Unexpected disproportionation of tetramethylethylenediamine-supported perchlorodisilane Cl3SiSiCl3

Article abstract of DOI:10.1021/ic301283m

The addition compound Cl₃SiSiCl₃·TMEDA was formed quantitatively by treatment of Cl₃SiSiCl₃ with tetramethylethylenediamine (TMEDA) in pentane at room temperature. The crystal structure of Cl₃SiSiCl₃·TMEDA displays one tetrahedrally and one octahedrally bonded Si atom (monoclinic, P2 ₁/n). ²⁹Si CP/MAS NMR spectroscopy confirms this structure. Density functional theory (DFT) calculations have shown that the structure of the meridional isomer of Cl₃SiSiCl₃· TMEDA is 6.3 kcal lower in energy than that of facial coordinate species. Dissolving of Cl₃SiSiCl₃·TMEDA in CH ₂Cl₂ resulted in an immediate reaction by which oligochlorosilanes Si_nCl_2n (n = 4, 6, 8, 10; precipitate) and the Cl^--complexed dianions [Si_nCl_2n+2] ^2- (n = 6, 8, 10, 12; CH₂Cl₂ extract) were formed. The constitutions of these compounds were confirmed by MALDI mass spectrometry. Additionally, single crystals of [Me₃NCH ₂CH₂NMe₂]₂[Si₆Cl ₁₄] and [Me₃NCH₂CH₂NMe ₂]₂[Si₈Cl₁₈] were obtained from the CH₂Cl₂ extract. We found that Cl₃SiSiCl ₃·TMEDA reacts with MeCl, forming MeSiCl₃ and the products that had been formed in the reaction of Cl₃SiSiCl ₃·TMEDA with CH₂Cl₂. X-ray structure analysis indicates that the structures of [Me₃NCH₂CH ₂NMe₂]₂[Si₆Cl₁₄] (monoclinic, P2₁/n) and [Me₃NCH₂CH ₂NMe₂]₂[Si₈Cl₁₈] (monoclinic, P2₁/n) contain dianions adopting an "inverse sandwich" structure with inverse polarity and [Me₃NCH ₂CH₂NMe₂]⁺ as countercations. Single crystals of SiCl₄·TMEDA (monoclinic, Cc) could be isolated by thermolysis reaction of Cl₃SiSiCl₃·TMEDA (50 °C) in tetrahydrofuran (THF).

Full text of DOI:10.1021/ic301283m

Article
pubs.acs.org/IC
Unexpected Disproportionation of Tetramethylethylenediamine-
Supported Perchlorodisilane Cl SiSiCl
3
3
†
†
†
†
†
‡
†
Jan Tillmann, Frank Meyer-Wegner, Andor Nadj, Johanna Becker-Baldus, Tanja Sinke,
Michael Bolte, Max C. Holthausen, Matthias Wagner, and Hans-Wolfram Lerner*
†
,†
†
Institut fu
̈
r Anorganische Chemie, Goethe-Universitat
̈
Frankfurt am Main, Max-von-Laue-Straße 7, 60438 Frankfurt am Main,
Germany
‡
Institut fu
Germany
̈
r Biophysikalische Chemie, Goethe-Universitat Frankfurt am Main, Max-von-Laue-Straße 9, 60438 Frankfurt am Main,
̈
*
S Supporting Information
ABSTRACT: The addition compound Cl SiSiCl ·TMEDA
3
3
was formed quantitatively by treatment of Cl SiSiCl with
3
3
tetramethylethylenediamine (TMEDA) in pentane at room
temperature. The crystal structure of Cl SiSiCl ·TMEDA
3
3
displays one tetrahedrally and one octahedrally bonded Si
2
9
atom (monoclinic, P2 /n). Si CP/MAS NMR spectroscopy
1
confirms this structure. Density functional theory (DFT)
calculations have shown that the structure of the meridional
isomer of Cl SiSiCl ·TMEDA is 6.3 kcal lower in energy than
3
3
that of facial coordinate species. Dissolving of
Cl SiSiCl ·TMEDA in CH Cl resulted in an immediate
3
3
2
2
reaction by which oligochlorosilanes Si Cl (n = 4, 6, 8, 10; precipitate) and the Cl -complexed dianions [Si Cl ]2− (n =
−
n
2n
n
2n+2
6
, 8, 10, 12; CH Cl extract) were formed. The constitutions of these compounds were confirmed by MALDI mass spectrometry.
2 2
Additionally, single crystals of [Me NCH CH NMe ] [Si Cl ] and [Me NCH CH NMe ] [Si Cl ] were obtained from the
3
2
2
2 2
6
14
3
2
2
2 2
8
18
CH Cl extract. We found that Cl SiSiCl ·TMEDA reacts with MeCl, forming MeSiCl and the products that had been formed in
2
2
3
3
3
the reaction of Cl SiSiCl ·TMEDA with CH Cl . X-ray structure analysis indicates that the structures of
3
3
2
2
[
Me NCH CH NMe ] [Si Cl ] (monoclinic, P2 /n) and [Me NCH CH NMe ] [Si Cl ] (monoclinic, P2 /n) contain
3 2 2 2 2 6 14 1 3 2 2 2 2 8 18 1
+
dianions adopting an “inverse sandwich” structure with inverse polarity and [Me NCH CH NMe ] as countercations. Single
3
2
2
2
crystals of SiCl ·TMEDA (monoclinic, Cc) could be isolated by thermolysis reaction of Cl SiSiCl ·TMEDA (50 °C) in
4
3
3
tetrahydrofuran (THF).
INTRODUCTION
transition state for the disproportionation of the disilane 1
possesses a moderately high energy and lies well below the
transition state of the corresponding base-free reaction. We
therefore come to the conclusion that the key intermediate of
the disproportionation of 1 is the amine-complexed dichlor-
osilylene and no free silylene will be formed in this reaction.
It should be noted here that the course of the reaction of 1
with pyridine is different compared to the disproportionation of
■
Over the past decades the disproportionation reaction of Si Cl
2
6
(
1) which gives the perchlorinated neopentasilane Si(SiCl )
3
1
4
−5
(
2) and SiCl4 has been widely investigated.
However,
although this reaction has been known for 60 years, its
mechanism has still not yet been fully understood, and no hard
evidence regarding the nature of the intermediates exists. Very
recently we have repeated the reaction of 1 with NR (R = Me,
Et) and found it fully reproducible. Moreover, we were able to
monitor the course of the reaction between 1 and NMe Et by
means of low-temperature two-dimensional heteronuclear
correlation spectroscopy (HETCOR) experiments. We found
that a resonance at 42.7 ppm in the H/ Si 2D spectrum
shows a correlation with the methyl protons of NMe Et which
7
6
3
6
1 with NMe . When using equimolar equivalents of reactants,
3
treatment of 1 with pyridine yielded the disilylated 1,4-
2
dihydropyridine 3, and in this reaction no perchlorinated
8
,9
neopentasilane 2 was formed (Scheme 1). Obviously, a
polarization of the central Si−Si bond of 1 had taken place. The
positively and negatively-charged fragments of 1,
1
29
2
+
−
Cl Si ··· SiCl , which had been formed, apparently underwent
3
3
could be attributed to the Si nuclei of SiCl ·NMe Et.
Additionally, we calculated the energy barriers of the base-
free and the base-catalyzed liberation of SiCl from 1. For the
2
2
an addition reaction to the pyridine ring to give the disilylated
,4-dihydropyridine 3. We had verified the constitution of 3 by
1
2
9
HETCOR NMR spectroscopy.
base-free formation of SiCl , the calculated activation energy of
2
−1
about 50 kcal mol is prohibitively high. In the base-catalyzed
case, we found a first small barrier associated with the
Received: June 18, 2012
Published: July 12, 2012
coordination of NMe to the disilane 1. The subsequent
3
©
2012 American Chemical Society
8599
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Article
Scheme 1. Reactivity of Cl SiSiCl (1) Towards NR (R =
3
3
3
Me, Et) and Pyridine
(
−
i) +NR (R = Me, Et) in pentane at −10 °C. (ii) × 3, +Si Cl , −SiCl ,
3
2
6
4
NR . (iii) +pyridine in benzene at room temperature.
3
In this paper we report the reaction of 1 with
tetramethylethylenediamine (TMEDA). The structural features
Figure 2. Solid-state structure of Cl SiSiCl ·TMEDA. (1·TMEDA)
3
3
(monoclinic, P2 /n). Displacement ellipsoids are drawn at the 50%
1
of 1·TMEDA and its disproportionation behavior have been
probability level. H atoms are omitted for clarity. Selected bond
lengths (Å) and angles (deg.): Si(1)−N(1) = 2.064(5), Si(1)−N(2) =
2.113(5), Si(1)−Cl(3) = 2.176(2), Si(1)−Cl(1) = 2.1929(19), Si(1)−
Cl(2) = 2.194(2), Si(1)−Si(2) = 2.405(2), Si(2)−Cl(5) = 2.052(2),
Si(2)−Cl(6) = 2.062(3), Si(2)−Cl(4) = 2.073(3); N(1)−Si(1)−N(2)
−
investigated. In addition we present here the structures of Cl -
2
−
complexed dianions [Si Cl2n+2] (n = 6, 8).
n
RESULTS AND DISCUSSION
■
=
84.7(2), N(1)−Si(1)−Cl(3) = 92.66(15), N(2)−Si(1)−Cl(3) =
Synthesis of 1·TMEDA. When 1 in benzene was treated
with the bidentate TMEDA at room temperature, no
neopentasilane 2 was formed; however, TMEDA-complexed
disilane 1 could be isolated as a white solid (Scheme 2). The
8
8
8.48(14), N(1)−Si(1)−Cl(1) = 88.73(15), N(2)−Si(1)−Cl(1) =
9.68(14), Cl(3)−Si(1)−Cl(1) = 177.58(12), N(1)−Si(1)−Cl(2) =
90.23(17), N(2)−Si(1)−Cl(2) = 174.58(17), Cl(3)−Si(1)−Cl(2) =
89.75(8), Cl(1)−Si(1)−Cl(2) = 92.22(9), N(1)−Si(1)−Si(2) =
174.24(17), N(2)−Si(1)−Si(2) = 98.80(16), Cl(3)−Si(1)−Si(2) =
91.99(8), Cl(1)−Si(1)−Si(2) = 86.74(8), Cl(2)−Si(1)−Si(2) =
86.38(9).
Scheme 2. Synthesis of Cl SiSiCl ·TMEDA (1·TMEDA)
3
3
(
THF). Single crystals of 1·TMEDA could be obtained by gas-
phase diffusion of hexachlorodisilane and TMEDA. Overall, the
analytical data that we found are in good agreement with this
29
structure. The Si CP/MAS spectrum of 1·TMEDA features a
resonance at −0.5 ppm which is typical of tetracoordinate
silicon atoms and a signal at −163.5 ppm which is in the range
found for hexacoordinate silicon atoms. The mass spectrum
revealed a peak which could be assigned to 1·TMEDA. The
element ratio has also been confirmed by a combustion
analysis.
(i) +TMEDA, in pentane at room temperature.
addition compound 1·TMEDA was unambiguously identified
by solid-state 29Si NMR spectroscopy (Figure 1) and single
crystal X-ray diffraction (Figure 2). We found that 1·TMEDA is
poorly soluble in hydrocarbons such as pentane, hexane,
benzene, or toluene, and in diethyl ether and tetrahydrofuran
Reactivity of 1·TMEDA. Surprisingly, the disproportiona-
tion of TMEDA-supported 1 in CH Cl , as shown in Schemes
2
2
3
, 4, and 5, is quite different from the corresponding reaction of
1
and monodentate organyl-substituted amines NR (R = Me,
3
6
Et). We observed that dissolving of 1·TMEDA in CH Cl
resulted in an immediate reaction and after 1 min the mixture
2
2
+
became heterogeneous. Peaks were found in the MALDI mass
spectrum of the precipitate which could be assigned to the
oligochlorosilanes Si Cl (n = 4, 6, 8, 10) whereas the
n
2n
MALDI− mass spectrum of the solution revealed peaks of
2
−
2−
2−
oligochlorosilyl dianions [4a] , [4b] , [Si Cl ] , and
1
0
22
2−
[
Si Cl ] (Scheme 3). In addition we obtained single crystals
12
26
o f
[ M e 3 N C H 2 C H 2 N M e 2 ] 2 [ 4 a ]
3 2 2 2 2 2 2
a n d
[Me NCH CH NMe ] [4b] from the CH Cl extract. In this
context it should be noted that TMEDA reacts with CH Cl to
2
2
give the tetraalkylammonium chlorides 5 and 6, as shown in
10
Scheme 5. Both compounds are MeCl sources and therefore
t h e y a r e a b l e t o t r a n s f o r m T M E D A i n t o
[Me NCH CH NMe ]Cl. To prove this suggestion, the
2
9
Figure 1. Si CP/MAS NMR spectrum Cl SiSiCl ·TMEDA
(
3
3
1·TMEDA).
3
2
2
2
8
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Scheme 3. Main Reaction of Si Cl ·TMEDA (1·TMEDA)
Scheme 5. Generation of [Me NCH CH NMe ]Cl and the
2
6
3
2
2
2
with MeCl (80%) or with [Me NCH CH NMe ]Cl
MeCl Sources, the Tetraalkylammonium Chlorides 5 and 6,
by the Reaction of TMEDA with CH Cl
3
2
2
2
2
2
(
i) +TMEDA, -C H ClN .
6 15 2
behavior of 1·TMEDA toward MeI. In neat MeI the
decomposition of 1·TMEDA yielded MeSiCl along with
3
11
other oligochlorosilanes. The formation of MeSiCl indicates
3
an “ionic” mechanism in the disproportionation of 1·TMEDA
which was found in the pyridine-induced decomposition of 1.
Reaction of 1·TMEDA with Me SiN3 and subsequent
3
(
[
i) +MeCl/+[Me NCH CH NMe ]Cl, −SiCl , −TMEDA, at −78 °C;
3
2
2
2
4
treatment with LiMe yielded the silanimine dimer
4a]2 ([Si Cl ] , Xa = Cl); [4b] ([Si Cl ] , Xa = SiCl ).
−
2−
2−
2−
12
6
14
8
18
3
(Me SiNSiMe ) (9) and the silatetrazoline Me SiN-
2
3 2
2
12−14
SiMe3 × Me SiN3 (11)
together with a number of
3
Scheme 4. Side Reaction of Si Cl ·TMEDA (1·TMEDA) with
MeX (X = Cl, I) (20%)
2
6
unknown compounds. Both literature-known compounds, the
silanimine dimer 9 and the silatetrazoline 11, were identified by
NMR spectroscopy and gas chromatography mass spectrom-
etry (GC-MS). In this reaction obviously a heterolytic cleavage
−
of the Si−Si bond of 1·TMEDA with liberation of SiCl had
3
taken place. As depicted in Scheme 6, the transient silyl anion
−
SiCl , which had been formed, apparently underwent a
3
Staudinger-like reaction to give the silanimine 7 which
1
5
dimerizes to 8 or reacts with abundant Me SiN by [2 + 3]
3
3
14
cycloaddition to the silatetrazoline 10. A similar sequence was
found by the reactions of the silanides NaSiRtBu (R = tBu,
2
1
6,17
17,18
Ph)
with the silylazides tBu XSiN (X = halogen).
The
2
3
reaction of LiMe with dimeric silanimine 8 and the silatetrazo-
line 10 yielded the methyl derivatives 9 and 11, respectively
(
Scheme 6).
It is worth to mention that by heating the hexachlorodisilane
(i) +MeX (X = Cl, I), at −78 °C.
1
in the presence of 10 mol % 1·TMEDA, the neopentasilane 2
can be synthesized as well. It is remarkable that the disilane 1
was transformed to the neopentasilane 2 by a catalytical
amount of the adduct 1·TMEDA (Scheme 7).
reaction of 1·TMEDA with MeCl was also investigated. We
found that the TMEDA-supported disilane 1·TMEDA reacts
with MeCl, forming MeSiCl and the same products that had
The addition compound 1·TMEDA can be stored without
significant decomposition under an inert gas atmosphere for
several weeks at room temperature. However, by heating a
mixture of 1·TMEDA and THF to 50 °C we isolated the 1:1
3
been formed in the reaction of 1·TMEDA with CH Cl2
2
(
Scheme 3 and 4). The products were identified by MALDI
2
9
mass spectrometry, Si NMR spectroscopy, and X-ray
diffraction. The signal of MeSiCl in the Si NMR spectrum
2
9
adduct of SiCl with TMEDA. This result was also confirmed
3
4
of the reaction solution of 1·TMEDA with MeCl could be
by X-ray crystallography. Obviously, over the period of heating
recognized unambiguously. Now the question arises whether
the addition compound 1·TMEDA underwent a disproportio-
−
MeSiCl is formed from MeCl and SiCl by nucleophilic
nation reaction to give SiCl and dichlorosilylene. However, the
3
3
4
substitution or from MeCl and SiCl by silylene insertion. To
get more insight we decided to examine additionally the
dichlorosilylene seems to be instable in the presence of THF
and decomposes into several Cl−Si bonds containing
2
8
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Scheme 6. Reactivity of SiCl3− Generated from 1·TMEDA
Towards Me SiN
3
3
Figure 3. Calculated structures of meridional and facial isomers of
Cl SiSiCl ·TMEDA (1·TMEDA).
3
3
CCDC displays an octahedrally bonded Si atom as found in the
19
facial isomer of 1·TMEDA. In contrast to the solid-state
structure of meridional 1·TMEDA the N atoms of the chelate
ligand are cis-coordinated to the silyl substituent.
Crystals of [Me NCH CH NMe ] [4a] and
3
2
2
2 2
[
Me NCH CH NMe ] [4b] were grown from methylene
3 2 2 2 2
chloride at room temperature. X-ray structure analysis indicates
that both compounds contain dianions adopting an “inverse
20
sandwich” structure, however, with inverse polarity and
Scheme 7. Synthesis of the Perchlorinated Neopentasilane 2
+
Me NCH CH NMe as countercations (Figures 4 and 5). The
3
2
2
2
central structure motif of [Me NCH CH NMe ] [4a] and
3
2
2
2 2
[
Me NCH CH NMe ] [4b] consists of planar Lewis acidic Si
3 2 2 2 2 6
−
rings coordinated by Cl as Lewis base. This motif is similar to
those of a series of Si -ring compounds which have been
6
21,22
structurally characterized by Boudjouk and co-workers.
In
contrast to [Me NCH CH NMe ] [4b] the complex
3
2
2
2 2
[
Me NCH CH NMe ] [4a] has an inversion center in the
3 2 2 2 2
compounds. Therefore the poorly soluble complex
middle of the Si ring. It is interesting to note that for both
c o m p l e x e s , [ M e N C H C H N M e ] [ 4 a ] a n d
6
SiCl ·TMEDA could be crystallized as the only isolable
4
3
2
2
2
2
compound of this reaction.
[
Me NCH CH NMe ] [4b], the Si−Si distances in the Si
3
2
2
2 2
6
X-ray quality crystals of 1·TMEDA were obtained by gas-
phase diffusion of disilane 1 and TMEDA. Figure 2 represents
ring were 2.32−2.34 Å and feature very small deviations. The
Si−Si−Si angles in both compounds are nearly 120°, giving a
planar hexagonal Si ring. One of the most interesting features
the molecular structure of 1·TMEDA (monoclinic, P2 /n); the
1
6
selected bond lengths and angles are listed in the figure caption.
The solid-state structure of 1·TMEDA reveals one tetrahedrally
and one octahedrally bonded Si atom in which the six-
coordinate Si atom is chelated by TMEDA. The calculated
values of the meridional isomer are in good agreement with
those found in the solid-state structure (Table 1). The DFT
calculations indicate that the facial structure of 1·TMEDA is
energetically disfavored (Figure 3). In this context it should be
noted that structures of disilanes are rare which reveals one
tetrahedrally and one octahedrally bonded Si atom. The only
structurally characterized example which can be found in the
of these dianions is the strong interaction between the Si ring
6
and the apical halides. The contacts between the Si atoms and
the apical Cl− anions in both complexes are very similar
(
[
[
a v e r a g e d S i − C l c o n t a c t s : 3 . 0 2 0
M e N C H C H N M e ] [ 4 a ] , 3 . 0 1 4
Å
Å
i n
i n
3
2
2
2
2
Me NCH CH NMe ] [4b]). These distances are significantly
3
2
2
2 2
shorter than a typical Si−Cl van der Waals bond (3.9 Å) but
23
longer than the sum of the covalent radii (2.16 Å). Apparently
the Si−Cl interactions play a key role in the ring formation.
The formation of the unsymmetrically substituted ring in the
dianion [4b]2 can be explained by a SiCl insertion reaction in
−
2
the Si−Cl bond of Si Cl . It was found that Cl−SiSi bonds are
6
12
3
Table 1. Selected Averaged Bond Lengths [Å] for Disilanes
with One Tetrahedrally and One Octahedrally Bonded Si
Atom, Si Cl ·TMEDA (1·TMEDA) and Si Me Cl ·2,2′-
6
more favored than Cl−SiClSi for SiCl insertion. The silyl
2
2
anion SiCl3− can be considered as a dichlorosilylene donor
2
6
2
2
4
19
adduct and therefore as a SiCl source.
2
bipy
The addition compound SiCl ·TMEDA shown in Figure 6
4
c
d
Si−Si
Si −Cl
Si −Cl
(selected bond lengths see in the figure caption), crystallizes in
the monoclinic space group Cc. The octahedrally coordinated
a
b
mer-1·TMEDA
mer-1·TMEDA
2.405 Å
2.410 Å
2.560 Å
2.367 Å
2.188 Å
2.196 Å
2.172 Å
2.333 Å
2.062 Å
2.090 Å
2.110 Å
2.081 Å
Si atom in SiCl ·TMEDA is complexed to one TMEDA
4
b
molecule in a bidentate fashion as found in the solid-state
fac-1·TMEDA
fac-Si Me Cl ·2,2′-bipy ,
2
3,24
a
19
structures of 1·TMEDA and HSiCl ·TMEDA.
The Si−Cl
2
2
4
3
distances vary only little and are in the expected range and
a
b
c
d
X-ray structure analysis. Calculated. Octahedral. Tetrahedral.
comparable with those in 1·TMEDA and HSiCl ·TMEDA. In
3
8
602
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Inorganic Chemistry
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Figure 5. Solid-state structure of [Me NCH CH NMe ] [4b]
3
2
2
2 2
(
monoclinic, P2 /n). Displacement ellipsoids are drawn at the 50%
1
probability level. Selected bond lengths (Å) and angles (deg.): Si(1)−
Si(6) = 2.322(5), Si(1)−Si(2) = 2.340(5), Si(1)−Si(8) = 2.359(5),
Si(1)−Si(7) = 2.363(4), Si(2)−Cl(22) = 2.077(5), Si(2)−Cl(21) =
2.080(5), Si(2)−Si(3) = 2.320(5), Si(3)−Cl(32) = 2.075(5), Si(3)−
Cl(31) = 2.087(5), Si(3)−Si(4) = 2.327(6), Si(4)−Cl(42) = 2.074(4),
Si(4)−Cl(41) = 2.083(5), Si(4)−Si(5) = 2.309(5), Si(5)−Cl(52) =
Figure 4. Solid-state structure of [Me NCH CH NMe ] [4a]
3
2
2
2 2
(
monoclinic, P2 /n). Displacement ellipsoids are drawn at the 50%
1
probability level. Selected bond lengths (Å) and angles (deg.): Si(1)−
Cl(11) = 2.074(2), Si(1)−Cl(12) = 2.0772(19), Si(1)−Si(2) =
2.3174(17), Si(1)−Si(3A) = 2.3239(18), Si(2)−Cl(21) = 2.0754(18),
2
.079(5), Si(5)−Cl(51) = 2.081(5), Si(5)−Si(6) = 2.315(5), Si(6)−
Cl(61) = 2.075(4), Si(6)−Cl(62) = 2.081(5), Si(7)−Cl(71) =
.033(6), Si(7)−Cl(73) = 2.037(5), Si(7)−Cl(72) = 2.041(5),
Si(8)−Cl(81) = 2.023(5), Si(8)−Cl(82) = 2.038(5), Si(8)−Cl(83)
Si(2)−Cl(22) = 2.0783(17), Si(2)−Si(3) = 2.3260(18), Si(3)−Cl(31)
2.0676(17), Si(3)−Cl(32) = 2.0783(18), Si(3)−Si(1A) =
.3239(18); Cl(11)−Si(1)−Cl(12) = 102.27(9), Cl(11)−Si(1)−
=
2
2
Si(2) = 107.83(7), Cl(12)−Si(1)−Si(2) = 108.65(8), Cl(11)−
Si(1)−Si(3A) = 109.12(8), Cl(12)−Si(1)−Si(3A) = 108.49(7),
Si(2)−Si(1)−Si(3A) = 119.17(7), Cl(21)−Si(2)−Cl(22) =
=
2.045(5); Si(6)−Si(1)−Si(2) = 116.55(18), Si(6)−Si(1)−Si(8) =
1
1
1
08.28(18), Si(2)−Si(1)−Si(8) = 110.11(18), Si(6)−Si(1)−Si(7) =
10.25(17), Si(2)−Si(1)−Si(7) = 109.65(17), Si(8)−Si(1)−Si(7) =
00.85(17), Cl(22)−Si(2)−Cl(21) = 103.3(2), Cl(22)−Si(2)−Si(3)
1
1
1
1
=
=
02.08(7), Cl(21)−Si(2)−Si(1) = 108.21(7), Cl(22)−Si(2)−Si(1) =
07.17(7), Cl(21)−Si(2)−Si(3) = 107.64(7), Cl(22)−Si(2)−Si(3) =
08.63(7), Si(1)−Si(2)−Si(3) = 121.44(7), Cl(31)−Si(3)−Cl(32) =
02.31(7), Cl(31)−Si(3)−Si(1A) = 107.90(7), Cl(32)−Si(3)−Si(1A)
=
108.87(18), Cl(21)−Si(2)−Si(3) = 106.4(2), Cl(22)−Si(2)−Si(1)
107.7(2), Cl(21)−Si(2)−Si(1) = 106.46(18), Si(3)−Si(2)−Si(1) =
=
1
1
1
1
=
1
22.5(2), Cl(32)−Si(3)−Cl(31) = 100.7(2), Cl(32)−Si(3)−Si(2) =
06.7(2), Cl(31)−Si(3)−Si(2) = 110.5(2), Cl(32)−Si(3)−Si(4) =
08.43(19), Cl(31)−Si(3)−Si(4) = 109.6(2), Si(2)−Si(3)−Si(4) =
19.30(19), Cl(42)−Si(4)−Cl(41) = 101.6(2), Cl(42)−Si(4)−Si(5)
108.92(8), Cl(31)−Si(3)−Si(2) = 108.73(8), Cl(32)−Si(3)−Si(2)
108.27(7), Si(1A)−Si(3)−Si(2) = 119.37(6). Symmetry trans-
formations used to generate equivalent atoms: #1 −x + 1, −y + 2, −z +
1
.
110.7(2), Cl(41)−Si(4)−Si(5) = 108.1(2), Cl(42)−Si(4)−Si(3) =
09.4(2), Cl(41)−Si(4)−Si(3) = 107.9(2), Si(5)−Si(4)−Si(3) =
the end the related metric parameters of all three compounds
are very similar.
117.92(18), Cl(52)−Si(5)−Cl(51) = 101.4(2), Cl(52)−Si(5)−Si(4)
=
=
1
=
=
108.43(19), Cl(51)−Si(5)−Si(4) = 108.6(2), Cl(52)−Si(5)−Si(6)
107.4(2), Cl(51)−Si(5)−Si(6) = 107.11(19), Si(4)−Si(5)−Si(6) =
21.95(19), Cl(61)−Si(6)−Cl(62) = 102.6(2), Cl(61)−Si(6)−Si(5)
EXPERIMENTAL SECTION
■
108.5(2), Cl(62)−Si(6)−Si(5) = 106.93(18), Cl(61)−Si(6)−Si(1)
107.84(17), Cl(62)−Si(6)−Si(1) = 108.6(2), Si(5)−Si(6)−Si(1) =
General Considerations. All experiments were carried out under
dry argon or nitrogen using standard Schlenk and glovebox techniques.
Alkane solvents were dried over sodium and freshly distilled prior to
use. Benzene, toluene, and THF were distilled from sodium/
benzophenone. Benzene-d , toluene-d , and THF-d were distilled
1
=
20.92(18), Cl(71)−Si(7)−Cl(73) = 106.0(2), Cl(71)−Si(7)−Cl(72)
106.2(2), Cl(73)−Si(7)−Cl(72) = 104.8(2), Cl(71)−Si(7)−Si(1) =
115.5(2), Cl(73)−Si(7)−Si(1) = 110.6(2), Cl(72)−Si(7)−Si(1) =
112.9(2), Cl(81)−Si(8)−Cl(82) = 107.0(2), Cl(81)−Si(8)−Cl(83) =
105.5(2), Cl(82)−Si(8)−Cl(83) = 105.7(2), Cl(81)−Si(8)−Si(1) =
116.5(2), Cl(82)−Si(8)−Si(1) = 110.1(2), Cl(83)−Si(8)−Si(1) =
111.4(2).
6
8
8
from sodium/benzophenone and stored under a nitrogen atmosphere.
TMEDA was dried with LinBu. All other starting materials were
purchased from commercial sources and used without further
purification. Solution-state NMR spectra were recorded on a Bruker
DPX 250, a Bruker Avance 300, and a Bruker Avance 400. Solid-state
MAS NMR spectra were recorded on a Bruker Avance II WB 400
spectrometer equipped with a 4 mm MAS DVT triple resonance probe
in double resonance mode at Larmor frequencies of 293.8 and 78.03
MHz for H and 29Si, respectively. The 29Si CP/MAS spectra were
1
recorded at sample spinning rates of 8 kHz with a cross-polarization
25
step of 5 ms, 100 kHz Spinal6 and 1H decoupling during an
8
603
dx.doi.org/10.1021/ic301283m | Inorg. Chem. 2012, 51, 8599−8606

Inorganic Chemistry
Article
were performed at the microanalytical laboratories of the Universitat
Frankfurt and by the Microanalytical Laboratory Pascher. Mass
spectrometry was performed with a Fisons VG Platform II. GC-MS
measurements were performed with a Thermo Scientific Trace GC
Ultra/ITQ 900 MS (column: Machery-Nagel Optima-210MS, ID =
̈
0
.32 mm, film thickness = 0.5 μm, length = 25 m).
Synthesis of 1·TMEDA. A flask was charged with 1 (1.56 g, 5.8
mmol) in 10 mL of pentane to which TMEDA (0.51 g, 4.35 mmol)
was added at once. Immediately a colorless solid was deposited. The
colorless solid was filtered off and washed with pentane (2 × 10 mL).
Drying of the solid in vacuo yielded pure 1·TMEDA. Yield 1.49 g
(
89%).
2
9
1
·TMEDA. Si CP/MAS NMR: −0.5 (SiCl ), −163.4 (SiCl N ).
3
3
2
+
+
m/z (MALDI ) (%): 381 (100) [M] (correct isotope pattern). Elem.
Anal. Calcd for C H Cl Si C, 18.71%; H, 4.19%; N, 7.27%; Cl,
6
16
6
2
5
5.24%. Found: C, 18.62%; H, 4.13%; N, 7.95%; Cl, 54.20%.
Remark: Single crystals of 1·TMEDA as colorless needles were
obtained by gas-phase diffusion of hexachlorodisilane (6.25 g, 22.0
mmol) and TMEDA (2.71 g, 23.0 mmol) at room temperature.
Decomposition of 1·TMEDA in CH Cl . A flask was charged with
2
2
1
·TMEDA (1.0 g, 2.6 mmol) to which was added 10 mL of CH Cl .
2 2
+
Figure 6. Solid-state structure of one from two crystallographically
Immediately a colorless precipitate was formed. In the MALDI mass
spectrum of the precipitate peaks were found which could be assigned
to the oligochlorosilanes Si Cl (n = 4, 6, 8, 10) (m/z (MALDI ) (%):
independent molecules of SiCl ·TMEDA in the asymmetric unit
4
(
monoclinic Cc). Displacement ellipsoids are drawn at the 50%
+
probability level. Selected bond lengths (Å): Si(1)−N(12) = 2.083(9),
n
2n
+
3
95.8 (100, correct isotope pattern) [Si Cl ] , 593.6 (100, correct
Si(1)−N(11) = 2.104(9), Si(1)−Cl(13) = 2.176(4), Si(1)−Cl(12) =
4 8
+
isotope pattern) [Si Cl ] , 791.4 (100, correct isotope pattern)
6
12
2.178(4), Si(1)−Cl(14) = 2.182(4), Si(1)−Cl(11) = 2.186(4).
+
+
[
Si Cl ] , 989.2 (100, correct isotope pattern) [Si Cl ] . The
8 16 10 20
−
MALDI mass spectrum of the CH Cl solution revealed peaks of
2
2
acquisition time of 20 ms and a recycle delay of 3 s. The 29Si CP/MAS
oligochlorosilyl dianions [4a] , [4b] , [Si Cl ] , and [Si Cl ]
(m/z (MALDI ) (%): 336.5 (16) 335.5 (76) 334.5 (25) 333.6 (85)
332.5 (44) 331.6 (100) 330.7 (12) 329.6 (65) [Si Cl ] ([4a] ),
calcd for [Si Cl ] 337.7, 337.2, 336.7 (5) 336.2, 335.7 (12) 335.2,
6 14
2−
2−
2−
2−
10
22
12 26
−
spectrum of Cl SiSiCl ·TMEDA was acquired using 24576 transients
3
3
2
−
2−
and was indirectly referenced to trimethylsilane using the trimethylsilyl
6 14
26
2−
signal of tetrakis(trimethyl)silane at −9.86 ppm. Elemental analyses
Table 2. Crystal Data and Structure Refinement Parameters for 1·TMEDA, [Me NCH CH NMe ] [4a],
3
2
2
2 2
[
Me NCH CH NMe ] [4b], and SiCl ·TMEDA
3 2 2 2 2 4
1
·TMEDA
[Me NCH CH NMe ] [4a]
[Me NCH CH NMe ] [4b]
SiCl ·TMEDA
3
2
2
2
2
3
2
2
2
2
4
empirical formula
C H C N Si
C H Cl N Si
C H Cl N Si
C H C1 N Si
6
16 16
2
2
14 38 14
4
6
14 38 18
4
8
6
16
4
2
color
colorless
plate
colorless
colorless
colorless
block
shape
block
block
fw
385.09
927.32
1125.30
monoclinic
286.10
crystal system
space group
a, Å
monoclinic
monoclinic
monoclinic
P2 /n
1
P2 /n
1
P2 /n
1
Cc
8.5178(9)
16.642(2)
10.1630(8)
10.4876(10)
18.4868(16)
98.913(7)
1946.6(3)
2
12.382(2)
18.150(2)
20.566(3)
91.806(14)
4619.6
4
23.2626(13)
14.4338(7)
14.3613(8)
92.825(5)
4816.2(4)
16
b, Å
c, Å
10.5528(11)
90.255(8)
1495.9(3)
4
β, deg
3
volume, (Å )
Z
3
density (calcd.), Mg/m
1.710
1.582
1.618
1.578
−1
abs coeff μ(MoK ), mm
1.285
1.193
1.294
1.043
α
F(000)
784
944
2272
2368
crystal size, mm3
θ-range, deg
index ranges
0.1 × 0.06 × 0.05
2.69 to 27.69
0.27 × 0.27 × 0.25
3.64 to 25.71
−12 ≤ h ≤ 12
−12 ≤ k ≤ 12
−21 ≤ l ≤ 22
23116
0.1 × 0.1 × 0.02
3.45 to 25.78
−14 ≤ h ≤ 15
−22 ≤ k ≤ 22
−25 ≤ l ≤ 25
48470
0.28 × 0.26 × 0.22
3.25 to 25.85
−28 ≤h ≤ 28
−17 ≤ k ≤ 17
−17 ≤ l ≤ 17
8157
−10 ≤ h ≤ 11
−
−
21 ≤ k ≤ 21
13 ≤ l ≤ 13
no. of reflections collected
no. of independent reflections
R(int)
19798
3455
3652
8681
7637
0.0918
0.0876
0.1282
0.0984
Tmin, Tmax
0.9385 and 0.8822
3455/0/146
0.999
0.7546 and 0.7388
3652/0/172
1.148
0.9746 and 0.8815
8681/57/391
1.027
0.8030 and 0.7588
8158/2/471
1.988
no. of data/restraints/parameter
goodness of fit on F2
final R indices [I > 2σ(I)], R1, wR2
R indices (all data), R1, wR2
peak/hole e Å−
0.0692, 0.1149
0.1144, 0.1292
0.515 and −0.368
0.0729, 0,1158
0.0991, 0.1235
0.565 and −0.400
0.1128, 0.1906
0.2174, 0.2277
1.111 and −0.484
0.0918, 0.2194
0.0964, 0.2210
0.881 and −0.783
3
8
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dx.doi.org/10.1021/ic301283m | Inorg. Chem. 2012, 51, 8599−8606

Inorganic Chemistry
Article
3
34.7 (30) 334.2, 333.7 (56.5) 333.2, 332.7 (81) 332.2, 331.7, 331.2
mL, 0.67 mmol) was added at room temperature. Immediately a
colorless solid was deposited. The tube was sealed in vacuo and heated
(
(
(
4
4
100) 330.7, 330.2 (55) 329.7, 329.2, 328.7 (65); 436.5 (21) 435.5
43) 434.5 (30) 433.5 (30) 432.5 (80) 431.5 (100) 430.5 (42) 429.4
92) 427.5 (42) [Si Cl ] ([4b] ), calcd for [Si Cl ] 437.1, 436.6,
36.1 (5) 435.6, 435.1 (13) 434.6, 434.1 (28) 433.6, 433.1 (54) 432.6,
32.1 (82) 431.6, 431.2 (100) 430.6, 430.1 (96) 429.6, 429.1, 428.6
to 50 °C for 1 min. Crystals of SiCl ·TMEDA were obtained within 2
4
2
−
2−
2−
d at −30 °C. Yield 0.03 g (13%).
8
18
8
18
Thermolysis of 1·TMEDA in Si Cl . 1·TMEDA (0.06 g, 0.15
2
6
mmol) in neat Si Cl (0.81 g, 3.0 mmol) was heated to 55 °C for 15 h.
2
6
In the 29Si NMR spectrum of the reaction solution 2 can be assigned
as the major product of this reaction. After filtration and removal of all
volatile components in vacuo, 2 could be isolated as a colorless solid.
Yield: 0.34 g (80%).
(
5
100) 428.1, 427.6 (17), 536.3 (48) 534.3 (13) 533.4 (85) 532.4 (40)
31.4 (44) 530.4 (52) 529.4 (100) 527.3 (64) 525.4 (19) [Si Cl ] ,
2
−
10 22
2
−
calcd for [Si Cl ] 536.5, 536.0, 535.5 (5) 535.0, 534.5 534.0 (15),
10
22
5
5
6
32.5 532.0 (40) 531.5, 531.0 (57) 530.5, 530.0 (67) 529.5, 529.0,
28.5 (100) 528.0, 527.5, 527.0, 526.5 (47) 526.0, 525.5 (4); 633.2 −
23.9 [Si Cl ] , calcd for [Si Cl ] 632.4 − 623.5). At first single
X-ray Structure Determination. Data collections were per-
2
−
2−
formed on a Stoe-IPDS-II diffractometer, empirical absorption
12
26
12 26
2
7
crystals of [Me NCH CH NMe ] [4a] were grown from the CH Cl
correction using MULABS. The structures were solved with direct
28
3
2
2
2
2
2
2
2
extract (yield 15%). After 6 days at room temperature a second crop of
crystals of [Me NCH CH NMe ] [4b] were obtained (yield 5%).
However, the oligochlorsilanes Si Cl (n = 4, 6, 8, 10) could not be
separated.
Me NCH CH NMe ] [4a]. H NMR (CD CN, internal TMS): δ
methods and refined against F by full-matrix least-squares
29
calculation with SHELXL-97. Hydrogen atoms were placed on
ideal positions and refined with fixed isotropic displacement
parameters using a riding model. CCDC reference number: 884758
3
2
2
2 2
n
2n
1
[
(1·TMEDA), 884757 ([Me
([Me NCH CH NMe [4a]), and 793314 (SiCl
Computational Details. Geometry optimizations and harmonic
3
NCH
2
CH
2
NMe
2
]
2
[4b]), 884756
·TMEDA).
4
3
2
2
2
2
3
2
.23 (s, 6H, Me NCH ), δ 2.67 (m, 2H, Me NCH ), δ 3.20 (s, 9H,
3
2
2
2
]
2
2
2
2
2
29
1
Me NCH ), δ 3.52 (t, J = 6 Hz, 2H, Me NCH ). Si{ H}NMR
3
2
3
2
3
0
(
CD Cl , external TMS): δ −20.1. Elem. Anal. Calcd for
frequency calculations have been carried out with the Gaussian09
2
2
31
C H Cl N Si C, 18.13%; H, 4.13%; N, 6.04%. Found: C,
program employing the hybrid functional B3LYP(V), incorporating
32
1
4
38 14
4
6
1
7.49%; H, 4.15%; N, 5.74%.
Me NCH CH NMe ] [4b]. H NMR (CD CN, internal TMS): δ
the VWN5 parametrization as local correlation functional. The DFT
1
33
[
calculations were done in combination with the SVP basis set and
3
2
2
2
2
3
3
4
2
.23 (s, 6H, Me NCH ), δ 2.68 (m, 2H, Me NCH ), δ 3.20 (s, 9H,
the dispersion correction of Grimme (D2). Thermal and entropy
corrections were obtained from computed Hessians using the standard
procedures in Gaussian09.
2
2
2
2
29
1
Me NCH ), δ 3.55 (t, J = 6 Hz, 2H, Me NCH ). Si{ H}NMR
3
2
3
2
(
(
1
CD Cl , external TMS): δ 11.1 (SiCl ), δ −20.6 (2 × SiCl ), δ −20.8
2
2
3
2
SiCl ), n.o. (Si(SiCl ) Si ). Elem. Anal. Calcd for C H Cl N Si C,
2
3
2
2
14 38 18
4
8
4.94%; H, 3.40%; N, 4.98%. Found: C, 15.01%; H, 3.44%; N, 4.91%.
Decomposition of 1·TMEDA in MeCl. Methyl chloride (10 g,
98.2 mmol) and TMEDA (3.2 g, 27.0 mmol) were condensed on 1
ASSOCIATED CONTENT
Supporting Information
■
*
S
1
The table of X-ray parameters, atomic coordinates and thermal
parameters, and bond distances and angles. This material is
available free of charge via the Internet at http://pubs.acs.org.
(
7.8 g, 27.0 mmol) which was cooled by liquid nitrogen (−196 °C).
The mixture was stirred for 24 h at −78 °C. The reaction solution was
warmed up to room temperature over a 12 h period. After removing all
volatiles in vacuo, the residue was extracted in CH Cl . The MALDI
2
2
mass spectrum of the CH Cl solution revealed peaks of
2
2
AUTHOR INFORMATION
Corresponding Author
Fax: +49-69798-29260. E-mail: lerner@chemie.uni-frankfurt.
2−
2−
2−
2−
■
oligochlorosilyl dianions [4a] , [4b] , [Si Cl ] , and [Si Cl ]
10
24
12 26
whereas in the MALDI mass spectrum of the remaining insoluble
*
material peaks were found which could be assigned to Si Cl (n = 4, 6,
n
2n
8
, 10). The 29Si NMR spectrum of the methylene chloride solution
de.
2
−
revealed signals of MeSiCl and the oligochlorosilylanions [4a] and
3
Notes
2
−
[
4b] . X-ray quality crystals of [Me NCH CH NMe ] [4b] were
3 2 2 2 2
The authors declare no competing financial interest.
grown from the methylene chloride solution at room temperature
(
yield 20%).
ACKNOWLEDGMENTS
Decomposition of 1·TMEDA in MeI. Methyl iodide (0.5 mL)
■
was condensed on a mixture of 1·TMEDA (0.20 g, 0.52 mmol) and 1
This work was supported by the Beilstein Institute as part of
the NanoBiC research cooperative (project eNet).
mL of CD Cl which was cooled by liquid nitrogen (−196 °C). The
2
2
1
29
reaction mixture was warmed up to −78 °C. In the H NMR and Si
NMR spectrum of the reaction solution the signals of MeSiCl were
3
REFERENCES
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observable. The MALDI mass spectrum of the reaction mixture
revealed peaks of the oligochlorosilanes Si Cl (n = 4, 6, 8, 10).
■
1
1
n
2n
Thermolysis of 1·TMEDA in the Presence of Me SiN .
·TMEDA (0.15 g, 0.38 mmol) and Me SiN (0.41 g, 3.80 mmol)
(2) (a) Kaczmarczyk, A.; Urry, G. J. Am. Chem. Soc. 1960, 82, 751−
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3
3
1
3 3
in 5 mL of benzene was heated to 55 °C for 15 h. After cooling to
room temperature a solution of LiMe (5 mmol) in ether was added to
the benzene solution. After filtration, 9 and 11 were identified by H
NMR spectroscopy and by GC-MS (9, τ = 1.49 min; m/z (EI ): 275
1
+
+
+
+
[
M-Me] ; 11, τ = 2.02 min; m/z (EI ): 260 [M] ).
Synthesis of SiCl ·TMEDA. Generally SiCl ·TMEDA was
̈ ̈
(3) Meyer-Wegner, F.; Scholz, S.; Sanger, I.; Schodel, F.; Bolte, M.;
4
4
synthesized in preparative scale following this synthetic route: A
solution of SiCl (1.48 g, 8.71 mmol) in pentane (10 mL) was treated
at room temperature with a solution of TMEDA (1.01 g, 8.71 mmol)
in pentane (10 mL). After stirring for 1 h the solvent was removed
under reduced pressure, and SiCl ·TMEDA could be obtained as
colorless microcrystalline solid. The product was identified by powder
diffraction. Yield: 2.29 g (92%). Si CP/MAS NMR: −161.0
(
Wagner, M.; Lerner, H.-W. Organometallics 2009, 28, 6835−6837.
(4) Fleming, D. K. Acta Crystallogr. 1972, B28, 1233−1236.
4
(5) (a) Herzog, U.; Richter, R.; Brendler, E.; Roewer, G. J.
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Jeske, J.; Jones, P. G.; du Mont, W.-W. J. Organomet. Chem. 1994, 475,
4
̈
95−98. (c) Muller, L.-P.; du Mont, W.-W.; Jeske, J.; Jones, P. G. Chem.
2
9
Ber. 1995, 128, 615−619. (d) Martens, R.; du Mont, W.-W. Chem. Ber.
1993, 126, 1115−1117. (e) Martens, R.; du Mont, W.-W. Chem. Ber
SiCl ·TMEDA). Elem. Anal. Calcd for C H Cl Si C, 25.19%; H,
4 6 16 4
5
.64%; N, 9.79%. Found C, 25.25%; H, 6.05%; N, 9.90%.
̈
1992, 125, 657−658. (f) du Mont, W.-W.; Muller, L.; Martens, R.;
Thermolysis of 1·TMEDA in THF: A NMR-tube was charged with
(0.20 g, 0.74 mmol) in THF-d (0.5 mL), and TMEDA (0.08 g, 0.1
Papathomas, P. M.; Smart, B. A.; Robertson, H. E.; Rankin, D. W. H.
1
Eur. J. Inorg. Chem. 1999, 1381−1392.
8
8
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dx.doi.org/10.1021/ic301283m | Inorg. Chem. 2012, 51, 8599−8606

Inorganic Chemistry
Article
(
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4
(
(29) Sheldrick, G. M. SHELXL-97, A Program for the Refinement of
Crystal Structures; University of Gottingen: Gottingen, Germany, 1997.
̈ ̈
West, R.; Belyakov, A. V.; Verne, H. P.; Haaland, A.; Wagner, M.;
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4
(
1
work; NMR data of 1,4-bis(trichlorosilyl)-1,4-dihydropyridine:
H
3
NMR: δ 5.90 (2H, d, J = 7.9 Hz, R N−CHCHR), δ 4.38 (2H,
HH
2
3
dd, J = 8.1 Hz, R N−CHCHR), δ 2.55 (1H, t, J = 4.5 Hz,
2
HH
1
3
̈
Dannenberg, J. J.; Dapprich, S.; Daniels, A. D.; Farkas, O.;
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2
2
2
15
29
CHCHR), δ 33.0 (R CSiH); N NMR: δ 99.8; Si NMR: δ −1.5
2
(
Cl Si−C), δ −25,5 (Cl Si−N).
3
3
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(
6
(
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(
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(
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(
(
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(
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