Syntheses, structure, and reactivity of amino(azido)stibanes

Article abstract of DOI:10.1002/ejic.201101107

Amino(azido)stibanes Mes*N(SiMe₃)Sb(N₃)X (X = N₃, Cl, OTf) were synthesized and fully characterized. Their structures were determined by single-crystal X-ray diffraction and are rare examples of antimony azides. On account of weak Sb...X van der Waals interactions, centrosymmetric dimers are observed in the solid state. Mes*N(SiMe₃)Sb(OTf)X species (X = Cl, N₃, and OTf; OTf = triflate = CF₃SO₃^-) are labile with respect to Me₃Si-OTf elimination even at ambient temperatures and form in situ the highly reactive iminostibane Mes*N=SbX, which rapidly decomposes. Diazide Mes*N(SiMe₃)Sb(N₃)₂ slowly decomposes when a Lewis acid such as B(C₆F₅) ₃ is present, thus leading to the formation of a salt that bears a heterocyclic Sb-N dication and an [N₃-B(C₆F ₅)₃]^- adduct anion in good yields. Amino(azido)stibanes Mes*N(SiMe₃)Sb(N₃)X (X = N ₃, Cl, OTf) were synthesized and characterized. Their thermal stability with respect to Me₃Si-X elimination was studied. Copyright

Full text of DOI:10.1002/ejic.201101107

FULL PAPER
DOI: 10.1002/ejic.201101107
Syntheses, Structure, and Reactivity of Amino(azido)stibanes
Mathias Lehmann,[a] Axel Schulz,*[a,b] and Alexander Villinger[a]
Keywords: Main group elements / Antimony / Stibanes / Azides / Nitrogen heterocycles
Amino(azido)stibanes Mes*N(SiMe3)Sb(N3)X (X = N3, Cl,
OTf) were synthesized and fully characterized. Their struc-
tures were determined by single-crystal X-ray diffraction and
are rare examples of antimony azides. On account of weak
Sb···X van der Waals interactions, centrosymmetric dimers
are observed in the solid state. Mes*N(SiMe3)Sb(OTf)X spe-
cies (X = Cl, N3, and OTf; OTf = triflate = CF3SO3–) are labile
with respect to Me3Si–OTf elimination even at ambient tem-
peratures and form in situ the highly reactive iminostibane
Mes*N=SbX, which rapidly decomposes. Diazide
Mes*N(SiMe3)Sb(N3)2 slowly decomposes when a Lewis acid
such as B(C6F5)3 is present, thus leading to the formation of
a salt that bears a heterocyclic Sb–N dication and an [N3–
B(C6F5)3]– adduct anion in good yields.
Introduction
Four-membered heterocycles of the type [X–Sb(μ-NR)]2
are known as cyclo-1,3-distiba(III)-2,4-diazanes (X = halo-
gen, R = organic group). These ring systems are good start-
ing materials for polycyclic inorganic and organometallic
compounds.[1–3] The cyclo-distiba(III)-diazane [Cl–Sb(μ-
NtBu)]2 was first generated by the treatment of SbCl3 with
LiN(SiMe3)(tBu).[4] Stahl introduced a simple one-pot syn-
thesis of [Cl–Sb(μ-NtBu)]2 by using SbCl3 and tBuNH2.
The structure was determined by Chivers et al.[5,6]
Recently, a series of four-membered rings of the type [X–
Sb(μ-NR)]2, which contain alternating antimony(III) and
nitrogen centers, were synthesized and fully characterized
(X = halogen, R = supermesityl = 2,4,6-tri-tert-butylphenyl
= Mes*), and represent rare examples of cyclo-distibadi-
azanes.[7] The synthesis was carried out by starting from
Scheme 1. Synthesis of halogen-substituted cyclo-1,3-distiba-2,4-di-
azane (X = Cl, Br, I).
–
the triflate (triflate = CF3SO3 = OTf) species [TfO–Sb(μ-
We are interested in heterocycles of the type [X–E(μ-
NR)]2 with a central E2N2 ring (E = element of group 15)
as building blocks for cyclic 1,3-dipnicata-2,4-diazenium
cations[12] (Scheme 2) and nitrogen-rich compounds such as
cyclic or acyclic pnictogen azides[13] or binary heterocycles
such as tetraazapnictoles, which can be generated from
pnictogen azides by means of Lewis acids such as GaCl3 or
B(C6F5)3 (Scheme 3).[14]
Particularly useful for the synthesis of imino-stibanes R–
N=Sb–X (X = Cl, N3) are triflate-substituted species,
RN(SiMe3)Sb(OTf)X (X = Cl, N3), since intrinsic elimi-
nation of Me3Si–OTf (Scheme 1 and Scheme 4) may lead to
the in situ formation of an azido(imino)stibane, which can
either dimerize to give 1,3-diazido-cyclo-1,3-distiba-2,4-di-
azane or isomerize to a tetraazastibole when a Lewis acid
is added (Scheme 3). Here we report on the synthesis and
full characterization of Mes*N(SiMe3)Sb(N3)(OTf),
Mes*N(SiMe3)Sb(Cl)(N3), and Mes*N(SiMe3)Sb(N3)2 as
possible candidates.
NR)]2 (Scheme 1). By means of Me3Si–OTf elimination, re-
actions of [TfO–Sb(μ-NR)]2 with Me3Si–X yielded the
halogen compounds [X–Sb(μ-NR)]2, except for the fluorine
species, for which an iodine/fluorine exchange reaction with
AgF was successfully applied.
Niecke et al. reported the first monomeric iminochlo-
rophosphane Mes*–N=E–Cl (E = P).[8] The stabilities of
the monomeric species R–N=EIII–X (E = P, As, Sb; X =
Cl, OTf) with respect to the corresponding dimers by using
Mes* groups (Mes* = 2,4,6-tri-tert-butylphenyl) on N and
a chloro or triflate substituent on the pnictogen was only
recently studied.[9–11]
[a] Universität Rostock Institut für Chemie
Albert-Einstein-Strasse 3a, 18059 Rostock, Germany
E-mail: axel.schulz@uni-rostock.de
[b] Leibniz-Institut für Katalyse e.V. an der Universität Rostock,
Albert-Einstein-Strasse 29a, 18059 Rostock, Germany
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejic.201101107.
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Syntheses, Structure and Reactivity of Amino(azido)stibanes
not yet known. The only known acyclic antimony azides
reported are Sb(N3)3,[15,16] ClSb(N3)2,[17] [Sb(N3)4]–,[18]
[Sb(N3)4]+,[18] Sb(N3)5,[19] [Sb(N3)6]–,[19] and Sb(C6H5)4-
(N3).[20] Thus it was of interest to study R1–N(R2)–Sb(X)–
N3 species and their reactivity (e.g., with Lewis acids).
Synthesis
As shown in Scheme 4, amino(dichloro)stibane
Mes*N(SiMe3)SbCl2 (1) was used as starting material for
the synthesis of azido species of the type R1–N(R2)–Sb(X)–
N3 (X = Cl or OTf; R1 = Mes*, R2 = SiMe3). The amino-
(diazido)stibane Mes*N(SiMe3)Sb(N3)2 (4) is easily ob-
tained when a small excess amount of NaN3 is added in
one portion to a stirred solution of Mes*N(SiMe3)SbCl2
in THF at ambient temperatures. Removal of the solvent,
extraction with n-hexane, and concentration finally resulted
in the deposition of colorless crystals of Mes*N(SiMe3)-
Sb(N3)2 (4) in good yields (76%).
Scheme 2. Synthesis of nitrogen-rich cyclo-1,3-dipnicta-2,4-diazen-
ium cations (E = P, As).
In a second series of experiments, we studied the synthe-
sis of monoazido-stibanes Mes*N(SiMe3)Sb(N3)X, which
were substituted by either a triflate or chloride ion (species
5: X = OTf; 6: X = Cl). Mes*N(SiMe3)Sb(N3)(OTf) can be
obtained in a two-step reaction: Treatment of Mes*N-
(SiMe3)SbCl2 (1) with one equivalent of AgOTf gives
Mes*N(SiMe3)Sb(Cl)(OTf) (3) in good yields (65%),
whereas addition of a second equivalent of AgOTf leads to
the formation of Mes*N(SiMe3)Sb(OTf)2 (2), which is an
ideal precursor for the generation of monoazide 5. Triflate-
substituted aminostibanes are especially suitable for the
generation of halogen- and pseudohalogen-substituted
compounds by means of Me3Si–OTf elimination upon ad-
Scheme 3. Synthesis of tetrazastiboles (LA = Lewis acid).
Figure 1. ORTEP drawing of the molecular structure of 4 in the
crystal. Thermal ellipsoids with 30% probability at 173 K (hydro-
gen atoms omitted for clarity). Selected bond lengths [Å] and
angles [°]: Sb1–N1 2.008(2), Sb–N5 2.085(2), Sb1–N2 2.089(3), Si1–
N1 1.766(2), N1–C1 1.467(2), N2–N3 1.204(4), N3–N4 1.134(4),
N5–N6 1.151(3), N6–N7 1.170(4); N1–Sb1–N5 99.19(9), N1–Sb1–
N2 98.22(9), N5–Sb1–N2 84.3(1), C1–N1–Si1 116.0(1), C1–N1–
Sb1 115.9(1), Si1–N1–Sb1 128.14(9), N3–N2–Sb1 119.2(2), N4–
Scheme 4. Synthesis of amino(azido)stibanes.
Results and Discussion
To the best of our knowledge, monomeric acyclic amino-
(azido)stibanes of the type R1–N(R2)–Sb(X)–N3 (X = halo-
gen, pseudohalogen, OTf; R1,2 = organic substituents) are N3–N2 174.0(4), N6–N5–Sb1 122.2(2), N5–N6–N7 173.4(3).
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M. Lehmann, A. Schulz, A. Villinger
FULL PAPER
dition of Me3Si–X (X = halogen or pseudohalogen). For Properties and Characterization
instance, when one equivalent of Me3Si–N3 was added to a
solution of Mes*N(SiMe3)Sb(OTf)2 in CH2Cl2 at –60 °C,
Azidostibanes 4, 5, and 6 were fully characterized by
within 20 min the monoazido species 5 was formed upon NMR, IR, and Raman spectroscopy, elemental analysis,
Me3Si–OTf elimination after warming to ambient tempera- and single-crystal structure elucidation (Figures 1, 2, 3, and
tures (yield: 85%). Even monoazide 6 can now easily be 4). As illustrated in Scheme 4, there are different synthetic
generated from Mes*N(SiMe3)Sb(N3)(OTf) (5) simply by routes but all afford species 4, 5, and 6 as colorless micro-
addition of Me3Si–Cl, which triggers the elimination of crystalline solids in good yields (Ͼ60%). Azide formation
Me3Si–OTf and the exchange of OTf by Cl. It should be can easily be detected by means of IR spectroscopy. The
noted that species 2 and 5 already slowly eliminate Me3Si– vibrational spectra of all three azides feature the presence
OTf at ambient temperatures in polar solvents such as of covalently bound azido ligands as shown by the asym-
CH2Cl2.
metrical stretching mode in the range 2200–2000 cm–1
Figure 2. Section of the chain composed of [···Sb–NNN···Sb–] units in the crystal in 4. Two types of bonds form the chain: Sb1–N5
2.085(2) and Sb1···N7Ј 3.196(4) Å.
Figure 3. ORTEP drawing of the molecular structure of 5 (left) and 6 (right) in the crystal. Thermal ellipsoids with 30% probability at
173 K (hydrogen atoms omitted for clarity). Selected bond lengths [Å] and angles [°]; 5: Sb1–N1 1.985(1), Sb1–N2 2.052(1), Sb1–O1
2.178(1), Si3–N1 1.789(1), N1–C1 1.466(2), N2–N3 1.223(2), N3–N4 1.133(2); N1–Sb1–N2 92.90(5), N1–Sb1–O1 95.26(4), N2–Sb1–O1
87.07(5), S1–O1–Sb1 121.57(7), C1–N1–Sb1 112.67(8), Si3–N1–Sb1 127.33(6), N3–N2–Sb1 121.4(1), N4–N3–N2 174.7(2); 6: Sb1–Cl1
2.4347(5), Sb1–N2 2.105(2), Sb1–N1 2.007(1), N2–N3 1.166(2), N3–N4 1.138(3), Si1–N1 1.769(2), N1–C1 1.454(2), N1–Sb1–N2 93.53(6),
N1–Sb1–Cl1 103.31(4), N2–Sb1–Cl1 89.94(5), C1–N1–Si1 116.5(1), C1–N1–Sb1 116.4(1), Si1–N1–Sb1 126.7(7), N3–N2–Sb1 117.6(1),
N4–N3–N2 174.9(2).
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Syntheses, Structure and Reactivity of Amino(azido)stibanes
Figure 4. Formation of centrosymmetric dimers through small intermolecular interactions in monoazides 5 (left) and 6 (right).
[νas(N3) = 2092 (4), 2095 (5), 2103 cm–1 (6)], the symmetri- X-ray Crystallography
cal stretching mode at 1400–1200 cm–1, and the defor-
mation mode at 700–600 cm–1. The Sb–N stretching modes
The structures of compounds 2–6, 9, and 10 (compounds
are found in the range 450–350 cm–1 [414–455 (4), 423 (5), 9 and 10 will be introduced in the next chapter) have been
407 (6), cf. 382–421 cm–1 in Sb(N3)5 and 370–386 cm–1 in determined. Tables 1 and 2 present the X-ray crystallo-
Sb(N3)3].[16a,19] The presence of more than one azido ligand graphic data. X-ray-quality crystals of all considered species
results in in-phase and out-of-phase coupling.
were selected in Kel-F-oil (Riedel-de Haën) or Fomblin
Compounds 4, 5, and 6 are air- and moisture-sensitive YR-1800 (Alfa Aesar) at ambient temperature. All samples
but stable under an argon atmosphere over a long period were cooled to –100(2) °C during the measurement.
as solid; however, they slowly decompose in solvents such
The molecular structures of azides 4, 5, and 6 are shown
as THF even at ambient temperatures. Both the mono- and in Figures 1, 2, 3, and 4, and of starting materials 2 and 3
the diazides are neither heat- nor shock-sensitive and are in Figures 5 and 6, respectively, along with selected bond
thermally stable up to over 90 °C. Presumably decomposi- lengths and angles. More details are found in the Support-
tion starts with the intrinsic elimination of Me3Si–OTf. In ing Information.
the solid state, the thermally most stable compound is di-
Diazide Mes*N(SiMe3)Sb(N3)2 (4) crystallizes in the tri-
¯
azido species 4 with a decomposition temperature of clinic space group P1 with two formula units per cell. The
148 °C, followed by compound 6 (Tdec. = 120 °C). Monoaz- structure consists of separated Mes*N(SiMe3)Sb-
ide 5 already decomposes at 95 °C without explosion. All (N3)2 molecules with two disordered tBu groups. In con-
three azidostibanes can be prepared in bulk.
trast to the trigonal pyramidal Sb atom, the nitrogen atom
Table 1. Crystallographic details of 2, 3, and 4.
Mes*N(SiMe3)Sb(OTf)2 (2)
Mes*N(SiMe3)Sb(Cl)(OTf) (3)
Mes*N(SiMe3)Sb(N3)2 (4)
Formula
Mr [gmol–1]
Color
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
C23H38F6NO6S2SbSi·0.5(C6H14)
C22H38ClF3NO3SSbSi
638.88
colorless
C21H38N7SbSi
538.42
colorless
monoclinic
P21/c
12.2068(4)
8.4027(3)
25.5240(9)
90
101.248(1)
90
2567.7(2)
4
1.393
1.142
173(2)
44137
9299
6996
0.0376
1112
795.59
colorless
triclinic
triclinic
¯
¯
P1
P1
10.5338(4)
12.8586(5)
14.8720(5)
77.470(2)
74.657(2)
65.953(2)
1760.4(1)
2
1.501
1.005
173(2)
42168
11844
10.1239(3)
16.8725(5)
26.5485(8)
108.099(1)
100.612(1)
90.3640(10)
4227.0(2)
6
1.506
1.233
173(2)
81600
γ [°]
V [Å3]
Z
ρcalcd. [gcm–3]
μ [mm–1]
T [K]
Measured reflections
Independent reflections
Reflections [IϾ2σ(I)]
Rint
22306
18109
0.0261
1956
10119
0.0317
814
F(000)
R1 {R[IϾ2σ(I)]}
wR2 (F2)
GoF
0.0286
0.077
1.075
0.0285
0.0760
1.064
0.0379
0.0950
1.063
Parameters
401
928
345
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M. Lehmann, A. Schulz, A. Villinger
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Table 2. Crystallographic details of 5, 6, and 10.
Mes*N(SiMe3)Sb(N3)(OTf) (5)
Mes*N(SiMe3)Sb(Cl)(N3) (6)
Compound 10
Formula
Mr [gmol–1]
Color
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
C22H38F3N4O3SSbSi·CH2Cl2
C21H38ClN4SbSi
531.84
colorless
monoclinic
P21/c
10.2880(4)
25.179(1)
10.4115(4)
90
C30H48N4Sb2·2(C18BF15N3)
1816.26
red
monoclinic
P21/c
9.8897(3)
17.0327(5)
20.4230(7)
90
730.39
colorless
monoclinic
P21/n
10.4273(4)
16.8836(5)
19.0314(6)
90
β [°]
103.313(2)
90
3260.5(2)
4
1.488
1.158
173(2)
43552
11626
9504
0.0232
1488
103.855(1)
90
2618.5(2)
4
1.349
1.215
173(2)
29673
7606
6266
0.0361
1096
94.453(2)
90
3429.8(2)
2
1.759
0.920
173(2)
56893
12057
9585
0.0363
1792
γ [°]
V [Å3]
Z
ρcalcd. [gcm–3]
μ [mm–1]
T [K]
Measured reflections
Independent reflections
Reflections [IϾ2σ(I)]
Rint
F(000)
R1 {R[IϾ2σ(I)]}
wR2 (F2)
GoF
0.0259
0.0695
1.070
0.0269
0.0657
1.038
0.0362
0.0827
1.043
Parameters
395
265
515
sits in a trigonal-planar environment (ΣՄ = 360.0°) with an in compounds 5 and 6 the antimony adopts a trigonal-py-
Sb–Namino single bond of 2.008(2) Å (Sb–N1), whereas the ramidal geometry attached to a planar nitrogen atom (Fig-
two Sb–Nazide single bonds are considerably longer with ure 3). Since the structural parameters for all three azide
values of 2.085(2) (Sb–N5) and 2.089(3) Å (Sb1–N2), compounds (4, 5, and 6) are very similar with respect to the
respectively. These Sb–Namino and Sb–Nazide bonds lie in Mes*N–Sb–N3 moiety, we would like to focus only on the
the expected range for aminostibanes, for example, d(Sb– differences. Although the Sb–Cl bond length of 2.4347(5) Å
Namino
amino) = 2.092(2) and d(Sb–Nazide) = 2.104(2) in [tBuC- 2.39 Å] in azide 6, the Sb–O distance [2.178(1) Å] is rather
(iPrN)2]Sb(N3)2,[21] and d(Sb–Nazide
2.119(4) Å in long compared to sum of the covalent radii (2.04 Å). This
) =
2.056(3) in Mes*N(SiMe3)SbCl2,[7] d(Sb– is in the typical range for a single bond [cf. Σrcov.(Sb–Cl) =
N
)
=
Sb(N3)3[16] [cf. Σrcov.(Sb–N) = 2.11 Å].[22] The angles around might partly be attributed to an intramolecular donor–ac-
the antimony center vary strongly from 99.19(9) (N1–Sb1– ceptor interaction (negative hyperconjugation)[25] between
N5)/98.22(9) (N1–Sb1–N2) to 84.3(1)° (N5–Sb1–N2), the lone pair (which occupies a p-type atomic orbital) lo-
which gives a difference of around 14°. For both azido li- cated at the amino-nitrogen atom (N1) and the antibonding
gands, the typical trans-bent structure with N–N–N angles Sb–O bond, which results in a weakening of the latter bond
of about 173–174° is observed.[23] The Nα–Nβ bonds differ while introducing a small amount of π bonding along the
significantly [1.204(4) versus 1.151(3) Å], and also the Nβ– Sb–Namino unit in accord with a short Sb–N1 bond
Nγ bond length is slightly different with values of 1.134(4) [1.985(1) Å; cf. Σrcov.(Sb–N) = 2.11 Å].[22]
(N3–N4) and 1.170(4) Å (N6–N7). This difference in bond
The asymmetric unit of 5 and 6 consists of a
lengths can be attributed to intermolecular interactions Mes*NSb(N3)(OTf) (and one molecule of CH2Cl2) and a
(Figure 1). A closer look at the intermolecular interactions Mes*NSb(Cl)(N3) molecule, respectively, but with small but
in 4 reveals an expansion of the Sb coordination number significant symmetric intermolecular interactions that lead
by the formation of nitrogen bridges that involves the γ- to the formation of centrosymmetric dimers (Figure 4).
nitrogen atom (N7) of only one azido ligand. These in- Whereas in 5 only one stronger Sb1···O2Ј interaction
terionic distances are rather long with values of 3.196(4) Å [3.009(1); cf. ΣrvdW(Sb···O) = 3.7 Å and d(Sb···N5Ј) =
[cf. ΣrvdW(Sb···N) = 3.8 Å];[24] however, they are responsible 3.715(2) Å] between the Sb center and one oxygen atom of
for the formation of a chainlike structure as depicted in an adjacent triflate group is observed, in 6 both the Cl and
Figure 2. A similar situation was found by Stahl et al. in the Nγ,azide atom display weak contacts with the Sb centers
diazido-cyclo-distibadiazane [N3–Sb(μ-NtBu)]2, which [Sb1···Cl1Ј 3.4902(5) Å, cf. ΣrvdW(Sb···Cl) = 4.0 Å and
forms a layer structure of associated molecules, with inter- Sb1···N2Ј 3.627(2) Å, cf. ΣrvdW(Sb···N) = 3.8 Å].
molecular Sb···N contacts of 3.226 Å.
Mes*N(SiMe3)Sb(OTf)2·0.5 C6H14 (2·0.5n-hexane) and
Monoazides 5·CH2Cl2 and 6 crystallize in the monoclinic Mes*N(SiMe3)Sb(Cl)(OTf) (3) crystallize in the triclinic
¯
space groups P21/n and P21/c, respectively, with four for- space group P1 with two and six formula units per cell,
mula units per cell. As discussed before for diazide 4, also respectively. Furthermore, chlorotriflate 3 was also crys-
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Syntheses, Structure and Reactivity of Amino(azido)stibanes
tallized from toluene, which led to the formation of mono- that consists of one Mes*N(SiMe3)Sb(Cl)(OTf) molecule
clinic crystals (space group P21) with an asymmetric unit along with one toluene molecule (Figure 5). In 3·toluene,
significant solvent···antimony interaction in an η6 fashion
[Sb···Caryl distances between 3.42–3.57 Å, cf. ΣrvdW(Sb···C)
= 3.9 Å] but no dimer formation due to intermolecular in-
teractions between adjacent Mes*N(SiMe3)Sb(Cl)(OTf)
molecules is observed. In contrast, for 2·0.5n-hexane, no
solvent interactions but centrosymmetric dimer formation
due to strong Sb···O interactions are found (Figure 6).[7] Be-
sides two intermolecular van der Waals contacts [Sb1···O3Ј
3.541(1) and Sb1···O6Ј 3.546(2) Å], two intramolecular con-
tacts [Sb1···O3Ј 3.135(2) and Sb1···O6Ј 3.311(2) Å] can also
be found. By these four interactions a Sb2O4 octahedron is
built (Figure 6, right). Also Mes*N(SiMe3)Sb(Cl)(OTf) (3)
forms a centrosymmetric dimer due to intra- and intermo-
lecular interactions [Sb1···O2 3.314(2) and Sb1···O2Ј
3.145(1) Å] as depicted in Figure 6 (left), however, no sig-
nificant Sb···ClЈ contacts are observed [Sb···ClЈ 4.713(5) Å].
Compared to compounds 5 and 6, similar structural fea-
tures with respect to bond lengths and angles are found for
2 and 3 (Figure 5).
Reactivity – Decomposition
Amino(azido)stibanes of the type Mes*N(SiMe3)–
Sb(N3)Y (4: Y = N3, 5: OTf, and 6: Cl) were synthesized
to study the possibility of an intrinsic Me3Si–Y elimination,
which generates in situ a reactive imino(azido)stibane as il-
lustrated in Scheme 5. Imino(azido)stibanes that bear an
Sb=N double bond can either dimerize along this double
bond forming a [N3–Sb(μ-NMes*)]2 heterocycle (7) or cy-
clize to give a tetraazastibole (8), a compound which was
recently obtained by an unusual isomerization reaction
starting from
7
upon addition of
a
Lewis acid
(Scheme 5).[10,13] Like Mes*N(SiMe3)Sb(OTf)2 (2), which
eliminates Me3Si–OTf at ambient temperatures to lead fi-
nally to the formation of the corresponding cyclo-1,3-dis-
tiba-2,4-diazane [OTf–Sb(μ-NMes*)]2,[7] Mes*N(SiMe3)-
Sb(Cl)(OTf) (3) isomerizes at 70 °C in n-hexane to result in
the formation of a mixture of Mes*N(SiMe3)SbCl2 (1) and
2, which further eliminates Me3Si–OTf to yield [OTf–Sb-
(μ-NMes*)]2 (Schemes 1 and 6). Also monoazide
Mes*N(SiMe3)Sb(N3)(OTf) (5) slowly decomposes in
CH2Cl2 and releases Me3Si–OTf. In this case, only Mes*–
N3 (9) (yield: 42%) and Me3Si–OTf could be observed as
products in this decomposition reaction (Scheme 6), which
suggests the elimination of Me3Si–OTf at the beginning fol-
Figure 5. ORTEP drawing of the molecular structure of 2·0.5n-hex-
ane (top), 3 (middle), and 3·toluene (bottom) in the crystal. Ther-
mal ellipsoids with 30% probability at 173 K (hydrogen atoms lowed by formation and decomposition of a tetrazastibole.
omitted for clarity). Selected bond lengths [Å] and angles [°]: 2:
Mes*–N3 (9) was characterized by an X-ray structure deter-
Sb–N 1.965(1), Sb–O1 2.069(1), Sb–O4 2.095(1), N–C1 1.467(2),
mination. In addition to the known triclinic structure (9a),
N–Si 1.803(1); C1–N–Sb 115.73(9), Si–N–Sb 128.80(7), N–Sb–O1
a new monoclinic modification was obtained (9b) (see the
91.22(5), N–Sb–O4 95.90(5), O1–Sb–O4 82.22(5), S1–O1–Sb
121.58(6), S2–O4–Sb 126.49(7). 3C Sb1–N1 1.998(1), Sb1–O1
Supporting Information).[26] In contrast to compound 5,
2.159(1), Sb1–Cl1 2.338(5); N1–Sb1–O1 98.67(6), N1–Sb1–Cl1
98.74(4), O1–Sb1–Cl1 88.49(4), S1–O1–Sb1 125.35(9), C1–N1–Si1
126.3(1), C1–N1–Sb1 105.7(1). 3·toluene: Sb–N 2.005(2), Sb–O1
2.117(2), Sb–Cl 2.375(1), Sb···centroid 3.203(1); N–Sb–O1 91.61(6),
N–Sb–Cl 104.44(5), O1–Sb–Cl 87.38(5), S1–O1–Sb 124.7(1), C1–
N–Si 128.0(2), C1–N–Sb 103.2(2).
species 1, 4, and 6 do not eliminate Me3Si–Y even at ele-
vated temperatures. Diazide 4 is thermally relatively stable.
For this reason, we added the Lewis acid B(C6F5)3 to trig-
ger the intrinsic elimination of Me3Si–N3. But even under
these conditions the decomposition reaction is rather slow.
Eur. J. Inorg. Chem. 2012, 822–832
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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827

M. Lehmann, A. Schulz, A. Villinger
FULL PAPER
Figure 6. Formation of centrosymmetric dimers through small intermolecular interactions in 5 (left) and 6 (right).
It took about five days for a complete decomposition in picted in Scheme 7. The anion was first described by
CH2Cl2 at ambient temperatures to lead in good yields Klapötke et al. in 2002.[27] We do want to stress that the
(Ͼ50%) to an intriguing dimeric heterocyclic Sb–N dication preparation of the salt that contains the heterocyclic Sb–N
with an azide–borane adduct anion, [N3–B(C6F5)3]–, as de- dication (10) can be reproduced in good yields although we
know only very little about its formation. Sb–N dication
with the [N3–B(C6F5)3]– counterion (10) can be isolated as
deep red crystals from CH2Cl2. Crystals of 10 are neither
heat- nor shock-sensitive and decompose above 173 °C.
The dimeric cyclic Sb–N ion represents one of the rare
examples of nitrogen–antimony cations.[28] Formally, the di-
cation from 10 can be regarded as a dimer of a diazastibol-
ium monocation (Scheme 7). Compound 10 crystallizes in
the monoclinic space group P21/c with two formula units
per cell. The structure consists of separated centrosymmet-
ric dications and [N3–B(C6F5)3]– anions (Figure 7). Only
two weak Sb···FC F [Sb···F11 3.216(1), Sb···F1Ј 3.439(1) Å]
6
5
and two Sb···Nazide [Sb···N3 3.302(2), Sb···N5Ј 3.600(2) Å]
contacts are found. The central Sb2N2 ring is planar with
two significant different Sb–N distances [Sb1–N1 2.103(2),
Sb1–N1Ј 2.315(2) Å] as well as all other cycles to form a
planar framework of five condensed cycles in the dication.
The Sb–N2 distance amounts to Sb1–N2 2.239(2) Å [cf.
Σrcov(Sb–N) = 2.11 Å].[22] The coordination sphere around
the antimony(III) can be best understood as a strongly dis-
torted bisphenoidal arrangement with the axial unit along
N2–Sb–N1Ј [N1–Sb1–C1 91.15(9), N1–Sb1–N2 73.35(6),
C1–Sb1–N2 85.42(9), N1–Sb1–N1Ј 71.12(6), C1–Sb1–N1Ј
86.82(9), N2–Sb1–N1Ј 143.41(6)°] when the weak van der
Waals interactions are not considered.
Scheme 5. Application of amino(azido)stibanes (4: Y = N3, 5: Y =
OTf, 6: Y = Cl; LA = Lewis acid).
Scheme 6. Decomposition of 3 and 5.
828
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© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 822–832

Syntheses, Structure and Reactivity of Amino(azido)stibanes
Scheme 7. Reaction of 4 with B(C6F5)3 to 10.
C(aryl) bond length of 1.647 Å. The coordination geometry
around boron in the tetrahedral BC3N core is slightly dis-
torted with the smallest angle of 105.7, and the largest
114.1°. The B1–N3–N4 angle amounts to 120.4(2)°.
Conclusion
Amino(azido)stibanes of the type Mes*N(SiMe3)Sb-
(N3)Y (Y = N3, OTf, and Cl) were synthesized to study the
possibility of an intrinsic Me3Si–Y elimination. They are
easily obtained either by Cl/N3 substitution reactions or the
elimination of Me3Si–OTf when triflate-substituted precur-
sors are treated with Me3Si–N3. The solid-state structures
of the monoazides 5 and 6 as well as diazide 4 revealed the
formation of centrosymmetric dimers facilitated by weak
Sb···Z van der Waals interactions (Z = O, N, Cl atoms).
Triflate-substituted amino(azido)stibanes slowly decom-
pose even at ambient temperatures in CH2Cl2 to form in
situ a highly reactive iminostibane when an adjacent Me3Si
group is available. Without a triflate group such as in diaz-
ide 4, amino(azido)stibanes are relatively stable with respect
to Me3Si–N3 elimination. However, by addition of a Lewis
acid, decomposition is strongly enhanced, thereby resulting
Figure 7. ORTEP drawing of the decomposition product 10 in the
crystal. Thermal ellipsoids with 30% probability at 173 K (hydro-
gen atoms omitted for clarity). Selected bond lengths [Å] and
angles [°]: Sb1–N1 2.103(2), Sb1–N2 2.239(2), Sb1–N1Ј 2.315(2),
Sb1–C1 2.133(2), N1–C2 1.290(2), N2–C3 1.288(2), B1–N3
1.590(2), B1–C22 1.644(3), B1–C28 1.648(3), B1–C16 1.650(3), N3–
N4 1.208(2), N4–N5 1.138(2); N1–Sb1–C1 91.15(9), N1–Sb1–N2
73.35(6), C1–Sb1–N2 85.42(9), N1–Sb1–N1Ј 71.12(6), C1–Sb1–
N1Ј 86.82(9), N2–Sb1–N1Ј 143.41(6), C2–N1–Sb1 119.3(1), C2–
N1–Sb1Ј 131.3(1), C3–N2–Sb1 117.3(1), N3–B1–C22 106.4(1), N3–
B1–C28 107.3(1), C22–B1–C28 109.8(1), N3–B1–C16 105.7(1), in the formation of a salt that bears an intriguing dimeric
cyclic Sb–N dication and the adduct anion [N3–B(C6F5)3]–.
C22–B1–C16 114.13(2), C28–B1–C16 113.0(2), N4–N3–B1
120.4(2), N5–N4–N3 174.6(2).
The dimeric cyclic Sb–N ion represents one of the rare ex-
amples of antimony dication.
The adduct anion [N3–B(C6F5)3]– belongs to a class of
adduct anions of strong Lewis acids such as [(F5C6)3B(μ-X)-
B(C6F5)3]– (X = CN, OH),[29–31] [Y–B(C6F5)3]– (OH),[32–36]
Experimental Details
[N{CN·B(C6F5)3}2]–,
[C{CN·B(C6F5)3}3]–,
[B{CN·B-
General Information: All manipulations were carried out under
oxygen- and moisture-free conditions by using standard Schlenk
and drybox techniques.
(C6F5)3}4]–,[37] [NO3·B(C6F5)3]–, or even [SO4·2B-
(C6F5)3]2–.[38] These anions are easily prepared in a simple
acid/base reaction. For example, an excess amount of
B(C6F5)3 is added to basic anions such as dicyanoamide or
nitrate to give in almost quantitative yields adduct anions
with astonishingly stable borate units. An example of an
azide-diadduct anion is [N3(GaCl3)2]– with two GaCl3 units
attached to the same N atom (Scheme 2).[12a,12f,39]
The azide ion distorts upon complexation from Dϱh to
Cs symmetry with two different N–N bond lengths [N3–N4
1.208(2), N4–N5 1.138(2) Å; N1–N2–N3 174.6(2)°]. The
azide anion (Figure 7) and the B(C6F5)3 group are con-
nected by means of a strong B–N bond {B1–N3 1.590(2) Å;
cf. 1.616(3) Å in CH3CN·B(C6F5)3;[40] 1.658 Å in H3N–
BH3;[41] 1.987(3) and 1.974(3) Å in [N3(GaCl3)2]–}.[39] The
Dichloromethane was purified according to a literature pro-
cedure,[42] dried first with P4O10 and secondly with CaH2, then
freshly distilled prior to use. CH3CN was dried with P4O10 and
freshly distilled prior to use. Tetrahydrofuran (THF) and toluene
were dried with Na/benzophenone and freshly distilled prior to use.
n-Hexane was dried with Na/benzophenone/tetraglyme and freshly
distilled prior to use.
Trimethylsilyl chloride (99%, Merck) and trimethylsilyl azide (99%,
Fluka) were distilled prior to use. NaN3 (99%, Acros) was used as
received. Silver trifluoromethylsulfonate (AgOTf),[43] dichloro-
[(2,4,6-tri-tert-butylphenyl)(trimethylsilyl)amino]stibane (Mes*N-
(SiMe3)SbCl2, 1), [(2,4,6-tri-tert-butylphenyl)(trimethylsilyl)amino]-
bis(trifluoromethylsulfonyl)stibane (Mes*N(SiMe3)Sb(OTf)2, 2),[7]
[44]
central boron atom is tetracoordinate with an average B– and B(C6F5)3 were prepared according to literature procedures.
Eur. J. Inorg. Chem. 2012, 822–832
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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829

M. Lehmann, A. Schulz, A. Villinger
FULL PAPER
13C{1H}, 13C DEPT, H, 19F{1H}, and 29Si INEPT NMR spectra (2), 1392 (1), 1287 (2), 1235 (2), 1213 (3), 1202 (3), 1180 (2), 1144
1
were obtained with a Bruker AVANCE 300 spectrometer or a
Bruker AVANCE 500 spectrometer and were referenced internally
to the deuterated solvent [13C, CD2Cl2: δref = 54.0 ppm, CDCl3:
δref = 77.0 ppm, OC4D8 ([D8]THF): δref = 67.4 ppm] or to protic
impurities in the deuterated solvent (1H, CDHCl2: δref = 5.31 ppm,
CHCl3: δref = 7.26 ppm, OC4D7H: δref = 3.57 ppm). CD2Cl2 and
CDCl3 were dried with P4O10, [D8]THF was dried with Na/benzo-
phenone. A Nicolet 380 FTIR with a Smart Orbit ATR device
was used for IR spectroscopy. For Raman spectroscopy, a Bruker
VERTEX 70 FTIR instrument with a RAM II FT-Raman module
and equipped with an Nd:YAG laser (1064 nm) was used. An Ana-
lysator Flash EA 1112 from Thermo Quest or a C/H/N/S-Mikron-
alysator TruSpec-932 from Leco was used for C, H, N analyses.
Melting points: EZ-Melt, Stanford Research Systems, heating rate
20 °Cmin–1 (clearing-points are reported). Mass spectrometry was
carried out with a Finnigan MAT 95-XP from Thermo Electron.
(2), 1099 (1), 1029 (1), 1003 (2), 936 (1), 923 (1), 868 (1), 821 (2),
785 (1), 765 (2), 712 (1), 634 (1), 572 (2), 469 (1), 374 (1), 339 (2),
318 (4), 245 (2), 148 (1), 118 (1) cm–1.
Mes*N(SiMe3)Sb(N3)2 (4): NaN3 (2 mmol, 0.13 g) was added in
one portion at ambient temperatures to a stirred solution of
Mes*N(SiMe3)SbCl2 (1 mmol, 0.53 g) in THF (10 mL), and the re-
sulting colorless suspension was stirred for 20 h. The solvent was
removed under vacuum, and the colorless residue was extracted
with n-hexane (10 mL) and filtered (F4). The colorless solution was
concentrated to about 2 mL and stored at +5 °C for several hours,
which resulted in the deposition of colorless crystals of solvent by
syringe. Drying yielded 0.41 g (0.76 mmol, 76%) of Mes*N(SiMe3)-
Sb(N3)2 (4) as a colorless crystalline solid; m.p. 148 °C (dec.).
C21H38N7SbSi (538.42): calcd. C 46.85, H 7.11, N 18.21; found C
1
47.75, H 7.39, N 18.06. H NMR (25 °C, CD2Cl2, 300.13 MHz): δ
= 0.20 [s, 9 H, Si(CH3)3], 1.29 (s, 9 H, p-tBu), 1.55 (s, 18 H, o-tBu),
X-ray Structure Determination: X-ray-quality crystals of 2, 3,
3·toluene, 4, 5, 6, 9a, 9b, and 10 were selected in Kel-F-oil (Riedel
deHaen) or Fomblin YR-1800 (Alfa Aesar) at ambient tempera-
tures. All samples were cooled to 173(2) K during measurement.
The data were collected with a Bruker Apex Kappa-II dif-
fractometer using graphite-monochromated Mo-Kα radiation (λ =
0.71073 Å). The structures were solved by direct methods
(SHELXS-97)[45] and refined by full-matrix least-squares pro-
cedures (SHELXL-97).[46] Semiempirical absorption corrections
were applied (SADABS).[47] All non-hydrogen atoms were refined
anisotropically; hydrogen atoms were included in the refinement at
calculated positions using a riding model.
7.45 (s,
75.48 MHz):
2
H, CH) ppm. 13C{1H} NMR (25 °C, CD2Cl2,
δ
= 4.06 [Si(CH3)3], 31.56 [C(CH3)3], 35.05
[C(CH3)3], 35.62 [C(CH3)3], 38.51 [C(CH3)3], 125.86 (CH), 139.27
(Ar–C), 147.57 (Ar–C), 149.77 (Ar–C) ppm. 29Si INEPT NMR
(25 °C, CD2Cl2, 49.70 MHz): δ = 14.6 [Si(CH3)3] ppm. IR (ATR,
25 °C, 32 scans): ν = 3390 (vw), 3334 (vw), 2957 (m), 2905 (m),
˜
2863 (m), 2092 (s), 2078 (s), 1599 (w), 1556 (vw), 1539 (vw), 1520
(vw), 1505 (vw), 1487 (w), 1471 (m), 1461 (m), 1457 (m), 1435 (w),
1404 (m), 1391 (m), 1361 (m), 1314 (m), 1263 (m), 1250 (s), 1213
(m), 1198 (m), 1172 (m), 1140 (m), 1030 (vw), 1020 (vw), 939 (vw),
910 (w), 887 (m), 850 (s), 832 (s), 768 (m), 749 (s), 727 (s), 683 (m),
673 (m), 643 (s), 578 (m), 550 (w), 538 (m) cm–1. Raman (75 mW,
25 °C, 500 scans): ν = 3479 (1), 3069 (1), 2963 (9), 2905 (10), 2866
˜
CCDC-852780 (for 2), -852781 (for 3), -852783 (for 4), -852784 (for
5), -852785 (for 6), and -852786 (for 10) contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
(5), 2777 (1), 2708 (1), 2095 (6), 2079 (3), 1600 (4), 1453 (3), 1406
(1), 1362 (1), 1317 (1), 1287 (1), 1249 (2), 1200 (2), 1175 (3), 1140
(3), 1101 (2), 1025 (1), 922 (1), 824 (2), 748 (1), 729 (2), 684 (1),
645 (1), 632 (1), 570 (2), 508 (1), 488 (1), 455 (1), 414 (6), 274 (1),
237 (1), 220 (1), 181 (1), 130 (1) cm–1.
Mes*N(SiMe3)SbCl(OTf) (3): AgOTf (1 mmol, 0.26 g) in toluene
(5 mL) was added over a period of five minutes at 0 °C to a stirred
solution of Mes*N(SiMe3)SbCl2 (1 mmol, 0.53 g) in toluene
(10 mL), and the resulting colorless suspension was stirred for two
hours. The solvent was removed under vacuum, and the colorless
residue was extracted with n-hexane (10 mL) and filtered (F4). The
colorless solution was concentrated to about 2 mL and stored at
+5 °C for several hours to result in the deposition of colorless crys-
tals. Removal of solvent by syringe and drying yielded 0.42 g
Mes*N(SiMe3)Sb(N3)(OTf) (5): Me3SiN3 (1 mmol, 0.12 g) in
CH2Cl2 (3 mL) was added over a period of five minutes at –60 °C
to a stirred solution of Mes*N(SiMe3)Sb(OTf)2 (1 mmol, 0.75 g) in
CH2Cl2 (10 mL). The resulting colorless solution was warmed to
room temperature over a period of 20 min. The solvent was re-
moved under vacuum, and the colorless residue was recrystalized
from n-hexane. Removal of solvent by syringe and drying yielded
0.55 g (0.85 mmol, 85%) of Mes*N(SiMe3)SbN3(OTf) (5) as a col-
(0.65 mmol, 65%) of Mes*N(SiMe3)SbCl(OTf) (3) as a colorless orless crystalline solid; m.p. 95 °C (dec.). C22H38N4F3O3SSbSi
crystalline solid; m.p. 113 °C (dec.). C22H38NClF3O3SSbSi
(638.88): calcd. C 41.36, H 5.99, N 2.19; found C 41.49, H 5.96, N
2.11. 1H NMR (25 °C, CD2Cl2, 300.13 MHz): δ = 0.29 [s, 9 H,
Si(CH3)3], 1.30 (s, 9 H, p-tBu), 1.56 (s, 18 H, o-tBu), 7.51 (s, 2 H,
CH) ppm. 13C{1H} NMR (25 °C, CD2Cl2, 75.48 MHz): δ = 4.57
(645.47): calcd. C 40.94, H 5.93, N 8.68; found C 40.75, H 5.84, N
7.26. 1H NMR (25 °C, CD2Cl2, 300.13 MHz): δ = 0.23 [s, 9 H,
Si(CH3)3], 1.29 (s, 9 H, p-tBu), 1.54 (s, 18 H, o-tBu), 7.48 (s, 2 H,
CH) ppm. 13C{1H} NMR (25 °C, CD2Cl2, 75.48 MHz): δ = 4.10
[Si(CH3)3], 31.49 [C(CH3)3], 35.12 [C(CH3)3], 35.94 [C(CH3)3],
[Si(CH3)3], 31.50 [C(CH3)3], 35.51 [C(CH3)3], 36.11 [C(CH3)3], 38.60 [C(CH3)3], 119.30 [q, 1J(13C,19F) = 318.2 Hz, CF3], 126.20
38.74 [C(CH3)3], 119.10 [q, 1J(13C,19F) = 318.4 Hz, CF3], 126.46 (CH), 136.37 (Ar–C), 148.62 (Ar–C), 149.71 (Ar–C) ppm. 19F
(CH), 135.79 (Ar–C), 149.00 (Ar–C), 150.23 (Ar–C) ppm. 19F
NMR: δ = (25 °C, CD2Cl2, 282.38 MHz): –77.17 (CF3) ppm. 29Si
INEPT NMR (25 °C, CD2Cl2, 49.70 MHz): δ = 18.8 [Si(CH3)3]
NMR (25 °C, CD2Cl2, 282.38 MHz): δ = –77.51 (CF3) ppm. 29Si
INEPT NMR (25 °C, CD2Cl2, 49.70 MHz): δ = 19.8 [Si(CH3)3] ppm. IR (ATR, 25 °C, 32 scans): ν = 2958 (m), 2912 (m), 2870 (m),
˜
ppm. IR (ATR, 25 °C, 32 scans): ν = 2960 (m), 2906 (m), 2872 (m),
2103 (s), 1600 (w), 1478 (w), 1462 (w), 1405 (w), 1393 (m), 1350
(m), 1313 (m), 1256 (m), 1229 (m), 1196 (s), 1171 (m), 1149 (m),
1097 (m), 1023 (m), 960 (s), 908 (w), 882 (m), 840 (s), 768 (m), 748
(m), 739 (m), 689 (m), 678 (m), 630 (s), 586 (m), 573 (m), 541 (m)
˜
1598 (m), 1514 (m), 1496 (w), 1478 (m), 1469 (w), 1464 (w), 1436
(w), 1404 (w), 1393 (w), 1381 (w), 1364 (m), 1250 (s), 1222 (s), 1172
(s), 1100 (m), 1020 (s), 992 (m), 936 (w), 911 (m), 883 (m), 864 (s),
853 (m), 836 (m), 812 (m), 781 (m), 760 (m), 753 (m), 749 (m), 730 cm–1. Raman (250 mW, 25 °C, 1000 scans): ν = 3090 (1), 2995 (3),
˜
(m), 711 (m), 689 (m), 671 (m), 665 (m), 627 (s), 612 (s), 575 (s), 2964 (8), 2907 (10), 2783 (1), 2712 (1), 2094 (4), 1601 (4), 1547 (1),
542 (m) cm–1. Raman (75 mW, 25 °C, 500 scans): ν = 3059 (2), 2961
(8), 2907 (10), 2780 (1), 2712 (1), 1602 (3), 1464 (2), 1448 (2), 1415
1455 (2), 1408 (2), 1356 (1), 1290 (1), 1247 (1), 1229 (2), 1197 (2),
1173 (2), 1139 (3), 1098 (2), 1022 (1), 959 (1), 937 (1), 920 (1), 862
˜
830
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© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 822–832

Syntheses, Structure and Reactivity of Amino(azido)stibanes
(1), 816 (2), 767 (2), 740 (2), 690 (1), 634 (2), 570 (2), 542 (1), 481
(1), 423 (6), 323 (1), 255 (1), 182 (2) cm–1.
Acknowledgments
Financial support by the Deutsche Forschungsgemeinschaft
(DFG) (SCHU-1170/8-1) is gratefully acknowledged. We are in-
debted to BASF for the kind gift of chemicals.
Mes*N(SiMe3)SbCl(N3) (6): Me3SiCl (1 mmol, 0.11 g) in CH2Cl2
(3 mL) was added over a period of five minutes at –60 °C to a
stirred solution of Mes*N(SiMe3)Sb(N3)(OTf) (1 mmol, 0.65 g) in
CH2Cl2 (10 mL). The resulting colorless solution was warmed to
room temperature over a period of 20 min. The solvent was re-
moved under vacuum and the colorless residue was recrystallized
from n-hexane. Removal of solvent by syringe and drying yielded
0.38 g (0.72 mmol, 72%) of Mes*N(SiMe3)SbCl(N3) (6) as a color-
less crystalline solid; m.p. 120 °C (dec.). C21H38N4ClSbSi (531.84):
calcd. C 47.42, H 7.20, N 10.53; found C 47.56, H 7.20, N 10.38.
1H NMR (25 °C, CD2Cl2, 300.13 MHz): δ = 0.23 [s, 9 H,
Si(CH3)3], 1.28 (s, 9 H, p-tBu), 1.56 (s, 18 H, o-tBu), 7.45 (s, 2 H,
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CH) ppm. IR (ATR, 25 °C, 32 scans): ν = 3390 (vw), 3334 (vw),
˜
2956 (m), 2911 (m), 2859 (m), 2095 (s), 2078 (s), 1603 (m), 1484
(m), 1476 (m), 1462 (m), 1404 (m), 1391 (m), 1361 (m), 1311 (m),
1260 (s), 1254 (s), 1245 (m), 1213 (m), 1193 (m), 1170 (m), 1135
(m), 1099 (s), 1026 (w), 1019 (w), 942 (w), 923 (w), 908 (w), 896
(w), 883 (m), 851 (s), 833 (s), 769 (m), 750 (s), 731 (s), 686 (m), 671
(m), 644 (s), 634 (m), 605 (w), 580 (m), 569 (w), 540 (m) cm–1.
Compound 10: A solution of B(C6F5)3 (1 mmol, 0.52 g) in CH2Cl2
(5 mL) was added at –60 °C over a period of five minutes to a
stirred solution of Mes*N(SiMe3)Sb(N3)2 (1 mmol, 0.56 g) in
CH2Cl2 (10 mL). The resulting orange solution was stirred for
seven days at ambient temperature. The dark red solution was con-
centrated to about 2 mL and stored at +5 °C for several hours,
which resulted in the deposition of red crystals. Removal of solvent
by syringe and drying yielded 0.51 g (0.28 mmol, 56%) of N-(6-
imino-3,5-di-tert-butyl-cyclohexa-2,4-dienyl)iminomethylstibenium
azidotris(pentafluorphenyl)borate (10) as a red crystalline solid;
m.p. 173 °C (dec.). C66H48N10BF30Sb2 (1816.26): calcd. C 43.65, H
2.66, N 7.71; found C 43.32, H 2.69, N 7.50. 1H NMR (25 °C, [D8]-
THF, 300.13 MHz): δ = 1.16 (s, 6 H, Me), 1.28 (s, 18 H, tBu), 1.44
(s, 18 H, tBu), 6.77 [d, 1J(1H,1H) = 1.93 Hz, 2 H, CH], 7.03 [d,
1J(1H,1H) = 1.93 Hz, 2 H, CH], 11.81 (s, 2 H, NH) ppm. 13C{1H}
NMR (25 °C, [D8]THF, 75.48 MHz): δ = 12.77 (CH3), 28.81
[C(CH3)3], 30.64 [C(CH3)3], 37.46 [C(CH3)3] 117.12 (CH), 127.17
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(CH), 137.7 [m, 1J(13C,19F)
= 250 Hz, Ar–CF], 139.8 [m,
1J(13C,19F) = 243 Hz, Ar–CF], 149.3 [m, 1J(13C,19F) = 243 Hz, Ar–
CF], 151.50 (Ar–C), 164.84 (Ar–C), 166.22 (Ar–C), 169.16 (Ar–C)
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3
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3
= 22 Hz, 12 F, mCF], –163.53 [t, J(19F,19F) = 20.2 Hz, 6 F, p-CF],
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25 °C, 32 scans): ν = 3347 (m), 3071 (vw), 2972 (m), 2965 (m), 2912
˜
(w), 2879 (w), 2123 (s), 2003 (w), 1643 (m), 1624 (m), 1592 (w),
1565 (vw), 1556 (vw), 1514 (s), 1493 (m), 1461 (s), 1455 (s), 1403
(m), 1385 (m), 1372 (m), 1350 (m), 1333 (m), 1318 (m), 1275 (m),
1245 (m), 1199 (m), 1121 (m), 1091 (s), 1086 (s), 1026 (w), 1020
(w), 1012 (w), 972 (s), 927 (m), 910 (m), 890 (m), 862 (s), 838 (m),
824 (m), 802 (m), 767 (m), 756 (m), 745 (m), 733 (m), 670 (s), 665
(m), 648 (m), 617 (m), 604 (m), 593 (m), 574 (m), 534 (w) cm–1.
Raman (250 mW, 25 °C, 1500 scans): ν = 3085 (1), 2973 (2), 2922
˜
(2), 2811 (1), 2118 (1), 1624 (3), 1591 (2), 1560 (2), 1513 (10), 1400
(1), 1384 (1), 1335 (2), 1320 (1), 1267 (1), 1237 (1), 1199 (3), 1122
(1), 1086 (1), 1026 (1), 971 (1), 928 (1), 892 (1), 870 (1), 823 (1),
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Eur. J. Inorg. Chem. 2012, 822–832
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
831

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Received: October 12, 2011
Published Online: January 11, 2012
832
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© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2012, 822–832