Palladium-catalyzed insertion of 1,2- And 1,4-quinones into Si-Si bonds and its application to the modification of Si-Si-bond-containing polymers

Article abstract of DOI:10.1021/om970215q

Me₃SiSiMe₃ reacted with 1,2- and 1,4-quinones (p-benzoquinone (2a), its derivatives, 1,2-and 1,4-naphthoquinone, 9,10-phenanthraquinone (2f), 9,10-anthraquinone) in the presence of palladium catalysts to give the corresponding bis(trimethylsiloxy) aromatics in excellent to moderate yields. Active palladium catalysts were PdCl₂L₂ (L = tertiary phosphine) and Pd(dibenzylideneacetone)₂-2P(OCH₂)₃CEt, among which PdCl₂(PEt₃)₂ was in general the most efficient. A 1,2-disilacyclohexane cleanly underwent the reaction with 2f to form a 10-membered cyclic adduct. The reaction of Me₃SiSiMe₂SiMe₃ with 2a also afforded p-(Me₃SiO)₂C₆H₄, via formal extrusion of a silylene unit. Treatment of cis-(PhMe₂Si)₂Pt(P-Me₂Ph)₂ with 2a gave p-(PhMe₂SiO)₂C₆H₄, indicative of the involvement of bis(silyl)palladium species in the catalysis. Quinones 2a,f smoothly underwent the palladium-catalyzed insertion into the Si-Si bonds of (SiMePhSiMePh-p-C₆H₄)_n (9a), (SiMe₂SiMe₂CH₂CH₂)_n, and (SiMe₂SiMe₂O)_n to give partially or exhaustively modified polymers with arylenedioxy units incorporated in the backbones. A polysilane, (SiMe₂)_n, also reacted with 2a to provide a polymer with -SiMe₂-O-p-C₆H₄-O- linkages. Upon UV irradiation, a partially modified polymer obtained from 9a and 2f showed a smaller extent of decrease in molecular weight than did the original polymer. Modification with 2f improved the thermal stability of 9a in thermogravimetric analysis.

Full text of DOI:10.1021/om970215q

Organometallics 1997, 16, 5223-5233
5223
P a lla d iu m -Ca ta lyzed In ser tion of 1,2- a n d 1,4-Qu in on es
in to Si-Si Bon d s a n d Its Ap p lica tion to th e Mod ifica tion
of Si-Si-Bon d -Con ta in in g P olym er s
Hiroshi Yamashita, N. Prabhakar Reddy, and Masato Tanaka*
National Institute of Materials and Chemical Research, Tsukuba, Ibaraki 305, J apan
Received March 17, 1997X
Me3SiSiMe3 reacted with 1,2- and 1,4-quinones (p-benzoquinone (2a ), its derivatives, 1,2-
and 1,4-naphthoquinone, 9,10-phenanthraquinone (2f), 9,10-anthraquinone) in the presence
of palladium catalysts to give the corresponding bis(trimethylsiloxy) aromatics in excellent
to moderate yields. Active palladium catalysts were PdCl2L2 (L ) tertiary phosphine) and
Pd(dibenzylideneacetone)2-2P(OCH2)3CEt, among which PdCl2(PEt3)2 was in general the
most efficient. A 1,2-disilacyclohexane cleanly underwent the reaction with 2f to form a
10-membered cyclic adduct. The reaction of Me3SiSiMe2SiMe3 with 2a also afforded
p-(Me3SiO)2C6H4, via formal extrusion of a silylene unit. Treatment of cis-(PhMe2Si)2Pt(P-
Me2Ph)2 with 2a gave p-(PhMe2SiO)2C6H4, indicative of the involvement of bis(silyl)palladium
species in the catalysis. Quinones 2a ,f smoothly underwent the palladium-catalyzed insertion
into the Si-Si bonds of (SiMePhSiMePh-p-C6H4)n (9a ), (SiMe2SiMe2CH2CH2)n, and
(SiMe2SiMe2O)n to give partially or exhaustively modified polymers with arylenedioxy units
incorporated in the backbones. A polysilane, (SiMe2)n, also reacted with 2a to provide a
polymer with -SiMe2-O-p-C6H4-O- linkages. Upon UV irradiation, a partially modified
polymer obtained from 9a and 2f showed a smaller extent of decrease in molecular weight
than did the original polymer. Modification with 2f improved the thermal stability of 9a in
thermogravimetric analysis.
In tr od u ction
we have discovered that R-diketones and an R-keto ester
respectively undergo double silylation or double silyla-
tive reductive coupling with hexamethyldisilane in the
presence of palladium or platinum catalysts.9c Further
studies along this line have revealed that 1,2- and 1,4-
quinones also smoothly react with nonactivated disi-
Increasing attention has been directed toward orga-
nosilicon compounds owing to their versatile synthetic
utility and unique physicochemical properties.1 One of
the most promising methods for their preparation is
transition-metal-catalyzed addition of Si-Si bonds2 to
unsaturated compounds such as acetylenes,3 olefins,3r,u,v,4
dienes,3g,h,m,n,5 allenes,3q,6 a diyne,7 R,â-unsaturated
ketones,5c,8 quinones,5c,9a,b R-diketones,9c an R-keto ester,9c
aldehydes,3p-r,v,10 a ketone,10 isocyanides,3w,11 and im-
ines.12 However, when conventional Pd-PPh3 catalysts
are used, disilane linkages that are not activated by
electron-withdrawing substituents or ring strain are in
general reluctant to undergo the reaction.3a,c,d,f,5b,7 In
order to overcome this drawback, we have surveyed
effective catalysts for nonactivated Si-Si bonds. As a
result, we have found that the Pd-P(OCH2)3CEt system
is highly efficient in the insertion of acetylenes into the
Si-Si bonds of hexamethyldisilane, octamethyltrisilane,
and Si-Si-bond-containing polymers.3j,l,13,14 In addition,
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X Abstract published in Advance ACS Abstracts, November 1, 1997.
(1) For instance: (a) Silicon Chemistry; Corey, E. R., Corey, J . Y.,
Gaspar, P. P., Eds.; Ellis Horwood: Chichester, U.K., 1988. (b)
Inorganic and Organometallic Polymers; Zeldin, M., Wynne, K. J .,
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Chemistry; Marciniec, B., Chojnowski, J ., Eds.; Gordon and Breach:
Basel, Switzerland, 1995.
(2) For reviews on some transition-metal-catalyzed reactions of Si-
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(b) Horn, K. A. Chem. Rev. 1995, 95, 1317.
S0276-7333(97)00215-X CCC: $14.00 © 1997 American Chemical Society

5224 Organometallics, Vol. 16, No. 24, 1997
Ta ble 1. Rea ction s of Hexa m eth yld isila n e (1a ) w ith 1,2- a n d 1,4-Qu in on es (2)a
Yamashita et al.
run no.
2
Pd cat. (mol % Pdb)
time
product (yield,c %)
1
2
3
4
5
6
2a
PdCl2(PPh3)2 (1)
5 min
5 min
5 min
5 min
1 h
1 h
1 h
12 h
1 h
1 h
3a (10)
3a (12)
PdCl2(PiBu3)2 (1)
PdCl2(PEt3)2 (1)
PdCl2(PMe3)2 (1)
PdCl2(PPh3)2 (2)
PdCl2(PhCN)2 (2)
PdCl2(PhCN)2-2PPh3 (2)
Pd(dba)2-2P(OCH2)3CEt (1)
Pd(dba)2-2PPh3 (2)
Pd(dba)2-4PPh3 (2)
Pd(PPh3)4 (2)
PdCl2(PPh3)2 (2)
PdCl2(PEt3)2 (2)
PdCl2(PPh3)2 (2)
PdCl2(PEt3)2 (2)
Pd(dba)2-2P(OCH2)3CEt (2)
PdCl2(PPh3)2 (2)
PdCl2(PEt3)2 (2)
PdCl2(PEt3)2 (4)
PdCl2(PPh3)2 (2)
PdCl2(PEt3)2 (2)
PdCl2(PMe3)2 (2)
Pd(dba)2-2P(OCH2)3CEt (2)
PdCl2(PPh3)2 (2)
PdCl2(PEt)2 (2)
Pd(dba)2-2P(OCH2)3CEt (2)
3a (∼100)
3a (17)
3a (∼100 [95])
3a (0.5), 4a (0.5)
3a (96), 4a (2)
7
8d
9
3a (70), 4a (9), 5a (3), P1 (∼4),e P2 (∼1)e
3a (47), 4a (14), 5a (tracef), P1 (∼0.5),e P2 (∼1)e
10
11
12
13
14
15
16
17
18
19i
20
21
22
23
24
25
26
3a (23), 4a (9), 5a (tracef), P1 (tracef),e P2 (∼0.5)e
1 h
3a (21), 4a (8), 5a (tracef), P1 (tracef),e P2 (∼0.5)e
2b
2c
24 h
24 h
1 h
1 h
1 h
5 d
5 d
5 d
1 h
1 h
1 h
1 h
1 h
1 h
1 h
3b (70 [∼65]g), P3 (∼8),e P4 (∼2)e
3b (83), P3 (∼1),e P4 (∼2)e
3c (78 [80]h)
3c (87)
3c (1)
3d (2)
3d (5)
3d (24)
3e (27), 4e (22)
3e (65), 4e (22)
3e (56), 4e (23)
3e (11), 4e (5)
3f (78)
3f (99)
3f (∼100 [95])
2d
2e
2f
Conditions: 1a (0.44 mmol), 2 (0.40 mmol), benzene (0.05 mL), 120 °C. Based on 2. c Estimated by GC based on 2. Figures in
a
b
brackets are isolated yields. 1a (3.52 mmol), 2a (3.20 mmol), benzene (0.40 mL). e Figures in parentheses are approximate yields using
d
the same GC (TCD) factors as those for 3. f e0.2%. ∼90% purity. 6 h. 140 °C.
g
h
i
lanes in the presence of some palladium catalysts to give
the corresponding 1,2- and 1,4-bis(siloxy) aromatic
compounds.15,16 Herein are described full details of the
novel catalysis, the reactivity of bis(silyl)platinum spe-
cies in relation to the mechanism, and an application
to the modification of organosilicon polymers.17
Resu lts a n d Discu ssion
Ca ta lysts. Heating a mixture of hexamethyldisilane
(1a ; 1.1 equiv), p-benzoquinone (2a ), a palladium cata-
lyst, and benzene at 120 °C gave a 1,6-double-silylation
product, p-bis(trimethylsiloxy)benzene (3a ) (eq 1; Table
1, runs 1-11). The activity of PdCl2L2 complexes
(5) (a) Okinoshima, H.; Yamamoto, K.; Kumada, M. J . Am. Chem.
Soc. 1972, 94, 9263. (b) Sakurai, H.; Kamiyama, Y.; Nakadaira, Y.
Chem. Lett. 1975, 887. (c) Tamao, K.; Okazaki, S.; Kumada, M. J .
Organomet. Chem. 1978, 146, 87. (d) Matsumoto, H.; Shono, K.; Wada,
A.; Matsubara, I.; Watanabe, H.; Nagai, Y. J . Organomet. Chem. 1980,
199, 185. (e) Sakurai, H.; Eriyama, Y.; Kamiyama, Y.; Nakadaira, Y.
J . Organomet. Chem. 1984, 264, 229. (f) Ishikawa, M.; Nishimura, Y.;
Sakamoto, H.; Ono, T.; Oshita, J . Organometallics 1992, 11, 483. (g)
Obora, Y.; Tsuji, Y.; Kawamura, T. Organometallics 1993, 12, 2853.
(6) (a) Watanabe, H.; Saito, M.; Sutou, N.; Nagai, Y. J . Chem. Soc.,
Chem. Commun. 1981, 617. (b) Watanabe, H.; Saito, M.; Sutou, N.;
Kishimoto, K.; Inoue, J .; Nagai, Y. J . Organomet. Chem. 1982, 225,
343.
(7) Kusumoto, T.; Hiyama, T. Tetrahedron Lett. 1987, 28, 1807.
(8) (a) Hayashi, T.; Matsumoto, Y.; Ito, Y. Tetrahedron Lett. 1988,
29, 4147. (b) Hayashi, T.; Matsumoto, Y.; Ito, Y. J . Am. Chem. Soc.
1988, 110, 5579. (c) Matsumoto, Y.; Hayashi, T.; Ito, Y. Tetrahedron
1994, 50, 335.
(9) (a) Reddy, N. P.; Yamashita, H.; Tanaka, M. J . Am. Chem. Soc.
1992, 114, 6596. (b) Yamashita, H.; Reddy, N. P.; Tanaka, M.
Macromolecules 1993, 26, 2143. (c) Yamashita, H.; Reddy, N. P.;
Tanaka, M. Chem. Lett. 1993, 315.
(10) Uchimaru, Y.; Williams, N. A.; Tanaka, M. Presented at the
67th Annual Meeting of the Chemical Society of J apan, Tokyo, J apan,
March 29-April 1, 1994; Abstract 1H107.
(11) (a) Ito, Y.; Nishimura, S.; Ishikawa, M. Tetrahedron Lett. 1987,
28, 1293. (b) Ito, Y.; Matsuura, T.; Murakami, M. J . Am. Chem. Soc.
1988, 110, 3692. (c) Ito, Y.; Suginome, M.; Murakami, M.; Shiro, M. J .
Chem. Soc., Chem. Commun. 1989, 1494. (d) Ito, Y.; Suginome, M.;
Matsuura, T.; Murakami, M. J . Am. Chem. Soc. 1991, 113, 8899.
(12) Williams, N. A.; Uchimaru, Y.; Tanaka, M. Presented at the
69th Annual Meeting of the Chemical Society of J apan, Tokyo, J apan,
March 27-30, 1995; Abstract 2C746.
(13) For insertion of acetylenes into nonactivated Si-Si bonds, Ito
et al. also reported an effective palladium catalyst system that
contained a large amount of a tertiary alkyl isocyanide.3k,s,t,w
(14) For double silylation with nonactivated Si-Si bonds using
iodine or fluoride anion as catalyst, see: (a) Matsumoto, H.; Koike, S.;
Matsubara, I.; Nakano, T.; Nagai, Y. Chem. Lett. 1982, 533. (b) Hiyama,
T.; Obayashi, M.; Mori, I.; Nozaki, H. J . Org. Chem. 1983, 48, 912. (c)
Hiyama, T.; Obayashi, M. Tetrahedron Lett. 1983, 24, 4109.
(15) Insertion of p-benzoquinone into an activated disilane (1,2-
difluoro-1,1,2,2-tetramethyldisilane) with the Pd-PPh3 catalyst was
previously reported.5c For iodine-catalyzed reactions of 1,4-quinones,
see Ref 14a.
increased in the order L ) PPh3 < PiBu3 < PMe3 < PEt3,
(16) The reaction is useful for protection of quinones. For instance,
see: (a) Thompson, R. H. Naturally Occurring Quinones; Academic
Press: New York, 1971. (b) Stewart, R. F.; Miller, L. L. J . Am. Chem.
Soc. 1980, 102, 4999. (c) Willis, J . P.; Cogins, K. A. Z.; Miller, L. L. J .
Org. Chem. 1981, 46, 3215.
(17) Preliminary results on polymer modification have already been
published.9b

Pd-Catalyzed Insertion of Quinones into Si-Si Bonds
Organometallics, Vol. 16, No. 24, 1997 5225
Ch a r t 1
F igu r e 1. Time course of the yield of 3a in the reaction of
1a with 2a catalyzed by PdCl2(PPh3)2 (1a , 0.44 mmol; 2a ,
0.40 mmol; PdCl2(PPh3)2, 0.004 mmol; benzene, 0.05 mL;
120 °C).
series of 1,4-quinones, the reactivity decreases in the
order 2a > 2c . 2d , presumably reflecting the steric
hindrance of the quinones. As compared with 2a , 2b
displays low reactivity, which can be considered in terms
of steric and electronic factors. However, since 2,3,5,6-
tetrafluoro-p-benzoquinone was more reactive than 2a ,19
steric hindrance of the chlorine substituents appears to
be the major factor for the low reactivity of 2b. When
1,2-quinones were used in place of 1,4-quinones, 1,4-
double silylation proceeded under similar conditions.
Thus, 1,2-naphthoquinone (2e) and 9,10-phenanthra-
quinone (2f) reacted with 1a to provide the correspond-
ing 1,2-bis(siloxy) aromatics 3e and 3f, respectively
(runs 20-26).20 Noteworthy is the result that 3f was
obtained nearly quantitatively (run 26), since it was
reported that 2f did not form 3f by the conventional
double silylation using Me3SiCl/K.21
For almost all quinones, PdCl2(PEt3)2 exhibited the
highest activity among the catalysts examined, although
the Pd(dba)2-2P(OCH2)3CEt system was also efficient
in the reaction of 2f. Usually the desired double
silylation proceeded cleanly by using suitable palladium
catalysts, and nearly pure products 3 were isolated by
short-path distillation in excellent to good yields (runs
5, 14, and 26). However, in the reaction of 2b, GC and
GC-MS indicated formation of a dechlorinated byprod-
uct (P3, ∼2-8% yield) that appeared to be 1,2,4-
trichloro-3,6-bis(trimethylsiloxy)-5-(trimethylsilyl)ben-
zene. The compound may be formed via substitution
of the chlorine atom of 3b by the trimethylsilyl group
of 1a .22,23 On the other hand, the o-quinone 2e gave a
considerable amount of naphthol derivatives, 2-(trimeth-
ylsiloxy)-1-naphthol and 1-(trimethylsiloxy)-2-naphthol
(4e; Chart 1, 5-23% yields). These are genuine prod-
ucts of the reaction and not secondary products coming
from workup procedures.
revealing PdCl2(PEt3)2 to be most efficient (runs 1-4).
With the PdCl2(PEt3)2 catalyst (1 mol %) 3a was
obtained nearly quantitatively by heating only for 5 min.
Palladium metal was essential in the reaction, and an
attempt to run the reaction in the presence of PEt3 (2
mol %) alone in place of PdCl2(PEt3)2 did not result in
the formation of 3a . Although the activity of PdCl2-
(PPh3)2 was lower, 3a was formed in ∼100% yield by
increasing the catalyst concentration (2 mol %) and
prolonging the reaction time (1 h) (run 5). Phosphine
ligands appear to be prerequisites for occurrence of the
reaction; a palladium catalyst without phosphines,
PdCl2(PhCN)2, was almost inactive, while the activity
of the PdCl2(PhCN)2-2PPh3 system was similar to that
of PdCl2(PPh3)2 (runs 6, 7). However, excess phosphine
(P/Pd ) 4) significantly slowed the reaction in Pd-PPh3
systems such as Pd(dba)2-4PPh3 (dba ) dibenzylidene-
acetone) and Pd(PPh3)4 (runs 10, 11). On the other
hand, the Pd(dba)2-2P(OCH2)3CEt system, which was
the catalyst of choice for insertion of acetylenes into Si-
Si bonds,3j,l was less active and less selective in the
present reaction (run 8); the formation of 3a (70% yield,
12 h reaction time) was accompanied by the undesired
formation of 4-(trimethylsiloxy)phenol (4a ; Chart 1, 9%)
and 1,4-bis(trimethylsiloxy)-2-(trimethylsilyl)benzene
(5a ; Chart 1, 3%).18
Besides the nature and the quantity of phosphorus
ligands, the presence of chlorine in the reaction system
affects the activity and selectivity. Thus, a chlorine-
free Pd-PPh3 system, Pd(dba)2-2PPh3, was much less
active than PdCl2(PPh3)2 and afforded a considerable
amount of 4a (run 9). Monitoring the progress of the
reaction with the PdCl2(PPh3)2 catalyst showed the
presence of an induction period (2-3 min) (Figure 1),
indicative of the conversion of PdCl2(PPh3)2 into active
species in the initial stage of the reaction. At the
moment, however, the real structure of the catalytically
active species and the mechanism detailing the favor-
able role of the chlorine atom are ambiguous.
Si-Si-Bon d ed Com p ou n d s. A phenylated disilane,
1,1,2,2-tetramethyl-1,2-diphenyldisilane (1b), also re-
(19) (a) 2,3,5,6-Tetrafluoro-p-benzoquinone (TFBQ), which is steri-
cally similar to 2a but electronically more deficient than 2a , showed
higher reactivity than 2a , although the products were not fully
characterized;19b in the reaction with 1a (1a 0.44 mmol, quinone 0.40
mmol, PdCl2(PPh3)2 0.004 mmol, benzene 0.05 mL, 120 °C, 10 min),
the conversion of 1a was 80% for TFBQ, while it was 34% for 2a . The
results indicate that electron-withdrawing substituents are likely to
promote the reaction. (b) GC and GC-MS measurements indicated
formation of p-(Me3SiO)2C6F4 (∼40% yield), Me3SiF (∼20%), and an
adduct (∼20%) that showed a GC-MS parent peak at m/z 560 which
corresponded to 1a + TFBQ × 2 + Me3Si - F.
Qu in on es. Besides 2a , other 1,4-quinones such as
chloranil (2b), 1,4-naphthoquinone (2c), and 9,10-an-
thraquinone (2d ) also reacted with 1a in the presence
of palladium catalysts to give the corresponding 1,4-
bis(siloxy) aromatic compounds (3b-d ) in good to
moderate yields (eq 1; Table 1, runs 12-19). In the
(18) Small amounts of other products (P1 and P2, total yields ∼5%)
were also formed, although their structures have not been determined
yet. GC-MS indicated m/z values for the parent ions of 254 (an isomer
of 3a ) for P1 and 434 (1a + 2a × 2 + Me3Si - H) for P2 (see
Experimental Section).
(20) The high reactivity of 2f as compared with sterically less
hindered 2e suggests that the steric effect is not as crucial in the case
of o-quinone.
(21) Murakawa, T.; Fujii, K.; Murai, S.; Tsutsumi, S. Bull. Chem.
Soc. J pn. 1972, 45, 2520.

5226 Organometallics, Vol. 16, No. 24, 1997
Yamashita et al.
acted with 2a in the presence of the PdCl2(PEt3)2
catalyst to give the p-bis(siloxy)benzene 3g (89% yield)
along with a small amount of the phenol derivative 4g
(7%) (eq 2). When a cyclic disilane, 1,1,2,2-tetramethyl-
e0.05:∼1). The formation of 6i and P5 may suggest the
involvement of (silylene)palladium species in the ca-
talysis.24
The reaction of octamethyltrisilane (1e) with 2a
unexpectedly gave 3a (30%) and 4a (20%) as the major
volatile products (eq 6), via formal extrusion of a silylene
unit from 1e, along with a small quantity (e10%) of a
compound that was suggested by GC-MS to be a 1:2
adduct, dimethylbis[4-(trimethylsiloxy)phenoxy]silane
(6j, Chart 1). In the reaction of 1e with phenylacety-
1,2-disilacyclohexane (1c), was allowed to react with the
o-quinone 2f, the 10-membered cyclic product 3h was
obtained nearly quantitatively (eq 3). In contrast, we
lene, formation of such degraded products was not
observed, and a mixture of the regioisomeric 1:2 adducts
was obtained cleanly.3j,k
Mech a n ism . Quinone 2a is known to interact with
Pd(PPh3)4 to give (p-benzoquinone)Pd(PPh3)2 (7).25 Ugo
et al. proposed that such a species was involved in the
palladium-catalyzed addition of terminal olefins to 2a .26
Kumada et al. also assumed the possible participation
of a similar intermediate in the addition of 1d to 2a .5c
However, treatment of 7 with disilane 1a (2 equiv) in
the absence or presence of 2c scarcely afforded 3a (e5%
yield, g90% recovery of 7) even after heating at 120 °C
for 9-23 h (eq 7). On the other hand, the reaction of
have found that treatment of 1c with the p-quinone 2a
under similar reaction conditions resulted in ring-
opening copolymerization to give a polymer consisting
of alternating 1,6-disilahexylene and p-phenylenedioxy
units (eq 4).9a Different from 1a ,b, the activated disilane
27
cis-(PhMe2Si)2Pt(PMe2Ph)2 (8a ) with 2a (2 equiv)
1,2-difluoro-1,1,2,2-tetramethyldisilane (1d ) did not un-
dergo smooth addition to 2a under the present condi-
tions using the PdCl2(PEt3)2 catalyst; the reaction
formed the expected bis(siloxy)benzene 3i in a much
lower yield (∼25%, eq 5), and gave byproducts (4i, 6i,
smoothly proceeded at 80 °C to form 3g (60% yield) and
4g (35%) (eq 8).28 Accordingly, the present catalysis
seems to involve bis(silyl)palladium species, which are
(24) (Silylene)palladium species may be involved in the catalyses
of a 1,2-dichlorodisilane and a 1,3-dichlorotrisilane under certain
conditions as well. Thus, Cl(SiMe2)2Cl24a or Cl(SiMe2)3Cl24b respectively
reacts with a diketone (benzil) or acetylenes (2 equiv) in the presence
and P5, Chart 1) that appeared to be 4-(fluorodimeth-
ylsiloxy)phenol (4i), bis[4-(fluorodimethylsiloxy)phen-
oxy]dimethylsilane (6i), and difluorodimethylsilane (P5),
respectively (GC (TCD) area ratio 3i:4i:6i:P5 ) 1:e0.05:
of a palladium catalyst to form
a 4,5-diphenyl-1,3-dioxa-2-sila-4-
cyclopentene or 1,4-disilacyclohexadienes, along with the coproduct
Me2SiCl2. See: (a) Rich, J . D. Organometallics 1989, 8, 2609. (b)
Tanaka, Y.; Yamashita, H.; Tanaka, M. Organometallics 1995, 14, 530.
(25) Takahashi, S.; Hagihara, N. Nippon Kagaku Zasshi 1967, 88,
1306.
(26) Roffia, P.; Conti, F.; Gregorio, G.; Pregaglia, G. F.; Ugo, R. J .
Organomet. Chem. 1973, 54, 357.
(22) For examples of palladium-catalyzed exchange reactions be-
tween C-X (X ) Cl, Br, I) and Si-Si bonds giving C-Si and Si-X
bonds, see: (a) Matsumoto, H.; Ohkawa, K.; Matsubara, I.; Kasahara,
M.; Arai, T.; Nagai, Y. J . Organomet. Chem. 1984, 264, 29 and
references cited therein. (b) Eaborn, C.; Griffiths, R. W.; Pidcock, A.
J . Organomet. Chem. 1982, 225, 331 and references cited therein. (c)
Yamamoto, K.; Hayashi, A.; Suzuki, S.; Tsuji, J . Organometallics 1987,
6, 974 and references cited therein. (d) Krafft, T. E.; Rich, J . D.;
McDermott, P. J . J . Org. Chem. 1990, 55, 5430 and references cited
therein.
(27) Kobayashi, T.; Hayashi, T.; Yamashita, H.; Tanaka, M. Chem.
Lett. 1988, 1411.
(28) Different from 8a ,
a bis(fluorosilyl)platinum species, cis-
(FMe2Si)2Pt(PEt3)2 (8b), that was prepared by oxidative addition of
29
1d to Pt(PEt3)3 did not undergo smooth reaction with 2a (see
Experimental Section), which may be a reason for the nonselective
catalytic reaction of 1d with 2a .
(29) Yamashita, H.; Kobayashi, T.; Hayashi, T.; Tanaka, M. Chem.
Lett. 1990, 1447.
(23) GC showed formation of another byproduct (P4, ∼2%) whose
GC-MS indicated the parent ion at m/z 356 ()Me3Si × 2 + 35Cl × 3 +
C6O2H).

Pd-Catalyzed Insertion of Quinones into Si-Si Bonds
Organometallics, Vol. 16, No. 24, 1997 5227
Ta ble 2. Rea ction s of Silicon P olym er s (9) w ith Qu in on es (2)a
run no.
9b
2 (amt, equiv)
Pd cat.c
time
product (yield,d %)
p:qe
Mw (Mw/Mn) f of 10
1
9a
9a
9b
9c
9b
9c
9c
2f (1.05)
2f (0.30)
2f (1.05)
2f (0.30)
2a (1.05)
2a (0.30)
2a (0.30)
A
A
A
A
B
B
C
3 h
3 h
1 h
40 min
3 h
10a (90)
10b (86)
10c (84)
10d (∼100)
10e (83j)
10f (66)
∼100:∼0
5.8 × 104 (3.0)
5.2 × 104 (2.9)
5.0 × 104 (2.5)
1.8 × 105 (2.4)
1.9 × 104 (2.4)k
1.1 × 105 (2.2)
2.5 × 105 (3.5)
2g
3
29:71
∼100:∼0
20:80
4h
5i
6h
7h
∼100:∼0
15 min
40 min
21:79
10f (69)
21:79
a
Conditions: 9 (0.20 mmol monomer unit), 2 (0.30 or 1.05 equiv/monomer unit of 9), Pd catalyst (ca. 2 mol % Pd/2), benzene (0.10 mL),
120 °C. 9a , Mw ) 4.6 × 104 (Mw/Mn ) 2.6); 9b, Mw ) 2.5 × 105 (Mw/Mn ) 2.3); 9c, Mw ) 1.9 × 105 (Mw/Mn ) 2.3). c Legend: A, Pd(dba)2-
b
2P(OCH2)3CEt; B, PdCl2(PEt3)2; C, PdCl2(PPh3)2. Yield after purification. e Estimated by 1H NMR and/or elemental analysis. Measured
d
f
g
h
i
by GPC using polystyrene standards. Pd catalyst (4 mol % Pd/2f). 9c (0.50 mmol monomer unit). 9b (0.40 mmol monomer unit),
benzene (0.20 mL). A combined yield of two fractions with higher and lower molecular weights (see Experimental Section). Before
purification.
j
k
Sch em e 1
formed by oxidative addition of Si-Si bonds to pal-
ladium species,30 in the pathways leading to the forma-
tion of bis(siloxy) aromatics (Scheme 1). Analogous
bis(silyl)metal species were previously proposed as
intermediates for the double silylation of acetylenes,
dienes, and olefins.3o,u,29,31
On the other hand, the phenol derivative 4a was
formed as a byproduct in the reaction of 1a with 2a
under certain conditions. To get more information on
the origin of the hydrogen atom of the hydroxy group,
benzene-d6 or (D3C)3SiSi(CD3)3 was used in place of
benzene or 1a , respectively (Pd(dba)2-2P(OCH2)3CEt
catalyst). In each case, a mixture of compounds of types
3a and 4a was obtained as the major volatile product.32
equiv/monomer unit) in the presence of the Pd(dba)2-
However, GC-MS and/or NMR measurements did not
2P(OCH2)3CEt (ca. 2 mol % Pd/2f) catalyst at 120 °C
show deuterium incorporation into the hydroxy group
for 3 h, insertion of 2f into almost every Si-Si bond of
of the type 4a compound. The results indicate that the
9a cleanly took place to give the modified polymer 10a
hydroxy hydrogen does not come from the solvent or
(p:q ) ∼100:∼0, Mw ) 5.8 × 104, Mw/Mn ) 3.0) with
from the disilane. Further studies are required to
9,10-phenanthrylenedioxy units incorporated in the
elucidate the mechanism of the formation of 4a and
backbone (run 1). Analytically pure 10a was readily
other hydroxy-group-containing byproducts.
obtained by precipitation from benzene-2-propyl alco-
Mod ifica tion of Silicon P olym er s. The present
hol. Since the reaction proceeds nearly quantitatively,
catalysis was applicable to modification of Si-Si-bond-
the degree of the modification is easily controlled by
containing polymers by insertion of 2f and 2a , which
varying the quantity of 2f charged; the use of 0.30 equiv
could undergo double silylation with 1a nearly quanti-
of 2f per monomer unit of 9a gave the modified polymer
tatively (eqs 9 and 10; Table 2).
10b with 29% of the Si-Si bonds being converted (run
When a disilanylene-unit-containing polymer, poly[(1,2-
2). The molecular weight of 10b (Mw ) 5.2 × 104, Mw/
dimethyl-1,2-diphenyldisilanylene)(p-phenylene)]33 (9a ;
Mn ) 2.9) was in reasonable agreement with the
Mw ) 4.6 × 104, Mw/Mn ) 2.6), was treated with 2f (1.05
predicted value (Mw ) 5.5 × 104, Mw/Mn ) 2.7) for 29%
modification,34 indicative of no extensive degradation
(30) Although there has been no direct evidence, possible charge
having taken place during the reaction. Likewise, poly-
[(tetramethyldisilanylene)ethylene]4a (9b; Mw ) 2.5 ×
105, Mw/Mn ) 2.3) could be exhaustively reconstructed
transfer from disilanes to quinones may assist oxidative addition of
the disilanes to the palladium center by decreasing the electron density
at the silicon atoms. For intramolecular charge transfer from a Si-Si
bond to a quinone moiety, see: Sakamoto, K.; Sakurai, H. J . Am. Chem.
Soc. 1991, 113, 1466.
(31) (a) Kobayashi, T.; Hayashi, T.; Yamashita, H.; Tanaka, M.
Chem. Lett. 1989, 467. (b) Murakami, M.; Yoshida, T.; Ito, Y. Orga-
nometallics 1994, 13, 2900.
(32) Compounds 3a (64% yield) and 4a (7%) were formed in the
reaction run in benzene-d6 (120 °C, 12 h), while the reaction of
(D3C)3SiSi(CD3)3 gave (D3C)3SiO-p-C6H4-OSi(CD3)3 (∼50%) and (D3-
C)3SiO-p-C6H4-OH (∼3%), as analyzed by GC-MS and 1H NMR.
(33) (a) Nate, K.; Ishikawa, M.; Ni, H.; Watanabe, H.; Saheki, Y.
Organometallics 1987, 6, 1673. (b) Nate, K.; Inoue, T.; Sugiyama, H.;
Ishikawa, M. J . Appl. Polym. Sci. 1987, 34, 2445.
by insertion of 2f to give the new polymer 10c (Mw
)
5.0 × 104, Mw/Mn ) 2.5), albeit with a decrease in the
molecular weight (run 3). A siloxane polymer, poly(tet-
ramethyldisiloxane)35 (9c; Mw ) 1.9 × 105, Mw/Mn
)
2.3), also reacted with 2f (0.30 equiv) to give the
(34) Predicted Mw of 10b ) (Mw of 9a ) × (average formula weight
per monomer unit with 29% modification of 10b)/(formula weight per
monomer unit of 9a ) ) (4.6 × 104) × (376.9/316.6) ) 5.5 × 104.

5228 Organometallics, Vol. 16, No. 24, 1997
Yamashita et al.
F igu r e 2. 13C NMR spectrum of 10a (in CDCl3).
partially modified polymer 10d (Mw ) 1.8 × 105, Mw/
Mn ) 2.4), with the degree of modification being 20% at
40 min reaction time (run 4).
Introduction of p-phenylenedioxy units was possible
as well by using 2a . Thus, the reaction of 9b with 2a
(1.05 equiv) smoothly proceeded in the presence of the
PdCl2(PEt3)2 catalyst to give the exhaustively modified
polymer 10e (Mw ) 1.9 × 104, Mw/Mn ) 2.4) (run 5).
Polymer 9c also underwent reaction with 2a (0.30 equiv)
polymer 12 (Mw ) 1.5 × 104), consisting of alternating
dimethylsilylene and p-phenylenedioxy units, in 85%
yield. Reprecipitation with benzene-2-propyl alcohol
provided a fraction with a higher molecular weight of
Mw ) 2.3 × 104 (Mw/Mn ) 3.8) in 46% yield. Polymer
12, however, may be formed via interaction of dimeth-
ylsilylene with 2a rather than via direct insertion of 2a
into the Si-Si bonds of 11, judging from the result that
the reaction of 1e under similar reaction conditions
involved formal extrusion of a dimethylsilylene unit (eq
6). In addition, we have observed that a cyclic oligosi-
lane, dodecamethylcyclohexasilane, also underwent a
palladium-catalyzed reaction with 2a , possibly via si-
lylene intermediates, to give the same polymer 12.9a
Polymers 10a -c,e possessed much higher chemical
stability against hydrolysis than the monomeric com-
pounds 3a ,f and could be purified by precipitation using
2-propanol without significant degradation. In contrast,
siloxane polymers 10d ,f were not as stable, and at-
tempted precipitation using 2-propanol or methanol
resulted in a decrease in the molecular weight; the
values of Mw before and after reprecipitation were
respectively 1.7 × 105 and 1.2 × 105 for 10d (precipita-
tion with benzene-2-propyl alcohol) and 1.2 × 105 and
5.0 × 104 for 10f (benzene-methanol). However, Flo-
risil columns were found to be effective for purification
of the polymers without extensive degradation; in
separate experiments, the values of Mw before and after
column chromatography (benzene eluent) were both 1.8
× 105 for 10d and respectively 1.3 × 105 and 1.1 × 105
for 10f.
to give the partially reconstructed polymer 10f (Mw
)
1.1 × 105, Mw/Mn ) 2.2) with 21% of the Si-Si bonds
being transformed at 15 min reaction time (run 6).
Modified polymers 10e,f obtained with the PdCl2(PEt3)2
catalyst showed lower molecular weights (GPC) than
the original polymers, indicative of unfavorable degra-
dation also having taken place. However, in the reac-
tion of 9c, a less active catalyst, PdCl2(PPh3)2, was found
to be able to reconstruct without the degradation; 10f
obtained with the PdCl2(PPh3)2 catalyst exhibited an
increased molecular weight (Mw ) 2.5 × 105) (run 7).
A polysilane also reacted with a quinone to provide
an arylenedioxy-unit-containing polymer (eq 11). Thus,
upon heating of a mixture of poly(dimethylsilylene)36
(11), 2a (1.1 equiv/monomer unit), PdCl2(PEt3)2 (ca. 1
mol %/2a ), and benzene in a sealed tube at 120 °C, the
originally insoluble 11 gradually dissolved to give a
brown solution. After 18 h a small amount of an
insoluble solid was removed by filtration. Concentration
of the filtrate followed by washing with hexane gave the
Modified polymers 10 show satisfactory 1H, 13C, and/
or 29Si NMR, IR, and analytical data for the proposed
structures. For instance, the 13C NMR spectrum of 10a
cleanly displays 2 signals ascribable to the SiMe carbons
at -2.3 and -2.2 ppm37 and 13 signals for the ring
carbons in the region 120-140 ppm (Figure 2). On the
other hand, the partially modified polymer 10d shows
new SiMe2 carbon signals A, B, and C at -0.2, 0.4, and
(35) Chojnowski, J .; Kurjata, J .; Rubinsztajn, S. Makromol. Chem.,
Rapid Commun. 1988, 9, 469.
(36) The molecular weight of 11 was measured by high-temperature
GPC (ca. 210 °C) to be 4.7 × 103 for Mw (Mw/Mn ) 1.8). See: Ohnaka,
T. In Synthesis and Applications of Organosilicon Polymers; Sakurai,
H. Ed.; CMC: Tokyo, 1989; p 99.
(37) The appearance of the two signals seems to originate from
diastereoisomerism with respect to the placement of the substituents
at the neighboring two silicon atoms.

Pd-Catalyzed Insertion of Quinones into Si-Si Bonds
Organometallics, Vol. 16, No. 24, 1997 5229
F igu r e 3. 13C NMR signals of the SiMe2 moieties of (a)
10d and (b) 10f. The signals marked with x are coupling
satellites with 29Si (1J SiC ≈ 48 Hz). For assignment of the
signals A-D and A′-D′, see Figure 4.
F igu r e 5. UV spectra of 10a ,b and 9a (1 × 10-4 M THF
solution).
F igu r e 4. Possible classification of the SiMe2 moieties in
10d (10f) for the corresponding 13C NMR signals (Figure
3).
1.4 ppm, respectively, along with an SiMe2 signal D at
the same chemical shift (2.0 ppm) as for the parent
polymer 9c, with the integral ratio A:B:C:D being 1:1.5:
1.4:9.5 (Figure 3a). Likewise, 13C NMR of 10f (run 7)
displays new SiMe2 signals A′, B′, and C′ at -0.7, -0.3,
and 1.5 ppm, respectively, along with an intact signal
D′ at 2.0 ppm with the ratio A′:B′:C′:D′ being 1:2.6:3.0:
11.4 (Figure 3 b). In view of the modified and/or intact
diad linkages, the SiMe2 moieties are classified into four
groups, depending on the chemical shifts of the methyl
carbons (Figure 4): those in two adjacent modified
linkages for A and A′, those in modified linkages that
are adjacent to unmodified linkages for B and B′, those
in unmodified linkages for C and C′ (neighboring to B
and B′, therefore the intensity of B ≈ C and B′ ≈ C′),
and those in unmodified linkages for D and D′ (other
than C and C′). On the basis of the assignment, the
degrees of modification for 10d and 10f are respectively
estimated at 19 and 20%, which are similar to those
F igu r e 6. Time course of the molecular weights of 10b
and 9a upon irradiation by UV light (8 × 10-3 M benzene
solution, low-pressure mercury lamp, monitoring by GPC
with an RI detector).
3.9 × 103, 4.0 × 103, 3.1 × 102, and 3.3 × 102 for the
partially (29%) modified polymer 10b and 1.4 × 104, 1.4
× 104, 1.5 × 103, and 1.6 × 103 for the exhaustively
modified polymer 10a (Figure 5). The existence of new
absorption bands suggests the possibility that photore-
activities of these modified polymers are different from
those of the starting polymers. Indeed, upon irradiation
of a benzene solution of 10b or 9a (8 × 10-3 M) with a
low-pressure mercury lamp, the modified polymer 10b
discontinued the decrease in molecular weight at about
40 min, while degradation of the unmodified polymer
9a was still in progress38 (Figure 6). In addition, 10b
gave a small amount of a fragment with a low molecular
weight (8 × 102 at the peak top) in the early stage of
the reaction (∼10 min), whereas 9a did not form such a
fragment (Figure 7). The fragment, as well as the
residual major fraction, showed a UV spectrum similar
to that for 10b, indicating that the phenanthrene rings
still existed in the backbone (Figure 8).
1
obtained from H NMR and elemental analysis (20 and
21%, respectively). On the other hand, the order of the
intensity, B (B′) > A (A′), indicates that modified
linkages are separated rather than bonded to each
other. Accordingly, the partially modified polymers
10d ,f seem to have random-type copolymeric structures.
P r op er ties of th e Mod ified P olym er s. Polymers
10 exhibit new UV absorption bands arising from the
introduced phenanthrene or benzene rings (ranges of
On the other hand, thermogravimetric analysis (TGA)
of 10a (100% modification), 10b (29% modification), and
9a (parent polymer; 0% modification) revealed that
introduction of phenanthrene rings improved the ther-
mal stability (Figure 9); the temperatures of 5 and 10%
λmax: 297-299, 309-312, 348-350, and 365-367 nm
for phenanthrene rings and 283-287 nm for benzene
rings). In 10a ,b the value of the absorption coefficient
is almost proportional to the degree of modification; the
values at 299, 312, 348, and 366 nm are respectively
(38) Photoreactivity33a and thermal stability (TGA)33b for 9a were
previously examined.

5230 Organometallics, Vol. 16, No. 24, 1997
Yamashita et al.
F igu r e 9. TGA of 10a ,b and 9a (under helium, 10 °C/min
raising rate).
controlling the physicochemical properties of Si-Si-
bond-containing polymers.
Exp er im en ta l Section
NMR spectra were measured on Bruker AC-200 (1H and
13C), Bruker ARX-300 (29Si), and J EOL FX-90 (31P) instru-
ments (200 MHz for 1H, 50.3 MHz for 13C, 59.6 MHz for 29Si,
and 36.2 MHz for 31P). The NMR solvent is CDCl3 unless
otherwise noted. Chemical shifts are referred to Me4Si (0
ppm), CHCl3 (7.25 ppm), C6D5H (7.16 ppm), or C6D4HCD3 (6.97
ppm) for 1H NMR, CDCl3 (77.0 ppm) or C6D6 (128.0 ppm) for
13C NMR, Me4Si (0 ppm) for 29Si NMR, and H3PO4 (85%
solution in D2O, 0 ppm) for 31P NMR. IR spectra were recorded
on J ASCO A-302 and/or J ASCO FT/IR-5000 spectrometers. UV
spectra were measured on a Shimadzu UV-3100 spectrometer.
GC-(HR)MS analyses (EI, 70 eV) were performed on Shi-
madzu QP-1000 and/or J EOL DX-303 spectrometers. Molec-
ular weights of polymers were measured with a GPC system
equipped with a high-pressure Shimadzu LC-6A pump, Shodex
KF-80M, KF-802, and KF-801 columns, and Shimadzu RID-
2A or Shodex SE-61 (RI) and/or Shimadzu SPD-M1A (UV)
detectors using THF eluent and polystyrene standards. TGA
was performed with a Shimadzu TG-30 system.
F igu r e 7. Time dependence of the GPC curves of (a) 10b
and (b) 9a upon irradiation by UV light (8 × 10-3
M
benzene solution, low-pressure mercury lamp, monitoring
with a UV detector at 270 nm).
Every liquid starting material or solvent was dried with an
appropriate agent (molecular sieves 4A, sodium, etc.) and
distilled in vacuo or under nitrogen. 1,1,2,2-Tetramethyl-1,2-
diphenyldisilane (1b) was purchased and distilled in vacuo.
1,1,2,2-Tetramethyl-1,2-disilacyclohexane39 (1c), 1,2-difluoro-
1,1,2,2-tetramethyldisilane40 (1d ), and octamethyltrisilane41
(1e) were prepared according to the literature. p-Benzo-
quinone (2a ) and 1,2-naphthoquinone (2e) were recrystallized
from hexane. 1,4-Naphthoquinone (2c) was sublimed and
subsequently recrystallized from benzene. Chloranil (2b),
9,10-anthraquinone (2d ), and 9,10-phenanthraquinone (2f)
were used as purchased. PdCl2(PPh3)2,42 PdCl2(PMe3)2,43
PdCl2(PhCN)2,44 Pd(dba)2,45 Pd(PPh3)4,46 (p-benzoquinone)Pd-
F igu r e 8. UV spectra of the degraded polymer of 10b (UV
irradiation for 40 min) at the molecular weights of 2.4 ×
104 (X) and 8 × 102 (Y) (Figure 7; in GPC (THF eluent)
using a UV detector with a photodiode array).
weight loss (modification degree, %) under helium at a
10 °C/min raising rate were respectively 455 and 465
°C (0), 470 and 485 °C (29), and 480 and 510 °C (∼100).
This indicates the possibility of offering a new class of
heat-resistant materials by insertion of quinones having
thermally stable aromatic rings.
In conclusion, insertion of 1,2- or 1,4-quinones into
nonactivated Si-Si bonds proceeds in the presence of
palladium catalysts such as PdCl2L2 (L ) PEt3, PPh3,
etc.) and Pd(dba)2-2P(OCH2)3CEt to give various 1,2-
and 1,4-bis(siloxy) aromatic compounds. The process
was successfully applied to the modification of Si-Si-
bond-containing polymers by direct insertion of quinones
into their backbones. Since the modified polymers
exhibit unique photochemical and thermal properties,
the present reaction provides a new methodology for
(39) Kumada, M.; Tamao, K.; Takubo, T.; Ishikawa, M. J . Orga-
nomet. Chem. 1967, 9, 43.
(40) Kumada, M.; Yamaguchi, M.; Yamamoto, Y.; Nakajima, J .;
Shiina, K. J . Am. Chem. Soc. 1956, 21, 1264.
(41) Kumada, M.; Ishikawa, M. J . Organomet. Chem. 1963, 1, 153.
(42) King, A. O.; Negishi, E.; Villani, F. J ., J r.; Silveira, A., J r. J .
Org. Chem. 1978, 43, 358.
(43) Evans, J . G.; Goggin, P. L.; Goodfellow, R. T.; Smith, J . G. J .
Chem. Soc. A 1968, 464.
(44) Doyle, J . R.; Slade, P. E.; J onassen, H. B. Inorg. Synth. 1960,
6, 216.
(45) Ukai, T.; Kawazura, H.; Ishii, Y. J . Organomet. Chem. 1974,
65, 253.

Pd-Catalyzed Insertion of Quinones into Si-Si Bonds
Organometallics, Vol. 16, No. 24, 1997 5231
25
27
(PPh3)2 (7), cis-(PhMe2Si)2Pt(PMe2Ph)2 (8a ), and cis-
73 (100), 45 (38); GC-HRMS calcd for C12H18Cl4O2Si2 389.9598,
found 389.9614.
29
(FMe2Si)2Pt(PEt3)2 (8b) were synthesized by the literature
47
48
reactions. PdCl2(PiBu3)2 and PdCl2(PEt3)2 were prepared
by treatment of PdCl2(PhCN)2 with 2 equiv of the correspond-
ing phosphines according to the reported procedure.49 PPh3
was recrystallized from ethanol. P(OCH2)3CEt was distilled
and subsequently recrystallized from hexane. Poly[(1,2-di-
methyl-1,2-diphenyldisilanylene)(p-phenylene)]33a (9a ), poly-
[(tetramethyldisilanylene)ethylene]4a (9b), and poly(tetrameth-
yldisiloxane)35 (9c) were prepared according to the literature.
Poly(dimethylsilylene) (11) was obtained from Nippon Soda
Co. Ltd.
3f: 1H NMR δ 0.28 (s, 18H, SiCH3), 7.50-7.66 (m, 4H, ring
2,3,6,7-H), 8.05-8.17 (m, 2H, ring 1,8-H), 8.58-8.69 (m, 2H,
ring 4,5-H); 13C NMR δ 0.1 (SiC), 120.5 (4C), 149.4 (2C); GC-
MS m/ z (relative intensity) 366 (100, M+), 266 (38), 73 (74),
45 (20); GC-HRMS calcd for C20H26O2Si2 354.1471, found
354.1470.
4a : 1H NMR δ 0.22 (s, 9H, SiCH3), 4.37 (s, 1H, OH), 6.70
(s, 4H, C6H4) (addition of D2O diminished the signal at 4.38
ppm); MS m/ z (relative intensity) 182 (46, M+), 167 (100); GC-
HRMS calcd for C9H14O2Si 182.0763, found 182.0758.
4e: a mixture of 2-(trimethylsiloxy)-1-naphthol and 1-(tri-
methylsiloxy)-2-naphthol (ratio of the two regioisomers A:B
Ca ta lytic Rea ction s. Each reaction of a Si-Si-bonded
compound with a quinone was carried out at 120 or 100 °C
under nitrogen in a sealed glass tube (6 mm i.d.).
1
≈ 1:4); H NMR δ 0.33 (isomer A) and 0.36 (B) (each s, 9H,
Rea ction s of 1a w ith 2a -f. A typical procedure is as
follows (Table 1, run 5). A mixture of 1a (0.44 mmol), 2a (0.40
mmol), PdCl2(PPh3)2 (0.008 mmol), and benzene (0.05 mL) was
heated at 120 °C for 1 h. GC and GC-MS analyses showed
almost complete consumption of 2a and formation of p-
bis(trimethylsiloxy)benzene (3a ; ∼0.40 mmol, ∼100% yield).
In a separate reaction under the same conditions, concentra-
tion of the reaction mixture followed by Kugelrohr distillation
gave 3a (0.38 mmol, 95% yield).
Similarly, 1,2,4,5-tetrachloro-3,6-bis(trimethylsiloxy)ben-
zene (3b; ∼65% yield, ∼90% purity), 1,4-bis(trimethylsiloxy)-
naphthalene (3c; 80% yield), and 9,10-bis(trimethylsiloxy)-
phenanthrene (3f; 95% yield) were respectively isolated in the
reactions of 1a with 2b (PdCl2(PPh3)2 catalyst, 24 h; run 12),
2c (PdCl2(PPh3)2 catalyst, 6 h; run 14), and 2f (Pd(dba)2-
2P(OCH2)3CEt catalyst, 1 h; run 26). Preparative GC was used
to purify 1,2-bis(trimethylsiloxy)naphthalene (3e) (vide infra).
Compounds 3a ,14a,16b 3b,50 3c,14a,50 3d ,50 3e,50 and 3f51 were
identified by NMR, IR, and GC-(HR)MS spectra or by
comparison with the authentic samples.
The reaction of 2a using the Pd(dba)2-2P(OCH2)3CEt
catalyst (run 8) gave 3a (70% yield) and other products (4a ,
5a , P1, and P2) whose GC-(HR)MS parent ions respectively
corresponded to 4-(trimethylsiloxy)phenol, 1,4-bis(trimethyl-
siloxy)-2-(trimethylsilyl)benzene,52 an isomer of 3a with M+
) m/ z 254, and a compound with M+ ) m/ z 434 (1a + 2a ×
2 + Me3Si - H) (GC (TCD) area ratio 3a :4a :5a :P1:P2 ) 100:
10:5:5:3). Preparative GC gave relatively pure 4a (∼60%
purity, a mixture with 3a ) and 5a (∼95% purity). Their NMR
spectra were consistent with the proposed structures.
On the other hand, the reaction of 2b (run 12) gave 3b (70%
yield) and other products (P3 and P4) (GC (TCD) area ratio
3b:P3:P4 ) 100:13:2). GC-MS showed the parent ion for P3
at m/ z 428 (for 35Cl), which corresponded to 1,2,4-trichloro-
3,6-bis(trimethylsiloxy)-5-(trimethylsilyl)benzene, while the
parent ion for P4 was m/ z 356 ()Me3Si × 2 + 35Cl × 3 +
C6O2H).
SiCH3), 5.23 (A) and 5.83 (B) (each s, 1H, OH), 7.08-8.19 (m,
6H, ring protons) (addition of D2O diminished the signals at
5.23 and 5.83 ppm); GC-MS m/ z (relative intensity) 232 (49,
M+), 216 (100), 201 (44), 186 (43), 75 (41); GC-HRMS calcd
for C13H16O2Si 232.0920, found 232.0917.
5a : 1H NMR δ 0.24 (s, 18H, SiCH3), 0.29 (s, 9H, SiCH3),
6.61 (d, J ) 8.6 Hz, 1H, ring H), 6.69 (dd, J ) 8.6, 2.9 Hz, 1H,
ring H), 6.82 (d, J ) 2.9 Hz, 1H, ring H); 13C NMR δ -1.0, 0.2,
and 0.6 (SiCH3), 116.9, 121.1, and 126.2 (aromatic CH), 130.9,
148.6, and 154.6 (quaternary C); IR (neat) 1472 (s), 1260 (s),
1216 (s), 924 (s), 842 (s) cm-1; GC-MS m/ z (relative intensity)
326 (100, M+), 311 (27), 295 (14), 73 (50); GC-HRMS calcd
for C15H30O2Si3 326.1553, found 326.1560.
P1: GC-MS m/ z (relative intensity) 254 (28, M+), 238 (100),
223 (88), 179 (14), 133 (13), 73 (32), 45 (16); GC-HRMS calcd
for C12H22O2Si2 254.1158, found 254.1169.
P2: GC-MS m/ z (relative intensity) 434 (100, M+), 419 (30),
223 (88), 355 (14), 254 (14), 73 (50); GC-HRMS calcd for
C
21H34O4Si3 434.1765, found 434.1766.
P3: GC-MS m/ z (relative intensity) 428 (19, M+ for 35Cl),
413 (9), 270 (16), 93 (16), 73 (100), 45 (23).
P4: GC-MS m/ z (relative intensity) 356 (5, M+ for 35Cl),
269 (100), 267 (95), 113 (44), 93 (26), 73 (19), 63 (27).
Rea ction of 1b w ith 2a . A mixture of 1b (0.80 mmol), 2a
(0.88 mmol), PdCl2(PEt3)2 (0.016 mmol), and benzene (0.20 mL)
was heated at 120 °C for 14 h. GC and GC-MS showed
formation of p-bis(dimethylphenylsiloxy)benzene (3g, 0.71
mmol, 89% yield) and 4-(dimethylphenylsiloxy)phenol (4g,
0.055 mmol, 7%). Florisil column chromatography with ben-
zene eluent gave pure 3g and relatively pure 4g (∼80% purity,
a mixture with 3g) as colorless oils.
3g: 1H NMR δ 0.49 (s, 12H, SiCH3), 6.64 (s, 4H, OC6H4O),
7.37-7.49 and 7.61-7.72 (each m, 6H and 4H, C6H5); 13C NMR
δ -1.2 (SiCH3), 120.5 (OC6H4O), 127.9 (m-C of C6H5), 129.8
(p-C of C6H5), 133.4 (o-C of C6H5), 137.3 (ipso-C of C6H5), 149.3
(SiOC); IR (neat) 1506 (s), 1430 (m), 1256 (s), 1238 (s), 1222
(s), 1122 (s), 920 (s), 840 (s), 810 (s), 792 (s), 742 (m), 730 (m),
702 (s), 666 (m); GC-MS m/ z (relative intensity) 378 (100,
M+), 363 (63), 285 (75), 135 (87), 43 (22). Anal. Calcd for
In the reaction of 2e (run 20), GC-(HR)MS showed forma-
tion of 3e (27% yield) and 2-(trimethylsiloxy)-1-naphthol and
1-(trimethylsiloxy)-2-naphthol (4e; 22%). Preparative GC gave
relatively pure 3e (∼85% purity, a mixture with 4e) and 4e
(∼60% purity, a mixture with 3e).
C
22H26O2Si2: C, 69.79; H, 6.92. Found: C, 69.73; H, 6.90.
4g: 1H NMR (C6D6) δ 0.38 (s, 6H, SiCH3), 3.70 (br s, 1H,
OH), 6.32-6.42 and 6.67-6.77 (each m, each 2H, OC6H4O),
7.12-7.24 and 7.53-7.63 (each m, 3H and 2H, C6H5); GC-
MS m/ z (relative intensity) 244 (100, M+), 229 (91), 151 (32),
135 (66), 43 (23); GC-HRMS calcd for C14H16O2Si 244.0919,
found 244.0929.
Rea ction of 1c w ith 2f. A mixture of 1c (0.60 mmol), 2f
(0.66 mmol), PdCl2(PEt3)2 (0.008 mmol), and benzene (0.15 mL)
was heated at 120 °C for 24 h. 1H NMR showed formation of
3h in ∼100% yield. Florisil column chromatography with
benzene eluent gave nearly pure 3h (0.555 mmol, 93% yield)
as a colorless viscous oil.
3h : 1H NMR δ 0.16 (s, 9H, SiCH3), 0.92-1.07 and 1.83-
2.00 (each m, each 4H, CH2), 7.50-7.67 (m, 4H, ring H), 8.06-
8.17 and 8.58-8.79 (each m, each 2H, ring H); 13C NMR δ -1.5
(SiCH3), 15.7 and 23.6 (CH2), 122.4, 124.8, 126.4, and 128.3
(ring CH), 127.6, 129.9, and 137.8 (ring quaternary C); IR
Spectral data for 3b, 3f, 4a , 4e, 5a , P1, P2, P3, and P4 are
as follows.
3b: 1H NMR δ 0.33 (s, 18H, SiCH3); 13C NMR δ 0.8 (SiC),
124.5 (4C), 144.6 (2C); GC-MS m/ z (relative intensity) 390
(28, M+ for 35Cl), 375 (35), 340 (29), 325 (17), 267 (30), 93 (35),
(46) Coulson, D. R. Inorg. Synth. 1972, 13, 121.
(47) PdCl2(PiBu3)2: mp 150.2-151.5 °C. Anal. Calcd for C24H54Cl2-
P2Pd: C, 49.53; H, 9.35. Found: C, 49.54; H, 9.35.
(48) Mann, F. G.; Purdie, D. J . Chem. Soc. 1935, 1549.
(49) J enkins, J . M.; Verkade, J . G. Inorg. Synth. 1968, 11, 108.
(50) Neumann, G.; Neumann, W. P. J . Organomet. Chem. 1972, 42,
277.
(51) Bouas-Laurent, H.; Lapouyade, R.; Brigand, C.; Desvergne, J .-
P. C.R. Acad. Sci. Paris, Ser. C 1970, 270, 2167.
(52) Duthaler, R. O.; Lyle, P. A.; Heuberger, C. Helv. Chim. Acta
1984, 67, 1406.

5232 Organometallics, Vol. 16, No. 24, 1997
Yamashita et al.
(neat) 1600 (s), 1492 (m), 1450 (s), 1420 (m), 1374 (s), 1356
(s), 1340 (s), 1282 (m), 1252 (s, SiMe), 1228 (m), 1178 (s), 1118
(s), 1064 (s), 1036 (s), 926 (s), 882 (s), 866 (s), 838 (s), 820 (s),
794 (s), 758 (s), 726 (s), 698 (m), 676 (m), 664 (m), 642 (m);
GC-MS m/ z (relative intensity) 380 (66, M+), 266 (100), 236
was concentrated (∼1 mL) and was added dropwise to 2-pro-
panol (∼4 mL). The precipitated solid was separated and dried
in vacuo to give 10a (0.18 mmol monomer unit, 90% yield) with
Mw ) 5.8 × 104 (Mw/Mn ) 3.0).
Similarly, 10b,c were obtained in the reactions of 9a ,b with
2f. The reaction conditions and the yields and the molecular
weights of the polymers after precipitation are shown in Table
2. In the reaction of 9b with 2a , precipitation with benzene-
2-propyl alcohol from the reaction mixture (Mw ) 1.9 × 104,
Mw/Mn ) 2.4) gave a fraction 10e (A) (0.18 mmol monomer
unit, 46% yield) with a higher molecular weight, Mw ) 3.6 ×
104 (Mw/Mn ) 2.6). Concentration of the mother liquor yielded
another fraction 10e (B) (37%) with a lower molecular weight,
Mw ) 1.2 × 104 (Mw/Mn ) 2.0). When 9c was used, the
produced polymers 10d ,f were purified by passage of the
reaction mixtures through short-path Florisil columns (ben-
zene eluent).
(33), 99 (13), 59 (30); GC-HRMS calcd for
C22H28O2Si2
380.1628, found 380.1646.
Rea ction of 1d w ith 2a . A mixture of 1d (0.40 mmol), 2a
(0.44 mmol), PdCl2(PEt3)2 (0.004 mmol), and benzene (0.05 mL)
was heated at 100 °C for 12 h. GC and GC-MS showed
formation of p-bis(fluorodimethylsiloxy)benzene (3i; ∼0.1 mmol,
∼25% yield) and other products (4i, 6i, and P5) whose GC-
(HR)MS parent ions corresponded to those of 4-(fluorodimeth-
ylsiloxy)phenol, bis[4-(fluorodimethylsiloxy)phenoxy]dimethyl-
silane, and difluorodimethylsilane (GC (TCD) area ratio 3i:
4i:6i:P5 ) 100:5:2:95). NMR spectral data for 3i were in
agreement with the reported values.5c
4i: GC-MS m/ z (relative intensity) 186 (100, M+), 171 (73),
79 (33), 77 (55), 49 (19), 47 (31); GC-HRMS calcd for
C8H11FO2Si 186.0512, found 186.0511.
6i: GC-MS m/ z (relative intensity) 428 (100, M+), 395 (33),
243 (34), 77 (21); GC-HRMS calcd for C18H26F2O4Si3 428.1107,
found 428.1121.
In the reaction of 11, a mixture of 11 (1.0 mmol monomer
unit), 2a (1.1 mmol), PdCl2(PEt3)2 (0.01 mmol), and benzene
(0.50 mL) was magnetically stirred at 120 °C for 18 h. Benzene
(∼5 mL) was added to the reaction mixture, and the solution
was filtered. Concentration of the filtrate in vacuo followed
by washing of the residual solid with hexane gave 12 (0.85
mmol monomer unit, 85% yield, Mw ) 1.5 × 104, Mw/Mn ≈ 6).
Reprecipitation with benzene-2-propyl alcohol and slight
evaporation of the solvents provided the fraction 12 (A) (46%)
P5: GC-MS m/ z (relative intensity) 96 (74, M+), 81 (100).
Rea ction of 1e w ith 2a . A mixture of 1e (0.40 mmol), 2a
(0.88 mmol), PdCl2(PEt3)2 (0.016 mmol), and benzene (0.10 mL)
was heated at 120 °C for 12 h. GC and GC-MS showed
formation of 3a (0.12 mmol, 30%), 4a (0.08 mmol, 20%), and a
compound (6j) whose GC-(HR)MS parent ion corresponded
to dimethylbis[4-(trimethylsiloxy)phenoxy]silane (GC area
ratio 3a :6j ) 5:e2). GPC of the reaction mixture showed a
peak with Mw ≈ 8 × 102 (Mw/Mn ≈ 1).
with a higher molecular weight, Mw ) 2.3 × 104 (Mw/Mn
)
3.8).
Appearance and physical, spectral, and analytical data for
10a -f and 12 are as follows.
10a : off-white solid; softening temperature 177-195 °C; 1H
NMR δ 0.47 (br s, 6H, SiCH3), 7.03-7.63 (m, 18H, benzene
and phenanthrene ring H), 7.73-7.95 and 8.37-8.60 (each m,
4H, phenanthrene ring H); 13C NMR δ -2.3 and -2.2 (2C,
SiCH3), 122.1 (2C), 123.3 (2C), 124.8 (2C), 125.8 (2C), 127.6
(4C), 128.3 (2C), 129.2 (2C), 129.8 (2C), 133.7 (4C), 134.6 (4C),
135.2 (2C), 137.0 (2C), 137.4 (2C); IR (KBr) 1600 (m), 1492
(m), 1450 (m), 1426 (m), 1370 (m), 1340 (m), 1256 (m), 1176
(m), 1136 (s), 1114 (s), 1064 (m), 1034 (m), 924 (m), 840 (m),
784 (s), 756 (s), 736 (m), 724 (m), 698 (m), 516 (m) cm-1; UV
(THF) λmax (ꢀmonomer unit) 259 (5.4 × 104), 273 (2.3 × 104), 299
(1.4 × 104), 312 (1.4 × 104), 348 (1.5 × 103), 366 (1.6 × 103)
nm. Anal. Calcd for C34H28O2Si2: C, 77.82; H, 5.38. Found:
C, 77.25; H, 5.31.
6j: GC-MS m/ z (relative intensity) 420 (100, M+), 195 (14),
73 (64); GC-HRMS calcd for C20H32O4Si3 420.1608, found
420.1593.
Rea ction of 7 w ith 1a . A mixture of 7 (0.0215 mmol), 1a
(0.043 mmol), and benzene-d6 (0.25 mL) was heated under
nitrogen in a sealed NMR tube at 120 °C for 23 h. 1H NMR
showed almost no reactions taking place (yield of 3a e1%,
g90% recovery of 7). When a mixture of 7 (0.021 mmol), 1a
(0.042 mmol), 2c (0.021 mmol), and benzene-d6 (0.25 mL) was
1
heated at 120 °C for 9 h, H NMR and GC showed formation
of a small amount of 3a (∼4% yield) with recovery of 7 (g90%).
Rea ction of 8a w ith 2a . A mixture of 8a (0.0075 mmol),
2a (0.015 mmol), and benzene-d6 (0.30 mL) was heated under
nitrogen in a sealed NMR tube at 80 °C for 5 min. NMR and
GC showed almost complete consumption of 8a and formation
of 3g (60% yield), 4g (35%), and a platinum complex that
appeared to be (p-benzoquinone)Pt(PMe2Ph)2:53 1H NMR δ
1.24 (d, J PH ) 9.8 Hz, J PtH ) 34.0 Hz, 12 H, PCH3), 5.44 (t,
J PH ) 2.4 Hz, J PtH ) 24.5 Hz, 4H, OC6H4O); 31P NMR δ -13.0
10b: off-white solid; softening temperature 145-155 °C; 1H
NMR δ 0.40-0.88 (m, SiCH3), 7.03-7.76 (m, benzene and
phenanthrene ring H), 7.76-7.91 and 8.35-8.58 (each m,
phenanthrene ring H); IR (KBr) 1600 (m), 1496 (m), 1454 (m),
1430 (s), 1374 (m), 1340 (m), 1248 (m), 1178 (m), 1114 (s), 1066
(m), 1038 (m), 928 (m), 840 (m), 784 (s), 772 (s), 758 (s), 736
(s), 696 (s), 500 (s) cm-1; UV (THF) λmax (ꢀmonomer unit) 258 (2.8
× 104), 299 (3.9 × 103), 312 (4.0 × 103), 348 (3.1 × 102), 366
1
(s, J PtP ) 3745 Hz).
(3.3 × 102) nm. Anal. Calcd for (C34H28O2Si2)0.29(C20H20Si2)0.71
:
Rea ction of 8b w ith 2a . To a toluene-d8 (0.70 mL) solution
of 8b (0.061 mmol) placed in a Schlenk tube cooled to -50 °C
was added 2a (0.061 mmol) under nitrogen. The suspension
was warmed to room temperature over ∼3 h. 1H NMR of the
supernatant solution displayed the SiMe signals of 8b, 3i, and
other unidentified species in the region 0-0.3 ppm (integral
ratio of the SiMe protons 8b:3i:others ≈ 18:1:3). GC and GC-
MS showed formation of 3i as the major volatile product.
When the reaction was carried out in benzene-d6 from room
temperature to 120 °C, NMR and GC-MS showed formation
of a complex mixture, and 3i was not detected.
Rea ction s of 9a -c a n d 11 w ith 2a ,f. A typical procedure
is as follows. A mixture of 9a (Mw ) 4.6 × 104, Mw/Mn ) 2.6,
0.20 mmol monomer unit), 2f (0.21 mmol), Pd(dba)2 (0.004
mmol), P(OCH2)3CEt (0.008 mmol), and benzene (0.10 mL) was
heated at 120 °C for 3 h. Benzene (4 mL) was added to the
reaction mixture, and the solution was filtered. The filtrate
C, 76.67; H, 5.97. Found: C, 76.68; H, 5.95.
1
10c: off-white solid; softening temperature 82-90 °C; H
NMR δ 0.08 (s, 12H, SiCH3), 0.61 (s, 4H, SiCH2CH2), 7.37-
7.52, 7.92-8.04, and 8.44-8.59 (each m, ring H, 8H); 13C NMR
δ -1.7 (4C, SiCH3), 8.6 (2C, CH2), 122.3 (2C), 122.6 (2C), 124.8
(2C), 126.1 (2C), 127.5 (2C), 129.7 (2C), 137.2 (2C); IR (KBr)
1601 (m), 1491 (m), 1452 (m), 1423 (m), 1373 (m), 1357 (m),
1340 (m), 1253 (m), 1180 (m), 1137 (m), 1118 (m), 1065 (m),
1035 (m), 926 (m), 820 (s), 793 (m), 754 (s), 725 (m) cm-1; UV
(THF) λmax (ꢀmonomer unit) 258 (4.1 × 104), 273 (1.5 × 104), 299
(8.8 × 103), 311 (9.4 × 103), 350 (9.6 × 102), 367 (9.8 × 102)
nm. Anal. Calcd for C20H24O2Si2: C, 68.13; H, 6.86. Found:
C, 68.08; H, 6.66.
10d : off-white gummy solid; softening temperature 50-59
°C; 1H NMR δ -0.10-0.36 (m, SiCH3), 7.10-7.67, 8.01-8.30,
and 8.44-8.71 (each m, ring H); 13C NMR δ -0.2, 0.4, 1.4, and
2.0 (SiCH3), 122.2, 123.1, 123.4, 124.8, 126.2, 127.6, 129.5,
129.8, 136.4, and 136.7 (ring C); IR (neat) 1620 (m), 1603 (m),
1493 (m), 1456 (m), 1425 (m), 1404 (m), 1375 (m), 1357 (m),
(53) For some (p-quinone)Pt(PPh3)2 complexes, see: Cenini, S.; Ugo,
R.; Monica, G. L. J . Chem. Soc. A 1971, 416.

Pd-Catalyzed Insertion of Quinones into Si-Si Bonds
Organometallics, Vol. 16, No. 24, 1997 5233
1342 (m), 1251 (s), 1183 (m), 1116 (m), 1063 (s), 1036 (s), 932
P h otor ea ctivities of 10b a n d 9a . A stirred benzene (1
mL) solution of 10b or 9a (0.008 mmol monomer unit) under
nitrogen in a quartz cell was irradiated with a low-pressure
mercury lamp (EIKOHSHA, EL-S-SQ 30W) that was placed
at a distance of 15 cm from the cell. At reaction times of 10,
40, and 100 min, irradiation was discontinued, and a portion
(20 µL) of the solution was taken out by a syringe. The
solution was concentrated by nitrogen stream, and the residue
was analyzed by GPC. The values of Mw (irradiation time,
min) were 5.2 × 104 (0), 3.8 × 104 (10), 3.1 × 104 (40), and 2.9
× 104 (100) for 10b and 4.6 × 104 (0), 3.7 × 104 (10), 2.9 × 104
(40), and 1.6 × 104 (100) for 9a (Figures 6-8).
(m), 843 (s), 804 (s), 766 (s), 725 (m), 681 (m), 646 (m) cm-1
;
UV (THF) λmax (ꢀmonomer unit) 257 (1.2 × 104), 273 (4.0 × 103),
297 (2.6 × 103), 309 (2.9 × 103), 348 (2.3 × 102), 365 (2.2 ×
102) nm. Anal. Calcd for (C18H20O3Si2)0.20(C4H12OSi2)0.80: C,
46.95; H, 7.88. Found: C, 46.89; H, 7.68.
10e (A): off-white solid; softening temperature 76-79 °C;
1H NMR δ 0.20 (s, 12H, SiCH3), 0.67 (s, 4H, SiCH2CH2), 6.67
(s, 4H, ring H); 13C NMR δ -2.1 (4C, SiCH3), 7.8 (2C, CH2),
120.5 (4C), 149.4 (2C); IR (KBr) 1506 (s), 1470 (m), 1367 (m),
1253 (s), 1226 (s), 1131 (m), 1052 (m), 922 (s), 835 (s), 785 (s),
756 (m), 717 (m), 526 (m) cm-1; UV (THF) λmax (ꢀmonomer unit
)
287 (2.4 × 103) nm. Anal. Calcd for C12H20O2Si2: C, 57.09;
Th er m ogr a vim etr ic An a lyses of 10a ,b a n d 9a . The
measurements were carried out under helium in the range of
room temperature to 900 °C at a raising rate of 10 °C/min.
The temperatures of 5 and 10% weight loss were 480 and 510
°C for 10a , 470 and 485 °C for 10b, and 455 and 465 °C for 9a
(Figure 9). The weights of the residues after heating to 900
°C were 32, 38, and 44% for 10a ,b and 9a , respectively.
H, 7.98. Found: C, 56.80; H, 7.87.
10f: pale brown viscous oil; 1H NMR δ 0.11-0.24 (m,
SiCH3), 6.72 (br s, ring H); 13C NMR δ -0.7, -0.3, 1.5, 2.0
(SiCH3), 120.36 and 120.42 (o-C), 148.6 and 149.1 (ipso-C); IR
(KBr) 1506 (s), 1404 (m), 1251 (s), 1054 (s), 932 (s), 835 (s),
816 (s), 799 (s), 766 (s), 681 (m), 646 (m) cm-1; UV (THF) λmax
(ꢀmonomer unit) 283 (5.2 × 102) nm. Anal. Calcd for (C10H16O3-
Si2)0.21(C4H12OSi2)0.79: C, 40.76; H, 8.35. Found: C, 40.74; H,
8.05.
Ack n ow led gm en t. We are grateful to the J apan
Science and Technology Corporation (J ST) for partial
financial support through the CREST (Core Research
for Evolutional Science and Technology) program.
12 (A): sticky brown solid; 1H NMR (C6D6) δ 0.22 (br s, 6H,
SiCH3), 6.91 (br s, 4H, ring H); 13C NMR (C6D6) δ -2.5 (2C,
SiC), 120.9 (4C), 149.5 (2C); 29Si NMR (C6D6) δ -5.2; IR (KBr)
1502 (s), 1263 (m), 1234 (m), 1214 (s), 936 (s), 839 (s), 806 (m)
cm-1. Anal. Calcd for C8H10O2Si: C, 57.80; H, 6.06. Found:
C, 58.45; H, 5.43.
OM970215Q