Synthesis of polysilanes bearing pendant carbosilyl groups and 29Si-NMR probe on the tacticity using side chain silicon atoms

Article abstract of DOI:10.1016/S0022-328X(02)01254-8

New functional polysilanes [R₂R¹Si(CH₂)₂SiH]_n (R = Me, R¹ = H (1); R = R¹ = Et(2); R = Me, R¹ = Ph (3)) bearing carbosilyl side chains have been synthesized by catalyt

Full text of DOI:10.1016/S0022-328X(02)01254-8

Journal of Organometallic Chemistry 650 (2002) 223ꢁ230
/
www.elsevier.com/locate/jorganchem
Synthesis of polysilanes bearing pendant carbosilyl groups and
29Si-NMR probe on the tacticity using side chain silicon atoms
Ravi Shankar *, Anubhav Saxena, Ajaib S. Brar
Department of Chemistry, Indian Institute of Technology, New Delhi 110016, India
Abstract
New functional polysilanes [R2R1Si(CH2)2SiH]n (Rꢀ
/
Me, R1ꢀ
/
H (1); Rꢀ
/
R1ꢀ
/
Et (2); Rꢀ
/
Me, R1ꢀ
Ph (3)) bearing carbosilyl
/
side chains have been synthesized by catalytic dehydropolymerization of precursor carbosilanes R2R1SiCH2CH2SiH3 using
1
Cp2TiCl2ꢁ
/
BuLi as a catalyst. These polymers are characterized by H, 13C, 29Si, {1Hꢁ29
/
Si} HSQC NMR spectroscopy, GPC and
TGA. Attempts to delineate the tacticity from the analysis of deconvoluted 29Si{1H}-NMR signals associated with the side chain
silicon atoms reveal that the triad concentration ratio follows a Bernoullian statistical model for polymers 1 and 2 only. # 2002
Elsevier Science B.V. All rights reserved.
Keywords: Carbosilane; Hydrosilylation; Dehydropolymerization; Microstructure; Deconvolution
1. Introduction
metallocene complexes have been examined as precata-
lysts in an attempt to improve the molecular weight and
induce stereoregularity in the polymer chain [8].
It is well recognized that the intriguing electronic
properties of polysilanes associated with delocalized s
bonded backbone are influenced by average molecular
weight [9], nature of the substituents [10] and conforma-
tion of the polymer chain [11]. Also, the microstructure
of polysilanes derived from prochiral monomer is under
In the past two decades, there have been extensive
studies on the multifaceted chemistry of linear poly-
silanes. By virtue of the s bond delocalized backbone,
these polymers exhibit many useful physical properties
which allow their potential technical applications as
photoconductors, electrical conductors, photoresists
and non-linear optical materials [1].
investigation to better understand structureꢁproperty
/
Polysilanes are also known as excellent precursors for
SiC ceramic fibers [2].
relationship, by analogy with the stereoregular organic
polymers [12]. From the analysis of deconvoluted 29Si-
NMR spectra, Jones et al. [13] have reported a logical
explanation of tacticity by identifying the isotactic,
syndiotactic and atactic triad sequences of
poly(dialkyl/arylsilane)s synthesized by Wurtz coupling.
The results are found to be in accord with Bernoullian
statistical model. By the similar approach, Corey et al.
have recently reported a detailed analysis of complex
29Si-NMR spectra of poly(phenylsilane) [8h,8j] and
poly(p-tolylsilane) [8k] produced by Group 4 metallo-
cene catalyzed dehydrocoupling. It is concluded that
these polymers adopt atactic configuration irrespective
of the nature of the catalyst used. For poly(p-tolylsi-
The most common approach for the synthesis of
poly(dialkyl/arylsilane)s involve thermal [3], ultrasonic
[4] or electrochemical [5] Wurtz coupling of dichloroor-
ganosilanes in presence of alkali metals. Though this
method results in high molecular weight polysilanes, the
severe polymerization conditions impair the use of
monomers with functionalized groups as well as control
on average molecular weight and stereoselectivity during
the chain growth [1a,1b,6]. Following the pioneering
work of Harrod et al. [7], an alternate synthetic
approach involving the transition metal mediated dehy-
drocoupling of primary organosilanes has been actively
pursued. A variety of chiral and achiral Group 4
1
lane), H-NMR spectral region of methyl groups of p-
tolyl substituents has also been examined to gauge the
polymer tacticity and the results are in accord with those
obtained from 29Si-NMR spectrum. In a separate study,
* Corresponding author.
E-mail address: shankar@netearth.iitd.ac.in (R. Shankar).
0022-328X/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 3 2 8 X ( 0 2 ) 0 1 2 5 4 - 8

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R. Shankar et al. / Journal of Organometallic Chemistry 650 (2002) 223ꢁ230
/
Harrod et al. [8g] have made a detailed analysis of 29Si-
NMR spectrum of poly(phenylsilane). In contrast to the
earlier reports [8b,8e], it was observed that the nature of
the dehydropolymerization precatalyst had little influ-
ence on the stereochemical outcome of the coupling
reactions and predominantly atactic microstructure was
concluded.
gous carbosilanes [14]. The 29Si-NMR spectrum of each
compound exhibits two distinct signals and allows the
detection of SiH3 and R2R1Siꢁ
/
groups (Section 3).
2.2. Polymerization of 1aꢁ3a
/
The neat carbosilane monomers 1aꢁ/3a are subjected
In an earlier report, Corriu et al. [2e,2f] have studied
the condensation reaction of 1,4-disilapentane, H2Me-
to dehydropolymerization using catalyst Cp2TiCl2ꢁ
/
BuLi with 1:2.2:40 catalyst to silane ratio. The contents
upon heating at 50 8C for 48 h are transformed into
immobile viscous gums. Isolation of crude polymers is
effected by dissolving the contents in hexane and
deactivating the catalyst in air until the color of the
solution changes from blue to yellow. The cyclic and low
SiCH2CH2SiH3 in presence of Cp2TiMe2 or Cp2TiCl2ꢁ
/
2-n-BuLi as catalyst. The studies reveal the initial
formation of oligosilane [H2MeSiCH2CH2SiH]n by
virtue of preferential reactivity of SiH3 group. There-
after side chain SiH2 groups of the oligomer undergo
condensation resulting in crosslinked polymer. Our
interest in functional polysilanes bearing the carbosilyl
side chains stems from a desire to expand the scope of
reaction chemistry in the side chain substituents as well
as to explore the 29Si-NMR response of carbosilyl
silicon atoms in extracting the configurational informa-
tion of these polysilanes. As a logical extension of our
earlier work [14], we have synthesized new polysilanes
molecular weight species formed during the reactions (as
1
evident from the H-NMR signals at d 4.8ꢁ
/5.1 due to
Siꢁ
tion using n-pentaneꢁ
lanes 1ꢁ3 are obtained as pale-yellow viscous gums in
48ꢁ60% isolable yield. These are soluble in common
organic solvents such as toluene, THF, hexane, chloro-
form, dichloromethane, benzene etc. GPC data of 1ꢁ
/H protons) are separated by repeated solvent extrac-
/
methanol mixture. The polysi-
/
/
/
3
[R2R1Si(CH2)2SiH]n (Rꢀ
/
Me, R1ꢀ
/
H (1); Rꢀ
/
R1ꢀ
Et
/
show a monomodel molecular weight distribution with
Mw ranging between 3100 and 5200 and polydispersity
(2); Rꢀ
/
Me, R1ꢀPh (3)) and studied the 29Si-NMR
/
spectra in the region of dangling carbosilyl functional
groups to understand the microstructure. The results are
reported herein.
1.1ꢁ2.1. In accord with the earlier trends [2e,14], the
/
formation of 1 proceeds with the selective dehydrocou-
1
pling at primary SiH site only. H-NMR spectrum of
each polymer shows broad unresolved signals in the
regions characteristic of functional groups protons.
2. Results and discussion
While a broad resonance between d 3.4ꢁ3.8 is attributed
/
to the backbone SiH protons, polymer 1 shows a
fortuitous chemical shift equivalence of the carbosilyl
SiH protons in the same region. The integrated proton
ratio of various groups is in accord with the idealized
structure as shown in Scheme 1. In the 29Si{1H}-NMR
spectra, the silicon atoms associated with the carbosilyl
groups appear in the region similar to that observed in
the corresponding precursors, although the observed
pattern is reminiscent of configurational sequence of the
polymer chain (see below). DEPT29Si-NMR spectra
2.1. Synthesis of monomer 1aꢁ3a
/
Hydrosilylation reaction between equimolar quanti-
ties of vinyltrichlorosilane and chlorodimethylsilaneꢁ
triethylsilaneꢁdimethylphenylsilane in presence of Kar-
/
/
stedt’s catalyst [15] results in the isolation of the
corresponding chlorocarbosilanes as colorless, distill-
able liquids. Subsequent treatment of these derivatives
with lithium aluminium hydride affords the desired
carbosilane monomers 1aꢁ/3a (equation 1).
CH2ꢀCHSiCl3
ꢂR2R1SiH Ca0talyst R2R1SiCH2CH2SiH3
(1)
LiAlH 4
where Rꢀ
/
Me, R1ꢀ
/
H (1a); Rꢀ
/
R1ꢀ
/
Et (2a); Rꢀ
/
Me,
R1ꢀ
/Ph (3a).
1H, 13C and 29Si-NMR spectral data are in confor-
mity with these compounds and suggest the formation
of exclusive b- isomers during hydrosilylation. For 1a,
1
the H-NMR spectrum reveals two distinct signals at d
3.87 and 3.55 in 1:3 intensity ratio and are attributed to
Siꢁ
assignments of different ꢁ
accordance with the trends reported earlier for analo-
/
H and SiH3 protons, respectively. The spectral
/
CH2ꢁ groups are made in
/
Scheme 1.

R. Shankar et al. / Journal of Organometallic Chemistry 650 (2002) 223ꢁ
/
230
225
allow the detection of backbone SiH and SiH2 end
groups at d ꢃ51.0 to ꢃ61.5 andꢃ48.5 to ꢃ53.2,
respectively. There was no evidence of the presence of
additional quaternary silicon centers that would be
associated with polymer crosslinking. Further confirma-
tion of the spectral assignments for 1 has been made on
110ꢁ
/
220 and 350ꢁ580 8C. The residual yields obtained
/
in these samples (45% for 2; 48% for 3) are much lower
than that observed for 1. Although detailed pyrolysis
studies are warranted, high residual yield in 1 may be
attributed to thermally induced Kumada-type rearran-
gement [2] and/or cross-linking at the carbosilyl func-
tional groups. Also, trace amount of titanium catalyst if
present in the polymers can be reactivated thermally [2e]
and result in high ceramic yields.
/
/
/
/
the basis of (1Hꢁ29
reveals two cross peaks at d ꢃ
51.2 to ꢃ61.5/3.5ꢁ3.8 (Fig. 1). Based on these results,
the downfield chemical shift resonance at d 3.7ꢁ3.9 is
assigned to Me2SiHꢁ and upfield values (d 3.5ꢁ3.8) to
backbone SiH protons. DEPT-135 13C-NMR spectra of
1ꢁ3 reveal distinct signals due to the different functional
carbosilyl groups and are accordingly assigned.
Thermogravimetric analysis (TGA) of 1ꢁ3 shows
different thermal stability behavior (30ꢁ800 8C, nitro-
/
Si) HSQC NMR spectrum which
/
7.3 to ꢃ10.8/3.7ꢁ3.9 and
/
/
ꢃ
/
/
/
/
/
/
2.3. Microstructure of polysilanes
/
In principle, the polysilanes 1ꢁ3 may adopt isotactic
/
(all meso), syndiotactic (all racemic) or atactic (random)
configuration [16]. An examination of 29Si-NMR spec-
tra of these polysilanes indicate a broad and complex
pattern of signals due to the backbone. This is not
surprising since the 29Si-NMR spectra of previously
known polysilanes derived from dehydrocoupling of
prochiral monomers invariably exhibit similar trends
/
/
gen atmosphere) (Fig. 2). For 1, a gradual weight loss is
observed up to 650 8C yielding 74% residual yield while
the polymers 2 and 3 show two successive thermal
decomposition steps at temperature ranging between
Fig. 1. (1Hꢁ29
Si) HSQC NMR spectrum of polysilane 1.
/

226
R. Shankar et al. / Journal of Organometallic Chemistry 650 (2002) 223ꢁ230
/
Fig. 2. Thermogravimetric analysis (TGA) of polysilanes 1ꢁ3.
/
due to the presence of adjacent stereogenic silicon
centers [8]. On the other hand, the signals associated
1.0% error. By analogy with the literature trends
[6b,8b,8h] the low field signals at d ꢃ7.3 and ꢃ9.7
are tentatively assigned to mm and mr/rm stereodo-
mains, respectively, while the signals at d ꢃ10.2 and ꢃ
10.8 are included in the rr stereodomain. On the basis of
deconvolution studies, the signal intensity of each
chemical shift region was deduced and triad intensity
ratio (mm:mr:rr) was observed as 0.04:0.28:0.68. The
validity of the parent triad assignments has been
examined in terms of Bernoullian statistical model [17].
Based on the intensity of the rr triad sequence, the
Bernoullian model reveals probability of the meso
/
/
with the dangling carbosilyl side chains in 1ꢁ3 are quite
/
distinct and well resolved. With the assumption that the
spectral pattern of the side chain is reminiscent of
configurational sequences as reported recently for
poly(p-tolylsilane) [8k], an attempt has been made to
use carbosilyl group as a NMR probe for polymer
tacticity.
/
/
29Si-NMR spectrum of 1 shows three distinct signals
at d ꢃ
/
7.3, ꢃ
/
9.7 and ꢃ
/
10.8 along with a minor signal at
ꢃ
/
10.2 associated with the carbosilylꢁ/silicon atoms. The
intensity of triad level stereodomains was evaluated by
deconvolution of spectral region (Fig. 3). The fit
between real and calculated spectra was sufficiently
close and difference spectra of two matched within
stereoreplication (Pmꢀ
/
1ꢃPr) as 0.18 and an estimate
/
of the predicted intensity ratio is observed as
0.03(mm):0.29(mr):0.68(rr). Significantly, these values
are in excellent agreement with those obtained from the
deconvoluted spectrum. The probability of racemic
replication (Pr) is observed as 0.82. Similarly for
polysilane 2, the 29Si-NMR spectrum comprising of
five peaks in the region d 7.0 to 9.4 due to dangling side
chain was analyzed by deconvolution techniques. Fig. 4
shows the 29Si-NMR spectrum (carbosilyl region), the
calculated spectrum and the difference map between the
two which converged within 1.0% error. During the
optimization of deconvoluted spectrum, the signals at d
7.0ꢁ
/
7.8 and 8.3ꢁ8.6 are assigned to rr and mr/rm triad
/
sequences, respectively, while the resonance at d 9.4 to
mm stereodomain. Table 1 summarizes the relevant data
pertaining to the triad level concentration of the parent
peaks (from the 29Si-NMR spectrum) and those calcu-
lated on the basis of Bernoullian statistical model. An
excellent agreement between these values is observed in
this case too. Using the similar deconvolution method,
the relative intensities for the triad resonances (mm:rm/
mr:rr) in polysilane 3 was observed as 0.09: 0.14: 0.77.
The data, however, fails to suitably match the Bernoul-
Fig. 3. (a) Partial 29Si-NMR spectrum of 1 depicting carbosilyl region;
*
/
spectrum, -.-.- calculated spectrum; . . .. deconvoluted peaks. (b)
Difference spectrum of the actual and calculated spectrum.

R. Shankar et al. / Journal of Organometallic Chemistry 650 (2002) 223ꢁ
/
230
227
lane) prepared from catalytic dehydropolymerization
method [8g,8h,8j,8k]. In these polymers, Bernoullian
statistical arguments reveal predominantly atactic con-
figuration with marginal bias towards syndiotactic
character. On the other hand, available data on the
tacticity of poly(alkylsilane)s formed by the catalytic
approach is quite limited. Corey et al. [18] have reported
the formation of H[BuSiH]4H in which the formation of
one stereoisomer is strongly favored suggesting a
stereoselective chain growth. It thus appears that the
microstructure of polymers 1 and 2 may find an analogy
with that of H[BuSiH]4H. Recently the results obtained
on the microstructure analysis of polysilanes have been
implicated to throw light on the mechanism of the chain
growth during the catalytic process. Among the various
factors, the stereochemical outcome is believed to arise
from the interaction of chain end substituents RPSiH2
Fig. 4. Partial 29Si-NMR spectrum of 1 depicting carbosilyl region;
spectrum, -.-.- calculated spectrum; . . ... deconvoluted peaks.
(b) Difference spectrum of the actual and calculated spectrum.
*/
(Pꢀ
/
Polymer) with the metal center during Siꢁ
/Si bond
forming transition state [8g,8j]. The results obtained
herein and also those reported earlier [18] suggest that
the substituent effect (alkyl vs. aryl) of the primary
silane precursors may also influence the tacticity of
resulting polymers.
lian statistical model presumably due to the overlapping
of signals associated with these triad domains.
If the assumptions of the chemical shift regime of
different triad sequence is correct, the data obtained
herein for 1 and 2 gives appreciably high values of
racemic enchainment probability, Pr (0.82 for 1; 0.84 for
2). The number average sequence length for respective
meso and racemic addition [17] i.e. nm and nr are found
to be 1.28, 5.86 for 1, and 1.15, 6.18 for 2, which
indicates that average chain length for racemic addition
is more than for meso addition in the polysilanes. Thus
on the basis of above data a syndiotactic rich config-
uration is expected. It is, however, imperative to
mention that the interchange in the d 29Si assignments
of rr and mm configurations will not effect the
Bernoullian statistics but will result in isotactic prefer-
ence of the configuration. Given the choice between
these extremes, syndiotactic arrangement seems more
plausible on the basis of steric arguments and is in
agreement with previous results on related configura-
tional studies [6b,8b,8h].
In conclusion, the polysilanes 1ꢁ3 bearing the carbo-
/
silyl side chain have been synthesized by titanium
catalyzed dehydrocoupling and serve as representative
models to probe the polymer tacticity using the side
chain silicon atoms as the NMR probe. The micro-
structure analysis is based on deconvolution of 29Si-
NMR signals of the carbosilyl groups and delineating
the triad concentration ratios therefrom. While the
results for 1 and 2 are in good agreement with the
Bernoullian statistical model, that of 3 does not follow
similar statistics. Determination of the microstructure of
these polymers using 29Si-NMR studies of side chain
silicon atoms finds a close analogy with a seminal report
1
on the poly(p-tolylsilane) in which the H-NMR spec-
trum of the side chain substituent (methyl group) is used
to deduce microstructure [8k]. Although a syndiotactic
rich configuration is predicted for these polysilanes, the
validity of this method needs to be strengthened by
correlating these data with those obtained from 29Si-
NMR analysis of the polymer backbone.
These results are in contrast to the previously known
microstructure of poly(phenylsilane) and poly(p-tolylsi-
Table 1
Experimentally and statistically determined triad concentration ratio for 1 and 2
Polymers
Triads
Experimentally found unit ratio
Statistical calculated unit ratio
Pm
Pr
1
rr
0.68
0.28
0.04
0.70
0.27
0.02
0.68
0.29
0.03
0.70
0.27
0.03
mr/rm
mm
rr
0.18
0.16
0.82
0.84
2
mr/rm
mm

228
R. Shankar et al. / Journal of Organometallic Chemistry 650 (2002) 223ꢁ230
/
3. Experimental
75 8C, yield 81%).1H-NMR (CDCl3):d 0.09 (d, 3JHH
3.78 Hz, SiMe2); 0.64ꢁ0.78 (m, ꢁCH2CH2ꢁ); 3.55 (t,
3JHH 3.89 (m, SiH); 13C-NMR
3.39 Hz, SiH3); 3.86ꢁ
(CDCl3): d ꢃ4.4 (SiMe2); ꢃ0.2 (ꢁCH2SiH3); 10.4
10.7 (SiH); ꢃ54.5
ꢀ
/
/
/
/
3.1. General comments
ꢀ
/
/
/
/
/
All operations were carried out using standard
Schlenk line techniques under dry nitrogen atmosphere.
Solvents were freshly distilled under inert atmosphere
over sodium benzophenone ketyl (diethylether) or
phosphorous pentoxide (n-hexane) before use. Trichlor-
ovinylsilane and chlorodimethylsilane (Aldrich) were
distilled over Mg prior to use. Triethylsilane, dimethyl-
phenylsilane, Karstedt’s catalyst, lithium aluminium
hydride, Cp2TiCl2 and n-butyl lithium (Aldrich) were
used as received. The molarity of hexane solution of n-
BuLi was confirmed by a titration method [19].
(SiHCH2); 29Si-NMR (CDCl3): d ꢃ
/
/
(SiH3); IR (cmꢃ1): 2149 (nSiH); 929 (d SiH2).
3.3. Preparation of Et3SiCH2CH2SiH3 (2a)
The reaction between triethylsilane (4.3 g; 6.0 ml; 37.5
mmol) and vinyltrichlorosilane (6.1 g, 4.8 ml; 37.7
mmol) was carried out following the procedure de-
scribed for 1a. The contents were heated for 70 8C for 5
h and distilled (b.p. 92ꢁ95 8C/5 mmHg, yield 88%). The
/
distillate (9.2 g, 33.1 mmol) was treated with LiAlH4 (2.0
g, 52.9 mmol) in diethylether. Subsequent work up gave
Infrared spectra were routinely obtained as thin films
on a Nicolet FT-IR 460 (Prote´ge´) spectrometer. 1H, 13
C
2a as a colorless liquid (b.p. 50ꢁ
/
52 8C/5 mmHg, yield
78%). H-NMR (CDCl3): d 0.51ꢁ0.76 (m, CH2SiH3ꢂ
CH2(Et)); 0.86ꢁ0.98 (m, Et3SiCH2ꢂCH3(Et)); 3.53 (t,
3JHH 3.61 Hz, SiH3); 13C-NMR (CDCl3): d 3.2
(CH2SiH3), 3.3 (CH3ꢁCH2Siꢁ), 7.6 (Et3SiCH2 ꢁ), 7.7
(CH3); 29Si-NMR (CDCl3): d 8.3 (Et3Si); ꢃ
54.1 (SiH3);
IR (cmꢃ1): 2144 (nSiH); 925 (d SiH2).
and 29Si-NMR spectra were recorded in CDCl3 on a
Bruker 300DPX spectrometer at frequency of 300, 75.5
and 59.6 MHz, respectively. 13C and 29Si-NMR spectra
in DEPT mode were obtained using standard pulse
sequence with a J modulation time 3.7 ms and 2 s delay
/
/
1
/
/
ꢀ
/
/
/
/
/
time. 1Hꢁ29
Si (HSQC) spectra was recorded using
/
standard pulse sequence with a relaxation delay of 2 s
for each of the 512t1 experiments [20]. The chemical
shifts are quoted with respect to TMS. Peak deconvolu-
tions were achieved using ORIGIN 6.0 software with a
peak-fitting package for windows. Gel permeation
chromatography of the polysilanes were carried out in
THF solutions on a Waters associated liquid chromato-
graph comprising Ultrastyragel permeation columns, a
501 HPLC solvent delivery system and R-400 refractive
index detector. TGA was carried out under nitrogen
3.4. Preparation of Me2PhSiCH2CH2SiH3 (3a)
The reaction was carried out in a manner similar to
that described for 1a using dimethylphenylsilane (7.0 g;
8.0 ml; 52.1 mmol) and vinyltrichlorosilane (8.5 g, 6.7
ml, 52.6 mmol). The contents were heated at 75 8C for 6
h and distilled (b.p. 113ꢁ115 8C/5 mmHg, yield 79.5%).
/
The chlorocarbosilane (12.4 g, 41.6 mmol) thus obtained
was treated with LiAlH4 (2.53 g, 66.6 mmol) to afford
atmosphere (30ꢁ
/
800 8C, heating rate 10 8C minꢃ1) on
the product as a colorless liquid (b.p. 77ꢁ
mmHg, yield 70.8%). 1H-NMR (CDCl3):d 0.31 (s,
SiMe2); 0.67ꢁ76 (m, CH2SiH3); 0.80ꢁ0.87(m, Me2Ph-
SiCH2); 3.55 (t, JHH 3.71Hz, SiH3); 7.38ꢁ7.56 (m,
Ph) 13C-NMR (CDCl3): d ꢃ
2.9 (SiMe2); ꢃ0.3 (ꢁ
CH2SiH3); 12.2 (SiHCH2); 128.3, 129.5, 134.1 (SiꢁPh);
53.0 (SiH3); IR
/
79 8C/5
PerkinꢁElmer, TGA-7, thermogravimetric analyzer.
/
/
/
3
3.2. Preparation of Me2HSiCH2CH2SiH3 (1a)
ꢀ
/
/
/
/
/
To a stirred solution of trichlorovinylsilane (10.6 g,
8.3 ml, 65.6 mmol) containing catalytic amount of
Karstedt’s catalyst (10ꢃ5 mole of Pt/mole of silane
used), chlorodimethylsilane (5.9 g, 7.0 ml, 63.0 mmol)
was added dropwise. Induction period was observed
/
29Si-NMR (CDCl3): d ꢃ
/
1.3 (SiH); ꢃ
/
(cmꢃ1): 2145 (nSiH); 926 (d SiH2).
3.4.1. Polymerization reaction
after a 10ꢁ
/
15 min resulting in an exothermic reaction.
In a typical procedure, the carbosilane 1a (2.0 g; 16.9
mmol) was charged with Cp2TiCl2 (0.11 g; 0.44 mmol)
and n-BuLi (0.60 ml, 1.60 M in hexane) under dry N2
conditions. The solution immediately turned blue in
color. The reaction mixture was heated at 50 8C for 48
h. Thereafter, n-hexane (40 ml) was added and dry air
was bubbled in the solution until the intense color
disappeared. The solid residue was filtered through a
short column of celite and clear filtrate was kept under
vacuum for several hours to remove the volatile
materials. The resulting gummy residue was dissolved
in minimum amount of pentane and methanol was
added dropwise until the polysilane was obtained in a
The temperature was maintained below 45 8C during
this period. After the complete addition, the reaction
mixture was heated to 40 8C for 6 h. The crude mixture
was fractionally distilled (b.p. 85ꢁ88 8C/5 mmHg, yield
/
95%). The resulting chlorocarbosilane (15.2 g, 59.3
mmol) in diethylether was added dropwise to a disper-
sion of LiAlH4 (4.7 g, 124.7 mmol) in ether at 0 8C. The
contents were gently refluxed for 5ꢁ6 h and then
/
hydrolyzed with 1 N HCl. Ether layer was extracted
and dried over anhydrous Na2SO4. Thereafter, the
solvent was removed and the contents were distilled
under vacuum to yield 1a as colorless liquid (b.p. 72ꢁ
/

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/
230
229
[3] (a) H. Stuger, R. West, Macromolecules 18 (1985) 2349;
(b) L.A. Harrah, J.M. Zeigler, Macromolecules 20 (1987) 60;
separate layer as oily viscous gum. The dissolution/
separation procedure was repeated three times to
remove the catalyst and decomposition products, yield-
ing the polysilane 1 (Yield 58%). Following the similar
procedure as above, the polymer 2 and 3 were obtained
48 and 60% yield, respectively.
(c) A.R. Wolff, J. Maxka, R. West, J. Polym. Sci. Part A Polym.
Chem. 26 (1988) 713.
[4] (a) H.K. Kim, K. Matyjaszewski, J. Am. Chem. Soc. 110 (1989)
3321;
(b) R.D. Miller, D. Thompson, R. Soorivakumaran, G.N. Fickes,
J. Polym. Sci. Polym. Chem. 20 (1991) 813;
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(1994) 2397;
For 1: 1H-NMR (CDCl3):d 0.04 (s, SiMe2); 0.54ꢁ
(m, CH2CH2); 3.4ꢁ3.8 (SiH backboneꢂSiH2 side
groups); 3.7ꢁ
3.9 (SiH pendant); 13C-NMR (CDCl3): d
4.4 (SiMe2); 2.6ꢁ5.4 (ꢁCH2); 11.2ꢁ14.3 (Me2-
SiHCH2); 29Si-NMR (CDCl3): d ꢃ
7.3 to ꢃ10.9 (Me2-
SiH); ꢃ51.3 to ꢃ61.5 (SiH backboneꢂSiH2 end
groups); IR (cmꢃ1): 2108 (nSiH); UV (DCM, nm)
265; GPC (THF): Mwꢀ5170; Mnꢀ2460.
For 2: H-NMR (CDCl3): d 0.34ꢁ1.18 (alkyl); 3.46ꢁ
3.72 (SiH backboneꢂ
SiH2 side groups); 13C-NMR
(CDCl3): d 1.4ꢁ3.4 (CH3ꢁCH2Siꢁ CH2SiH), 6.4ꢁ8.4
(Et3SiCH2ꢃ
CH3); 29Si-NMR (CDCl3): d 7.8, 8.3,
8.6, 9.4 (Et3Si); ꢃ51.6 to ꢃ60.7 (SiH backboneꢂSiH2
end groups); IR (cmꢃ1): 2117 (nSiH); UV (DCM, nm)
262; GPC (THF): Mwꢀ4670; Mnꢀ3800.
For 3: H-NMR (CDCl3):d 0.38 (SiMe2); 0.72ꢁ
CH2CH2ꢁ); 3.46ꢁ3.78 ( SiH back boneꢂSiH2 end
groups); 7.47ꢁ 3.1
7.61 (m, Ph) 13C-NMR (CDCl3): d ꢃ
(SiMe2); ꢃ0.8 to 3.7 (CH2); 10.9 to 13.6 (PhMe2-
SiHCH2); 128.7 to 134.9 (Siꢁ
Ph); 29Si-NMR (CDCl3):
d 0.5 to ꢃ1.9 (SiH pendant); ꢃ48.5 to ꢃ60.2 (SiH
backboneꢂ
SiH2 end groups); IR (cmꢃ1): 2103 (nSiH);
UV (DCM, nm) 261; GPC (THF): Mwꢀ3110; Mnꢀ
/
0.98
/
/
/
ꢃ
/
/
/
/
(c) K. Huang, L.A. Vermeulen, J. Chem. Soc. Chem. Commun.
(1998) 247.;
/
/
/
/
/
(d) S. Kashimura, M. Ishifune, N. Yamashita, H.-B. Bu, M.
Takebayashi, S. Kitajima, D. Yoshiwara, Y. Kataoka, R.
Nishida, S.-I. Kawasaki, H. Murase, T. Shono, J. Org. Chem.
64 (1999) 6615.
/
/
1
/
/
[6] (a) A.R. Wolff, I. Nozue, J. Maxka, R. West, J. Polym. Sci. Part
A Polym. Chem. 26 (1988) 701;
/
/
/
/
ꢂ
/
/
(b) J. Maxka, F. Mitter, D. Powell, R. West, Organometallics 10
(1991) 660;
/
ꢂ
/
/
/
/
(c) E. Fossum, K. Matyjaszewski, Macromolecules 28 (1995)
1618.
[7] (a) C.T. Aitken, J.F. Harrod, E. Samuel, J. Organomet. Chem.
279 (1985) C11;
/
/
1
/
1.21
(b) C.T. Aitken, J.F. Harrod, E. Samuel, J. Am. Chem. Soc. 108
(1986) 4059;
(ꢁ
/
/
/
/
/
/
(c) C.T. Aitken, J.F. Harrod, E. Samuel, Can. J. Chem. 64 (1986)
1677.
/
[8] (a) H.-G. Woo, T.D. Tilley, J. Am. Chem. Soc. 111 (1989) 8043;
(b) J.P. Banovetz, K.M. Stein, R.M. Waymouth, Organometallics
10 (1991) 3430;
/
/
/
/
/
(c) R.M. Shaltout, J.Y. Corey, Main Group Chem. 1 (1995) 115;
(d) V.K. Dioumaev, J.F. Harrod, Organometallics 15 (1996) 3859;
(e) N. Choi, S.-Y. Onozawa, T. Sakkura, M. Tanaka, Organo-
metallics 16 (1997) 2765;
/
/
2880.
(f) B.J. Grimmond, J.Y. Corey, P.N. Rath, Organometallics 18
(1999) 404;
(g) V.K. Dioumaev, K. Rahimian, F. Gauvin, J.F. Harrod,
Organometallics 18 (1999) 2249;
Acknowledgements
(h) B.J. Grimmond, J.Y. Corey, Organometallics 18 (1999) 2223;
(i) Y. Obora, M. Tanaka, J. Organomet. Chem. 595 (2000) 1;
(j) B.J. Grimmond, N.P. Rath, J.Y. Corey, Organometallics 19
(2000) 2975;
The authors are grateful to DST (India) for financial
support and C.S.I.R. (India) for S.R.F. to A. Saxena.
(k) B.J. Grimmond, J.Y. Corey, Organometallics 19 (2000) 3776;
(l) S. Bourg, R.J.P. Corriu, M. Enders, J.J.J. Moreau, Organo-
metallics 14 (1995) 564.
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230
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Pmꢂ
/
Prꢀ
/
1; mmꢀ
/
Pm2
;
rrꢀ
/
(1ꢃ
/
Pm)2; mr/rmꢀ
/
2Pm(1ꢃ
/
Pm);
nm
and nm, nr are the probability and number average sequence
ꢀ/
mmꢂ
/
0.5 mr/0.5 mr; nrꢀ
/
rrꢂ
/
0.5 mr/0.5 mr. Where Pm, Pr
[12] M.D. Bruce, G.F. Coates, E. Hauptmann, R.M. Waymouth, J.W.
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