve, Eur. J.
Inorg. Chem. 2006, 3221–3226; e) Y. Gao, C. F. Ye, B. Twamley,
J. M. Shreeve, Chem. Eur. J. 2006, 12, 9010–9018; f) R. P. Singh,
R. D. Verma, D. T. Meshri, J. M. Shreeve, Angew. Chem. 2006, 118,
3664–3682; Angew. Chem. Int. Ed. 2006, 45, 3584–3601; g) H. Xue,
H. X. Gao, B. Twamley, J. M. Shreeve, Eur. J. Inorg. Chem. 2006,
2959–2965.
[4] a) T. M. Klapçtke, J. Stierstorfer, Helv. Chim. Acta 2007, 90, 2132–
2150; b) M. Gçbel, T. M. Klapçtke, Z. Anorg. Allg. Chem. 2007,
633, 1006–1017; c) G. Steinhauser, T. M. Klapçtke, Angew. Chem.
2008, 120, 3376–3394; Angew. Chem. Int. Ed. 2008, 47, 3330–3347;
d) C. Darwich, T. M. Klapçtke, C. M. Sabate, Chem. Eur. J. 2008, 14,
5756–5771; e) T. M. Klapçtke, C. M. Sabate, Eur. J. Inorg. Chem.
2008, 5350–5366; f) T. M. Klapçtke, J. Stierstorfer, A. U. Wallek,
Chem. Mater. 2008, 20, 4519–4530.
[5] a) Z. Zeng, H. X. Gao, B. Twamley, J. M. Shreeve, J. Mater. Chem.
2007, 17, 3819–3826; b) Y. Guo, H. X. Gao, B. Twamley, J. M.
Shreeve, Adv. Mater. 2007, 19, 2884–2888; c) Y. G. Huang, H. X.
Gao, B. Twamley, J. M. Shreeve, Eur. J. Inorg. Chem. 2007, 2025–
2030; d) H. X. Gao, Y. G. Huang, C. F. Ye, B. Twamley, J. M.
Shreeve, Chem. Eur. J. 2008, 14, 5596–5603; e) H. X. Gao, Z. Zeng,
B. Twamley, J. M. Shreeve, Chem. Eur. J. 2008, 14, 1282–1290; f) Y.
Huang, H. X. Gao, B. Twamley, J. M. Shreeve, Eur. J. Inorg. Chem.
2008, 2560–2568.
[13] H. Xue, H. Gao, B. Twamley, J. M. Shreeve, Chem. Mater. 2007, 19,
1731–1739.
[14] Bruker, APEX2 v2009/3-0, Bruker AXS Inc., Madison, 2009.
[15] Bruker, SAINT v7.60A, Bruker AXS Inc., Madison, 2009.
[16] Bruker, XPREP v2008/2, Bruker AXS Inc., Madison, 2008.
[17] Bruker, SADABS v2008/1, Bruker AXS Inc., Madison, 2008.
[18] Bruker, SHELXTL v2008/4, Bruker AXS Inc., Madison, 2008.
[19] Gaussian 03, Revision D.01, M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgom-
ery, Jr., K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J.
Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega,
G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R.
Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao,
H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross,
V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann,
O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y.
Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg,
V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O.
Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Fores-
man, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski,
B. B. Stefanov, A. L. G. Liu, P. Piskorz, I. Komaromi, R. L. Martin,
D. J. Fox, T. Keith, M. A. Al-Laham, C. Peng, A. Nanayakkara, M.
Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. Wong, C. Gon-
zalez, J. A. Pople, Gaussian, Inc., Wallingford, CT, 2004.
[20] R. G. Parr, W. Yang, Density Functional Theory of Atoms and Mole-
cules, Oxford University Press, New York, 1989.
[21] H. D. B. Jenkins, D. Tudela, L. Glasser, Inorg. Chem. 2002, 41,
2364–2367.
[22] CHEETAH 5.0 Userꢄs Manual, S. Bastea, L. E. Fried, K. R. Glaese-
mann, W. M. Howard, P. C. Souers, P. A. Vitello, Lawrence Liver-
more National Laboratory, 2007.
[6] a) J. Stierstorfer, K. R. Tarantik, T. M. Klapçtke, Chem. Eur. J. 2009,
15, 5775–5792; b) T. M. Klapçtke, C. M. Sabate, New J. Chem. 2009,
33, 1605–1617; c) T. M. Klapçtke, C. M. Sabate, Z. Anorg. Allg.
Chem. 2009, 635, 1812–1822; d) T. M. Klapçtke, J. Stierstorfer,
Dalton Trans. 2009, 643–653; e) T. M. Klapçtke, C. M. Sabate, A.
Penger, M. Rusan, J. M. Welch, Eur. J. Inorg. Chem. 2009, 880–896;
f) T. M. Klapçtke, C. M. Sabate, Z. Anorg. Allg. Chem. 2010, 636,
163–175.
Received: May 8, 2010
Published online: July 26, 2010
10784
www.chemeurj.org
ꢀ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2010, 16, 10778 – 10784