Electrochemical synthesis of symmetrical difunctional disilanes as precursors for organofunctional silanes

Article abstract of DOI:10.1016/j.jorganchem.2005.08.016

Difunctional disilanes of the general type XR₂SiSiR₂X (1-5) (X = OMe, H; R = Me, Ph, H) have been synthesized by electrolysis of the appropriate chlorosilanes XR₂SiCl in an undivided cell with a constant current supply and in the absence of any complexing agent. Reduction potentials of the chlorosilane starting materials derived from cyclic voltammetry measurements were used to rationalize the results of preparative electrolyses. Organofunctional silanes of the general formula MeO(Me ₂)SiC₆H₄Y (6a-c, 7) were subsequently obtained by the reaction of sym-dimethoxytetramethyldisilane (1) with NaOMe in the presence of p-functional aryl bromides BrC₆H₄Y (Y = OMe, NEt₂, NH₂).

Full text of DOI:10.1016/j.jorganchem.2005.08.016

Journal of Organometallic Chemistry 691 (2006) 105–110
www.elsevier.com/locate/jorganchem
Electrochemical synthesis of symmetrical difunctional disilanes
as precursors for organofunctional silanes
a,
a
a
b
b
*
Christa Grogger , Bernhard Loidl , Harald Stueger , Thomas Kammel , Bernd Pachaly
a
Institut f u¨ r Anorganische Chemie, Technische Universit a¨ t Graz, Stremayrgasse 16, A-8010 Graz, Austria
b
Wacker-Chemie GmbH, Johannes-Hess-Strasse 24, D-84489 Burghausen, Germany
Received 5 July 2005; accepted 3 August 2005
Available online 27 September 2005
Abstract
Difunctional disilanes of the general type XR
the appropriate chlorosilanes XR SiCl in an undivided cell with a constant current supply and in the absence of any complexing agent.
Reduction potentials of the chlorosilane starting materials derived from cyclic voltammetry measurements were used to rationalize the
results of preparative electrolyses. Organofunctional silanes of the general formula MeO(Me )SiC Y (6a–c, 7) were subsequently
obtained by the reaction of sym-dimethoxytetramethyldisilane (1) with NaOMe in the presence of p-functional aryl bromides BrC
Y = OMe, NEt , NH ).
2 2
SiSiR X (1–5) (X = OMe, H; R = Me, Ph, H) have been synthesized by electrolysis of
2
2
6 4
H
6
4
H Y
(
2
2
Ó 2005 Elsevier B.V. All rights reserved.
Keywords: Electrochemistry; Cyclic voltammetry; Disilanes; Organofunctional silanes
1
. Introduction
There exists a wide variety of methods for the formation
of silicon–carbon bonds involving the cleavage of Si–Si
bonds, such as the metathesis reaction of disilanes with
organic halides [3,4] or acid halides [5,6], the addition of
disilanes to unsaturated systems [7] or reactions via the
formation of silylenes [8] or silyl radicals [9]. Furthermore,
Due to their widespread applications, e.g. in rubber, coat-
ings, thermoplastics and adhesives, silanes of the general for-
mula X–(R )Si–R Y, with X and Y meaning two functional
0
2
groups, are of great industrial interest [1]. With their func-
tionality Y bound to an organic spacer they can undergo
chemical bond formation to organic substrates, whereas
the functional group X at the inorganic side of the molecule
provides a possible linkage to inorganic substrates. Thus, a
hybrid character is obtained for these so-called organofunc-
tional silanes (OFS). Usually, very specific synthesis routes
have been developed and patented for the large scale produc-
tion of OFS, e.g. aminopropyltriethoxysilane [2]. The aim of
our work in this field is to explore new, simple and more
general methods for the synthesis of OFS.
Si–Si bonds can be cleaved with strong bases such as
ꢀ
F
[10] or sodium methoxide. Sakurai and Kondo [11]
reported the cleavage of hexamethyldisilane with NaOMe
in strongly coordinating solvents such as HMPA, 1,3-di-
methyl-2-imidazolione or THF/crown ethers. Based on this
work, Watanabe et al. [12] cleaved 1,2-dimethoxytetrameth-
yldisilane with NaOMe and reacted the postulated silyl an-
ion intermediate with aromatic and aliphatic halides, thus
yielding phenyl or butyl substituted silanes (Eqs. (1) and (2)).
MeOMe
2
SiSiMe
2
OMe
NaOMe
ꢀ
þ
ƒ
ƒƒ! MeOMe
2
Si Na þ ðMeOÞ SiMe
2
ð1Þ
ð2Þ
2
ꢀ
þ
RX
MeOMe Si Na ƒƒ! MeOMe SiR
2
2
ꢀ
NaX
*
Corresponding author. Tel.: +433168738217; fax: +433168738701.
½
R ¼ Ph; n-Bu; X ¼ Cl; Brꢁ
E-mail address: christa.grogger@tugraz.at (C. Grogger).
0
022-328X/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.08.016

106
C. Grogger et al. / Journal of Organometallic Chemistry 691 (2006) 105–110
In order to utilize this approach for the synthesis of OFS
starting from commercially available precursors we were
seeking for convenient methods for the direct formation of
difunctional disilanes from chlorosilanes. Compounds like
H–(Si R )–H or MeO–(Si R )–OMe are usually made by
The results are summarized in Table 1. Not unexpectedly
product distribution and yield obtained after electrolysis
strongly depend on the nature of the functional group at-
tached to the silicon atom. Methoxy and amino substituted
chlorosilanes turned out to be nearly unreactive under the
2
4
2
4
substituent exchange starting from the appropriate 1,2-di-
chloro precursors [13]. Et N–(Si Me )–NEt and Me SiO–
reaction conditions applied. MeOMe SiCl affords only
2
traces of MeOMe SiSiMe OMe (1), while in the case of
2
2
4
2
3
2
2
(
Si R )–OSiMe can be prepared by coupling Et N–SiMe Cl
Et NMe SiCl and (Me Si) NMe SiCl, respectively, the
2 2 3 2 2
2
4
3
2
2
or Me SiO–SiMe Cl, respectively, with Li in THF [14,15].
unreacted starting materials were recovered nearly quanti-
tatively even after prolonged electrolysis times (4F instead
of 2). The attempt to couple Me SiCl selectively to the
3
2
Due to our own experience in the electrochemical formation
of silyl compounds [16] and based on a Japanese patent [17]
we expected the electrochemical coupling of appropriate
chlorosilanes to be a reasonable alternative.
2
2
corresponding disilane also failed. Insoluble poly(di-
methyl)silane is formed as the major product, ClMe SiSi-
2
Me Cl or soluble oligomers Cl(Me Si) Cl could not be
2
2
n
2
. Results and discussion
detected at all.
H-Si functional chlorosilanes were finally found to be
suitable substrates for the electrochemical conversion to
the corresponding 1,2-dihydrodisilanes, although the choice
of the supporting electrolyte turned out to be crucial in order
2
.1. Electrochemical synthesis of 1,2-difunctional disilanes
Although there exist several papers in the literature deal-
ing with the electrochemical formation of methylated or
phenylated disilanes [18–21], much less attempts have been
made to reduce chlorosilanes bearing one or more functional
groups on the silicon atom. Besides a patent claiming the for-
mation of 1,2-difunctional disilanes by the electrolysis of
to avoid extended side reactions. When HMe SiCl is electro-
2
lyzed in THF solution in the presence of Bu NBr as support-
4
ing electrolyte, not only the desired tetramethyldisilane (2)
but also significant amounts of hexamethyltrisilane and
octamethyltetrasilane are formed (Table 2). At first sight
rather inexplicable, the formation of these products is easy
to understand taking into account that quaternary ammo-
nium salts are known to catalyze the equilibration reaction
of HMe SiCl to Me SiH and Me SiCl (Eq. (4)) [20], which
0
0
chlorosilanes R R SiCl (R = Me, Ph, MeO, allyl, octyl) in
2
THF with various supporting electrolytes and two metal
electrodes [17], to the best of our knowledge only one publi-
cation exists dealing with the electrohemical Si–Si bond for-
mation starting from a functional chlorosilane: the
formation of 1,3-dihydrotrisilanes by co-electrolysis of
HMe SiCl and Ph SiCl with Mg electrodes in THF/LiClO
4
2
2
2
2
2
is an ideal co-substrate in the electroreduction giving rise to
the formation of oligosilanes (Eq. (5)).
2
2
2
THF=Bu4NBR
[
19].
Based on this literature, we electrolyzed several func-
HSiMe Cl ƒƒƒƒ ƒƒ ! H SiMe þ Cl SiMe
ð4Þ
2
2
2
2
2
2
HSiMe
2
Cl þ mCl
2
SiMe
2
tional chlorosilanes in THF in a simple undivided cell
equipped with a stainless steel cathode and a sacrificial
Mg anode (Eq. (3)).
electrolysis
ƒƒƒ ƒƒ ! HSiMe
2
½SiMe
2
ꢁ SiMe
2
H
ð5Þ
m
To overcome this undesired side reaction we tested several
other supporting electrolytes. Bu NBF , LiCl and even
2
XASiMe ACl
2
4
4
Mg anode
-
LiClO also favored the formation of tri- and tetrasilanes,
4
ƒ
ƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒƒ! XASiMe
2
SiMe
2
AX þ MgCl2
ð3Þ
stainless steel cathode 0:15 mA=cm2
but finally we found MgCl to be most suitable (compare
2
X ¼ Cl; MeO; NR ; H
Table 2).
2
Table 1
Electrolysis products and cyclovoltammetric data of functional chlorosilanes
a
p
b
b
Starting material
E
Disilane (% yield)
Other detected products (% yield)
c
Me
MeOMe
HMe
HPhMeSiCl
HPh SiCl
PhSiCl
NMe SiCl
NMe
2
SiCl
2
ꢀ3.03/ꢀ3.23
ꢀ3.3
–
(Me
2
Si)
n
(30) [16a]
d
d
2
SiCl
1 (traces)
2 (92)
3 (74)
4 (29)
5 (38)
–
–
Starting mat. (>90)
–
HPhMeSiOSiPhMeH (15)
HPh SiSiPh SiPh H (14), Ph
PhSiH (8), H SiPh
e
2
SiCl
ꢀ3.24
e
d
ꢀ2.99
e
d
2
ꢀ3.14
2
2
2
3
SiH (traces) Ph
(12), HPh SiOSiPh H (2) H
2
SiH
2
(49)
2
PhSiSiHPhSiPhH (7)
e
d
H
Et
(
2
ꢀ2.95
3
2
2
2
2
2
d
2
2
No signal
No signal
Starting mat. (>90)
Starting mat. (>90)
d
Me
3
Si)
2
2
SiCl
a
In CH
3
CN/Bu
4
NBPh
4
at m = 100 mV/s, referenced to ferrocene.
b
c
After electrolysis in THF/MgCl
Isolated yield.
Determined by GC/MS of crude product mixture.
Compare Section 4.
2
.
d
e

C. Grogger et al. / Journal of Organometallic Chemistry 691 (2006) 105–110
107
Table 2
Only with bromoanisole and bromodimethylaniline the
desired difunctional silyl substrates 6b and 6c could be ob-
tained in satisfying quantities. When p-chloro- or p-bro-
moaniline are reacted with NaOMe the preferred reaction
is H abstraction at the unprotected amino group thus lead-
ing to the N-silylated product 7. p-BrC H NO as well as
2
Product distribution obtained after electrolysis of HMe SiCl using
different supporting electrolytes
a
Supporting salt
Products (% yield)
Disilane
Trisilane
Others
Bu
Bu
4
NBr
40
20
60
10
100
1
50
25
32
40
–
Me
Me
Me
2
SiH
2
SiH
2
SiH
2
2
2
(10)
(5), HMe
(8)
6
4
2
4
NBF
4
2
SiF (50)
p-BrC H OH afford complex mixtures of unidentified reac-
6 4
tion products arising from the electrochemical instability of
LiCl
LiClO
4
2 2
HMe SiOSiMe H (50)
the NO or OH group, respectively. The reactions with
2
MgCl
2
–
t
2
p-BrC
6
H
4
OSiMe Bu and p-BrC H CH@CH also gave
6
4
2
a
Yields determined by H NMR of crude product mixture.
only poor yields of the corresponding organofunctional sil-
t
6 4
2
anes. In the case of p-BrC H OSiMe Bu the TBDMS pro-
tecting group is split off preferentially by the extremely
basic alkoxide, whereas with p-bromostyrene large quanti-
ties of styrene are formed along with the OFS. In general it
needs to be stated that yields strongly depend on the qual-
ity of the sodium methoxide used.
Watanabe et al. [12] also reported, that n-butyl halides
react according to Eqs. (1) and (2) to the corresponding
butylsilanes in rather good yields. In contrast to his work,
we found that butyl bromide and NaOMe give butylmethyl
ether (Eq. (6)), thus following the reaction pathway of the
well known Williamson ether synthesis [22].
Although less soluble than conventional supporting
electrolytes this low cost salt provides sufficient conductiv-
ity and prevents the equilibration reaction of HMe SiCl
2
most effectively. Thus, tetramethyldisilane (2) was formed
in yields up to 90%. As can be seen in Tables 1 and 2, other
hydrogen containing chlorosilanes can also be successfully
coupled electrochemically in the above mentioned THF/
MgCl electrolyte to get the corresponding disilanes 3–5.
2
Regarding product distribution, however, it is evident that
substituent scrambling and oligosilane formation becomes
more important in the presence of additional hydrogen
and phenyl substituents at the silicon atom (Table 1). Nev-
ertheless, compared to other methods for the preparation
of 1,2-dihydrodisilanes, electrolysis provides a versatile,
simple and successful alternative pathway.
NaOMe
n-buBr
NaOMe
n-buBr
MeOMe SiBu
MeOMe SiSiMe OMe
MeOBu
2
2
2
ð6Þ
2
.2. Synthesis of OFS from 2 by anionic cleavage
2.3. Cyclic voltammetry
Although 2 itself like Me SiSiMe does not react prop-
3
3
In order to obtain some information on the reduction
erly with NaOMe according to Eq. (1) it can be easily con-
verted to the 1,2-dimethoxy derivative 1 by methanolysis in
the presence of a catalyst [21]. 1 and several p-substituted
phenyl bromides were subsequently subjected to the reac-
tion sequence depicted in Eqs. (1) and (2) in order to inves-
tigate the tolerance of the method to various functional
groups attached to the phenyl ring. The results are summa-
rized in Scheme 1.
potentials and to better understand the results from pre-
parative electrolyses, a cyclic voltammetry study of the
starting chlorosilanes was performed. As the THF/MgCl2
solution which was used for the electrolyses did not give
any proper voltammograms due to insufficient conductiv-
ity, an alternative electrolyte had to be used. Thus, all mea-
surements were carried out in a CH CN/Bu NBPh
3
4
4
electrolyte. At the end of each measurement, ferrocene
FcH) was added as an internal standard and the reduction
(
potentials of the studied chlorosilanes were referenced to
ꢂ
E
¼ ðEox þ EredÞ=2 ¼ 0. It has to be taken into consider-
Me Me
FcH
ation that the solvent and especially the supporting electro-
lyte has some influence on the reduction potentials of
chlorosilanes [23]. The data from the cyclic voltammetry
study and the preparative electrolyses, nevertheless, look
consistent, although the absolute values for the reduction
potentials in CH CN/Bu NBPh may be actually different
H
Si Si H
(2)
Me
MeO Si
Me
Me Me
Br-C
6 4
H -Y
Y
NaOMe
MeOH
cat.
Y = H, -OMe, -NMe : (6a-c)
2
Me Me
3
4
4
MeO Si Si OMe (1)
from those in THF/MgCl2.
Me Me
As expected, all substrates exhibit a reduction wave in
the very cathodic region not reversible at scan rates in
the range of 20–500 mV/s (compare Table 1). The
aminosilanes Et NMe SiCl and (Me Si) NMe SiCl do
Me H
6 4 2
X-C H -NH
6 4
NaOMe Br-C H -Y
MeO Si
Me
N
X
NaOMe
2
2
3
2
2
not give any products as they obviously cannot be re-
duced electrochemically in the applied systems. MeOMe2-
SiCl is reduced at a very cathodic potential, already
Y = -OH, -NO : complex mixture
X = Cl, Br; (7)
2
Scheme 1.

108
C. Grogger et al. / Journal of Organometallic Chemistry 691 (2006) 105–110
within the limit of electrolyte degradation. As a conse-
quence, the corresponding disilane 1 is formed only in
very low yields. In contrast to this, the hydrochlorosil-
anes have reduction potentials placed conveniently within
the electrochemical window, although slightly more neg-
ative compared to the corresponding dichlorosilanes.
Therefore, if a dichlorosilane such as Me SiCl or
corded with a Kipp and Zonen BD8 flatbed recorder. The
three electrode system consisted of a platinum disk micro-
electrode (500 lm), a Pt counter electrode and a Ag/AgCl
reference electrode. 25 ml of a 0.1 M solution of Bu NBPh
4
4
in THF were introduced into the cell and the silane was
ꢀ
3
added in a concentration of 10 M. Ferrocene was added
at the end of each experiment and used as an internal stan-
dard. Thus, all potentials are quoted relative to the ferro-
cene/ferrocenium redox couple [29].
2
2
Ph SiCl is formed due to equilibration reactions from
2
2
the corresponding hydrochlorosilanes (HMe SiCl or
2
HPh SiCl, respectively) it will be reduced preferentially,
2
thus leading to the formation of oligosilanes as depicted
in Eqs. (4) and (5).
4.3. General electrolysis procedure
Constant current supply was afforded by a Wenking
STP 84 potentiostat. Electrolysis was carried out in an
undivided cell equipped with a magnesium anode in the
center and a cylindrical cathode, made of stainless steel,
around it. The supporting salt was dissolved in a concen-
tration of 0.2–0.5 mol/L in THF, and this solution was
introduced into the cell under a dry nitrogen atmosphere.
After addition of the silane, electrolysis was carried out
3
. Conclusions
The electrochemical coupling of monochlorosilanes
was shown to be a versatile method for the direct synthe-
sis of difunctional disilanes [24]. Especially 1,2-dihydro-
disilanes are easily accessible in good yields using
MgCl as supporting electrolyte in THF. The results of
2
2
preparative electrolyses are very well reflected by the
reduction potentials of the chlorosilane starting materials
derived from cyclic voltammetry measurements. The
merit of 1,2-difunctional disilanes for the synthesis of
organofunctional silanes, however, turned out to be
rather limited by the low tolerance of the subsequent
Si–Si-bond cleavage reaction to many functional groups.
Further studies concerning the application of electro-
chemical methods for the synthesis of OFS are currently
under investigation.
at a constant current density of 0.25 mA/cm until no more
starting material could be detected. The reaction was mon-
2
9
itored by Si NMR and GC/MS.
4.4. 1,2-Dimethoxytetramethyldisilane (1)
5.0 g (40 mmol) of (MeO)Me SiCl were electrolyzed at
2
15 mA for 7 days (2,4 F). All volatile compounds were
stripped off in vacuum (1 mbar), leaving a grayish white
residue which was completely soluble in water. NMR anal-
ysis of the volatile fraction showed, that only traces of 1
were formed and most of the starting material remained
unreacted.
4
. Experimental
2
9
4
.1. General procedures
MeOMe SiSiMe OMe: Si NMR (THF/ext. lock D O,
2 2 2
1
ext. TMS, ppm): d = 11.8. H NMR (CDCl , ext. TMS,
3
All reactions and other manipulations were carried out
ppm): d = 0.20 (s, 12H, SiCH ), 3.40 (s, 6H SiOCH ), both
3
3
+
using standard Schlenk techniques under an inert atmo-
sphere of nitrogen. All solvents were dried and distilled un-
der nitrogen prior to use. Commercial grade Me SiCl and
consistent with the literature [30]. MS m/z 178 [M] , 163
+
+
+
[M ꢀ CH ] , 133 [M ꢀ 3CH ] 89 [SiMe OMe] .
3
3
2
2
2
HMe SiCl (Wacker) as well as HPhMeSiCl, HPh SiCl and
4.5. Tetramethyldisilane (2)
2
2
H PhSiCl (Aldrich) were distilled prior to use. MeOMe SiCl
2
2
[
25], Et NMe SiCl [26], (Me Si) NMe SiCl [27] and 1 [28]
7.3 g (78 mmol) of HMe SiCl were electrolyzed at 15
2
2
3
2
2
2
were synthesized according to the literature procedures.
Bu NBr, MgCl and LiCl (Fluka ‘‘puriss. electrochem.
mA for 8 days (2,75 F). All volatile compounds were
stripped off in vacuum (1 mbar), leaving a grayish white
residue which is completely soluble in water. To remove
excess THF the mixture was distilled with a 1 m rotating
strip column until 7.55g of the crude product (including
4
2
grade’’) were dried in vacuum at 50 °C for several hours.
NMR spectra were recorded on a Bruker 300-MSL spec-
1
13
trometer; H NMR: 300.13 MHz; C NMR: 75.47 MHz;
2
9
1
29
Si NMR: 59.62 MHz. GC/MS analyses were made on
some residual THF) remained. H- and
Si NMR
a HP 5971/A/5890-II GC/MS coupling (HP 1 capillary
column, length 25 m, diameter 0.2 mm, 0.33 lm
polydimethylsiloxane).
analysis showed HMe SiSiMe H to be the only reaction
product. Thus, integration and calculation of the THF/
disilane ratio allowed to calculate the yield of 2 to be
2
2
4
.27 g (92%).
2
9
4
.2. Cyclic voltammetry
HMe SiSiMe H: Si NMR (THF/ext. lock D O, ext.
2
2
2
1
TMS, ppm): d = ꢀ39.0. H NMR (CDCl , ext. TMS,
3
All voltammograms were performed under an inert
ppm): d = 0.17 (12H, SiCH ), 3.75 (2H, SiH), both consis-
3
+
atmosphere at room temperature with a Wenking LB
5M potentiostat/Wenking POS 73 scan generator and re-
tent with the literature [31]. MS m/z 118 [M] , 103
[M ꢀ CH ] ,73 [Si(CH ) ] , 59 [M ꢀ Si(CH ) H] .
+
+
+
9
3
3 3
3 2

C. Grogger et al. / Journal of Organometallic Chemistry 691 (2006) 105–110
109
4
.6. 1,2-Dimethyl-1,2-diphenyldisilane (3)
.0 g (31.9 mmol) of HMePhSiCl were electrolyzed for 6
trolysis solution, approximately 90% of the starting materi-
als could be recovered.
5
days at 15 mA (5 F). After removal of all volatile
compounds the gray residue was extracted with pentane
applying ultrasound. Filtration and subsequent evapora-
tion of pentane yielded 2.85 g of the crude product contain-
ing 3 (85%) and HPhMeSiOSiPhMeH (15%) according to
4.10. General procedure for the reaction of the difunctional
disilanes with sodium methoxide
A solution of 0.50 g (2.8 mmol) of 1 in 10 ml of THF
was added drop wise to a suspension of 0.15 g (2.8 mmol)
of sodium methoxide and the equivalent amount of the or-
ganic halide in 20 ml of THF. As sodium halide precipi-
tated the reaction mixture became more and more turbid.
After no further conversion could be detected by GC/
MS, the reaction mixture was filtered, the solvent was evap-
orated and the resulting residue was analyzed using GC/
MS and NMR.
1
29
GC/MS-, H- and Si NMR analysis. (The high content
of siloxane was due to insufficiently dried MgCl ) This cor-
2
responds to a yield of 74 % of 3 based on HMePhSiCl.
2
9
HPhMeSiSiPhMeH: Si NMR (THF/ext. lock D O,
2
ext. TMS, ppm): d = ꢀ36.4, ꢀ36.8, consistent with the lit-
+
+
erature [32]. MS m/z 242 [M] , 197 [Si(C H ) (CH )] , 121
6
+
5 2
3
+
[
M ꢀ Si(C H ) (CH )H] , 105 [Si(C H )] .
6
5
3
6
5
4
.7. 1,1,2,2-Tetraphenyldisilane (4)
4.11. Methoxydimethylphenylsilane (6a)
5
.1 g (23.3 mmol) of HPh SiCl were electrolyzed for 10
0.44 g (2.8 mmol) of bromobenzene gave a mixture of
2
days (11,7 F) at 15 mA until all chlorosilane was consumed
reaction control by GC/MS). After removal of all volatile
40% of unreacted bromobenzene and 60% of 6a according
1
(
to GC/MS and H NMR.
1
compounds the gray residue was extracted with pentane
applying ultrasound. Filtration and subsequent evapora-
tion of the solvent yielded 3.92 g of an oily residue contain-
ing 4 (37%), HPh SiSiPh SiPh H (14%), Ph SiH (traces)
MeOMe SiPh: H NMR (CDCl , ext. TMS, ppm):
2
3
d = 0.52 (s, 6H, Si(CH ) ), 3.55 (s, 3H, SiOCH ), 7.21
3
2
3
2
9
(m, 5H, C H ). Si NMR (THF/ext. lock D O, ext.
6
5
2
TMS, ppm): d = 8.4, consistent with the literature [34].
2
2
2
3
1
29
+
+
+
and Ph SiH (49 %) according to GC/MS-, H- and Si
MS m/z 166 [M] , 151 [M ꢀ CH ] , 121 [M ꢀ 3CH ] .
2
2
3
3
NMR analysis. Thus, an overall yield of 4 of 29% based
on HPh SiCl was obtained.
4.12. p-(Methoxyphenyl)methoxydimethylsilane (6b)
2
2
9
HPh SiSiPh H: Si NMR (THF/ext. lock D O, ext.
2
2
2
TMS, ppm): d = ꢀ34.4; consistent with the literature [33].
0.52 g (2.8 mmol) of 4-bromoanisole gave 0.54 g of a
mixture of unreacted 4-bromoanisole (40%) and 6b (60%)
after a reaction time of 3 days according to GC/MS and
+
+
MS m/z 366 [M] ,259 [Si(C H ) ] , 183 [M ꢀ Si(C H ) H].
6
5 3
6
5 2
1
4
.8. 1,2-Diphenyldisilane (5)
H NMR.
1
MeOMe SiPhOMe: H NMR (CDCl , ext.TMS, ppm):
2
3
4
.28 g (19,5 mmol) of H PhSiCl were electrolyzed at 20
d = 0.38 (s, 6H, Si(CH ) ), 3.44 (s, 3H, SiOCH ), 3,84 (s,
3 2 3
2
2
9
mA. After 29 h (2.2 F) electrolysis was stopped and all
volatile compounds were removed. The resulting gray res-
idue was extracted with pentane applying ultrasound.
Filtration and subsequent evaporation of pentane yielded
3H, OCH ), 7.24 (dd, 4H, C H ). Si NMR (ext. lock
3 6 4
+
D O, ext. TMS, ppm): d = 8.9. MS m/z 196 [M] , 181
2
+
+
[M ꢀ CH ] , 151 [M ꢀ 3CH ] .
3
3
1
.73 g of an oily mixture containing 5 (71%), PhSiH3
4.13. p-N,N-Dimethylaminophenylmethoxydimethylsilane
(6c)
(
8%), H SiPh (12%), HPh SiOSiPh H (2%) and
2
2
2
2
1
H PhSiSiHPhSiPhH (7%) according to GC/MS-, H-
2
2
2
9
and Si NMR analysis. This corresponds to a yield of
8% of 5 based on H PhSiCl.
0.56 g (2.8 mmol) of 4-bromo-N,N-dimethylaniline gave
0.55 g of a mixture of unreacted 4-bromo-N,N-dimethylan-
iline (35%) and 6c 65%) after a reaction time of 4 days
3
2
2
9
H PhSiSiPhH : Si NMR (THF/ext. lock D O, ext.
2
2
2
1
TMS, ppm): d = ꢀ61.2; consistent with the literature [33].
according to GC/MS and H NMR.
+
+
+
1
MS m/z 214 [M] , 183 [Si(C H ) H] , 105 [Si(C H )] .
MeOMe SiPhNMe : H NMR (CDCl , ext. TMS,
6
5 2
6
5
2
2
3
ppm): d = 0.45 (s, 6H, Si(CH ) ), 3.05 (s, 6H, N(CH ) ),
3
2
3 2
4
.9. Attempts to electrolyze N,N-dimethylaminodimethyl-
3.55 (s, 3H, SiOCH ), 7.20 (dd, 4H, C H ). MS m/z 209
3 6 4
+
+
+
chlorosilane and N,N-bis(trimethylsilyl)aminodimethyl-
chlorosilane
[M] , 194 [M ꢀ CH ] , 164 [M ꢀ 3CH3]
134
3
+
[Si(CH ) C H ] .
3
2
6
4
1
8 mmol of Et NMe SiCl or (Me Si) NMe SiCl, respec-
4.14. Attempted synthesis of methoxydimethylsilylaniline
2
2
3
2
2
tively, were electrolyzed at 20 mA for 60 h (4 F). Reaction
2
9
control with GC/MS and Si NMR showed, that the start-
ing materials remained unreacted and no traces of the
wanted disilanes were formed. After distillation of the elec-
0.48 g (2.8 mmol) of 4-bromoaniline gave 0.63 g of a
mixture of 40% of unreacted 4-bromoaniline and 60% of
(N-4-bromophenylamino)methoxydimethylsilane (7) after

110
C. Grogger et al. / Journal of Organometallic Chemistry 691 (2006) 105–110
1
a reaction time of 22 h according to GC-MS and
H
[14] K. Tamao, A. Kawachi, Y. Ito, Organometallics 12 (2) (1993)
80.
[15] J. Harloff, E. Popowski, H. Fuhrmann, J. Organomet. Chem. 592
1999) 136.
5
NMR.
1
MeOMe SiNHPhBr: H NMR (CDCl , ext. TMS,
2
3
(
ppm): d = 0.35 (bd, 6H, Si(CH ) ), 3.45 (s, 3H, SiOCH ),
3
2
3
[16] (a) C. Jammegg, S. Graschy, E. Hengge, Organometallics 13 (1994)
+
+
6
2
.95 (dd, 4H, C H ) MS m/z 261 [M] , 246 [M ꢀ CH ] ,
2397;
6
4
3
+
+
29 [M ꢀ CH (OCH )] 165[M ꢀ CH Br] .
(b) Ch. Grogger, H. Fallmann, G. F u¨ rpaß, H. St u¨ ger, J. Organomet.
Chem. 665 (2003) 186;
3
3
3
(
c) H. Fallmann, Ch. Grogger, in: N. Auner, J. Weis (Eds.),
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