Synthesis of cooligomers of titanium-bridged silsesquioxanes and octakis(hydridosilsesquioxane)

Article abstract of DOI:10.1246/cl.2000.1332

New titanium-bridged silsesquioxanes having olefinic groups, Ti[(c-C₅H₉)₇Si₇O₁₂(SiMe₂R)]₂ (R = vinyl, allyl), react with octakis(hydridosilsesquioxane) under hydrosilylation reac

Full text of DOI:10.1246/cl.2000.1332

1332
Chemistry Letters 2000
Synthesis of Cooligomers of Titanium-Bridged Silsesquioxanes and
Octakis(hydridosilsesquioxane)
Kenji Wada, Koichi Yamada, Daisuke Izuhara, Teruyuki Kondo, and Take-aki Mitsudo*
Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501
(Received September 1, 2000; CL-000818)
New titanium-bridged silsesquioxanes having olefinic
groups, Ti[(c-C5H9)7Si7O12(SiMe2R)]2 (R = vinyl, allyl), react
with octakis(hydridosilsesquioxane) under hydrosilylation reac-
tion conditions to give oligomeric materials. The local struc-
ture around the titanium atoms of the starting silsesquioxanes is
unchanged even in the oligomeric materials.
local C2-symmetry of their siloxane frameworks.
The hydrosilylation of olefinic groups in titanium-bridged
silsesquioxane 1b or 1c with 0.5 equiv of octakis(hydrido-
silsesquioxane) (H8Si8O12, 4)11 in the presence of a Pt2(dvs)3
catalyst (2 mol% as Pt, dvs = divinyltetramethyldisiloxane) in
toluene at room temperature for 24 h afforded cooligomers, 5b
or 5c, respectively (see eq 2). The produced cooligomers are
Metal-containing oligosilsesquioxanes have attracted atten-
tion from the viewpoint of their role as well-defined, homoge-
neous models for the active surface sites of the supported cata-
lysts or metal-containing zeolites.1 Among them, recent inter-
est has been focused on the catalytic activities of titanium-con-
taining silsesquioxanes2 including Ti[(c-C5H9)7Si7O12(SiMe3)]2
(1a)2a,b for epoxidation of olefins as a soluble analog of
titanosilicates.3 On the other hand, silsesquioxanes and sphero-
silicates of cage-like core structures are expected to be candi-
dates for building blocks of novel organic–inorganic hybrid
materials, and porous or heat-resistant materials are produced
by the hydrosilylation polymerization of T8 cubes.4,5
Therefore, introduction of appropriate functional groups into
metallasilsesquioxanes is of interest. We have recently reported
the synthesis and functionalization of a series of metallocene-
containing silsesquioxanes with a vinyl group.6 Note that there
are reports on the catalytic activities of polymeric materials pro-
duced from a silsesquioxane diol and metallic species.2c,7
highly soluble in THF, toluene, and hexane.
The GPC analysis of crude 5b showed the oligomer forma-
tion (Mw = 45000, Mn = 9200 based on polystyrene standards).
The profile of 5b consists of a large peak in a high Mw region
(Mw = 200000–10000) together with several low Mw peaks (Mw
= 6000). A very small shoulder was found at around Mw
=
2000, indicating only a trace amount of unreacted 1b remained
in the crude mixture. In addition, there was no sign of unreact-
ed 4. Note that the reaction of 1b with an equimolar amount of
4 only produced a low molecular weight species (Mw = 9600,
Mn = 2700). The oligomer 5c shows higher Mw of 63000, but
the molecular weight distribution is broader (Mn = 6600).
1
In the present communication, new titanium-bridged
silsesquioxanes with olefinic moieties, Ti[(c-C5H9)7Si7O12-
(SiMe2R)]2, R = vinyl (1b) or allyl (1c), are synthesized, and
the hydrosilylative oligomerization of these compounds with
octakis(hydridosilsesquioxane) is reported.
The IR and H-NMR study revealed that about half of the
SiH groups of 4 remained in both 5b and 5c. According to the
13C-NMR (DEPT) spectra, the silylation cleanly occurred at the
terminal carbon atoms of the olefinic groups with excellent
regioselectivity. No other possible regioisomeric connection
The reaction of disilanols having an olefinic group ((c-
C5H9)7Si7O10(SiMe2R)(OH)2, R = vinyl (2b),6 allyl (2c)8),
which were prepared by the controlled silylation of a
silsesquioxane triol (c-C5H9)7Si7O9(OH)3 3,1 with
tetrakis(diethylamino)titanium in benzene at room temperature,
produced titanium-bridged silsesquioxanes 1b (68%)9 or 1c
(62%),10 respectively. The structures of 1b and 1c were deduced
1
on the basis of H,- 13C-, 29Si-NMR, and FAB mass analyses.
The 29Si-NMR spectrum of 1b consists of eight peaks of almost
the same intensity for sixteen silicon atoms, indicating apparent
Copyright © 2000 The Chemical Society of Japan

Chemistry Letters 2000
1333
3
4
I. W. C. E. Arends, R. A. Sheldon, M. Wallau, and U. Schuchardt,
Angew. Chem., Int. Ed. Engl., 36, 1144 (1997) and references therein.
C. Zhang, F. Babonneau, C. Bonhomme, R. M. Laine, C. L. Soles, H.
A. Hristov, and A. F. Lee, J. Am. Chem. Soc., 120, 8380 (1998).
T. Kobayashi, T. Hayashi, and M. Tanaka, Chem. Lett., 1998, 763.
K. Wada, M. Bundo, D. Nakabayashi, N. Itayama, T. Kondo, and T.
Mitsudo, Chem. Lett., 2000, 628.
was detected by NMR.
The materials in the present work include only a specific
titanium species. The 29Si-NMR peaks of 5b and 5c in the T-
silicon region were very similar to those of 1b and 1c, respec-
tively, although broadening was observed (Figure 1). In addi-
tion, no 29Si-peaks were found in the region of –50 to –60 ppm1
even after the treatment with methanol followed by the column
chromatography to remove the Pt catalyst, indicating the
absence of silanols formed by cleavage of the Ti–O–Si bonds.
The UV spectra of 5b and 5c displayed a sharp absorption band
at 210 nm, characteristic of a tetrahedrally coordinated,
monomeric titanium species,2b almost identical to the case with
1b and 1c (λmax = 210 nm). Therefore, the local structure
around the titanium atoms of 5b or 5c is estimated to be very
similar to those of 1b or 1c. These results suggest the structures
5
6
7
8
H. C. L. Abbenhuis, H. W. G. van Herwijnen, and R. A. van Santen,
Chem. Commun., 1996, 1941.
2c: A disilanol (c-C6H11)7Si7O10(SiMePhCH=CH2)(OH)2 has been
prepared from [PPh3Me]+[(c-C6H11)7Si7O12H2]– (F. J. Feher and S. H.
Phillips, J. Organomet. Chem., 521, 401 (1996)). Alternatively, to a
solution of 3 (10.5 g, 12.0 mmol) and triethylamine (5.0 cm3, 36
mmol) in THF (70 cm3), allylchlorodimethylsilane (1.1 cm3, 7.2
mmol) in THF (30 cm3) was dropwise added and stirred at room tem-
perature for 18 h. Filtration followed by evaporation leave a white
solid. This was extracted with pentane (100 cm3) to give a clear fil-
trate and a white solid. From the pentane-insoluble solid, 4.8 mmol
of unreacted 3 was recovered, and from the filtrate the solvent was
evaporated. The product was obtained by recrystallization by slow
diffusion of acetonitrile into a benzene solution. Yield 98%. mp
166.0–168.0 °C; 1H NMR (300 MHz, CDCl3, 25 °C) δ 5.83 (ddt, 3J
3
= 17.1, 9.7, 8.1 Hz, 1H, SiCH2CH=CH2), 4.91 (d, J = 17.1 Hz, 1H,
trans-CH2CH=CH2), 4.87 (d, 3J = 9.7 Hz, 1H, cis-CH2CH=CH2),
4.01 (br, 2H, SiOH), 1.75–1.50 (br m, 58H, CH2 of Cy and
SiCH2CH=CH2), 1.06–0.92 (br m, 7H, CH of Cy), 0.16 (s, 6H,
Si(CH3)2); 13C{1H} NMR (75 MHz, CDCl3, 25 °C) δ 134.35
(SiCH2CH=CH2), 113.71 (SiCH2CH=CH2), 27.57, 27.45, 27.40,
27.34, 27.26, 27.24, 27.09, 27.02, 27.00, 26.88, 26.84 (CH2 of Cy),
25.89 (SiCH2CH=CH2), 23.69, 22.82, 22.46, 22.27, 22.20 (1:2:2:1:1
for CH of Cy), –0.50 (Si(CH3)2); 29Si{1H} NMR (76 MHz, CDCl3,
0.2 M Cr(acac)3, 25 °C) δ 7.73, –56.62, −65.57, −66.43, −67.36
(1:2:2:1:2). Anal. Calcd for C40H76O12Si8 (973.73): C, 49.34; H,
7.87%. Found C, 49.36; H, 7.64%.
9
1b: To a solution of 2b (768 mg, 0.8 mmol) in dry benzene (30 cm3),
tetrakis(diethylamino)titanium (135 mg, 0.4 mmol) in dry benzene
(15 cm3) was dropwise added and stirred at room temperature for 6 h.
After the solvent was evaporated, the resulting off-white solid was
extracted with hexane (30 cm3). Filtration by using a 0.45 µm PTFE
filter gave a clear solution. After evaporation, 1b was obtained by
recrystallization by slow diffusion of acetone into a benzene solution.
Yield 68%. mp 267.5–268.0 °C; 1H NMR (300 MHz, CDCl3, 25 °C)
3
3
δ 6.16 (dd, J = 20.2, 14.9 Hz, 2H, SiCH=CH2), 5.93 (dd, J = 14.9
Hz, 2J = 4.0 Hz, 2H, cis-SiCH=CH2), 5.74 (dd, 3J = 20.2 Hz, 2J = 4.0
Hz, 2H, trans-SiCH=CH2), 1.89–1.43 (br m, 112 H, CH2 of Cy),
1.02–0.85 (br m, 14 H, CH of Cy), 0.24 (s, 6H, Si(CH3)2), 0.23 (s, 6
H, Si(CH3)2); 13C{1H} NMR (75 MHz, CDCl3, 25 °C) δ 139.37
(SiCH=CH2), 131.58 (SiCH=CH2), 27.76, 27.61, 27.50, 27.36, 27.33,
27.16, 27.11, 27.06, 26.96, 26.93 (CH2 of Cy), 24.30, 23.46, 23.12,
23.08, 23.00, 22.44, 22.33 (1:1:1:1:1:1:1 for CH of Cy), 0.45, 0.36
(Si(CH3)2); 29Si{1H} NMR (76 MHz, CDCl3, 0.2 M Cr(acac)3, 25
°C) δ –2.12, –65.24, –65.76, –66.11, –67.12, –68.05, –68.15, –68.28
(1:1:1:1:1:1:1:1). MS (FAB+) m/z 1892 (7) [M – C5H10]+, 861 (100).
Anal. Calcd for C78H144O24Si16Ti (1963.25): C, 47.72; H, 7.39%.
Found C, 47.28; H, 7.76%.
of oligomers exemplified in Figure 2.
In conclusion, hydrosilylation between octakis(hydrido-
silsesquioxane) and new titanium-bridged silsesquioxanes with
olefinic groups afforded novel oligomeric materials. These
oligomers are estimated to possess a titanium species very simi-
lar to that in 1b or 1c. They would be appropriate precursors of
organic–inorganic hybrid materials for the catalysts with
titanosilicate-like active sites,3 or porous oxides with uniformly
controlled micropores.12
10 1c: Yield 62%. mp 288.0–289.0 °C; 1H NMR (300 MHz, CDCl3, 25
°C) δ 5.80 (ddt, 3J = 17.1, 9.7, 8.1 Hz, 2H, SiCH2CH=CH2), 4.85 (d,
3J = 17.1 Hz, 2H, trans-SiCH2CH=CH2), 4.81 (d, 3J = 9.7 Hz, 2H,
cis-SiCH2CH=CH2), 1.86–1.49 (br m, 116H, CH2 of Cy and
SiCH2CH=CH2), 0.96–0.90 (br m, 14H, CH of Cy), 0.18 (s, 6H,
Si(CH3)2), 0.17 (s, 6H, Si(CH3)2); 13C{1H} NMR (75 MHz, CDCl3,
25 °C) δ 134.69 (SiCH2CH=CH2), 113.04 (SiCH2CH=CH2), 27.78,
27.72, 27.59, 27.48, 27.48, 27.38, 27.34, 27.30, 27.17, 27.09, 27.04,
26.94, 26.90, 26.87 (CH2 of Cy), 26.11 (SiCH2CH=CH2), 24.26,
23.44, 23.14, 23.05, 23.01, 22.40, 22.29 (1:1:1:1:1:1:1 for CH of Cy),
–0.21 (Si(CH3)2); 29Si{1H} NMR (76 MHz, CDCl3, 0.2 M Cr(acac)3,
25 °C) δ 6.53, –65.25, –65.76, –66.16, –67.14, –68.08, –68.27
(1:1:1:1:1:1:2). MS (FAB+) m/z 1948 (12) [M – C3H6]+, 1919 (13),
861 (100). Anal. Calcd for C80H148O24Si16Ti (1991.30): C, 48.25; H,
7.49%. Found C, 47.44; H, 7.39%.
This work is supported in part by a Grant-in-Aid for
Scientific Research (No. 11650807) from the Ministry of
Education, Science, Sports, and Culture. The authors are grate-
ful to Dr. S.-W. Zhang at Osaka University for assistance in
GPC analyses, and Mr. Y. Hisamoto at Kyoto University for his
kind instruction in FAB mass measurements.
References and Notes
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