Syntheses, structure, and derivatization of potassium complexes of penta(organo)[60]fullerene-monoanion, -dianion, and -trianion into hepta- and octa(organo)fullerenes

Article abstract of DOI:10.1021/ja050318x

Two-electron reduction of penta(organo)[60]fullerenes C₆₀Ar ₅H (Ar = Ph and biphenyl) by potassium/mercury amalgam afforded potassium complexes of the corresponding open-shell radical dianions [K ⁺(thf)_n]₂[C₆₀Ar₅ ^2-.]. These compounds were characterized by UV-visible-near-IR and electron spin resonance spectroscopy in solution. Anaerobic crystallization of [K⁺(thf)_n]₂[C₆₀(biphenyl) ₅^2-.] that exists largely as a monomer in solution gave black crystals of its dimer [K⁺(thf)₃] ₄[(biphenyl)₅C₆₀-C₆₀(biphenyl) ₅^4-], in which the two fullerene units are connected by a C-C single bond [1.577(11) A] as determined by X-ray diffraction. Three-electron reduction of C⁶⁰Ar₅H with metallic potassium gave a black-green trianion [K⁺(thf)_n] ₃[C₆₀Ar₅^3-]. The reaction of the trianion with an alkyl halide RBr (R = PhCH₂ and Ph₂CH) regioselectively afforded a hepta-organofullerene C₆₀Ar ₅R₂H, from which a potassium complex [K ⁺(thf)_n][C₆₀(biphenyl)₅(CH ₂Ph)₂^-] and a palladium complex Pd[C ₆₀(biphenyl)₅(CH₂Ph)₂](π- methallyl) as well as octa-organofullerene compounds C₆₀(biphenyl) ₅(CH₂Ph)₃H₂ and Ru[C ₆₀(biphenyl)₅(CH₂Ph)₃H]Cp were synthesized. These compounds possess a dibenzo-fused corannulene π-electron conjugated system and are luminescent.

Full text of DOI:10.1021/ja050318x

Published on Web 05/20/2005
Syntheses, Structure, and Derivatization of Potassium
Complexes of Penta(organo)[60]fullerene-Monoanion,
-Dianion, and -Trianion into Hepta- and
Octa(organo)fullerenes
Yutaka Matsuo† and Eiichi Nakamura*,†,‡
Contribution from the Nakamura Functional Carbon Cluster Project, ERATO, Japan Science
and Technology Agency and Department of Chemistry, The UniVersity of Tokyo, Hongo,
Bunkyo-ku, Tokyo 113-0033, Japan
Received January 18, 2005; E-mail: nakamura@chem.s.u-tokyo.ac.jp
Abstract: Two-electron reduction of penta(organo)[60]fullerenes C60Ar5H (Ar ) Ph and biphenyl) by
potassium/mercury amalgam afforded potassium complexes of the corresponding open-shell radical dianions
[K+(thf)n]2[C60Ar52-•]. These compounds were characterized by UV-visible-near-IR and electron spin
resonance spectroscopy in solution. Anaerobic crystallization of [K+(thf)n]2[C60(biphenyl)52-•] that exists largely
as a monomer in solution gave black crystals of its dimer [K+(thf)3]4[(biphenyl)5C60-C60(biphenyl)54-],
in which the two fullerene units are connected by a C-C single bond [1.577(11) Å] as determined by X-
ray diffraction. Three-electron reduction of C60Ar5H with metallic potassium gave a black-green tri-
anion [K+(thf)n]3[C60Ar53-]. The reaction of the trianion with an alkyl halide RBr (R ) PhCH2 and
Ph2CH) regioselectively afforded a hepta-organofullerene C60Ar5R2H, from which a potassium complex
[K+(thf)n][C60(biphenyl)5(CH2Ph)2-] and a palladium complex Pd[C60(biphenyl)5(CH2Ph)2](π-methallyl) as well
as octa-organofullerene compounds C60(biphenyl)5(CH2Ph)3H2 and Ru[C60(biphenyl)5(CH2Ph)3H]Cp were
synthesized. These compounds possess a dibenzo-fused corannulene π-electron conjugated system and
are luminescent.
Introduction
structurally more complex, functional fullerene compounds,
regio- and chemoselective derivatization of the fullerene core
Organic functionalization of [60]fullerene has created a
number of organic derivatives, and has significantly expanded
the scope of the science of carbon clusters. Water-soluble
derivatives1 and organometallic complexes2,3 are representative
of such organofullerene compounds. For the synthesis of
of the organofullerene compounds becomes necessary (cf.
second-stage functionalization such as the one shown in Scheme
1): This poses synthetic problems even more challenging than
those already imposed on the initial organo-derivatization of
the parent fullerene.4 Organic derivatization of organofullerene
has been largely achieved in two ways: first, by addition of a
nucleophile to neutral fullerene core4 and, second, by electro-
philic reaction of anionic fullerene core generated by deproto-
nation of hydrofullerene or by reduction of fullerene. Among
the latter method, the hydrofullerene route has already proven
useful for the two-stage functionalization. For instance, a
cyclopentadienide anion 1 and a bucky ferrocene anion 2 have
been alkylated in high yield to give a variety of functionalized
fullerene derivatives5 and metal complexes3g (Scheme 1).
However, anion and polyanions of organofullerenes are less
synthetically useful, in contrast to the case known for the parent
† Nakamura Functional Carbon Cluster Project, ERATO.
‡ The University of Tokyo.
(1) (a) Sawamura, M.; Nagahama, N.; Toganoh, M.; Hackler, U. E.; Isobe,
H.; Nakamura, E.; Zhou, S.-Q.; Chu, B. Chem. Lett. 2000, 1098-1099.
(b) Zhou, S.; Burger, C.; Chu, B.; Sawamura, M.; Nagahama, N.; Toganoh,
M.; Hackler, U. E.; Isobe, H.; Nakamura, E. Science 2001, 291, 1944-
1947. (c) Nakamura, E.; Isobe, H. Acc. Chem. Res. 2003, 36, 807-815.
(d) Burger, C.; Hao, J.; Ying, Q.; Isobe, H.; Sawamura, M.; Nakamura, E.;
Chu, B. J. Colloid Interface Sci. 2004, 275, 632-641.
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12850-12851. (b) Iikura, H.; Mori, S.; Sawamura, M.; Nakamura, E. J.
Org. Chem. 1997, 62, 7912-7913. (c) Sawamura, M.; Toganoh, M.;
Kuninobu, Y.; Kato, S.; Nakamura, E. Chem. Lett. 2000, 270-271. (d)
Sawamura, M.; Iikura, H.; Ohama, T.; Hackler, U. E.; Nakamura, E. J.
Organomet. Chem. 2000, 599, 32-36. (e) Nakamura, E.; Sawamura, M.
Pure Appl. Chem. 2001, 73, 355-359.
(3) (a) Sawamura, M.; Kuninobu Y.; Nakamura E. J. Am. Chem. Soc. 2000,
122, 12407-12408. (b) Sawamura, M.; Kuninobu, Y.; Toganoh, M.;
Matsuo, Y.; Yamanaka, M.; Nakamura, E. J. Am. Chem. Soc. 2002, 124,
9354-9355. (c) Nakamura, E. Pure Appl. Chem. 2003, 75, 427-434. (d)
Matsuo, Y.; Nakamura, E. Organometallics 2003, 22, 2554-2563. (e)
Toganoh, M.; Matsuo, Y.; Nakamura, E. Angew. Chem., Int. Ed. 2003, 42,
3530-3532. (f) Toganoh, M.; Matsuo, Y.; Nakamura, E. J. Organomet.
Chem. 2003, 683, 295-300. (g) Toganoh, M.; Matsuo, Y.; Nakamura, E.
J. Am. Chem. Soc. 2003, 125, 13974-13975. (h) Matsuo, Y.; Kuninobu,
Y.; Ito, S.; Nakamura, E. Chem. Lett. 2004, 33, 68-69. (i) Kuninobu, Y.;
Matsuo, Y.; Toganoh, M.; Sawamura, M.; Nakamura, E. Organometallics
2004, 23, 3259-3266. (j) Matsuo, Y.; Iwashita, A.; Nakamura, E.
Organometallics 2005, 24, 89-95.
2-
fullerene-dianion C60 that reacts with an alkyl halide giving
C60(alkyl)2.6-12 The organofullerene-polyanions have been
(4) (a) Nakamura, E.; Tahara, K.; Matsuo, Y.; Sawamura, M. J. Am. Chem.
Soc. 2003, 125, 2834-2835. (b) Matsuo, Y.; Tahara, K.; Sawamura, M.;
Nakamura, E. J. Am. Chem. Soc. 2004, 126, 8725-8734.
(5) Hamasaki, R.; Matsuo, Y.; Nakamura, E. Chem. Lett. 2004, 33, 328-329.
(6) Caron, C.; Subramanian, R.; D’Souza, F.; Kim, J.; Kutner, W.; Jones, M.
T.; Kadish, K. M. J. Am. Chem. Soc. 1993, 115, 8505-8506.
(7) Subramanian, R.; Kadish, M. K.; Vijayashree, N. M.; Gao, X.; Jones, T.
M.; Miller, D. M.; Krause, K. L.; Suenobu, T.; Fukuzumi, S. J. Phys. Chem.
1996, 100, 16327-16335.
9
10.1021/ja050318x CCC: $30.25 © 2005 American Chemical Society
J. AM. CHEM. SOC. 2005, 127, 8457-8466
8457

A R T I C L E S
Scheme 1
Matsuo and Nakamura
Scheme 2
generated and studied by cyclic voltammetry but seldom
isolated,13,14 structurally characterized, or examined for their
synthetic utility. The reduction potentials required to reduce
the functionalized fullerenes that are generally higher than those
of the parent fullerene,15 the symmetry of the function-
alized fullerenes, inherently lower in level than that of [60]-
fullerene, and the instability of reduced species sometimes
observed16,17 make the studies on the structures and reactivities
rather difficult.
The anion 12 (Scheme 1) is an electronically interesting
compound as it contains a cyclopentadienide moiety homo-
conjugated with the bottom 50π-electron system.2b We consid-
ered that this structural feature may favorably affect the
reduction chemistry so that the resulting polyanion can be used
for further chemical functionalization. Described in this article
are the results of controlled reduction of the penta(aryl)[60]-
fullerene C60Ar5H (Ar ) biphenyl and Ph; 3),18 which led to
generation and characterization of the potassium salts of the
C60Ar5 mono-, di-, and trianions (Scheme 2) as well as their
regioselective derivatization into new a type of fullerene
molecules bearing seven and eight organic groups (7-13). The
dianion was found to give upon crystallization a tetraanionic
dimer [K+(thf)3]4[(biphenyl)5C60-C60(biphenyl)54-] (5a), where
the two fullerene radical dianions are connected by a C-C
σ-bond.
Results and Discussion
Structure and Electrochemical Property of Pentakis-
(biphenyl)[60]fullerene Monoanion 1. To start the studies on
the polyanions of penta(organo)[60]fullerene, we first examined
the properties of the monoanion 1, which will be further reduced
to the di- and trianions. In our previous reports,1-5 we often
-
referred to the generation of the monoanion C60Ar5 (1) yet
without any structural data. Treatment of C60Ar5H (3) with K/Hg
first reduces the bottom 50π-part, which is followed by loss of
hydrogen from the top cyclopentadiene moiety to generate 1.2b
Alternatively, deprotonation of 3 with KH also generates 1. Such
operations generate C60Ar5K, which may be either a true anion
C60Ar5- having a solvent separated K+ (i.e., [K+(thf)n][C60Ar5-]),
or a complex having direct C-K contact. To probe this issue
we have chosen pentakis(biphenyl)[60]fullerene C60(biphenyl)5H19
(3a; pentakis(biphenyl) derivatives are denoted as “a”) and
penta(phenyl)[60]fullerene C60Ph5H (3b; penta(phenyl) deriva-
tives are denoted as “b”).2 The biphenyl compound was
particularly intriguing for its ability to form a one-dimensional
stacked array through inclusion of another molecule into the
cavity created by the wall of the five biphenyl groups.19,20,21
[K+(thf)6][C60(biphenyl)5-] (1a) was prepared by deproto-
nation of C60(biphenyl)5H with KH in THF (Scheme 2), and
single crystals were obtained by slow diffusion of hexane into
a THF solution of 1a under Ar atmosphere. The crystal structure
of 1a (Figures 1 and 2) indicates that the potassium atom is
trapped inside the biphenyl cavity, and hence, there is no one-
dimensional stacking of the fullerene molecules.19 The potassium
ion in 1a is solvated by six THF molecules leaving the
fullerene-cyclopentadienide as a free anion. The positively
(8) Fukuzumi, S.; Suenobu, T.; Hirasaka, T.; Arakawa, R.; Kadish, K. M. J.
Am. Chem. Soc. 1998, 120, 9220-9227.
(9) Cheng, F.; Murata, Y.; Komatsu, K. Org. Lett. 2002, 4, 2541-2544.
(10) Miki, S.; Kitao, M.; Fukunishi, K. Tetrahedron Lett. 1996, 37, 2049-2052.
(11) (a) Allard, E.; Rivie´re, L.; Delaunay, J.; Dubois, D.; Cousseau, J.
Tetrahedron Lett. 1999, 40, 7223-7226. (b) Allard, E.; Delaunay, J.; Cheng,
F.; Cousseau, J.; Ordu´na, J.; Gar´ın, J. Org. Lett. 2001, 3, 3503-3506. (c)
Allard, E.; Delaunay, J.; Cousseau, J. Org. Lett. 2003, 5, 2239-2242.
(12) Taylor, R. Lecture Notes on Fullerene Chemistry. A Handbook for Chemists;
Imperial College Press: London, UK, 1999.
(13) Konarev, D. V.; Khasanov, S. S.; Otsuka, A.; Yoshida, Y.; Saito, G. J.
Am. Chem. Soc. 2002, 124, 7648-7649.
(14) (a) Tanaka, T.; Kitagawa, T.; Komatsu, K.; Takeuchi, K. J. Am. Chem.
Soc. 1997, 119, 9313-9314. (b) Kitagawa, T.; Tanaka, T.; Takata, Y.;
Takeuchi, K.; Komatsu, K. Tetrahedron 1997, 53, 9965-9976.
(15) Fullerene derivatives bearing strong electron-withdrawing groups show
lower reduction potential. Cf. Keshavarz-K, M.; Knight, B.; Srdanov, G.;
Wudl, F. J. Am. Chem. Soc. 1995, 117, 11371-11372.
(16) (a) Yanilkin, V. V.; Nastapova, N. V.; Gubskaya, V. P.; Morozov, V. I.;
Berezhnaya, L. Sh.; Nuretdinov, I. A. Rus. Chem. Bull. 2002, 51, 72-77.
(b) Nuretdinov, I. A.; Morozov, V. I.; Gubskaya, V. P.; Yanilkin, V. V.;
Berezhnaya, L. Sh.; Il’yasov, A. V. Russ. Chem. Bull. 2002, 51, 813-816.
(17) Keshavarz-K, M.; Knight, B.; Haddon, C.; Wudl, F. Tetrahedron 1996,
52, 5149-5159.
(18) Though the chemistry of compounds with the Ar groups other than phenyl
and biphenyl as well as C60Me5 is expected to be very similar to that of
3a,b, these latter compounds gave much better defined products as described
in the text.
(19) Sawamura, M.; Kawai, K.; Matsuo, Y.; Kanie, K.; Kato, T.; Nakamura, E.
Nature 2002, 419, 702-705.
(20) Matsuo, Y.; Muramatsu, A.; Hamasaki, R.; Mizoshita, N.; Kato T.;
Nakamura, E. J. Am. Chem. Soc. 2004, 126, 432-433.
(21) Okada, S.; Arita, R.; Matsuo, Y.; Nakamura, E.; Oshiyama, A.; Aoki, H.
Chem. Phys. Lett. 2004, 399, 157-161.
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Synthesis of Useful Organofullerene Polyanions
A R T I C L E S
Figure 3. Cyclic voltammogram of 1a at 25 °C in a 1.0 mM THF solution
containing 100 mM [nBu4N][ClO4] as a supporting electrolyte. The red area
indicates roughly where anionic charge may reside.
Scheme 3
Figure 1. ORTEP drawing of 1a‚(THF)3. THF molecules in the crystal
packing are omitted for clarity. Thermal ellipsoids are drawn in 30%
probability level. Bond lengths (Å): K-O1 ) 2.674(4), K-O2 ) 2.723-
(5), K-O3 ) 2.759(6), K-O4 ) 2.616(5), K-O5 ) 2.707(6), K-O6 )
2.819(6).
Figure 2. CPK model of 1a. Six THF molecules coordinating to the
potassium ion are drawn in stick representation. (a) Top view. (b) Side
view.
red1
red2
pound 1b is reduced at E1/2
) -1.84 and E1/2
) -2.52
V (vs Fc/Fc+) at -78 °C in THF under cyclic voltammetric
condition, and the single-crystal-grade sample of 1a showed
reversible two-electron reduction at E1/2red1 ) -1.69 and E1/2
charged K+(thf)6 is obviously a better guest to the cavity than
the negatively charged C60Ar5-. To create a one-dimensional
stack of C60Ar5- as in the case of C60Ar5H, we need to consider
further engineering. The bond lengths (Table S1 in Supporting
Information) follow the conventional single/double bond nota-
tion shown for the structure 1 in Scheme 1. Thus, the average
bond length (1.41 Å) in the cyclopentadienide [C(Cp)-C(Cp)]]
is between the C-C bond (1.43-5 Å) and CdC bond (1.38-9
Å) found in 1, and much shorter than the bond length on the
(5,6) ring junction found in [60]fullerene (1.47 Å).22 The bottom
50π-electron system of 1a shows a smaller degree of bond
alternation than that in [60]fullerene.
Next we examined reduction potential of 1 to choose proper
reducing reagents to obtain di- and trianion. The cyclic
voltammogram of penta(phenyl)[60]fullerene anion (1b, C60Ph5-)
was previously reported2b and is compared here with that of
the penta(biphenyl)[60]fullerene anion 1a. The phenyl com-
red2
) -2.26 V (vs Fc/Fc+) at 25 °C in THF without decomposition
(Figure 3).23 We ascribe the difference between 1a and 1b to
the effect of the electron-withdrawing p-phenyl groups. On the
basis of the data, we decided to use potassium/mercury amalgam
(reduction potential ) ca. 2.0 V)24 to reduce the monoanions
1a and 1b selectively into the penta(organo)[60]fullerene
dianions and to use potassium metal (reduction potential ) ca.
2.7 V) to synthesize the trianions.
Synthesis, Structure, and Spectral Properties of Pentakis-
(biphenyl)[60]fullerene Radical Dianion 4a. One-electron
reduction of 1a by 1 wt % K/Hg amalgam in THF at 25 °C
gave the pentakis(biphenyl)[60]fullerene radical dianion,
[K+(thf)n]2[C60(biphenyl)52-•] (4a) (Scheme 3). The color of the
THF solution changed gradually from dark red to black during
red1
red2
(23) Fullerene is reduced at E1/2
) -0.86 V and E1/2
) -1.44 V (Fc/
Fc+) in THF. Cf. Lerke, S. A.; Parkinson, B. A.; Evans, D. H.; Fagan, P.
J. J. Am. Chem. Soc. 1992, 114, 7807-7813.
(24) Connelly, N. G.; Geiger, W. E. Chem. ReV. 1996, 96, 877-910.
(22) Liu, S.; Lu, Y.-J.; Kappes, M. M.; Ibers, J. A. Science 1991, 254, 408-
410.
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A R T I C L E S
Matsuo and Nakamura
the reaction for 12 h. After removal of excess K/Hg amalgam,
solvent was removed under reduced pressure to obtain air- and
moisture-sensitive black crystals in quantitative yield. The
reduction of C60(biphenyl)5H (3a) was performed under the same
1
conditions. A THF-d8 solution of 4a exhibited no H and 13C
NMR signals, and a THF solution of 4a was ESR active (vide
infra). On the basis of a series of analyses discussed below, 4a
in solution exists predominantly as an open-shell radical dianion
that can be formulated to have a negative charge on the
cyclopentadienide and a radial anion on the bottom π-electron
system (Scheme 3).
In contrast to the high nucleophilic reactivity of the trianion
discussed later, the radial dianion 4a,b acts only as a reducing
agent, reacting with benzyl bromide at 25 °C to give bibenzyl
and the starting material 3a,b (after treatment with aqueous
HCl). Apparently, a single-electron transfer from 4a,b to benzyl
bromide took place to generate benzyl radical, which then
dimerized to give bibenzyl. The observed chemical behavior is
typical of a monomeric radical dianion 4a,b rather than a dimer
[K+(thf)3]4[Ar5C60-C60Ar54-] (5a,b)san issue that surfaced in
the experimental finding described in the next paragraph.
Attempted isolation of this radical dianion by recrystallization
(slow diffusion of hexane into a THF solution) unexpectedly
gave a black-colored air-sensitive dimer 5a (Scheme 3). The
isolation of the dimer is a good indication of the radical dianionic
-•
nature of 4a, in the light of the behavior of a radical anion C60
that exists predominantly as a monomer in solution at room
temperature but in equilibrium with its dimer (C60-C60)2- 25,26
.
Similarly, the K/Hg reduction of [K+(thf)n][C60Ph5-] (or C60-
Ph5) afforded black crystals of [K+(thf)n]2[C60Ph52-•] (4b),
which are also ESR active and air-sensitive.
Figure 4. Crystal structure of 5a‚(THF)6‚(hexane). ORTEP drawing with
20% probability level ellipsoid. Solvent molecules in the crystal packing
are omitted for clarity.
As found by X-ray crystallographic analysis at 153 K (Figure
4), the dimer exists in an anti conformation (i.e., for the
interfullerene bond) as predicted by theory for (C60-C60)2- 27,28
.
an η3-fashion both to the cyclopentadienide and to the phenyl
group, forming a bent sandwich structure. In Figure 5b, we see
that potassium ion K2 is attached in an η2- and η6-fashion to a
C48*-C49* bond and a C44-C45-C53-C58-C57-C52
hexagon of two fullerene bottoms. Contact distances between
K2 and each carbon atoms are 3.204(6) and 3.233(5) Å (K2-
C49* and K2-C48*, respectively) for the η2-coordination and
3.259(6)-3.663(7) Å for the η6-coordination, the values of
which are comparable to the typical distance found in the alkali
metal cation-π interactions.31,32 Such coordination implies that
the negative charge in the bottom π-electron system is located
around the C48* and C49* carbon atoms, and most likely at
C49*.33 Further discussion on the carbon skeleton is provided
in Supporting Information (Table S2).
This provides the second example of a single-crystal structure
of a dimer of [60]fullerene radical anion,29 and the third of a
fullerene dimer connected by a single σ-bond.9 The bond length
of the bridging intercage C-C bond of 5a (1.577(11) Å) is
halfway between those of the typical C(sp3)-C(sp3) bond (1.54
Å) and the fullerene interfullerene C-C bond in anionic dimer
[(C60-C60)2-; 1.597(7) Å],29a and comparable to the intercage
bond length in neutral dimer [RC60-C60R; 1.576(6) Å].9 It is
known that the interfullerene single bond in the negatively
charged dimer (C60-C60)2- starts to break at 200-220 K in
crystals.29a The single bond in 5a is thermally stable in the
crystalline state as investigated by an X-ray analysis at 300 K.
The organometallic features of the potassio dimer 5a is next
discussed in some detail (Figure 5), as the crystal structure 5a
provides relevant information on the structure of organopotas-
sium complexes that have not been studied very often.30 In
Figure 5a, we see that the potassium atom K1 is coordinated in
The single crystals of 5a are ESR silent.34 On the other hand,
a black THF solution prepared by dissolving crystals of the
1
dimer 5a is ESR active at room temperature and shows no H
and 13C NMR signals. These observations indicate that 5a
dissociates into a monomeric open-shell radical dianion 4a
(Scheme 3). The similar C-C bond dissociation in solution is
(25) Rapta, P.; Dunsch, L. J. Electroanal. Chem. 2001, 507, 287-292.
(26) Reed, C. A.; Bolskar, R. D. Chem. ReV. 2000, 100, 1075-1120.
(27) Lee, K. H.; Park, S. S.; Suh, Y.; Yamabe, T.; Osawa, E.; Lu¨thi, H. P.;
Gutta, P.; Lee, C. J. Am. Chem. Soc. 2001, 123, 11085-11086.
(28) Segura, J. L.; Martin, N. Chem. Soc. ReV. 2000, 29, 13-25.
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Soc. 2002, 124, 8520-8521. (b) Konarev, D. V.; Khasanov, S. S.;
Vorontsov, I. I.; Saito, G.; Antipin, M. Y.; Otsuka, A.; Lynbovskaya, R.
N. Chem. Commun. 2002, 2548-2549. (c) Konarev, D. V.; Khasanov, S.
S.; Saito, G.; Otsuka, A.; Yoshida, Y.; Lynbovskaya, R. N. J. Am. Chem.
Soc. 2003, 125, 10074-10083.
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2978.
(32) Ma, J. C.; Dougherty, D. A. Chem. ReV. 1997, 97, 1303-1324.
(33) Location of a positive charge affects localization of a negative charge. Cf.
Hoffman, D.; Bauer, W.; Hampel, F.; Hommes, N. J. R. v. E.; Schleyer, P.
v. R.; Otto, P.; Pieper, U.; Stalke, D.; Wright, D. S.; Snaith, R. J. Am.
Chem. Soc. 1994, 116, 528-536.
(30) Jutzi, P.; Burford, N. Chem. ReV. 1999, 99, 969-990.
(34) Single-bonded dimer (C60-C60)
2- is known to be diamagnetic. Cf. ref 26.
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8460 J. AM. CHEM. SOC. VOL. 127, NO. 23, 2005

Synthesis of Useful Organofullerene Polyanions
A R T I C L E S
Figure 6. Absorption spectra of penta(biphenyl)[60]fullerene-polyanions.
Orange line: neutral compound, C60(biphenyl)5H. Dark-red line: monoan-
ion, 1a. Black line: radical dianion, 4a. Green line: trianion, 6a.
Conditions: THF solution (0.45 mM) under argon.
Scheme 4
Figure 5. Schematic drawings of the structure of 5a around potassium
ions. Atoms denoted by asterisks represent crystallographically equivalent
atoms as to the inversion center residing at the middle point between C59
and C59*. (a) A top part. (b) A bottom part. Solid double line < 1.40 Å <
solid-dashed line < 1.43 Å < solid single line. Dashed lines represent
coordination of the potassium ions. Bond lengths (Å): K1-O1 ) 2.642-
(9), K1-O2 ) 2.790(11), K1-O3 ) 2.716(8), K1-C1 ) 3.082(6), K1-
C2 ) 3.266(6), K1-C5 ) 3.619(7), K1-C61 ) 3.260(6), K1-C62 )
3.357(7), K1-C66 ) 3.560(7), K2-O4 ) 2.641(5), K2-O5 ) 2.647(4),
K2-O6 ) 2.766(6), K2-C44 ) 3.500(6), K2-C45 ) 3.663(7), K2-C52
) 3.285(6), K2-C53 ) 3.607 (7), K2-C57 ) 3.259(6), K2-C58 ) 3.392-
(6), K2-C48* ) 3.233(5), K2-C49* ) 3.204(6), C54-C59 ) C54*-C59*
) 1.534(7), C58-C59 ) 1.527(8), C59-C60 ) 1.534(8), C59-C59* )
1.577(11), C48*-C49* ) 1.420(8), C48*-C54* ) 1.402(8). Bond angles
(deg): C58-C59-C60 ) 100.3(4), C58-C59-C54 ) 109.7(5), C60-
C59-C54 ) 108.9(5), C58-C59-C59* ) 111.2(6), C60-C59-C59* )
112.6(6), C54-C59-C59* ) 113.4(5). Sum of three angles around C59
(intracage) ) 318.9°.
6a in THF at 25 °C. Among these four, only 4a exhibits near-
IR bands at λmax ) 771 nm (ꢀ ) 1.09 × 103), 996 nm (ꢀ )
1.08 × 103), and 1125 nm (ꢀ ) 1.65 × 103), characteristic of
an open-shell species with a small band gap.40 The other two
are closed-shell species with a large HOMO-LUMO gap. The
wavelength (λmax ) 1125 nm) is ca. 50 nm lower energy-shifted
•
known for the dimer of neutral radical species RC60 (R )
various alkyl groups).9,28,35,36 The ESR spectrum of 4a in THF
at 290 K exhibited a broad signal that has a g value of 2.003,
which is comparable to the value observed for most organic
radicals and for a free electron (g ) 2.0023), with a peak-to-
peak line width (∆Hpp) of 1.68 mT (Figure S1). The g value is
-•
than that of C60 (λmax ) 1075-1080 nm).39 This difference
is in accord with the intrinsically lower degree of symmetry of
2-
4a (i.e., less orbital degeneracy) than C60
.
much larger than the one observed for C60 (g ) 1.9991),37
-•
Synthesis and Properties of Pentakis(biphenyl)[60]fullerene
Trianion 6. Treatment of the monoanion 1a with 2.5 equiv of
potassium metal in THF at 25 °C for 18 h afforded a dark-
green solution of the pentakis(biphenyl)[60]fullerene-trianion
[K+(thf)n]3[C60(biphenyl)53-] (6a) (Scheme 4). After removal
of THF, an air- and moisture-sensitive black-green powder of
6a was obtained. Similarly, C60Ph5H gave the corresponding
trianion [K+(thf)n]3[C60Ph53-] (6b). Reduction of C60Ar5H (Ar
) biphenyl and Ph) by excess potassium metal in THF also
gave 6a and 6b. Effort to obtain single crystals of 6a and 6b
suitable for X-ray diffraction analysis has so far been unsuc-
cessful because of extreme air sensitivity.
and close to the one observed for C60 (g ) 2.0025),25,38
3-
suggesting that the behavior of the radical dianion 4a is closer
to the fullerene trianion rather than to the fullerene radical anion
because of the interaction between the top cyclopentadienyl
anion and the bottom 50π-electron system.2b
The near-IR absorption is diagnostic of the charge state of
the [60]fullerene anions39 and, in conjunction with the above
data, indicates that 4a exists largely as a monomer in solution.
Figure 6 shows the UV-vis-NIR absorption spectra of neutral
C60(biphenyl)5H, monoanion 1a, radical dianion 4a, and trianion
(35) Morton, J. R.; Preston, K. F. P.; Krusic, J.; Hill, S. A.; Wasserman, E. J.
Am. Chem. Soc. 1992, 114, 5454-5455.
As shown in Figure 6, the trianion 6a absorbs at λmax ) 545
nm (ꢀ ) 5.17 × 103) and 692 nm (ꢀ ) 5.03 × 103). This
(36) Bond dissociation temperature depends on the size of the R group.
(37) Eaton, S. S.; Eaton, G. R. Appl. Magn. Reson. 1996, 11, 155-170.
(38) Boyd, P. D. W.; Bhyrappa, P.; Paul, P.; Stinchcombe, J.; Bolskar, R. D.;
Sun, Y.; Reed, C. A. J. Am. Chem. Soc. 1995, 117, 2907-2914.
(39) (a) Lawson, D. R.; Feldheim, D. L.; Foss, C. A.; Dorhout, P. K.; Elliott,
C. M.; Martin, C. R.; Parkinson, B. J. Electrochem. Soc. 1992, 139, L68-
L71. (b) Khaled, M. M.; Carlin, R. T.; Trulove, P. C.; Eaton, C. R.; Eaton,
S. S. J. Am. Chem. Soc. 1994, 116, 3465-3465.
spectrum is very different from the spectrum observed for
2- 39
C60
,
which shows characteristic near-IR absorptions with
maximum peaks at λmax ) ca. 830 and ca. 952 nm. The reason
-•
(40) C60 exhibiting vibronic absorption at near-IR region. Cf. ref 39.
9
J. AM. CHEM. SOC. VOL. 127, NO. 23, 2005 8461

A R T I C L E S
Scheme 5
Matsuo and Nakamura
2- 43
for this difference can be ascribed to the contribution of the
top cyclopentadienyl anion. We could not find any NMR signals
of 6a and observed a single broad ESR signal of 6a at a
temperature range from 290 to 4.4 K. A small amount of residual
radical dianion 4a as minor component in 6a appears to hamper
the NMR measurement. Interpretation of the NMR and ESR
spectra of 6a remains inconclusive.
being rate limiting for C60
,
we ascribe this efficiency to
greater electron-transfer ability of 6a,b (and likely greater
nucleophilicity of C60Ar5R2-).
The structure determination of 7a,b and 8a,b was not at all
an easy issue because of numerous possibilities as to the position
of the cyclopentadienyl proton and the two R groups. The first
piece of information on symmetry was obtained by derivatization
of 7a into potassium and palladium complexes. Deprotonation
of 7a with 1.2 equiv of KH in THF afforded a single regioisomer
[K+(thf)n][C60(biphenyl)5(CH2Ph)2-] (9) (Scheme 5), which is
C1 symmetric (1H and 13C NMR). Similarly, a deprotonation/
palladation sequence3i afforded Pd[C60(biphenyl)5(CH2Ph)2](π-
methallyl) (10) as a single regioisomer in 90% yield (Scheme
The trianions 6a and 6b are useful nucleophiles (Scheme 5).
Treatment of the black-green THF solution of 6a,b with 3.5-
equiv of a benzylic halide41 (RX; R ) CH2Ph and CHPh2) at
25 °C caused an immediate change of the color into dark red,
and subsequent protonation with aqueous HCl afforded a doubly
alkylated product C60Ar5R2H (7a: Ar ) biphenyl and R ) CH2-
Ph; 7b: Ar ) Ph and R ) CH2Ph; 8a: Ar ) biphenyl and R
) CHPh2; 8b: Ar ) Ph and R ) CHPh2) as a predominant
product42 in 65-75% yield. This chemical reactivity parallels
5), and its H and 13C NMR spectra also indicated the C1
symmetry. These pieces of information limited the range of
structural possibility, which was then reduced into one.
1
that of the fullerene dianion C60 .
2- 6,7,8,11 The reaction may take
Addition of PhCH2MgCl to 7a in THF at 25 °C afforded
C60(biphenyl)5(CH2Ph)3H2 (11) in 82% yield (Scheme 5). The
1H NMR spectrum of 11 exhibited five sets of two C60-H signals
due to the top and bottom hydrogen atoms (i.e., five regioiso-
mers). This as well as the UV-vis spectrum is essentially the
same as that of a known compound C60Me5Ph3H24b possessing
the same regiochemistry as 11. Reaction of 7a with the benzyl
Grignard reagent, followed by an addition of [RuCp(MeCN)3]-
[PF6] gave air-stable Ru[C60(biphenyl)5(CH2Ph)3H]Cp (12) as
a mixture of three regioisomers. It is a dark-green compound
(λmax ) ca. 700 nm). Compound 11 emits orange-red light
(λmax ) 622 nm, Φ ) 1.0%) upon irradiation at λmax ) 365
nm, but ruthenium complex 12 is not luminescent. Then, 11
place in three-stages as proposed for C602- by Fukuzumi;7,8 that
is, electron transfer from 6a,b to the alkyl halide (to generate a
radical dianion 4a,b and an alkyl radical) followed by radical-
radical coupling to give a mono-alkylated product C60Ar5R2-
,
-
and SN2 reaction with the alkyl halide to generates C60Ar5R2
.
2-
We noted that 6a,b is much more reactive than C60 which
requires a 20-100 fold excess of the benzyl halide to obtain a
reasonable reaction rate.7,8,11 The initial electron-transfer step
(41) Reactions with MeI, (Me3Si)2CHCl, and BrCH2CO2Et gave a complex
mixture of many regioisomers and the starting compound 3a,b.
(42) Determination of regioselectivity of the reaction was impossible for
numerous possibilities of nonessential regioisomers: For instance, even
the compounds 7a,b and 8a,b consist of an inseparable mixture of
regioisomers as to the location of the hydrogen atom. With this limitation
in mind, we concluded that the regioselectivity of the alkylation reaction
was very high.
(43) Electron transfer from C602- to RX is the rate-limiting step in the formation
of RC60-. See ref 7.
9
8462 J. AM. CHEM. SOC. VOL. 127, NO. 23, 2005

Synthesis of Useful Organofullerene Polyanions
A R T I C L E S
Table 1. Crystal Data and Structure Analysis Results for 1a and
5a
was doubly deprotonated by 4.5 equiv of KH into a dianion
[K+(thf)n]2[C60(biphenyl)5(CH2Ph)32-] (13). The cyclopentadi-
enyl proton surrounded by the five biphenyl groups was
deprotonated upon addition of the first 1.5 equiv of KH, and
the proton next to the benzyl groups was removed slowly with
the remaining 3 equiv. The compound 13 was Cs symmetric
(1H and 13C NMR). With the above pieces of information, we
concluded that the dialkylation of the trianion 6a,b took place
regioselectively to introduce two benzyl groups on two fullerene
carbon atoms located on the opposite side of the top cyclopen-
tadienide moiety. The two benzyl groups in 7a,b are in a 1,4-
relation to each other in the hexagon. Interestingly, and perhaps
not without reason, this 1,4-substitution is mechanistically
related to the same 1,4-located carbon atoms in 5a; that is, the
C49* atom where anionic charge resides, and the C59* atom
where the C-C bond forms (cf. Figure 5).
1a‚
(THF)3
5a‚(THF)6‚(hexane)
formula
C
156H117KO9
C159H124K2O9
crystal system
space group
R, Rw (I > 2σ(I))
R1, wR2 (all data)
GOF on F2
a, Å
monoclinic
P21/n (No. 14)
0.1044, 0.3048
0.1487, 0.3559
1.286
20.650(3)
27.279(2)
19.546(3)
90
91.404(5)
90
11007(2)
4
triclinic
P1h (No. 2)
0.1174, 0.3077
0.1820, 0.3651
1.226
15.777(3)
17.554(3)
21.761(4)
81.860(9)
72.851(9)
77.342(9)
5600(2)
b, Å
c, Å
R, deg
â, deg
γ, deg
V, Å3
Z
2
T, K
153(2)
153(2)
crystal size, mm
D
0.85, 0.65, 0.20
1.312
0.54, 0.26, 0.22
1.338
calcd, g/cm3
In conclusion, selective reduction of organofullerene com-
pounds with carefully chosen reduction agents affords well-
defined, synthetically useful organofullerene polyanions. The
investigation has given basic information to the chemistry of
reduced penta(aryl)fullerene molecules that have so far been
generated as transient species and studied only through elec-
trochemical measurements. The study not only elucidated the
properties and reactivities of anion and polyanions of the
organofullerenes about which rather little has so far been known,
but also provided new synthetic entries to functionalized
fullerenes. The reduction methodology has provided a variety
of new structures such as dimer-, hepta- and octa-alkylated
compounds such as 5 and 7-13. Given the new conjugation
networks4,44 and the organometallic ligand systems3 found in
7-13 (such as luminescent fused corannulene), we expect that
the alkylation strategies based on the reduction chemistry is
complementary to the organocopper routes,2 and will provide
useful possibilities for material science applications.1,19,20,45 The
selective reduction methodology will also find use in polyfunc-
tionalization of carbon clusters other than [60]fullerene.
2θmin, 2θmax, deg
4.12, 51.72
16563
9667
4.34, 51.9
16858
9159
no. refl. measured (unique)
no. refl. measured (I > 2σ(I))
no. parameters
1486
1524
trometers, respectively. When THF-d8 and chloroform-d were used as
solvent, spectra were referenced to residual solvent protons in the H
1
NMR spectra (3.58 and 7.26 ppm) and to solvent carbons in the 13C
NMR spectra (67.4 and 77.0 ppm). Mass spectra were measured on
Shimadzu LCMS-QP8000 and Waters ZQ2000 LC-mass spectrometer.
High-resolution mass spectra were measured on a JEOL JMS-T100LC
APCI/ESI-TOF mass spectrometer.
Electrochemical Measurements. Cyclic voltammetry (CV) was
performed using a BAS CV-50W voltammetric analyzer and three-
electrode cell with a glassy carbon working electrode and a platinum
wire counter electrode. All potentials were recorded against an Ag/
Ag+ reference electrode and corrected against Fc/Fc+. CV was measured
at a scan rate of 100 mV/s.
ESR Measurement. ESR spectra of 4a and 6a were recorded on a
JEOL continuous wave X-band spectrometer, JES-RE2X, equipped with
a helium flow-temperature controller. All measurements were performed
by using sealed ESR tubes. THF solution samples were measured using
2-mm quartz ESR tubes.
Experimental Section
UV-vis-NIR Measurement. UV-vis-NIR spectra of 4a and 6a
were recorded on a HITACHI U3500 spectrometer. All solutions were
prepared in spectrograde THF that was distilled from Na/K alloy by
trap-to-trap distillation prior to the measurements.
General. All manipulations were carried out under argon using
standard Schlenk techniques. THF, THF-d8, and hexane were dried over
Na/K alloy and purified by trap-to-trap distillation before use.
Chloroform-d was used as received. The water content of the solvent
was determined with a Karl Fischer Moisture Titrator (MK-210, Kyoto
Electronics Company) to be less than 20 ppm for THF and THF-d8.
Penta(phenyl)[60]fullerene and penta(biphenyl)[60]fullerene were pre-
pared according to the literature.2a,d,19 Benzyl bromide was purchased
from Tokyo Kasei Kogyo Co., Ltd. and was distilled under reduced
pressure. Chemical yields of the potassium complexes were calculated
on a postulate that three THF molecules coordinate to one potassium
atom.
X-ray Crystallographic Analysis. Single crystals of 1a and 5a
suitable for X-ray diffraction studies were grown and subjected to data
collection. The data sets were collected on a MacScience DIP2030
Imaging Plate diffractometer using Mo KR (graphite monochromated,
λ ) 0.71069 Å) radiation. Crystal data and data statistics are
summarized in Table 1. The structure of 1a and 5a was solved by the
directed method (SIR97).46 The positional and thermal parameters of
non-hydrogen atoms were refined anisotropically on F2 by the full-
matrix least-squares method, using SHELXL-97.47 Hydrogen atoms
were placed at calculated positions and refined “riding” on their
corresponding carbon atoms. In the subsequent refinement, the function
HPLC analyses for reactions affording air-stable neutral compounds
were performed on Shimadzu LC-10A system equipped with SPD-
M10A diode array detector. Preparative HPLC separations were
performed by use of Buckyprep column (Nacalai Tesque Co., 20 mm
× 250 mm) using toluene/2-propanol (5/5) or toluene/hexane (5/5) as
∑ω(Fo - Fc2)2 was minimized, where |Fo| and |Fc| are the observed
2
and calculated structure factor amplitudes, respectively. The agreement
1
eluent. All H (400 MHz, 500 MHz) and 13C (100 MHz, 125 MHz)
indices are defined as R1 ) ∑ (||Fo| - |Fc||)/∑|Fo| and wR2 ) [∑ω
(Fo2 - Fc2)2/∑ (ωFo )]1/2 CCDC No. 271756 (1a) and No. 271957 (5a).
4
NMR spectra were recorded on JEOL ECX400 and ECA500 spec-
(44) (a) Randic´, M. Chem. ReV. 2003, 103, 3449-3606. (b) Scott, L. T. Angew.
Chem., Int. Ed. 2003, 42, 4133-4135. (c) Hoffmann, R. Int. J. Philos.
Chem. 2003, 9, 7-10. (d) Matsuo, Y.; Tahara, K.; Nakamura, E. Org. Lett.
2003, 5, 3181-3184.
(45) Isobe, H.; Mashima, H.; Yorimitsu, H.; Nakamura, E. Org. Lett. 2003, 5,
4461-4463.
(46) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G. L.; Giacovazzo,
C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, R. J. Appl.
Crystallogr. 1999, 32, 115-119.
(47) Sheldrick, G. M. Programs for Crystal Structure Analysis, Release 97-2;
Institut fu¨r Anorganische Chemie der Universita¨t, Tammanstrasse 4, D-3400
Go¨tingen, Germany, 1998.
9
J. AM. CHEM. SOC. VOL. 127, NO. 23, 2005 8463

A R T I C L E S
Matsuo and Nakamura
Preparation of [K(thf)n][C60(C6H4-Ph-4)5] (1a). A Schlenk tube
was charged with C60(biphenyl)5H (500 mg, 0.336 mmol) and potassium
hydride (40 mg, 1.01 mmol) which was washed with dried hexane.
Addition of THF (60 mL) to the Schlenk tube at 25 °C gave a dark-
red solution with evolving H2 gas. After stirring for 20 min at 25 °C,
the reaction mixture was transferred to a centrifugation tube via cannula.
The dark-red solution was separated from potassium hydride by
centrifugation and transferred to a Schlenk tube. Solvent was removed
under reduced pressure, and the dark-red microcrystalline solid was
washed with dried hexane to obtain 1a (568 mg, 0.326 mmol, 97%
(500 mg, 0.452 mmol) by using potassium/mercury amalgam gave 6b
(809 mg, 0.432 mmol, 96% yield).
Preparation of C60(biphenyl)5(CH2Ph)2H (7a). Method A. To a
black-green solution of 6a (300 mg, 0.133 mmol) in THF (10 mL)
was added benzyl bromide (79.7 mg, 0.466 mmol) at 25 °C. The color
of the solution immediately changed to dark red. After stirring for 2
min, aqueous HCl (1 N, 0.2 mL) was dropped into the solution.
Methanol (60 mL) was added to the reaction mixture to precipitate red
microcrystals, which were collected by filtration. The crystalline crude
solid was purified by silica gel column chromatography using eluent
CS2/toluene (from 10/0 to 8/2). The intense red band following the
yellow band was collected, and the solution was concentrated under
reduced pressure. Methanol was added to the concentrated solution to
give a red crystalline precipitate, which was collected by filtration and
washed with methanol to afford 7a (167 mg, 0.100 mmol, 75% yield)
as an inseparable mixture of five regioisomers as to the position of the
hydrogen atom. The NMR and high-resolution APCI-TOF MS spectra
were measured for the mixture. 1H NMR (CDCl3, 500 MHz): δ 3.35-
4.09 (m, 4H, CH2Ph), 5.33, 5.36, 5.37, 5.42, and 5.46 (s × 5, 1H,
C60-H), 7.27-8.05 (m, 55H, aromatic protons). 13C{1H} NMR (CDCl3,
125 MHz): δ 47.0-47.8 (CH2Ph), 58.54-61.25 (C(sp3)-H, C(sp3)-
Ph, and C(sp3)-CH2), 127.01-154.89 (aromatic carbons). HRMS
(APCI-TOF, negative) m/z calcd for C134H59 [M - H]- 1668.4650,
found: 1668.4645. Anal. Calcd for C134H60: C, 96.38; H, 3.62.
Found: C, 96.21; H, 3.59.
Method B. C60(biphenyl)5H (1.00 g, 0.672 mmol) and potassium
metal (263 mg, 6.72 mmol) were placed in a Schlenk tube to which
was added THF (40 mL). Hydrogen gas evolved, and the color of the
solution changed to dark red after stirring for 4 h at 25 °C. Further
stirring for 18 h gave a dark-green solution which was transferred to
an another Schlenk tube via cannula. To this solution was added benzyl
bromide (402 mg, 2.35 mmol) at 25 °C. The color of the solution
changed from dark green to dark red. After stirring for 2 min, aqueous
HCl (1 N, 1.0 mL) and methanol (200 mL) were added to obtain crude
microcrystal, which was subjected to purification as with method A
described above. The title compound (751 mg, 0.450 mmol, 67% yield)
was obtained as red crystals.
1
yield). H NMR (THF-d8, 500 MHz): δ 7.15 (t, Ph, 5H), 7.27 (t, Ph,
10H), 7.36 (d, C6H4, 10H), 7.51 (d, Ph, 10H), 8.04 (d, C6H4, 10H).
13C{1H} NMR (THF-d8, 125 MHz): δ 62.18 (C60(sp3), 5C), 126.90
(biphenyl, 10C), 127.27 (biphenyl, 5C), 127.71 (biphenyl, 10C), 128.84
(biphenyl, 5C), 129.24 (biphenyl, 10C), 129.84 (biphenyl, 10C), 139.32
(biphenyl, 5C), 142.50 (biphenyl, 5C), 143.32 (C60, 10C), 145.62 (C60,
5C), 146.65 (C60, 5C), 147.41 (C60, 10C), 149.38 (C60, 5C), 149.41
(C60, 10C), 159.88 (C60, 10C).
Preparation of [K(thf)n]2[C60(C6H4-Ph-4)5] (4a). Method A. To a
potassium/mercury amalgam (1.0 wt %; K: 50 mg, 1.3 mmol; Hg:
5.0 g) was added a solution of 1a (500 mg, 0.287 mmol) in THF (40
mL) at 25 °C. After stirring for 24 h at 25 °C, the reaction mixture
was transferred to a centrifugation tube via cannula. The dark-brown
solution was separated from the mercury amalgam by centrifugation.
The supernatant solution was transferred to a Schlenk tube, and solvent
was removed under reduced pressure. The resulting black microcrys-
talline solid was washed with dried hexane to obtain 4a (550 mg, 0.275
mmol, 96% yield). Air-sensitive open-shell compound 4a was char-
acterized by the ESR, UV-vis-NIR spectroscopy and by the X-ray
crystallography.
Method B. Alternatively, the title compound could be directly
prepared by the treatment of C60(biphenyl)5H (500 mg, 0.336 mmol)
and potassium/mercury amalgam (1.0 wt %; K: 50 mg, 1.3 mmol;
Hg: 5.0 g). The same preparation procedure described above was
performed to obtain 4a (638 mg, 0.319 mmol, 95% yield).
Preparation of [K(thf)n]2[C60Ph5] (4b). Method A. Starting material
[K(thf)n][C60Ph5] (1b) was prepared according to a previous paper.2
The same potassium/mercury amalgam reduction was performed to
obtain 4b. Complex 4b (569 mg, 0.352 mmol, 96% yield) was derived
from 1b (500 mg, 0.367 mmol). The title compound 4b is also an air-
sensitive and ESR-active compound.
Preparation of C60Ph5(CH2Ph)2H (7b). The procedure described
for 7a was performed to obtain 7b. Compound 7b (890 mg, 0.690
mmol, 69% yield) was synthesized from C60Ph5H (1.11 g, 1.00 mmol),
benzyl bromide (599 mg, 3.50 mmol), potassium metal (391 mg, 10.0
mmol), and THF (50 mL).
1H NMR (CDCl3, 400 MHz): δ 3.3-3.6
Method B. The procedure described for 4a was performed to obtain
4b. Reduction of C60Ph5H (500 mg, 0.452 mmol) by using potassium/
mercury amalgam (1.0 wt %; K: 50 mg, 1.3 mmol; Hg: 5.0 g) gave
4b (711 mg, 0.440 mmol, 97% yield).
(m, 2H, CHHPh), 3.8-4.1 (m, 2H, CHHPh), 5.20, 5.22, 5.24, 5.29,
and 5.33 (s × 5, 1H, C60-H), 7.0-8.0 (m, 35H, Ph). 13C{1H} NMR
3
(CDCl
3, 100 MHz): δ 47.3-47.8 (CH2Ph), 58.4-60.0 (C(sp )-Ph and
C(sp3)-CH2), 61.82, 62.35, 62.82, 63.43, and 63.72 (C(sp3)-H), 126.7-
129.0 (Ph), 131.0-131.4 (Ph), 136.8-136.9 (ipso-Ph (CH2Ph)), 137.5-
137.6 (ipso-Ph (CH2Ph)), 139.7-164.1 (C60(sp2) and ipso-Ph (C60-
Ph)). HRMS (APCI-TOF, negative) m/z calcd for C104H39 [M - H]-
1288.3085, found: 1288.3087. Anal. Calcd for C104H40: C, 96.87; H,
3.13. Found: C, 96.70; H, 3.03.
Preparation of C60(biphenyl)5(CHPh2)2H (8a). The procedure
described for 7a was performed to obtain 8a. Compound 8a (174 mg,
0.0955 mmol, 71% yield) was synthesized from C60(biphenyl)5H (200
mg, 0.134 mmol), diphenylmethyl bromide (116 mg, 0.470 mmol),
potassium metal (52.0 mg, 1.34 mmol), and THF (20 mL).1H NMR
(CDCl3, 400 MHz): δ 5.38-5.83 (m, 3H, C60-H and CHPh2), 6.80-
8.33 (m, 65H, Ph). 13C{1H} NMR (CDCl3, 100 MHz): δ 57.3-66.4
(sp3 C(C60)-Ph, C(C60)-CH, C(C60)-H, and CHPh2), 126.1-164.3 (sp2
carbon of C60 and aromatic carbons). HRMS (APCI-TOF, negative)
m/z calcd for C146H67 [M - H]- 1820.5276, found: 1820.5267. Anal.
Calcd for C146H68: C, 96.24; H, 3.76. Found: C, 96.02; H, 3.64.
Preparation of C60Ph5(CHPh2)2H (8b). The procedure described
for 7a was performed to obtain 8b. Compound 8b (187 mg, 0.130
mmol, 72% yield) was synthesized from C60Ph5H (200 mg, 0.181
mmol), diphenylmethyl bromide (157 mg, 0.634 mmol), potassium
Preparation of [K(thf)n]3[C60(C6H4-Ph-4)5] (6a). Method A. Mi-
crocrystalline solids of 1a (500 mg, 0.287 mmol) and potassium metal
(28.0 mg, 0.717 mmol) were placed in a Schlenk tube, and THF (40
mL) was added at 25 °C to start the reduction. After stirring for 18 h
at this temperature, a dark-green solution of 6a was obtained. THF
was removed under reduced pressure, and the resulting dark-green solid
(pyrophoric) was washed with dry hexane to obtain 6a (615 mg, 0.273
mmol, 95%). Characterization of the title compound was performed
by UV-vis-NIR and ESR spectroscopy.
Method B. An alternative procedure for the preparation of 6a is
reduction of C60(biphenyl)5H. Treatment of microcrystalline solids of
C60(biphenyl)5H (500 mg, 0.336 mmol) and potassium metal (112 mg,
2.86 mmol) in THF (40 mL) gave the same dark-green solution. The
solution was transferred to a centrifugation tube via cannula under
argon, and insoluble materials were removed by centrifugation. Drying
under reduced pressure and washing with hexane afforded the air- and
moisture-sensitive dark-green powder 6b (725 mg, 0.322 mmol, 96%).
Preparation of [K(thf)n]3[C60Ph5] (6b). The procedures described
for 6a were performed to obtain 6b. Reduction of 1b (500 mg, 0.367
mmol) by using potassium metal (35.9 mg, 0.918 mmol) afforded 6b
(651 mg, 0.348 mmol, 95% yield). Alternatively, reduction of C60Ph5H
9
8464 J. AM. CHEM. SOC. VOL. 127, NO. 23, 2005

Synthesis of Useful Organofullerene Polyanions
A R T I C L E S
metal (71.0 mg, 1.81 mmol), and THF (20 mL).1H NMR (CDCl3, 400
MHz): δ 5.21-5.32 (s × 10, 2H, CHPh2), 5.67, 5.67, 5.69, 5.70, and
5.71 (s × 5, 1H, C60-H), 6.82-8.45 (m, 45H, Ph). 13C{1H} NMR
(CDCl3, 100 MHz): δ 57.5-66.1 (sp3 C(C60)-Ph, C(C60)-CH, C(C60)-
H, and CHPh2), 126.5-158.0 (Ph). HRMS (APCI-TOF, negative) m/z
calcd for C116H47 [M - H]- 1440.3711, found: 1440.3713. Anal. Calcd
for C116H48: C, 96.64; H, 3.36. Found: C, 96.51; H, 3.32.
and fullerene sp2 carbons). HRMS (APCI-TOF, positive) m/z calcd for
C
Pd: C, 90.55; H, 3.63. Found: C, 90.40; H, 3.49.
138H66Pd [M]+ 1828.4235, found: 1828.4238. Anal. Calcd for C138H66-
Preparation of C60(biphenyl)5(CH2Ph)3H2 (11). To a solution of
7a (200 mg, 0.120 mmol) in THF (20 mL) was added a THF solution
of PhCH2MgCl (0.70 M, 0.34 mL, 0.24 mmol) at 25 °C. After stirring
for 10 min at 25 °C, the solution was quenched with saturated NH4Cl
aqueous solution (0.05 mL). Solvent was removed under reduced
pressure, and the resulting crude solid was purified by silica gel column
chromatography using CS2/toluene (from 10/0 to 7/3) eluent. The orange
band was collected, and the solvent was evaporated to a small volume
under reduced pressure. Methanol was added to the concentrated
solution to give orange-yellow microcrystals 11 (173 mg, 0.098 mmol,
82% yield) as an inseparable mixture of five regioisomers as to the
position of the hydrogen atom. The NMR and high-resolution APCI-
Preparation of [K(thf)n][C60(biphenyl)5(CH2Ph)2] (9). Compound
7a (100 mg, 0.060 mmol) and pre-washed KH (3.0 mg, 0.072 mmol)
were placed in a Schlenk tube, and then THF (10 mL) was added at 25
°C. Hydrogen gas evolved, and the color of the solution changed from
red brown to dark red. After stirring for 30 min at 25 °C, insoluble
material was removed by centrifugation. Removal of a solvent and
washing with dry hexane afforded air-sensitive dark-red powder 9 (110
1
mg, 0.057 mmol, 95% yield). H NMR (THF-d8, 400 MHz): δ 3.49
1
2
2
TOF MS spectra were measured for the mixture. H NMR (CDCl3,
(d, JH-H ) 12.8 Hz, 1H, PhCHH), 3.56 (d, JH-H ) 12.8 Hz, 1H,
2
2
500 MHz): δ 2.90-3.50 (m, 6H, CH2Ph), 4.83, 4.84, 4.87, 4.88, and
4.91 (s × 5, 1H, C60-H bottom indene moiety), 5.35, 5.35, 5.47, 5.51,
and 5.57 (s × 5, 1H, C60-H top cyclopentadiene moiety), 7.15-8.17
(m, 60H, aryl groups). 13C{1H} NMR (CDCl3, 125 MHz): δ 44.45-
49.90 (CH2Ph), 56.05-62.84 (sp3 carbon atoms of C60), 127.01-157.39
(aryl groups). HRMS (APCI-TOF, negative) m/z calcd for C141H67 [M
- H]- 1760.5276, found: 1760.5279. Anal. Calcd for C141H68: C,
96.11; H, 3.89. Found: C, 95.98; H, 3.83.
PhCHH), 3.98 (d, JH-H ) 12.8 Hz, 1H, PhCHH), 4.03 (d, JH-H
)
12.8 Hz, 1H, PhCHH), 7.1-7.6 (m, 45H, Ph and C6H4), 7.82 (d, 3JH-H
) 7.6 Hz, 2H, o-C6H4), 7.90 (d, 3JH-H ) 7.6 Hz, 2H, o-C6H4), 7.97 (d,
3JH-H ) 7.6 Hz, 2H, o-C6H4), 8.20 (d, JH-H ) 7.6 Hz, 2H, o-C6H4),
3
8.25 (d, JH-H ) 7.6 Hz, 2H, o-C6H4). 13C{1H} NMR (THF-d8, 100
3
MHz): δ 47.01 (PhCH2), 48.86 (PhCH2), 59.43 (C(sp3)-CH2), 60.72
(C(sp3)-CH2), 61.84 (C(sp3)-C6H4), 61.85 (C(sp3)-C6H4), 62.22 (C(sp3)-
C6H4), 62.23 (C(sp3)-C6H4), 62.64 (C(sp3)-C6H4), 126.01, 126.65,
126.70, 126.83, 127.15, 127.37, 127.64, 127.66, 127.71, 128.58, 128.72,
128.84, 129.18, 129.23, 129.65, 129.76, 129.82, 130.02, 130.17, 132.14,
132.37, 138.06, 138.88, 138.93, 139.03, 139.08, 139.48, 139.69, 140.00,
141.55, 142.39, 142.57,142.61, 142.76, 143.25, 143.49, 143.75, 143.87,
144.36, 144.98, 145.75, 145.98, 146.25, 146.35, 146.46, 147.21, 147.45,
147.81, 148.26, 148.52, 148.99, 149.48, 149.72, 150.39, 151.34, 151.67,
152.25, 152.41, 153.01, 153.31, 154.21, 155.70, 156.78, 158.33, 159.22,
160.31, 161.53, 162.27, 162.83, and 163.29 (sp2 carbon of C60 and
aromatic carbons).
Preparation of Ru[C60(biphenyl)5(CH2Ph)3H]Cp (12). To a solu-
tion of 7a (50 mg, 0.030 mmol) in THF (5.0 mL) was added a THF
solution of PhCH2MgCl (0.70 M, 0.085 mL, 0.060 mmol) at 25 °C.
After stirring for 10 min at 25 °C, [RuCp(MeCN)3][PF6] (30 mg, 0.070
mmol) was added to the solution. The resulting red solution was stirred
for 5 min at 25 °C, and the solution was quenched with saturated NH4-
Cl aqueous solution (0.10 mL). Insoluble products were separated
through a pad of silica gel (eluent: toluene) and purified by silica gel
column chromatography using CS2/toluene (from 10/0 to 7/3) eluent.
The brown-green band was collected, and the solvent was evaporated
to a small volume under reduced pressure. Methanol was added to the
concentrated solution to give orange-yellow microcrystals 12 (42.6 mg,
0.0221 mmol, 74% yield) as an inseparable mixture of three regioiso-
mers as to the position of the hydrogen atom. The NMR and high-
Preparation of Pd[C60(biphenyl)5(CH2Ph)2](π-methallyl) (10). A
THF solution of tBuOK (1.0 M, 0.033 mL, 0.033 mmol) was added to
a solution of 7a (50 mg, 0.030 mmol) in THF (5.0 mL). The color of
the solution changed from red to dark red, indicating formation of 9.
After stirring for 10 min at 25 °C, [Pd(π-methallyl)Cl]2 (3.6 mg, 0.018
mmol) was added to the solution. The resulting red solution was stirred
for 5 min at 25 °C, and the solution was quenched with saturated NH4-
Cl aqueous solution (0.10 mL). Insoluble products were separated
through a pad of silica gel (eluent: toluene), and purification by HPLC
(Nacalai Tesque, Buckyprep, 20 × 250 mm, eluent: toluene/hexane
) 4/6) was performed. The fractions containing 10 were collected and
evaporated to a small volume, and precipitation with methanol afforded
10 (49 mg, 0.027 mmol, 90% yield). 1H NMR (CDCl3, 500 MHz): δ
1.68 (s, Me, 3H), 2.04 (s, CH2(anti), 2H), 3.08 (s, CH2(syn), 2H), 3.37
1
resolution APCI-TOF MS spectra were measured for the mixture. H
NMR (CDCl3, 500 MHz): δ 3.93-4.25 (m, 6H, CH2Ph), 5.16, 5.18,
and 5.20 (s × 3, 5H, Cp), 5.46, 5.55, and 5.63 (s × 3, 1H, C60-H top
cyclopentadiene moiety), 7.27-8.14 (m, 60H, aryl groups). 13C{1H}
NMR (CDCl3, 125 MHz): δ 52.98-56.02 (CH2Ph), 58.75-61.69 (sp3
carbon atoms of C60), 71.75, 71.66, and 71.67 (Cp), 98.65-98.72
(fullerene indenyl moiety), 126.98-157.20 (aryl groups). HRMS
(APCI-TOF, negative) m/z calcd for C146H71Ru [M - H]- 1925.4640,
found: 1925.4638. Anal. Calcd for C146H72Ru: C, 90.99; H, 3.77.
Found: C, 90.88; H, 3.72.
2
2
(d, JH-H ) 13.0 Hz, 1H, PhCHH), 3.45 (d, JH-H ) 13.0 Hz, 1H,
2
2
PhCHH), 3.91 (d, JH-H ) 12.7 Hz, 1H, PhCHH), 3.99 (d, JH-H
)
Preparation of [K(thf)n]2[C60(biphenyl)5(CH2Ph)3] (13). Compound
11 (20 mg, 0.011 mmol) and pre-washed KH (1.4 mg, 0.035 mmol)
were placed in a NMR tube and then was added THF-d8 (0.5 mL) by
trap-to-trap distillation. After evolution of hydrogen gas became
complete, the NMR tube was sealed under reduced pressure. This
12.7 Hz, 1H, PhCHH), 7.1-8.1 (m, 55H, Ph and C6H4). 13C{1H} NMR
(CDCl3, 125 MHz): δ 21.60 (methallyl Me), 47.38 (CH2Ph), 47.85
(CH2Ph), 57.65 (methallyl CH2), 58.51 (C(sp3)-C6H4), 58.71 (C(sp3)-
C6H4), 58.81 (C(sp3)-CH2), 59.00 (C(sp3)-C6H4), 59.13 (C(sp3)-C6H4),
59.25 (C(sp3)-C6H4), 59.92 (C(sp3)-CH2), 115.93 (methallyl CMe),
119.45 (fullerene cyclopentadienyl moiety), 120.05 (FCp), 120.38
(FCp), 120.52 (FCp), 120.77 (FCp), 126.35, 126.38, 126.42, 126.51,
126.53, 126.98, 127.01, 127.06, 127.40, 127.44, 128.10, 128.21, 128.38,
128.51, 128.65, 128.73, 128.76, 128.78, 128.82, 128.86, 129.01, 131.15,
131.44, 132.23, 135.72, 136.34, 136.86, 137.63, 137.84, 139.82, 139.92,
139.99, 140.01, 140.09, 140.32, 140.34, 140.37, 140.41, 141.64, 141.89,
142.86, 143.25, 143.59, 143.68, 143.70, 143.81, 143.87, 144.01, 144.16,
144.45, 144.58, 144.62, 144.72, 145.59, 145.67, 145.84, 146.22, 146.43,
146.96, 147.66, 147.69, 147.74, 147.86, 148.28, 148.82, 149.11, 149.32,
149.41, 149.63, 149.69,150.55, 150.93, 151.08, 151.68, 152.15, 152.21,
152.72, 152.81, 153.01, 153.75, 153.78, 154.71, 154.85, 155.05, 155.83,
158.85, 159.77, 160.68, and 164.37 (aromatic Ph and C6H4 carbons
1
1
sample was subjected to measurement of the H NMR spectrum. H
NMR (THF-d8, 500 MHz): δ 3.39 (d, 2JH-H ) 12.6 Hz, 2H, CH2Ph),
3.60 (d, JH-H ) 12.6 Hz, 2H, CH2Ph), 3.76 (s, 2H, CH2Ph), 7.11-
2
7.55 (m, 46H, Ar), 7.60 (d, 2H, Ar), 7.87 (d, 2H, Ar), 8.03 (d, 4H,
Ar), 8.12 (d, 4H, Ar), 8.36 (d, 2H, Ar). 13C{1H} NMR (THF-d8, 125
MHz): δ 52.42 (CH2Ph), 52.65 (CH2Ph), 58.85 (sp3 C(C60)-CH2), 60.25
(sp3 C(C60)-CH2), 60.88 (sp3 C(C60)-Ar), 61.48 (sp3 C(C60)-Ar), 61.67
(sp3 C(C60)-Ar), 122.96, 123.62, 125.89, 126.16, 126.29, 126.57, 126.65,
126.82, 126.94, 127.14, 127.21, 127.44, 127.55, 127.62, 127.64, 127.86,
128.03, 128.42, 129.26, 129.30, 129.36, 130.01, 130.13, 130.36, 132.08,
132.15, 132.66, 137.76, 138.52, 138.59, 138.75, 139.85, 140.97, 141.52,
141.93, 142.75, 142.77, 144.21, 144.24, 144.54, 146.13, 146.18, 146.57,
147.09, 147.74, 148.29, 148.59, 148.75, 149.60, 150.47, 150.67, 150.85,
9
J. AM. CHEM. SOC. VOL. 127, NO. 23, 2005 8465

A R T I C L E S
Matsuo and Nakamura
153.06, 156.49, 157.38, 159.37, 159.46, and 162.34 (sp2 carbons of
the C60 skeleton and aryl carbons).
Acknowledgment. The present research was supported by a
Grant-in-Aid for Specially Promoted Research and the 21st
Century COE Programs for Frontiers in Fundamental Chemistry.
We thank Frontier Carbon Corporation for a generous supply
of [60]fullerene.
When 1.2 equiv of KH was used for this reaction, a monodeproto-
nated product [K+(thf)n][C60(biphenyl)5(CH2Ph)3H-] was obtained.
Deprotonation occurred at the top cyclopentadiene moiety, and thus
1
the hydrogen atom on the bottom indene moiety remained. H NMR
2
(THF-d8, 500 MHz): δ 2.89 (d, JH-H ) 12.9 Hz, 2H, CH1 Ph), 3.08
2
Supporting Information Available: Description for X-ray
structure as well as CIF files of 1a and 5a, and ESR spectrum
of 4a. This material is available free of charge via the Internet
at http://pubs.acs.org.
(d, JH-H ) 12.9 Hz, 2H, CH1 Ph), 3.25 (d, JH-H ) 12.8 Hz, 2H,
2
2
2
CH2 Ph), 3.34 (d, JH-H ) 12.6 Hz, 2H, CH3 Ph), 3.44 (d, JH-H
)
2
2
2
2
2
12.6 Hz, 2H, CH3 Ph), 3.45 (d, JH-H ) 12.8 Hz, 2H, CH2 Ph), 4.85
2
2
(s, 1H, C60-H), 7.10-7.56 (m, 46H, Ar), 7.61 (d, 2H, Ar), 7.71 (d, 2H,
Ar), 7.74 (d, 2H, Ar), 7.74 (d, 2H, Ar), 8.09 (d, 2H, Ar), 8.11 (d, 2H,
Ar), 8.37 (d, 2H, Ar).
JA050318X
9
8466 J. AM. CHEM. SOC. VOL. 127, NO. 23, 2005