Synthesis and characterization of 1,3-dihalogeno-2,4-bis(2,4,6-tri-tert- butylphenyl)-cyclo-1,3-distiba-2,4-diazanes, [X-Sb(μ-NR)]2 (X = F, Cl, Br, and I)

Article abstract of DOI:10.1002/ejic.201000885

The whole series of four-membered rings of the type [X-Sb(μ-NR)] ₂, containing alternating antimony(III) and nitrogen centers, have been synthesized and fully characterized (X = halogen, R = supermesityl = 2,4,6-tri-tert-butylphenyl = Mes*) and

Full text of DOI:10.1002/ejic.201000885

SHORT COMMUNICATION
DOI: 10.1002/ejic.201000885
Synthesis and Characterization of 1,3-Dihalogeno-2,4-bis(2,4,6-tri-tert-
butylphenyl)-cyclo-1,3-distiba-2,4-diazanes, [X–Sb(μ-NR)]2 (X = F, Cl, Br, and I)
Mathias Lehmann,[a] Axel Schulz,*[a,b] and Alexander Villinger[a]
Keywords: Heterocycles / Antimony / Halogens / Synthesis design / Structure elucidation
The whole series of four-membered rings of the type [X–
Sb(μ-NR)]2, containing alternating antimony(III) and nitrogen
centers, have been synthesized and fully characterized (X =
halogen, R = supermesityl = 2,4,6-tri-tert-butylphenyl =
Mes*) and represent rare examples of cyclo-distiba-diaz-
anes. The synthesis was carried out starting from the triflate
species [TfO–Sb(μ-NR)]2, which has been generated by uti-
lizing a new synthetic route. By Me3Si–OTf elimination, reac-
tions of [TfO–Sb(μ-NR)]2 with Me3Si–X yielded the halogen
compounds [X–Sb(μ-NR)]2 with the exception of the fluorine
species for which an iodine/fluorine exchange reaction with
AgF was successfully applied. The structures of all starting
materials, along the reaction pathway, and of all halogen
species were determined by single-crystal X-ray diffraction.
While for the compounds [X–Sb(μ-NR)]2 (X = OTf, Cl, Br, and
I), a molecular structure with no significant intermolecular
interactions was observed, the analogous fluorine species
[F–Sb(μ-NR)]2 displays Sb···F van der Waals interactions be-
tween the centrosymmetric dimers, which leads to a chain-
like structure in the crystal.
Burford and co-workers have studied the stabilities of the
monomeric species R–N=E(III)–X (E = P, As, Sb) with re-
spect to the corresponding dimers by using Mes* groups
(Mes* = 2,4,6-tri-tBu-phenyl) at the N atom and a chloro
Introduction
Four-membered rings of the type [X–Sb(μ-NR)]2, con-
taining alternating antimony(III) and nitrogen centers, are
known as cyclo-1,3-distiba(III)-2,4-diazanes (X = halogen,
R = organic group). Current interest in these ring systems
has increased in the recent past, mainly because such spe-
cies are good starting materials for polycyclic inorganic and
organometallic compounds.[1–3] The cyclo-distiba(III)-diaz-
ane [Cl–Sb(μ-NtBu)]2 was first generated by the reaction of
SbCl3 with LiN(SiMe3)tBu.[4] However, Stahl has shown
that [Cl–Sb(μ-NtBu)]2 can be prepared in a simple one-pot
synthesis, as displayed in Scheme 1, and the structure was
later determined by Chivers et al.[5,6] No other antimony
compounds of the type [X–Sb(μ-NR)]2 (X = halogen) have
been isolated to date.
–
or triflate (triflate = CF3SO3 = –OTf) substituent at the
pnictogen atom.[7] Monomeric Mes*–N=P–Cl was first re-
ported by Niecke et al.[8] While for the triflate derivative
both the monomer and the dimer were isolated, it was
shown that for the heavier arsenic and antimony analogs
only the dimers were obtained in the solid state.[7b] In con-
trast to the antimony species, it has been proven by NMR
studies that the arsenic dimer dissociates in solution, and a
1:1.7 equilibrium between the dimer and the monomer is
observed at ambient temperature.[9]
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 cations.[10] Particularly useful
for this purpose are dihalogeno-substituted species, since re-
action with AgX (X = weakly coordinating anion)[11] or
halogen abstraction by means of strong Lewis acids result
in the formation of salts containing cyclo-dipnictadiazen-
ium cations.[10] Here, we report on the synthesis and full
characterization of 1,3-dihalogeno-2,4-bis(2,4,6-tri-tert-but-
ylphenyl)-cyclo-1,3-distiba-2,4-diazanes [X–Sb(μ-NMes*)]2.
Structural data of the full halogen series (X = F, Cl, Br, and
I) are presented for the first time.
Scheme 1. One-pot synthesis of [Cl–Sb(μ-NtBu)]2.
[a] Universität Rostock, Institut für Chemie, Abteilung
Anorganische Chemie,
Albert-Einstein-Strasse 3a, 18059 Rostock, Germany
E-mail: axel.schulz@uni-rostock.de
Results and Discussion
[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.201000885.
Depending on the reaction conditions and stoichiometry,
the reaction of Mes*–NH2 and SbCl3 in the presence of
a base such as Et3N, DBU (1,8-diazabicyclo[5.4.0]undec-7-
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M. Lehmann, A. Schulz, A. Villinger
SHORT COMMUNICATION
ene), and Mes*–NH2 etc. does not result in the exclusive to the deposition of colorless crystals of Mes*N(SiMe3)-
generation of cyclo-distiba(III)-diazane, [Cl–Sb(μ- SbCl2 (2) in good yields (86%) (Scheme 3). Compound 2
a
NMes*)]2 (F), but instead mixtures of mono- and disubsti- is thermally stable up to 116 °C (melting point) and then
tuted products (A and B) along with traces of the desired decomposes at this temperature. For this reason, it was not
cyclo-distiba(III)-diazanes (F) were observed as illustrated possible to generate [Cl–Sb(μ-NMes*)]2 by means of base
in Scheme 2.[7b,12] With a large excess of Mes*–NH2, the or thermally induced Me3Si–Cl elimination.
triply substituted species C is formed. Hence, a new
straightforward synthetic route to cyclo-distiba(III)-diaz-
anes had to be found. The idea was to use the elimination
of trimethylsilyl trifluoromethanesulfonate, Me3Si–OTf, as
driving force to introduce a halogen (X) according to R2Sb–
OTf + Me3Si–X Ǟ Me3Si–OTf + R2Sb–X. For this reason
Scheme 3. Synthesis of 2 and 3.
[TfO–Sb(μ-NMes*)]2 had to be isolated in good yields.
However, the synthesis [addition of AgOTf to a mixture of
SbCl3 and LiN(H)Mes*], published by the Burford
group,[7b] results in the formation of a complex mixture,
from which [TfO–Sb(μ-NMes*)]2 was isolated in small
yields (14%), and thus is not suitable to for the develop-
ment of this chemistry.
The second reaction step involves the addition of
Mes*N(SiMe3)SbCl2 (2) to a stirred suspension of silver
triflate AgOTf in CH2Cl2 at low temperature (–80 °C). By
allowing this mixture to warm up to 0 °C for 30 min and to
crystallize at –25 °C after concentration, crystalline 3 (95%,
Scheme 3) was afforded. While 3 is thermally stable as a
solid up to 90 °C (dec.), it slowly eliminates Me3Si–OTf at
slightly elevated temperatures (35 °C) in CH2Cl2, which re-
sults in the formation of dimeric [TfO–Sb(μ-NMes*)]2 (4)
in very good yields (94%) (Scheme 4). The intramolecular
elimination of Me3Si–OTf is easily followed by H or 19F
1
NMR spectroscopy.
Scheme 4. Synthesis of 4.
The major advantage of this three-step procedure is that
all three reaction products (2, 3, and 4) along the reaction
sequence can be purified easily and isolated in bulk as well
as in good yields. All compounds have been fully charac-
terized. Compounds 2 and 3 are stable for long periods
when stored in a sealed tube and kept at low temperatures.
As a consequence, [TfO–Sb(μ-NMes*)]2 (4) can also be pre-
pared in bulk and as a very pure crystalline orange solid,
which allows follow-up chemistry. Interestingly, triflate-sub-
stituted cyclo-distiba(III)-diazane 4 was found to decom-
pose at 187 °C, which is in contrast to the published decom-
position temperature, Tdec Ͼ 360 °C.[7b]
Scheme 2. Possible reaction products in the reaction of Mes*–NH2
and SbCl3 in the presence of a base.
Synthesis of [TfO–Sb(μ-NMes*)]2
Synthesis of [X–Sb(μ-NMes*)]2 (X = F, Cl, Br, and I)
The halogen compounds [X–Sb(μ-NMes*)]2 (X = Cl, Br,
Our new three-step synthesis of [TfO–Sb(μ-NMes*)]2
starts from N-(2,4,6-tri-tert-butyl-phenyl)-N-(trimethylsilyl)- I) are prepared in high yields (Cl: 86, Br: 91, I: 95%) by
amine [Mes*N(H)SiMe3, 1], which is easily obtained from reaction of 4 with Me3Si–X in CH2Cl2 at ambient tempera-
Mes*–NH2, nBuLi, and Me3Si–Cl.[13] Treatment of a tolu- ture for 30 min. Removal of the solvent and Me3Si–OTf,
ene solution of 1 with nBuLi and SbCl3 resulted in the for- followed by washing with n-hexane, afforded crystalline sol-
mation of a brownish suspension. Filtration and removal of ids (Scheme 5). The fluorine-substituted species was pre-
the solvent followed by re-crystallization from n-hexane led pared by an I/F exchange reaction by means of AgF, since
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[X–Sb(μ-NR)]2 (X = F, Cl, Br, and I)
the analogous reaction with Me3Si–F could not be applied the trigonal-pyramidal antimony atom, the central nitrogen
because of the very large Si–F bond dissociation energy. To atom sits in a trigonal-planar environment (ΣϽN = 359.2°)
a stirred suspension of [I–Sb(μ-NMes*)]2 in THF was with an Si–N single bond of 1.737(3) and N–Sb bond of
added finely powdered AgF at ambient temperature. Re- 2.056(3) Å [Σrcov(Si–N)
= 1.87 and Σrcov(Sb–N) =
moval of the solvent and washing with n-hexane, followed 2.11 Å].[14] Since the phenyl ring of the Mes* group lies or-
by extraction with THF, afforded [F–Sb(μ-NMes*)]2 in thogonal to the plane composed of Si, N, and Sb atoms,
good yields (78%).
there is no interaction between the nitrogen lone pair
(which is localized on a p atomic orbital) and the π system
of the phenyl ring (Figure 1). A look along the Sb–Si axis
displays a staggered conformation for the SbCl2/SiMe3
groups. The Sb–Cl bond lengths between 2.359–2.369 Å are
in the range expected for a typical Sb–Cl single bond
[Σrcov(Sb–Cl) = 2.4 Å].[14]
Scheme 5. Synthesis of 5Cl (X = Cl), 5Br (X = Br) and 5I (X = I).
All halogen compounds [X–Sb(μ-NMes*)]2 (5F: X = F,
5Cl: X = Cl, 5Br: X = Br, 5I: X = I) are moisture sensitive
but can be handled in air for a short period. They are easily
prepared in bulk and are stable under argon atmosphere
over a long period when stored in a sealed tube at ambient
temperature or in common organic solvents. All species are
thermally stable up to over 170 °C (Tdec. 5F: 240, 5Cl: 172,
5Br: 173, 5I: 173 °C). It should be noted that the color
changes from pale yellow for 5F through to yellow for 5Cl
to orange for 5Br and 5I.
Figure 1. ORTEP drawing of the molecular structure of 2 in the
crystal. Thermal ellipsoids with 50% probability at 173 K (hydro-
gen atoms omitted for clarity). Selected bond lengths [Å] and
angles [°]: Sb1–N 2.056(3), Sb1–Cl2 2.359(2), Sb1–Cl1 2.369(2),
Si1–N 1.737(3), N–C1 1.476(4); N–Sb1–Cl2 99.18(7), N–Sb1–Cl1
103.58(7), Cl2–Sb1–Cl1 90.92(5), C1–N–Sb 105.3(2), C1–N–Si
127.2(2), Si–N–Sb 127.42(1).
The Raman data of all species considered show sharp
bands in the expected region 5F: 549/490, 5Cl: 308/297,
5Br: 252/234/211, 5I: 169/148/122 cm–1, which can be as-
signed to the stretching frequencies νs,Sb–X and νas,Sb–X
,
respectively. Especially in the case of 5Br and 5I, the asym-
metric stretching mode combines strongly with Sb–N defor-
mation modes. Only very small deviations are observed in
Mes*N(SiMe3)–Sb(OTf)2 (3)
1
the H and 13C NMR spectra.
Compound 3 crystallizes in the space group P21/n with
four molecules per unit cell and one independent molecule
per asymmetric unit (Figure 2). Upon exchanging Cl by
OTf, the major structural features do not change much. The
primary coordination sphere consists again of a trigonal-
planar nitrogen atom and a pyramidal (O2,N)Sb core, how-
X-ray Structure Analysis
The solid-state structures of the starting materials 2, 3,
and 4 are displayed in Figures 1, 2, and 4, respectively,
along with selected bond lengths and angles. The structure
of 4 is already known,[7b] but for comparison, we would
like to include our structural data into the discussion. The
molecular structures of halogen compounds [X–Sb(μ-
NMes*)] are shown in Figure 5. Selected bond lengths and
angles for 4 and 5X are summarized in Table 1. Crystallo-
graphic details for all compounds are given in Tables 2 and
3. X-ray quality crystals of all species considered were se-
lected in Kel-F-oil (Riedel deHaen) or Fomblin YR-1800
(Alfa Aesar) at ambient temperatures. All samples were co-
oled to 173(2) K during the measurement.
Mes*N(SiMe3)–SbCl2 (2)
Figure 2. ORTEP drawing of the molecular structure of 3 in the
crystal. Thermal ellipsoids with 50% probability at 173 K (hydro-
gen atoms omitted for clarity). Selected bond lengths [Å] and
angles [°]: Sb–N1 1.966(1), Sb–O1 2.089(1), Sb–O4 2.098(1), N1–
C1 1.473(2), N1–Si 1.798(1), N1–Sb–O1 92.42(6); N1–Sb–O4
94.22(4), O1–Sb–O4 83.50(4), C1–N1–Si1 117.43(7), C1–N1–Sb1
113.42(8), Si1–N1–Sb1 128.76(6), S1–O1–Sb1 124.93(6), S2–O4–
Compound 2 (Figure 1) crystallizes in the monoclinic
space group P21/n with four formula units per cell. The
structure consists of separated Mes*N(SiMe3)–SbCl2 mole-
cules with no significant intermolecular contacts. Only
weak Cl···HC interactions are found. The positions of the
SbCl2 and SiMe3 moieties are disordered. In contrast to Sb1 123.41(6).
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M. Lehmann, A. Schulz, A. Villinger
SHORT COMMUNICATION
ever, with two secondary intermolecular interactions be- (Figure 5) display trans-substituted centrosymmetric dimers
tween the antimony and O3Ј and O5Ј atoms of an adjacent with a planar Sb2N2 core protected by two bulky Mes*
molecule, which forms a centrosymmetric dimer. The dis- groups. Astonishingly, the metrical parameters of the Sb2N2
tances Sb···O3Ј and Sb···O5Ј of 3.314 and 3.379 Å, respec- core such as the Sb···Sb and Sb–N distances or the N–Sb–
tively, lie within the range of weak Sb···O van der Waals NЈ and Sb–N–SbЈ angles (Table 1) do not change along the
interactions [cf. ΣrvdW(Sb–O) = 3.7 Å].[14] Moreover, intra- series 5F, 5Cl, 5Br, and 5I and are in the same range found
molecular Sb···O interactions are also found between for the triflate species 4. Two slightly different Sb–N bond
Sb···O3 [3.295(2) Å] and Sb···O5 [3.200(2) Å], which finally lengths between 2.016 and 2.055 Å are found in the ex-
lead to a distorted Sb2O4 octahedron (Figure 3). The Sb–O pected range for a typical single bond {cf. Σrcov(Sb–N) =
bond lengths are 2.089(1) (Sb–O1) and 2.098(1) Å (Sb–O4). 2.11 Å, Table 1, 2.009(7)–2.022(7) Å in [Cl–Sb(μ-
While the Si–N bond length of 1.798(1) Å is slightly longer NtBu)]2}.[6,14] The Sb···Sb distances between 3.11–3.16 Å
than that in 2, the Sb–N distance decreases considerably are only slightly longer than the sum of the covalent radii
[1.966(1) vs. 2.056(3) Å].
(2.82 Å) but significantly shorter than the sum of the van
der Waals radii (4.4 Å).[14] Thus, strong van der Waals inter-
Figure 3. View of the centrosymmetric dimer 3 formed by intermo-
lecular Sb···O contacts. Together with intramolecular Sb···O inter-
actions, a distorted Sb2O4 octahedron is observed.
[X–Sb(μ-NMes*)]2 (X = OTf, F, Cl, Br, and I)
While compounds 4, 5F and 5Cl crystallize in the mono-
clinic space groups P21/n and P21/c, with four molecules
¯
per unit cell, the triclinic space group P1 is found for 5Br
and 5I with two molecules in the unit cell. Noteworthy, only
5Br crystallizes with one (disordered) solvent molecule,
CH2Cl2, per unit cell.
The molecular structures of the triflate derivative of [X–
Sb(μ-NMes*)] (Figure 4) and all the halogen derivatives
Figure 4. ORTEP drawing of the molecular structure of 4 in the
crystal. Thermal ellipsoids with 50% probability at 173 K (hydro-
gen atoms omitted for clarity). See the text for values of selected
metrical parameters.
Figure 5. ORTEP drawing of the molecular structures of 5F, 5Cl,
5Br, and 5I in the crystal. Thermal ellipsoids with 50% probability
at 173 K (hydrogen atoms omitted for clarity). See Table 1 for val-
ues of selected metrical parameters.
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[X–Sb(μ-NR)]2 (X = F, Cl, Br, and I)
Table 1. Selected structural data of 4 and 5X (X = F, Cl, Br, I); distances in Å, angles in °.
4
5F
5Cl
5Br
5I
Sb–X
Sb–N
Sb–NЈ
C–N
Sb···Sb
N–Sb–NЈ
Sb–N–SbЈ
X–Sb–N
X–Sb–NЈ
C–N–Sb
C–N–SbЈ
2.139(2)
2.016(3)
2.022(3)
1.449(4)
3.113(1)
79.1(1)
100.9(1)
90.3(1)
96.8(1)
1.974(1)
2.038(2)
2.055(2)
1.436(2)
3.154(1)
79.18(7)
100.82(7)
91.31(7)
100.31(7)
113.29(1)
140.64(1)
2.4143(6)
2.038(1)
2.052(1)
1.442(1)
3.148(5)
79.36(4)
100.64(4)
95.85(3)
102.11(3)
114.59(7)
142.58(8)
2.565(1)
2.034(2)
2.052(2)
1.441(2)
3.148(1)
79.18(5)
100.82(5)
99.78(4)
104.04(5)
116.6(1)
140.6(1)
2.797(1)
2.039(2)
2.054(2)
1.432(2)
3.157(1)
79.08(7)
100.92(7)
101.59(4)
107.83(4)
117.1(1)
139.4(1)
114.6(2)
141.1(2)
actions across the ring can be assumed. Similar structural (173) ≈ 5I (173 °C). The largest decomposition temperature
features are found in [X–Sb(μ-NtBu)]2 (X = OTf, N3, is seen for 5F, the species with the strongest intermolecular
Cl)[5,6]
interactions.
As expected the halogen–antimony bond lengths increase
in the order, 5F [1.974(1), cf. Σrcov(Sb–F) = 2.05 Å] Ͻ 5Cl
[2.4143(6), cf. Σrcov(Sb–Cl) = 2.40] Ͻ 5Br [2.565(1), cf.
Σrcov(Sb–Br) = 2.55 Å] and 5I [2.797(1), cf. Σrcov(Sb–I) =
2.74 Å],[14] as well as the X–Sb–N angles, in accord with the
VSEPR model. The two antimony atoms adopt a trigonal-
pyramidal geometry with very small N–Sb–N angles of ca.
79° and Sb–N–Sb angles of ca. 100.1°. In contrast to spe-
cies 2 and 3, the nitrogen atoms also sit in a slightly trigo-
nal-pyramidal environment with the two Mes* groups in a
trans position.
Only weak CH···X and CH···Sb interactions are found
between the [X–Sb(μ-NMes*)] dimers with one exception.
In 5F, these dimers interact further through a weak sym-
metric interaction involving both fluorine atoms
[d(SbЈ···FЈЈ) = 2.706(2) Å; cf. ΣrvdW(Sb···F) = 3.7 Å],[14] as
shown in Figure 6; if these interactions are considered, the
overall Sb coordination geometry is strongly distorted te-
tragonal. Hence, the crystal structure of 5F can be de-
scribed as a weakly bound polymer of strongly bound cen-
trosymmetric dimers. Such intermolecular interactions can
be assumed to be responsible for the observed trend of the
thermal stability, 5F (240) ϾϾ 4 (187) Ͼ 5Cl (172) ≈ 5Br
Conclusions
The reaction of Mes*N(H)SiMe3 with SbCl3 in the pres-
ence of 1 equiv. nBuLi has been studied, which results in the
formation of Mes*N(SiMe3)SbCl2 in high yields. Hitherto
unknown Mes*N(SiMe3)SbCl2 represents a very good pre-
cursor for further synthesis. For example, reaction of
Mes*N(SiMe3)SbCl2 with 2 equiv. AgOTf gave Mes*N-
(SiMe3)Sb(OTf)2, which eliminates thermally Me3Si–OTf to
form [TfO–Sb(μ-NMes*)]2. This synthetic route represents
a novel pathway to [TfO–Sb(μ-NMes*)]2 and the hitherto
unknown halogen species, [X–Sb(μ-NMes*)]2, which can
easily be obtained by treatment of [TfO–Sb(μ-NMes*)]2
with Me3Si–X (X = Cl, Br, I) where Me3Si–OTf is elimin-
ated . The fluorine-substituted species [F–Sb(μ-NMes*)]2 is
generated by the reaction of [I–Sb(μ-NMes*)]2 with AgF.
Thus, it was possible for the first time to discuss the chemi-
cal and physical properties, as well as structural trends, for
the whole halogen series.
Experimental Section
General Information: All manipulations were carried out under
oxygen- and moisture-free conditions under argon by using stan-
dard Schlenk or drybox techniques. Dichloromethane was purified
according to a literature procedure,[15] dried with P4O10, and freshly
distilled prior to use. Tetrahydrofuran (THF), benzene, toluene,
and ethyl ether were dried with Na/benzophenone and freshly dis-
tilled prior to use. N-hexane was dried with Na/benzophenone/tet-
raglyme and freshly distilled prior to use. Mes*N(H)SiMe3 was pre-
pared as described in a literature procedure.[13]
1
NMR: 13C{1H}, 13C DEPT, H, 19F{1H}, and 29Si INEPT NMR
spectra were obtained on a Bruker AVANCE 300 spectrometer and
were referenced internally to the deuterated solvent (13C, CD2Cl2:
δreference = 54 ppm, C6D6: δreference = 128.0 ppm) or to protic impu-
rities in the deuterated solvent (1H, CDHCl2: δreference = 5.31 ppm,
C6D5H: δreference = 7.16 ppm). CD2Cl2 was dried with P4O10, and
C6D6 was dried with Na/benzophenone. IR: A Nicolet 380 FTIR
with a Smart Orbit ATR device was used. Raman: A Bruker VER-
TEX 70 FTIR with RAM II FT-Raman module, equipped with a
Figure 6. View of the molecular structure of 5F showing the chains
of dimers.
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M. Lehmann, A. Schulz, A. Villinger
SHORT COMMUNICATION
Nd:YAG laser (1064 nm) was used. CHN Analyses: An Analysator
Flash EA 1112 from Thermo Quest or C/H/N/S-Mikronalysator
TruSpec-932 from Leco was used. Melting Points: These are uncor-
X-ray Structure Determination: X-ray quality crystals were selected
in Fomblin YR-1800 perfluoroether (Alfa Aesar) at ambient tem-
peratures. The samples were cooled to 173(2) K during measure-
rected (EZ-Melt, Stanford Research Systems). Heating-rate 20 °C/ ment. The data were collected on a Bruker Apex Kappa-II CCD
min (clearing-points are reported). MS: A Finnigan MAT 95-XP
from Thermo Electron was used.
diffractometer by using graphite-monochromated Mo-Kα radiation
(λ = 0.71073). The structures were solved by direct methods
Table 2. Crystallographic details of 2, 3, and 4.
2
3
4
Formula
C21H38Cl2NSbSi
525.26
colorless
monoclinic
P21/n
C23H38F6NO6S2SbSi
752.5
colorless
monoclinic
P21/n
C36H58F6N2O6S2Sb2
1060.48
yellow
monoclinic
P21/n
Fw [gmol–1]
Color
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
12.767(6)
12.816(7)
15.170(7)
90
14.090(8)
16.142(9)
14.472(8)
90
11.453(6)
16.477(8)
11.961(6)
90
β [°]
92.413(13)
90
2480(2)
4
1.407
1.382
90.318(11)
90
3292(3)
4
1.518
1.070
90.36(2)
90
2257(2)
2
1.560
1.358
γ [°]
V [Å3]
Z
ρcalcd. [gcm–3]
μ [mm–1]
T [K]
173(2)
24981
6963
5600
0.0238
1080
173(2)
83570
11713
9679
0.0302
1528
173(2)
39701
5969
5214
0.0341
1072
Measured reflections
Independent reflections
Reflections with IϾ2σ(I)
Rint
F(000)
R1 {R[IϾ2σ(I)]}
0.0457
0.1109
1.093
0.0225
0.0564
1.018
0.0330
0.0746
1.123
wR2 (F2)
GooF
No. parameters
CCDC
313
794567
373
794568
263
794569
Table 3. Crystallographic details of 5X (X = F, Cl, Br, I).
5F
5Cl
C36H58Cl2N2Sb2
833.24
yellow
monoclinic
P21/c
5Br
5I
Formula
C36H58F2N2Sb2
800.34
colorless
monoclinic
P21/n
C36H58Br2N2Sb2, C2H4Cl4
C36H58I2N2Sb2
Fw [gmol–1]
1092.02
orange
triclinic
1016.14
orange
triclinic
Color
Crystal system
¯
P1
¯
P1
Space group
a [Å]
b [Å]
c [Å]
α [°]
β [°]
6.150(3)
29.67(2)
10.034(5)
90
100.67(2)
90
1800(2)
2
1.477
15.325(3)
10.702(2)
12.134(2)
90
100.03(3)
90
1959.7(7)
2
1.412
10.079(5)
10.588(6)
13.116(6)
77.51(2)
69.55(2)
61.62(2)
1152(1)
1
8.138(3)
11.003(4)
11.334(4)
76.70(1)
85.64(2)
89.27(2)
984.8(7)
1
γ [°]
V [Å3]
Z
ρcalcd. [gcm–3]
1.574
3.166
1.713
2.964
μ [mm–1]
1.537
1.540
T [K]
173(2)
24836
6423
4766
0.0356
816
173(2)
40560
8585
7068
0.0266
848
173(2)
29271
8289
6932
0.0275
544
173(2)
26036
7081
5668
0.0323
496
Measured reflections
Independent reflections
Reflections with IϾ2σ(I)
Rint
F(000)
R1 (R[IϾ2σ(I)])
0.0319
0.0602
1.020
0.0235
0.0503
1.010
0.0252
0.0583
1.043
0.0260
0.0540
1.018
wR2 (F2)
GooF
No. parameters
CCDC
199
794573
199
794570
248
794571
199
794572
5506
www.eurjic.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 5501–5508

[X–Sb(μ-NR)]2 (X = F, Cl, Br, and I)
(SHELXS-97)[16] and refined by full-matrix least-squares pro- (7), 1146 (5), 1116 (2), 1025 (2), 922 (2), 884 (1), 863 (2), 823 (5),
cedures (SHELXL-97)[17] Semiempirical absorption corrections
were applied (SADABS).[18] All non-hydrogen atoms were refined
anisotropically, hydrogen atoms were included in the refinement at
calculated positions by using a riding model. The crystallographic
details of the compounds are presented in Tables 2 and 3. The
CCDC numbers refer to 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.
788 (2), 761 (2), 616 (1), 591 (2), 566 (3), 549 (2), 490 (3), 299 (2),
257 (4), 224 (3), 163 (3), 147 (6), 125 (4), 110 (4) cm–1. MS (CI
positiv): m/z (%) = 206 (18) [Mes*NH3 – tBu]+, 262 (100)
[Mes*NH3]+, 382 (7) [Mes*NSb]+, 395 (6) [Mes*N(H)SbN]+, 642
(Ͻ1) [M –SbF2]+, 781 (3) [M –F]+, 800 (Ͻ 1) [M]+.
[Cl–Sb(μ-NMes*)]2 (5Cl): To a stirred suspension of 4 (1.06 g,
1 mmol) in CH2Cl2 (10 mL) was added Me3SiCl (0.24 g, 2.2 mmol)
in CH2Cl2 (5 mL) over a period of 5 min at ambient temperature.
After stirring for 30 min, the solvent was removed from the clear
yellow solution, the yellow residue was dried for 2 h in vacuo and
washed three times with n-hexane (2 mL). Drying of the residue in
vacuo yielded 0.72 g (0.86 mmol, 86%) of 5Cl as a yellow crystal-
line solid. Mp. 172 °C (dec.). C36H58Cl2N2Sb2 (833.24): calcd. C
51.89, H 7.02, N 3.36; found C 51.93, H 7.03, N 3.11. 1H NMR
(25 °C, CD2Cl2, 300.13 MHz): 1.29 (s, 18 H, p-tBu), 1.63 (s, 36 H,
o-tBu), 7.33 (s, 4 H, CH) ppm. 13C{1H} NMR (25 °C, CD2Cl2,
75.48 MHz): 31.80 [C(CH3)3], 35.79 [C(CH3)3], 36.32 [C(CH3)3],
38.75 [C(CH3)3], 124.13 (CH), 143.14 (Ar-C), 144.88 (Ar-C), 146.64
[TfO–Sb(μ-NMes*)]2 (4): A solution of Mes*N(SiMe3)–Sb(OTf)2
(2) (1.51 g, 2 mmol) in CH2Cl2 (25 mL) was warmed at 35 °C for
36 h, which resulted in the deposition of orange crystals. The dark
orange supernatant was transferred by syringe, concentrated to ap-
proximately 5 mL, and stored at –25 °C for several hours, which
again resulted in the deposition of orange crystals. Drying of the
combined crystalline fractions in vacuo yielded 1.01 g (0.94 mmol,
94%) of
4
as orange crystals. Mp. 187 °C (dec.).
C36H58F6N2O6S2Sb2 (1060.48): calcd. C 43.04, H 5.51, N 2.64;
found C 43.31, H 5.91, N 2.48. 1H NMR (25 °C, CD2Cl2,
300.13 MHz): 1.29 (s, 18 H, p-tBu), 1.64 (s, 36 H, o-tBu), 7.41 (s,
4 H, CH) ppm. 13C{1H} NMR (25 °C, CD2Cl2, 75.48 MHz): 31.57
[p-C(CH3)3], 34.94 [p-C(CH3)3], 35.49 [o-C(CH3)3], 37.39 [o-
C(CH3)3], 118.97 (q, CF3), 124.68 (CH), 140.59 (Ar-C), 146.34 (Ar-
C), 147.39 (Ar-C) ppm. 19F {1H} NMR (25 °C, CD2Cl2,
(Ar-C) ppm. IR [ATR, 25 °C, 32 scans ]: ν = 3079 (vw), 3008 (w),
˜
2960 (s), 2949 (s), 2937 (s), 2902 (m), 2867 (m), 1596 (w), 1472 (w),
1463 (w), 1457 (w), 1434 (w), 1409 (m), 1394 (m), 1360 (s), 1289
(w), 1261 (w), 1241 (m), 1208 (s), 1198 (s), 1174 (s), 1140 (w), 1102
(s), 1026 (w), 921 (w), 912 (w), 877 (m), 836 (s), 818 (w), 781 (s),
749 (m), 690 (s), 646 (w), 624 (s), 585 (m), 563 (w), 535 (m) cm–1.
Raman [250 mW, 25 °C, 552 scans]: 3078 (1), 2965 (10), 2920 (8),
2903 (9), 2776 (1), 2707 (2), 1597 (7), 1465 (3), 1450 (3), 1412 (3),
1392 (2), 1361 (1), 1293 (3), 1246 (2), 1215 (6), 1203 (5), 1188 (7),
1142 (6), 1113 (2), 1026 (1), 923 (2), 860 (2), 823 (4), 782 (1), 758
(4), 618 (1), 563 (2), 538 (1), 477 (1), 390 (1), 308 (5), 297 (9), 235
(8), 159 (2), 142 (3), 132 (3), 110 (3) cm–1.
282.38 MHz): –78.03 ppm. IR (ATR, 25 °C, 32 scans): ν = 3024
˜
(vw), 2964 (m), 2944 (m), 2914 (m), 2872 (m), 1593 (w), 1479 (w),
1462 (w), 1435 (vw), 1414 (w), 1394 (m), 1360 (s), 1297 (w), 1281
(w), 1265 (w), 1232 (m), 1188 (s), 1149 (s), 1100 (m), 1026 (m), 933
(s), 884 (m), 878 (m), 841 (s), 818 (w), 779 (s), 766 (w), 751 (m),
701 (m), 667 (vw), 650 (w), 625 (s), 587 (s), 572 (m), 543 (m), 532
(s) cm–1. Raman [100 mW, 25 °C, 800 scans]: 3027 (2), 2968 (9),
2940 (8), 2908 (10), 2782 (2), 2755 (2), 2710 (2), 1594 (8), 1463 (4),
1416 (6), 1393 (3), 1364 (3), 1287 (4), 1268 (2), 1236 (5), 1215 (10),
1203 (8), 1185 (7), 1145 (8), 1113 (3), 1013 (1), 944 (3), 922 (2), 867
(3), 820 (4), 779 (2), 766 (3), 619 (2), 593 (1), 564 (3), 547 (2), 538
(2), 509 (2), 475 (2), 410 (3), 364 (2), 344 (2), 317 (2), 301 (2), 245
(8), 214 (2), 160 (2), 148 (2), 130 (2) cm–1.
[Br–Sb(μ-NMes*)]2 (5Br): To a stirred suspension of 4 (1.06 g,
1 mmol) in CH2Cl2 (10 mL) Me3SiBr was added (0.34 g, 2.2 mmol)
in CH2Cl2 (5 mL) over a period of 5 min at ambient temperature.
After stirring for 30 min, the solvent was removed from the orange
solution and the orange residue was dried for 2 h in vacuo and
washed three times with n-hexane (2 mL). Drying of the residue in
vacuo yielded 0.84 g (0.91 mmol, 91%) of 5Br as an orange crystal-
line solid. Mp. 173 °C (dec.). C36H58Br2N2Sb2 (922.19): calcd. C
46.89, H 6.34, N 3.04; found C 46.86, H 6.45, N 2.65. 1H NMR
(25 °C, CD2Cl2, 300.13 MHz): 1.28 (s, 18 H, p-tBu), 1.61 (s, 36 H,
o-tBu), 7.31 (s, 4 H, CH) ppm. 13C{1H} NMR (25 °C, CD2Cl2,
75.48 MHz): 31.74 [C(CH3)3], 34.80 [C(CH3)3], 35.79 [C(CH3)3],
37.39 [C(CH3)3], 124.15 (CH), 143.17 (Ar-C), 144.88 (Ar-C), 146.35
[F–Sb(μ-NMes*)]2 (5F): To
a stirred suspension of [I–Sb(μ-
NMes*)]2 (5I) (1.02 g, 1 mmol) in THF (25 mL), finely powdered
AgF (0.26 g, 2 mmol) was added in one portion, and the resulting
red supension was stirred for 8 h at ambient temperatures. The sol-
vent was removed, and the residue was dried in vacuo for 30 min.
The resulting grey residue was washed three times with n-hexane
(5 mL) and was then extracted four times with THF (30 mL), which
resulted in a pale yellow suspension. The solvent was removed, and
the pale yellow residue was dried in vacuo for 6 h, which yielded
0.62 g (0.78 mmol, 78%) of 5F as a pale yellow crystalline solid.
Mp. 240 °C (dec.). C36H58F2N2Sb2 (800.34): calcd. C 54.02, H 7.30,
N 3.50; found C 53.48, H 7.46, N 3.42. 1H NMR (25 °C, C6D6,
300.13 MHz): 1.32 (s, 18 H, p-tBu), 1.79 (s, 36 H, o-tBu), 7.59 (s,
4 H, CH) ppm. 13C{1H} NMR (25 °C, C6D6, 75.48 MHz): 31.63
[C(CH3)3], 34.48 [C(CH3)3], 35.21 [C(CH3)3], 37.62 [C(CH3)3],
123.67 (CH), 144.81 (Ar-C), 148.05 (Ar-C) ppm. 19F {1H} NMR
(25 °C, C6D6, 282.38 MHz): –84.25 ppm. IR [ATR, 25 °C, 32
(Ar-C) ppm. IR (ATR, 25 °C, 32 scans): ν = 3006 (w), 2950 (s),
˜
2936 (s), 2903 (m), 2868 (m), 1594 (w), 1470 (w), 1463 (w), 1455
(w), 1436 (w), 1408 (m), 1404 (m), 1391 (m), 1360 (s), 1283 (w),
1257 (m), 1238 (m), 1208 (m), 1196 (m), 1172 (s), 1140 (w), 1103
(s), 1021 (m), 982 (w), 945 (vw), 934 (vw), 919 (w), 910 (w), 879
(m), 836 (s), 817 (m), 783 (s), 749 (m), 686 (s), 648 (w), 623 (s), 589
(m), 564 (w), 536 (m) cm–1. Raman [100 mW, 25 °C, 544 scans]:
3112 (5), 2963 (7), 2915 (7), 2777 (1), 2707 (1), 1596 (7), 1447 (2),
1412 (3), 1392 (2), 1361 (2), 1285 (3), 1215 (6), 1186 (7), 1143 (5),
1113 (2), 923 (1), 861 (2), 822 (3), 783 (1), 759 (2), 618 (1), 586 (1),
564 (2), 541 (2), 289 (1), 252 (2), 234 (5), 211 (10), 163 (1), 138 (2)
cm–1.
scans]: ν = 3085 (vw), 3017 (w), 2947 (s), 2918 (m), 2866 (m), 1597
˜
(w), 1477 (w), 1454 (w), 1447 (w), 1402 (m), 1389 (m), 1358 (m),
1289 (w), 1261 (w), 1239 (m), 1204 (s), 1180 (s), 1175 (s), 1140 (m),
1105 (s), 1022 (vw), 984 (vw), 932 (vw), 910 (w), 875 (m), 839 (s),
819 (w), 784 (s), 750 (m), 681 (s), 647 (w), 627 (s), 592 (m), 563
[I–Sb(μ-NMes*)]2 (5I): To a stirred suspension of 4 (1.06 g,
1 mmol) in CH2Cl2 (10 mL) was added Me3SiI (0.44 g, 2.2 mmol)
in CH2Cl2 (5 mL) over a period of 5 min at ambient temperature.
(w), 538 (m) cm–1. Raman [100 mW, 25 °C, 800 scans] 3082 (2), After stirring for 30 min, the solvent was removed from the orange
3019 (2), 2971 (9), 2951 (10), 2922 (10), 2907 (9), 2775 (2), 2706
(2), 1601 (7), 1449 (4), 1414 (3), 1362 (2), 1293 (3), 1220 (6), 1191
suspension and the orange residue was dried for 2 h in vacuo and
washed three times with n-hexane (2 mL). Drying in vacuo yielded
Eur. J. Inorg. Chem. 2010, 5501–5508
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
5507

M. Lehmann, A. Schulz, A. Villinger
SHORT COMMUNICATION
Am. Chem. Soc. 2002, 124, 14012–14013; b) N. Burford, T. S.
Cameron, C. L. B. Macdonald, K. N. Robertson, R. Schurko,
D. Walsh, Inorg. Chem. 2005, 44, 8058–8064; c) N. Burford,
C. A. Dyker, A. D. Phillips, H. A. Spinney, A. Deckon, R. Mc-
Donald, P. J. Ragogna, A. L. Rheingold, Inorg. Chem. 2004,
43, 7502–7507; d) N. Burford, K. D. Conroy, J. C. Landry, P. J.
Ragogna, M. J. Ferguson, R. McDonald, Inorg. Chem. 2004,
43, 8245–8251.
0.97 g (0.95 mmol, 95%) of 5I as an orange crystalline solid. Mp.
173 °C (dec.). C36H58I2N2Sb2 (1016.14): calcd. C 42.55, H 5.75, N
2.76; found C 42.18, H 5.63, N 2.53. 1H NMR (25 °C, CD2Cl2,
300.13 MHz): 1.27 (s, 18 H, p-tBu), 1.58 (s, 36 H, o-tBu), 7.29 (s,
4 H, CH) ppm. 13C{1H} NMR (25 °C, CD2Cl2, 75.48 MHz): 31.74
[C(CH3)3], 34.79 [C(CH3)3], 35.72 [C(CH3)3], 37.45 [C(CH3)3],
124.20 (CH), 143.56 (Ar-C), 144.69 (Ar-C), 145.98 (Ar-C) ppm. IR
(ATR, 25 °C, 32 scans): ν = 2999 (w), 2954 (m), 2935 (m), 2901
˜
[8] a) E. Niecke, M. Nieger, F. Reichert, Angew. Chem. Int. Ed.
Engl. 1988, 27, 1715–1716; b) E. Niecke, R. Detsch, M. Nieger,
R. Reichert, W. W. Schoeller, Bull. Soc. Chim. Fr. 1993, 130,
25–31.
(m), 2867 (m), 1596 (w), 1558 (vw), 1539 (vw), 1506 (vw), 1472 (w),
1456 (m), 1435 (w), 1409 (m), 1401 (m), 1398 (m), 1388 (m), 1359
(s), 1287 (w), 1261 (w), 1247 (w), 1240 (m), 1207 (m), 1196 (m),
1171 (s), 1140 (w), 1102 (s), 1022 (w), 994 (vw), 944 (vw), 933 (vw),
921 (w), 909 (w), 878 (m), 835 (s), 816 (m), 780 (s), 748 (m), 683
(s), 649 (w), 621 (s), 587 (s), 563 (w), 535 (s) cm–1. Raman [200 mW,
25 °C, 117 scans]: 3000 (1), 2967 (4), 2957 (3), 2918 (4), 2904 (4),
2775 (1), 2707 (1), 1598 (4), 1448 (2), 1412 (2), 1391 (2), 1361 (1),
1289 (2), 1242 (1), 1213 (4), 1184 (5), 1142 (4), 1112 (1), 1025 (1),
924 (1), 880 (2), 860 (2), 821 (1), 780 (1), 759 (1), 564 (1), 540 (1),
301 (1), 231 (3), 169 (10), 148 (2), 122 (2) cm–1.
[9] A. Schulz, A. Villinger, Angew. Chem. 2008, 120, 614–617; An-
gew. Chem. Int. Ed. 2008, 47, 603–606.
[10] a) D. Michalik, A. Schulz, A. Villinger, N. Weding, Angew.
Chem. 2008, 120, 6565–6568; Angew. Chem. Int. Ed. 2008, 47,
6465–6468; b) A. Villinger, A. Westenkirchner, R. Wustrack,
A. Schulz, Inorg. Chem. 2008, 47, 9140–9142; c) W. Baumann,
A. Schulz, A. Villinger, Angew. Chem. 2008, 120, 9672–9675;
Angew. Chem. Int. Ed. 2008, 47, 9530–9532; d) D. Michalik, A.
Schulz, A. Villinger, Inorg. Chem. 2008, 47, 8316–8322; e) R.
Kutzora, A. Schulz, A. Villinger, R. Wustrack, Dalton Trans.
2009, 9304–9311; f) A. Schulz, A. Villinger, Inorg. Chem. 2009,
48, 7359–7367.
Supporting Information (see footnote on the first page of this arti-
cle): Details for the preparation and characterization of all com-
pounds is presented.
[11] Reviews: a) I. Krossing, I. Raabe, Angew. Chem. Int. Ed. 2004,
43, 2066–2090; b) C. Reed, Acc. Chem. Res. 1998, 31, 133–139;
c) S. H. Strauss, Chem. Rev. 1993, 93, 927–942 and references
cited therein.
[12] A similar diversity of products for the attempted synthesis of
[Cl–Sb(μ-NR)]2 (R = 2,6-dimethylphenyl) was also reported:
N. Burford, E. Edelstein, J. C. Landry, M. J. Ferguson, R. Mc-
Donald, Chem. Commun. 2005, 40, 5074–5076.
Acknowledgments
We are indebted Johannes Thomas for Raman measurements.
[13] E. Niecke, J. Hombeul, M. Blättner, V. von der Gönna, A. Ru-
ban in Synthetic Methods of Organometallic and Inorganic
Chemistry, 1996, Thieme, Stuttgart, NewYork.
[14] Holleman Wiberg, Lehrbuch der Anorganischen Chemie, Vol.
102., Walter de Gruyter, Berlin, 2007, Anhang IV.
[15] C. B. Fischer, S. Xu, H. Zipse, Chem. Eur. J. 2006, 12, 5779–
5784.
[16] G. M. Sheldrick, SHELXS-97: Program for the Solution of
Crystal Structures, University of Göttingen, Germany 1997.
[17] G. M. Sheldrick, SHELXL-97: Program for the Refinement of
Crystal Structures, University of Göttingen, Germany 1997.
[18] G. M. Sheldrick, SADABS Version 2, University of Göttingen,
Germany 2004.
[1] M. S. Balakrishna, D. J. Eisler, T. Chivers, Chem. Soc. Rev.
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[2] L. Stahl, Coord. Chem. Rev. 2000, 210, 203–250 and references
cited therein.
[3] a) E. L. Doyle, L. Riera, D. S. Wright, Eur. J. Inorg. Chem.
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[4] N. Kuhn, O. J. Scherer, Z. Naturforsch., Teil B 1979, 34, 888.
[5] D. C. Haagenson, L. Stahl, R. J. Staples, Inorg. Chem. 2001,
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[6] D. J. Eisler, T. Chivers, Inorg. Chem. 2006, 45, 10734–10742.
[7] a) N. Burford, T. S. Cameron, K. D. Conroy, B. Ellis, M.
Lumsden, C. L. B. Macdonald, R. McDonald, A. D. Phillips,
P. J. Ragogna, R. W. Schurko, D. Walsh, R. E. Wasylishen, J.
Received: August 19, 2010
Published Online: November 3, 2010
5508
www.eurjic.org
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2010, 5501–5508