Photochemical addition of C60 with siliranes: Synthesis and characterization of carbosilylated and hydrosilylated C60 derivatives

Article abstract of DOI:10.1021/ja1049719

Photochemical reactions of C₆₀ with siliranes (1a-d) afford adducts of four types (2a-5b) as carbosilylated and hydrosilylated C ₆₀ derivatives. Characterization of these adducts was conducted using MS, UV, NMR spectroscopy, and single-crystal X-ray analyses. In particular, the first example of the crystal structure of a closed 1,2-adduct at the 5,6-ring junction of the C₆₀ cage is provided by single-crystal X-ray analysis of 3b. Electrochemical analyses also revealed unique redox properties of the products 2b-5b, which depend on the regiochemistry of the functionality, in addition to the substituents on the C₆₀ cage. Theoretical calculations offer bases for the experimentally observed redox properties and relative stabilities of the silylated products.

Full text of DOI:10.1021/ja1049719

Published on Web 08/10/2010
Photochemical Addition of C60 with Siliranes: Synthesis and
Characterization of Carbosilylated and Hydrosilylated C60
Derivatives
Junko Nagatsuka,† Sachie Sugitani,† Masahiro Kako,‡ Tsukasa Nakahodo,†
Naomi Mizorogi,† Midori O. Ishitsuka,† Yutaka Maeda,§ Takahiro Tsuchiya,†
Takeshi Akasaka,*,† Xingfa Gao,| and Shigeru Nagase|
Center for Tsukuba AdVanced Research Alliance, UniVersity of Tsukuba,
Tsukuba 305-8577, Japan, Department of Applied Physics and Chemistry, The UniVersity of
Electro-Communications, Chofu 182-8585, Japan, Department of Chemistry, Tokyo Gakugei
UniVersity, Koganei 184-8501, Japan, and Department of Theoretical and Computational
Molecular Science, Institute for Molecular Science, Okazaki 444-8585, Japan
Received June 7, 2010; E-mail: akasaka@tara.tsukuba.ac.jp
Abstract: Photochemical reactions of C60 with siliranes (1a-d) afford adducts of four types (2a-5b) as
carbosilylated and hydrosilylated C60 derivatives. Characterization of these adducts was conducted using
MS, UV, NMR spectroscopy, and single-crystal X-ray analyses. In particular, the first example of the crystal
structure of a closed 1,2-adduct at the 5,6-ring junction of the C60 cage is provided by single-crystal X-ray
analysis of 3b. Electrochemical analyses also revealed unique redox properties of the products 2b-5b,
which depend on the regiochemistry of the functionality, in addition to the substituents on the C60 cage.
Theoretical calculations offer bases for the experimentally observed redox properties and relative stabilities
of the silylated products.
Scheme 1
Introduction
Much attention has been devoted to the chemical derivati-
zation of fullerenes, which continuously yields fascinating
results. Numerous studies of the fullerenes derivatized with
various substituents have been reported, demonstrating applica-
tions for functionalized materials such as electronic devices.1
To date, we have developed the functionalization of fullerenes
and endohedral metallofullerenes using several reactive com-
pounds under both thermal and photochemical conditions
(Scheme 1).2-11 We have also demonstrated that introduction
of electropositive silyl groups onto the outer surfaces of
fullerenes perturbed the electronic characteristics.2–6 For in-
stance, the redox properties of the silylated C60 derivatives are
changed substantially from those of C60 and of other C60
† University of Tsukuba.
‡ The University of Electro-Communications.
§ Tokyo Gakugei University.
| Institute for Molecular Science.
(1) (a) Hirsch, A. The Chemistry of the Fullerenes; Georg Thieme Verlag:
Stuttgart, 1994. (b) Taylor, R. The Chemistry of Fullerenes; World
Scientific: Singapore, 1995. (c) Hirsch, A. Synthesis 1995, 895–913.
(d) Averdung, J.; Torres-Garcia, G.; Luffmann, H.; Schlachter, I.;
Mattay, J. Fullerenes, Nanotubes, Carbon Nanostructures 1996, 4,
633–654. (e) Langa, F.; Nierengarten, J. F. Fullerenes: Principles and
Applications; RSC Publishing: London, 2007. (f) Hirsch, A. Fullerenes
and Related Structures; Springer: Berlin, 1999. (g) Endofullerenes: A
New Family of Carbon Clusters; Akasaka, T., Nagase, S., Eds.;
Kluwer: Dordrecht, The Netherlands, 2002. (h) Wakahara, T.; Kako,
M.; Maeda, Y.; Akasaka, T.; Kobayashi, K.; Nagase, S. Curr. Org.
Chem. 2003, 7, 927–943. (i) Martin, N. Chem. Commun. 2006, 2093–
2104. (j) Dunsch, L.; Yang, S. Phys. Chem. Chem. Phys. 2007, 46,
881–891. (k) Dunsch, L.; Yang, S. Small 2007, 3, 1298–1320. (l)
Chaur, M. N.; Melin, F.; Ortiz, A. L.; Echegoyen, L. Angew. Chem.,
Int. Ed. 2009, 48, 7514–7538. (m) Tan, Y.-Z.; Xie, S.-Y.; Huang, R.-
B.; Zheng, L.-S. Nat. Chem. 2009, 1, 450–460. (n) Yamada, M.;
Akasaka, T.; Nagase, S. Acc. Chem. Res. 2010, 43, 92–102.
(2) (a) Akasaka, T.; Ando, W.; Kobayashi, K.; Nagase, S. J. Am. Chem.
Soc. 1993, 115, 1605–1606. (b) Akasaka, T.; Mitsuhida, E.; Ando,
W.; Kobayashi, K.; Nagase, S. J. Chem. Soc., Chem. Commun. 1995,
1529–1530.
(3) (a) Akasaka, T.; Ando, W.; Kobayashi, K.; Nagase, S. J. Am. Chem.
Soc. 1993, 115, 10366–10367. (b) Suzuki, T.; Maruyama, Y.; Akasaka,
T.; Ando, W.; Kobayashi, K.; Nagase, S. J. Am. Chem. Soc. 1994,
116, 1359–1363. (c) Akasaka, T.; Mitsuhida, E.; Ando, W.; Kobayashi,
K.; Nagase, S. J. Am. Chem. Soc. 1994, 116, 2627–2628. (d) Akasaka,
T.; Maeda, Y.; Wakahara, T.; Okamura, M.; Fujitsuka, M.; Ito, O.;
Kobayashi, K.; Nagase, S.; Kako, M.; Nakadaira, Y.; Horn, E. Org.
Lett. 1999, 1, 1509–1512. (e) Maeda, Y.; Takahashi, S.; Wakahara,
T.; Akasaka, T.; Sasaki, Y.; Fujitsuka, M.; Ito, O.; Kobayashi, K.;
Nagase, S.; Kako, M.; Nakadaira, Y. ITE Lett. 2000, 1, 408–411. (f)
Maeda, Y.; Sato, R.; Wakahara, T.; Okamura, M.; Akasaka, T.;
Fujitsuka, M.; Ito, O.; Kobayashi, K.; Nagase, S.; Kako, M.; Nakadaira,
Y.; Horn, E. J. Organomet. Chem. 2000, 611, 414–419.
9
12106 J. AM. CHEM. SOC. 2010, 132, 12106–12120
10.1021/ja1049719  2010 American Chemical Society

Photochemical Addition of C60 with Siliranes
A R T I C L E S
derivatives functionalized with carbon-containing or oxygen-
containing groups.3 Moreover, results show that the circular
motion of metal atoms inside the endohedral metallofullerenes
is controllable by exohedral functionalization through the
addition reactions of disiliranes7 and carbenes,8 the Bingel
reaction,9 and the Prato reaction.10 Such regulation of encap-
sulated atoms is expected to be valuable for application of
metallofullerenes as functional electronic and magnetic devices.
However, the substrates used for silylation of fullerenes have
been hitherto limited to silylenes,2 disiliranes,3,4 disilanes,5 and
silyl anions12 to produce monosilylated and multisilylated
derivatives. As a part of our continuing research into the
chemistry of fullerenes, we conducted photoreactions of C60 with
siliranes (silacyclopropanes), which are members of the most
fundamental cyclic orgnosilanes. It has been well documented
that siliranes are reactive toward various nucleophilic reagents
because of their strained, polar C-Si bonds in silirane rings.13
Recent studies have demonstrated that siliranes are useful and
versatile substrates for regioselective and stereoselective syn-
theses.14 If it is possible to derivatize fullerenes with activated
C-Si bonds of siliranes instead of disiliranes, then novel
carbosilylation reactions will be realized to fine-tune the
electronic properties of fullerene derivatives.
Herein, we report the photoreactions of C60 with siliranes
1a-d (Chart 1), describing the first example of carbosilylation
of C60 to afford several adducts of C60. In addition, we present
(8) (a) Suzuki, T.; Maruyama, Y.; Kato, T.; Akasaka, T.; Kobayashi, K.;
Nagase, S.; Yamamoto, K.; Funasaka, H.; Takahashi, T. J. Am. Chem.
Soc. 1995, 117, 9606–9607. (b) Maeda, Y.; et al. J. Am. Chem. Soc.
2004, 126, 6858–6859. (c) Iiduka, Y.; Wakahara, T.; Nakahodo, T.;
Tsuchiya, T.; Sakuraba, A.; Maeda, Y.; Akasaka, T.; Yoza, K.; Horn,
E.; Kato, T.; Liu, M. T. H.; Mizorogi, N.; Kobayashi, K.; Nagase, S.
J. Am. Chem. Soc. 2005, 127, 12500–12501. (d) Matsunaga, Y.;
Maeda, Y.; Wakahara, T.; Tsuchiya, T.; Ishitsuka, M. O.; Akasaka,
T.; Mizorogi, N.; Kobayashi, K.; Nagase, S.; Kadish, K. M. ITE Lett.
2006, 7, 43–49. (e) Iiduka, Y.; Wakahara, T.; Nakajima, K.; Nakahodo,
T.; Tsuchiya, T.; Maeda, Y.; Akasaka, T.; Yoza, K.; Liu, M. T. H.;
Mizorogi, N.; Nagase, S. Angew. Chem., Int. Ed. 2007, 46, 5562–
5564. (f) Akasaka, T.; Kono, T.; Matsunaga, Y.; Wakahara, T.;
Nakahodo, T.; Ishitsuka, M. O.; Maeda, Y.; Tsuchiya, T.; Kato, T.;
Liu, M. T. H.; Mizorogi, N.; Slanina, Z.; Nagase, S. J. Phys. Chem.
A 2008, 112, 1294–1297. (g) Tsuchiya, T.; et al. J. Am. Chem. Soc.
2008, 130, 450–451. (h) Lu, X.; Nikawa, H.; Tsuchiya, T.; Maeda,
Y.; Ishitsuka, M. O.; Akasaka, T.; Toki, M.; Sawa, H.; Slanina, Z.;
Mizorogi, N.; Nagase, S. Angew. Chem., Int. Ed. 2008, 47, 8642–
8645. (i) Cao, B.; Nikawa, H.; Nakahodo, T.; Tsuchiya, T.; Maeda,
Y.; Akasaka, T.; Sawa, H.; Slanina, Z.; Mizorogi, N.; Nagase, S. J. Am.
Chem. Soc. 2008, 130, 983–989. (j) Yamada, M.; Someya, C.;
Wakahara, T.; Tsuchiya, T.; Maeda, Y.; Akasaka, T.; Yoza, K.; Horn,
E.; Mizorogi, N.; Nagase, S. J. Am. Chem. Soc. 2008, 130, 1171–
1176. (k) Lu, X.; Nikawa, H.; Nakahodo, T.; Tsuchiya, T.; Ishitsuka,
M. O.; Maeda, Y.; Akasaka, T.; Toki, M.; Sawa, H.; Slanina, Z.;
Mizorogi, N.; Nagase, S. J. Am. Chem. Soc. 2008, 130, 9129–9136.
(l) Akasaka, T.; et al. J. Am. Chem. Soc. 2008, 130, 12840–12841.
(m) Takano, Y.; Aoyagi, M.; Yamada, M.; Nikawa, H.; Slanina, Z.;
Mizorogi, N.; Ishitsuka, M. O.; Tsuchiya, T.; Maeda, Y.; Akasaka,
T.; Kato, T.; Nagase, S. J. Am. Chem. Soc. 2009, 131, 9340–9346.
(n) Lu, X.; Nikawa, H.; Feng, L.; Tsuchiya, T.; Maeda, Y.; Akasaka,
T.; Mizorogi, N.; Slanina, Z.; Nagase, S. J. Am. Chem. Soc. 2009,
131, 12066–12067.
(4) (a) Akasaka, T.; Suzuki, T.; Maeda, Y.; Ara, M.; Wakahara, T.;
Kobayashi, K.; Nagase, S.; Kako, M.; Nakadaira, Y.; Fujitsuka, M.;
Ito, O. J. Org. Chem. 1999, 64, 566–569. (b) Fujitsuka, M.; Ito, O.;
Maeda, Y.; Kako, M.; Wakahara, T.; Akasaka, T. Phys. Chem. Chem.
Phys. 1999, 1, 3527–3531. (c) Wakahara, T.; Kondo, T.; Okamura,
M.; Akasaka, T.; Hamada, Y.; Suzuki, T.; Kako, M.; Nakadaira, Y.
J. Organomet. Chem. 2000, 611, 78–84. (d) Wakahara, T.; Rahman,
G. M. A.; Maeda, Y.; Kako, M.; Sato, S.; Okamura, M.; Akasaka, T.;
Kobayashi, K.; Nagase, S. ITE Lett. 2003, 4, 67–73. (e) Wakahara,
T.; Maeda, Y.; Kako, M.; Akasaka, T.; Kobayashi, K.; Nagase, S. J.
Organomet. Chem. 2003, 685, 177–188. (f) Maeda, Y.; Rahman,
G. M. A.; Wakahara, T.; Kako, M.; Okamura, M.; Sato, S.; Akasaka,
T.; Kobayashi, K.; Nagase, S. J. Org. Chem. 2003, 68, 6791–6794.
(5) (a) Sasaki, Y.; Konishi, T.; Fujitsuka, M.; Ito, O.; Maeda, Y.;
Wakahara, T.; Akasaka, T.; Kako, M.; Nakadaira, Y. J. Organomet.
Chem. 2000, 599, 216–220. (b) Sasaki, Y.; Fujitsuka, M.; Ito, O.;
Maeda, Y.; Wakahara, T.; Akasaka, T.; Kobayashi, K.; Nagase, S.;
Kako, M.; Nakadaira, Y. Heterocycles 2001, 54, 777–787.
(9) (a) Feng, L.; Nakahodo, T.; Wakahara, T.; Tsuchiya, T.; Maeda, Y.;
Akasaka, T.; Kato, T.; Horn, E.; Yoza, K.; Mizorogi, N.; Nagase, S.
J. Am. Chem. Soc. 2005, 127, 17136–17137. (b) Feng, L.; Wakahara,
T.; Nakahodo, T.; Tsuchiya, T.; Piao, Q.; Maeda, Y.; Lian, Y.;
Akasaka, T.; Horn, E.; Yoza, K.; Kato, T.; Mizorogi, N.; Nagase, S.
Chem.sEur. J. 2006, 12, 5578–5586. (c) Feng, L.; Tsuchiya, T.;
Wakahara, T.; Nakahodo, T.; Piao, Q.; Maeda, Y.; Akasaka, T.; Kato,
T.; Yoza, K.; Horn, E.; Mizorogi, N.; Nagase, S. J. Am. Chem. Soc.
2006, 128, 5990–5991.
(6) (a) Han, A.; Wakahara, T.; Maeda, Y.; Niino, Y.; Akasaka, T.;
Yamamoto, K.; Kako, M.; Nakadaira, Y.; Kobayashi, K.; Nagase, S.
Chem. Lett. 2001, 974–975. (b) Wakahara, T.; Han, A.; Maeda, Y.;
Niino, Y.; Akasaka, T.; Yamamoto, K.; Kako, M.; Nakadaira, Y.;
Kobayashi, K.; Nagase, S. ITE Lett. 2001, 2, 649–653. (c) Wakahara,
T.; Han, A.; Niino, Y.; Maeda, Y.; Akasaka, T.; Suzuki, T.; Yamamoto,
K.; Kako, M.; Nakadaira, Y.; Kobayashi, K.; Nagase, S. J. Mater.
Chem. 2002, 12, 2061–2064.
(10) (a) Cao, B.; Wakahara, T.; Maeda, Y.; Han, A.; Akasaka, T.; Kato,
T.; Kobayashi, K.; Nagase, S. Chem.sEur. J. 2004, 10, 716–720. (b)
Yamada, M.; Wakahara, T.; Nakahodo, T.; Tsuchiya, T.; Maeda, Y.;
Akasaka, T.; Yoza, K.; Horn, E.; Mizorogi, N.; Nagase, S. J. Am.
Chem. Soc. 2006, 128, 1402–1403. (c) Yamada, M.; Okamura, M.;
Sato, S.; Someya, C. I.; Mizorogi, N.; Tsuchiya, T.; Akasaka, T.; Kato,
T.; Nagase, S. Chem.sEur. J. 2009, 15, 10533–10542.
(7) (a) Akasaka, T.; Kato, T.; Kobayashi, K.; Nagase, S.; Yamamoto, K.;
Funasaka, H.; Takahashi, T. Nature 1995, 374, 600–601. (b) Akasaka,
T.; Nagase, S.; Kobayashi, T.; Suzuki, T.; Kato, K.; Yamamoto, H.;
Funasaka, T.; Takahashi, T. J. Chem. Soc., Chem. Commun. 1995,
1343–1344. (c) Akasaka, T.; Nagase, S.; Kobayashi, K.; Suzuki, T.;
Kato, T.; Kikuchi, K.; Achiba, Y.; Yamamoto, K.; Funasaka, H.;
Takahashi, T. Angew. Chem., Int. Ed. Engl. 1995, 34, 2139–2141. (d)
Wakahara, T.; Matsunaga, Y.; Katayama, A.; Maeda, Y.; Kako, M.;
Akasaka, T.; Okamura, M.; Kato, T.; Choe, Y.-K.; Kobayashi, K.;
Nagase, S.; Huang, H.; Ata, M. Chem. Commun. 2003, 2940–2941.
(e) Yamada, M.; Feng, L.; Wakahara, T.; Tsuchiya, T.; Maeda, Y.;
Lian, Y.; Kako, M.; Akasaka, T.; Kato, T.; Kobayashi, K.; Nagase,
S. J. Phys. Chem. B 2005, 109, 6049–6051. (f) Maeda, Y.; Miyashita,
J.; Hasegawa, T.; Wakahara, T.; Tsuchiya, T.; Feng, L.; Lian, Y.;
Akasaka, T.; Kobayashi, K.; Nagase, S.; Kako, M.; Yamamoto, K.;
Kadish, K. M. J. Am. Chem. Soc. 2005, 127, 2143–2146. (g) Wakahara,
T.; Iiduka, Y.; Ikenaga, O.; Nakahodo, T.; Sakuraba, A.; Tsuchiya,
T.; Maeda, Y.; Kako, M.; Akasaka, T.; Yoza, K.; Horn, E.; Mizorogi,
N.; Nagase, S. J. Am. Chem. Soc. 2006, 128, 9919–9925. (h) Yamada,
M.; Nakahodo, T.; Wakahara, T.; Tsuchiya, T.; Maeda, Y.; Akasaka,
T.; Kako, M.; Yoza, K.; Horn, E.; Mizorogi, N.; Kobayashi, K.;
Nagase, S. J. Am. Chem. Soc. 2005, 127, 14570–14571. (i) Wakahara,
T.; Yamada, M.; Takahashi, S.; Nakahodo, T.; Tsuchiya, T.; Maeda,
Y.; Akasaka, T.; Kako, M.; Yoza, K.; Horn, E.; Mizorogi, N.; Nagase,
S. Chem. Commun. 2007, 2680–2682. (j) Yamada, M.; Wakahara, T.;
Tsuchiya, T.; Maeda, Y.; Kako, M.; Akasaka, T.; Yoza, K.; Horn, E.;
Mizorogi, N.; Nagase, S. Chem. Commun. 2008, 558–560.
(11) (a) Maeda, Y.; Miyashita, J.; Hasegawa, T.; Wakahara, T.; Tsuchiya,
T.; Nakahodo, T.; Akasaka, T.; Mizorogi, N.; Kobayashi, K.; Nagase,
S.; Kato, T.; Ban, N.; Nakajima, H.; Watanabe, Y. J. Am. Chem. Soc.
2005, 127, 12190–12191. (b) Takano, Y.; Yomogida, A.; Nikawa, H.;
Yamada, M.; Wakahara, T.; Tsuchiya, T.; Ishitsuka, M. O.; Maeda,
Y.; Akasaka, T.; Kato, T.; Slanina, Z.; Mizorogi, N.; Nagase, S. J. Am.
Chem. Soc. 2008, 130, 16224–16230. (c) Nikawa, H.; Yamada, T.;
Cao, B.; Mizorogi, N.; Slanina, Z.; Tsuchiya, T.; Akasaka, T.; Yoza,
K.; Nagase, S. J. Am. Chem. Soc. 2009, 131, 10950–10954. (d) Maeda,
Y.; Sato, S.; Inada, K.; Nikawa, H.; Yamada, M.; Mizorogi, N.;
Hasegawa, T.; Tsuchiya, T.; Akasaka, T.; Kato, T.; Slanina, Z.; Nagase,
S. Chem.sEur. J. 2010, 16, 2193–2197. (e) Lu, X.; Nikawa, H.;
Tsuchiya, T.; Akasaka, T.; Toki, M.; Sawa, H.; Mizorogi, N.; Nagase,
S. Angew. Chem., Int. Ed. 2010, 49, 594–597.
(12) (a) Kusukawa, T.; Ando, W. Angew. Chem., Int. Ed. Engl. 1996, 35,
1315–1317. (b) Kusukawa, T.; Ando, W. J. Organomet. Chem. 1998,
561, 109–120.
(13) (a) Seyferth, D.; Duncan, P.; Vick, S. C. J. Organomet. Chem. 1977,
125, C5–C10. (b) Seyferth, D.; Duncan, P.; Shannon, M. L. Orga-
nometallics 1984, 3, 579–583. (c) Tortorelli, V. J.; Jones, M., Jr.; Wu,
S.-H.; Li, Z.-H. Organometallics 1983, 2, 759–764.
9
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A R T I C L E S
Nagatsuka et al.
Chart 1
Table 1. Oxidation Potentials (Eox)a of Siliranes
compound
1a
1b
1c
1d
6
Eox (V)
0.22
0.47
0.84
1.17
0.24
a Versus ferrocene/ferrocenium couple.
Chart 2. Possible Structures for 1,2-Adducts of C60 with Bridging
Group X
has been provided.16 In this report, we present the first full
characterization of the silylated C60 of the type C, as well as
the derivatives of other addition types.
Results and Discussion
Photoreactions of C60 and Siliranes. Siliranes 1a-d were
synthesized using reactions of organic silylenes (Dmt2Si: and
Dep2Si:)17 with ethylene and substituted olefins. The oxidation
potentials (Eox) of 1a-d are presented in Table 1, which shows
that 1a and 1b have fairly low Eox values comparable with that
of disilirane 6, whereas those of 1c and 1d are somewhat higher.
Because 1a and 1b contain benzylsilane structures in their
molecules, such low Eox values are reasonable because of the
possible σ-π interaction between the ring Si-C bonds and the
aryl groups attached to the ring carbon atoms. Therefore, 1a
and 1b are expected to react readily with C60, a weak electron
acceptor, because it has been suggested that donor-acceptor
interaction plays an important role in the photoreaction of C60
and 6.3
Photoreactions of C60 with siliranes were conducted as
follows. A toluene solution of 1a and C60 was irradiated for
3 h with two 500-W tungsten-halogen lamps using an aqueous
sodium nitrite filter solution (cutoff <400 nm) under an Ar
atmosphere. After consumption of 1a, careful separation of the
reaction mixture using HPLC afforded two products, 2a and
5a, as shown in Scheme 2. In a similar procedure, the reaction
of C60 and 1b produced four adducts: 2b, 3b, 4b, and 5b. On
the other hand, the photoreactions of 1c and 1d proceeded quite
slowly, as anticipated. Irradiation of C60 with 1c and 1d for
60 h resulted in the formation of 2c and 2d, respectively, in
lower yields, although substantial amounts of 1c and 1d were
recovered. The structures of these products were determined
using NMR, UV spectroscopy, mass spectrometry, and single-
crystal X-ray structural analyses (Vide infra). To the best of our
knowledge, these results constitute the first example of carbosi-
lylation of fullerenes.
a detailed characterization of the silylated products using NMR,
UV spectroscopy, mass spectrometry, cyclic voltammetry,
differential pulse voltammetry, and single-crystal X-ray struc-
tural analyses along with theoretical calculations. Of particular
interest is the isolation of a closed type of 1,2-adduct at the
5,6-ring junction in these reactions. There are four possible
isomeric structures A-D for derivatized C60 resulting from 1,2-
addition of various reagents, as shown in Chart 2. However,
almost all reported 1,2-adducts are categorized into types A and
B. Recent theoretical investigations have postulated that the
production of types C and D is unfavorable because of the
formation of destabilizing double bonds in five-membered
rings.15 To our knowledge, only one example of the formation
of a type C isomer has been reported, that by Kabe et al.
Nevertheless, no structural analysis using X-ray crystallography
(15) (a) Prato, M.; Li, Q. C.; Wudl, F.; Lucchini, V. J. Am. Chem. Soc.
1993, 115, 1148–1150. (b) Prato, M.; Lucchini, V.; Maggini, M.;
Stimpfl, E.; Scorrano, G.; Elermann, M.; Suzuki, T.; Wudl, F. J. Am.
Chem. Soc. 1993, 115, 8479–8580. (c) Raghavachari, K. Chem. Phys.
Lett. 1992, 195, 221–224. (d) Raghavachari, K.; Sosa, C. Chem. Phys.
Lett. 1993, 209, 223–228. (e) Haddon, R. C.; Raghavachari, K.
Tetrahedron 1996, 52, 5207–5220. (f) Diederich, F.; Isaacs, L.; Philp,
D. J. Chem. Soc., Perkin Trans. 2 1994, 391–394. (g) Wallenborn,
E.-U.; Haldimann, R. F.; Kla¨rner, F.-G.; Diederich, F. Chem.sEur.
J. 1998, 4, 2258–2265. (h) Shen, C. K.-F.; Yu, H.-H.; Juo, C.-G.;
Chien, K.-M.; Her, G.-R.; Luh, T.-Y. Chem.sEur. J. 1997, 3, 744–
748.
(14) (a) Franz, A. K.; Woerpel, K. A. Acc. Chem. Res. 2000, 33, 813–820.
(b) Clark, T. B.; Woerpel, K. A. J. Am. Chem. Soc. 2004, 126, 9522–
9523. (c) Calad, S. A.; Woerpel, K. A. J. Am. Chem. Soc. 2005, 127,
2046–2047.
(16) Kabe, Y.; Ohgaki, H.; Yamagaki, T.; Nakanishi, H.; Ando, W. J.
Organomet. Chem. 2001, 636, 82–90.
(17) “Dmt” and “Dep” are used hereafter as abbreviations of, respectively,
4-tert-butyl-2,6-dimethylphenyl and 2,6-diethylphenyl groups.
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Photochemical Addition of C60 with Siliranes
A R T I C L E S
Scheme 2
Figure 1. Absorption spectra of 2a and 5a.
Thermal and photochemical transformation of the silylated
products was examined to clarify their relative stabilities. Upon
heating toluene solutions of 2b-5b independently at 100 °C in
the dark, 3b afforded 2b, and 4b gave a mixture of 2b and 3b,
respectively, although the conversion of 2b and 5b did not take
place at all. Meanwhile, irradiation of 2b-5b under the same
conditions employed for 1b at room temperature caused the
rearrangement of 4b to 3b, although 2b, 3b, and 5b were
recovered quantitatively. These results indicate that the stabilities
of 2b, 3b, and 4b decrease in the order 2b > 3b > 4b and that
the conversion of 4b to 3b is likely to occur in part during the
photolysis of 1b. In contrast to 1b, 1a produced no product
other than 2a and 5a. When the photoreaction of C60 and 1a in
toluene-d8 at -30 °C was monitored using 1H NMR, no
additional signal suggesting the formation of intermediates was
observed.
Structural Determination of 2a and 5a. The MALDI-TOF
mass spectrometry of 5a displays peaks for m/z 1250 (M-),
720(C60-), and 529(M--C60H) as expected for a 1:1 adduct of
C60 and 1a, whereas that of 2a gives no peak for M-. In the
UV-vis absorption spectra of 2a and 5a, characteristic absorp-
tion maxima are observed, respectively, at 443 nm for 2a, and
at 446 nm for 5a (Figure 1). Because such absorption bands
are known to be specific to C60 derivatives resulting from 1,2-
addition at a 6,6-ring junction,18 similar structures of derivatized
C60 cage are suggested for 2a and 5a. Additional structural
information was obtained by 1H NMR and 13C NMR spectros-
copy as follows.
Figure 2. (a) 13C NMR spectrum of 2a. (b) HMBC spectrum of 2a.
Dmt groups, as well as those of phenyl protons. Two doublets
for the two methylene protons are also observed to suggest an
unsymmetrical structure of 2a. In the 13C NMR spectrum of
The 1H NMR spectrum of 2a displays four methyl, two tert-
butyl, and four aryl proton signals of the two nonequivalent
9
J. AM. CHEM. SOC. VOL. 132, NO. 34, 2010 12109

A R T I C L E S
Nagatsuka et al.
Figure 3. (a) 13C NMR spectrum of 5a. (b) HMQC spectra of 5a. (c) HMBC spectrum of 5a.
2a, 58 signals for the sp2 carbons of C60 skeleton were observed
along with 10 tertiary and 12 quaternary sp2 carbon signals from
the two nonequivalent Dmt and the two nonequivalent phenyl
groups (Figures 2a). This result also suggests that free rotation
of the bulky Dmt rings may be restricted because of the steric
hindrance in 2a. In addition, signals for two sp3 carbons of the
C60 cage, one methylene carbon and one quaternary carbon of
the silacyclopentane ring of 2a, and four methyl and two tert-
butyl carbons of Dmt groups were observed in the upfield
spectral area. Moreover, the HMBC spectrum displays cross
peaks corresponding to the correlation of the methylene protons
and the sp3 carbons of C60 cage and the quaternary carbon of
the silacyclopentane ring in 2a (Figure 2b). These spectral data
are consistent with C1 symmetry of 2a resulting from 1,2-
addition of 1a at the 6,6-ring junction of C60, with the
silacyclopentane ring held in an envelope conformation.
Regarding the 1H NMR and 13C NMR spectra of 5a, numbers
and multiplicities of the signals for the C60 cage, the Dmt, and
the phenyl groups closely resemble those of 2a, except that one
of sp3 carbon (δ 61.31) of the C60 cage is tertiary to have a
C60-H bond (Figures 3a). In addition, two singlet proton signals
are found at δ 8.76 and 7.69, which are assignable, respectively,
to the alkenyl proton and the methyne proton on the C60 cage
of 5a. The HMQC spectrum of 5a indicates that these proton
signals at δ 8.76 and 7.69 correlate with a signal of the alkenyl
carbon at δ 125.66 and that of sp3 carbon of the C60 cage at δ
9
12110 J. AM. CHEM. SOC. VOL. 132, NO. 34, 2010

Photochemical Addition of C60 with Siliranes
A R T I C L E S
carbons of the two nonequivalent Dep and the 4-tert-butylphenyl
groups (Figure 5a). As described for 2a, the degenerated spectral
symmetry of Dep groups may be explained based on restriction
of the free rotation of bulky Dep rings in 2b. Also observed
are signals corresponding to two sp3 carbons of the C60 cage,
one methylene and one methyne of the silacyclopentane ring
of 2b, four ethyl groups, and one tert-butyl group. Additional
analyses using HMQC and HMBC support the spectral assign-
ment of the silacyclopentane ring protons of 2b at δ 5.31, 3.94,
and 2.55. Consequently, the methylene carbon signal at δ 29.01
show two cross peaks with the proton signals at δ 3.94 and
2.55, whereas the methyne carbon at δ 58.65 correlates with a
proton signal at δ 5.31 in the HMQC spectrum (Figure 5b).
Moreover, in the HMBC spectrum of 2b, cross peaks are
observed between the sp3 carbon signals of the C60 cage at δ
80.07, 74.84, and the silacyclopentane ring proton signals
(Figure 5c). Therefore, it is concluded that 2b has C1 symmetry
with a silacyclopentane structure at a 6,6-ring junction of C60.
1
In the H NMR and 13C NMR spectra of 3b, numbers and
multiplicities of proton and carbon signals for the C60 cage, the
Dep, and the 4-tert-butylphenyl groups closely resemble those
of 2b (Figure 6a). The presence of a silacyclopentane structure
is also suggested by the HMQC and the HMBC spectra (Figures
6b,c). These observations indicate that the structure of 3b
resembles that of 2b well. However, 3b was determined to be
a closed 1,2-adduct at a 5,6-ring junction of C60 using single-
crystal X-ray structural analysis as described below.
1
The NMR analyses of 4b and 5b were limited to H NMR
because of the low yields of these compounds. Although the
structure of 4b was determined to be a 1,4-adduct by single-
crystal X-ray analysis, that of 5b has not been obtained yet.
Comparisons of H NMR, UV-vis spectra, and MALDI-TOF
MS of 5a and 5b present the possibility that the structure of 5b
resembles that of 5a.
Figure 4. (a) Absorption spectra of 2b, 3b, 4b, and 5b. (b) vis-NIR spectra
of 2b and 3b.
1
61.31, respectively (Figure 3b). Meanwhile, the proton signal
at δ 7.69 shows a cross peak with another sp3 carbon (δ 66.92)
of the C60 cage in the HMBC spectrum (Figure 3c). These
observations support the proposed structure of 5a as a hydrosi-
lylated C60 derivative.
Structural Determination of 2c. It can be verified that 2c and
2d are the 1:1 adducts because the corresponding molecular
ion peaks m/z 1154 for 2c and m/z 1098 for 2d are observed
together with 720 (C60-) in the MALDI-TOF mass spectra. The
characteristic absorption bands for 1,2-adducts at the 6,6-ring
junction are also confirmed at 443 nm for 2c and 442 nm for
2d in UV-vis spectra. Because 2c displays four methyl, three
tert-butyl, and four aryl proton signals in the 1H NMR spectrum,
the inhibited free rotation of two nonequivalent Dmt groups is
suggested. An ABX coupling is also verified for the silacyclo-
pentane ring protons of 2c using HMQC spectroscopy. In the
13C NMR spectrum of 2c, 70 sp2 carbon signals are assigned to
58 carbons of C60 skeleton and four tertiary and eight quaternary
aromatic carbons of the two nonequivalent Dmt groups. Ad-
ditional 14 sp3 carbon signals are found in the upfield region
for the four methyl and the three tert-butyl groups and the four
silacyclopentane ring carbons of 2c. Therefore, it is concluded
that 2c is a 1,2-adduct at the 6,6-ring junction as with 2a and
Structural Determination of 2b, 3b, 4b, and 5b. In the
MALDI-TOF mass spectrometry, 2b, 3b, 4b, and 5b each
display peaks for m/z 1174 (M-), 720(C60-) as expected for
1:1 adducts of C60 and 1b. The UV-vis absorption spectra of
2b and 5b show absorption maxima at 442 nm for 2b and 444
nm for 5b (Figure 4a,b). Probably, 2b and 5b should be
derivatives resulting from 1,2-addition at a 6,6-ring junction of
C60 as proposed for 2a and 5a. In a similar manner, it is
suggested that 4b formed by 1,4-addition to the six-membered
ring of C60 judged by its characteristic absorption maxima at
443, 467, and 552 nm.19 On the other hand, no specific
absorption band is observed for 3b, which would yield a clue
to the structure, although 3b has an absorption band extending
to a longer wavelength than those of 2b, 4b, and 5b.
1
2b. The low temperature H NMR measurement of 2d at 223
1
The H NMR of 2b displays proton signals for four ethyl
K provided four methyl, two tert-butyl, and four aryl proton
signals as well as three signals assignable to the silacyclopentane
ring protons. By comparison of the spectral data with those of
2a-2c, 2d is assumed to be a 1,2-adduct at 6,6-ring junction of
C60 without free rotation of the Dmt groups and with an envelope
conformation of the silacyclopentane ring. Furthermore, coa-
lescence of these signals reflecting conformational change of
2d was observed at 295 K, yielding an activation energy ∆Gq
) 15.4 kcal/mol. The fact that 2d afforded one methyl, one
tert-butyl, one aryl proton, and two methylene signals in the
groups and one tert-butyl group, along with aromatic proton
signals of Dep and 4-tert-butylphenyl groups. The ring protons
of the silacyclopentane addend of 2b are confirmed to constitute
an ABX spin system. Meanwhile, the 13C NMR spectrum of
2b shows 58 quaternary signals for the C60 skeleton together
with 16 signals of eight tertiary and eight quaternary aromatic
(18) Hirsch, A.; Gro¨sser, T.; Skiebe, A.; Soi, A. Chem. Ber. 1993, 126,
1061–1067.
(19) Akasaka, T.; et al. Org. Lett. 2000, 2, 2671–2674.
9
J. AM. CHEM. SOC. VOL. 132, NO. 34, 2010 12111

A R T I C L E S
Nagatsuka et al.
Figure 5. (a) 13C NMR spectrum of 2b. (b) HMQC spectrum of 2b. (c) HMBC spectrum of 2b.
1H NMR measurement at 383 K confirmed the proposed
structure of 2d.
the C60 cage and are in agreement with the fact that 3b and 4b
are less stable than 2b, which has no such shortened C-C bonds
in the pentagon rings.
Crystal Structures of 2b, 3b, 4b, and 5a. The structures of
2b, 3b, 4b, and 5a were confirmed using single-crystal X-ray
analyses. The structure of 3b was established unambiguously
to be a closed 1,2-adduct at a 5,6-ring junction of C60. ORTEP
drawings of 2b, 3b, 4b, and 5a are shown in Figures 7a-d and
8a-d, with selected bond lengths in Table 2. Also described
are the corresponding calculated bond lengths of the optimized
structures obtained by the B3LYP/3-21G** method. On the basis
of the structural data, the following features should be pointed
out: (i) The Si-C bonds between the C60 and the silirane
addends in 2b, 3b, 4b, and 5a are markedly elongated compared
with those found in normal Si-C single bonds of organosilanes.
This elongation may be attributed to the steric repulsion between
the C60 cage and the bulky substituents on the Si atoms and
also to the ꢀ-effect resulting from σ-π conjugation between
the Si-C σ-orbital and the π-orbital of the C60 cage. (ii) The
C-C bond lengths between two sp3 carbon atoms of the C60
cage of 2b and 3b are much longer than those of normal C-C
single bonds. (iii) The C-C bond lengths between one sp3
carbon atom and one sp2 carbon atom of the C60 cage of 2b,
3b, 4b, and 5a are almost within normal values for C-C single
bonds as shown in Table 2. (iv) The geometries of sp3 carbon
atoms of the C60 cage of 2b, 3b, 4b, and 5a are roughly
tetrahedral, as verified by the bond angles around those atoms.
(v) The double bond characters of C5-C6, C7-C8 of 3b and
C8-C9 of 4b are apparently enhanced because these bonds are
shortened substantially compared to the other C-C bond lengths
of the pentagon rings of the C60 cages. These results suggest
that 3b and 4b contain double bonds in the pentagon rings of
Reaction Mechanism. It is apparent that C60 is selectively
excited in these photoreactions because 1a-d have no absorp-
tion band greater than 400 nm and are inert to irradiation. The
photoreactions of C60 and 1a-d were suppressed by addition
of 1,4-diazabicyclo[2.2.2]octane (DABCO) or 1,2,4,5-tet-
ramethoxybenzene (TMB), each of which quenches the excited
triplet state of C60 (3C60*). Meanwhile, the free energy changes
3
(∆G) of the electron-transfer process from 1a and 1b to C60*
in toluene are 7.6 and 13.4 kcal/mol, respectively, according to
the Rehm-Weller equation.20 Previously, we reported that the
photoaddition of C60 with disilirane 6 proceeds probably through
an exciplex resulted from 3C60* with 6 in nonpolar solvents.3 It
3
was also observed that C60* was quenched efficiently by
addition of 6 in the laser flash photolysis.3d-f On the basis of
these results, a similar reaction mechanism is plausible for 1a-d,
as presented in Scheme 3, where 3C60* operates as a key reactive
3
species. Addition of C60* and silirane produces a diradical
intermediate 7. Subsequent ring closure of 7 affords the cyclized
adducts 2a, 2b, 3b, and 4b, whereas intramolecular hydrogen
transfer leads to 5a and 5b.
Electronic Properties of 2a, 2b, 3b, 4b, 5a, and 5b. The redox
potentials of the silylated products 2a, 2b, 3b, 4b, 5a, and 5b
were measured using cyclic voltammetry (CV) and differential
pulse voltammetry (DPV) and are listed with those of related
compounds in Table 3. The corresponding voltammograms are
also presented in Figure 9. The oxidation waves in the CV are
(20) Rehm, D.; Weller, A. Isr. J. Chem. 1970, 8, 259–271.
9
12112 J. AM. CHEM. SOC. VOL. 132, NO. 34, 2010

Photochemical Addition of C60 with Siliranes
A R T I C L E S
all irreversible, probably because of desilylation during the CV
measurements, as observed previously for 8 (Chart 3).3b We
have reported that the silylated C60 show lower oxidation and
reduction potentials than those of C60 itself and the derivatives
with alkyl and alkoxyl substituents.3b In fact, the first oxidation
potentials (Eox1) of 2a, 2b, 3b, 4b, 5a, and 5b are shifted
cathodically from 130 mV to 530 mV compared to that of C60.
Results also show that the Eox1 values of 2a and 2b (1,2-adducts
at 6,6-ring junction) and 4b (1,4-adduct) are somewhat higher
than those of the corresponding bis-silylated compounds 8 (1,2-
adduct) and 10 (1,4-adduct), respectively. On the other hand,
the reduction potentials (Ered) of 2a, 2b, and 4b resemble those
of 8 and 10 overall. These results indicate that the carbosily-
lation, compared to the bis-silylation, has medium effects on
tuning the electron-donor properties of fullerenes, although their
effects on tuning the acceptor properties are similar. Particularly
noteworthy is the low Eox1 and the high Ered1 values of 3b: the
former is comparable with those of 8 and 10, whereas the latter
resembles that of C60. As reported for the 8, 10, and 11, it is
also confirmed that the redox properties of the carbosilylated
fullerenes depend on both the electronic effects of their
substituents and the regiochemistry of the functionality. The
1,2-addition at 5,6-rung junction might exert some specific
effects on tuning the redox properties of C60; it is complementary
to the 1,2-addition at 6,6-ring junction and the 1,4-addition.
Further investigation of the redox properties was conducted
based on theoretical calculations as described below.
Theoretical Calculations. To obtain insight into the structures
and the electronic properties of the silylated products, theoretical
calculations were conducted for 2b, 3b, and 4b. The geometries
of the compounds were optimized at the AM1 and the B3LYP/
3-21G** levels.21 Subsequently, single point energies were
calculated at the B3LYP/6-31G**//B3LYP/3-21G** level.
Figure 10 portrays the optimized structures of 2b, 3b, and 4b
with selected bond lengths included in Table 2 for comparison
with the corresponding X-ray crystal structures. Checking of
these structural parameters confirmed that the calculations
reproduce the X-ray structures of the silacyclic vicinities of 2b,
3b, and 4b. The relative energies and the HOMO, LUMO
energies of 2b, 3b, and 4b are also listed in Table 4. The relative
energies at B3LYP/6-31G**//B3LYP/3-21G** level show that
2b is 15.5 and 22.8 kcal/mol more stable than 3b and 4b,
respectively, in agreement with the experimental results of the
thermal transformation from 4b to 2b. It is particularly interest-
ing that the energy level for HOMO (EHOMO) is raised while
that of LUMO (ELUMO) is lowered in 3b compared to the
corresponding levels of 2b and 4b, respectively. This result is
consistent with the cathodic shifts of Eox and Ered of 3b in
1
1
comparison with those of 2a, 2b, and 4b.
Conclusions
For this study, C60 was derivatized by the photochemical
addition of siliranes 1a-d to afford novel carbosilylated
compounds, which were characterized using MS, NMR spec-
troscopy, X-ray crystallography, and electrochemical analyses.
Single-crystal X-ray structural analysis of 3b unambiguously
disclosed the structure of a closed 1,2-adduct at 5,6-ring junction
of C60, hitherto unknown in the structural determination of
fullerene derivatives. Results also show that carbosilylation is
(21) (a) Becke, A. D. Phys. ReV. A 1988, 38, 3098–3100. (b) Becke, A. D.
J. Chem. Phys. 1993, 98, 5648–5652. (c) Lee, C.; Yang, W.; Parr,
R. G. Phys. ReV. B 1988, 37, 785–789. (d) Frisch, M. J.; et al.
GAUSSIAN 03, reV. C.01; Gaussian Inc.: Wallingford, CT, 2004.
Figure 6. (a) 13C NMR spectrum of 3b. (b) HMQC spectrum of 3b. (c)
HMBC spectrum of 3b.
9
J. AM. CHEM. SOC. VOL. 132, NO. 34, 2010 12113

A R T I C L E S
Nagatsuka et al.
Figure 7. ORTEP drawings of (a) 2b, (b) 3b, (c) 4b, and (d) 5a with thermal ellipsoids shown at the 30% probability level.
effective for fine-tuning of the redox properties of fullerenes,
and complementary to the bis-silylation. Furthermore, it is
noteworthy that the redox properties of derivatized fullerenes
are controlled not merely by the electronic effect of additives
but also by the regiochemistry of addition reactions. These
results will broaden the scope of derivatization of fullerenes
9
12114 J. AM. CHEM. SOC. VOL. 132, NO. 34, 2010

Photochemical Addition of C60 with Siliranes
A R T I C L E S
Figure 8. Partial views of (a) 2b, (b) 3b, (c) 4b, and (d) 5a in the vicinities of addends.
by HPLC using a 5PBB column (i.d. 20 mm × 250 mm) and a
Buckey Prep M column (i.d. 20 mm × 250 mm) obtained from
Nacalai Tesque inc.
and endohedral metallofullerenes using organosilanes and
engender new application of silylated fullerenes for functional
materials.
Data for 2a: dark brown solid; 1H NMR (500 MHz, C6D6, 293
K) δ 7.15 (s, 1H), 7.11 (s, 1H), 6.78 (s, 1H), 6.74 (s, 1H), 7.16-6.71
(m, 10H), 4.80 (d, 1H, J ) 14 Hz), 3.42 (d, 1H, J ) 14 Hz), 3.21
(s, 3H), 3.02 (s, 3H), 2.55 (s, 3H), 2.45 (s, 3H), 1.22 (s, 9H), 1.11
(s, 9H); 13C NMR (500 MHz, C6D6, 293 K) δ 162.74 (s, 1C), 162.24
(s, 1C), 159.65 (s, 1C), 155.48 (s, 1C), 153.67 (s, 1C), 151.43 (s,
1C), 149.62 (s, 1C), 148.16 (s, 1C), 148.02 (s, 1C), 147.68 (s, 1C),
147.53 (s, 1C), 147.36 (s, 1C), 147.29 (s, 1C), 147.19 (s, 3C),
147.13 (s, 1C), 146.95 (s, 1C), 146.91 (s, 3C), 146.74 (s, 1C),
146.69 (s, 1C), 146.45 (s, 1C), 146.37 (s, 1C), 146.36 (s, 1C),
146.29 (s, 1C), 146.20 (s, 1C), 146.01 (s, 1C), 145.76 (s, 1C),
145.65 (s, 1C), 145.18 (s, 2C), 145.03 (s, 2C), 144.97 (s, 1C),
144.72 (s, 1C), 144.61 (s, 2C), 143.99 (s, 1C), 143.80 (s, 2C),
143.68 (s, 1C), 143.64 (s, 1C), 143.40 (s, 2C), 143.22 (s, 2C),
142.99 (s, 1C), 142.91 (s, 1C), 142.84 (s, 1C), 142.54 (s, 1C),
142.51 (s, 2C), 142.31 (s, 1C), 141.82 (s, 1C), 141.57 (s, 1C),
141.48 (s, 1C), 140.56 (s, 1C), 140.31 (s, 1C), 140.20 (s, 1C),
139.13 (s, 1C), 138.99 (s, 1C), 136.52 (s, 1C), 135.12 (s, 1C),
134.57 (s, 1C), 134.06 (s, 1C), 130.76 (s, 1C), 127.25 (d, 1C),
127.15 (d, 1C), 126.41 (d, 1C), 126.27 (d, 1C), 83.05 (s, 1C; C60C),
72.53 (s, 1C; CPh2), 65.76 (s, 1C; C60Si), 34.87 (s, 1C; C(CH3)3),
34.69 (s, 1C; C(CH3)3), 31.70 (4C), 31.58 (q, 3C; C(CH3)3), 30.71
(q, 1C; CH3), 28.31 (q, 1C; CH3), 27.29 (q, 1C; CH3), 24.99 (q,
1C; CH3); vis-NIR (toluene) λmax 443, 316 nm; MALDI-TOF MS
m/z 720 (C60-).
Experimental Section
General. All chemicals and solvents were obtained from Wako
Pure Chemical Industries, Ltd. and Aldrich Chemical Co. Inc.
and were used without further purification, unless otherwise
stated. Toluene was distilled over benzophenone sodium ketyl
under an argon atmosphere before its use in reaction. 1,2-D
ichlorobenzene (ODCB) was distilled over P2O5 under vacuum
before its use. High-performance liquid chromatography (HPLC)
isolation was performed on LC-908 and LC-918 chromatographs
(Japan Analytical Industry Co., Ltd.) that were monitored by
UV absorption at 330 nm. Toluene was used as the eluent. Mass
spectrometry was performed on a Bruker BIFLEX III instrument
(Bruker Analytik) with 1,1,4,4-tetraphenyl-1,3-butadiene as the
matrix. Absorption spectra were measured by using a SHI-
MADZU UV-3150 spectrophotometer (Shimadzu Corp.). The
1H and 13C NMR measurements were conducted on Bruker
AVANCE 300 and 500 spectrometers with a CryoProbe system
(Bruker Analytik). Cyclic voltammograms (CVs) and differential
pulse voltammograms (DPVs) were recorded on a BAS CV50W
electrochemical analyzer (BAS Inc.). Platinum wires were used
as the working and counter electrodes. The reference electrode
was a saturated calomel reference electrode (SCE) filled with
0.1 M (n-Bu)4NPF6 (TBAPF6) in ODCB. The CVs were recorded
using a scan rate of 20 mV/s. The DPVs were obtained using a
pulse amplitude of 50 mV, a pulse width of 50 ms, a pulse period
of 200 ms, and a scan rate of 20 mV/s.
1
Data for 5a: dark brown solid; H NMR (500 MHz, C6D6) δ
8.76 (s, 1H), 7.80 (d, 2H, J ) 8 Hz), 7.69 (s, 1H), 7.28 (d, 2H, J
) 7 Hz), 7.16-6.93 (m, 6H), 7.07 (s, 1H), 7.01 (s, 1H), 6.73 (s,
1H), 6.70 (s, 1H), 3.45 (s, 3H), 3.01 (s, 3H), 2.36 (s, 3H), 2.06 (s,
3H), 1.36 (s, 9H), 1.04(s, 9H); 13C NMR (500 MHz, C6D6) δ 162.33
(d, 1C; CH), 159.37 (s, 1C), 157.89 (s, 1C), 157.33 (s, 1C), 156.13
(s, 1C), 153.85 (s, 1C), 152.72 (s, 1C), 149.50 (s, 1C), 148.72 (s,
1C), 148.58 (s, 1C), 148.35 (s, 1C), 148.26 (s, 1C), 147.88 (s, 1C),
147.56 (s, 3C), 147.53 (s, 1C), 147.45 (s, 1C), 147.43 (s, 1C),
147.39 (s, 1C), 147.34 (s, 1C), 147.26 (s, 1C), 147.23 (s, 1C),
Photoreactions of C60 with Siliranes 1a-d. A typical procedure
is exemplified by the case of 1a as follows. A toluene solution (25
mL) of C60 (15.0 mg, 2.1 × 10-5 mol) and 1a (11.1 mg, 2.1 ×
10-5 mol) was degassed using freeze-pump-thaw cycles under
reduced pressure. The solution was then irradiated with 500 W
tungsten-halogen lamps through a sodium nitrite filter solution
(cutoff <400 nm) for 2.5 h. The products 2a and 5a were isolated
9
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A R T I C L E S
Nagatsuka et al.
Table 2. Selected Bond Lengths (Å) of 2b, 3b, 4b, and 5a
Scheme 3
bond
lengtha
2b
Si1-C1
Si1-C81
C1-C9
C9-C82
C81-C82
C1-C2
C1-C5
C9-C10
C9-C8
2.005(2) [2.019]
1.882(3) [1.900]
1.611(3) [1.619]
1.583(3) [1.586]
1.537(2) [1.560]
1.532(2) [1.542]
1.521(3) [1.529]
1.526(3) [1.541]
1.544(2) [1.540]
3b
Si1-C1
Si1-C81
Si1-C61
Si1-C71
C1-C9
C9-C82
C81-C82
C1-C2
C1-C5
C9-C94
C8-C9
C5-C6
C7-C8
1.999(2) [2.013]
1.893(2) [1.900]
1.926(2) [1.924]
1.903(2) [1.898]
1.637(3) [1.660]
1.585(3) [1.583]
1.542(3) [1.560]
1.535(3) [1.545]
1.506(3) [1.500]
1.634(2) [1.539]
1.524(3) [1.511]
1.368(3) [1.387]
1.384(3) [1.384]
Table 3. Redox Potentials (V)a of Silylated C60 Derivatives
compound
Eox
Ered
Ered
Ered
3
1
1
2
4b
2a
5a
2b
3b
4b
5b
+0.99b,c
+0.90b,c
+1.08b,d
+0.68b,e
+0.82b,c
+0.94b,c
+1.21b
+0.60b
+0.77b
+0.73b
+0.33b
-1.28d
-1.31c
-1.28d
-1.15e
-1.25c
-1.24c
-1.12
-1.29
-1.21
-1.22
-1.19
-1.66d
-1.72c
-1.74d
-1.73e
-1.68c
-1.68c
-1.50
-1.67
-1.57
-1.61
-1.59
-2.23d
-2.19c
-2.28d
Si1-C1
Si1-C81
Si1-C61
Si1-C71
C1-C5
C5-C6
C6-C7
C7-C8
C8-C9
C1-C9
C81-C82
C7-C82
1.991(2) [1.998]
1.936(2) [1.971]
1.901(2) [1.917]
1.902(2) [1.922]
1.526(2) [1.525]
1.357(2) [1.359]
1.516(2) [1.534]
1.505(2) [1.500]
1.359(2) [1.358]
1.496(2) [1.509]
1.569(2) [1.608]
1.573(2) [1.581]
-2.24c
-1.95
-2.18
-1.97
-2.12
-2.18
f
C60
8f
9g
10h
11h
a Values obtained by DPV are in volts relative to ferrocene/
ferrocenium couple. b Irreversible. c 50 mV/s scan rate. d 20 mV/s scan
rate. e 100 mV/s scan rate. f Reference 3b. g Reference 4d. h Reference
4a.
5a
Si1-C1
Si1-C85
C1-C9
C1-C2
C1-C5
C9-C10
C9-C8
1.991(2)
1.876(3)
1.590(3)
1.529(3)
1.533(3)
1.524(4)
1.538(3)
Hz), 4.42-4.35 (m, 1H), 4.14-4.06 (m, 1H), 3.94 (dd, 1H, J ) 15
Hz, J ) 13 Hz), 3.74-3.60 (m, 2H), 3.26-3.11 (m, 2H), 3.02-2.95
(m, 1H), 2.72-2.63 (m, 1H), 2.55 (dd, 1H, J ) 13 Hz, J ) 2 Hz),
1.94 (t, 3H, J ) 7 Hz), 1.78 (t, 3H, J ) 7 Hz), 1.49 (s, 9H), 0.92
(t, 3H, J ) 7 Hz), 0.57 (t, 3H, J ) 7 Hz); 13C NMR (500 MHz,
CS2/CD2Cl2, 293 K) δ 162.14 (s, 1C), 162.04 (s, 1C), 159.97 (s,
1C), 157.84 (s, 1C), 152.18 (s, 1C), 151.50 (s, 1C), 151.43 (s, 1C),
150.49 (s, 1C), 150.04 (s, 1C), 149.64 (s, 1C), 149.61 (s, 1C),
149.07 (s, 1C), 149.01 (s, 1C), 148.92 (s, 1C), 148.93 (s, 1C),
148.81 (s, 1C), 148.74 (s, 1C), 148.62 (s, 1C), 148.55 (s, 1C),
148.53 (s, 1C), 148.49 (s, 1C), 148.38 (s, 1C), 148.35 (s, 1C),
148.24 (s, 1C), 148.04 (s, 1C), 147.96 (s, 1C), 147.90 (s, 1C),
147.78 (s, 1C), 147.11 (s, 1C), 147.05 (s, 1C), 146.90 (s, 1C),
146.78 (s, 1C), 146.44 (s, 1C), 146.87 (s, 1C), 145.78 (s, 1C),
145.30 (s, 1C), 145.07 (s, 1C), 145.05 (s, 1C), 145.02 (s, 1C),
144.71 (s, 1C), 144.64 (s, 1C), 144.60 (s, 1C), 144.35 (s, 1C),
144.32 (s, 1C), 144.23 (s, 1C), 144.21 (s, 1C), 144.12 (s, 1C),
144.01 (s, 1C), 144.04 (s, 1C), 143.56 (s, 1C), 141.97 (s, 1C),
141.87 (s, 1C), 141.81 (s, 1C), 141.23 (s, 1C), 141.13 (s, 1C),
139.12 (s, 1C), 139.07 (s, 1C), 137.89 (s, 1C), 137.69 (s, 1C),
137.17 (s, 1C), 134.99 (s, 1C), 133.00 (d, 1C), 132.78 (d, 1C),
132.41 (d, 1C), 134.58 (s, 1C), 130.88 (s, 1C), 129.98 (d, 1C),
129.58 (d, 1C), 128.46 (d, 1C), 127.89 (d, 1C), 127.52 (d, 1C),
80.07 (s, 1C; C60C), 74.84 (s, 1C; C60Si), 58.65 (d, 1C; C60CH),
36.66 (t, 1C; CH2), 36.14 (t, 1C; CH2), 33.97 (t, 2C; CH2), 32.85
(s, 4C), 32.82 (t, 1C; CH2), 29.01 (q, 1C; CH3), 18.64 (q, 1C; CH3),
17.98 (q, 1C; CH3), 17.72 (q, 1C; CH3), 16.89 (q, 1C; CH3);
a Bond lengths of optimized structures at the B3LYP/3-21G** level
are in brackets.
147.14 (s, 1C), 146.86 (s, 1C), 146.58 (s, 1C), 146.55 (s, 1C),
146.50 (s, 1C), 146.43 (s, 1C), 146.33 (s, 1C), 145.87 (s, 1C),
145.84 (s, 1C), 145.75 (s, 1C), 145.61 (s, 1C), 145.57 (s, 2C),
145.50 (s, 1C), 145.00 (s, 1C), 144.66 (s, 1C), 144.61 (s, 1C),
144.56 (s, 1C), 144.38 (s, 1C), 143.79 (s, 1C), 143.66 (s, 2C),
146.54 (s, 1C), 143.18 (s, 1C), 143.05 (s, 2C), 142.96 (s, 1C),
142.92 (s, 1C), 142.75 (s, 1C), 142.71 (s, 1C), 142.67 (s, 1C),
142.31 (s, 2C), 142.28 (s, 2C), 141.20 (s, 1C), 140.97 (s, 1C),
140.88 (s, 2C), 140.00 (s, 1C), 139.23 (s, 1C), 138.30 (s, 1C),
136.39 (s, 1C), 136.08 (s, 1C), 135.41 (s, 1C), 135.23 (s, 1C),
132.14 (s, 1C), 130.16 (d, 1C), 129.53 (d, 1C), 129.46 (d, 1C),
128.84 (d, 1C), 128.20 (d, 1C), 128.13 (d, 1C), 127.91(d, 1C),
126.96 (d, 1C), 126.76 (d, 1C), 126.02 (d, 1C), 125.66 (s, 1C; CPh2),
66.92 (s, 1C; C60Si), 61.31 (d, 1C; C60H), 34.96(s, 1C; C(CH3)3),
34.80 (s, 1C; C(CH3)3), 31.97 (q, 3C; C(CH3)3), 31.68 (q, 3C;
C(CH3)3), 28.11 (q, 1C; CH3), 28.05 (q, 1C; CH3), 27.30 (q, 1C;
CH3), 25.92 (q, 1C; CH3); vis-NIR (toluene) λmax 446, 316 nm;
MALDI-TOF MS m/z 1250 (M-), 720 (C60-), 529 (M--C60H).
Data for 2b: dark brown solid; 1H NMR (500 MHz, CS2/CD2Cl2,
293 K) δ 7.66-7.02 (m, 10H), 5.31(dd, 1H, J ) 15 Hz, J ) 2
9
12116 J. AM. CHEM. SOC. VOL. 132, NO. 34, 2010

Photochemical Addition of C60 with Siliranes
A R T I C L E S
Figure 9. Cyclic voltammograms (CV) and differential pulse voltammograms (DPV) of 2a (a), 5a (b), 2b (c), 3b (d), 4b (e), and 5b (f) in 1,2-dichlorobenzene
containing 0.1 M (n-butyl)4NPF6. The peaks of monosilylated C60 derivatives are marked by red b. Condition: working electrode, Pt disk (1 mm diameter);
counter electrode, Pt wire; reference electrode, SCE. Redox potentials are in volts relative to ferrocene/ferrocenium couple.
9
J. AM. CHEM. SOC. VOL. 132, NO. 34, 2010 12117

A R T I C L E S
Nagatsuka et al.
1.98(m, 1H), 1.00(s, 9H), 0.98(s, 9H), 0.81(s, 9H); 13C NMR (125
MHz, C6D6, 293 K) δ 161.5(s, 1C), 160.1 (s, 1C), 157.5 (s, 1C),
156.9 (s, 1C), 153.6 (s, 1C), 152.7 (s, 1C), 149.4 (s, 1C), 147.4 (s,
1C), 146.8 (s, 1C), 146.7 (s, 3C), 146.6 (s, 1C), 146.5 (s, 1C), 146.4
(s, 2C), 146.3 (s, 3C), 145.8 (s, 1C), 145.7 (s, 1C), 145.6 (s, 3C),
145.5 (s, 2C), 145.0 (s, 2C), 144.5 (s, 2C), 144.4 (s, 1C), 144.0 (s,
1C), 143.8 (s, 1C), 143.7 (s, 1C), 143.3 (s, 1C), 143.2 (s, 3C), 143.1
(s, 1C), 143.0 (s, 1C), 142.8 (s, 1C), 142.6 (s, 1C), 142.5 (s, 1C),
142.4 (s, 1C), 142.2 (s, 1C), 142.1 (s, 1C), 142.0 (s, 1C), 141.8 (s,
1C), 140.2 (s, 1C), 139.6 (s, 1C), 139.2 (s, 1C), 138.5 (s, 1C), 137.2
(s, 1C), 136.2 (s, 1C), 136.0 (s, 1C), 132.8 (s, 1C), 132.6 (s, 1C),
124.8 (s, 1C), 125.2 (s, 1C), 124.6 (s, 1C), 124.3 (s, 1C), 75.6 (s,
1C), 74.6 (s, 1C), 62.9(d, 1C; SiCH2CH), 35.5 (s, 1C; tBu), 33.0
(s, 2C; tBu), 29.9 (q, 3C; tBu), 29.8 (q, 3C; tBu), 29.7 (q, 3C;
tBu), 28.0 (q, 1C; CH3), 25.1 (q, 1C; CH3), 24.1 (q, 1C; CH3),
22.7 (q, 1C; CH3), 20.5 (t, 1C; SiCH2); vis-NIR (toluene) λmax
312, 443 nm; MALDI-TOF MS m/z 1154 (M-), 720 (C60-).
Chart 3
Data for 2d: dark brown solid; 1H NMR (300 MHz, C6D6/CS2,
383 K) δ 6.83(s, 4H), 3.48(t, 2H, J ) 6.6 Hz), 2.56(s, 12H), 2.31(t,
1
2H, J ) 6.6 Hz), 1.02(s, 18H); H NMR (300 MHz, C6D6/CS2,
223 K) δ 7.15(s, 1H), 6.98(s, 1H), 6.90(s, 1H), 6.71(s, 1H), 3.72(m,
2H), 3.35(s, 3H), 3.00(m, 1H), 2.84(s, 3H), 2.37(s, 3H), 2.21(s,
3H), 2.02(m, 1H), 1.34(s, 9H), 1.16(s, 9H); vis-NIR (toluene) λmax
310, 330, 443 nm; MALDI-TOF MS m/z 1098 (M-), 720 (C60-).
X-ray Crystallography of 2b, 3b, 4b, and 5a. Crystals of 2b
were obtained using liquid-liquid bilayer diffusion method of
an ODCB solution of 2b using hexane as a poor solvent. Crystals
of 4b and 5a were obtained by slow evaporation of the
corresponding solutions in mixed solvents of CS2 and toluene.
Mixed crystals of 2b and 3b were also obtained using a similar
procedure from a solution containing 2b and 3b in a mixed
solvent of CS2 and toluene. Single-crystal X-ray diffraction data
of 2b were collected on a Rigaku Saturn CCD area detector
(Rigaku Corp.) with graphite monochromated Mo-KR radiation.
Those of 4b, 5a, and mixed crystals of 2b and 3b were collected
on a Rigaku RAXIS-RAPID IP area detector (Rigaku Corp.).
Crystal Data for 2b: C92H42Si, Mr ) 1175.43, black platelet,
0.20 × 0.13 × 0.11 mm3, monoclinic, P21/n (No. 14), a )
12.777(3), b ) 23.903(5), c ) 18.151(4) Å, ꢀ ) 106.495(4)°, V )
5315(2) Å3, Z ) 4; Fcalcd ) 1.469 g cm-3, µ(Mo KR) ) 0.105
mm-1, θmax ) 29.57°, T ) 100.1 K, 38,924 measured reflections,
14,592 independent reflections, 839 refined parameters, GOF )
1.024, R1 ) 0.1346 and wR2 ) 0.2675 for all data; R1 ) 0.0869
for 8633 independent reflections (I > 2.0σ(I)), largest difference
peak and hole 1.45 and -0.50 e Å-3, respectively.
Crystal Data for 2b and 3b: (2b and 3b made mixed crystals
in a mixing ratio of 61 (2b):39 (3b), respectively) C92H42Si, Mr
) 1175.43, black block, 0.10 × 0.10 × 0.10 mm3, monoclinic,
P21/n (No. 14), a ) 12.7665(5), b ) 23.9369(10), c ) 18.2436(6)
Å, ꢀ ) 106.8259(10)°, V ) 5336.4(4) Å3, Z ) 4; Fcalcd ) 1.463
g cm-3, µ(Mo KR) ) 0.104 mm-1, θmax ) 27.39°, T ) 120.1 K,
40,593 measured reflections, 11,992 independent reflections,
1291 refined parameters, GOF ) 1.028, R1 ) 0.0926 and wR2
) 0.1784 for all data; R1 ) 0.0630 for 8482 independent
reflections (I > 2.0σ(I)), largest difference peak and hole 0.59
and -0.34 e Å-3, respectively.
Crystal Data for 4b ·(C7H8)2: C106H58Si, Mr ) 1359.71, black
block, 0.74 × 0.40 × 0.40 mm3, monoclinic, P21/n (No. 14), a )
19.694(4), b ) 13.366(2), c ) 24.195(4) Å, ꢀ ) 90.091(8)°, V )
6369.0(18) Å3, Z ) 4; Fcalcd ) 1.418 g cm-3, µ(Mo KR) ) 0.098
mm-1, θmax ) 27.49°, T ) 100.1 K, 61,116 measured reflections,
14,522 independent reflections, 965 refined parameters, GOF )
1.030, R1 ) 0.0734 and wR2 ) 0.1833 for all data; R1 ) 0.0665
for 12,708 independent reflections (I > 2.0σ(I)), largest difference
peak and hole 2.14 and -0.83 e Å-3, respectively.
vis-NIR (toluene) λmax 719, 442 nm; MALDI-TOF MS m/z 1274
(M-), 720 (C60-).
Data for 3b: dark brown solid; 1H NMR (500 MHz, CS2/CD2Cl2,
293 K) δ 7.71-7.12 (m, 10H), 4.51 (dd, 1H, J ) 15 Hz, J ) 2
Hz), 3.74 (dd, 1H, J ) 15 Hz, J ) 13 Hz), 3.62-3.51 (m, 2H),
3.21-3.08 (m, 4H), 2.89-2.69 (m, 2H), 1.97 (dd, 1H, J ) 13 Hz,
J ) 2 Hz), 1.68 (t, 3H, J ) 7 Hz), 1.64 (t, 3H, J ) 7 Hz), 1.50 (s,
9H), 0.93 (t, 3H, J ) 7 Hz), 0.53 (t, 3H, J ) 7 Hz); 13C NMR (500
MHz, CS2/CD2Cl2, 293 K) δ 157.91 (s, 1C), 156.82 (s, 1C), 152.31
(s, 1C), 152.19 (s, 1C), 152.04 (s, 1C), 151.68 (s, 1C), 151.57 (s,
1C), 151.06 (s, 1C), 150.81 (s, 1C), 150.68 (s, 1C), 150.47 (s, 1C),
150.28 (s, 1C), 150.01 (s, 1C), 149.53 (s, 1C), 149.24 (s, 1C),
148.94 (s, 1C), 148.68 (s, 1C), 148.60 (s, 1C), 148.31 (s, 1C),
148.00 (s, 1C), 147.98 (s, 1C), 147.97 (s, 1C), 147.66 (s, 1C),
147.50 (s, 1C), 147.39 (s, 1C), 147.24 (s, 1C), 147.21 (s, 1C),
146.99 (s, 2C), 146.63 (s, 1C), 146.57 (s, 1C), 146.46 (s, 1C),
145.04 (s, 1C), 144.83 (s, 1C), 144.66 (s, 1C), 144.33 (s, 1C),
143.95 (s, 1C), 143.88 (s, 1C), 143.83 (s, 1C), 143.70 (s, 1C),
143.49 (s, 1C), 142.55 (s, 1C), 142.14 (s, 1C), 141.79 (s, 1C),
141.51 (s, 1C), 141.26 (s, 1C), 140.07 (s, 1C), 139.95 (s, 1C),
139.82 (s, 1C), 139.51 (s, 1C), 139.38 (s, 2C), 139.33 (s, 1C),
139.03 (s, 1C), 138.66 (s, 1C), 138.34 (s, 1C), 137.99 (s, 1C),
137.48 (s, 1C), 136.99 (s, 1C), 136.84 (s, 1C), 134.66 (s, 1C),
134.00 (s, 1C), 133.25 (d, 1C), 132.69 (s, 1C), 132.64 (d, 1C),
132.25 (d, 1C), 132.10 (s, 1C), 131.68 (d, 1C), 130.88 (d, 1C),
129.89 (d, 1C), 129.82 (d, 1C), 128.28 (d, 1C), 128.23 (d, 1C),
127.38 (d, 1C), 76.98 (s, 1C; C60C), 74.52 (s, 1C; C60Si), 59.43 (d,
1C; C60CH), 36.69 (s, 1C; C(CH3)3), 35.30 (t, 1C; CH2), 35.22 (t,
1C; CH2), 34.03 (q, 3C; C(CH3)3), 32.65 (t, 1C; CH2), 32.48 (t,
1C; CH2), 22.40 (t, 1C; CH2), 18.41 (q, 1C; CH3), 17.98 (q, 1C;
CH3), 17.92 (q, 1C; CH3), 17.66 (q, 1C; CH3); vis-NIR (toluene)
no absorption maximum; MALDI-TOF MS m/z 1274 (M-), 720
(C60-).
Data for 4b: dark brown solid; 1H NMR (300 MHz, CS2/CD2Cl2,
293 K) δ 7.97-7.11 (m, 10H), 5.01 (dd, 1H, J ) 10 Hz, J ) 5
Hz), 4.16 (dd, 1H, J ) 15 Hz, J ) 10 Hz), 3.53-3.22 (m, 4H),
3.01-2.82 (m, 4H), 2.64 (dd, 1H, J ) 15 Hz, J ) 5 Hz), 1.84 (t,
3H, J ) 7 Hz), 1.68 (t, 3H, J ) 7 Hz), 1.60 (s, 9H), 0.78 (t, 3H,
J ) 7 Hz), 0.64 (t, 3H, J ) 7 Hz); vis-NIR (toluene) λmax 552,
467, 443 nm; MALDI-TOF MS m/z 1274 (M-), 720 (C60-).
Data for 5b: dark brown solid; vis-NIR (toluene) λmax 726, 445
nm; MALDI-TOF MS m/z 1274 (M-), 720 (C60-).
Crystal Data for 5a · (C7H8): C105H54Si, Mr ) 1343.67, black
prism, 0.58 × 0.34 × 0.20 mm3, monoclinic, P21/c (No. 14), a
) 14.287(2), b ) 23.441(5), c ) 19.533(3) Å, ꢀ ) 104.270(5)°,
V ) 6339.8(18) Å3, Z ) 4; Fcalcd ) 1.408 g cm-3, µ(Mo KR) )
Data for 2c: dark brown solid; 1H NMR (300 MHz, C6D6/CS2,
293 K) δ 7.36(s, 1H), 7.12(s, 1H), 7.09(s, 1H), 6.80(s, 1H), 3.67(m,
1H), 3.23(s, 3H), 2.95(m 1H), 2.62(s, 3H), 2.34(s, 3H), 2.07(s, 3H),
9
12118 J. AM. CHEM. SOC. VOL. 132, NO. 34, 2010

Photochemical Addition of C60 with Siliranes
A R T I C L E S
Figure 10. Optimized structures of 2b (a), 3b (b), and 4b (c) at the B3LYP/3-21G** level.
Table 4. Ground-State Relative Energies Computed at the AM1
data; R1 ) 0.0778 for 10,377 independent reflections (I >
2.0σ(I)), largest difference peak and hole 1.13 and -0.72 e Å-3
,
and B3LYP/3-21G** Levels and HOMO and LUMO Energies (eV)
at the B3LYP/3-21G** level
respectively.
Erel (kcal/mol)
CCDC 767620 (2b), 767619 (2b and 3b mixed crystal), 767618
(4b), and 767617 (5a) contain the supplementary crystallographic
data for this paper. These data are obtainable free of charge from
The Cambridge Crystallographic Data Centre via www.ccdc.
cam.ac.uk/data_request/cif.
adduct
AM1
B3LYP/3-21G**
EHOMO
ELUMO
∆Eb
2b
3b
4b
0.0
17.1
21.8
0.0 (0.0)a
18.7 (15.5)a
23.6 (22.8)a
-5.85
-5.41
-5.85
-3.21
-3.54
-3.29
2.64
1.88
2.56
Computational Method. Full geometry optimizations were
performed at AM1; then they were reoptimized at B3LYP/3-
21G**.21 B3LYP/6-31G** single-point energies were computed
using B3LYP/3-21G** optimized geometries.
a Single point energies at B3LYP/6-31G**level are in parentheses.
b ∆E ) ELUMO - EHOMO
.
0.098 mm-1, θmax ) 27.49°, T ) 90.1 K, 57,893 measured
reflections, 14,038 independent reflections, 1123 refined param-
eters, GOF ) 1.047, R1 ) 0.1047 and wR2 ) 0.2284 for all
Acknowledgment. This work was supported in part by a
Grant-in-Aid for Scientific Research on Innovative Areas (No.
9
J. AM. CHEM. SOC. VOL. 132, NO. 34, 2010 12119

A R T I C L E S
Nagatsuka et al.
20108001, “pi-Space”), a Grant-in-Aid for Scientific Research
(A) (No. 20245006). The Next Generation Super Computing
Project (Nanoscience Project), Nanotechnology Support Project,
and Grant-in-Aid for Scientific Research on Priority Area (Nos.
20036008, 20038007) from the Ministry of Education, Culture,
Sports, Science, and Technology of Japan.
Supporting Information Available: Complete refs 8b,8g,8l, 19,
and 21d; crystallographic data in CIF format; spectroscopic data;
and theoretical results for the silylated fullerenes. This material is
available free of charge via the Internet at http://pubs.acs.org.
JA1049719
9
12120 J. AM. CHEM. SOC. VOL. 132, NO. 34, 2010