Polyazide chemistry: The first binary group 6 azides, Mo(N 3)6, W(N3)6, [Mo(N3) 7]-, and [W(N3)7]-, and the [NW(N3)4]-

Article abstract of DOI:10.1002/anie.200462740

(Figure Presented) Bang on target: The highly explosive Group 6 azides Mo(N₃)₆ and W(N₃)₆ are prepared by the reaction of Me₃SiN₃ with MoF₆ and WF ₆, respectively. The

Full text of DOI:10.1002/anie.200462740

Communications
Azides
Polyazide Chemistry: The First Binary Group 6
Azides, Mo(N3)6, W(N3)6, [Mo(N3)7]ꢀ, and
[W(N3)7]ꢀ, and the [NW(N3)4]ꢀ and
[NMo(N3)4]ꢀ Ions**
Ralf Haiges,* Jerry A. Boatz, Robert Bau,
Stefan Schneider, Thorsten Schroer,
Muhammed Yousufuddin, and Karl O. Christe*
Dedicated to Professor Kurt Dehnicke
Whereas numerous binary transition-metal azido complexes
have been reported,[1] no binary Group 6 azides are known.
Only a limited number of partially azide-substituted molyb-
denum and tungsten compounds have been reported.[2–30]
Furthermore, no heptaazido compounds have been described.
Herein, we report the synthesis and characterization of
the first binary Group 6 azides, Mo(N3)6, W(N3)6, [Mo(N3)7]ꢀ,
and [W(N3)7]ꢀ. The last two ions represent the first examples
of heptaazides. We also report the crystal structure of W(N3)6
and the controlled nitrogen loss from the heptaazido anions to
[*] Dr. R. Haiges, Prof. Dr. R. Bau, 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
Space and Missile Propulsion Division
Air Force Research Laboratory (AFRL/PRSP)
10 East Saturn Boulevard
Edwards Air Force Base, CA 93524 (USA)
[**] This work was funded by the Air Force Office of Scientific Research
and the National Science Foundation. We thank Prof. Dr. G. A. Olah
and Dr. M. Berman, for their steady support, and Dr. R. Wagner for
his help and stimulating discussions. Dedicated to Professor Kurt
Dehnicke for his lifelong contributions to azide chemistry.
Supporting information for this article is available on the WWW
under http://www.angewandte.org or from the author.
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DOI: 10.1002/anie.200462740
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give nitrido-teraazido anions. The [NMo(N3)4]ꢀ ion is already
known but had been obtained by a different method.[25]
The reactions of MoF6 or WF6 with excess (CH3)3SiN3 in
acetonitrile solution at ꢀ25 to ꢀ308C result in complete
fluoride–azide exchange and yield clear, dark-red solutions of
Mo(N3)6 or W(N3)6, respectively [Eq. (1), (M = Mo, W)].
2.95 ꢀ, respectively. The structure of the W(N3)6 unit is only
slightly distorted from perfect S6 symmetry and closely
resembles those of [As(N3)6]ꢀ,[33] [Sb(N3)6]ꢀ,[34] [Si(N3)6]2ꢀ,[35]
[Ge(N3)6]2ꢀ,[36] and [Ti(N3)6]2ꢀ,[1a] but contrasts that of [Te-
(N3)6]2ꢀ[37] which possesses a sterically active free valence
electron pair on its central atom. W(N3)6 consists of an
asymmetric W(N3)2 unit with two azido groups covalently
bonded in a bent fashion to the tungsten. The remaining four
coordination positions at the metal center are occupied by
four symmetry related azido groups (symmetry operations
MF6 þ 6 ðCH3Þ3SiN3 ! MðN3Þ6 þ 6 ðCH3Þ3SiF
ð1Þ
Removal of the volatile compounds (CH3CN, (CH3)3SiF,
and excess (CH3)3SiN3) at ꢀ258C results in the isolation of the
neat hexaazides in quantitative yield.
ꢀ
ꢀy + 1,xꢀy + 1,z and ꢀx + y,ꢀx + 1,z). The observed W N
bonds of 1.949(2) ꢀ and 2.006(2) ꢀ are significantly longer
than that of 1.85(2) ꢀ found for [WF5N3].[13a]
As expected for covalently bonded, neutral, high-oxida-
tion-state polyazides,[31] Mo(N3)6 and W(N3)6 are extremely
shock sensitive and can explode violently even at low-
temperature, when either touched with a metal spatula or
by rapid change in temperature, such as freezing with liquid
nitrogen. W(N3)6 was isolated as a dark red solid, and ruby-
red single crystals were obtained by recrystallization from its
CH3CN solution. Neat W(N3)6 must be handled with extreme
care and at reduced temperature. Warming the compound to
ambient temperature results in violent decomposition and can
cause serious damage. For example, when a Teflon ampule,
containing a small amount of single crystals, was allowed to
warm to room temperature inside a stainless steel can, an
explosion resulted which not only destroyed the ampule but
also blew a hole of 5-cm diameter through the wall of the steel
can. Mo(N3)6 was obtained as a dark red solid. It is even more
sensitive than W(N3)6 and explodes violently upon the
slightest provocation, such as a rapid change in the pressure
of the inert gas in the vacuum line.
The observed low-temperature Raman spectrum of W-
(N3)6 (Figure 2) was assigned (see Supporting Information) by
Figure 2. Low-temperature Raman spectrum of solid W(N3)6.
Tungsten hexaazide was characterized by its crystal
comparison with the spectra calculated at the MP2[38] and
B3LYP[39] levels of theory using a SBKJ + (d) basis set.[40]
Although the calculated frequencies and intensities vary
somewhat with the method used, their overall agreement with
the experiment is very satisfactory. The internal modes of the
azido ligands are separated into groups of six, owing to in-
phase (one mode) and out-of-phase (five modes) coupling,
with the in-phase mode resulting in the highest polarizability
change and Raman intensity. For example, the antisymmetric
N3 stretching modes exhibit two very intense bands at 2139
and 2130 cmꢀ1, which represent the in-phase coupled mode,
split by either Fermi resonance or site symmetry effects, and a
cluster of five less intense bands between 2107 and 2064 cmꢀ1
which represents the five out-of-phase coupled modes. The
{WN6} skeleton is approximately octahedral with the devia-
tions from right angles being 78 or less. Therefore, the skeletal
vibrations can be derived from Oh symmetry, allowing for a
splitting into the degenerate components (two for the
E modes and three for the F modes). It should be noted
that there is no clear preference for using either the MP2 or
the B3LYP set for fitting the entire spectrum. There is
considerable variation in the relative intensities and sequen-
ces of the modes within a given group, and both sets should be
used for a comparison with the observed spectrum.
structure[32] and vibrational spectroscopy. It crystallizes in
¯
the trigonal space group P3 and contains isolated W(N3)6
molecules (Figure 1), as shown by the closest W···N and N···N
contacts between neighboring molecules of 4.02 ꢀ and
Figure 1. ORTEP diagram of W(N3)6. Thermal ellipsoids are set at 50%
probability. The tungsten atom is situated on a crystallographic site of
S6 symmetry. Selected bond lengths [ꢀ] and angles [8]: W1-N1 1.949
(2), W1-N4 2.006 (2), N1-N2 1.224(2), N2-N3 1.123(2), N4-N5
1.216(2), N5-N6 1.129(2); N1-N2-N3 176.7(2), N4-N5-N6 176.7(2),
N1-W1-N1’ 92.42(6), N1-W1-N4 172.84(5), N1-W1-N4’ 94.68(5), N1-
W1-N4’’ 86.38(6), N4-W1-N4’ 86.69(6), W1-N1-N2 138.31(11), W1-N4-
N5 134.34(12).
Because of its extreme sensitivity, the identity of molyb-
denum hexaazide could only be established by its low-
temperature Raman spectrum in CH3CN solution (Figure 3
and Supporting Information). The agreement between
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Figure 4. Low-temperature Raman spectrum of [PPh4][Mo(N3)7]. The
Figure 3. Low-temperature Raman spectrum of Mo(N3)6 dissolved in
bands marked by an asterisk ( ) are due to the Teflon-FEP sample
*
CH CN. The band marked by an asterisk ( ) is due to the Teflon-FEP
*
3
tube. Bands marked by are from the [Mo(N3)7]ꢀ ion. The three
^
^
sample tube. Bands marked by are from CH3CN.
*
bands marked by arise from excess Me3SiN3.
observed and calculated spectra is again satisfactory. All
attempts failed to obtain single crystals of diffraction quality.
Additional proof for the presence of Mo(N3)6 was obtained by
its conversion into [Mo(N3)7]ꢀ and the known[25] [NMo(N3)4]ꢀ
ion.
The reactions of M(N3)6 (M = Mo or W) with ionic azides,
such as [NMe4]+[N3]ꢀ or [PPh4]+[N3]ꢀ, produce the corre-
sponding [M(N3)7]ꢀ salts [Eq. (2), (A = PPh4, NMe4)].
MðN3Þ6 þ Aþ½N3ꢁꢀ ! Aþ½MðN3Þ7ꢁꢀ
ð2Þ
Salts of both heptaazido anions were isolated at low
temperature as extremely shock-sensitive red solids that
explode violently when warmed towards room temperature.
Not surprisingly, they are less stable and more difficult to
handle than hexaazido salts, thus preventing us from obtain-
ing their crystal structures. These salts were characterized by
low-temperature Raman spectroscopy and represent the first
known examples of covalent heptaazides. The spectra of
[PPh4][Mo(N3)7] and [PPh4][W(N3)7] are shown in Figure 4
and 5, respectively (the observed and calculated frequencies
and intensities are listed in the Supporting Information).
Three different ligand arrangements are possible for hepta-
coordinated transition-metal complexes which differ only
little in energy.[41] They are derived from a pentagonal
bipyramid (1/5/1 arrangement), a monocapped trigonal
prism (1/4/2 arrangement), and a monocapped octahedron
(1/3/3 arrangement). Therefore, we have explored the possi-
bility of these three arrangements for [W(N3)7]ꢀ at the
B3LYP(3)/SBKJ + (d) level of theory. Two stable minimum
energy structures, a 1/5/1 and a 1/4/2 structure (Figure 6 and
Supporting Information), were located, the 1/5/1 structure
being favored by 3.3 kcalmolꢀ1. When monocapped octahe-
dral structures were used as starting points, the calculations
always converged to the pentagonal bipyramidal structure.
This result was somewhat unexpected because [WF7]ꢀ and
[MoF7]ꢀ exhibit monocapped octahedral structures in their
cesium salts.[41h] In view of the small energy difference, the
similarity of their calculated vibrational spectra, and the
sensitivity of the calculated spectra to the level of theory used
(Supporting Information), it was not possible to distinguish
Figure 5. Low-temperature Raman spectrum of [PPh4][W(N3)7]. The
band marked by an asterisk ( ) is due to the Teflon-FEP sample tube.
*
ꢀ
^
Bands marked by are from the [W(N3)7] ion.
Figure 6. B3LYP/SBKJ+(d) optimized geometries of [W(N3)7]ꢀ.
A) Pentagonal bipyramid (1/5/1), B) monocapped trigonal prism (1/4/
2).
between the 1/5/1 and 1/4/2 structures based on the observed
Raman spectra. Additional evidence for the formation of
heptazido anions is derived from the observed frequencies.
Compared to the neutral hexaazides, the addition of a
negatively charged [N3]ꢀ ion increases the ionicity of the
metal-azide bonds and the ionic character of the azide ligands.
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plugs) is mandatory.[1a] Ignoring safety precautions can lead to
serious injuries!
This effect should cause decreases in the antisymmetric N3
ligand and {MN6} skeletal stretching frequencies and
increases in the symmetric N3 ligand frequencies, and is
clearly observed in our spectra.
Solutions of either heptaazido anion in SO2 or CH3CN
decompose on warming to room temperature with nitrogen
evolution and formation of the tetraazido nitrido molyb-
date(vi)[25] and tetraazido nitrido tungstate(vi) anion, respec-
tively [Eq. (3) (M = Mo, W)].
Materials and Apparatus: 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 or stainless steel/Teflon-FEP vacuum line.[43]
All reaction vessels and the stainless steel/Teflon-FEP vacuum line
were passivated with ClF3 prior to use. Nonvolatile materials were
handled in the dry argon atmosphere of a glove box.
Raman spectra were recorded 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 less(!!) than 50 mW. Teflon-FEP tubes
with stainless steel valves that were passivated with ClF3 were used as
sample containers.
The starting materials WF6, MoF6 (both Ozark Mahoning) and
[PPh4]I (Aldrich) were used without further purification. (CH3)3SiN3
(Aldrich) was purified by fractional condensation prior to use.
Solvents were dried by standard methods and freshly distilled prior to
use. [PPh4]F and [PPh4]N3 were prepared from [PPh4]I and AgF and
AgN3, respectively. [NMe4][WF7] and [PPh4][WF7] were obtained
from WF6 with [NMe4]F and [PPh4]F, respectively.[44] [NMe4]F[45] and
[NMe4]N3,[46] were prepared by literature methods.
Preparation of W(N3)6: On the stainless steel vacuum line, WF6
(0.463 mmol) was condensed at ꢀ1968C into a Teflon-FEP ampule.
The ampule was then attached to a glass vacuum line and after
evacuation, CH3CN (50 mmol) was condensed in at ꢀ1968C. The
mixture was allowed to warm to ambient temperature forming a
colorless solution. After re-cooling to ꢀ1968C, (CH3)3SiN3 (4.43
mmol) was condensed onto the frozen solution, and the mixture was
warmed to ꢀ258C. Within minutes, the mixture turned orange-red
and the color intensified while the reaction proceeded. After 1 h, the
reaction mixture was dark red. All volatile material was pumped off
at ꢀ258C, leaving behind a dark red solid (yield: 0.215 g, expected for
0.463 mmol of W(N3)6, 0.202 g). Ruby-red single crystals were grown
from a solution in CH3CN by slow evaporation of the solvent
in vacuo.
>ꢀ20 oC
Aþ½MðN3Þ7ꢁꢀ
Aþ½NMðN Þ ꢁꢀ þ 4 N2
ð3Þ
ƒƒƒƒ!
3
4
The [NW(N3)4]ꢀ salts can also be prepared in a single step
from the corresponding [WF7]ꢀ salt and (CH3)3SiN3 in
CH3CN solution [Eq. (4) (A = PPh4, NMe4)].
Aþ½WF7ꢁꢀ þ 7 ðCH3Þ3SiN3 ! Aþ½NWðN3Þ4ꢁꢀ þ 4 N2 þ 7 ðCH3Þ3SiF
ð4Þ
The identity of [NW(N3)4]ꢀ and [NMo(N3)4]ꢀ was estab-
lished by vibrational spectroscopy and for [PPh4][NMo(N3)4]
also by its crystal structure (see Supporting Information).[42]
The structure of the [NMo(N3)4]ꢀ ion and its vibrational
spectra were in excellent agreement with those reported by
Dehnicke and co-workers for [AsPh4]+[NMo(N3)4]ꢀ, which
was prepared from the [NMoCl4]ꢀ salt and AgN3 in a CH2Cl2
suspension,[25] and, therefore require no further discussion.
The observed Raman spectrum of [NMe4][NW(N3)4] is shown
in Figure 7. The observed frequencies and assignments, based
on the calculated spectra, are listed for both tetraazido nitrido
anions in the Experimental Section.
Preparation of Mo(N3)6: The reaction was carried out as
described above for W(N3)6 using MoF6 (0.133 mmol), CH3CN
(30 mmol), and (CH3)3SiN3 (1.07 mmol). After keeping the mixture
for 1 h at ꢀ308C, a Raman spectrum of the reaction mixture was
recorded. The removal of all material volatile at ꢀ308C resulted in
the formation of a dark red, extremely explosive solid.
Preparation of [M(N3)7]ꢀ salts (M = Mo, W): Cold solutions of
M(N3)6 (0.20 mmol) in SO2 (60 mmol) were added to mixtures of
PPh4N3 (0.20 mmol) and SO2 (25 mmol) at ꢀ648C. The mixtures were
kept at this temperature for 30 min and occasionally agitated. All
volatiles were removed at ꢀ648C in a dynamic vacuum, leaving
behind dark red solids; weight expected for 0.20 mmol of [PPh4]-
[Mo(N3)7]: 0.146 g; found 0.158 g; weight expected for 0.20 mmol of
[PPh4][W(N3)7]: 0.163 g; found: 0.171 g.
Preparation of [NM(N3)4]ꢀ salts (M = Mo, W): Cold solutions of
the [M(N3)7]ꢀ salts (0.25 mmol) in SO2 (100 mmol) were warmed
from ꢀ648C to ꢀ258C. After about 30 min at ꢀ258C, the temperature
was raised over a period of 2 h to 258C. All volatiles were slowly
removed in a dynamic vacuum, leaving behind dark red solids.
[P(C6H5)4][NMo(N3)4]: weight found: 0.145 g; weight expected
for 0.25 mmol: 0.154 g; Raman of the [NMo(N3)4]ꢀ ion (50 mW,
ꢀ808C): n˜ = 2109(10.0), 2098(2.2), 2070(1.5), 2064(1.9), 2055(1.8),
2047(1.1), 2040(1.1), 2025(0.5) (nasN3); 1331(0.7), 1319(0.7), 1285(0.5),
Figure 7. Low-temperature Raman spectrum of [NMe4][NW(N3)4]. The
bands marked by an asterisk ( ) are due to the Teflon-FEP sample
*
tube. Bands marked by are from the [NMe4]+ ion.
^
Experimental Section
Caution! Covalent azides are potentially hazardous and can decom-
pose explosively under various conditions! The polyazides of this work
are extremely shock-sensitive and can explode violently upon the
slightest provocation. They should be handled only on a scale of less
than 1 mmol and can cause, even on a 1-mmol scale, significant
damage. During the handling of W(N3)6 and Mo(N3)6, rapid changes in
temperature or pressure can result in violent explosions. The use of
appropriate safety precautions (safety shields, face shields, leather
gloves, protective clothing, such as heavy leather welding suits and ear
ꢂ
1259(0.3) (nsN3); 1034(2.2) (nMo N); 657(0.6), 639(0.6), 626(0.5),
596(0.4), 589(0.4), 568(0.3) (dN3); 443(4.1), 429(4.1), 405(0.8),
384(0.9), 357(1.1) (nMoNazide); 292(1.2), 273(1.1), 258(1.5)
(dMoNazide); 216(1.2), 183(2.7), 161(1.7) cmꢀ1
.
[N(CH3)4][NW(N3)4]: weight found: 0.117 g, weight expected for
0.25 mmol: 0.110 g; Raman of the [NW(N3)4]ꢀ ion (50 mW, ꢀ808C):
n˜ = 2114(10.0), 2083(2.2), 2069(2.2), 2060(1.4), (nasN3); 1324(0.4),
ꢂ
1315(0.4), 1259(0.2) (nsN3); 1010(1.0), (nW N); 655(0.6), 632(0.7),
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611(0.3), 579(0.5) (dN3); 452(7.1), 416(0.7), 321(0.6) (nWNazide);
266(1.3), 262(1.3), 253(1.4), 247(1.4), 226(1.0) (dWNazide); 189(2.0),
118(4.0), 110(4.0), 100(4.1) cmꢀ1
[6] D. L. Hughes, M. Y. Mohammed, C. J. Pickett, J. Chem. Soc.
Dalton Trans. 1990, 2013 (trans-[MoN(N3)L2], [{m-MoN-
(N3)2}{NMo(N3)L2}2] (L = dppe)).
.
Theoretical Methods: The molecular structures and harmonic
vibrational frequencies were calculated using second-order many-
body perturbation theory[38] (denoted as MP2, but also known as
MBPT(2)) and also density functional theory (DFT) level using the
B3LYP hybrid functional,[39a–c] which included the VWN5 correlation
functional.[39d] The Stevens, Basch, Krauss, and Jaisen effective core
potentials and the corresponding valence-only basis sets were
[7] S. J. N. Burgmayer, J. L. Templeton, Inorg. Chem. 1985, 24, 2224
([M(CO)2(S2CNEt2)2N3]ꢀ (M = Mo, W)).
[8] D. Sellmann, W. Weber, G. Liehr, H. P. Beck, J. Organomet.
Chem. 1984, 269, 155 ([{(m-N3)3[M(CO)3]2}3] (M = Mo, W),
[W(CO)5N3]ꢀ).
[9] C. T. Kan, P. B. Hitchcock, R. L. Richards, J. Chem. Soc. Dalton
Trans. 1982, 79 (trans-[M(N3)(NO)(dppe)2] (M = Mo, W)).
[10] J. A. Broomhead, J. R. Budge, Aust. J. Chem. 1979, 32, 1187
([Mo(NCO)(N3)(NO)L2]ꢀ, [W(N3)2(NO)L2]ꢀ, [W(N3)(NO)-
(Me2SO)L2]) (L = S2CNEt2)).
[11] H. Behrens, E. Lindner, G. Lehnert, J. Organomet. Chem. 1970,
22, 665 ([M(CO)3(N3)L]ꢀ (M = Mo, W; L = 2,2’-bipyridine
(bipy), ethylenediamine)).
[12] G. Hoch, R. Panter, M. L. Ziegler, Z. Naturforsch. B 1976, 31,
294 ([(p-C7H7)M(CO)2(N3)] M = Mo, W)).
used.[40a–b] The basis set for nitrogen was augmented with
a
d polarization function (exponent of 0.8[40c]) and a diffuse s + p shell
(exponent of 0.0639[40d]), denoted as SBKJ + (d). Hessians (energy
second derivatives) were calculated for the final equilibrium struc-
tures to determine if they are minima (positive definite hessian) or
nth-order transition states (“n” negative eigenvalues). All calcula-
tions were performed using the electronic structure code
GAMESS.[47]
[13] a) J. Fawcett, R. D. Peacock, D. R. Russell, J. Chem. Soc. Dalton
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Chem. 1981, 20, 3580 ([WF5N3]).
Received: November 27, 2004
Published online: February 21, 2005
[14] B. Glavincevski, S. Brownstein, J. Inorg. Nucl. Chem. 1981, 43,
1827 ([WF5N3], [WF6N3]ꢀ).
[15] R. G. W. Gingerich, R. J. Angelici, J. Organomet. Chem. 1977,
132, 377 ([W(CO)5N3]).
[16] a) W. Palitzsch, C. Beyer, U. Bꢁhme, B. Rittmeister, G. Roewer,
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Chem. Soc. Chem. Commun. 1978, 20, 863; c) H. Werner, W.
Beck, H. Engelmann, Inorg. Chim. Acta 1969, 3, 331 ([W-
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[17] P. Dabas, R. Saxena, M. K. Rastogi, Asian J. Chem. 1997, 9, 453
([W(N3)3(OR)2] (R = Alkyl)).
[18] S. M. Musleh, P. Dabas, R. K. Multani, M. Katyal, Curr. Sci.
1985, 54, 138 ([WO(N3)2(OR)2] (R = Alkyl)).
[19] S. M. Musleh, M. K. Rastogi, R. K. Multani, Orient. J. Chem.
1986, 2, 11 ([WS2(N3)2]).
[20] D. Fenske, A. Frankenau, K. Dehnicke, Z. Anorg. Allg. Chem.
1989, 579, 27 ([WCl3(NCl)(CH3CN)(N3)], [WCl4(NCl)(N3)]ꢀ).
[21] I. Walker, J. Strꢃhle, P. Ruschke, K. Dehnicke, Z. Anorg. Allg.
Chem. 1982, 487, 26 ([{WNCl3·HN3}4])
[22] H.-w. Lam, G. Wilkinson, B. Hussain-Bates, M. B. Hursthouse, J.
Chem. Soc. Dalton Trans. 1993, 781 ([{W(NtBu)2(N3)-
(NH2tBu)}2(m-N3)2]).
[23] E. O. Fischer, D. Wittmann, D. Himmelreich, R. Cai, K.
Ackermann, D. Neugebauer, Chem. Ber. 1982, 115, 3152 ([(m-
N3)2{(CO)3WCNEt2}2]).
[24] T.-Y. Cheng, M. R. Smith, III, J. M. Dysard, J. Y. Ali, G. L.
Hillhouse, Polyhedron 1996, 15, 2551 (trans, trans-[W-
(NHNHPh)(N3)2(NO)(PPh3)2]).
[25] K. Dehnicke, J. Schmitte, D. Fenske, Z. Naturforsch. B 1980, 35,
1070; [AsPh4][MoN(N3)4].
[26] J. Beck, E. Schweda, J. Straehle, Z. Naturforsch. 1985, 40b, 1073;
[MoN(N3)2Cl(terpy)] (terpy = 2,2’:6’,2’’-terpyridine).
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Keywords: azides · molybdenum · nitrides ·
structure elucidation · tungsten
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L = 1,2-ethanediylbis-
1864
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Angew. Chem. Int. Ed. 2005, 44, 1860 –1865

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