Synthesis of 1,1-bis(silyl)-1-alkene derivatives bearing Si-H functional groups via Peterson protocol

Article abstract of DOI:10.1016/j.jorganchem.2008.08.035

Various aromatic aldehydes were converted to one-carbon elongate 1,1-bis(silyl)-1-alkene derivatives bearing Si-H functional and reactive groups in a convenient one-pot operation via the Peterson protocol. Then poly(styrene) and poly(α-methylstyrene) (I{cyrillic, ukrainian}&II) random homopolymers were synthesized by solution free radical polymerization at 70(±1) °C using α,α′-azobis(isobutyronitrile) (AIBN) as an initiator. The aldehyde group is introduced by direct electrophilic substitution of polymers I{cyrillic, ukrainian} and II. This formylation reaction was conducted in two different solvents: dichloromethane (CH₂Cl₂) and nitrobenzene (PhNO₂). The results indicate that PhNO₂ appeared to be a more suitable solvent for such an aldehyde functionalization of the polymers. The formylated polymers (I_CHO, II_CHO) were then converted to Si-H functionalized polymers (I_Si-H, II_Si-H) via reaction with tris(dimethylsilyl)methyllithium, (HMe₂Si)₃CLi.

Full text of DOI:10.1016/j.jorganchem.2008.08.035

Journal of Organometallic Chemistry 693 (2008) 3622–3626
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis of 1,1-bis(silyl)-1-alkene derivatives bearing Si–H functional groups via
Peterson protocol
*
Kazem D. Safa , Akbar Hassanpour, Shahin Tofangdarzadeh
Organosilicon Research Laboratory, Faculty of Chemistry, University of Tabriz, 51664 Tabriz, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 5 August 2008
Received in revised form 25 August 2008
Accepted 27 August 2008
Available online 3 September 2008
Various aromatic aldehydes were converted to one-carbon elongate 1,1-bis(silyl)-1-alkene derivatives
bearing Si–H functional and reactive groups in a convenient one-pot operation via the Peterson protocol.
Then poly(styrene) and poly(
a
-methylstyrene) (I&II) random homopolymers were synthesized by solu-
tion free radical polymerization at 70( 1) °C using
a
,
a0-azobis(isobutyronitrile) (AIBN) as an initiator.
The aldehyde group is introduced by direct electrophilic substitution of polymers I and II. This formyla-
tion reaction was conducted in two different solvents: dichloromethane (CH2Cl2) and nitrobenzene
(PhNO2). The results indicate that PhNO2 appeared to be a more suitable solvent for such an aldehyde
functionalization of the polymers. The formylated polymers (ICHO, IICHO) were then converted to Si–H
functionalized polymers (ISi–H, IISi–H) via reaction with tris(dimethylsilyl)methyllithium, (HMe2Si)3CLi.
Ó 2008 Elsevier B.V. All rights reserved.
Keywords:
Tris(dimethylsilyl)methane
Peterson olefination
1,1-Bis(silyl)-1-alkenes
Si–H functional group,
functionalized poly(styrene)
1. Introduction
reaction, there are a few reports about the preparation of 1,
1-bis(silyl)-1-alkenes in the literature from this protocol [17].
1,1-Dimetalated-1-alkenes constitute an important class of
organometallic reagents which are currently widely used as poten-
tial intermediates in the organic and organometallic synthesis.
Among the most notable and commonly employed gem-diorgano-
metallics, the 1,1-bis(silyl)-1-alkenes are of unique importance.
Their use as precursors for the preparation of ketones as well as
variety of important organosilicon intermediate such as acylsil-
anes, epoxysilanes, 1-halovinylsilanes, silylenolethers, (E)-alke-
neylsilanes, silylenolacetates etc., stimulate interest in their
synthetic availability [1–8].
Introduction of functional groups on a polymer chain results in
modification of many properties of polymer such as thermal and
mechanical properties, gas permeabilities, polarity, solubility,
adhesion, etc. For example, it is known that the polymers contain-
ing tris(trimethylsilyl)methyl, (Me3Si)3C–, group have excellent
permeability. Therefore, the preparation of macromolecules con-
taining the organosilyl groups and studying their properties are a
novel field in polymer and silicon chemistry [9–13].
However, as far as we are aware, there has hitherto been no ref-
erences in the literature about the preparation of 1,1-bis(silyl)-
1-alkenes containing Si–H functional and reactive group by this
method. Herein, we employed the Peterson protocol to synthesize
1,1-bis(silyl)-1-alkenes bearing Si–H groups. Moreover, we carried
out the same reaction on the side chain of formylated styrene
polymers to synthesize functionally new macromolecules con-
taining Si–H groups.
2. Results and discussion
Recently, we have embarked on a program directed towards the
development of tris(dimethylsilyl)methyllithium, (HMe2Si)3CLi,
reaction for the generation of synthetically useful organosilicon
compounds [18,19]. We paid particular attention to epoxides be-
cause of their ring opening reaction and the potentially coordina-
tion of the produced alkoxide group to silicon, thereby enabling
the facile cyclization. For example, when (HMe2Si)3CLi reacts with
ethylene oxide in THF at ꢀ5 °C, it seems that because of the exis-
tence of the Si–H bond, an intramolecular alkoxylation takes place
and the cyclic product forms (Scheme 1) [18]. In ongoing effort to
exploit (HMe2Si)3CLi, we envisioned that appending (HMe2Si)3CLi
ligand to carbonyl group should led to interesting compounds.
The starting point of the work was the compound tris(dimethyl-
silyl)methane, (HMe2Si)3CH, which was made in 60% yield from
HMe2SiCl, CHBr3 and Mg in THF. (HMe2Si)3CH was then metallated
By using the Peterson olefination reaction, synthetically useful
vinylsilanes can be prepared by the reaction of bis(silyl)methyl
metal with carbonyl compounds using the direct addition–elimi-
nation process [14–16]. Despite many useful studies of Peterson
olefination reaction over the conventional carbonyl olefination
* Corresponding author. Tel.: +98 411 3393124; fax: +98 411 3340191.
E-mail address: dsafa@tabrizu.ac.ir (K.D. Safa).
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.08.035

K.D. Safa et al. / Journal of Organometallic Chemistry 693 (2008) 3622–3626
3623
HMe2Si
HMe2Si
HMe2Si
SiMe2H
O
HMe2S i
Me
+
HMe2Si
Li
H
H
Me
H
Si
H
Si
SiMe2H
O
H
-
O
Me
Me
Scheme 1. Preparation of silacyclopantane via the reaction of (HMe2Si)3CLi with ethylene oxide.
with lithiumdiisopropylamide (LDA) during 6 h and gave (HMe2-
Si)3CLi [20].
)
(
)
(
n
)
(
HMe2SiCl þ CHBr3 þ Mg ! ðHMe2SiÞ CH L!DAðHMe2SiÞ CLi
m1
m2
H2O
Cl2CHOMe
SnCl4
3
3
(HMe2Si)3CLi reacts with non-enolisable aldehydes such as benzal-
dehyde, o-chloro, p-chloro, 2,6-dichloro, o-bromo, p-bromo, and m-
fluoro benzaldehyde with the formation of carbon–carbon double
bond. This method of preparing functionalized silanes is limited
by the readiness with which (HMe2Si)3CLi abstracts a proton, if
one is available, rather than attacking the carbonyl group. The Pet-
erson reactions readily take place and give the corresponding 1,1-
bis(silyl)-1-alkene derivatives.
We postulated that when (HMe2Si)3CLi is treated with carbonyl
group, it initially forms the alkoxide intermediate (A), then because
of the presence of the Si–H bond, an intramolecular alkoxide attack
takes place and gives (B). It seems likely that the cyclic intermedi-
ate (B) is unstable and swiftly converts to 1,1-bis(silyl)-1-alkene
with the elimination of Me2SiO (Scheme 2).
We were also interested in carrying out analogous reactions
with polymers containing carbonyl groups in the side chains. For
this reason poly(styrene) and poly(a-methylstyrene) (I, II) were
formylated by methyl dicholromethyl ether (Cl2CHOMe) in the
presence of tin (IV) chloride (SnCl4) [21]. We found that solvent
plays an important role in the completion of the formylation reac-
tion. When CH2Cl2 is employed as a solvent, the 1H NMR spectrum
shows two signals for OMe and CHCl which indicates that the
hydrolysis step of the intermediate (C) is not complete, probably
due to insolubility of the resulted polymer in CH2Cl2 (Scheme 3).
II
Cl
MeO
H
(
(C)
)
)
(
(
)
)
(
m2
m1
m2
m1
(HMe2Si)3CLi
C
H
H
O
Me
Me
Me
C
Si
Si
Me
IICHO
IISi-H
H
H
Scheme 3. Preparation of formylated polymer IICHO and its conversion to functional
polymer IISi–H
.
HMe2Si
HMe2Si
O
OLi
C
THF
HMe2Si
HMe2Si
C
HMe2Si
(A)
H
C Li
+
Ar
H
Ar
HMe2Si
-LiH
Me2Si
O
HMe2Si
H
Me2S i= O
+
HMe2Si
C
C
H
C
C
HMe2Si
Ar
Ar
HMe2Si
(B)
Me
Cl
Cl
Cl
Br
Ar =
(
Si
O
O
)
F
n
Cl
B r
Me
Scheme 2. Treatment of some non-enolisable aldehydes with (HMe2Si)3CLi.

3624
K.D. Safa et al. / Journal of Organometallic Chemistry 693 (2008) 3622–3626
groups proceed via nucloephilic attack at carbonyl group yielding
(A) as intermediate, and then followed by an intramolecular reac-
tion between Si–H and OLi groups of (A) resulting in ring closure
and the formation of the intermediate (B) which is swiftly con-
verted to 1,1-bis(silyl)-1-alkenes. In order to examine similar reac-
tion on the polymer side chain, I and II random homopolymers
were functionalized with formyl groups. It is found that solvent
plays a crucial role in the formylation reaction. PhNO2 appears to
be a more suitable solvent than CH2Cl2. Treatment of (HMe2Si)3CLi
with carbonyl groups in the side chain of functionalized polymers
ICHO and IICHO led to the preparation of new macromolecules con-
taining Si–H groups (ISi–H and IISi–H) which have potential for con-
version into new materials with a variety of chemically reactive
pendant groups.
4. Experimental
4.1. Solvents and reagents
The reactions involving organolithium reagents were carried
out under dry argon. Solvents were dried by standard methods.
Substrates for preparation of tris(dimethylsilyl)methyllithium,
viz. HSiMe2Cl (Merck), Mg (Merck), CHBr3 (Merck), and all bezalde-
hyde derivatives (Merck) and dichloromethyl ether (Cl2CHOMe)
(Merck) and tin (IV) chloride (SnCl4) (Merck) were used as re-
ceived. For the synthesis of LDA n-BuLi (Fluka 1.6 M) was titrated
by diphenylacetic acid.
Fig. 1. The 1H NMR spectra of (a) IICHO and (b) IISi–H.
In contrast, using PhNO2 as a solvent eliminates the mentioned sig-
nals in 1H NMR which clearly demonstrates that the hydrolysis of
the intermediate (C) was completed in this solvent.
The percentage of formyl in polymer IICHO side chain was calcu-
lated by measuring the integrated peak areas of the formyl proton
and total aliphatic protons. The expression in Eq. (1) was used to
determine the composition of the polymer, where m1 is the mole
4.2. Spectra
The 1H NMR and 13C NMR were recorded with a Bruker FT-
400 MHz spectrometer at room temperature and CDCl3 as a sol-
vent. The mass spectra were obtained with a GC-Mass Agilent,
quadrupole mode 5973N instrument, operating at 70 eV. The FT-
IR spectra were recorded on a Bruker-Tensor 270 spectrometer.
Elemental analyses were carried out with an Elementar vario EL
III instrument.
fraction of formyl
styrene. Both formyl
a
-methylstyrene and 1 ꢀ m1 is that of
a-methyl-
a
-methylstyrene and -methylstyrene con-
a
tain 5 aliphatic protons. Based on the mentioned calculation,
incorporation of formyl in the side chain of polymer ICHO and IICHO
were assigned 49 and 52 mol%, respectively
IA
integrated peak area of formyl protons
¼
Ia integrated peak area of aliphatic protons
IA m1
4.3. Preparation of the formylated polymers
¼
Ia 5m1 þ 5ð1 ꢀ m1Þ
on simplification, This gives
5IA
Dissolved polymer in nitrobenzene was treated with methyl
dichloromethyl ether (Cl2CHOMe) in the presence of anhydrous
tin (IV) chloride (SnCl4) (mole ratio 1:1:2, 20–25 °C, 3 h). After
hydrolysis and washing with water, 1,4-dioxane–HCl mixture,
the organic layer was poured into cooled methanol to precipitate
the formylated polymer.
m1% ¼
ꢁ 100
ð1Þ
Ia
The new copolymers containing bis(silyl)alkenes (ISi–H and IISi–H
)
were synthesized by the treatment of carbonyl group in the side
chain of copolymers with excess amount of (HMe2Si)3CLi. All of
the obtained spectroscopic results indicate that the conversion of
carbonyl groups into bis(silyl)alkene on the side chain of polymers
were completely carried out. The 1H NMR spectra of the copolymers
show the complete disappearance of carbonyl proton resonance at
9.91 ppm and the concomitant appearance of Si–H protons at
3.99–4.07 ppm and –SiMe2 protons at 0.07–0.25 ppm (Fig. 1). In
addition, the FT-IR spectra of the obtained copolymers ISi–H and II
Si–H do not show a sharp peak at 1696 cmꢀ1 which indicates the ab-
sence of –CHO group. And also a sharp peak at 2019 cmꢀ1 related to
Si–H bond was observed.
4.4. Copolymer ICHO
FT-IR (KBr, cmꢀ1), 3033 (HC@), 2840, 2731 (CHO), 1695 (CO),
1600, 1450 (Ph); 1H NMR (400 MHz, CDCl3, ppm): d 1.41–1.86 (ali-
phatic), 6.50–8.25 (aromatic), 9.88 (CHO).
4.5. Copolymer IICHO
FT-IR (KBr, cmꢀ1), 3030 (HC@), 2844, 2732 (CHO), 1696 (CO),
1601, 1449 (Ph); 1H NMR (400 MHz, CDCl3, ppm): d 0.01–1.63 (ali-
phatic), 6.99–8.24 (aromatic), 9.91 (CHO).
4.6. Preparation of polymer bearing 1,1-bis(silyl)-1-alkenes
3. Conclusion
(HMe2Si)3CLi [20] (15.8 mmol) was added dropwise with stir-
ring to solutions of copolymers ICHO and IICHO (15.8 mmol) in THF
at room temperature. The reaction was quenched by adding a
small amount of acidic methanol after 2 h and the reaction mixture
A variety of non-enolizable aromatic aldehydes are converted to
the corresponding 1,1-bis(silyl)-1-alkenes in one-pot procedure
involving the addition of (HMe2Si)3CLi to aromatic aldehyde. It is
likely that the initial step of (HMe2Si)3CLi reaction with formyl

K.D. Safa et al. / Journal of Organometallic Chemistry 693 (2008) 3622–3626
3625
was poured into cooled acidic methanol to precipitate the poly-
4.13. Preparation of 1,1-bis(dimethylsilyl)-2-(p-chlorophenyl)ethylene
mers ISi–H and IISi–H
.
A colourless oil: Rf = 0.85 (n-hexane); yield = 60%; FT-IR (KBr,
cmꢀ1), 3060 (HC@), 2114 (Si–H), 1555, 1468 (Ph) 1250, 892 (Si–
CH3); 1H NMR (400 MHz, CDCl3, ppm): d 0.16 (d, 6H, 3JHH = 3.78 Hz,
SiMe2), 0.27 (d, 6H, 3JHH = 3.38 Hz, SiMe2), 4.20–4.29 (m, 2H, Si–H),
7.20–7.23 (d, JHH = 8.59 Hz, 2H, Ph), 7.27–7.29 (d, JHH = 8.34 Hz,
2H, Ph), 7.70 (s, 1H, HC@); 13C NMR (100 MHz, CDCl3, ppm): d
ꢀ4.0, ꢀ3.4 (SiMe2), 126.4, 127.0, 127.6, 128.5, 142.9, 153.4 (Ph,
C@C); m/z (EI): 256 (6%, [M+2]+), 254 (18%, [M]+), 239 (45%,
[MꢀMe]+), 219 (14%, [MꢀCl]+), 195 (100%, [MꢀSiMe2H]+), 143
(59%, [MꢀClꢀSiMe2H]+), 59 (36%, [SiMe2H]+). Anal. Calc. for
C12H19Si2Cl: C, 56.7; H, 7.5. Found: C, 56.4; H, 7.1%.
4.7. Copolymer ISi–H
FT-IR (KBr, cmꢀ1), 3035 (HC@), 2110 (Si–H), 1251, 895 (Si–CH3);
1H NMR (400 MHz, CDCl3, ppm): d 0.10–0.26 (dd, SiMe2), 1.55–1.95
(aliphatic), 4.01–4.10 (Si–H), 7.05–7.30 (aromatic).
3
3
4.8. Copolymer IISi–H
FT-IR (KBr, cmꢀ1), 3033 (HC@), 2109 (Si–H), 1250, 893 (Si–CH3);
1H NMR (400 MHz, CDCl3, ppm): d 0.07–0.25 (dd, SiMe2), 0.500–
2.27 (aliphatic), 3.99–4.07 (Si–H), 6.98–7.26 (aromatic).
4.14. Preparation of 1,1-bis(dimethylsilyl)-2-(2,6-dichlorophenyl)-
ethylene
4.9. General procedure for synthesis of 1,1-bis(silyl)-1-alkenes
(HMe2Si)3CLi (15.8 mmol) and aldehyde (15 mmol) in ether
(10 ml) was refluxed for 2 h, and then poured into water and ex-
tracted into ether. The organic layer was washed with water and
dried (Na2SO4). The solvent was evaporated to give a liquid which
was separated on a preparative TLC in n-hexane to give 1,1-bis(si-
lyl)-1-alkenes.
A colourless oil: Rf = 0.78 (n-hexane); yield = 56%; FT-IR (KBr,
cmꢀ1), 3056 (HC@), 2119 (Si–H), 1562, 1427 (Ph) 1251, 889 (Si–
CH3); 1H NMR (400 MHz, CDCl3, ppm): d 0.06 (d, 6H, 3JHH = 3.84 Hz,
SiMe2), 0.34 (d, 6H, 3JHH = 3.69 Hz, SiMe2), 3.89–3.92 (m, 1H, Si–H),
4.33–4.36 (m, 1H, Si–H), 7.14–7.18 (t, 1H, 3JHH = 8.01 Hz, Ph), 7.31–
3
7.33 (d, 2H, JHH = 8.01 Hz, Ph), 7.39 (s, 1H, HC@); 13C NMR
(100 MHz, CDCl3, ppm): d ꢀ4.5, ꢀ4.5 (SiMe2), 126.5, 127.4, 127.6,
137.6, 145.4, 147.6 (Ph, C@C); m/z (EI): 293 (1% [M+4]+), 291 (6%,
[M+2]+), 289 (9%, [M]+), 274 (14%, [MꢀMe]+), 142 (100%,
[MꢀPhꢀ2Cl]+), 59 (36%, [SiMe2H]+). Anal. Calc. for C12H18Si2Cl2:
C, 49.8; H, 6.2. Found: C, 50.1; H, 6.5%.
4.10. Preparation of 1,1-bis(dimethylsilyl)-2-phenylethylene
A colourless oil: Rf = 0.95 (n-hexane); yield = 74%; FT-IR (KBr,
cmꢀ1), 3062 (HC@), 2114 (Si–H), 1555, 1490 (Ph) 1251, 898 (Si–
CH3); 1H NMR (400 MHz, CDCl3, ppm): d 0.19 (d, 6H, 3JHH = 3.82 Hz,
SiMe2), 0.31 (d, 6H, 3JHH = 3.68 Hz, SiMe2), 4.30–4.34 (m, 2H, Si–H),
7.30–7.34 (m, 5H, Ph), 7.83 (s, 1H, HC@); 13C NMR (100 MHz,
CDCl3, ppm): d ꢀ4.2, ꢀ3.3 (SiMe2), 125.3, 126.5, 127.1, 139.6,
140.0, 154.9 (Ph, C@C); m/z (EI): 220 (15%, [M]+), 205(32%,
[MꢀMe]+), 161 (70%, [MꢀSiMe2H]+), 143 (100%, [MꢀPh]+), 59
(18%, [SiMe2H]+). Anal. Calc. for C12H20Si2: C, 65.4; H, 9.1. Found:
C, 65.7; H, 9.3%.
4.15. Preparation of 1,1-bis(dimethylsilyl)-2-(o-boromophenyl)-
ethylene
A colourless oil: Rf = 0.80 (n-hexane); yield = 54%; FT-IR (KBr,
cmꢀ1), 3033 (HC@), 2118 (Si–H), 1590, 1489 (Ph) 1255, 895 (Si–
CH3); 1H NMR (400 MHz, CDCl3, ppm):
d
ꢀ0.37 (d, 6H,
3JHH = 3.84 Hz, SiMe2), ꢀ0.12 (d, 6H, JHH = 3.72 Hz, SiMe2), 3.69–
3.73 (m, 1H, Si–H), 3.87–3.90 (m, 1H, Si–H), 6.67–7.10 (m, 4H,
Ph), 7.26 (s, 1H, HC@); 13C NMR (100 MHz, CDCl3, ppm): d ꢀ4.3,
ꢀ4.1 (SiMe2), 121.8, 125.6, 127.9, 128.9, 131.1, 140.1, 141.7,
154.0 (Ph, C@C); m/z (EI): 301 (5%, [M+2]+), 299 (5%, [M]+), 284
(7%, [MꢀMe]+), 219 (30%, [MꢀBr]+), 143 (100%, [MꢀC6H4Br]+), 59
(20%, [SiMe2H]+). Anal. Calc. for C12H19Si2Br: C, 48.2; H, 6.3. Found:
C, 48.5; H, 6.4%.
3
4.11. Preparation of 1,1-bis(dimethylsilyl)-2-(m-fluorophenyl)-
ethylene
A colourless oil: Rf = 0.78 (n-hexane); yield = 65%; FT-IR (KBr,
cmꢀ1), 3068 (HC@), 2116 (Si–H), 1560, 1482 (Ph) 1253, 891 (Si–
CH3); 1H NMR (400 MHz, CDCl3, ppm):
d
ꢀ0.30 (d, 6H,
3JHH = 3.84 Hz, SiMe2), ꢀ0.19 (d, 6H, JHH = 3.68 Hz, SiMe2), 3.78–
3.83 (m, 2H, Si–H), 6.48–6.60 and 6.79–6.84 (m, 4H, Ph), 7.30 (s,
1H, HC@); 13C NMR (100 MHz, CDCl3, ppm): d ꢀ4.0, ꢀ3.4 (SiMe2),
113.3, 113.9, 122.9, 142.1, 128.3, 153.3, 160.2, 162.7 (Ph, C@C);
m/z (EI): 238 (15%, [M]+), 223 (32%, [MꢀMe]+), 219 (10%,
[MꢀF]+), 179 (85%, [MꢀSiMe2H]+), 163 (100%, [MꢀFꢀSiMe2H]+),
154 (35%, [MꢀC6H4F]+), 59 (20%, [SiMe2H]+). Anal. Calc. for
C12H19Si2F: C, 60.5; H, 8.0. Found: C, 60.7; H, 8.2%.
3
4.16. Preparation of 1,1-bis(dimethylsilyl)-2-(p-boromophenyl)-
ethylene
A colourless oil: Rf = 0.80 (n-hexane); yield = 52%; FT-IR (KBr,
cmꢀ1), 3030 (HC@), 2116 (Si–H), 1590, 1489 (Ph) 1255, 895 (Si–
CH3); 1H NMR (400 MHz, CDCl3, ppm):
d
ꢀ0.26 (d, 6H,
3
3JHH = 3.84 Hz, SiMe2), ꢀ0.15 (d, 6H, JHH = 3.68 Hz, SiMe2), 3.84–
3
3.87 (m, 2H, Si–H), 6.72 (d, JHH = 8.41 Hz, 2H, Ph), 7.02 (d,
3JHH = 8.41 Hz, 2H, Ph), 7.26 (s, 1H, HC@); 13C NMR (100 MHz,
CDCl3, ppm): d ꢀ4.0, ꢀ3.4 (SiMe2), 120.6, 128.8, 129.9, 138.5,
141.5, 153.4 (Ph, C@C); m/z (EI): 301 (7%, [M+2]+), 299 (7%, [M]+),
284 (35%, [MꢀMe]+), 219 (25%, [MꢀBr]+), 143 (100%,
[MꢀC6H4Br]+), 59 (30%, [SiMe2H]+). Anal. Calc. for C12H19Si2Br C,
48.2; H, 6.3. Found: C, 47.9; H, 6.1%.
4.12. Preparation of 1,1-bis(dimethylsilyl)-2-(m-chlorophenyl)-
ethylene
A colourless oil: Rf = 0.85 (n-hexane); yield = 68%; FT-IR (KBr,
cmꢀ1), 3063 (HC@), 2115 (Si–H), 1559, 1470 (Ph) 1255, 895 (Si–
CH3); 1H NMR (400 MHz, CDCl3, ppm): d 0.16 (d, 6H, 3JHH = 3.86 Hz,
SiMe2), 0.27 (d, 6H, 3JHH = 3.68 Hz, SiMe2), 4.24–4.29 (m, 2H, Si–H),
7.14–7.27 (m, 4H, Ph), 7.70 (s, 1H, HC@); 13C NMR (100 MHz,
CDCl3): d ꢀ4.0, ꢀ3.4 (SiMe2), 125.2, 126.5, 127.2, 128.0, 132.8,
141.5, 142.4, 153.1 (Ph, C@C); m/z (EI): 256 (3%, [M+2]+), 254
(9%, [M]+), 239 (57%, [MꢀMe]+), 219 (10%, [MꢀCl]+), 195 (85%,
[MꢀSiMe2H]+), 143 (100%, [MꢀClꢀSiMe2H]+), 59 (20%, [SiMe2H]+).
Anal. Calc. for C12H19Si2Cl: C, 56.7; H, 7.5. Found: C, 56.5; H, 7.3%.
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