Synthesis and derivatization of iridium(I) and iridium(III) pentamethyl[60]fullerene complexes

Article abstract of DOI:10.1021/om049333l

An iridium(I) pentamethyl[60]fullerene complex, Ir(η⁵-C ₆₀Me₅)(CO)₂ (1), was prepared by the reaction of KC(C₆₀Me₅) with [IrCl(CO)₂]₂ in an acetonitrile/THF solution. Oxidation of the indium atom of 1 by I ₂ successfully proceeded to afford an iridium(III) complex, Ir(η⁵C₆₀Me₅)I₂(CO) (2), in 80% yield. Ligand exchange reactions of 1 took place to give phosphine complexes, Ir(η⁵-C₆₀Me₅)(CO)(PEt₃) (3b) and Ir(η⁵-C₆₀Me₅)(CO)(PEt₃) (3c), in 60% and 35% yields, respectively. Similarly, the Ir(I) phosphine complex Ir(η⁵-C₆₀Me₅)(CO)(PMe₃) (3a) was also obtained by the reaction of 2 with PMe₃ in 92% yield via reduction of the complex, while treatment of 2 with XylNC (Xyl = 2,6-dimethylphenyl isocyanide) gave another Ir(III) complex, Ir(η ⁵-C₆₀Me₅)I₂(XylNC) (4), in 93% yield. MeMgBr and PhCCMgBr reacted with 2 to give alkyl and alkynyl complexes, Ir(η⁵-C₆₀Me₅)Me₂(CO) (5) and Ir(η⁵-C₆₀Me₅)(CCPh)₂(CO) (6), in 60% and 81% yields, respectively. The molecular structures of 1,2, and 3a were determined by X-ray crystallographic analysis. Cyclic voltammetric investigation of 1 and 2 revealed the electrochemical properties of the Ir(I) and Ir(III) complexes. Complex 1 showed three reversible one-electron-reduction waves in the cathodic scan, and one reversible two-electron-oxidation wave in the anodic scan, while the complex 2 exhibited two-electron reduction of the metal center and one-electron reduction of the fullerene part. The isolated diiodide complex 2 will be a useful starting material for the synthesis of various metal fullerene complexes.

Full text of DOI:10.1021/om049333l

Organometallics 2005, 24, 89-95
89
Synthesis and Derivatization of Iridium(I) and
Iridium(III) Pentamethyl[60]fullerene Complexes
Yutaka Matsuo, Akihiko Iwashita, and Eiichi Nakamura*
Department of Chemistry, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
Received August 26, 2004
An iridium(I) pentamethyl[60]fullerene complex, Ir(η5-C60Me5)(CO)2 (1), was prepared by
the reaction of K(C60Me5) with [IrCl(CO)2]2 in an acetonitrile/THF solution. Oxidation of
the iridium atom of 1 by I2 successfully proceeded to afford an iridium(III) complex, Ir(η5-
C60Me5)I2(CO) (2), in 80% yield. Ligand exchange reactions of 1 took place to give phosphine
complexes, Ir(η5-C60Me5)(CO)(PEt3) (3b) and Ir(η5-C60Me5)(CO)(PPh3) (3c), in 60% and 35%
yields, respectively. Similarly, the Ir(I) phosphine complex Ir(η5-C60Me5)(CO)(PMe3) (3a) was
also obtained by the reaction of 2 with PMe3 in 92% yield via reduction of the complex,
while treatment of 2 with XylNC (Xyl ) 2,6-dimethylphenyl isocyanide) gave another Ir-
(III) complex, Ir(η5-C60Me5)I2(XylNC) (4), in 93% yield. MeMgBr and PhCCMgBr reacted
with 2 to give alkyl and alkynyl complexes, Ir(η5-C60Me5)Me2(CO) (5) and Ir(η5-C60Me5)-
(CCPh)2(CO) (6), in 60% and 81% yields, respectively. The molecular structures of 1, 2, and
3a were determined by X-ray crystallographic analysis. Cyclic voltammetric investigation
of 1 and 2 revealed the electrochemical properties of the Ir(I) and Ir(III) complexes. Complex
1 showed three reversible one-electron-reduction waves in the cathodic scan, and one
reversible two-electron-oxidation wave in the anodic scan, while the complex 2 exhibited
two-electron reduction of the metal center and one-electron reduction of the fullerene part.
The isolated diiodide complex 2 will be a useful starting material for the synthesis of various
metal fullerene complexes.
Introduction
which is fundamentally unsuitable for bonding with a
metal atom on the surface of the spherical molecules.7
The η2-fullerene ligand tends to be displaced in the
course of ligand exchange reactions.3
Incorporation of transition metals into the carbon
network of fullerene and carbon nanotubes1 creates a
rich world of chemistry through synergy of the metallic
and carbonaceous components. Immediately after the
start of the mass production of [60]fullerene,2 efforts to
synthesize transition-metal η2-fullerene complexes and
to examine their reactivities started.3 However, the
chemistry of exohedral metal η2-fullerene complexes has
suffered from the difficulty of chemical derivatization
of the complexes. In particular, the electron-deficient
nature of the fullerene has limited the possibility of
making higher-valent organometallics, since back-dona-
tion of the metal d-electron density to the low-lying
antibonding orbitals4 of the fullerene is weakened in
these complexes. Thus, upon oxidation of the metal
center, the η2-bonded transition metal tends to dissoci-
ate from the fullerene core.5,6 Another general problem
is the radial orientation of the fullerene π-orbitals,
We previously reported that a pentamethylated [60]-
fullerene anion ( )C60Me5)8 forms stable transition-
metal η5-complexes, such as Fe(η5-C60Me5)Cp,9 Ru(η5-
C
60Me5)Cp,10
Ru(η5-C60Me5)Cl(CO)2,11
Rh(η5-
C60Me5)(CO)2,12 and Pd(η5-C60Me5)(π-allyl).13 Ru(η5-
C60Me5)Cl(CO)2 has been shown to undergo exchange
of the carbonyl ligand and the chlorine atom to afford a
variety of alkyl and alkynyl complexes without loss of
the C60Me5 ligand.11 In the present study, we examined
whether the metal C60Me5 complex can be chemically
oxidized to give a higher-valent metal complex without
cleavage of the metal-fullerene bond. To this end, we
focused on the iridium fullerene complex,14-20 since
iridium complexes are known to give stable high-valent
complexes.21 Successful oxidation of the metal center of
metal fullerene complexes has not been reported so far,
* To whom correspondence should be addressed. E-mail:
nakamura@chem.s.u-tokyo.ac.jp.
(7) Haddon, R. C. Science 1993, 261, 1545-1550.
(8) (a) Sawamura, M.; Toganoh, M.; Kuninobu, Y.; Kato, S.; Naka-
mura, E. Chem. Lett. 2000, 270-271. (b) Nakamura, E.; Sawamura,
M. Pure Appl. Chem. 2001, 73, 355-359.
(1) Hashimoto, A.; Yorimitsu, H.; Ajima, K.; Suenaga, K.; Isobe, H.;
Miyawaki, J.; Yudasaka, M.; Iijima, S.; Nakamura, E. Proc. Natl. Acad.
Sci. U.S.A. 2004, 101, 8527-8530.
(2) Kra¨tschmer, W.; Lamb, L. D.; Fostiropoulos, K.; Huffman, D. R.
Nature 1990, 347, 354-358.
(9) (a) Sawamura, M.; Kuninobu, Y.; Toganoh, M.; Matsuo, Y.;
Yamanaka, M.; Nakamura, E. J. Am. Chem. Soc. 2002, 124, 9354-
9355. (b) Nakamura, E. Pure Appl. Chem. 2003, 75, 427-434.
(10) Matsuo, Y.; Kuninobu, Y.; Ito, S.; Nakamura, E. Chem. Lett.
2004, 33, 68-69.
(3) (a) Stephens, A. H. H.; Green, M. L. H. Adv. Inorg. Chem. 1997,
44, 1-43. (b) Balch, A. L.; Olmstead, M. M. Chem. Rev. 1998, 98, 2123-
2165.
(4) Haddon, R. C.; Brus, L. E.; Raghavachari, K. Chem. Phys. Lett.
1986, 125, 459-464.
(11) Matsuo, Y.; Nakamura, E. Organometallics 2003, 22, 2554-
2563.
(5) Lerke, S. A.; Parkinson, B. A.; Evans, D. H.; Fagan, P. J. J. Am.
Chem. Soc. 1992, 114, 7807-7813.
(12) Sawamura, M.; Kuninobu, Y.; Nakamura, E. J. Am. Chem. Soc.
2000, 122, 12407-12408.
(6) Chernega, A. N.; Green, M. L. H.; Haggitt, J.; Stephens, A. H.
H. J. Chem. Soc., Dalton Trans. 1998, 755-767.
(13) Kuninobu, Y.; Matsuo, Y.; Toganoh, M.; Sawamura, M.; Naka-
mura, E. Organometallics 2004, 23, 3259-3266.
10.1021/om049333l CCC: $30.25 © 2005 American Chemical Society
Publication on Web 11/30/2004

90 Organometallics, Vol. 24, No. 1, 2005
Matsuo et al.
Scheme 1. Synthesis and Derivatization of the
except for a rare example of oxidation of the iridium
complex by molecular oxygen.17d We herein report the
synthesis of the Ir(I) C60Me5 complex 1 and oxidation
reaction of this Ir(I) complex 2 by iodine into an Ir(III)
complex bearing two iodo ligands. We also describe the
structures and the electrochemical properties of the Ir-
(I) and Ir(III) complexes and report on the carbonyl
ligand exchange and alkylation and alkynylation of the
iodo complex.
Ir(η5-C60Me5) Complexes
Results and Discussion
Synthesis and Characterization of Iridium Di-
carbonyl Complex. We found that the success of
complexation of an iridium metal to the C60Me5 ligand
strongly depends on the choice of the starting iridium
compound. Synthesis of the first iridium-C60Me5 com-
plex was achieved by the use of the rather uncommon
iridium dicarbonyl chloro dimer [IrCl(CO)2]2,22 which
can be prepared by treatment of [IrCl(coe)2]2 (coe )
cyclooctene) with carbon monoxide gas (1 atm) in
acetonitrile. A yellow acetonitrile solution of [IrCl(CO)2]2
was mixed with a THF solution of K(C60Me5), affording
the iridium C60Me5 dicarbonyl complex Ir(C60Me5)(CO)2
(1) as orange microcrystals (Scheme 1). Several attempts
to obtain iridium C60Me5 complexes by the reaction of
K(C60Me5) with other starting materials, [IrCl(coe)2]2,
[IrCl(1,5-cod)2]2 (cod ) cyclooctadiene), IrCl(py)(CO)2 (py
) pyridine), Ir(acac)(CO)2 (acac ) acetylacetonato), and
IrCl(CO)(PPh3)2, resulted in recovery of C60Me5H. The
η5 complex 1 is quite stable toward molecular oxygen,
water, and heat (100 °C) both in a solution and as a
solid. This property stands in contrast to that of most
of the known iridium η2-fullerene complexes;3 for in-
stance, a complex of the Vaska-type iridium complex23
and C60, Ir(η2-C60)Cl(CO)(PPh3)2, is fluxional in solu-
tion.14a,19
Complex 1 was characterized by IR, 1H and 13C NMR,
and UV measurements and combustion analysis. The
IR spectrum of 1 showed two bands for symmetric and
asymmetric stretching vibrations of the two carbonyl
ligands at 2031 and 1968 cm-1, which are nearly
identical with those of the similar dicarbonyl complex
IrCp(CO)2 (νCO 2037 and 1957 cm-1; Cp ) C5H5),24 and
higher than those of IrCp*(CO)2 (νCO 2000 and 1925
cm-1; Cp* ) C5Me5).25 The increase of the νCO value
observed in 1 is probably caused by stronger back-
donation to the C60Me5 ligand than to the C5Me5 ligand.
(14) (a) Balch, A. L.; Catalano, V. J.; Lee, J. W. Inorg. Chem. 1991,
30, 3980-3981. (b) Balch, A. L.; Catalano, V. J.; Lee, J. W.; Olmstead,
M. M.; Parkin, S. R. J. Am. Chem. Soc. 1991, 113, 8953-8955. (c)
Balch, A. L.; Catalano, V. J.; Lee, J. W.; Olmstead, M. M. J. Am. Chem.
Soc. 1992, 114, 5455-5457. (d) Balch, A. L.; Lee, J. W.; Noll, B. C.;
Olmstead, M. M. J. Am. Chem. Soc. 1992, 114, 10984-10985. (e) Balch,
A. L.; Lee, J. W.; Olmstead, M. M. Angew. Chem., Int. Ed. Engl. 1992,
31, 1356-1358. (f) Balch, A. L.; Ginwalla, A. S.; Lee, J. W.; Noll, B.
C.; Olmstead, M. M. J. Am. Chem. Soc. 1994, 116, 2227-2228. (g)
Balch, A. L.; Costa, D. A.; Lee, J. W.; Noll, B. C.; Olmstead, M. M.
Inorg. Chem. 1994, 33, 2071-2072. (h) Balch, A. L.; Lee, J. W.; Noll,
C.; Olmstead, M. M. Inorg. Chem. 1994, 33, 5238-5243. (i) Balch, A.
L.; Costa, D. A.; Noll, B. C.; Olmstead, M. M. J. Am. Chem. Soc. 1995,
117, 8926-8932. (j) Balch, A. L.; Costa, D. A.; Noll, B. C.; Olmstead,
M. M. Inorg. Chem. 1996, 35, 458-462.
(15) (a) Koefod, R. S.; Hudgens, M. F.; Shapley, J. R. J. Am. Chem.
Soc. 1991, 113, 8957-8958. (b) Zhu, Y.; Koefod, R. S.; Devadoss, C.;
Shapley, J. R.; Schuster, G. B. Inorg. Chem. 1992, 31, 3505-3506. (c)
Koefod, R. S.; Xu, C.; Lu, W.; Shapley, J. R.; Hill, M. G.; Mann, K. R.
J. Phys. Chem. 1992, 96, 2928-2930.
(16) (a) Rasinkangas, M.; Pakkanen, T. T.; Pakkanen, T. A.; Ahlgre´n,
M.; Rouvinen, J. J. Am. Chem. Soc. 1993, 115, 4901-4901. (b)
Soimasuo, M.; Pakkanen, T. T.; Ahlgre´n, M.; Pakkanen, T. A. Polyhe-
dron 1998, 17, 2073-2077.
1
The H NMR spectrum of 1 exhibited only one singlet
at δ 2.43 for the five magnetically equivalent methyl
groups on the C60 skeleton. The 13C NMR spectrum
displayed only a small number of signals due to the C5v-
symmetric fullerene skeleton: the cyclopentadienyl
moiety (δ 109.73), the sp3 fullerene carbon atom (δ
51.99), and five other types of fullerene sp2 carbon atoms
(δ 143.09, 144.32, 147.30, 148.54, 148.82, and 151.36),
together with five methyl groups on the fullerene moiety
(δ 30.59) and a carbonyl signal on the iridium (δ 193.14).
The UV spectrum of 1 showed a broad absorption
extended to ca. 550 nm with the maximum wavelengths
(λmax/nm) 261 (ꢀ ) 6.7 × 104), 349 (ꢀ ) 1.6 × 104), and
400 (ꢀ ) 8.7 × 103).
(17) (a) Usatov, A. V.; Kudin, K. N.; Vorontsov, E. V.; Vinogradova,
L. E.; Novikov, Y. N. J. Organomet. Chem. 1996, 522, 147-153. (b)
Usatov, A. V.; Peregudova, S. M.; Denisovich, L. I.; Vorontsov, E. V.;
Vinogradova, L. E.; Novikov, Y. N. J. Organomet. Chem. 2000, 599,
87-96. (c) Usatov, A. V.; Martynova, E. V.; Dolgushin, F. M.; Peregu-
dov, A. S.; Antipin, M. Y.; Novikov, Y. N. Eur. J. Inorg. Chem. 2002,
2565-2567. (d) Usatov, A. V.; Martynova, E. V.; Dolgushin, F. M.;
Peregudov, A. S.; Antipin, M. Y.; Novikov, Y. N. Eur. J. Inorg. Chem.
2003, 29-33.
An unambiguous structure determination of 1 was
achieved by single-crystal X-ray diffraction analysis.
Recrystallization of 1 by slow diffusion of methanol into
a toluene solution of 1 gave single crystals suitable for
X-ray crystallography. Figure 1 shows the molecular
structure of 1, and selected geometrical parameters are
summarized in Table 1. The iridium atom is bonded to
the fullerene cyclopentadienide carbon atoms in an η5
(18) Schreiner, S.; Gallaher, T. N.; Parsons, H. K. Inorg. Chem. 1994,
33, 3021-3022.
(19) Catalano, V. J.; Parodi, N. Inorg. Chem. 1997, 36, 537-541.
(20) Lee, G.; Cho, Y.-J.; Park, B. K.; Lee, K.; Park, J. T. J. Am. Chem.
Soc. 2003, 125, 13920-13921.
(21) Comprehensive Organometallic Chemistry II; Abel, E. W., Stone,
F. G. A., Wilkinson, G., Atwood, J. D., Eds.; Pergamon Press: New
York, 1995; Vol. 8.
(23) Vaska, L. Acc. Chem. Res. 1968, 1, 335-344.
(24) Fischer, E. O.; Brenner, K. S. Z. Naturforsch. 1962, 17b, 774-
776.
(25) Kang, J. W.; Moseley, K.; Maitlis, P. M. J. Am. Chem. Soc. 1969,
91, 5970-5977.
(22) Roberto, D.; Cariati, E.; Psaro, R.; Ugo, R. Organometallics
1994, 13, 4227-4231.

Iridium Pentamethyl[60]fullerene Complexes
Organometallics, Vol. 24, No. 1, 2005 91
Figure 2. Cyclic voltammogram of 1 at 25 °C in a THF
solution containing n-Bu4NClO4 as a supporting electrolyte
(scan rate 100 mV/s).
to those of Rh(η5-C60Me5)(CO)2 (E1/2
) -1.46 V and
red1
) -1.94 V) and Ru(η5-C60Me5)Cl(CO)2 (E1/2
red2
red1
E1/2
Figure 1. Crystal structure of 1: (a) ORTEP drawing with
red2
) -1.34 V and E1/2
) -1.94 V) and, thus, are
30% probability level ellipsoids; (b) space-filling models.
assigned to the reduction of fullerene moieties. Note that
the iridium complex 1 shows the third reversible reduc-
tion peak of the fullerene moiety at -2.66 V, which has
not so far been observed for the previously reported C60-
Me5 and C60Ph5 metal complexes.9a,11,12,13,27 The com-
pound 1 is thus robust even under the harsh reduction
conditions. In the anodic scan, complex 1 exhibited a
one-step two-electron irreversible oxidation (0.71 V vs
Fc/Fc+), which is due to Ir(I)/Ir(III) oxidation. We next
examined chemical oxidation to prepare the Ir(III)
complexes, as described in the following section.
Table 1. Selected Bond Lengths (Å) and Angles
(deg) for 1, 2, and 3a
Ir(η5-C60Me5)(CO)2 (1)
Ir-C1
2.310(10)
2.276(11)
2.322(11)
2.326(10)
2.286(11)
2.30
Ir-centroid(Cp)
Ir-C6
1.95
Ir-C2
1.84(2)
1.815(19)
1.16(2)
1.19(2)
Ir-C3
Ir-C7
Ir-C4
C6-O1
C7-O2
Ir-C5
Ir-C(Cp)a
C6-Ir-C7
89.3(7)
Ir(η5-C60Me5)I2(CO) (2)
Oxidation of 1: Synthesis of the Ir(III) C60Me5
Complexes. Oxidation of the metal center of the Ir(I)
complex 1 by I2 smoothly proceeded to afford the
expected Ir(III) complex. Treatment of 1 with 1.0 equiv
of I2 in toluene at 25 °C afforded an air-stable iridium
diiodo complex, Ir(η5-C60Me5)I2(CO) (2), in 80% yield
(Scheme 1). This clean conversion from Ir(I) to Ir(III)
and stability of the Ir(III) complex can be attributed to
the electronic properties of the C60R5 ligand, whose
occupied highest molecular orbital (HOMO) is delocal-
ized at the top pentagon.27b This cyclopentadienyl
moiety stabilizes the d6 metal center of the octahedral
geometry by facial coordination. In the IR spectrum of
2, absorption due to the carbonyl ligand was observed
Ir-C1
Ir-C2
Ir-C3
Ir-C4
Ir-C5
2.225(9)
Ir-C(Cp)a
Ir-centroid(Cp)
Ir-C16
2.28
2.243(9)
2.350(9)
2.340(9)
2.239(10)
1.93
1.881(19)
1.14(2)
C16-O1
C1-C6-C11
C2-C7-C12
C3-C8-C13
120.9(10)
C4-C9-C14
C5-C10-C15
117.2(9)
112.6(9)
115.0(9)
115.9(10)
Ir(η5-C60Me5)(PMe3)(CO) (3a)
Ir-C1
2.370(16)
2.359(16)
2.305(15)
2.285(16)
2.323(16)
2.33
Ir-C16
Ir-P
P-C17
P-C18
P-C19
C16-O1
1.83(2)
2.261(6)
1.81(2)
1.79(2)
1.80(2)
1.09(2)
Ir-C2
Ir-C3
Ir-C4
Ir-C5
Ir-C(Cp)a
Ir-centroid(Cp)
1
at 2051 cm-1. The H NMR measurement gave a very
1.99
simple spectrum consisting of only one singlet signal due
to the methyl groups on the fullerene moiety at δ 2.42.
The 13C NMR spectrum exhibited 10 signals: two
signals in the sp3 region (δ 30.16 and 51.74), one (δ
109.79) due to the Cp carbons, six in the sp2 region (δ
142.70, 143.90, 147.01, 148.25, 148.50, and 150.93), and
one (δ 186.28) due to the carbonyl carbon. These
observations indicate time-averaged pseudo C5v sym-
metry of the C60Me5 ligand in solution.
The molecular structure of 2 was determined by the
single-crystal X-ray diffraction study. The ORTEP
drawing and space-filling models are shown in Figure
3, and selected bond distances and angles are listed in
Table 1. The d6 iridium metal center adopts a three-
C1-C6-C11
C2-C7-C12
C3-C8-C13
120.9(10)
C4-C9-C14
C5-C10-C15
P-Ir-C16
117.2(9)
112.6(9)
87.0(7)
115.0(9)
115.9(10)
a Averaged bond distances of the five Ir-C(Cp) bonds.
fashion with an average Ir-C distance of 2.30 Å, which
is slightly longer than that of the Cp* analogue (2.26 Å
for IrCp*(CO)2).26 The iridium-carbon bond length for
the η5-complex 1 is substantially longer than those for
η2-complexes (2.155(8)-2.194(10) Å)14 and for the µ2,η2:
η2-complex C60{Ir2Cl2(1,5-cod)2}2 (2.201(7)-2.231(6) Å).16
In the electrochemical analysis, 1 showed reversible
three-electron-reduction events (E1/2red1 ) -1.39, E1/2
red2
red3
) -2.01, and E1/2
) -2.66 V vs Fc/Fc+) within the
solvent cutoff window of THF, as shown in Figure 2.
(27) (a) Sawamura, M.; Iikura, H.; Nakamura, E. J. Am. Chem. Soc.
1996, 118, 12850-12851. (b) Iikura, H.; Mori, S.; Sawamura, M.;
Nakamura, E. J. Org. Chem. 1997, 62, 7912-7913. (c) Sawamura, M.;
Iikura, H.; Ohama, T.; Hackler, U. E.; Nakamura, E. J. Organomet.
Chem. 2000, 599, 32-36.
The lower two reduction potentials of 1 are comparable
(26) Chen, J.; Daniels, L. M.; Angelici, R. J. Acta Crystallogr. 1993,
C49, 1061-1063.

92 Organometallics, Vol. 24, No. 1, 2005
Matsuo et al.
The reversible reduction of 2 suggests that conversion
between the Ir(III) and the reduced complexes occurs
without structural changes. This stability of the complex
2 to the reduction is probably due to the ability of the
C60Me5 ligand to conjugatively27b stabilize the negative
charges that would otherwise localize on the metal
atom. Complex 2 could not be oxidized within the
solvent cutoff window.
Carbonyl Ligand Exchange of 1 and 2. The
carbonyl ligand of the Ir-C60Me5 complexes could be
readily replaced by phosphine and isonitrile ligands.
Note that such ligand exchange reactions of the carbonyl
ligand have not been observed for the iridium η2-
fullerene mononuclear complexes.3,15a The reaction of 1
with an excess amount (15 equiv) of PEt3 and PPh3 in
THF proceeded under reflux conditions to afford the
phosphine complexes Ir(η5-C60Me5)(PEt3)(CO) (3b) and
Ir(η5-C60Me5)(PPh3)(CO) (3c) in 60% and 35% yields,
respectively. Neither prolonged reaction time nor addi-
tion of phosphines promoted the exchange reaction of
the second carbonyl group, likely because of both steric
and electronic effects of the C60Me5 ligand. We next
attempted to replace the carbonyl ligand of 2 by the
phosphine ligand: we found that addition of phosphines
to 2 reduces the complex, giving back an Ir(I) complex.
Treatment of 2 with 5 equiv of PMe3 or PPh3 proceeded
in THF at 25 °C to afford Ir(η5-C60Me5)(PR3)(CO) (3a
(R ) Me), 3c (R ) Ph)) in 92% and 50% yields,
respectively. When an isonitrile was used, the ligand
exchange reaction of 2 with XylNC (Xyl ) 2,6-dimeth-
ylphenyl) cleanly took place without changing the
valence of the metal center and afforded the Ir(III)
isonitrile complex Ir(C60Me5)I2(XylNC) (4) in 93% yield.
Figure 3. Crystal structure of 2‚C6H6: (a) ORTEP draw-
ing with 30% probability level ellipsoids (a benzene mol-
ecule found in the unit cell is omitted for clarity); (b) space-
filling models.
The 1H and 13C NMR spectra of 3a-c and 4 exhibited
signals due to the pseudo C5v symmetric structure, and
the 31P NMR signals were observed for the phosphine
complexes (δ -48.32 for 3a, δ 3.27 for 3b, and δ 11.22
for 3c). The vibration stretching values (1932-1933
cm-1) of the carbonyl ligand in the IR spectra of the Ir-
(I) trialkylphosphine complexes 3a,b are lower than
those of 1 and 2, being in good accordance with the more
electron-rich nature of the Ir atoms in 3a,b. The
molecular structure of the phosphine complex was
determined by the X-ray analysis of a crystal of 3a,
which was obtained by slow evaporation of the toluene
solution. The crystal structure of 3a is shown in Figure
5, and selected bond lengths and angles are listed in
Table 1. The P-Ir-C16 angle is 87.0(7)°, smaller than
the C6-Ir-C7 angle of 1 (89.3(7)°), probably because
of the steric hindrance between C60Me5 and the phos-
phine ligand.
Figure 4. Cyclic voltammogram of 2 at 25 °C in a THF
solution containing n-Bu4NClO4 as a supporting electrolyte
(scan rate 100 mV/s).
legged piano-stool geometry surrounded by two iodine
atoms and one carbon monoxide ligand. The average
distance between iridium and fullerene cyclopentadi-
enide carbon atoms (2.28 Å) is comparable to that of 1,
but the steric bulkiness of the iodo ligand induces
dissymmetric coordination of the C60Me5 ligand (Ir-C1
) 2.225(9) Å, Ir-C2 ) 2.243(9) Å, Ir-C3 ) 2.350(9) Å,
Ir-C4 ) 2.340(9) Å, and Ir-C5 ) 2.239(10) Å). Steric
repulsion between the carbonyl ligand and the methyl
groups on the fullerene also affects the structure of the
fullerene ligand. The methyl group of C11, which is
situated under the carbonyl group, is pushed outward.
The C1-C6-C11 angle (120.9(10)°) is 3.7-7.3° larger
than the other four angles.
Alkylation and Alkynylation of 2. Since 2 has two
halogen atoms on the iridium center, we anticipated
that 2 serves as a useful starting material for the
synthesis of various iridium C60Me5 complexes. Complex
2 was converted to the air-stable dimethyl complex
Ir(η5-C60Me5)Me2(CO) (5) in 60% yield by reaction with
excess MeMgBr in THF at room temperature (Scheme
The electrochemical behavior of the Ir(III) complex 2
in THF at 25 °C was investigated (Figure 4). A one-
step two-electron reduction (-0.81 V) and a one-electron
reduction (-1.56 V) were observed in the cathodic scan.
The first large reduction wave is due to the reduction
of the metal center (Ir(III)/Ir(I)), while the second
reduction wave must be due to the reduction of the
fullerene moiety, as judged by a comparison with the
reported reduction potentials of the C60Me5 ligand and
the transition metal-C60Me5 complexes.8-13,27 It is note-
1
1). In the H and 13C NMR spectra of 5, characteristic
proton and carbon signals due to the methyl group
directly bonded to the iridium center were observed at
δ 1.57 and -30.73, respectively. These chemical shift
values are comparable to those of the Cp* complex
worthy that neither the C60Me5 nor the I- anion
-
dissociates from the three-electron-reduced species 23-
.

Iridium Pentamethyl[60]fullerene Complexes
Organometallics, Vol. 24, No. 1, 2005 93
electron-accepting nature31 of the fullerene are the
properties of interest when we consider utilization in
catalysis.
Experimental Section
General Considerations. All manipulations were carried
out under a nitrogen or argon atmosphere with standard
Schlenk techniques. The water content of solvents was deter-
mined with a Karl Fischer moisture titrator (MK-210, Kyoto
Electronics Co.) to be less than 30 ppm. All reactions were
monitored by HPLC (column, Cosmosil-Buckyprep, 4.6 × 250
mm, Nacalai Tesque; flow rate, 1.0 mL/min; eluent, toluene/
2-propanol (7/3); detector, Shimadzu SPD-M10Avp). Prepara-
tive HPLC was performed on a Buckyprep column (20 × 250
mm) using toluene/2-propanol (9/1 or 7/3) as eluent (flow rate
20 mL/min, detected at 350 nm with an UV spectrophotometric
detector, Shimadzu SPD-6A). Isolated yields were calculated
on the basis of the starting fullerene compounds. All NMR
spectra were measured with JEOL EX-400 (400 MHz), JEOL
ECA-500 (500 MHz), or Bruker AM500 (500 MHz) instru-
ments. Spectra are reported in parts per million from internal
tetramethylsilane (δ 0.00 ppm) or residual protons of the
deuterated solvent for 1H NMR, from solvent carbon (e.g. δ
77.00 ppm for chloroform) for 13C NMR, and from external H3-
PO4 (δ 0.00 ppm) for 31P NMR. Other spectra were recorded
by the use of the following instruments: IR spectra, Applied
Systems Inc. React-IR 1000; UV/vis spectra, Hitachi U3500;
mass spectra, Shimadzu LCMS-QP8000, Waters ZQ2000, and
JEOL JMS-T100LC. Elemental analyses were performed at
the organic elemental analysis laboratory in this department.
Materials. THF and toluene were distilled from Na/K alloy,
and acetonitrile and hexane were distilled from CaH2 before
use. All solvents were thoroughly degassed by trap-to-trap
distillation and stored under argon. A THF solution of t-BuOK
was purchased from Sigma-Aldrich Co. and used as received.
C60Me5H was prepared according to our previous report.8 [IrCl-
(coe)2]2 was prepared according to literature methods.32
[(1,2,3,4,5-η)-6,9,12,15,18-Pentamethyl-1,6,9,12,15,18-
Figure 5. Molecular structure of 3a‚C6H5CH3: (a) ORTEP
drawing with 30% probability level ellipsoids (a toluene
molecule found in the unit cell is omitted for clarity); (b)
space-filling models.
Ir(Cp*)Me2(CO) (δH 0.32, δC -24.3).28 The monomethyl-
ated complex Ir(η5-C60Me5)MeI(CO) (6) was also ob-
tained by the reaction of 2 with equimolar MgMe2 in
THF at 25 °C in 50% yield. An alkynyl complex was
synthesized in a similar manner. The reaction of 2 with
a phenylalkynyl Grignard reagent at 25 °C proceeded
smoothly to give the air-stable dialkynyl complex Ir(η5-
C60Me5)(CCPh)2(CO) (7) in 81% yield.
Conclusion
We synthesized the iridium(I) C60Me5 complex 1 as a
new member of the transition-metal C60Me5 complexes
(transition metals ) Fe, Ru, Rh, group 10 triad) and
demonstrated that 1 tolerates oxidation of the metal
center and can be converted to the Ir(III) complex 2 by
treatment with iodine in good yield. The iodo and
carbonyl ligands of 2 are easily replaced by alkyl,
alkynyl, phosphine, and isonitrile ligands. Complex 2
will therefore be a useful starting material for the
construction of various metal fullerene hybrid molecules.
Hereupon, the difunctional nature of 2 (i.e., the two
metal-halogen bonds of 2) is complementary to the
monofunctional nature of the reported ruthenium C60-
Me5 monochloro complexes.11 Transition-metal dihalides
bearing a suitable ancillary ligand are generally useful
catalyst precursors for various synthetic reactions, and
in particular, d6 iridium(III) cyclopentadienyl complexes
are useful for C-H bond activation29 and catalytic
transfer hydrogenation reactions.30 Therefore, we an-
ticipate that the Ir(III) C60Me5 complexes will serve as
catalysts for organic synthesis. The light-sensitizing and
hexahydro[60]fulleren-1-yl]dicarbonyliridium,
Ir(η5-
C60Me5)(CO)2 (1). To a suspension of C60Me5H (500 mg, 0.628
mmol) in THF (50 mL) was added a solution of t-BuOK (1.0
M, 0.75 mL, 0.75 mmol) in THF under argon. The reaction
mixture was stirred for 30 min at room temperature. After
removal of the solvent under reduced pressure, the resulting
solid was dissolved in THF again. In another Schlenk tube,
[IrCl(coe)2]2 (703 mg, 0.785 mmol) was suspended in CH3CN
(50 mL) under argon, and the suspension was vigorously
stirred. Replacement of argon with carbon monoxide followed
by stirring for ca. 10 min afforded a yellow solution of [IrCl-
(CO)2]2. The solution of K(C60Me5) was added to the solution
of [IrCl(CO)2]2 through a cannula, and the mixture was stirred
for 5 min. After the solvent was evaporated in vacuo, the
residue was dissolved in toluene (50 mL) and insoluble
products were removed by filtration through a pad of silica
(30) (a) Mashima, K.; Abe, T.; Tani, K. Chem. Lett. 1998, 1199-
1200. (b) Mashima, K.; Abe, T.; Tani, K. Chem. Lett. 1998, 1201-1202.
(c) Murata, K.; Ikariya, T.; Noyori, R. J. Org. Chem. 1999, 64, 2186-
2187. (d) Murata, K.; Konishi, H.; Ito, M.; Ikariya, T. Organometallics
2002, 21, 253-255. (e) Ogo, S.; Makihara, N.; Kaneko, Y.; Watanabe,
Y. Organometallics 2001, 20, 4903-4910. (f) Fujita, K.; Furukawa, S.;
Yamaguchi, R. J. Organomet. Chem. 2002, 649, 289-292. (g) Fujita,
K.; Yamamoto, K.; Yamaguchi, R. Org. Lett. 2002, 4, 2691-2694. (h)
Suzuki, T.; Morita, K.; Tsuchida, M.; Hiroi, K. Org. Lett. 2002, 4, 2361-
2363. (i) Suzuki, T.; Morita, K.; Tsuchida, M.; Hiroi, K. J. Org. Chem.
2003, 68, 1601-1602.
(31) (a) Fukuzumi, S.; Guldi, D. M. Electron-Transfer Chemistry of
Fullerenes. In Electron-Transfer Chemistry; Balzani, V., Ed.; Wiley-
VCH: Weinheim, Germany, 2000; Vol. 2, pp 270-337. (b) Fullerenes:
From Synthesis to Optoelectronic Properties; Guldi, D. M., Martin, N.,
Eds.; Kluwer Academic: Dordrecht, The Netherlands, 2002.
(32) Herde, J, L.; Lambert, J. C.; Senoff, C. V. Inorg. Synth. 1974,
15, 18-19.
(28) Go´mez, M.; Kisenyi, J. M.; Sunley, G. J.; Maitlis, P. M. J.
Organomet. Chem. 1985, 296, 197-207.
(29) (a) Janowicz, A. H.; Bergman, R. G. J. Am. Chem. Soc. 1982,
104, 352-354. (b) Hoyano, J. K.; Graham, W. A. G. J. Am. Chem. Soc.
1982, 104, 4, 3723-3725. (c) Arndtsen, B. A.; Bergman, R. G. Science
1995, 270, 1970-1973. (d) Iverson, C. N.; Smith, M. R., III. J. Am.
Chem. Soc. 1999, 121, 7696-7697. (e) Cho, J.-Y.; Iverson, C. N.; Smith,
M. R., III. J. Am. Chem. Soc. 2000, 122, 12868-12869. (f) Diversi, P.;
Marchetti, F.; Ermini, V.; Matteoni, S. J. Organomet. Chem. 2000, 593/
594, 154-160. (g) Hou, Z.; Koizumi, T.; Fujita, A.; Yamazaki, H.;
Wakatsuki, Y. J. Am. Chem. Soc. 2001, 123, 5812-5813.

94 Organometallics, Vol. 24, No. 1, 2005
Matsuo et al.
gel. Purification with repeated preparative HPLC separation
(Buckyprep 20 mm × 250 mm, toluene/i-PrOH (7/3), flow rate
20 mL/min, retention time 8 min) gave 1 (248 mg, 38% yield)
as brown crystals. IR (KBr, cm-1): 2031 (s), 1968 (s) (νCO). 1H
NMR (400 MHz, CDCl3): δ 2.43 (s, 15H, CH3). 13C{1H} NMR
(100 MHz, CDCl3): δ 30.59 (5C, CH3), 51.99 (5C, CH3C), 109.73
(5C, C(Cp)), 143.09 (10C, C60), 144.32 (10C, C60), 147.30 (5C,
C60), 148.54 (10C, C60), 148.82 (5C, C60), 151.36 (10C, C60),
193.14 (2C, CO). APCI-MS (-): m/z 1043 (M-). UV-vis (1.0
× 10-5 M in CH2Cl2; λmax/nm (ꢀ)): 261 (6.7 × 104), 349 (1.6 ×
104), 400 (8.7 × 103). Anal. Calcd for C67H15O2Ir: C, 77.08; H,
1.45. Found: C, 76.89; H, 1.72.
106.92 (5C, C(Cp)), 143.54 (10C, C(C60)), 144.63 (10C, C(C60)),
146.71 (5C, C(C60)), 147.73 (10C, C(C60)), 148.40 (5C, C(C60)),
153.52 (10C, C(C60)), 177.35 (d, JP-C ) 19.9 Hz, 1C, CO).
2
31P{1H} NMR (200 MHz, CDCl3): δ 3.27. APCI-HRMS (-): m/z
calcd for C72H30IrOP (M-), 1132.1640; found, 1132.1600.
[(1,2,3,4,5-η)-6,9,12,15,18-Pentamethyl-1,6,9,12,15,18-
hexahydro[60]fulleren-1-yl]carbonyl(triphenylphosphi-
ne)iridium, Ir(η5-C60Me5)(CO)(PPh3) (3c). This compound
was prepared in a manner similar to that for 3b. Complex 3c
was isolated (35% yield) as reddish brown crystals by repeated
preparative HPLC separation. 1H NMR (400 MHz, CDCl3): δ
2.23 (s, 15H, CH3), 7.44-7.70 (m, 15H, C6H5). 13C{1H} NMR
(125 MHz, CDCl3/CS2): δ 30.83 (s, 5C, CH3), 50.20 (s, 5C,
[(1,2,3,4,5-η)-6,9,12,15,18-Pentamethyl-1,6,9,12,15,18-
hexahydro[60]fulleren-1-yl]carbonyldiiodoiridium, Ir-
(η5-C60Me5)I2(CO) (2). To a solution of Ir(η5-C60Me5)(CO)2 (1;
100 mg, 0.0957 mmol) in THF (100 mL) was added I2 (24.5
mg, 0.0957 mmol). After the mixture was stirred for 5 min,
the solvent was evaporated under reduced pressure. Repeated
preparative HPLC separation (Buckyprep 20 mm × 250 mm,
toluene/i-PrOH (9/1), flow rate 20 mL/min, retention time 12
min) afforded reddish brown crystals of 2 (97.3 mg, 80% yield).
IR (powder, cm-1): 2051 (s) (νCO), 2964 (m), 2921 (m), 2854
3
CH3C), 107.36 (s, 5C, C(Cp)), 127.78 (d, JC-P ) 10.8 Hz, 6C,
2
m-C6H5), 130.19 (s, 3C, p-C6H5), 134.96 (d, JC-P ) 12.0 Hz,
6C, o-C6H5), 136.99 (d, 1JC-P ) 56.38 Hz, 3C, ipso-C6H5), 143.39
(s, 10C, C(C60)), 144.23 (s, 10C, C(C60)), 146.40 (s, 5C, C(C60)),
147.47 (s, 10C, C(C60)), 148.13 (s, 5C, C(C60)), 153.01 (s, 10C,
C(C60)), 174.08 (s, 1C, CO). 31P{1H} NMR (200 MHz, CD2Cl3):
δ 11.22 (br, 1P, PPh3). APCI-HRMS (-): m/z calcd for C84H30-
IrOP (M-), 1276.1640; found, 1276.1665.
[(1,2,3,4,5-η)-6,9,12,15,18-Pentamethyl-1,6,9,12,15,18-
hexahydro[60]fulleren-1-yl]carbonyl(2,6-dimethyl-
phenyl isocyanide)iridium, Ir(η5-C60Me5)I2(XylNC) (4).
To a solution of 2 (4.50 mg, 0.00354 mmol) in THF (5 mL)
was added a solution of 2,6-dimethylphenyl isocyanide (2.31
mg, 0.0177 mmol) under argon. After stirring for 15 h at 25
°C, the solvent was removed under reduced pressure. The
residue was dissolved in toluene and this solution passed
through a pad of silica gel. The filtrate was concentrated under
reduced pressure, and addition of ethanol to the solution
afforded 4 (4.10 mg, 93% yield) as reddish brown crystals. IR
(powder, cm-1): 2964 (m), 2917 (m), 2858 (m) (νC-H), 2167 (s)
(νNC). 1H NMR (400 MHz, CDCl3): δ 2.75 (s, 15H, C60CH3),
2.79 (s, 6H, CCH3), 7.24 (br, 3H, CH(Xyl)). 13C{1H} NMR (100
MHz, CDCl3): δ 19.27 (2C, CH3(Xyl)), 29.89 (5C, CH3), 51.68
(5C, CH3C), 105.46 (5C, Cp), 124.91 (1C, ipso-C6H3), 128.20
(2C, m-C6H3), 129.74 p-C6H3), 136.81 (m-C6H3), 143.08 (10C,
C(C60)), 143.90 (10C, C(C60)), 147.18 (5C, C(C60)), 148.35 (10C,
C(C60)), 148.55 (5C, C(C60)), 151.72 (10C, C(C60)), 177.57 (1C,
CO), 209.90 (1C, NC). APCI-HRMS (+): m/z calcd for C74H24-
IIrN (M - I+), 1244.0585; found, 1244.0559.
[(1,2,3,4,5-η)-6,9,12,15,18-Pentamethyl-1,6,9,12,15,18-
hexahydro[60]fulleren-1-yl]dimethyliridium,Ir(η5-C60Me5)-
Me2(CO) (5). To a solution of 2 (10.0 mg, 0.00788 mmol) in
THF (5 mL) was added a solution of MeMgBr in THF (1.0 M,
95 µL, 0.095 mmol). After the mixture was stirred for 5 min
at room temperature, the solvent was evaporated in vacuo,
and the residue was diluted in toluene. The resulting suspen-
sion was passed through a pad of silica gel. Repeated prepara-
tive HPLC separation (Buckyprep 20 mm × 250 mm, toluene/
i-PrOH (7/3), flow rate 16 mL/min, retention time 10 min)
afforded reddish brown crystals of 5 (4.9 mg, 60% yield). IR
(powder, cm-1): 1994 (s) (νCO), 2962 (m), 2920 (m), 2851 (m)
(νCH). 1H NMR (400 MHz, CDCl3): δ 1.57 (s, 6H, Ir-CH3), 2.44
(s, 15H, C60CH3). 13C{1H} NMR (125 MHz, CDCl3): δ -30.73
(2C, Ir-CH3), 27.91 (5C, C60CH3), 51.39 (5C, CH3C), 110.74
(5C, Cp), 143.69 (10C, C60), 144.03 (10C, C60), 146.90 (5C, C60),
147.93 (10C, C60), 148.52 (5C, C60), 152.97 (10C, C60), 169.67
(1C, CO). APCI-HRMS (-): m/z calcd for C68H21IrO (M-),
1046.1222; found, 1046.1246.
1
(m) (νC-H). H NMR (400 MHz, CDCl3): δ 2.42 (s, 15H, CH3).
13C{1H} NMR (100 MHz, CDCl3): δ 30.16 (5C, CH3), 51.74 (5C,
CH3C), 109.79 (5C, Cp), 142.70 (10C, C60), 143.90 (10C, C60),
147.01 (5C, C60), 148.25 (10C, C60), 148.50 (5C, C60), 150.93
(10C, C60), 186.28 (1C, CO). UV-vis (1.0 × 10-5 M in CH2Cl2;
λmax/nm (ꢀ)): 260 (7.67 × 104), 354 (2.06 × 104), 393 (1.31 ×
104). APCI-MS (-): m/z 1269 (M-). APCI-HRMS (-): m/z calcd
for C65H15I2Ir (M- - CO), 1241.8890; found, 1241.8860.
[(1,2,3,4,5-η)-6,9,12,15,18-Pentamethyl-1,6,9,12,15,18-
hexahydro[60]fulleren-1-yl]carbonyl(trimethylphosphi-
ne)iridium, Ir(η5-C60Me5)(CO)(PMe3) (3a). To a solution of
2 (5.00 mg, 0.003 91 mmol) in THF (5.0 mL) was added a
solution of PMe3 in THF (1.0 M, 20 µL, 0.0200 mmol), and the
mixture was stirred for 10 min. After the solvent was evapo-
rated in vacuo, the residue was dissolved in toluene (10 mL).
The resulting suspension was filtrated through a pad of silica
gel, and the filtrate was concentrated to 2 mL under reduced
pressure. Addition of hexane (10 mL) to the solution precipi-
tated a solid, which was collected by filtration, washed with
hexane (10 mL), and dried under vacuum to afford 3a (3.93
mg, 92%) as dark red crystals. IR (powder, cm-1): 2962 (m),
1
2910 (m), 2854 (m) (νC-H), 1933 (s) (νCO). H NMR (500 MHz,
2
CDCl3): δ 2.11 (d, JP-H ) 10.5 Hz, 9H, PCH3), 2.41 (s, 15H,
1
C60CH3). 13C{1H} NMR (125 MHz, CDCl3): δ 26.71 (d, JP-C
) 38.8 Hz, 9C, PMe3), δ 31.98 (5C, CH3), 50.09 (5C, CH3C),
106.70 (5C, C(Cp)), 143.57 (10C, C60), 144.65 (10C, C60), 146.71
(5C, C60), 147.73 (10C, C60), 148.41 (5C, C60), 153.51 (10C, C60),
178.75 (1C, CO). 31P{1H} NMR (200 MHz, CDCl3): δ -48.32
(PMe3). APCI-HRMS (+): m/z calcd for C69H25IrOP (M + H+),
1091.1249; found, 1091.1240.
[(1,2,3,4,5-η)-6,9,12,15,18-Pentamethyl-1,6,9,12,15,18-
hexahydro[60]fulleren-1-yl]carbonyl(triethylphosphine)-
iridium, Ir(η5-C60Me5)(CO)(PEt3) (3b). To a solution of 1
(8.70 mg, 0.008 33 mmol) in THF (5 mL) was added a solution
of triethylphosphine (14.5 mg, 0.125 mmol) in THF (1.7 M,
0.74 mL) under nitrogen in a Schlenk tube, and the solution
was stirred and heated under reflux for 15 h. The solvent was
evaporated in vacuo, and the residue was diluted in toluene
(50 mL). The resulting suspension was passed through a pad
of silica gel. Repeated preparative HPLC separation (Bucky-
prep 20 mm × 250 mm, toluene/i-PrOH (7/3), flow rate 20 mL/
min, retention time 10 min) afforded reddish brown crystals
of 3b (5.70 mg, 60% yield). IR (powder, cm-1): 2960 (m), 2920
(m), 2851 (m) (νC-H), 1932 (s) (νCO). 1H NMR (400 MHz,
[(1,2,3,4,5-η)-6,9,12,15,18-Pentamethyl-1,6,9,12,15,18-
hexahydro[60]fulleren-1-yl]methyliodoiridium, Ir(η5-
C60Me5)MeI(CO) (6). To a solution of 2 (6.68 mg, 0.005 25
mmol) in THF (5 mL) was added a solution of MgMe2 in THF
(0.020 M, 0.53 mL, 0.011 mmol). After the mixture was stirred
for 5 min at room temperature, the solvent was evaporated
under reduced pressure, and the residue was dissolved in
toluene. After the solution was passed through a pad of silica
gel, repeated preparative HPLC separation (Buckyprep 20 mm
× 250 mm, toluene/ i-PrOH (7/3), flow rate 16 mL/min,
3
3
CDCl3): δ 1.32 (td, JH-H ) 7.6 Hz, JP-H ) 16.8 Hz, 9H,
3
2
PCH2CH3), 2.14 (qd, JH-H ) 7.6 Hz, JP-H ) 7.6 Hz, 6H,
PCH2), 2.42 (s, 15H, C60CH3). 13C{1H} NMR (125 MHz,
CDCl3): δ 8.83 (d, 2JP-C ) 2.37 Hz, 3C, PCH2), 23.38 (d, 2JP-C
) 36.4 Hz, 3C, PCH2CH3), 32.17 (s, 5C, CH3), 50.23 (5C, CH3C),

Iridium Pentamethyl[60]fullerene Complexes
Organometallics, Vol. 24, No. 1, 2005 95
Table 2. Crystal Data Collection Parameters for
1, 2, and 3a
retention time 15 min) afforded reddish brown crystals of 6
(3.0 mg, 50% yield). IR (powder, cm-1): 2023 (s) (νCO), 2968
(m), 2920 (m), 2851 (m) (νCH). H NMR (400 MHz, CDCl3): δ
1
1
2‚C6H6
3a‚C6H5CH3
2.54 (s, 3H, Ir-CH3), 2.57 (s, 15H, C60CH3). 13C{1H} NMR (125
MHz, CDCl3): δ -30.73 (1C, Ir-CH3), 29.08 (5C, C60CH3),
51.48 (5C, MeC), 110.55 (5C, Cp), 143.35 (10C, C60), 143.78
(10C, C60), 146.92 (5C, C60), 148.08 (10C, C60), 148.50 (5C, C60),
151.79 (10C, C60), 179.50 (1C, CO). APCI-MS (-): m/z 1157
(M-).
formula
formula wt
cryst syst
space group
a (Å)
C
67H15IrO2
C
72H21I2IrO
C76H32IrOP
1184.28
monoclinic
P21/c (No. 14)
21.462(2)
20.660(2)
10.0920(8)
90
90.906(6)
90
4474.3(8)
4
1043.99
1347.98
triclinic
monoclinic
P21/n (No. 14) P1h (No. 2)
9.9750(10)
23.1470(16)
16.0130(15)
90
93.525(4)
90
3690.3(6)
4
1.879
153(2)
9.9950(8)
13.5060(13)
17.1450(16)
73.171(5)
87.823(6)
79.239(5)
2176.1(3)
2
b (Å)
c (Å)
[(1,2,3,4,5-η)-6,9,12,15,18-Pentamethyl-1,6,9,12,15,18-
hexahydro[60]fulleren-1-yl]carbonyldi(phenylethynyl)-
iridium, Ir(η5-C60Me5)(CCPh)2(CO) (7). To a suspension of
2 (10.0 mg, 0.00788 mmol) in THF (5.0 mL) was added a
solution of (phenylethynyl)magnesium bromide (63.0 mL,
0.0320 mmol) in THF (0.50 M) at 25 °C. After the mixture was
stirred for 5 min at 25 °C, the solvent was removed in vacuo.
The residue was diluted in toluene, and the resulting suspen-
sion was passed through a pad of silica gel. The purification
of the product was carried out by preparative HPLC
(Buckyprep 20 mm × 250 mm, toluene/i-PrOH (7/3), flow rate
20 mL/min, retention time 13 min). The title compound 7 (7.76
mg, 81%) was obtained as a reddish powder. 1H NMR (500
MHz, CDCl3): δ 2.64 (s, 15H, CH3), 7.21 (tt, 3J ) 7.6 Hz, 4J )
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
Dcalcd (g/cm3)
T (K)
cryst size (mm)
2.057
153(2)
1.758
153(2)
0.15 × 0.02 × 0.20 × 0.20 × 0.40 × 0.20 ×
0.02
4.68, 51.5
7012
0.05
4.14, 51.6
7686
5748
686
0.1033,
0.2646
0.0821,
0.2226
1.136
0.01
4.38, 51.5
7693
5512
707
0.1317,
0.2932
0.1043,
0.2772
1.116
2θmin, 2θmax (deg)
no. of rflns (unique)
no. of rflns (I > 2σ(I)) 3562
no. of params
632
0.1523,
R1, wR2 (all data)
0.2921
R, Rw (I > 2.0σ(I))
GOF on F2
0.0913,
0.2306
0.933
3
3
1.2 Hz, 2H, p-C6H5), 7.33 (dd, J ) 7.6 Hz, J ) 8.4 Hz, 4H,
m-C6H5), 7.50 (dd, 3J ) 8.4 Hz, 4J ) 1.2 Hz, 4H, o-C6H5). 13C-
{1H} NMR (125 MHz, CDCl3): δ 28.71 (5C, CH3), 46.44 (2C,
Ir-C), 51.16 (5C, CCH3), 102.82 (2C, PhC), 112.02 (5C, C(Cp)),
126.26 (2C, p-C6H5), 127.23 (2C, ipso-C6H5), 127.96 (4C m-C6H5),
132.04 (4C, o-C6H5), 143.59 (10C, C60), 143.94 (10C, C60), 146.97
(5C, C60), 148.15 (10C, C60), 148.65 (5C, C60), 151.94 (10C, C60),
159.92 (1C, CO). APCI-HRMS (-): m/z calcd for C82H25IrO
(M-), 1216.1511; found, 1216.1554.
ment indices are defined as R1 ) ∑(||Fo| - |Fc||)/∑|Fo| and wR2
) [∑w(Fo - Fc2)2/∑(wFo )]1/2
2
4
.
Electrochemical Measurements. Electrochemical mea-
surements were performed using a Hokuto HZ-5000 voltam-
metric analyzer. A glassy-carbon electrode was used as the
working electrode. The counter electrode was a platinum coil,
and the reference electrode was a Ag/Ag+ electrode. Cyclic
voltammetry (CV) was performed at a scan rate of 100 mV/s.
All half-wave potentials are given as E1/2 ) (Ep,c + Ep,a)/2,
where Ep,c and Ep,a are the cathodic and anodic peak potentials,
respectively. The potential was corrected against Fc/Fc+.
X-ray Crystallographic Analysis. Crystals of 1, 2, and
3a suitable for X-ray diffraction study were mounted on a
MacScience DIP2030 imaging plate diffractometer for data
collection using Mo KR (graphite monochromated, λ ) 0.710 69)
radiation. Crystal data and data statistics are summarized in
Table 2. The structures of complexes 1, 2, and 3a were solved
by direct methods (SHELXS-97)33 and expanded using Fourier
techniques (DIRDIF-94).34 The positional and thermal param-
eters of non-hydrogen atoms of 1, 2, and 3a were refined using
a full-matrix least-squares method. Hydrogen atoms were
placed at calculated positions (C-H ) 0.95 Å) and kept fixed.
Acknowledgment. The present research was sup-
ported by a Grant-in-Aid for Specially Promoted
Research, a Grant-in-Aid for Young Scientists (A), and
the 21st Century COE Programs for Frontiers in
Fundamental Chemistry.
A generous supply of
All non-hydrogen atoms of 1, 2, and 3a were anisotropically
[60]fullerene from Frontier Carbon Corp. is gratefully
acknowledged.
2
refined. In the subsequent refinement, the function ∑w(Fo
-
Fc2)2 was minimized, where |Fo| and |Fc| are the observed and
calculated structure factor amplitudes, respectively. The agree-
Supporting Information Available: Lists of positional
parameters, thermal displacement parameters, bond lengths,
and bond angles and figures giving labeling schemes for 1, 2,
and 3a; these data are also available as CIF files. This material
is available free of charge via the Internet at http://pubs.acs.org.
(33) Sheldrick, G. M. Program for the Solution of Crystal Structures;
University of Go¨ttingen, Go¨ttingen, Germany, 1997.
(34) Beurskens, P. T.; Admiraal. G.; Beurskens, G.; Bosman, W. P.;
de Gelder, R.; Israel, R.; Smits, J. M. M. The DIRDIF-94 Program
System; Technical Report of the Crystallography Laboratory; Univer-
sity of Nijmegen, Nijmegen, The Netherlands, 1994.
OM049333L