From a stable silanone complex to isolable, donor-supported silicoxonium halides [LSi(dmap)=O-SiMe3+X-

Article abstract of DOI:10.1002/chem.201101610

The first donor-stabilized silylated silicoxonium species [LSi=O-SiMe ₃⁺ (L=(RN)C(=CH₂)CH=CMe(NR), R=2,6-iPr ₂C₆H₃) have been synthesized from the reaction of the dmap-supported (dmap=p-dim

Full text of DOI:10.1002/chem.201101610

DOI: 10.1002/chem.201101610
From a Stable Silanone Complex to Isolable, Donor-Supported SiliACHTNUTGRNEUNGcoxonium
+
ꢀ
ꢀ
Halides ACTHNUGRTNENUG[LSiCAHTUNGTRENN(GUN dmap)=O SiMe3] X **
Yun Xiong, Shenglai Yao, Elisabeth Irran, and Matthias Driess*[a]
Abstract: The first donor-stabilized si-
the
ionic
silicoxonium
ꢀ
bromide
in THF. In the case of Me3SiI, the reac-
tion furnishes the silicoxonium iodide
+
ꢀ
ꢀ
lylated silicoxonium species [LSi=O
[L(dmap)Si=O SiMe3] Br (3) can be
ACHTUNGTRENNUNG
SiMe3]+
(L=(RN)C
(=CH2)CH=
obtained as a primary product of the
reaction with Me3SiBr, which affords
[LSi(Br)OSiMe3] (4) with release of
the dmap ligand at room temperature
[LACTHNGUETRN(NUG dmap)Si=O SiMe3] I (5) as the
+
ꢀ
ꢀ
CMe(NR), R=2,6-iPr2C6H3) have been
synthesized from the reaction of the
dmap-supported (dmap=p-dimethyla-
minopyridine) silanone complex [LSi-
most stable species. Compounds 2–5
were isolated and fully characterized
through multinuclear NMR spectrosco-
py, mass spectrometry, elemental analy-
ses, and single-crystal X-ray diffraction
analyses.
ACHTUNGTRENNUNG(dmap)=O] (1) with trimethylsilyl hal-
Keywords: dimethylaminopyridine ·
halides · Lewis bases · silanones ·
silicoxonium ion
ides. Although the reaction with
Me3SiCl leads directly to the Si=O ad-
dition product [LSi(Cl)OSiMe3] (2),
Introduction
taking advantage of kinetic protection and thermodynamic
stabilization, we recently succeeded in synthesizing a series
of donor- and/or acceptor-stabilized silicon species that bear
the Si=O subunit,[8–11] among which the 4-dimethylaminopyr-
Carboxonium ions, in which the positive charge can delocal-
ize into the neighboring carbon atom through a resonance
interaction, exhibit both carboxonium and carbenium ion
character (Scheme 1, E=C). They are important intermedi-
ates in many acid-catalyzed re-
idine (dmap)-supported silanone (silaurea) species
1
(Scheme 2) represents an isolable silicon analogue of ke-
tones suitable for reactivity studies of the Si=O moiety.[12]
Although the Si=O double bond in 1 is highly polar and an
actions.[1] To date, long-lived
ꢀ
protonated as well as alkylated
carboxonium ions are readily
Si O single bond is favored in its resonance structures, in-
[12]
terestingly, 1 reacts with NH3 and H2S[13] across the Si=O
prepared by protonation of the
bond to give unique silanoic acid derivatives. In addition,
the Si=O moiety in 1 also shows coordination ability by re-
acting with Lewis acids such as AlMe3, thus leading to the
stable Lewis acid–base adduct A with a [Si=O!AlMe3]
moiety (Scheme 2).[14] The latter reactions prompted us to
investigate the reactivity of 1 toward trimethylsilyl halides
Me3SiX (X=Cl, Br, and I). Since the Me3Si+ is isoelectronic
to AlMe3, the addition of Me3SiX to 1 was expected to give
isolable silylated silicoxonium species B (Scheme 2). Herein
we wish to report the successful isolation and characteriza-
tion of the first donor-stabilized silicoxonium species
carbonyl
compounds
with
Scheme 1. The
ions (E=C) and silicoxonium
(E=Si) ions.
carboxonium
strong acids or by alkylation of
the carbonyl compounds using
alkyl triflates and so on.[2,3]
Even the silylated carboxonium
ions,[4] also named siloxycarbenium ions,[5] have been pre-
pared by generation of the trialkylsilyl cation in situ by
using the Corey hydride transfer[6] in the presence of ke-
tones, although none of the structures have been proven
crystallographically as yet.
+
ꢀ
ꢀ
In contrast, the corresponding heavier silicon analogues,
that is, silicoxonium ions [>Si=OR]+ (R=H, alkyl, silyl)
are scarcely investigated on account of the difficulty in syn-
thesizing suitable Si=O-containing silanone species.[7] By
[LACHTNGUTREN(UNG dmap)Si=O SiMe3] X (L=RNCACHTUNGRTNEN(UNG =CH2)CH=CMeNR;
R=2,6-iPr2C6H3; X=Br, 3; X=I, 5) along with the Si=O
addition products [LSi(X)OSiMe3] (X=Cl, 2; X=Br, 4).
[a] Dr. Y. Xiong, Dr. S. Yao, Dr. E. Irran, Prof. Dr. M. Driess
Technische Universitꢀt Berlin
Institute of Chemistry
Metalorganic and Inorganic Materials
Sekr. C2, Strasse des 17. Juni 135
10623 Berlin (Germany)
Fax : (+49)30-314-29732
E-mail: matthias.driess@tu-berlin.de
Scheme 2. The dmap-stabilized silanone (silaurea) 1 and its Lewis ad-
ducts A and B.
[**] dmap=p-dimethylaminopyridine; X=Br, I.
11274
ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 11274 – 11279

FULL PAPER
Results and Discussion
The EIMS spectrum of 2 shows the molecular ion M at
m/z 566 (9%) along with the most intensive peak at m/z 551
assignable to [MꢀMe]+. The proton NMR spectrum of 2 in
[D8]THF shows the characteristic feature of the ligand L
and a singlet at d=ꢀ0.43 ppm for the SiMe3 group. Its
29Si NMR spectrum exhibits a singlet at d=ꢀ67 ppm for the
silicon nucleus of the LSi moiety and a singlet at d=14 ppm
for the SiMe3 subunit. Some of the NMR spectroscopic data
All the reactions of 1 with Me3SiX (X=Cl, Br, I) are sum-
marized in Scheme 3. When equimolar amounts of Me3SiCl
were added to a suspension of 1 in toluene at room temper-
ature, the reaction mixture turned to a clear solution imme-
diately, thus indicating the complete conversion of 1. The
proton NMR spectrum of the resulting mixture shows the
corresponding resonance signals for the ꢂfreeꢃ dmap mole-
cule and the Si=O addition product 2 (Scheme 3).
+
ꢀ
ꢀ
for 2–5 and for [Ph2C=O SiMe3] TFPB (TFPB=tetrakis-
AHCTUNGTRENNUNG
We propose that the silicoxonium chloride 2’ (Scheme 3)
is formed initially, which subsequently liberates dmap to
afford the addition product 2 on account of the formation of
Table 1.
Table 1. Comparison of selected chemical shifts in the 1H and 29Si NMR
spectra of compounds 2–5 and [Ph2C=O SiMe3] TFPB (TFPB=tetra-
kis[3,5-bis(trifluoromethyl)phenyl]borate); d in ppm.
ꢀ
ꢀ
ꢀ
+
ꢀ
a strong Si Cl bond. Since the analogous Si Br and Si I
bond formation is less favored, the corresponding silicoxoni-
um halides 3 and 5 (Scheme 3) were expected to be more
stable than 2’. This is confirmed by addition of equimolar
amounts of Me3SiBr and Me3SiI to solutions of 1 in toluene,
which leads to facile formation of a saltlike precipitate of 3
and 5, respectively (Scheme 3). The ion pair 3 is stable in
the solid state; however, it slowly converts to the more
ꢀ
+
ꢀ
2
3
4
5
[Ph2C=O SiMe3]
TFPB[5]
d(1H)
SiMe3
d(29Si)
LSi
ꢀ0.43[a] ꢀ0.19[a] ꢀ0.39[a] ꢀ0.20[a]
ꢀ0.45[b]
0.54[b]
ꢀ67[a]
(ꢀ65[b]
14[a]
ꢀ76[a]
ꢀ70[a]
ꢀ75[a]
)
d(29Si)
SiMe3
18[a]
16[a]
18[a]
52.3[b]
ꢀ
(16[b]
)
stable Si Br addition product 4 under release of the dmap
ligand in THF solutions at room temperature. In contrast,
the ion pair 5 is stable even in boiling THF. This underlines
that the conversion of the ionic species 2’, 3, and 5 to the ad-
dition products depends on the nucleophilicity of the halide
anion towards silicon as portrayed in Scheme 4. The compo-
sition and constitution of all isolated compounds 2–5 were
determined by MS, multinuclear NMR spectroscopy, ele-
mental (C, H, N) analyses, and single-crystal X-ray diffrac-
tion studies.
[a] Recorded in [D8]THF. [b] Recorded in [D2]dichloromethane.
Compound 2 is soluble in toluene and THF. Single crys-
tals of 2 suitable for X-ray diffraction analysis could be ob-
tained in THF at room temperature. Compound 2 crystal-
lized in the monoclinic space group P21/m (Figure 1). The
two Si atoms are tetrahedrally coordinated and bridged by
ꢀ
an oxygen atom. The Si1 Cl1 bond length of 2.055(1) ꢄ
falls in the normal range of
[15]
ꢀ
Si Cl single bonds. The same
is true for the two Si N bonds
(1.707(2) ꢄ). Remarkably, the
ꢀ
ꢀ
Si1 O1 distance of 1.587(2) ꢄ
is significantly shorter than that
ꢀ
of Si2 O1 (1.650(2) ꢄ), thus re-
flecting the larger electrophilic
character of the Si1 atom on ac-
count of its more electronega-
tive substituents. The Si1-O1-
Si2 bond angle of 152.8(2)8 is
similar to values observed for
other disiloxanes.[16a] Selected
metric parameters are summar-
ized in Table 2.
The cation in 3 represents the
first isolated Lewis base stabi-
lized silylated silicoxonium that
Scheme 3. Reactions of 1 with Me3SiX (X=Cl, Br, I).
+
ꢀ
contains an [Si=O SiMe3]
moiety. The HR-ESI spectrum
of 3 in cation mode showed a
peak at m/z 655.42310 (calcd
655.42219) that is assignable to
(dmap)=O SiMe3] . In the
proton NMR spectrum of 3, the
+
ꢀ
[LSi
N
Scheme 4. Stability of silylated silicoxonium species.
Chem. Eur. J. 2011, 17, 11274 – 11279
ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
11275

M. Driess et al.
Figure 2. Molecular structure of 3. Thermal ellipsoids are drawn at the
50% probability level. Hydrogen atoms are omitted for clarity. Selected
Figure 1. Molecular structure of 2. Thermal ellipsoids are drawn at the
50% probability level. Hydrogen atoms are omitted for clarity. The
methyl groups of the SiMe3 each adopts two positions in the crystal struc-
ture due to the disordering and only one of them is shown. Selected bond
ꢀ
ꢀ
ꢀ
bond lengths [ꢄ] and angles [8]: Si1 O1 1.584(1), Si2 O1 1.677(1), Si1
ꢀ
ꢀ
ꢀ
ꢀ
N1 1.713(2), Si1 N2 1.707(2), Si1 N3 1.808(2), Si2 C37 1.842(2), Si2
ꢀ
ꢀ
ꢀ
ꢀ
C38 1.848(2), Si2 C39 1.858(2), C1 C2 1.339(3), C2 C3 1.456(3), C3 C4
ꢀ
1.341(3), C4 C5 1.500(3); Si1-O1-Si2 159.1(1), N2-Si1-N3 107.8(1), N1-
ꢀ
ꢀ
ꢀ
lengths [ꢄ] and angles [8]: Si1 O1 1.587(2), Si2 O1 1.650(2), Si1 N1
Si1-N3 108.4(1), N1-Si1-N2 106.7(1).
ꢀ
ꢀ
ꢀ
ꢀ
1.707(2), Si1 N2 1.707(2), Si1 Cl1 2.055(1), C1 C2 1.417(4), C2 C3
ꢀ
1.406(3), N1 C2 1.425(3); Si1-O1-Si2 152.8(2).
ꢀ
nance structures shown in Scheme 5. Accordingly, the Si1
O1 distance of 1.584(1) ꢄ is slightly longer than that of the
Table 2. Comparison of selected metric parameters of compounds 2–5.
Distances in ꢄ and angles in 8.
Si=O bond in 1 (1.545(2) ꢄ,[12] whereas the Si2 O1 bond
ꢀ
ꢀ
(1.677(1) ꢄ) is comparable to the Si O s-bond length in
2
3
4
5
ꢀ
LSiO
(NHC) (1.682(2) ꢄ).[17] Notably, the latter Si1 O1 dis-
ꢀ
Si1 N1
1.707(2)
1.707(2)
–
1.587(2)
1.650(2)
152.8(2)
1.713(2)
1.707(2)
1.808(2)
1.584(1)
1.677(1)
159.1(1)
1.715(2)
1.715(2)
–
1.585(2)
1.646(2)
156.2(1)
1.709(3)
1.713(3)
1.811(3)
1.582(3)
1.662(3)
165.1(2)
ꢀ
tance is also marginally longer than the corresponding Si O
ꢀ
Si1 N2
length in [LSiCAHTUNGTRENNNUG
ꢀ
Si1 N3
ꢀ
Si1 O1
servation may reflects the electronically less positive charac-
ter of silicon relative to aluminum.
ꢀ
Si2 O1
Si1-O1-Si2
As mentioned above, the ion pair 3 is more stable in the
solid state and reacts slowly at ambient temperature in THF
to form the corresponding silyl bromide 4 with release of
the dmap molecule (Scheme 3). The EIMS spectrum of iso-
lated 4 shows a peak of the molecular ion M at m/z 614
(9%), whereas the most intensive peak at m/z 599 corre-
sponds to [MꢀMe]+. As shown in Table 1, the chemical
characteristic resonances for the ligands L and dmap can be
assigned unambiguously. The sharp singlet at d=ꢀ0.19 ppm
for the protons of the SiMe3 group exhibits a slight down-
field shift relative to that of 2 (d=ꢀ0.43 ppm, Table 1). Sim-
ilar trends can be observed for the resonance of the Si atom
in SiMe3 (d=18 ppm vs. 14 ppm in 2) and for the Si nucleus
of LSi (d=ꢀ76 ppm vs. ꢀ67 ppm in 2).
1
shift of the protons of the SiMe3 group in the H NMR spec-
trum appears at d=ꢀ0.39 ppm, similarly to that of 2
(d=ꢀ0.43 ppm). Likewise, the 29Si resonances are compara-
ble to those observed for 2.
Compound 3 is sparingly soluble in toluene and diethyl
ether but soluble in THF. It crystallized as colorless cubes in
the monoclinic space group P21/c. A single-crystal X-ray dif-
fraction analysis revealed that 3 is an ion pair (Figure 2) as
shown by the closest Si···Br contacts of 4.700 and 6.227 ꢄ
for Si2···Br1 and Si1···Br1, respectively. Thus the structural
features resemble that of the ionic compound [py!SiMe3]+
Brꢀ (py=pyridine) with a Si···Br distance of 4.359 ꢄ.[16b]
The dmap molecule remains coordinated to the Si1 atom,
which thus adopts a distorted tetrahedral coordination envi-
ꢀ
ronment. The Si1 N3 distance of 1.808(2) ꢄ is significantly
ꢀ
ꢀ
longer than the other Si N distances (Si1 N1 (1.713(2) ꢄ)
ꢀ
+
and Si1 N2 (1.707(2) ꢄ)). The positive charge in 3 is pre-
sumably thoroughly delocalized as represented by the reso-
ꢀ
Scheme 5. Resonance structures of the [LSi(dmap)=O SiMe3] cation in
3 and 5.
11276
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ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 11274 – 11279

Silicoxonium Halides
FULL PAPER
Figure 4. Molecular structure of 5. Thermal ellipsoids are drawn at the
50% probability level. Hydrogen atoms and THF molecules are omitted
for clarity. The iodide anion and solvent THF molecules are in disorder.
Figure 3. Molecular structure of 4. Thermal ellipsoids are drawn at the
50% probability level. Hydrogen atoms are omitted for clarity. The
methyl groups of the SiMe3 and the aryl groups each adopts two positions
in the crystal structure due to the disordering and only one of them is
ꢀ
ꢀ
Selected bond lengths [ꢄ] and angles [8]: Si1 O1 1.582(3), Si2 O1
ꢀ
ꢀ
ꢀ
1.662(3), Si1 N1 1.709(3), Si1 N2 1.717(3), Si1 N3 1.811(3); Si1-O1-Si2
165.1(2), N2-Si1-N3 106.8(2), N1-Si1-N3 109.4(2), N1-Si1-N2 106.0(2),
O1-Si1-N1 114.4(2), O1-Si1-N2 115.3(2), O1-Si1-N3 104.6(2).
ꢀ
ꢀ
shown. Selected bond lengths [ꢄ] and angles [8]: Si1 O1 1.585(2), Si2
ꢀ
ꢀ
ꢀ
ꢀ
O1 1.646(2), Si1 Br1 2.240(1), Si1 N1 1.715(2); Si1 N2 1.715(2), C1 C2
ꢀ
ꢀ
1.417(4), C2 C3 1.406(3), N1 C2 1.425(3); Si1-O1-Si2 156.2(1), O1-Si1-
Br1 108.9(1), O1-Si1-N1 112.1(1).
silicon atom of the LSi subunit in 3 and 5 do not differ sig-
nificantly from those of the neutral species 2 and 4
(Table 2). This observation may be ascribed in large part to
the strong donor effect of the supporting dmap ligand in 3
and 5, respectively.
Single crystals of 4 suitable for X-ray diffraction analysis
could be obtained from THF solutions; the compound crys-
tallized in a monoclinic space group P21/m with similar dis-
orders as those that occurred in 2. As expected, the com-
pound is isostructural to the chloride analogue 2 (Figure 3).
ꢀ
The Si1 Br1 distance of 2.240(1) ꢄ, which is significantly
shorter than that in the silicoxonium bromide 3 (6.227 ꢄ),
Conclusion
ꢀ
falls in the common range of Si Br distances in related silyl
bromides.[15] Despite the different halogen atoms connected
to Si1 in 4 relative to 2, their respective metric parameters
are quite similar (Table 2).
In summary, by examining the reactivity of the donor-stabi-
lized silanone complex [LSiACTHNUTRGENUGN(dmap)=O] (1) towards trime-
thylsilyl halides Me3SiX (X=Cl, Br, and I) under mild con-
The aforementioned treatment of 1 with Me3SiI both in
toluene and in THF at room temperature led immediately
to the formation of the ionic compound 5 (Scheme 3). No
further elimination of dmap and coordination of Iꢀ to the
silicon center to give 6 was observed, even in boiling THF.
The HR-ESI spectrum of 5 (cation mode) showed a peak at
m/z 655.42316 (calcd 655.42219) assignable to the cation
ditions, the first Lewis base supported silicoxonium halides
+
ꢀ
species with [>Si=O SiMe3] have been synthesized and
isolated successfully. The stability of these silicoxonium spe-
cies depends on the nature of the respective halide counter-
ion. Although the corresponding silicoxonium chloride 2’ is
elusive during the formation of [LSi(Cl)OSiMe3] (2), the sil-
+
ꢀ
ꢀ
icoxonium bromide [LACHTNUTRGNE(NUG dmap)Si=O SiMe3] Br (3) could
+
1
[LSi
(dmap)=O SiMe3] . The H and 13C NMR spectra of 5
be isolated and structurally characterized but transforms in
ꢀ
in [D8]THF show very similar patterns to those of 3 for the
supporting ligand L and the coordinated dmap. The same is
true for the 29Si NMR spectroscopic resonances of 5 and 3
(Table 1). Pale yellow rhombic crystals of 5 suitable for
X-ray diffraction analysis could be obtained from a THF so-
lution at room temperature. The compound crystallized in
the monoclinic space group P2/c with several THF mole-
cules in the asymmetric unit. Similar to 3, compound 5 fea-
tures an ionic structure, although they are not isostructural
solutions to afford [LSi(Br)OSiMe3] (4) and ꢂfreeꢃ dmap. In
ꢀ
contrast, the corresponding iodide salt [L
G
SiMe3]+Iꢀ 5 is stable both in the solid state and in THF. The
first Lewis base stabilized silicoxonium compounds 3 and 5
are expected to serve as promising precursors for the syn-
thesis of value-added organosilicon compounds. Respective
investigations are currently in progress.
ꢀ
(Figure 4). The shortest Si I contact amounts to 5.176 ꢄ.
Experimental Section
The conformation and the geometric parameters of the
cation of 5 are very similar to those of 3 (Table 2). Unex-
pectedly, the corresponding metric parameters around the
General: All experiments and manipulations were carried out under dry
oxygen-free nitrogen by using standard Schlenk techniques or using an
Chem. Eur. J. 2011, 17, 11274 – 11279
ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
11277

M. Driess et al.
Synthesis of 3: Me3SiBr (0.070 mL, d=1.16 gmLꢀ1
, 0.53 mmol) was
MBraun inert atmosphere dry box that contained an atmosphere of puri-
fied nitrogen. Solvents were dried by standard methods and freshly dis-
tilled prior to use. The starting material 1 was prepared according to liter-
ature procedures.[12,18] The NMR spectra were recorded using Bruker
spectrometers ARX200 and AV400 and with residual solvent signals as
internal references (1H and 13C{H}) or with an external reference (SiMe4
for 29Si). Abbreviations: s=singlet, d=doublet, t=triplet, sept=septet,
m=multiplet, br=broad. Elemental analyses were performed using a
FlashEA 1112 CHNS analyzer.
added to a suspension of 1 (0.31 g, 0.53 mmol) in toluene (10 mL) at
room temperature. The suspension turned clear immediately. In half an
hour compound 3 precipitated from the solution with yield of 0.30 g
(0.41 mmol, 77%). X-ray qualified single crystals were obtained as color-
less plates from THF at ꢀ208C. M.p. 1708C (decomposed); 1H NMR
(200.13 MHz, [D8]THF, 258C): d=ꢀ0.19 (s, 9H; SiMe3), 0.64 (d,
3J(H,H)=7.0 Hz, 3H; CHMe2), 0.71 (d, 3J(H,H)=7.0 Hz, 3H; CHMe2),
1.03 (d, 3J(H,H)=7.0 Hz, 3H; CHMe2), 1.10 (d, 3J(H,H)=7.0 Hz, 3H;
CHMe2), 1.21 (d, 3J(H,H)=7.0 Hz, 3H; CHMe2), 1.27 (d, 3J(H,H)=
7.0 Hz, 3H; CHMe2), 1.41 (d, 3J(H,H)=7.0 Hz, 3H; CHMe2), 1.45 (d,
3J(H,H)=7.0 Hz, 3H; CHMe2), 1.79 (s, 3H; NCMe), 2.45 (sept,
3J(H,H)=7.6 Hz, 1H; CHMe2), 2.74 (sept, 3J(H,H)=7.6 Hz, 1H;
CHMe2), 3.25 (s, 1H; NCCH2), 3.47 (s, 6H; dmap), 3.51–3.68 (m, 2H;
CHMe2), 4.05 (s, 1H; NCCH2), 5.65 (s, 1H; g-CH), 6.66–6.80 (m, 1H;
dmap), 7.09–7.27 (m, 6H; 2,6-iPr2C6H3), 7.77–8.74 ppm (m, 3H; dmap);
13C{1H} NMR (100.61 MHz, [D8]THF, 258C): d=1.99 (SiMe3), 22.1
(NCCH3), 24.1, 24.3, 25.0, 25.9, 26.4, 28.8, 29.6, 29.8 (CHMe2, CHMe2),
41.3 (dmap), 87.8 (NCCH2), 107.1 (g-C), 111.8 (dmap), 124.9, 125.0,
125.8, 126.1, 129.1, 134.8, 144.3, 148.0, 148.6, 149.1, 149.7, 149.8, 158.3,
174.7 ppm (NCMe, NCCH2, dmap, 2,6-iPr2C6H3); 29Si{1H} NMR
(79.49 MHz, [D8]THF, 258C): d=ꢀ76 (s, 1Si; N3SiO), 18 ppm (SiMe3);
HR-ESI: m/z calcd: 655.42219 [MꢀBr]+; found: 655.42310; elemental
analysis calcd (%) for C39H59N4Si2OBr: C 63.65, H 8.08, N 7.61; found: C
63.54, H 8.04, N 7.87.
Single-crystal X-ray structure determination: Crystals were each mounted
on a glass capillary in perfluorinated oil and measured in a cold N2 flow.
The data of 2–5 were collected using an Oxford Diffraction Xcalibur S
Sapphire instrument at 150 K (MoKa radiation, l=0.71073 ꢄ). The struc-
tures were solved by direct methods and refined on F2 with the SHELX-
97[19] software package. The positions of the hydrogen atoms were calcu-
lated and considered isotropically according to a riding model.
CCDC-827047 (2), 827048 (3), 827049 (4), and 827050 (5) contain the
supplementary crystallographic data for this paper. These data can be ob-
tained free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
Crystal data for 2: Monoclinic, space group P21/m; a=8.861(2), b=
19.952(3), c=10.235(2) ꢄ; b=113.73(2)8; V=1656.6(5) ꢄ3; Z=2; 1calcd
=
1.141 Mgmꢀ3
; mACHTUNGTRENNUNG ; 6608 collected reflections, 3003
(MoKa)=0.213 mmꢀ1
crystallographically independent reflections (Rint =0.0416), 2096 reflec-
tions (I>2s(I)); qmax =258; R(Fo)=0.0501 (I>2s(I)), wR(F2o)=0.1235
(all data), 201 refined parameters.
Synthesis of 4: Me3SiBr (0.073 mL, d=1.16 gmLꢀ1
, 0.55 mmol) was
added to a suspension of 1 (0.32 g, 0.55 mmol) in THF (10 mL) at room
temperature. The suspension turned clear immediately. The proton NMR
spectra showed a mixture of 3 and 4. By heating the solution to 508C for
3 d, compound 3 converted to 4 completely. Compound 4 crystallized as
colorless rods from the solution at 48C with a yield of 0.25 g (0.41 mmol,
Crystal data for 3: Monoclinic, space group P21/c; a=10.8224(4), b=
20.9731(9), c=17.9482(5) ꢄ; b=96.219(3)8; V=4049.9(3) ꢄ3; Z=4;
1calcd =1.207 Mgmꢀ3; m(MoKa)=1.108 mmꢀ1; 29892 collected reflections,
7098 crystallographically independent reflections (Rint =0.0381), 5107 re-
flections with (I>2s(I)), qmax =258, R(Fo)=0.0312 (I>2s(I)), wR(F2o)=
0.0684 (all data), 438 refined parameters.
1
74%). M.p. 2158C; H NMR (200.13 MHz, [D8]THF, 258C): d=ꢀ0.39 (s,
9H; SiMe3), 1.14–1.36 (m, 24H; CHMe2), 1.64 (s, 3H; NCMe), 3.08 (s,
1H; NCCH2), 3.44–3.72 (m, 4H; CHMe2), 3.80 (s, 1H; NCCH2), 5.37 (s,
1H; g-CH), 7.16–7.32 ppm (m, 6H; 2,6-iPr2C6H3); 13C{1H} NMR
(100.61 MHz, [D8]THF, 258C): d=1.36 (SiMe3), 21.8 (NCCH3), 24.1,
24.5, 25.3, 25.4, 26.0, 26.1, 26.4, 27.2 (CHMe2), 29.0, 29.1, 29.6, 29.8
(CHMe2), 87.9 (NCCH2), 105.1 (g-C), 124.6, 124.7, 125.7, 126.3, 128.8,
128.9, 135.4, 135.8, 141.3, 148.5, 148.6, 149.7, 150.1, 150.4 ppm (NCMe,
NCCH2, 2,6-iPr2C6H3); 29Si{1H} NMR (79.49 MHz, [D8]THF, 258C): d=
ꢀ70 (s, 1Si; N3SiO), 16 ppm (s, 1Si, SiMe3); EI-MS: m/z (%): 614 (9)
[M]+, 599 (100), [MꢀMe]+, 571 (65) [MꢀiPr]+; elemental analysis calcd
(%) for C32H49N2Si2OBr: C 62.62, H 8.05, N 4.56; found: C 62.54, H 7.79,
N 4.61.
Crystal data for 4: Monoclinic, space group P21/m; a=8.8642(4), b=
19.8176(8), c=10.4248(4) ꢄ; b=114.594(3)8’ V=1665.2(1) ꢄ3; Z=2;
1calcd =1.224 Mgmꢀ3; m(MoKa)=1.332 mmꢀ1; 14482 collected reflections,
3032 crystallographically independent reflections (Rint =0.0352), 2482 re-
flections with (I>2s(I)), qmax =258, R(Fo)=0.0309 (I>2s(I)), wR(F2o)=
0.0784 (all data), 267 refined parameters.
Crystal data for 5: Monoclinic, space group P2/c; a=19.2310(9), b=
11.3749(5), c=23.172(1) ꢄ; b=106.280(5)8; V=4865.5(4) ꢄ3; Z=4,
1calcd =1.200 Mgmꢀ3; m(MoKa)=0.745 mmꢀ1; 35224 collected reflections,
8568 crystallographically independent reflections (Rint =0.0493), 6556 re-
flections with (I>2s(I)), qmax =258, R(Fo)=0.0586 (I>2s(I)), wR(F2o)=
0.1539 (all data), 555 refined parameters.
Synthesis of 5: Me3SiI (0.060 mL, d=1.40 gmLꢀ1, 0.42 mmol) was added
to a suspension of 1 (0.25 g, 0.42 mmol) in toluene (10 mL) at room tem-
perature. The suspension turned clear immediately. In half an hour com-
pound 5 precipitated from the solution with yield of 0.30 g (0.38 mmol,
90%). X-ray qualified single crystals were obtained as colorless plates
from THF at 48C. M.p. 1958C (decomposed); 1H NMR (200.13 MHz,
Synthesis of 2: Me3SiCl (0.080 mL, d=0.85 gmLꢀ1
, 0.63 mmol) was
added to a suspension of 1 (0.37 g, 0.63 mmol) in toluene (10 mL) at
room temperature. The suspension turned clear immediately. From the
concentrated solution (4 mL) compound 2 crystallized as colorless plates
with yield of 0.30 g (0.53 mmol, 84%). X-ray qualified single crystals
were obtained from THF at ꢀ208C. M.p. 2138C; 1H NMR (200.13 MHz,
[D8]THF, 258C): d=ꢀ0.43 (s, 9H; SiMe3), 1.09–1.38 (m, 24H; CHMe2),
1.63 (s, 3H; NCMe), 3.05 (s, 1H; NCCH2), 3.15 (sept, 3J(H,H)=7.0 Hz,
1H; CHMe2), 3.40–3.69 (m, 3H; CHMe2), 3.76 (s, 1H; NCCH2), 5.31 (s,
1H; g-CH), 7.09–7.38 ppm (brm, 6H; 2,6-iPr2C6H3); 1H NMR
(200.13 MHz, [D2]dichloromethane, 258C): d=ꢀ0.44 (s, 9H; SiMe3),
1.15–1.36 (m, 24H; CHMe2), 1.63 (s, 3H; NCMe), 3.05 (s, 1H; NCCH2),
3.34–3.63 (m, 4H; CHMe2), 3.79 (s, 1H; NCCH2), 5.31 (s, 1H; g-CH),
7.16–7.32 ppm (brm, 6H; 2,6-iPr2C6H3); 13C{1H} NMR (100.61 MHz,
[D8]THF, 258C): d=1.20 (SiMe3), 22.0 (NCMe), 23.5, 24.2, 24.5, 24.8,
25.3, 26.0, 26.1, 26.6 (CHMe2), 28.8, 28.9, 29.5, 29.6 (CHMe2), 87.2
(NCCH2), 104.2 (g-C), 123.7, 124.6, 124.7, 125.6, 125.9, 128.7, 128.8, 141.5,
143.1, 148.5, 148.9, 149.6, 149.9, 150.2 ppm (NCMe, NCCH2, 2,6-
iPr2C6H3); 29Si{1H} NMR (79.49 MHz, [D8]THF, 258C): d=ꢀ67 (s, 1Si;
N2SiOCl), 14 ppm (s, 1Si; OSiMe3); 29Si{1H} NMR (79.49 MHz,
[D8]dichloromethane, 258C): d=ꢀ65 (s, 1Si; N2SiOCl), 16 ppm (s, 1Si;
OSiMe3); EI-MS: m/z (%): 566 (9) [M]+, 551 (100), [MꢀMe]+, 523 (55)
[M+ꢀiPr]; elemental analysis calcd (%) for C32H49N2Si2OCl: C 67.50, H
8.67, N 4.92; found: C 67.30, H 8.31, N 5.03.
3
[D8]THF, 258C): d=ꢀ0.20 (s, 9H; SiMe3), 0.65 (d, J(H,H)=7.0 Hz, 3H;
CHMe2), 0.72 (d, 3J(H,H)=7.0 Hz, 3H; CHMe2), 1.04 (d, 3J(H,H)=
7.0 Hz, 3H; CHMe2), 1.11 (d, 3J(H,H)=7.0 Hz, 3H; CHMe2), 1.21 (d,
3J(H,H)=7.0 Hz, 3H; CHMe2), 1.25 (d, 3J(H,H)=7.0 Hz, 3H; CHMe2),
1.41 (d, 3J(H,H)=7.0 Hz, 3H; CHMe2), 1.45 (d, 3J(H,H)=7.0 Hz, 3H;
3
CHMe2), 1.81 (s, 3H; NCMe), 2.44 (sept, J(H,H)=7.6 Hz, 1H; CHMe2),
2.72 (sept, 3J(H,H)=7.6 Hz, 1H; CHMe2), 3.26 (s, 1H; NCCH2), 3.48 (s,
6H, dmap), 3.44–3.67 (m, 2H; CHMe2), 4.07 (s, 1H; NCCH2), 5.68 (s,
1H; g-CH), 7.17–7.32 (m, 6H; 2,6-iPr2C6H3), 7.82 (br, 2H; dmap), 8.04
(br, 1H; dmap), 8.65 ppm (br, 1H; dmap); 13C{1H} NMR (100.61 MHz,
[D8]THF, 258C): d=2.14 (SiMe3), 22.2 (NCCH3), 24.3, 24.4, 25.7, 26.1,
26.2, 26.4, 29.6, 29.7, 29.8 (CHMe2, CHMe2), 41.8 (dmap), 91.5 (NCCH2),
107.2 (g-C), 108.3 (dmap), 125.0, 125.2, 125.8, 126.3, 129.1, 129.2, 134.8,
135.3, 144.3, 148.0, 148.5, 149.1, 149.6, 149.7, 158.1, 174.7 ppm (NCMe,
NCCH2, dmap, 2,6-iPr2C6H3); 29Si{1H} NMR (79.49 MHz, [D8]THF,
258C): d=ꢀ75 ppm (s, 1Si; N3SiO), 18 ppm (s, 1Si; SiMe3); HR-ESI: m/
z calcd: 655.42219 [MꢀI]+; found: 655.42316; elemental analysis calcd
(%) for C39H59N4Si2OI: C 59.83, H 7.59, N 7.16; found: C 59.86, H 7.48,
N 7.09.
11278
www.chemeurj.org
ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2011, 17, 11274 – 11279

Silicoxonium Halides
FULL PAPER
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Received: May 25, 2011
Published online: August 25, 2011
Chem. Eur. J. 2011, 17, 11274 – 11279
ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
11279