Reactions of trimethylsiloxychlorosilanes with lithium metal - On the mechanism of the formation of trimethylsiloxysilyllithium compounds LiSiRR'(OSiMe3)

Article abstract of DOI:10.1016/j.jorganchem.2008.01.023

The reaction pathway for the formation of the trimethylsiloxysilyllithium compounds (Me₃SiO)RR′SiLi (2a: R = Et, 2b: R = ⁱPr, 2c: R = 2,4,6-Me₃C₆H₂ (Mes); 2a-c: R′ = Ph; 2d: R = R′ = Mes) starting fro

Full text of DOI:10.1016/j.jorganchem.2008.01.023

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Journal of Organometallic Chemistry 693 (2008) 1283–1291
www.elsevier.com/locate/jorganchem
Reactions of trimethylsiloxychlorosilanes with lithium metal – On
the mechanism of the formation of
trimethylsiloxysilyllithium compounds LiSiRR0(OSiMe3)
Joerg Harloff, Eckhard Popowski *
Institut fu¨r Chemie der Universita¨t Rostock, Albert-Einstein-Straße 3a, D-18051 Rostock, Germany
Received 18 October 2007; received in revised form 8 January 2008; accepted 14 January 2008
Available online 19 January 2008
Abstract
The reaction pathway for the formation of the trimethylsiloxysilyllithium compounds (Me3SiO)RR0SiLi (2a: R = Et, 2b: R = iPr, 2c:
R = 2,4,6-Me3C6H2 (Mes); 2a–c: R0 = Ph; 2d: R = R0 = Mes) starting from the conversion of the corresponding trimethylsiloxychloro-
silanes (Me3SiO)RR0SiCl (1a–d) in the presence of excess lithium in a mixture of THF/diethyl ether/n-pentane at ꢀ110 °C was
investigated.
The trimethylsiloxychlorosilanes (Me3SiO)RPhSiCl (1a: R = Et, 1b: R = iPr, 1c: R = Mes) react with lithium to give initially the tri-
methylsiloxysilyllithium compounds (Me3SiO)RPhSiLi (2a–c). These siloxysilyllithiums 2 couple partially with more trimethylsiloxychlo-
rosilanes 1 to produce the siloxydisilanes (Me3SiO)RPhSi–SiPhR(OSiMe3) (Ia–c), and they undergo bimolecular self-condensation
affording the trimethylsiloxydisilanyllithium compounds (Me3SiO)RPhSi–RPhSiLi (3a–c). The siloxydisilanes I are cleaved by excess
of lithium to give the trimethylsiloxysilyllithiums (Me3SiO)RPhSiLi (2). In the case of the two trimethylsiloxydisilanyllithiums
(Me3SiO)RPhSi–RPhSiLi (3a: R = Et, 3b: R = iPr) a reaction with more trimethylsiloxychlorosilanes (Me3SiO)RPhSiCl (1a, 1b) takes
place under formation of siloxytrisilanes (Me3SiO)RPhSi–RPhSi–SiPhR(OSiMe3) (IIa: R = Et, IIb: R = iPr) which are cleaved by
lithium to yield the trimethylsiloxysilyllithiums (Me3SiO)RPhSiLi (2a, 2b) and the trimethylsiloxydisilanyllithiums (Me3SiO)RPhSi–
RPhSiLi (3a, 3b). The dimesityl-trimethylsiloxy-silyllithium (Me3SiO)Mes2SiLi (2d) was obtained directly by reaction of the trimethyl-
siloxychlorosilane (Me3SiO)Mes2SiCl (1d) and lithium without formation of the siloxydisilane intermediate. Both silyllithium
compounds 2 and 3 were trapped with HMe2SiCl giving the products (Me3SiO)RR0Si–SiMe2H and (Me3SiO)RPhSi–RPhSi–SiMe2H.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords: Disilanes; Trisilanes; Si–Si bond cleavage; Trimethylsiloxysilyllithiums; Mechanism of formation
1. Introduction
with at least one aryl substituent on the silicon atom is
the reaction of the corresponding chlorosilanes RR0(aryl)
SiCl with lithium metal [1,6,10,11,13–15]. The functional-
ised silyllithium compounds (H)Ph2SiLi [16], (H)Mes2SiLi
[17,18]; (Et2N)n- Ph3ꢀnSiLi (n = 1, 2), (Et2N)MePhSiLi
[7,9–11,19,20]; (tBuO)2PhSiLi [7,9–11,21], [(Me3Si)2N]-
Me2ꢀnPhnSiLi (n = 1, 2) [22]; (Me3SiO)RPhSiLi (R = Me,
Et, Pr, Bu, Ph, Mes, Tip; Mes = 2,4,6-Me3C6H2, Tip =
2,4,6-(Me2CH)3C6- H2) and (Me3SiO)Mes2SiLi [23,24] can
be also synthesised by this method.
Organosilyllithium compounds are versatile reagents in
synthetic organic and organometallic chemistry. Syntheses,
properties and reactivity of the organosilyllithium
compounds and of the other alkali metal derivatives of
organosilicon compounds have been subject of several
reviews [1–12]. The most convenient method for the prepa-
ration of triorganosilyllithium compounds RR0(aryl)SiLi
i
t
In the reactions of the trimethylsiloxychlorosilanes
(Me3SiO)RPhSiCl (R = Me, Et, Pr, Bu, Ph, Mes) with
*
Corresponding author. Tel.: + 49 381 498 6380; fax: + 49 381 498
i
t
6382.
lithium metal in THF at ꢀ78 °C and in a mixture of
E-mail address: eckhard.popowski@uni-rostock.de (E. Popowski).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.01.023

1284
J. Harloff, E. Popowski / Journal of Organometallic Chemistry 693 (2008) 1283–1291
i
t
THF/diethyl ether/n-pentane (volume ratio 4:1:1) at
ꢀ110 °C (Trapp mixture) the silyllithium derivatives
(Me3SiO)RPhSiLi, Me3SiO(RPhSi)2Li and Me3SiRPhSiLi
have been obtained [23,24]. The stability of the trimethylsil-
oxysilyllithiums (Me3SiO)RPhSiLi is higher at ꢀ110 °C
than at ꢀ78 °C. The trimethylsiloxydisilanyllithiums
(Me3SiO)RPhSi–RPhSiLi are formed by bimolecular self-
condensation of trimethylsiloxysilyllithiums (Eq. (1)).
Et, Pr, Bu, Ph, Mes, Tip) and (Me3SiO)Mes2SiLi by
reductive lithiation of the corresponding trimethylsiloxy-
chlorosilanes proceeds via a disilane intermediate. This
assumption is supported by the results of the reactions of
the trimethylsiloxychlorosilanes (Me3SiO)RPhSiCl (R =
tBu, Mes) with lithium in a Trapp mixture at ꢀ110 °C.
When the reactions have been stopped at an early stage,
the disilanes (Me3SiO)RPhSi–SiPhR(OSiMe3) (R = tBu,
Mes) could be isolated. In many cases the trimethylsiloxy-
silyllithiums undergo self-condensation reactions affording
the trimethylsiloxydisilanyllithiums (see above). These
compounds could also be involved in the process of form-
ing the trimethylsiloxysilyllithiums.
78˚C
or
110°C
R
Me3SiO Si Li
Ph
R
R
R
Me SiO Si Li
Me3SiO Si Si Li
Ph Ph
+
+ LiOSiMe3
3
Ph
ð1Þ
In this paper we describe the results of our studies on the
mechanism of formation of the trimethylsiloxysilyllithium
compounds (Me3SiO)RR0SiLi (2a–d) by reductive lithia-
tion of trimethylsiloxychlorosilanes with lithium metal in
a Trapp mixture at ꢀ110 °C.
The trimethylsiloxysilyllithiums (Me3SiO)TipPhSiLi
and (Me3SiO)Mes2SiLi do not undergo such a self-
condensation.
t
Except for Bu3SiLi [8,25] the peralkylated silyllithium
compounds cannot be prepared by reaction of the corre-
sponding chlorosilanes with lithium metal [6,7,10,11]. The
t
a
b
c
d
attack of the chlorosilanes R3SiCl (R = alkyl except Bu)
R
R0
a
Et
Ph
iPr
Ph
Mesa
Ph
Mes
Mes
on lithium metal affords the homocoupling products only,
i.e. the disilanes R3Si–SiR3. Similarly, the alkyl(amino)
chlorosilanes (Et2N)nR3ꢀnSiCl (n = 1, 2; R = alkyl) [26]
and [(Me3Si)2N]Me2SiCl [22] as well as the trimethylsiloxy-
chlorosilane (Me3SiO)Me2SiCl [23] undergo only homo-
coupling reactions with lithium to give the corresponding
symmetrical disilanes.
Mes: 2,4,6-Me3C6H2.
2. Results and discussion
Although the reductive lithiation of chlorosilanes is
widely used for the synthesis of aryl-containing silyllithium
compounds [overview in Refs. 2,6,7,10,11], the course of
reaction has been investigated only occasionally [1,13–
15,20]. For the formation of phenyl-substituted silyllithi-
ums PhnMe3ꢀnSiLi (n = 1, 2, 3) the following reaction
pathway is discussed [1,6,7,10,11,13,14]: (i) rapid formation
of the silyllithium, (ii) reaction of the silyllithium with more
chlorosilane to give the disilane and (iii) symmetrical clea-
vage of the Si–Si bond of the disilane by lithium (Eq. (2)).
For the investigations of the mechanism of forming the
trimethylsiloxysilyllithiums (Me3SiO)RR0SiLi by reaction
of the corresponding trimethylsiloxychlorosilanes (Me3-
SiO)RR0SiCl (1a–d) with lithium metal the reaction
temperature ꢀ110 °C was chosen because both the yield
and the stability of the trimethylsiloxysilyllithium com-
pounds (Me3SiO)RR0SiLi (2a–d) are relatively high at this
temperature [23,24]. Furthermore, investigations are
limited to those transformations of the trimethylsiloxy-
chlorosilanes 1 with lithium in which the yields of com-
pounds from ambiguous chemical pathways are very
small [24]. That are the trimethylsilylsilyllithium deriva-
+2 Li
LiCl
+P hnMe3-nSiCl
LiCl
PhnMe3-nSiCl
n=1,2,3
PhnMe3-nSiLi
PhnMe3-nSi SiMe3-nPhn
+2 Li
i
tives Me3SiRPhSiLi (R = Et, Pr) for the reactions of
the trimethylsiloxychlorosilanes (Me3SiO)EtPhSiCl (1a)
and (Me3SiO)iPrPhSiCl (1b) with lithium as well as the
lithiumoxysilyllithiums (LiO)RMesSiLi (R = Ph, Mes)
and the disilane (Me3SiO)Mes2Si–SiMe3 for the reactions
of (Me3SiO)MesPhSiCl (1c) and (Me3SiO)Mes2SiCl (1d)
with lithium [24].
For monitoring the reactions after the reaction start
samples of the reaction mixture were taken out at certain
time intervals and quenched with dimethylchlorosilane.
The identification of the trapped products of lithiumsila-
nides as well as intermediates was carried out by spectro-
scopic methods and by using authentic compounds. The
changes in amounts of various species in the reaction mix-
tures were determined by GC. The peak areas in the gas
chromatograms serve as relative measure for the changes
in amounts of the several compounds.
2PhnMe3-nSiLi
ð2Þ
The disilanes can be isolated when the reactions are
stopped at an appropriate stage. The corresponding disi-
lane intermediates are also formed in the lithiation of
1-chloro-1,2,3,4-tetrahydro-1-phenyl-1-silanaphthalene [15]
and the diethylamino-substituted chlorosilane (Et2N)Ph2-
SiCl [20]. High steric shielding of the Si(Cl) atom in the
chlorosilane can inhibit the formation of the disilane [13–
15]. Thus, the reaction of chloro-tri(o-tolyl)silane with
lithium yields the silyllithium compound without forma-
tion of a disilane [1,13].
In Ref. [24] we have assumed that the generation of the
trimethylsiloxysilyllithiums (Me3SiO)RPhSiLi (R = Me,

J. Harloff, E. Popowski / Journal of Organometallic Chemistry 693 (2008) 1283–1291
1285
The reaction leading during the transformation of the
two alkyl-substituted trimethylsiloxychlorosilanes (Me3-
SiO)RPhSiCl (1a: R = Et, 1b: R = iPr), of the mesityl-
phenyl-trimethylsiloxy-chlorosilane (Me3SiO)MesPhSiCl (1c)
and of the dimesityl-trimethylsiloxy-chlorosilane (Me3SiO)-
Mes2SiCl (1d) with lithium (molar ratio Li: chlorosi-
lane = 4:1) are clearly different from each other. It is most
complex in the case of the reactions of the siloxychlorosil-
anes (Me3SiO)RPhSiCl (1a: R = Et, 1b: R = iPr) with
lithium. Beside the well-known trapping products (Me3SiO)-
RPhSi–SiMe2H (4a: R = Et, 4b: R = iPr) and (Me3SiO)-
RPhSi–RPhSi–SiMe2H (5a: R = Et, 5b: R = iPr) [24],
formed by the reaction of the lithiumsilanides (Me3SiO)-
RPhSiLi (2a: R = Et, 2b: R = iPr) and (Me3SiO)RPhSi–
5,0E+07
4,5E+07
4,0E+07
3,5E+07
3,0E+07
2,5E+07
2,0E+07
1,5E+07
1,0E+07
5,0E+06
0,0E+00
0
20
40
60
80
100
120
140
160
trct (min)
x
(Me3SiO)EtPhSiCl (1a)
Me3SiO(EtPhSi)2OSiMe3 (Ia)
Me3SiO(EtPhSi)3OSiMe3 (IIa)
(Me3SiO)EtPhSiSiMe2H (4a), trapping product of (Me3SiO)EtPhSiLi (2a)
Me3SiO(EtPhSi)2SiMe2H (5a), trapping product of Me3SiO(EtPhSi)2Li (3a)
Δ
Fig. 1. Course of reaction of the siloxychlorosilane (Me3SiO)EtPhSiCl (1a) with lithium metal in a Trapp mixture at ꢀ110 °C monitored by GC. For GC
measurements samples of the reaction mixture were quenched with HMe2SiCl.
4,5E+07
4,0E+07
3,5E+07
3,0E+07
2,5E+07
2,0E+07
1,5E+07
1,0E+07
5,0E+06
0,0E+00
0
20
40
60
80
100 120 140 160 180 200
rct (min)
t
x (Me3SiO)iPrPhSiCl (1b)
Me3SiO(iPrPhSi)2OSiMe3 (Ib)
Me3SiO(iPrPhSi)3OSiMe3 (IIb)
(Me3SiO)iPrPhSiSiMe2H (4b), trapping product of (Me3SiO)iPrPhSiLi (2b)
Me3SiO(iPrPhSi)2SiMe2H (5b), trapping product of Me3SiO(iPrPhSi)2Li (3b)
Δ
Fig. 2. Course of reaction of the siloxychlorosilane (Me3SiO)iPrPhSiCl (1b) with lithium metal in a Trapp mixture at ꢀ110 °C monitored by GC. For GC
measurements samples of the reaction mixture were quenched with HMe2SiCl.

1286
J. Harloff, E. Popowski / Journal of Organometallic Chemistry 693 (2008) 1283–1291
RPhSiLi (3a: R = Et, 3b: R = iPr) with HMe2SiCl, respec-
tively, the disilanes (Me3SiO)RPhSi–SiPhR(OSiMe3) (Ia:
R = Et, Ib: R = iPr) and trisilanes (Me3SiO)RPhSi–
SiPhR–SiPhR(OSiMe3) (IIa: R = Et, IIb: R = iPr) were
found in the quenched reaction mixtures.
In the Figs. 1 and 2 the changes of peak areas of the
trimethylsiloxychlorosilanes (Me3SiO)RPhSiCl (1a: R =
Et, 1b: R = iPr), the trapping products (Me3SiO) RPhSi–
SiMe2H (4a, 4b) of trimethylsiloxysilyllithiums (Me3SiO)-
RPhSiLi (2a, 2b), the trapping products (Me3SiO)RPhSi–
RPhSi–SiMe2H (5a, 5b) of trimethylsiloxydisilanyllithiums
Me3SiO(RPhSi)2Li (3a, 3b) as well as the disilanes Me3SiO
(RPhSi)2OSiMe3 (Ia, Ib) and the trisilanes Me3SiO
(RPhSi)3OSiMe3 (IIa, IIb) are shown in dependence of
the reaction time trct
.
The amount of the siloxychlorosilanes (Me3SiO)RPh-
SiCl (1a: R = Et, 1b: R = iPr) decreases continuously.
Until an approximately 90% consumption of the chlorosi-
lanes 1a, 1b the amounts of the trapping products
(Me3SiO)RPhSi–SiMe2H (4a, 4b) of (Me3SiO)RPhSiLi
(2a, 2b) and the trapping products (Me3SiO)RPhSi–
RPhSi–SiMe2H (5a, 5b) of (Me3SiO)RPhSi–RPhSiLi (3a,
3b) are constantly low. Only at a level of about 10% for
the chlorosilanes 1 (peak area in gas chromatogram) a con-
siderable increase of the amounts of 4 and 5, trapping
products of the silyllithium derivatives 2 and 3, is observed.
R
Me3SiO Si Cl
R'
R
R'
a
Et
iPr
Mes Ph
Mes Mes
Ph
Ph
b
c
d
1a-d
+ 2 Li - LiCl
Self-condensation
R
Me SiO Si Li (2)
+
R
Me3SiO Si Li
R'
R R
3
Ph
Me3SiO Si Si Li
Ph Ph
- LiOSiMe3
3a-c (R = Et, iPr, Mes)
2a-d (all)
Si-Si coupling
Si-Si coupling
+ (Me3SiO)RPhSiCl - LiCl
+ (Me3SiO)RPhSiCl - LiCl
1
1
R
R
Me3SiO Si OSiMe3
Me3SiO Si OSiMe3
Ph
Ph
2
3
Ia-c (R = Et, iPr, Mes)
IIa, IIb (R = Et, iPr)
Si-Si bond cleavage
Si-Si bond cleavage
+ 2 Li
+ 2 Li
R
R R
2 Me3SiO Si Li
Me3SiO Si Si Li
Ph Ph
+
2a, 2b
Ph
2a-c
3a, 3b
Self-condensation
- LiOSiMe3
3a-c
i
Scheme 1. Courses of reactions when the trimethylsiloxychlorosilanes (Me3SiO)RR0SiCl (1) (R = Et, Pr, Mes, R0 = Ph; R = R0 = Mes) are treated with
lithium metal (4 equiv.) in THF/Et2O/n-pentane (volume ratio 4:1:1) at ꢀ110 °C.

J. Harloff, E. Popowski / Journal of Organometallic Chemistry 693 (2008) 1283–1291
1287
Immediately from the beginning of the reaction of the chlo-
rosilanes 1 with lithium the formation of the disilanes
Me3SiO(RPhSi)2OSiMe3 (Ia, Ib) and the trisilanes
Me3SiO(RPhSi)3OSiMe3 (IIa, IIb) occurs. In the course
of reaction the amounts of the di- and trisilanes I and II
increase slowly, pass through maxima still before the sil-
oxychlorosilanes 1 are consumed completely and fall off
then relatively fast. With the decrease of amounts of the
intermediates I and II a clear increase of the amounts of
the trapping products (Me3SiO)RPhSi–SiMe2H (4) of tri-
methylsiloxysilyllithiums 2 and (Me3SiO)RPhSi–RPhSi–
(Me3SiO)RPhSiLi (R = Me, Ph) and the trimethylsiloxy-
disilanyllithiums Me3SiO(RPhSi)2Li (R = Me, Ph), which
were obtained beside other compounds in the reaction of
the corresponding trimethylsiloxychlorosilanes (Me3SiO)-
RPhSiCl (R = Me, Ph) with lithium at ꢀ110 °C in a Trapp
mixture [23,24]. Both types of compounds were clearly
proved in the reaction mixture before the trimethylsiloxy-
chlorosilanes 1 were consumed completely. In Table 1 the
yields of the disilanes Me3SiO(RPhSi)2OSiMe3 (I) and the
respective reaction times trct(Imax) between trimethylsiloxy-
chlorosilanes 1 and lithium metal when the peak areas of
the siloxydisilane intermediates I have maxima in the gas
chromatograms as well as the yields of the trisilanes
Me3SiO(RPhSi)3OSiMe3 (II) and of the trimethylsiloxy-
chlorosilanes 1 at these reaction times trct(Imax) are given.
Extended reaction times lead to complete decomposition
of the di- and trisilanes I and II (Table 1).
The reaction leading during the transformation of
mesityl-phenyl-trimethylsiloxy-chlorosilane (Me3SiO)Mes-
PhSiCl (1c) with lithium metal corresponds to that of
the transformation of the trimethylsiloxychlorosilanes
(Me3SiO)RPhSiCl (1a: R = Et, 1b: R = iPr) with lithium
(see Fig. 3; Table 1, Scheme 1) with the exception, that
no formation of a trisilane intermediate Me3SiO(Mes-
PhSi)3OSiMe3 and no cleavage by lithium take place.
The bimolecular reaction of the trimethyl-
siloxydisilanyllithium Me3SiO(MesPhSi)2Li (3c) and the
trimethylsiloxychlorosilane 1c is most probably suppressed
by high steric hindrance about the Si(Li) and Si(Cl)
atom.
SiMe2H (5) of trimethylsiloxydisilanyllithiums
3
is
connected. After complete transformation of the disilanes
I and trisilanes II the amounts of the trapping products 4
and 5 of 2 and 3 do not change any longer within the moni-
toring period considerably. These results are arguments for
the reaction pathways during the attack of excess lithium
metal on the trimethylsiloxychlorosilanes (Me3SiO)RPh-
SiCl (1a: R = Et, 1b: R = iPr) summarised in Scheme 1.
The trimethylsiloxychlorosilanes (Me3SiO)RPhSiCl (1)
react with lithium metal to give the corresponding trime-
thylsiloxysilyllithiums (Me3SiO)RPhSiLi (2a, 2b) initially.
Afterwards the trimethylsiloxysilyllithiums 2 react partially
with more siloxychlorosilanes 1 to give the disilanes
Me3SiO(RPhSi)2OSiMe3 (Ia, Ib) as well as react under
bimolecular self-condensation affording the siloxydisilanyl-
lithiums Me3SiO(RPhSi)2Li (3a, 3b). The trimethylsiloxy-
disilanyllithiums 3 then couple with the unconsumed
siloxychlorosilanes 1 to give the trisilanes Me3SiO(RPhSi)3
OSiMe3 (IIa, IIb). The disilanes and trisilanes Me3SiO-
(RPhSi)nOSiMe3 (I: n = 2, II: n = 3) are cleaved by lithium
to form the trimethylsiloxysilyllithiums (Me3SiO)RPhSiLi
(2a, 2b), and the trimethylsiloxydisilanyllithiums Me3SiO-
(RPhSi)2Li (3a, 3b) as well as the trimethylsiloxy silyllithi-
ums 2a, 2b, respectively. The trimethylsiloxysilyllithiums 2
undergo partially self-condensation to yield the trimethyl-
siloxydisilanyllithiums 3 [24].
The dimesityl-trimethylsiloxy-chlorosilane (Me3SiO)-
Mes2SiCl (1d) reacts with lithium to give the silyllithium
compound (Me3SiO)Mes2SiLi (2d) without formation of
the disilane intermediate Me3SiO(Mes2Si)2OSiMe3
(Scheme 1). Contrary to the reactions of the trimethylsil-
oxychlorosilanes (Me3SiO)RPhSiCl (1a: R = Et, 1b:
R = iPr, 1c: R = Mes; also R = Me, Ph) with lithium (see
above) the coupling reaction of the formed silylanion 2
with more chlorosilane 1 does not take place. The reason
for that is the high steric hindrance at the silicon centre
of 1d and 2d. The chlorosilanes (o-CH3C6H4)3SiCl [1,13]
Presumably, the respective disilanes Me3SiO(RPhSi)2-
OSiMe3 (R = Me, Ph) and trisilanes Me3SiO(RPhSi)3-
OSiMe3 (R = Me, Ph) are also involved as intermediates
in the formation of the trimethylsiloxysilyllithiums
Table 1
Yields of the 1,2-bis(trimethylsiloxy)disilanes Me3SiO(RPhSi)2OSiMe3 (I) and 1,3-bis(trimethylsiloxy)trisilanes Me3SiO(RPhSi)3OSiMe3 (II) in the
reaction mixture (formed in the reaction of siloxychlorosilanes (Me3SiO)RPhSiCl (1a–c and R = Me, Ph) with lithium in a Trapp mixture at ꢀ110 °C) at
the reaction times trct(Imax) when the peak area of the respective siloxydisilane intermediate I has a maximum in the gas chromatogram
Compound
a
b
c
R = Et
iPr
Mes
Me
Ph
(Me3SiO)RPhSiCl (1) (%)
8
6
16
9
26
Me3SiO(RPhSi)2OSiMe3 (I) (%)
Me3SiO(RPhSi)3OSiMe3 (II) (%)
39/15
20/10
34/12
10/7
22/5
–
12/5
29/14
33/9
10/7
Reaction time, trct
trct(Imax) (min)
90
120
45
150
150
270
65
120
16
60
a
trct(I/IIend
)
(min)
Yield determined by GC/yield of the isolated substance.
a
Reaction time when the intermediates I and II were consumed completely.

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J. Harloff, E. Popowski / Journal of Organometallic Chemistry 693 (2008) 1283–1291
5,0E+07
4,5E+07
4,0E+07
3,5E+07
3,0E+07
2,5E+07
2,0E+07
1,5E+07
1,0E+07
5,0E+06
0,0E+00
0
50
100
150
200
250
300
t
rct (min)
x
(Me3SiO)MesPhSiCl (1c)
Me3SiO(MesPhSi)2OSiMe3 (Ic)
(Me3SiO)MesPhSiSiMe2H (4c), trapping product of (Me3SiO)MesPhSiLi (2c)
Me3SiO(MesPhSi)2SiMe2H (5c), trapping product of Me3SiO(MesPhSi)2Li (3c)
Δ
Fig. 3. Course of reaction of the siloxychlorosilane (Me3SiO)MesPhSiCl (1c) with lithium metal in a Trapp mixture at ꢀ110 °C monitored by GC. For GC
measurements samples of the reaction mixture were quenched with HMe2SiCl.
and (Et2N)2PhSiCl [20] with high steric shielding of the
silicon centre react directly with lithium as well to yield
exclusively the corresponding silyllithium compounds.
The intermediates Me3SiO(RPhSi)2OSiMe3 (Ia: R = Et,
Ib: R = iPr, Ic: R = Mes; also R = Me, Ph) and
Me3SiO(RPhSi)3OSiMe3 (IIa: R = Et, IIb: R = iPr; also
R = Me, Ph) could be isolated, if the reactions of the sil-
oxychlorosilanes 1a–c, and (Me3SiO)RPhSiCl (R = Me,
Ph) with lithium in a Trapp mixture at ꢀ110 °C were
stopped at an early stage, i.e. at the reaction times trct(Imax),
when the respective siloxydisilane intermediate Me3SiO-
(RPhSi)2OSiMe3 (I) had a maximum of peak area in the
gas chromatogram.
vents used were dried by standard procedures and distilled
under argon. Me3SiCl and HMe2SiCl were treated with
small amounts of CaH2 to remove traces of dissolved HCl.
The lithium wire was purchased from Aldrich (about
0.01% Na) and converted into very thin plates for the
reactions.
The course of reaction of the siloxychlorosilanes 1a–d
with lithium metal was monitored by GC. Samples of the
reaction mixture (1.0 ml for GC and GC–MS, 2.0 ml for
NMR) were taken out at certain time intervals and
quenched with HMe2SiCl. Then the received reaction mix-
tures were analysed by GC and additionally, selected
samples of quenched mixtures by GC–MS and NMR.
For the identification and determination of reaction prod-
ucts the trimethylsiloxydisilanes (Me3SiO)RR0Si–SiMe2H
(4a: R = Et, 4b: R = iPr, 4c: R = Mes; 4a–c: R0 = Ph; 4d:
R = R0 = Mes), trapping products of the trimethylsiloxysi-
lyllithiums (Me3SiO)RR0SiLi (2a–d); the trimethylsiloxytri-
silanes (Me3SiO)RPhSi–RPhSi–SiMe2H (5a: R = Et, 5b:
R = iPr, 5c: R = Mes), trapping products of trimethylsil-
oxydisilanyllithiums (Me3SiO)RPhSi–RPhSiLi (3a–c) as
well as the 1,2-bis(trimethylsiloxy)disilanes (Me3SiO)-
RPhSi–SiPhR(OSiMe3) (Ia: R = Et, Ib: R = iPr, Ic: R =
Mes; also R = Me, Ph) and the 1,3-bis(trimethylsiloxy)tri-
3. Experimental
Mass spectra: Mass spectrometer Intectra AMD 402-3.
GC–MS: Coupling gas chromatograph Hewlett Packard
HP-5890-II – Mass spectrometer HP 59827 A. Gas chro-
matography: Hewlett Packard HP-5890-II, capillary
column HP1 (FS, non-polar) 25 m; Chrompack CP 9002,
capillary column WCOT (FS, non-polar) 24 m. NMR spec-
tra: Bruker ARX 400 (1H/13C/ 29Si NMR: 400.1/100.6/
79.5 MHz), Bruker ARX 250 (1H NMR: 250.1 MHz) or
Bruker ARX 300 (13C/29Si NMR: 75.5/59.6 MHz); solu-
tions of 30–50% in C6D6, reference C6D6, chemical shifts
refer to dTMS = 0.0 ppm. IR spectra: Nicolet 205 FT-IR,
liquids as films between KBr disks. Elemental analyses:
Leco Modell 932, absolute error 0.3%.
silanes
(Me3SiO)RPhSi–RPhSi–SiPhR(OSiMe3)
(IIa:
R = Et, IIb: R = iPr; also R = Me, Ph) were available as
pure substances [24, Section 3.2].
The compounds Ia–c, (Me3SiO)RPhSi–SiPhR(OSiMe3)
(R = Me, Ph), IIa, IIb and (Me3SiO)RPhSi–RPhSi–
SiPhR(OSiMe3) (R = Me, Ph) could be isolated by frac-
tional distillation and were identified and characterised
by their elemental analyses; mass, NMR and partially by
IR spectra.
The syntheses of the trimethylsiloxychlorosilanes 1a–d
and (Me3SiO)RPhSiCl (R = Me, Ph) are described in
Ref. [23] and [24]. All reactions were carried out in dry,
degassed solvents under an atmosphere of argon. The sol-

J. Harloff, E. Popowski / Journal of Organometallic Chemistry 693 (2008) 1283–1291
1289
The GC yields given in Table 1 are based on GC
investigations of all fractions (pure and/or mixed frac-
tions), which were obtained by work-up of the quenched
reaction mixtures, under using the pure compounds
Me3SiO(RPhSi)2- OSiMe3 (Ia: R = Et, Ib: R = iPr, Ic:
R = Mes; also R = Me, Ph) and Me3SiO(RPhSi)3OSiMe3
(IIa: R = Et, IIb: R = iPr; also R = Me, Ph) as standards.
The yields of the compounds isolated by distillation are
clearly lower than those determined by GC because of
the work-up of complex mixtures with very similar
compounds.
lithium metal and for the following trapping reactions with
Me3SiCl. By quenching with HMe2SiCl (see Section 3.1) it
could clearly be proved that the intermediates I, II and
Me3SiO(RPhSi)nOSiMe3 (n = 2, 3; R = Me, Ph) are
bis(trimethylsiloxy)-substituted di- and trisilanes and are
not possible silanolates such as Me3SiO(RPhSi)nOLi
(n = 2, 3) or LiO(RPhSi)nOLi (n = 2, 3). The correspon-
ding trapping products Me3SiO(RPhSi)nOSiMe2H (n = 2,
3) or HMe2SiO(RPhSi)nOSiMe2H (n = 2, 3) were not
found in the reaction mixtures. Thus Me3SiCl could also
be used as trapping agent. The work-up of the crude pro-
ducts is described separately. Some details of the reactions
are given in Scheme 1 and in Table 1. About the isolation
of the siloxydisilane (Me3SiO)MesPhSi–SiPhMes(OSiMe3)
(Ic) from the reaction of the trimethylsiloxychlorosilane
(Me3SiO)MesPhSiCl (1c) with lithium was reported in
Ref. [24].
3.1. Investigations of the course of reactions of the
trimethylsiloxychlorosilanes 1a–1d with lithium metal in a
Trapp mixture at ꢀ110 °C quenching of the reaction
mixtures with chlorodimethylsilane
On the analogies of the preparative work a general
procedure is given for the reactions of the trimethylsiloxy-
chlorosilanes 1a–d with lithium metal and for the quench-
ing of samples with HMe2SiCl. The time intervals of
sampling and the peak areas of selected products in the
gas chromatograms of the reaction mixtures are given in
Figs. 1–3.
3.2.1. General procedure
A mixture of 0.14 mol very thin lithium plates and 70 ml
Trapp mixture (THF/Et2O/n-pentane in volume ratio
4:1:1) was cooled down to ꢀ110 °C. To the respective mix-
ture 0.035 mol trimethylsiloxychlorosilane 1a–c and
(Me3SiO)RPhSiCl (R = Me, Ph), dissolved in 30 ml Trapp
mixture, was added dropwise within 15 min with vigorous
stirring. The reaction progress was monitored by GC of
samples quenched with HMe2SiCl. The vigorous stirring
was continued at ꢀ110 °C until the peak areas of the sil-
oxydisilane intermediates I and (Me3SiO)RPhSi–SiR-
Ph(OSiMe3) (R = Me, Ph) in the gas chromatograms of
the reaction mixture had a maximum. After the reaction
times trct(Imax) as given in Table 1 the excess lithium was
removed. Then 0.07 mol trapping agent Me3SiCl was
added to the solution of lithium silanides stirred at
ꢀ110 °C. The reaction mixture was warmed to room tem-
perature within 30 min and was allowed to react for 24 h
at the same temperature. Subsequently, the solvent and
excess trapping agent were removed under reduced pres-
sure at room temperature and 50 ml n-pentane were added
to the residue. The resulting suspension was filtered, and
the solvent of the filtrate was evaporated under reduced
pressure. The respective residue was distilled in vacuo
below 0.3 Torr. Beside the di- and trisilanes I, II and
Me3SiO(RPhSi)nOSiMe3 (n = 2, 3; R = Me, Ph) also the
compounds were obtained, which are given for the corre-
sponding reactions of trimethylsiloxychlorosilanes 1 and
(Me3SiO)RPhSiCl (R = Me, Ph) with lithium in Ref. [24]
and [23].
General procedure. A mixture of 0.14 mol very thin lith-
ium plates and 100 ml Trapp mixture (THF/Et2O/n-pen-
tane in volume ratio 4:1:1) was cooled down to
ꢀ110 °C. To the mixture 0.035 mol trimethylsiloxychlo-
rosilane 1a–1d without solvent was added within a few
seconds with vigorous stirring. The vigorous stirring was
continued at ꢀ110 °C. After the start of reaction samples
of the reaction mixture (in most cases 1 ml per sample)
were taken out at certain time intervals and quenched
with HMe2SiCl. The changes in amounts of the obtained
compounds in the reaction mixtures were determined by
GC. The changes in amounts of selected products (peak
areas in the gas chromatograms as measure) in depen-
dence of the reaction time trct are shown in Figs. 1–3.
After the end of reaction monitoring by GC the excess
lithium was removed. Then 0.07 mol trapping agent
HMe2SiCl was added to the reaction solution stirred at
ꢀ110 °C. The reaction mixture was warmed to room tem-
perature (20 °C) and was allowed to react for 24 h at this
temperature. After completion of quenching the work-up
of the reaction mixture was carried out as described in
Ref. [24]. The respective spectrum of products obtained
is also given in Ref. [24].
3.2. Isolation of the intermediates (Me3SiO)RPhSi–
SiPhR(OSiMe3) (Ia: R = Et, Ib: R = iPr, Ic: R = Mes;
also R = Me, Ph) and (Me3SiO)RPhSi–RPhSi–
SiPhR(OSiMe3) (IIa: R = Et, IIb: R = iPr; also R = Me,
Ph)
3.2.2. Isolation of the siloxydisilanes Ia and IIa from the
reaction of 1a with lithium
Distillation of the residue through a slit pipe column
(Fischer, Mikro-Spaltrohr-System D100) (30–144 °C/0.05
Torr) yielded three fractions (30–45 °C, 45–85 °C, 85–
142 °C), which contained mixtures of 1a, (Me3SiO)2SiEtPh,
Me3SiO(EtPhSi)nSiMe3 (n = 1, 2), Me3SiEtPhSiSiMe3 [24]
and Ia in different proportions. In the fourth fraction
On the analogies of the preparative work a general pro-
cedure is given for the reactions of the trimethylsiloxychlo-
rosilanes 1a–c and (Me3SiO)RPhSiCl (R = Me, Ph) with

1290
J. Harloff, E. Popowski / Journal of Organometallic Chemistry 693 (2008) 1283–1291
(143–144 °C/0.05 Torr) pure disilane Ia was found. In the
distillation residue the trisilanes IIa and minor Ia remained.
Anal. Calc. for C24H42O2Si4 (474.943): C, 60.69; H, 8.91.
Found: C, 60.56; H, 8.78%.
By distillation of the residue using a ball tube oven (Buchi,
¨
Kugelrohrofen GKR-51) the trisilane IIa was isolated
(185–190 °C/0.06 Torr).
1,3-Bis(trimethylsiloxy)-1,2,3-tri-iso-propyl-1,2,3-triphe-
nyl-trisilane (IIb): Yield: 0.5 g (7%). B.p.: 195–200 °C/
0.02 Torr. GC: Diastereomeric ratio 2:1:1. MS (EI,
70 eV): m/z (%) = 622 (4) [M]+, 607 (17) [MꢀMe]+, 579
1,2-Bis(trimethylsiloxy)-1,2-diethyl-1,2-diphenyl-disilane
(Ia): Yield: 1.2 g (15%). B.p.: 143–144 °C/0.05 Torr. GC:
Diastereomeric ratio 1.2:1. MS (EI, 70 eV): m/z
(%) = 446 (5) [M]+, 431 (3) [MꢀMe]+, 417 (31) [MꢀEt]+,
373 (91) [MꢀSiMe3]+, 223 (66) [Me3SiOSiEtPh]+, 195
(100), 135 (34), 73 (16) [SiMe3]+. 1H NMR: d = 0.05,
0.07 (s, Me3SiO, 18H); 0.80, 0.82 (q, H2C, 4H); 1.04, 1.07
(t, H3C, 6H); 7.10–7.67 (m, Ph, 10H) ppm. 13C NMR:
d = 2.1, 2.1 (Me3SiO); 7.3, 7.3 (CH3); 10.1, 10.1 (CH2);
128.1, 128.1, 129.4, 129.4, 133.8, 133.9, 139.3, 139.5 (Ph)
ppm. 29Si NMR: d = ꢀ8.54, ꢀ8.51 (SiEtPh); 8.6, 8.7
i
(26) [Mꢀ Pr]+, 533 (68) [MꢀOSiMe3]+, 237 (100)
[Me3SiOSiiPrPh]+, 193 (52) [Me3SiOSiiPrPhꢀC3H8]+, 135
1
(35), 73 (11) [SiMe3]+. H NMR: d = 0.14, 0.16, 0.19 (s,
Me3SiO, 18H); 0.84–1.81 (Me2C and HC, 21H); 7.11–
7.76 (m, Ph, 15H) ppm. 29Si NMR: d = ꢀ41.2, ꢀ41.0,
ꢀ40.4 (SiiPrSiPhSi); ꢀ0.1, ꢀ0.3, ꢀ0.6 (iPrSiPhO); 8.0,
~
8.1, 8.2 (OSiMe3) ppm. IR(film): m (SiOSi) 1055, d(CH3Si)
1252 cmꢀ1. Anal. Calc. for C33H54O2Si5 (623.224): C,
63.60; H, 8.73. Found: C, 63.69; H, 8.67%.
~
(OSiMe3) ppm. IR(film):
m
(SiOSi) 1058, d(CH3Si)
3.2.4. Isolation of the siloxydisilanes (Me3SiO)MePhSi–
SiPhMe(OSiMe3) and (Me3SiO)MePhSi–MePhSi–
SiPhMe(OSiMe3) from the reaction of
1251 cmꢀ1. Anal. Calc. for C22H38O2Si4 (446.891): C,
59.13; H, 8.57. Found: C, 58.94; H, 8.62%.
1,3-Bis(trimethylsiloxy)-1,2,3-triethyl-1,2,3-triphenyl-tri-
silane (IIa): Yield: 0.7 g (10%). B.p.: 185–190 °C/
0.06 Torr. GC: Diastereomeric ratio 2:1:1. MS (EI,
70 eV): m/z (%) = 580 (0.5) [M]+, 565 (3) [MꢀMe]+, 491
(8) [MꢀOSiMe3]+, 357 (6) [Me3SiO(EtPhSi)2]+, 223 (94)
(Me3SiO)MePhSiCl with lithium
Distillation of the residue through a Fischer slit pipe
column in the temperature range of 50–150 °C/0.2
Torr yielded four fractions (50–75 °C, 75–90 °C, 90–120
°C, 120–148 °C), which consisted of mixtures of (Me3SiO)-
MePhSiCl, (Me3SiO)2SiMePh, Me3SiO(MePhSi)nSiMe3
(n = 1, 2), Me3SiMePhSiSiMe3 [23] and Me3SiO(MePhSi)2-
OSiMe3 in different proportions. The fifth fraction (149–
150 °C/0.2 Torr) contained pure disilane Me3SiO(MePh-
Si)2OSiMe3. In the distillation residue the trisilanes
Me3SiO(MePhSi)3OSiMe3 and small amounts of Me3SiO-
(MePhSi)2OSiMe3 remained. By distillation of the residue
1
[Me3SiOSiEtPh]+, 195 (100), 135 (23), 73 (8) [SiMe3]+. H
NMR: d = 0.02, 0.03, 0.04 (s, Me3SiO, 18H); 0.76–1.19
(H3CH2C, 15H); 7.08–7.55 (m, Ph, 15H) ppm. 13C NMR:
d = 2.2, 2.2, 2.3 (Me3SiO); 3.1, 3.3, 3.7, 11.0, 11.1, 11.2
(CH2); 7.3, 7.3, 7.4, 10.3, 10.4, 10.6 (CH3); 127.9–139.8
(Ph) ppm. 29Si NMR: d = ꢀ46.3, ꢀ46.2, ꢀ46.1 (SiEt-
SiPhSi); ꢀ1.6, ꢀ1.42, ꢀ1.39 (EtSiPhO); 8.4, 8.4, 8.5
~
(OSiMe3) ppm. IR(film):
m
(SiOSi) 1058, d(CH3Si)
using a Buchi ball tube oven the trisilane Me SiO-
¨
3
1251 cmꢀ1. Anal. Calc. for C30H48O2Si5 (581.143): C,
62.00; H, 8.33. Found: C, 61.87; H, 8.41%.
(MePhSi)3OSiMe3 was isolated (150–153 °C/0.05 Torr).
1,2-Bis(trimethylsiloxy)-1,2-dimethyl-1,2-diphenyl-disi-
lane: Yield: 0.4 g (5%). B.p.: 149–150 °C/0.2 Torr. GC:
Diastereomeric ratio 1.1:1. MS (EI, 70 eV): m/z
(%) = 418 (1) [M]+, 403 (2) [MꢀMe]+, 345 (39)
[MꢀSiMe3]+, 209 (100) [Me3SiOSiMePh]+, 193 (43)
[Me3SiOSiMePhꢀCH4]+, 135 (39), 73 (20) [SiMe3]+. 1H
NMR: d = 0.08, 0.09 (s, Me3SiO, 18H); 0.508, 0.511 (s,
MeSi, 6H); 7.14–7.61 (m, PhSi, 10H) ppm. 13C NMR:
d = 0.9, 1.0 (MeSi); 2.20, 2.24 (Me3SiO); 128.07, 128.10,
129.42, 129.44, 133.59, 133.63, 140.1, 140.2 (Ph) ppm.
3.2.3. Isolation of the siloxydisilanes Ib and Ib from the
reaction of 1b with lithium
Distillation of the residue through a Fischer slit pipe col-
umn (45–158 °C/0.05 Torr) yielded three fractions (45–
60 °C, 60–80 °C, 80–156 °C), which consisted of mixtures
of 1b, (Me3SiO)2SiiPrPh, Me3SiO(iPrPhSi)nSiMe3 (n = 1,
2), Me3SiiPrPhSiSiMe3 [24] and Ib in different proportions.
The fourth fraction (157–158 °C/0.05 Torr) contained pure
disilane Ib. In the distillation residue the trisilanes IIb and
29Si NMR: d = ꢀ10.0, ꢀ9.9 (SiMePh); 9.3, 9.4 (OSiMe3)
ꢀ1
~
minor Ib remained. Distillation of the residue using a Buchi
ppm. IR(film): m (SiOSi) 1048; d(CH3Si) 1252, 1261 cm
.
¨
ball tube oven (195–200 °C/0.02 Torr) yielded pure trisi-
lane IIb.
Anal. Calc. for C20H34O2Si4 (418.837): C, 57.35; H, 8.18.
Found: C, 57.46; H, 8.36%.
1,2-Bis(trimethylsiloxy)-1,2-di-iso-propyl-1,2-diphenyl-di
silane (Ib): Yield: 1.0 g (12%). B.p.: 157–158 °C/0.05 Torr.
GC: Diastereomeric ratio 1.3:1. MS (EI, 70 eV): m/z (%) =
1,3-Bis(trimethylsiloxy)-1,2,3-trimethyl-1,2,3-triphenyl-
trisilane: Yield: 0.9 g (14%). B.p.: 150–153 °C/0.05 Torr.
GC: Diastereomeric mixture. MS (EI, 70 eV): m/z
(%) = 538 (2) [M]+, 523 (3) [MꢀMe]+, 465 (2)
[MꢀSiMe3]+, 329 (9) [Me3SiOSiMePhSiMePh]+, 313 (24)
[MꢀSiMePhOSiMe3ꢀCH4]+, 252 (35) [MꢀSiMePhOSi-
Me3ꢀPh]+, 209 (93) [Me3SiOSiMePh]+, 193 (100)
[Me3SiOSiMePhꢀCH4]+, 135 (39), 73 (11) [SiMe3]+. 1H
NMR: d = 0.04, 0.06, 0.08 (s, Me3SiO, 18H); 0.48, 0.49,
0.50, 0.53, 0.54, 0.57 (s, MeSiPh, 9H); 7.10–7.58 (m, PhSi,
i
474 (7) [M]+, 459 (4) [MꢀMe]+, 431 (100) [Mꢀ Pr]+, 401
(16) [MꢀSiMe3]+, 237 (52) [Me3SiOSiiPrPh]+, 193 (44)
[M/2ꢀC3H8]+, 135 (78), 73 (30) [SiMe3]+. 1H NMR:
d = 0.18, 0.19 (s, Me3SiO, 18H); 0.87, 0.89 (d, Me2C,
12H); 1.06, 1.22 (sept, HC, 2H); 7.13–7.70 (m, Ph, 10H)
ppm. 29Si NMR: d = ꢀ7.9, ꢀ7.4 (Si iPrPh); 7.9, 8.0 (OSiM-
ꢀ1
~
e3) ppm. IR(film): m (SiOSi) 1053, d(CH3Si) 1252 cm
.

J. Harloff, E. Popowski / Journal of Organometallic Chemistry 693 (2008) 1283–1291
1291
15H) ppm. 13C NMR: d = ꢀ8.5, ꢀ8.2, ꢀ7.9 (SiMeSiPhSi);
1.8, 1.9, 2.0 (MeSiPhO); 2.2, 2.3, 2.3 (Me3SiO); 128.0–140.7
(Ph) ppm. 29Si NMR: d = ꢀ52.2, ꢀ51.9, ꢀ51.7 (SiMe-
SiPhSi); ꢀ3.1, ꢀ3.0, ꢀ2.7 (MeSiPhO); 9.3, 9.4, 9.5 (OSiM-
1261 cmꢀ1. Anal. Calc. for C27H42O2Si5 (539.065): C,
60.16; H, 7.85. Found: C, 60.20; H, 8.02%.
1251 cmꢀ1. Anal. Calc. for C42H48O2Si5 (725.275): C,
69.55; H, 6.67. Found: C, 69.79; H, 6.83%.
Acknowledgement
~
e3) ppm. IR(film): m(SiOSi) 1049; d(CH3Si) 1248, 1252,
We thank the Fonds der Chemischen Industrie for the
material support of this work.
3.2.5. Isolation of the siloxydisilanes (Me3SiO)Ph2Si–
SiPh2(OSiMe3) and (Me3SiO)Ph2Si–Ph2Si–
SiPh2(OSiMe3) from the reaction of (Me3SiO)Ph2SiCl
with lithium
References
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324.
Distillation of the residue through a Fischer slit pipe col-
umn (70–140 °C/0.03 Torr) yielded several fractions (70–
140 °C), which obtained mixtures of (Me3SiO)Ph2SiCl,
(Me3SiO)2SiPh2,
Me3SiO(Ph2Si)nSiMe3
(n = 1,
2),
Me3SiPh2SiSiMe3 [23] and Me3SiO(Ph2Si)2OSiMe3 in
different proportions. In the distillation residue Me3SiO-
(Ph2Si)2OSiMe3, Me3SiO(Ph2Si)3OSiMe3 and small
amounts of Me3SiO(Ph2Si)2SiMe3 remained. By distillation
of the residue using a Buchi ball tube oven (180–250 °C/
¨
0.05 Torr) the disilane Me3SiO(Ph2Si)2OSiMe3 (200–205
°C/0.05 Torr) and the trisilane Me3SiO(Ph2Si)3OSiMe3
(245–250 °C/0.05 Torr) were isolated.
1,2-Bis(trimethylsiloxy)-1,1,2,2-tetraphenyl-disilane: Yield:
0.9 g (9%). B.p.: 200–205 °C/0.05 Torr. MS (EI, 70 eV):
m/z (%) = 542 (8) [M]+, 527 (2) [MꢀMe]+, 469 (34)
[MꢀSiMe3]+, 271 (80) [Me3SiOSiPh2]+, 193 (100) [M/2–
1
C6H6]+, 135 (20), 73 (6) [SiMe3]+. H NMR: d = 0.11 (s,
Me3SiO, 18H), 7.12–7.76 (m, Ph, 20H) ppm. 13C NMR:
d = 2.2 (Me3SiO); 128.1, 129.9, 135.1, 138.4 (Ph) ppm.
29Si NMR: d = ꢀ18.7 (SiPh2), 10.5 (OSiMe3) ppm. IR
(film): m (SiOSi) 1041, d(CH3Si) 1253 cmꢀ1. Anal. Calc.
~
for C30H38O2Si4 (542.977): C, 66.36; H, 7.05. Found: C,
66.30; H, 7.17%.
1,3-Bis(trimethylsiloxy)-1,1,2,2,3,3-hexaphenyl-trisilane:
Yield: 0.6 g (7%). B.p.: 245–250 °C/0.05 Torr. MS (EI,
70 eV): m/z (%) = 724 (5) [M]+, 709 (2) [MꢀMe]+, 574
(2) [MꢀSiMe3–Ph]+, 453 (9) [Me3SiOSiPh2SiPh2]+, 376
(45) [Me3SiOSiPh2SiPh]+, 271 (100) [Me3SiOSiPh2]+, 193
[19] K. Tamao, A. Kawachi, J. Am. Chem. Soc. 114 (1992) 3989.
[20] C. Strohmann, O. Ulbrich, D. Auer, Eur. J. Inorg. Chem. (2001) 1013.
[21] K. Tamao, A. Kawachi, Organometallics 15 (1996) 4653.
[22] I. Rietz, E. Popowski, H. Reinke, M. Michalik, J. Organomet. Chem.
556 (1998) 67.
[23] J. Harloff, E. Popowski, H. Fuhrmann, J. Organomet. Chem. 592
(1999) 1.
1
(92) [Me3SiOSiPh2–C6H6]+, 135 (9), 73 (5) [SiMe3]+. H
[24] J. Harloff, E. Popowski, H. Reinke, J. Organomet. Chem. 692 (2007)
1421.
[25] N. Wiberg, K. Amelunxen, H.-W. Lerner, W. Schuster, H. No¨th, I.
Krossing, M. Schmidt-Amelunxen, T. Seifert, J. Organomet. Chem.
542 (1997) 1.
NMR: d = 0.06 (s, Me3SiO, 18H), 7.11–7.82 (m, Ph,
30H) ppm. 13C NMR: d = 2.3 (Me3SiO); 128.0, 128.1,
129.1, 129.7, 134.6, 135.2, 137.5, 138.5 (Ph) ppm. 29Si
NMR: d = ꢀ48.5 (SiSiPh2Si), ꢀ12.0 (OSiPh2), 10.8
~
m (SiOSi) 1043, d(CH3Si)
(OSiMe3) ppm. IR(film):
[26] K. Tamao, A. Kawachi, Y. Ito, Organometallics 12 (1993) 580.