Polyazide chemistry: Preparation and characterization of As(N 3)5, Sb(N3)5, and [P(C 6H5)4][Sb(N3)6]

Article abstract of DOI:10.1002/anie.200461730

After all, neat As(N₃)₅ can be isolated: By analogy with AsCl₅, neat As(N₃)₅ was predicted to be a highly unstable compound, and previous attempts at its synthesis had resulted in intense explosions. The successful syntheses and characterization of neat As(N₃)₅ and Sb(N₃)₅ and the crystal structure of the [Sb(N₃)₆]^- ion (see picture) are now described.

Full text of DOI:10.1002/anie.200461730

Communications
Binary Group 15 Azides
explode violently when touched with a metal spatula or by
rapid change in temperature (e.g. freezing with liquid nitro-
gen). As(N3)5 was obtained as a yellow liquid. Its identity was
established by the observed material balance, through 14N
NMR and vibrational spectroscopy, and its conversion with
[N3]ꢀ into the known[4,5] [As(N3)6]ꢀ ion. The observed low-
temperature Raman spectrum of As(N3)5 is shown in Figure 1.
Polyazide Chemistry: Preparation and
Characterization of As(N3)5, Sb(N3)5, and
[P(C6H5)4][Sb(N3)6]**
Ralf Haiges,* Jerry A. Boatz, Ashwani Vij, Vandana Vij,
Michael Gerken, Stefan Schneider, Thorsten Schroer,
Muhammed Yousufuddin, and Karl O. Christe*
The binary arsenic and antimony azide species As(N3)3,[1–3]
[As(N3)4]+,[4] [As(N3)4]ꢀ,[4] [As(N3)6]ꢀ,[4,5] Sb(N3)3,[3,6]
[Sb(N3)4]+,[4] [Sb(N3)4]ꢀ,[4] and [Sb(N3)6]ꢀ [4] have been
reported, and the crystal structures of As(N3)3,[3] Sb(N3)3,[3]
and [As(N3)6]ꢀ[4,5] determined.[7] In addition, the Lewis base
stabilized species M(N3)5·LB (M = As, Sb; LB = pyridine,
quinoline, NH3, N2H4, NH2CN) are known.[8] However,
previous attempts[4] to obtain the neat pentaazides of arsenic
and antimony were not successful. Even at low temperatures,
attempted syntheses resulted in explosions that were de-
scribed as “so intense that only pulverized glass remained”.[4]
Furthermore, As(N3)5 was predicted[4] to be a “highly
unstable compound”, based on its analogy to AsCl5.[9]
Herein, we communicate the synthesis and characterization
of neat As(N3)5 and Sb(N3)5, and their conversion into the
[As(N3)6]ꢀ and [Sb(N3)6]ꢀ ions, respectively. We also report
the crystal structure of [P(C6H5)4][Sb(N3)6].
Figure 1. Low-temperature Raman spectrum of As(N3)5.
In contrast to a previous prediction,[4] neat arsenic pentaazide
was found to be kinetically stable at ambient temperature, but
highly explosive. The presence of covalent azido
ligands[1–8,10–14] was confirmed by the observed 14N NMR
shifts of d = ꢀ149 ppm (Nb, Dn1/2 = 42 Hz), ꢀ160 ppm (Ng,
Dn1/2 = 96 Hz), and ꢀ282 ppm (Na, extremely broad) in
DMSO solution at 258C.
Sb(N3)5 was obtained as a pale yellow solid. It is even
more sensitive than As(N3)5 and must be handled at reduced
temperature. Warming the compound to ambient temper-
ature results in violent decomposition and can cause serious
damage. The identity of antimony pentaazide was established
by the observed material balance, its Raman spectrum
(Figure 2), and its reaction with [N3]ꢀ to give the [Sb(N3)6]ꢀ
ion. The calculated and observed vibrational frequencies and
intensities for As(N3)5 and Sb(N3)5 are listed in Table 1. The
agreement between the observed frequencies and those
calculated for pentacoordinate trigonal-bipyramidal struc-
The reactions of AsF5 or SbF5 in SO2 with excess
(CH3)3SiN3 result in facile and complete fluoride–azide
exchange and yield clear yellow solutions of As(N3)5 or
Sb(N3)5, respectively, [Eq. (1); M = As, Sb].
SO2
ƒƒ!
MF5 þ 5 ðCH3Þ3SiN3
MðN Þ þ 5 ðCH Þ SiF
ð1Þ
3
5
3 3
Removal of the volatile compounds (SO2, (CH3)3SiF, and
excess (CH3)3SiN3) results in the isolation of the neat
pentaazides.
As expected for highly endothermic, covalent polyazides,
As(N3)5 and Sb(N3)5 are highly shock sensitive and can
[*] Dr. R. Haiges, Dr. M. Gerken, Dr. S. Schneider, Dr. T. Schroer,
M. Yousufuddin, Prof. Dr. K. O. Christe
Loker Research Institute and Department of Chemistry
University of Southern California
Los Angeles, CA 90089-1661 (USA)
Fax: (+1)213-740-6679
E-mail: haiges@usc.edu
kchriste@usc.edu
Dr. J. A. Boatz, Dr. A. Vij, V. Vij
Space and Missile Propulsion Division
Air Force Research Laboratory (AFRL/PRSP)
10 East Saturn Boulevard Bldg 8451, Edwards Air Force Base, CA
93524 (USA)
[**] This work was funded by the Defense Advanced Research Projects
Agency, with additionalsupport from the Air Force Office of
Scientific Research and the NationalScience Foundation. R.H.
thanks the Deutsche Forschungsgemeinschaft for a postdoctoral
fellowship. We thank Prof. G. A. Olah, and Drs. A. Morrish, D.
Woodbury, and M. Berman, for their steady support, and Prof. R.
Bau and Dr. R. Wagner for their help and stimulating discussions.
Figure 2. Low-temperature Raman spectrum of Sb(N3)5. The band
marked by an asterisk is due to the Teflon-FEP sample tube.
6676
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
DOI: 10.1002/anie.200461730
Angew. Chem. Int. Ed. 2004, 43, 6676 –6680

Angewandte
Chemie
Table 1: Comparison of observed and calculated[a] vibrationalfrequencies [cm ꢀ1] and intensities[b] for As(N3)5 and Sb(N3)5.
Band
Description
As(N3)5
Sb(N3)5
calcd (IR) [Raman]
obsd Raman
calcd (IR) [Raman]
obsd Raman
2146 [10.0]
n1
nasN3
nasN3
nasN3
nasN3
nasN3
nsN3
nsN3
nsN3
nsN3
nsN3
dN3
dN3
dN3
dN3
dN3
dN3
dN3
dN3
dN3
dN3
nasMN
nasMN
nasMN
nsMN
nasMN
dMN
dMN
dMN
dMN
dMN
t
2162 [0.4]
2135 [4.7]
2114 [2.6]
2249 (366) [21]
2234 (775) [21]
2210 (182) [35]
2199 (417) [31]
2191 (924) [24]
1310 (48) [36]
1305 (190) [8.8]
1284 (45) [21]
1283 (344) [3.1]
1276 (172) [9.3]
727 (91) [2.6]
718 (16) [2.9]
712 (29) [1.0]
703 (59) [15]
686 (9) [18]
559 (9) [0.7]
552 (3) [0.9]
548 (5) [1.2]
547 (4) [0.2]
547 (12) [0.9]
514 (114) [3.1]
500 (100) [4.6]
488 (113) [4.6]
463 (10) [49]
416 (6) [10]
333 (73) [0.7]
322 (47) [0.9]
314 (43) [2.6]
298 (6) [5.2]
291 (5) [9.4]
183 (1) [4.2]
173 (3) [1.5]
167 (1) [4.4]
148 (0.3) [0.7]
112 (2) [3.2]
95 (0) [8.5]
2198 (208) [35]
2194 (936) [21]
2172 (282) [41]
2166 (393) [25]
2160 (941) [26]
1262 (53) [32]
1258 (151) [12]
1243 (17) [24]
1241 (290) [1.5]
1238 (134) [7.9]
661 (8) [1.5]
658 (40) [3.9]
653 (14) [1.9]
647 (28) [15]
634 (4) [28]
540 (4) [1.3]
529 (3) [0.9]
525 (2) [1.2]
524 (3) [1.3]
522 (4) [1.1]
458 (74) [5.3]
452 (74) [5.8]
446 (69) [5.3]
424 (4) [89]
n2
n3
2127 [3.8]
2107 [2.6]
2097 [2.2]
1260 [0.7]
1249 [0.5]
1239 [0.5]
1221 [0.4]
n4
n5
n6
1262 [0.3]
1250 [0.3]
n7
n8
n9
n10
n11
n12
n13
n14
n15
n16
n17
n18
n19
n20
n21
n22
n23
n24
n25
n26
n27
n28
n29
n30
n31
n32
n33
n34
n35
n36
n37
n38
n39
n40
n41
n42
699 [0.8]
682 [1.0]
667 [1.0]
646 [2.2]
630 [0.7]
666 [1.7]
532 [0.5]
434 [7.5]
421 [6.0]
437 [10.0]
397 [0.8]
404 [3.8]
382 [1.0]
400 (3) [14]
255 (62) [0.9]
250 (41) [1.6]
242 (11) [10]
234 (15) [5.2]
222 (29) [5.8]
151 (2) [5.5]
143 (4) [1.8]
136 (1) [5.6]
126 (1) [0.6]
92 (2) [3.7]
82 (1) [12]
81 (0) [12]
69 (1) [2.8]
49 (0) [4.7]
43 (0) [5.4]
34 (0) [8.8]
24 (0) [4.8]
291 [1.1]
253 [2.5]
239 [1.4]
207 [1.6]
183 [2.3]
171 [2.6]
303 [0.8]
284 [1.6]
194 [1.7]
t
t
t
t
t
t
92 (0.3) [9.5]
83 (1) [4.4]
53 (0) [4.6]
45 (0) [6.3]
43 (0) [7.7]
t
t
t
t
t
31 (0) [4.5]
[a] Our calculated MP2 minimum energy structures for As(N3)5 and Sb(N3)5 are derived from trigonalbipyramids and are very simialr to those
obtained at the B3LYP level.[4] [b] Observed Raman intensities are relative intensities; calculated IR intensities [kmmolꢀ1] and calculated Raman
[Š4 amuꢀ1].
tures is good. However, it must be kept in mind that
distinction between slightly different geometries based on
the skeletal modes in these types of polyazido compounds is
generally difficult, because the vibrational spectra are com-
plex and not very sensitive to minor changes in the ligand
arrangement.
The reactions of As(N3)5 and Sb(N3)5 with ionic azides,
such as [PPh4]+[N3]ꢀ, produce the corresponding
[As(N3)6]ꢀ[4,5] and [Sb(N3)6]ꢀ salts, respectively, [Eq. (2);
M = As, Sb].
colorless solids. The [PPh4][Sb(N3)6] salt can also be prepared
from the corresponding [SbCl6]ꢀ salt and (CH3)3SiN3 in
CH3CN solution. However, the previously published[4] reac-
tion conditions, that is, one single treatment at 258C for 24 h,
were found insufficient. Even after seven prolonged treat-
ments with large amounts of fresh (CH3)3SiN3 only four of the
original six chlorine ligands were replaced by azido groups, as
shown by Raman spectroscopy and single-crystal X-ray
diffraction studies. Heating to 828C in refluxing CH3CN was
required to achieve further chloride substitution.
Single crystals of [PPh4][Sb(N3)6] were obtained by
recrystallization from CH3CN solution. Because of the
presence of a large counterion which serves as an inert
spacer and suppresses detonation propagation, these salts are
SO2
MðN3Þ5 þ ½PPh4ꢁN3
½PPh ꢁ½MðN Þ ꢁ
ð2Þ
ƒƒ!
4
3 6
Both tetraphenylphosphonium salts were isolated as
Angew. Chem. Int. Ed. 2004, 43, 6676 –6680
www.angewandte.org
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
6677

Communications
much less shock sensitive than neat As(N3)5 and Sb(N3)5, and
their crystal structures. This result is in accord with our finding
that, under the previously reported conditions,[4] the chloride/
azide exchange is incomplete.
The observed Raman and IR spectra of [P(C6H5)4]
[Sb(N3)6] are shown in Figure 4, and the observed frequencies
and intensities are listed in the Experimental Section.
are thermally surprisingly stable. Thus, a crystalline sample of
[PPh4][Sb(N3)6] could be heated to its melting point at 104–
1068C without decomposition.
[PPh4][Sb(N3)6] crystallizes in the monoclinic space group
C2/c. Its X-ray structure (Figure 3)[15] revealed the presence of
Figure 3. ORTEP drawing of the anionic part of the crystalstructure of
[PPh4][Sb(N3)6]. Thermal ellipsoids are set at 50% probability. Selected
bond lengths [Š] and angles [8]: Sb-N1 2.065(2), Sb-N4 2.079(2), Sb-N7
2.085(3), N1-N2 1.220(3), N2-N3 1.120(3), N4-N5 1.222(4), N5-N6
1.127(4), N7-N8 1.222(3), N8-N9 1.128(4); N1-N2-N3 175.1(3), N4-
N5-N6 175.1(3), N7-N8-N9 174.7(4), N1-Sb-N4 92.00(9), N1-Sb-N7
88.33(11), N4-Sb-N7 88.45(11), Sb-N1-N2 116.7(2), Sb-N4-N5
116.4(2), Sb-N7-N8 116.6(2).
[PPh4]+ and [Sb(N3)6]ꢀ ions without significant cation–anion
interaction. The closest Sb···N and N···N contacts between
neighboring anions are 5.0 Š and 3.2 Š, respectively. The
structure of the [Sb(N3)6]ꢀ ion is only slightly distorted from
perfect S6 symmetry and is analogous to those of
[As(N3)6]ꢀ,[4,5] [Si(N3)6]2ꢀ[16] [Ge(N3)6]2ꢀ[17] and [Ti(N3)6]2ꢀ,[18]
and contrary to that of [Te(N3)6]2ꢀ.[19] The structure of the
[Sb(N3)6]ꢀ ion consists of an asymmetric SbN9 unit with three
azido groups covalently bonded in a trigonal pyramidal
fashion to the antimony center. The remaining three coordi-
nation sites at the metal center are occupied by three
symmetry related azido groups (symmetry operation ꢀx + 3/
Figure 4. IR (top) and Raman (bottom) spectra of [P(C6H5)4][Sb(N3)6].
The bands belonging to the [Sb(N3)6]ꢀ ion are marked with asterisks.
Assignments of the observed spectra were made by compar-
ison with those calculated at the MP2/SBK + (d) level of
theory and are given in the Experimental Section. The good
agreement between the observed and calculated spectra
confirms the results from the crystal-structure determination
that, in its [PPh4]+ salt, the [Sb(N3)6]ꢀ ion closely approx-
imates ideal S6 symmetry.
ꢀ
2,ꢀy + 3/2,ꢀz + 1). All three Sb N bond of 2.064(2), 2.079(2),
and 2.084(2) Š are significantly shorter than the 2.119(4) Š
found for Sb(N3)3.[3]
Further support for the presence of the [Sb(N3)6]ꢀ ion is
provided by the NMR spectrum. The 14N NMR spectrum in
DMSO shows resonances at d = ꢀ141 ppm (Nb, Dn1/2
=
Experimental Section
63 Hz), ꢀ185 ppm (Ng, Dn1/2 = 103 Hz), and ꢀ287 ppm (Na,
Dn1/2 = 580 Hz), that are characteristic for covalent
azides.[1–8,10–14] Our spectrum differs, particularly in the Ng
region, significantly from that previously reported[4] (Nb: d =
ꢀ141 ppm, Dn1/2 = 45 Hz; Ng: d = ꢀ154 ppm, Dn1/2 = 120 Hz,
d = ꢀ163 ppm, Dn1/2 = 45 Hz, d = ꢀ173 ppm, Dn1/2 = 110 Hz;
Na: d = ꢀ244 ppm, Dn1/2 = 580 Hz), for the [N(C2H5)4]+ salt in
the same solvent and at the same temperature. We have
observed similar shifts and multiple resonances for Ng (Nad =
ꢀ245 ppm; Ngd = ꢀ150, ꢀ160, ꢀ168, and ꢀ169 ppm) in
samples, prepared from [SbCl6]ꢀ, in which chlorine substitu-
tion was incomplete, as shown by Raman spectroscopy and
Caution! Arsenic and antimony azides are toxic, potentially hazard-
ous, and can decompose explosively under various conditions! They
should be handled only on a scale of less than 2 mmol with appropriate
safety precautions (safety shields, safety glasses, face shields, leather
gloves, protective clothing, such as leather suits, and ear plugs).[3,18,19]
Teflon containers should be used, whenever possible, to avoid hazard-
ous shrapnel formation. Rapid changes in temperature of As(N3)5 and
Sb(N3)5 (whether pure or in SO2 solution) can result in violent
explosions. The manipulation of these materials is facilitated by
handling them, whenever possible, in solution to avoid detonation
propagation, the use of large inert counterions as spacers, and anion
formation which increases the partial negative charges on the terminal
ꢀ
Ng atoms and thereby reduces the Nb Ng triple-bond character and the
6678
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
Angew. Chem. Int. Ed. 2004, 43, 6676 –6680

Angewandte
Chemie
tendency for N2 elimination. Ignoring safety precautions can lead to
serious injuries!
Basch, and Krauss (SBK) effective core potentials and the corre-
sponding valence-only basis sets were used.[26] The SBK valence basis
set for nitrogen was augmented with a d polarization function[25] and a
diffuse s + p shell,[27] whereas only a d polarization function[28] was
added to the antimony basis set. Hessians (energy second derivatives)
were calculated for the final equilibrium structures to determine if
they are minima (positive definite hessian) or transition states (one
negative eigenvalue). All calculations were performed using the
electronic structure code GAMESS.[29]
All reactions were carried out in Teflon-FEP ampules (FEP =
perfluoro ethylene propylene polymer) that were closed by stainless
steel valves. Volatile materials were handled in a Pyrex glass vacuum
line. All Teflon reaction vessels were passivated with ClF3 prior to use.
Nonvolatile materials were handled in the dry argon atmosphere of a
glove box.
Raman spectra were recorded at ꢀ808C in the range 4000–
80 cmꢀ1 on a Bruker Equinox 55 FT-RA spectrophotometer using a
Nd-YAG laser at 1064 nm with power levels of 200 mW or less and a
1808 geometry. Pyrex melting-point tubes that were baked out at
3008C for 48 h at 10 mTorr vacuum or Teflon-FEP tubes with stainless
steel valves that were passivated with ClF3 were used as sample
containers. IR spectra were recorded in the range 4000–400 cmꢀ1 on a
Midac, M Series, FT-IR spectrometer using KBr or AgCl pellets. The
pellets were prepared inside the glove-box using an Econo press
(Barnes Engineering Co.).
Unscaled calculated frequencies (cmꢀ1) and (infrared, kmmolꢀ1
and [Raman, Š4 amuꢀ1 intensities for the [Sb(N3)6]ꢀ ion (C2h
)
]
symmetry): Ag: 2219 (0) [82], 2200 (0) [48], 1273 (0) [77], 1267 (0)
[41], 659 (0) [6.0], 645 (0) [23], 596 (0) [18], 409 (0) [121], 385 (0)
[8.8], 236 (0) [5.2], 215 (0) [12], 128 (0) [9.3], 68 (0) [20], 30 (0) [17];
Bg: 2202 (0) [33], 1267 (0) [42], 652 (0) [0.9], 590 (0) [0.1], 549 (0)
[0.4], 372 (0) [5.4], 225 (0) [4.6,] 128 (0) [8.4], 41 (0) [12], 24 (0) [9.9];
Au: 2216 (1299) [0], 1268 (171) [0], 659 (5.8) [0], 590 (2.2) [0], 547
(5.8) [0], 424 (135) [0], 257 (122) [0], 195 (9.2) [0], 152 (1.0) [0], 68
(0.3) [0], 36 (1.1) [0], 19 (0.2) [0]; Bu: 2204 (1493) [0], 2193 (914) [0],
1271 (147) [0], 1268 (148) [0], 663 (25) [0], 650 (34) [0], 596 (7.0) [0],
429 (97) [0], 416 (112) [0], 247 (88) [0], 244 (52) [0], 166 (3.5) [0], 79
(4.1) [0], 71 (2.5) [0], 24 (0.5) [0].
14N NMR spectra were recorded unlocked at 36.13 MHz on a
Bruker AMX 500 spectrometer using solutions of the compounds in
DMSO in sealed standard glass tubes. Neat CH3NO2 (d = 0.00 ppm)
was used as the external reference.
The starting materials AsF5 (Ozark Mahoning) and [P(C6H5)4]I
(Aldrich) were used without further purification. (CH3)3SiN3
(Aldrich) was purified by fractional condensation and SbF5 (Ozark
Mahoning) by distillation prior to use. Solvents were dried by
standard methods and freshly distilled before being used.
[P(C6H5)4]N3 was prepared from [P(C6H5)4]I and AgN3.
Received: August 20, 2004
Keywords: antimony · arsenic · azides · theoreticalchemistry
.
As(N3)5: (CH3)3SiN3 (3.91 mmol) was condensed atꢀ1968C onto
a frozen solution of AsF5 (0.570 mmol) in SO2 (1 mL). The reaction
mixture was kept at ꢀ258C for 30 min and then slowly warmed to
ambient temperature over a period of 4 h resulting in a yellow
solution. Removal of all volatile material at ambient temperature in a
dynamic vacuum resulted in the isolation of a colorless liquid (0.170 g,
weight calculated for 0.570 mmol of As(N3)5 = 0.162 g). The obtained
liquid was characterized by Raman and NMR spectroscopy.
Sb(N3)5: (CH3)3SiN3 (4.84 mmol) was condensed atꢀ1968C onto
a frozen solution of SbF5 (0.609 mmol) in SO2 (14 mmol). The
reaction mixture was warmed to ꢀ258C and kept between ꢀ258C and
ꢀ158C for 10 h resulting in a bright yellow solution. Removal of all
volatile material at ꢀ158C in a dynamic vacuum resulted in the
isolation of an intense yellow solid (0.216 g, weight calculated for
0.609 mmol of Sb(N3)5 = 0.202 g).
[1] T. M. Klapötke, P. Geissler, J. Chem. Soc. Dalton Trans. 1995,
3365.
[2] P. Geissler, T. M. Klapötke, H.-J. Kroth, Spectrochim. Acta Part
A 1995, 51, 1075.
[3] R. Haiges, A. Vij, J. A. Boatz, S. Schneider, T. Schroer, M.
Gerken, K. O. Christe, Chem. Eur. J. 2004, 10, 508.
[4] K. Karaghiosoff, T. M. Klapötke, B. Krumm, H. Nöth, T. Schütt,
M. Suter, Inorg. Chem. 2002, 41, 170.
[5] T. M. Klapötke, H. Nöth, T. Schütt, M. Warchhold, Angew.
Chem. 2000, 112, 2197; Angew. Chem. Int. Ed. 2000, 39, 2108.
[6] T. M. Klapötke, A. Schulz, J. McNamara, J. Chem. Soc. Dalton
Trans. 1996, 2985.
[7] For recent reviews, see: a) W. Fraenk, T. M. Klapötke in
Inorganic Chemistry Highlights (Eds.: G. Meyer, D. Naumann,
L. Wesemann), Wiley-VCH, Weinheim, 2002; b) A. Kornath,
Angew. Chem. 2001, 113, 3231; Angew. Chem. Int. Ed. 2001, 40,
3135; c) T. M. Klapötke, Chem. Ber. 1997, 130, 443.
[8] T. M. Klapötke, T. Schütt, J. Fluorine Chem. 2001, 109, 151.
[9] a) K. Seppelt, Z. Anorg. Allg. Chem. 1977, 434, 5; b) K. Seppelt,
Angew. Chem. 1976, 88, 410; Angew. Chem. Int. Ed. Engl. 1976,
15, 377.
[10] T. M. Klapötke, B. Krumm, P. Mayer, O. P. Ruscitti, Inorg.
Chem. 2000, 39, 5426.
[11] T. M. Klapötke, B. Krumm, P. Mayer, H. Piotrowski, O. P.
Ruscitti, A. Schiller, Inorg. Chem. 2002, 41, 1184.
[12] T. M. Klapötke, B. Krumm, P. Mayer, H. Piotrowski, I. Schwab,
M. Vogt, Eur. J. Inorg. Chem. 2002, 2701.
[13] J. Mason in Multinuclear NMR (Ed.: J. Mason), Plenum, New
York, 1987.
[PPh4][M(N3)6] (M = As, Sb): Neat PPh4N3 (0.43 mmol) was
added to a cooled solution of M(N3)5 (0.43 mmol) in SO2 (15 mmol) at
ꢀ648C. The reaction mixture was kept at ꢀ258C and occasionally
agitated. After 2 h, all volatiles were removed at ambient temper-
ature in a dynamic vacuum, leaving behind solid [PPh4][M(N3)6].
([PPh4][As(N3)6]: 0.285 g, weight calculated for 0.43 mmol = 0.288 g;
[PPh4][Sb(N3)6]: 0.313 g, weight calculated for 0.43 mmol = 0.307 g).
Colorless single crystals of [PPh4][Sb(N3)6] were grown from a
solution in CH3CN by slow evaporation of the solvent in a dynamic
vacuum. Raman spectrum of the [As(N3)6]ꢀ ion (50 mW, 208C): n˜ =
2125(4.9)/2085(3.0) (nasN3), 1331(0.6)/1269(1.0)/1251(0.6) (nsN3),
666(1.5)/631(0.5) (dN3), 418(10.0) (nsAsN), 379(1.1) (nasAsN),
278(1.4) (dAsN), 165 (5.0) cmꢀ1
.
[Sb(N3)6]ꢀ: IR (KBr): n˜ =
3329(mw)/2583(w)/2522(w) (combination bands), 2086(vs)/2016(s)
(nasN3), 1337(m)/1318(m)/1264(s) (nsN3), 663(m)/580(w) (dN3),
424(s) cmꢀ1 (nSbN). Raman (50 mW, 208C): n˜ = 2116(4.1)/2087
(1.4)/2075(1.1)/2018(0.3) (nasN3), 1319(0.5)/1275(0.5) (nsN3), 653(1.4)
(dN3), 412(10.0) (nsSbN), 386(1.0) (nasSbN), 229(2.5) (dSbN), 147
[14] S. Berger, S. Braun, H. O. Kalinowski, NMR Spectroscopy of the
Non-Metallic Elements, Wiley, Chichester, 1997.
[15] Crystal data for C24H20N18PSb: Mr = 713.30, monoclinic, space
group C2/c, a = 22.055(3), b = 7.2656(7), c = 18.994(2) Š, a = 90,
b = 97.989(3), g = 908, V= 3014.1(5) Š3, F(000) = 1424, 1calcd(Z =
4) = 1.572 gcmꢀ3, m = 1.018 mmꢀ1, approximate crystal dimen-
sions 0.40 ” 0.18 ” 0.02 mm3, q range = 2.17 to 27.538, MoKa (l =
0.71073 Š), T= 143(2) K, 7213 measured data (Bruker 3-circle,
SMART APEX CCD with x-axis fixed at 54.748, using the
SMART V 5.625 program, Bruker AXS: Madison, WI, 2001), of
(3.0) cmꢀ1
.
Optimizations of all structures were performed using second-
order perturbation theory.[20,21] For the arsenic azides, the Binning and
Curtis double-zeta valence basis set,[22] augmented with a d polariza-
tion function[23] was used for the arsenic and the 6-31G(d) basis
set[24, 25] for the nitrogen atoms. For the antimony azides, the Stevens,
Angew. Chem. Int. Ed. 2004, 43, 6676 –6680
www.angewandte.org
ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
6679

Communications
which 3130 (Rint = 0.0545) unique. Lorentz and polarization
correction (SAINT V 6.22 program, Bruker AXS: Madison, WI,
2001), absorption correction (SADABS program, Bruker AXS:
Madison, WI, 2001). Structure solution by direct methods
(SHELXTL 5.10, Bruker AXS: Madison, WI, 2000), full-
matrix least-squares refinement on F2, data to parameters
ratio: 15.6:1, final R indices [I > 2s(I)]: R1 = 0.0356, wR2 =
0.0669, R1 = 0.0455, wR2 = 0.0684 (all data), GOF on F2 =
0.900. CCDC-240155 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from
the Cambridge Crystallographic Data Centre, 12, Union Road,
Cambridge CB21EZ, UK; fax: (+ 44)1223-336-033; or deposit@
ccdc.cam.ac.uk).
[16] A. C. Filippou, P. Portius, G. Schnakenburg, J. Am. Chem. Soc.
2002, 124, 12396.
[17] A. C. Filippou, P. Portius, D. U. Neumann, K.-D. Wehrstedt,
Angew. Chem. 2000, 112, 4524; Angew. Chem. Int. Ed. 2000, 39,
4333.
[18] R. Haiges, J. A. Boatz, S. Schneider, T. Schroer, M. Yousufuddin,
K. O. Christe, Angew. Chem. 2004, 116, 3210; Angew. Chem. Int.
Ed. 2004, 43, 3148.
[19] R. Haiges, J. A. Boatz, A. Vij, M. Gerken, S. Schneider, T.
Schroer, K. O. Christe, Angew. Chem. 2003, 115, 5027; Angew.
Chem. Int. Ed. 2003, 42, 5847.
[20] a) C. Moeller, M. S. Plesset, Phys. Rev. 1934, 46, 618; b) J. A.
Pople, J. S. Binkley, R. Seeger, Int. J. Quantum Chem. 1976, S10,
1; c) M. J. Frisch, M. Head-Gordon, J. A. Pople, Chem. Phys.
Lett. 1990, 166, 275.
[21] R. J. Bartlett, D. M. Silver, Int. J. Quantum Chem. Symp. 1975, 9,
1927.
[22] R. C. Binning, Jr., L. A. Curtiss, J. Comput. Chem. 1990, 11,
1206.
[23] A d function polarization exponent of 0.293 was used.
[24] W. J. Hehre, R. Ditchfield, J. A. Pople, J. Chem. Phys. 1972, 56,
2257.
[25] The exponent of the d polarization function on N is 0.8; see P. C.
Hariharan, J. A. Pople, Theor. Chim. Acta 1973, 28, 213.
[26] W. J. Stevens, H. Basch, M. Krauss, J. Chem. Phys. 1984, 81, 6026.
[27] The exponent of the diffuse s + p shell is 0.0639; see T. Clark, J.
Chandrasekhar, G. W. Spitznagel, P. v. R. Schleyer, J. Comput.
Chem. 1983, 4, 294.
[28] The exponent of the d polarization function on Sb is 0.211; see S.
Huzinaga, J. Andzelm, M. Klobukowski, E. Radzio-Andzelm, Y.
Sakai, H. Tatewaki, Gaussian Basis Sets for Molecular Calcu-
lations, Elsevier, Amsterdam, 1984.
[29] M. W. Schmidt, K. K. Baldridge, J. A. Boatz, S. T. Elbert, M. S.
Gordon, J. H. Jensen, S. Koseki, N. Matsunaga, K. A. Nguyen, S.
Su, T. L. Windus, J. Comput. Chem. 1993, 14, 1347.
6680 ꢀ 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
Angew. Chem. Int. Ed. 2004, 43, 6676 –6680