Syntheses, structures, and electrochemical properties of Os 3(CO)9-n(CNCH2Ph)n(μ3- η2:η2:η2-C60) (n = 2-4)

Article abstract of DOI:10.1021/om060566h

Benzyl isocyanide-substituted C₆₀-triosmium complexes, Os ₃(CO)_9-n(CNCH₂Ph)_n(μ₃- η²:η²:η²-C₆₀) (n = 2 (3), 3 (4), and 4 (5)), have been prepared by reactions of either Os ₃(CO)₉(μ₃-η²: η²:η²-C₆₀) (1) or its lesser isocyanide-substituted complexes with appropriate amounts of (triphenylphosphino)benzylimine (PhCH₂N=PPh₃). Compounds 3-5 have been characterized by spectroscopic (IR, MS, ¹H and ¹³C NMR) methods, cyclic voltammetry, and X-ray diffraction studies. Single-crystal X-ray diffraction studies reveal that isomer 3a has two inequivalent equatorial isocyanide ligands as a cis,trans-1,2-isomer and isomer 4a has three equivalent equatorial isocyanide ligands as a 1,2,3-isomer with C₃ symmetry. In compound 5, one benzyl isocyanide is axially coordinated to an osmium atom, whereas the other three benzyl isocyanide ligands are equatorially coordinated to each osmium atom. ¹H and ¹³C NMR data, however, indicate that compound 3 exists as a mixture of 1,2- (3a) and 1,1-isomers (3b) in a ratio of 7:1, compound 4 as a mixture of 1,2,3- (4a) and 1,1,2-isomers (4b) in a ratio of 1:1, and compound 5, interestingly, as a single species of a 1,1,2,3-isomer in solution. The cyclic voltammetric studies reveal that all the CVs of 3-5 and related Os ₃(CO)₈(CNCH₂Ph)(μ₃- η²:η²:η²-C₆₀) (2) show four reversible redox waves that correspond to a one-electron process each with the third and fourth waves overlapped within the chlorobenzene solvent potential window. As more isocyanide ligands are coordinated in 2-5, all the corresponding half-wave potentials are gradually shifted to more negative potentials, reflecting the electrondonor property of the isocyanide ligand. Furthermore, C₆₀-mediated electron delocalization from C₆₀ to the triosmium center takes place in the trianionic species of 2-5. The two isomers of 3 and 4 apparently undergo an equivalent electrochemical process, respectively.

Full text of DOI:10.1021/om060566h

4634
Organometallics 2006, 25, 4634-4642
Syntheses, Structures, and Electrochemical Properties of
Os3(CO)9-n(CNCH2Ph)n(µ3-η2:η2:η2-C60) (n ) 2-4)
Chang Yeon Lee,† Bo Keun Park,† Jung Hee Yoon,‡ Chang Seop Hong,‡ and
Joon T. Park*,†
Department of Chemistry and School of Molecular Science (BK21), Korea AdVanced Institute of Science
and Technology, Daejeon 305-701, Korea, and Department of Chemistry and Center for Electro- and
Photo-ResponsiVe Molecules, Korea UniVersity, Seoul, 136-701, Korea
ReceiVed June 28, 2006
Benzyl isocyanide-substituted C60-triosmium complexes, Os3(CO)9-n(CNCH2Ph)n(µ3-η2:η2:η2-C60) (n
) 2 (3), 3 (4), and 4 (5)), have been prepared by reactions of either Os3(CO)9(µ3-η2:η2:η2-C60) (1) or its
lesser isocyanide-substituted complexes with appropriate amounts of (triphenylphosphino)benzylimine
(PhCH2NdPPh3). Compounds 3-5 have been characterized by spectroscopic (IR, MS, 1H and 13C NMR)
methods, cyclic voltammetry, and X-ray diffraction studies. Single-crystal X-ray diffraction studies reveal
that isomer 3a has two inequivalent equatorial isocyanide ligands as a cis,trans-1,2-isomer and isomer
4a has three equivalent equatorial isocyanide ligands as a 1,2,3-isomer with C3 symmetry. In compound
5, one benzyl isocyanide is axially coordinated to an osmium atom, whereas the other three benzyl
1
isocyanide ligands are equatorially coordinated to each osmium atom. H and 13C NMR data, however,
indicate that compound 3 exists as a mixture of 1,2- (3a) and 1,1-isomers (3b) in a ratio of 7:1, compound
4 as a mixture of 1,2,3- (4a) and 1,1,2-isomers (4b) in a ratio of 1:1, and compound 5, interestingly, as
a single species of a 1,1,2,3-isomer in solution. The cyclic voltammetric studies reveal that all the CVs
of 3-5 and related Os3(CO)8(CNCH2Ph)(µ3-η2:η2:η2-C60) (2) show four reversible redox waves that
correspond to a one-electron process each with the third and fourth waves overlapped within the
chlorobenzene solvent potential window. As more isocyanide ligands are coordinated in 2-5, all the
corresponding half-wave potentials are gradually shifted to more negative potentials, reflecting the electron-
donor property of the isocyanide ligand. Furthermore, C60-mediated electron delocalization from C60 to
the triosmium center takes place in the trianionic species of 2-5. The two isomers of 3 and 4 apparently
undergo an equivalent electrochemical process, respectively.
bonding mode can be modified by altering the coordination
sphere of the metal centers to which C60 is coordinated.4c,d,6,9
This has led to continued and vigorous studies of C60-metal
cluster chemistry, in which ligand substitution controls the
fullerene tuning in terms of electrochemical properties and
reactivities. This substitution chemistry is important in stabilizing
Introduction
The interaction between metal clusters and a carbon cluster
such as [60]fullerene (C60) is one of the most interesting topics
in the area of exohedral metallofullerene chemistry.1 In par-
ticular, we have been interested in C60-metal cluster complexes
in order to investigate and understand the effects of metal cluster
coordination on the chemical and physical properties of C60 and
the reactivities and electrochemical properties of these complexes2a
and ultimately to develop new electronic nanomaterials and
nanodevices.2b The C60-metal cluster complexes have been
dominated by a π-type C60-metal cluster interaction with the
µ3-η2:η2:η2-C60 bonding mode. This unique π-bonding nature
in C60-metal cluster complexes, surprisingly, results in both
remarkable thermal stability and strong electronic communica-
tion between C60 and metal cluster centers.2a Furthermore, this
electronic communication can be fine-tuned with various ligands
of different electronic properties coordinated on the metal cluster
center.2a We have also demonstrated that the µ3-η2:η2:η2-C60
(3) Song, H.; Lee, Y.; Choi, Z.-H.; Lee, K.; Park, J. T.; Kwak, J.; Choi,
M.-G. Organometallics 2001, 20, 3139-3144.
(4) (a) Song, H.; Lee, K.; Park, J. T.; Choi, M.-G. Organometallics 1998,
17, 4477-4483. (b) Song, H.; Lee, K.; Park, J. T.; Chang, H. Y.; Choi,
M.-G. J. Organomet. Chem. 2000, 599, 49-56. (c) Song, H.; Lee, K.; Choi,
M.-G.; Park, J. T. Organometallics 2002, 21, 1756-1758. (d) Song, H.;
Choi, J. I.; Lee, K.; Choi, M.-G.; Park, J. T. Organometallics 2002, 21,
5221-5228.
(5) (a) Lee, K.; Hsu, H.-F.; Shapley, J. R. Organometallics 1997, 16,
3876-3877. (b) Lee, K.; Shapley, J. R. Organometallics 1998, 17, 3020-
3026. (c) Babcock, A. J.; Li, J.; Lee, K.; Shapley, J. R. Organometallics
2002, 21, 3940-3946.
(6) (a) Lee, K.; Lee, C. H.; Song, H.; Park, J. T.; Chang, H. Y.; Choi,
M.-G. Angew. Chem., Int. Ed. 2000, 39, 1801-1804. (b) Lee, K.; Choi,
Z.-H.; Cho Y.-J.; Song, H.; Park, J. T. Organometallics 2001, 20, 5564-
5570.
(7) (a) Lee, G.; Cho, Y.-J.; Park, B. K.; Lee, K.; Park, J. T. J. Am. Chem.
Soc. 2003, 125, 13920-13921. (b) Park, B. K.; Miah, M. A.; Lee, G.; Cho,
Y.-J.; Lee, K.; Park, S.; Choi, M,-G.; Park, J. T. Angew. Chem., Int. Ed.
2004, 43, 1712-1724. (c) Park, B. K.; Miah, M. A.; Kang, H.; Lee, K.;
Cho, Y.-J.; Churchill, D. G.; Park, S.; Choi, M.-G.; Park, J. T. Organo-
metallics 2005, 24, 675-679.
(8) (a) Lee, K.; Song, H.; Kim, B.; Park, J. T.; Park, S.; Choi, M.-G. J.
Am. Chem. Soc. 2002, 124, 2872-2873. (b) Lee, K.; Choi, Y. J.; Cho,
Y.-J.; Lee, C. Y.; Song, H.; Lee, C. H.; Lee, Y. S.; Park, J. T. J. Am. Chem.
Soc. 2004, 126, 9837-9844.
(9) Song, H.; Lee, C. H.; Lee, K.; Park, J. T. Organometallics 2002, 21,
2514-2520.
* Corresponding author. E-mail: joontpark@kaist.ac.kr. Fax: + 82-42-
869-5826.
† KAIST.
‡ Korea University.
(1) (a) Stephens, A.; Green, M. L. H. AdV. Inorg. Chem. 1997, 44, 1-43.
(b) Balch, A. L.; Olmstead, M. M. Chem. ReV. 1998, 98, 2123-2165. (c)
Nakamura, E.; Isobe, H. Acc. Chem. Res. 2003, 36, 807-815.
(2) (a) Lee, K.; Song, H.; Park, J. T. Acc. Chem. Res. 2003, 36, 78-86.
(b) Cho, Y.-J.; Ahn, T. K.; Song, H.; Kim. K. S.; Lee, C. Y.; Seo, W. S.;
Lee, K.; Kim, S. K.; Kim, D.; Park, J. T. J. Am. Chem. Soc. 2005, 127,
2380-2381.
10.1021/om060566h CCC: $33.50 © 2006 American Chemical Society
Publication on Web 08/19/2006

Benzyl Isocyanide-Substituted C60-Triosmium Complexes
Organometallics, Vol. 25, No. 19, 2006 4635
Scheme 1a
Table 1. Selected Interatomic Distances (Å) and esd’s for
3a, 4a, and 5
3a
4a
5
Os(1)-Os(2)
Os(2)-Os(3)
Os(1)-Os(3)
Os(1)-C(100)
Os(1)-C(110)
Os(2)-C(200)
Os(3)-C(300)
Os(1)-C(1)
Os(1)-C(2)
Os(2)-C(3)
Os(2)-C(4)
Os(3)-C(5)
Os(3)-C(6)
C(1)-C(2)
2.8871(7)
2.9016(7)
2.9270(8)
1.98(2)
2.907(1)
2.903(1)
2.889(1)
1.97(2)
2.8880(6)
2.9189(6)
2.8951(7)
1.93(1)
1.98(1)
2.00(1)
1.98(1)
2.23(1)
2.29(1)
2.22(1)
2.29(1)
2.21(1)
2.27(1)
1.43(1)
1.49(2)
1.47(2)
1.48(1)
1.46(2)
1.47(2)
2.00(2)
1.97(2)
1.93(2)
2.23(1)
2.30(1)
2.28(1)
2.27(1)
2.24(1)
2.29(1)
1.47(2)
1.48(2)
1.41(2)
1.51(2)
1.42(2)
1.50(2)
1.14(2)
1.14(2)
1.12(2)
2.22(1)
2.27(1)
2.25(1)
2.23(1)
2.22(1)
2.28(1)
1.44(2)
1.47(2)
1.42(2)
1.49(2)
1.43(2)
1.47(2)
1.13(2)
1.11(2)
C(2)-C(3)
C(3)-C(4)
C(4)-C(5)
C(5)-C(6)
C(6)-C(1)
C(100)-N(1)
C(200)-N(2)
C(300)-N(3)
C(100)-N(100)
C(110)-N(110)
C(200)-N(200)
C(300)-N(300)
1.19(2)
1.14(2)
1.15(2)
1.18(2)
a Legend: (1) 1.2 equiv of RNdPPh3, room temperature, 12 h, 76%;
(2) 3 equiv of RNdPPh3, room temperature, 12 h, 70%; (3) 5 equiv of
RNdPPh3, 120 °C, 3 h, 70%; (4) 10 equiv of RNdPPh3, 132 °C, 3 h,
40%; (5) 1.5 equiv of RNdPPh3, room temperature, 12 h, 70%; (6)
1.2 equiv of RNdPPh3, 120 °C, 3 h, 70%; (7) 5 equiv of RNdPPh3,
132 °C, 3 h, 28%. R ) CH2Ph.
2 have already been reported in our earlier account.9 Compound
3 was prepared in 70% yield from the reaction of Os3(CO)9-
(µ3-η2:η2:η2-C60) (1) with 3 equiv of PhCH2NdPPh3 in chlo-
robenzene (CB) at room temperature for 12 h. Compound 3
can be alternatively prepared from the reaction of 2 with 1.5
equiv of PhCH2NdPPh3 in CB at room temperature for 12 h in
a similar yield. Thermolysis of 1 with 5 equiv of PhCH2Nd
PPh3 in CB at 120 °C for 3 h afforded compound 4 in 70%
yield, which can also be prepared alternatively from that of 3
with 1.2 equiv of PhCH2NdPPh3 in CB at 120 °C for 3 h in a
similar yield. Compound 5 was prepared in 40% yield along
with formation of 4 (25%) from the reaction of 1 with an excess
amount (10 equiv) of PhCH2NdPPh3 in refluxing CB for 3 h,
whereas thermal reaction of 4 with 5 equiv of PhCH2NdPPh3
in CB at 120 °C for 3 h produces compound 5 in low yield
(28%). All the yields for the formation of 3-5 were optimized
in this study. The substitution with the benzyl isocyanide ligand
is also possible by initial decarbonylation of the corresponding
starting materials with Me3NO/MeCN reagent for the prepara-
tion of 2-5, but the solid (triphenylphosphino)benzylimine
reagent is convenient to handle and usually gives better yields
without the unpleasant smell of the isocyanide reagent.
X-ray Crystal Structures of 3a, 4a, and 5. The overall
molecular geometry and the atomic labeling schemes of 3a, 4a,
and 5 are illustrated in Figures 6, 7, and 8, respectively. Their
structures are presented in Scheme 1. Selected interatomic
distances and angles of the three compounds are listed in Tables
1 and 2, respectively.
a great variety of C60-metal cluster complexes, which should
facilitate the future nanotechnological applications employing
these complexes. In our previous work, various phosphine ligand
substitution chemistry has been intensively investigated in
[Re3(µ-H)3],3 [Os3],4 [Ru5C],5 [Os5C],6 [Ir4],7 and [Rh6]8 cluster
systems to establish the general trend of the reactivity and
electrochemical properties of these complexes.
We have previously reported that the reaction of Os3(CO)9-
(µ3-η2:η2:η2-C60) (1) with (triphenylphosphino)benzylimine
(PhCH2NdPPh3) produces a benzyl isocyanide-substituted
product, Os3(CO)8(CNCH2Ph)(µ3-η2:η2:η2-C60) (2),9 in which
the µ3-η2:η2:η2-C60 ligand transforms into a new σ-π mixed
type µ3-η1:η2:η1-C60 ligand by insertion of a benzyl isocya-
nide ligand into an Os-Os bond. An isolobal rhenium analogue,
Re3(µ-H)3(CO)8(CNCH2Ph)(µ3-η2:η2:η2-C60),3 has the benzyl
isocyanide ligand occupying an axial site, and there is a unique
electrochemical effect of the isocyanide ligand in the trirhenium
system. Furthermore, the benzyl isocyanide ligand has been
successfully employed to significantly increase solubility of a
bisfullerene hexarhodium cluster complex, Rh6(CO)5(dppm)2-
(CNCH2Ph)(µ3-η2:η2:η2-C60)2,8 which otherwise could not be
characterized. As an extension of our ongoing efforts, we herein
report the synthesis, structures, and electrochemistry of a variety
of benzyl isocyanide-substituted C60-triosmium complexes,
Os3(CO)9-n(CNCH2Ph)n(µ3-η2:η2:η2-C60) (n ) 2 (3), 3 (4), and
4 (5)), from reactions of either Os3(CO)9(µ3-η2:η2:η2-C60) (1)
or its lesser isocyanide-substituted complexes with appropriate
amounts of PhCH2NdPPh3 and varying reaction time and
temperature, as shown in Scheme 1.
The overall structural features of 3a are similar to those of
isomorphous cis,trans-Os3(CO)7(PMe3)2(µ3-η2:η2:η2-C60).4b Two
inequivalent benzyl isocyanide ligands adopt the less steric-
ally hindered equatorial positions at the two adjacent osmium
atoms in a cis and trans configuration with respect to the
Os1-Os2 edge. The two Os(CO)2(CNCH2Ph) and one Os(CO)3
unit are twisted slightly, all in the same direction, so that the
three axial carbonyls are disposed in a propeller-like configu-
ration. Compound 4a has three equatorial benzyl isocyanide
ligands, which are arranged as far from the other two as possible
with a pseudo-C3 symmetry, as reported in Os3(CO)6(PMe3)3-
Results and Discussion
Syntheses of 3-5. Synthetic procedures for 2-5 are sum-
marized in Scheme 1. The synthesis and structure of compound

4636 Organometallics, Vol. 25, No. 19, 2006
Lee et al.
Table 2. Selected Interatomic Angles (deg) and esd’s for 3a,
4a, and 5
3a
4a
5
Os(2)-Os(1)-Os(3)
Os(1)-Os(2)-Os(3)
Os(2)-Os(1)-C(100)
Os(3)-Os(1)-C(100)
Os(1)-Os(2)-C(200)
Os(3)-Os(2)-C(200)
Os(2)-Os(3)-C(300)
Os(1)-Os(3)-C(300)
Os(2)-Os(1)-C(110)
C(2)-C(1)-C(6)
59.869(19)
60.748(18)
149.6(5)
90.9(5)
91.7(5)
152.4(5)
60.13(2)
59.63(2)
144.8(5)
84.9(5)
80.7(5)
139.9(5)
94.2(6)
60.627(16)
59.806(16)
145.9(5)
85.9(5)
165.3(3)
130.5(3)
84.6(4)
154.2(6)
143.1(4)
85.7(4)
119.4(11)
120.4(11)
119.3(10)
121.4(11)
118.7(11)
120.6(11)
174.2(18)
175.3(15)
116.6(10)
120.0(11)
122.3(12)
118.8(11)
119.4(11)
122.6(11)
176.3(18)
177.0(15)
176.2(18)
120.5(10)
120.7(9)
118.8(9)
119.8(9)
120.3(10)
119.9(9)
C(1)-C(2)-C(3)
C(2)-C(3)-C(4)
C(3)-C(4)-C(5)
C(4)-C(5)-C(6)
C(5)-C(6)-C(1)
Os(1)-C(100)-N(1)
Os(2)-C(200)-N(2)
Os(3)-C(300)-N(3)
Os(1)-C(100)-N(100)
Os(1)-C(110)-N(110)
Os(2)-C(200)-N(200)
Os(3)-C(300)-N(300)
Figure 1. 1H NMR spectra (400 MHz, CDCl3, 298 K, benzylic
region) of (a) 3, (b) 4, and (c) 5.
176.2(13)
177.1(12)
175.5(11)
176.7(11)
(µ3-η2:η2:η2-C60).4b In compound 5, a benzyl isocyanide ligand
is coordinated on the Os1 atom in the axial position, whereas
the other three benzyl isocyanide ligands are equatorially bonded
to the Os1, Os2, and Os3 centers, respectively. The equatorially
bonded benzyl isocyanide on the Os1 atom is cis and trans to
that on the Os3 atom with respect to the Os1-Os3 edge and
trans and trans to that on the Os2 atom with respect to the
Os1-Os2 edge. The two equatorial benzyl isocyanide ligands
on the Os2 and Os3 centers are, however, unusually cis and cis
with respect to the Os2-Os3 edge, which seems to be possible
because of the relatively long and slim shape of the benzyl
isocyanide ligand. The bonding nature between the triosmium
framework and C60 in the starting material, Os3(CO)9(µ3-η2:
η2:η2-C60) (1), is retained during the formation of 3a, 4a, and
5. All other geometric features are within the expected ranges.
The average Os-Os bond lengths of 3a-5 (2.9052(7) Å for
3a, 2.900(1) Å for 4a, and 2.9001(6) Å for 5) are slightly
elongated compared to that for Os3(CO)12 (2.877(3) Å), presum-
ably due to bulky ligands in 3a-5. The C6 ring of the C60 moiety
is parallel with the Os3 plane in 3a-5 (dihedral angles: 0.4°
for 3a, 0.5° for 4a, and 0.6° for 5). The Os-CO distances range
from 1.88(2) to 1.96(2) Å for 3a, from 1.86(2) to 1.91(2) Å for
4a, and from 1.87(1) to 1.91(1) Å for 5. The C-O bond lengths
lie between 1.09(2) and 1.16(2) Å for 3a (av 1.13(2) Å),
1.13(2) and 1.18(2) Å for 4a (av 1.16(2) Å), and 1.12(2) and
1.17(2) Å for 5 (av 1.15(2) Å). The average Os-CNCH2Ph
bond distances in 3a, 4a, and 5 are 1.99(2), 1.96(2), and
1.97(1) Å, respectively. The average C-N bond lengths in 3a,
4a, and 5 are 1.12(2), 1.13(2), and 1.16(2) Å, respectively.
Characterization of 3-5. The new compounds 3-5 are
soluble in various solvents such as CS2, dichloromethane,
toluene, and chlorinated benzenes: the benzyl isocyanide ligand
generally increases solubility of these complexes compared to
their carbonyl and phosphine derivatives. All the compounds
were formulated on the basis of the molecular ion isotope
patterns (m/z (highest peak): 1722 (3); 1811 (4); 1900 (5)) in
the positive ion FAB mass spectra and the microanalytical data.
The IR spectra of 3-5 exhibit terminal NC stretching bands
in the range 2183-2165 cm-1 with intensities increasing as 5
> 4 > 3 (see Figure S2 in the Supporting Information). The
terminal CO stretching bands appear in the typical range of
2047-1950 cm-1 and shift to the low-energy region by ca. 20
cm-1/ligand as more benzyl isocyanide ligands are coordinated,
Figure 2. (a) 13CO-enriched 13C NMR spectrum (100 MHz, CDCl3,
298 K, carbonyl region) of 3. (b) 13C NMR spectrum (100 MHz,
CDCl3, 298 K, carbonyl region) of 4. (c) 13C NMR spectrum (100
MHz, CDCl3, 298 K, carbonyl region) of 5.
reflecting the stronger electron-donor effect of the isocyanide
ligand relative to the carbonyl ligand.
1
The H and 13C NMR spectra of complexes 3-5 at room
temperature are shown in Figures 1 and 2, respectively. Both
NMR data of 3 appear as two sets of resonances in an intensity
ratio of 7:1, implying that 3 exists as two isomers in solution.
1
The H NMR spectrum of 3 (Figure 1a) at room temperature
reveals an overlapped AB pattern at δ 5.08 (JHH ) 16.4 Hz,
denoted as 9) for 3a and a small singlet at δ 5.21 (denoted as
0) for 3b, for the benzylic protons of the two benzyl isocyanide
ligands, respectively. The overlapped AB pattern is ascribed to
the diastereotopic benzylic protons of 3a. The 13C NMR
spectrum (carbonyl region, Figure 2a) of 13CO-enriched 3 shows
three major resonances at δ 182.2, 181.6, and 179.1 in an
intensity ratio of 2:2:3 (denoted as 9) for 3a and two minor
resonances at δ 181.3 and 179.3 in an intensity ratio of 1:6
(denoted as 0) for 3b. The major isomer is identified as an
eq,eq-1,2-isomer (3a), which is observed in the solid state. The
two low-field singlet resonances at δ 182.2 and 181.6 with an
equal intensity are due to the equilibration of an axial carbonyl
on one osmium center with an equatorial carbonyl on the other

Benzyl Isocyanide-Substituted C60-Triosmium Complexes
Organometallics, Vol. 25, No. 19, 2006 4637
Scheme 2
Scheme 3
on the two Os(CO)2(CNCH2Ph) moieties due to the well-
established coupled restricted 3-fold rotations of the ligands on
the two osmium moieties,4b,10 as presented in Scheme 2. The
high-field singlet resonance at δ 179.1 with an intensity 3 is
attributed to the three equivalent carbonyls by a fast 3-fold
rotation on the Os(CO)3 center. Consequently, the two benzyl
isocyanide ligands in 3a become equivalent: one AB pattern
(δ 5.08) and one benzyl isocyanide carbon signal (δ 132.2 (2C,
NC) and 48.9 (2C, CH2)) appear in the 1H and 13C NMR spectra,
respectively. Isomorphous structures with similar fluxional
processes have been previously reported in cis,trans-Ru3(CO)7-
(PPh3)2(µ3-η2:η2:η2-C60)10 and cis,trans-Os3(CO)7(PMe3)2(µ3-
η2:η2:η2-C60) (7).4b The minor signals are attributed to the
1
ax,eq-1,1-isomer (3b), as shown in Scheme 1. The small H
NMR resonance at δ 5.21 is due to the proton signals of the
two equivalent isocyanide ligands based on the 3-fold rotation
of the Os(CO)(CNCH2Ph)2 center. The two 13C NMR signals
at δ 181.3 and 179.3 in an intensity ratio of 1:6 are assigned to
one carbonyl on the Os(CO)(CNCH2Ph)2 center and the other
six carbonyls due to fast 3-fold rotations on the two Os(CO)3
centers, respectively. The variable-temperature (VT) 13C NMR
spectra of 3 (CS2 + CD2Cl2 as an internal reference, see Figure
S2 in the Supporting Information) reveal that the resonance at
δ 179.3 due to 3b with an intensity of 6 becomes broad and is
finally resolved into two signals (δ 180.3 and 178.3) at 183 K.
This observation is consistent with the proposed ax,eq-structure
for 3b, where the two Os(CO)3 centers become equivalent in
the high-temperature limiting spectrum. The other possible
structure of 3b with eq,eq-configuration is eliminated, because
the signal at δ 179.3 would remain sharp at low temperatures
due to a Cs symmetric nature of 3b that undergoes fast 3-fold
rotations of the two Os(CO)3 centers. The 13C NMR (C60 region)
spectrum of 3a at room temperature shows 32 resonances (see
Scheme 3), as shown in Figure 3, which is consistent with the
idealized Cs symmetric nature of 3a in solution. The spectrum
contains 29 sp2 resonances (δ 158.2-142.4 in Figure 3a)
comprising 25 and 4 (δ 152.3, 143.7, 143.0 (1C + 2C,
overlapped), and 142.8, denoted as b) lines in an intensity ratio
of 2:1 and three sp3 carbon resonances of a-a′′ (δ 64.1, 62.3,
and 54.9 in Figure 3b) with an intensity of 2. The C60 carbon
resonances of 3b are too weak to be clearly observed.
with C3 symmetry observed in the solid state, in which all three
isocyanide ligands are equivalent and three axial and three
equatorial carbonyl ligands become equivalent by a 3-fold
rotation on each osmium center. The large resonance at δ 183.7,
therefore, is assigned to the six carbonyl ligands on the three
Os(CO)2(CNCH2Ph) centers of 4a. A similar structure that
undergoes fluxional processes identical to 4a was previously
reported for Os3(CO)6(PMe3)3(µ3-η2:η2:η2-C60),4b which, yet,
exists as a single eq,eq,eq-1,2,3-isomer. The other resonances
for 4b are consistent with the structure of an ax,eq,eq-1,1,2-
isomer (4b), as shown in Scheme 1. Three resonances at δ 185.4,
183.5, and 183.1 each with an intensity of 1 are due to a
carbonyl on the Os(CO)(CNCH2Ph)2 moiety and two inequiva-
lent carbonyls on the Os(CO)2(CNCH2Ph) center, although
definitive assignments cannot be made. The other resonance at
δ 180.9 with an intensity of 3 is due to three carbonyls on the
Os(CO)3 center, which undergoes a fast 3-fold rotation at room
temperature. Accordingly, three distinct resonances (δ 133.0
(1C, NC), 133.0 (1C, NC), 132.5 (1C, NC); 48.9 (1C, CH2),
48.7 (1C, CH2), and 48.6 (1C, CH2)) are observed for the three
inequivalent benzyl isocyanide ligands of 4b. The 13C NMR
spectrum (C60 region) of 4a reveals 12 resonances at δ 159.1
(6C), 153.2 (3C), 148.2 (6C), 146.1 (6C), 145.4 (6C), 144.5
(6C), 144.0 (3C), 143.9 (6C), 143.1 (6C), 143.0 (3C), and 142.6
(3C) for sp2 carbon atoms (Figure 4a) and 61.0 (6C) for sp3
carbon atoms (Figure 4b). The four resonances at δ 153.2, 144.0,
143.0, and 142.6 (denoted as b in Figure 4a) appear with about
half of the intensity of the other eight resonances. This
observation is consistent with an idealized C3V symmetry of 4a
in solution at room temperature, which contains 12 types of
carbon atoms of the C60 moiety, i.e., three carbon atoms each
for d, e, h, and i types (bold lines) and six carbon atoms each
for a, b, c, f, g, k, j, and l types, as analyzed in Scheme 4. The
six carbon atoms (a, bold line, sp3 carbon) coordinated to the
osmium atoms appear at δ 61.0 as a singlet (Figure 4b). The
small peaks observed in Figure 4a are due to 54 C60 sp2 carbon
atoms of 4b, but six resonances for six inequivalent C60 sp3
carbon atoms are clearly observed at δ 69.7, 66.3, 60.6, 59.6,
55.8, and 51.5 (denoted as O) in Figure 4b.
The NMR data of 4 also appear as two sets of resonances of
1
4a and 4b in an intensity ratio of 1:1. The H NMR spectrum
of 4 (Figure 1b) exhibits a large singlet at δ 5.01 (denoted as
b) for 4a and two singlets at δ 5.21 and 5.13 and an AB pattern
at δ 5.00 (JHH ) 16.4 Hz) in a ratio of 1:1:1 (denoted as O) for
4b, because of the benzylic protons of the three benzyl
isocyanide ligands, respectively. These data indicate that 4a has
three equivalent isocyanide ligands and 4b contains three
inequivalent isocyanide ligands. The 13C NMR spectrum (car-
bonyl region, Figure 2b) of 4 reveals a large resonance at δ
183.7 (denoted as b) for 4a and four small resonances at δ
185.4, 183.5, 183.1, and 180.9 in an intensity ratio of 1:1:1:3
(denoted as O) for 4b. On the basis of these NMR data, the
former resonances are assigned to an eq,eq,eq-1,2,3-isomer (4a)
1
The H NMR spectrum of 5 (Figure 1c) shows two singlets
at δ 4.94 and 5.12 for the benzylic protons of the four isocyanide
ligands in an intensity ratio of 1:1, indicating that the four
isocyanide ligands are equivalent pairwise. The 13C NMR
(10) Hsu, H.-F.; Shapley, J. R. J. Organomet. Chem. 2000, 599, 97-
105.

4638 Organometallics, Vol. 25, No. 19, 2006
Lee et al.
Figure 3. 13C NMR spectrum (100 MHz, CDCl3, 298 K, C60 region) of 3.
Figure 4. 13C NMR spectrum (100 MHz, CDCl3, 298 K, C60 region) of 4.
Scheme 4
exists as a single isomer of ax,eq,eq,eq-1,1,2,3-configuration
in solution, as shown in Scheme 1, adopting the structure found
in the solid state. The low-field resonance at δ 186.2 with an
intensity of 1 is obviously assigned to a carbonyl ligand on the
Os(CO)(CNCH2Ph)2 center and the other two high-field reso-
nances at δ 185.4 and 184.5 each with an intensity of 2 to
two axial and two equatorial carbonyls on the two Os(CO)2-
(CNCH2Ph) centers. These NMR data indicate that only the
unique Os(CO)(CNCH2Ph)2 center undergoes a fast 3-fold
rotation, leading to a Cs symmetry of this molecule at room
temperature. As a result, two types of resonances each with an
intensity of 2 due to benzyl isocyanide ligands are also observed
in the 13C NMR spectrum (δ 133.5 (2C, NC), 133.0 (2C, NC);
48.7 (2C, CH2), 48.5 (2C, CH2)). The 13C NMR spectrum (C60
region) is consistent with a Cs symmetric nature of 5, as
illustrated for compound 3a in Scheme 2, which comprises 29
sp2 carbon resonances in the region of δ 162.5-142.6 (sp2
carbon resonances (d, e, h, and i) are denoted as b in Figure
5a) and three sp3 carbon resonances at δ 67.4, 60.2, and 57.9
(Figure 5b).
spectrum (carbonyl region, Figure 2c) of 5 reveals three
resonances at δ 186.2, 185.4, and 184.5 in an intensity ratio of
1:2:2. Both NMR data imply that compound 5, interestingly,
The carbonyl resonances, apparently, shift to lower fields as
the number of benzyl isocyanide ligands on the metal atoms
increases, as clearly seen in 3a (δ 182.2 and 181.6), 3b (δ

Benzyl Isocyanide-Substituted C60-Triosmium Complexes
Organometallics, Vol. 25, No. 19, 2006 4639
Figure 5. 13C NMR spectrum (100 MHz, CDCl3, 298 K, C60 region) of 5.
181.3), 4b (δ 185.4, 183.5, and 183.1), and 5 (δ 186.2). A
similar trend was also reported for analogous phosphine-
substituted complexes.4b In phosphine-substituted C60-trios-
mium complexes, only the eq,eq-1,2-isomer and the eq,eq,eq-
1,2,3-isomer have been observed in Os3(CO)9-n(PMe3)n(µ3-η2:
η2:η2-C60) (n ) 2 and 3) compounds,4b yet the tetrasubsti-
tuted compound is not known. In benzyl isocyanide-substituted
C60-triosmium complexes of this work, however, the eq,eq-1,2-
isomer (3a), ax,eq-1,1-isomers (3b), eq,eq,eq-1,2,3-isomer (4a),
ax,eq,eq-1,1,2-isomer (4b), and tetrasubstituted ax,eq,eq,eq-
1,1,2,3-compound 5 have been characterized. The M-CO bond
strength is known to become stronger as more electron-donating
ligands are substituted on the metal center due to the increased
MfCO back-donation. The carbonyl activation, therefore, is
more facile with the less-electron-donating isocyanide ligand
relative to the more-electron-donating phosphine ligand, which
seems to facilitate the formation of higher substitution products
in isocyanide-substituted complexes. Compound 5, interestingly,
exists as a single isomer with the structure found in the solid
state (vide infra). For the 1,1- (3b) and 1,1,2-isomer (4b), the
other possible structural isomers with eq,eq- and eq,eq,eq-
configuration of the two isocyanide ligands on the Os(CO)-
(CNCH2Ph)2 centers were eliminated, because the ax,eq-
configuration of 3b was clearly proved by the VT 13C NMR
studies of 3 (Figure S2). The two possible structural isomers of
4b cannot be differentiated by VT 13C NMR studies of 4, since
similar patterns of the VT 13C NMR are expected for the two
possible isomers. Moreover, the ax,eq-configuration was also
observed in the structurally characterized ax,eq,eq,eq-1,1,2,3-
isomer (5) and thus seems to be a favorable configuration for
the 1,1-substituted isomer. The two isomers of 3 or 4 are
apparently formed during syntheses and are not interconvertible,
as indicated by NMR studies. We have not been successful as
of yet in separating the two isomers of 3 or 4 and in obtaining
crystal structures of 3b and 4b.
Figure 6. Molecular structure with atomic labeling scheme
for 3a.
Os3(CO)6(PMe3)3(µ3-η2:η2:η2-C60) (8), are provided in Table 3.
All the CVs of 2-5 reveal four reversible redox waves that
correspond to a one-electron process each with the third and
fourth waves overlapped (av ∆Ep1 ) 100 mV, ∆Ep2 ) 85 mV,
and ∆Ep3 ) 103 mV). The two isomers of 3 and 4 apparently
undergo equivalent electrochemical process, respectively. The
general features of the CVs of 2-5 are similar to those
previously reported for Os3(CO)8(PMe3)(µ3-η2:η2:η2-C60) (6),4a
as listed in Table 3. Electron delocalization from C60 to the
triosmium cluster in 6 has been previously proposed to occur
in the 63- state based on the overlap of the third and fourth
waves.4a As more isocyanide ligands are coordinated in 2-5,
all the corresponding half-wave potentials are gradually shifted
to more negative potentials (ca. 80 mV), which reflects the
electron-donor nature of the isocyanide ligand. The fact that
the third redox couples (-1.93, -2.09, and -2.34 V) of 6, 7,
and 8 appear at more negative potentials compared to those
(-1.79, -1.84, and -1.91 V) of 2, 3, and 4 proves that the
trimethylphosphine ligand is more electron-donating than the
benzyl isocyanide ligand. Moreover, in contrast to 3, the bis-
Electrochemical Studies of 2, 3, 4, and 5. Electrochemical
properties of complexes 2-5 have been examined by the cyclic
voltammetric method in CB solutions with tetrabutylammonium
perchlorate as the supporting electrolyte. Cyclic voltammograms
(CVs) of 2-5 are shown in Figure 9. Half-wave potentials (E1/2
)
of 2-5, together with free C60, Os3(CO)8(PMe3)(µ3-η2:
η2:η2-C60) (6), Os3(CO)7(PMe3)2(µ3-η2:η2:η2-C60) (7), and

4640 Organometallics, Vol. 25, No. 19, 2006
Lee et al.
Figure 9. Cyclic voltammograms of 2, 3, 4, and 5 in dry,
deoxygenated chlorobenzene (0.1 M [(n-Bu)4N][ClO4]). Scan rate
) 5 mV/s.
380 mV for 5). This electron delocalization from C60 to the
metal cluster is implied by the two close redox waves and well
precedented in C60-metal cluster complexes.3,4a,11 Although
electron-donating isocyanide ligands are substituted in 2-5,
interestingly, the fourth electron addition to C60 in 23-, 33-
4
,
3-, and 53- is still easier compared to that in free C603- due to
Figure 7. Molecular structure with atomic labeling scheme for
4a.
the electron delocalization from the C60 moiety to the triosmium
center.2a,11
Concluding Remarks
In the present benzyl isocyanide substitution chemistry of
Os3(CO)9(µ3-η2:η2:η2-C60) (1), we observed formation of
Os3(CO)9-n(CNCH2Ph)n(µ3-η2:η2:η2-C60) (n ) 2 (3), 3 (4), and
4 (5)) up to tetrasubstitution, in contrast to the phosphine sub-
stitution chemistry, due to the less-electron-donating effect of
the isocyanide ligand relative to the phosphine ligand. In bis-
and tris-substituted benzyl isocyanide complexes, two isomers
(3a/3b and 4a/4b) have been observed in solution, whereas only
a single isomer has been reported to exist in analogous phos-
phine-substituted complexes. All the substitution reactions
proceed under mild conditions with the solid (triphenylphos-
phino)benzylimine reagent, which is very convenient to handle
and generally results in high yields, especially without the
unpleasant smell of the isocyanide reagent. The slim-shaped
isocyanide ligand is known to adopt an axial position on the
triosmium framework,12 which accounts for the existence of two
isomers of 3 and 4 and the diversity of the benzyl isocyanide
substitution chemistry. In particular, electrochemical prop-
erties of the isocyanide derivatives are quite different from those
of the phosphine derivatives, which implies that investiga-
tion of the substitution chemistry is very important to prepare
C60-metal cluster complexes with various electronic properties
for future applications in electronic nanomaterials and device
fabrication.
Figure 8. Molecular structure with atomic labeling scheme for 5.
trimethylphosphine-substituted compound 74a exhibits three
reversible one-electron redox waves without electron delocal-
ization to the metal center due to the strong electron-donating
effect of the two trimethylphosphine ligands. These are clear
examples that the electrochemical properties of these C60-metal
cluster complexes can be fine-tuned by the kind and number of
the attached ligands on the metal centers. The third and fourth
reductions of 2-5 take place at the same potentials, which are
even more positive (-1.79 for 2, -1.84 for 3, -1.91 for 4, and
-1.99 V for 5) than the fourth reduction of free C60 at -2.38
V. These overlaps of the third and fourth waves in 2-5 support
Experimental Section
General Comments. All the reactions were carried out under a
nitrogen atmosphere with the use of standard Schlenk techniques.
the conclusion that the electron density of C60 in 23-, 33-, 43-
,
(11) Park, J. T.; Cho, J.-J.; Song, H.; Jun, C.-S.; Son, Y.; Kwak, J. Inorg.
Chem. 1997, 36, 2698-2699.
(12) (a) Mays, M. J.; Gavens, P. D. J. Chem. Soc., Dalton Trans. 1980,
911-917. (b) Lu, K.-L.; Chen, C.-C.; Lin, Y.-W.; Hong, F.-E.; Gau, H.-
M.; Gan, L.-L.; Luoh, H.-D. J. Organomet. Chem. 1993, 453, 263-267.
and 53- is significantly delocalized to the metal cluster center,
and thus large anodic shifts of the fourth reductions relative to
C60 occur (590 mV for 2, 540 mV for 3, 470 mV for 4, and

Benzyl Isocyanide-Substituted C60-Triosmium Complexes
Organometallics, Vol. 25, No. 19, 2006 4641
Table 3. Half-Wave Potentials (E1/2 vs E°Fc/Fc+) of Free C60, 2, 3, 4, 5, 6, 7, and 8
0/-1
-1/-2
-2/-3
-3/-4
compound
E1/2
E1/2
E1/2
E1/2
solvent
ref
C60
-1.06
-1.06
-1.12
-1.19
-1.30
-1.08
-1.06
-1.13
-1.28
-1.43
-1.42
-1.46
-1.54
-1.65
-1.46
-1.42
-1.48
-1.66
-1.91
-2.38
CB
CB
CB
CB
3
Os3(CO)8(CNCH2Ph)(µ3-η2:η2:η2-C60) (2)
Os3(CO)7(CNCH2Ph)2(µ3-η2:η2:η2-C60) (3)
Os3(CO)6(CNCH2Ph)3(µ3-η2:η2:η2-C60) (4)
Os3(CO)5(CNCH2Ph)4(µ3-η2:η2:η2-C60) (5)
C60
-1.79
-1.84
-1.91
-1.99
this work
this work
this work
this work
4a
4a
4a
this work
CB
-1.90
-1.93
-2.09
-2.34
-2.38
-1.95
DCB
DCB
DCB
CB
Os3(CO)8(PMe3)(µ3-η2:η2:η2-C60) (6)
Os3(CO)7(PMe3)2(µ3-η2:η2:η2-C60) (7)
Os3(CO)6(PMe3)3(µ3-η2:η2:η2-C60) (8)
Solvents were dried over the appropriate drying agents and distilled
immediately before use. C60 (99.5%, SES research) was used
without further purification. PhCH2NdPPh3,13 Os3(CO)9(µ3-η2:
η2:η2-C60),14 and Os3(CO)6(PMe3)3(µ3-η2:η2:η2-C60)4b were prepared
according to the literature methods. Carbon-13 CO enriched
complexes were prepared by using Os3(*CO)12 (ca. 50% enrich-
ment).15 Preparative thin-layer chromatography (TLC) plates were
prepared with silica gel GF254 (type 60, E. Merck).
the solvent and purification by preparative TLC (CS2/CH2Cl2,
10:1) afforded a mixture of two isomeric compounds, 4a and 4b
(41.1 mg, 0.0227 mmol, 70%, Rf ) 0.6), as a brownish-green
solid: IR (CH2Cl2) ν(CO) 2022 (vs), 1993 (s), 1960 (m), 1936 (w);
ν(NC) 2175 (s) cm-1; MS (FAB+) m/z 1811 (M+). Anal. Calcd
for C90H21N3O6Os3: C, 59.69; H, 1.17; N, 2.32. Found: C, 58.21;
H, 1.57; N, 2.37. Compound 4a: 1H NMR (400 MHz, CDCl3, 298
K) δ 7.33-7.22 (m, 15H, Ph), 5.01 (s, 6H, CH2); 13C{1H} NMR
(100 MHz, CDCl3, 298 K) carbonyl carbon; δ 183.7 (6CO), C60
sp2 carbon; 159.1 (6C), 153.2 (3C), 148.2 (6C), 146.1 (6C), 145.4
(6C), 144.5 (6C), 144.0 (3C), 143.9 (6C), 143.1(6C), 143.0 (3C),
142.6 (3C), C60 sp3 carbon; 61.0 (6C), benzyl isocyanide carbon;
132.6 (3C, NC), 129.1-126.9 (18C, Ph), 48.6 (3C, CH2). Com-
pound 4b: 1H NMR (400 MHz, CDCl3, 298 K) δ 7.33-7.22 (m,
15H, Ph), 5.21 (s, 2H, CH2), 5.13 (s, 2H, CH2), 5.04 (d, 1H, JHH
) 16.4 Hz, CH2), 4.98 (d, 1H, JHH ) 16.4 Hz, CH2); 13C{1H} NMR
(100 MHz, CDCl3, 298 K), carbonyl carbon; δ 185.4 (1CO), 183.5
(1CO), 183.1 (1CO), 180.9 (3CO), C60 sp2 carbon; 161.1-142.0
(54C), C60 sp3 carbon; 69.7 (1C), 66.3 (1C), 60.6 (1C), 59.6 (1C),
55.8 (1C), 51.5 (1C), benzyl isocyanide carbon; 133.0 (1C, NC),
133.0 (1C, NC), 132.5 (1C, NC), 129.1-126.9 (18C, Ph), 48.9 (1C,
CH2), 48.7 (1C, CH2), 48.6 (1C, CH2). 4a:4b ) 1:1 by integration
of NMR signals.
Infrared spectra were obtained on a Bruker EQUINOX-55
FT-IR spectrophotometer. 1H (400 MHz) and 13C (100 MHz) NMR
spectra were recorded on a Bruker AVANCE-400 spectrometer.
Positive ion FAB mass spectra (FAB+) were obtained by the staff
of the Korea Basic Science Institute, and all m/z values were
referenced to 192Os. Elemental analyses were provided by the staff
of the Energy and Environment Research Center at KAIST.
Preparation of Os3(CO)7(CNR)2(µ3-η2:η2:η2-C60) (3). Method
A. A chlorobenzene solution (50 mL) of Os3(CO)9(µ3-η2:η2:η2-C60)
(1) (50.0 mg, 0.0324 mmol) and PhCH2NdPPh3 (3 equiv, 35.7
mg, 0.0971 mmol) was stirred for 12 h at room temperature.
Evaporation of the solvent and purification by preparative TLC
(CS2) afforded a mixture of two isomeric compounds, 3a and 3b
(39.0 mg, 0.0227 mmol, 70%, Rf ) 0.4), as a brown solid: IR
(CH2Cl2) ν(CO) 2047 (vs), 2015 (s), 2002 (m), 1982 (w); ν(NC)
2183 (m) cm-1; MS (FAB+) m/z 1722 (M+). Anal. Calcd for
C83H14N2O7Os3: C, 57.90; H, 0.82; N, 1.63. Found: C, 56.53; H,
0.92; N, 1.78. Compound 3a: 1H NMR (400 MHz, CDCl3, 298 K)
δ 7.33-7.24 (m, 10H, Ph), 5.08 (an overlapped AB pattern, 4H,
JHH ) 16.4 Hz, CH2); 13C{1H} NMR (100 MHz, CDCl3, 298 K,)
carbonyl carbon; δ 182.2 (2CO), 181.6 (2CO), 179.1 (3CO), C60
sp2 carbon; δ 158.2 (2C), 157.6 (2C), 155.8 (2C), 152.5 (2C), 152.3
(1C), 148.1 (2C), 148.1 (2C), 147.9 (2C), 146.3 (2C), 146.2 (2C),
146.1 (2C), 145.2 (2C), 145.1 (2C), 145.0 (2C), 144.6 (2C), 144.4
(2C), 144.3 (2C), 144.2 (2C), 144.1 (2C), 144.0 (2C), 143.8 (2C),
143.7 (1C), 143.1 (2C), 143.0 (2C+1C), 142.8 (1C), 142.5 (2C),
142.4 (2C), C60 sp3 carbon; 64.1 (2C), 62.3 (2C), 54.9 (2C), benzyl
isocyanide carbon; 132.2 (2C, NC), 129.2-127.0 (12C, Ph), 48.9
(2C, CH2). Compound 3b: 1H NMR (400 MHz, CDCl3, 298 K) δ
7.33-7.24 (m, 10H, Ph), 5.21 (s, 4H, CH2); 13C{1H} NMR (100
MHz, CDCl3, 298 K) δ 181.3 (1CO), 179.3 (6CO). Other carbon
signals too weak to be observed. 3a:3b ) 7:1 by integration of
NMR signals.
Method B. A chlorobenzene solution (50 mL) of 3 (50.0 mg,
0.0290 mmol) and PhCH2NdPPh3 (1.2 equiv, 14.3 mg, 0.0389
mmol) was heated at 120 °C for 3 h. Evaporation of the solvent
and purification by preparative TLC (CS2/CH2Cl2, 10:1) produced
a mixture of two isomeric compounds, 4a and 4b (36.8 mg, 0.0203
mmol, 70%, Rf ) 0.6), as a brownish-green solid.
Preparation of Os3(CO)5(CNR)4(µ3-η2:η2:η2-C60) (5). Method
A. A chlorobenzene solution (50 mL) of Os3(CO)9(µ3-η2:η2:η2-C60)
(1) (50.0 mg, 0.0324 mmol) and PhCH2NdPPh3 (10 equiv, 119.0
mg, 0.3240 mmol) was heated at reflux for 3 h. Evaporation of the
solvent and purification by preparative TLC (CS2/CH2Cl2, 10:1)
afforded compound 5 (24.6 mg, 0.0130 mmol, 40%, Rf ) 0.4) as
a green solid. Compound 4 (14.7 mg, 0.0081 mmol, 25%) was also
produced by this method. Compound 5: IR (CH2Cl2) ν (CO) 2000
(s), 1976 (s), 1948 (w), 1915 (w); ν(NC) 2165 (vs) cm-1; 1H NMR
(400 MHz, CDCl3, 298 K) δ 7.28-7.23 (m, 20H, Ph), 5.12 (s, 4H,
CH2), 4.94 (s, 4H, CH2); 13C{1H} NMR (100 MHz, CDCl3, 298
K) carbonyl carbon; δ 186.2 (1CO), 185.4 (2CO), 184.5 (2CO),
C60 sp2 carbon; 162.5 (2C), 160.5 (2C), 159.4 (2C), 154.0 (1C),
153.7 (2C), 148.5 (2C), 148.2 (4C), 146.2 (2C), 146.1 (2C), 146.0
(2C), 145.6 (2C), 145.5 (2C), 145.4 (2C), 144.7 (2C), 144.6 (2C),
144.5 (2C), 144.4 (1C), 144.1 (2C), 144.0 (2C), 143.8 (2C), 143.7
(2C), 143.5 (2C), 143.3 (2C), 143.1 (1C), 143.0 (2C), 142.9 (2C),
142.7 (2C), 142.6 (1C), C60 sp3 carbon; 67.4 (2C), 60.2 (2C), 57.9
(2C), benzyl isocyanide carbon; 133.5 (2C, NC), 133.0 (2C, NC),
129.0∼126.9 (24C, Ph), 48.7 (2C, CH2), 48.5 (2C, CH2); MS
(FAB+) m/z 1900 (M+). Anal. Calcd for C97H28N4O5Os3: C, 61.32;
H, 1.49; N, 2.95. Found: C, 61.41; H, 1.63; N, 3.08.
Method B. A chlorobenzene solution (50 mL) of 2 (50.0 mg,
0.0306 mmol) and PhCH2NdPPh3 (1.5 equiv, 16.9 mg, 0.0459
mmol) was stirred for 12 h at room temperature. Evaporation of
the solvent and purification by preparative TLC (CS2) gave a
mixture of two isomeric compounds, 3a and 3b (36.9 mg, 0.0214
mmol, 70%, Rf ) 0.4), as a brown solid.
Preparation of Os3(CO)6(CNR)3(µ3-η2:η2:η2-C60) (4). Method
A. A chlorobenzene solution (50 mL) of Os3(CO)9(µ3-η2:η2:η2-C60)
(1) (50.0 mg, 0.0324 mmol) and PhCH2NdPPh3 (5 equiv, 59.5
mg, 0.1620 mmol) was heated at 120 °C for 3 h. Evaporation of
Method B. A chlorobenzene solution (50 mL) of 4 (50.0 mg,
0.0276 mmol) and PhCH2NdPPh3 (5 equiv, 50.7 mg, 0.138 mmol)
was heated at reflux for 3 h. Evaporation of the solvent and
purification by preparative TLC (CS2/CH2Cl2, 10:1) gave compound
5 (14.7 mg, 0.0077 mmol, 28%, Rf ) 0.4) as a green solid.
(13) Lee, K.-W.; Singer, L. A. J. Org. Chem. 1974, 39, 3780-3781.
(14) Lee, C. Y.; Song, H.; Lee, K.; Park, B. K.; Park, J. T. Inorg. Synth.
2004, 34, 225-228.
(15) Clauss, A. D.; Tachikawa, M.; Shapley, J. R.; Pierpont, C. G. Inorg.
Chem. 1981, 20, 1528-1533.

4642 Organometallics, Vol. 25, No. 19, 2006
Lee et al.
Table 4. Crystallographic Data for 3a, 4a, and 5
CS2/CH2Cl2 (3:1), and for 5 with hexane into CS2. Diffraction data
of 3a (273 K), 4a (273 K), and 5 (130 K) were collected on a
Bruker SMART diffractometer/CCD area detector. Prelimi-
nary orientation matrix and cell constants were determined from
three series of ω scans at different starting angles. The hemi-
spheres of reflection data were collected at scan intervals of 0.5°
ω with an exposure time of 20 s per frame. The data were corrected
for Lorentz and polarization effects, but no correction for crystal
decay was applied. Absorption corrections were performed using
SADABS.17
Each structure was solved by direct18 and difference Fourier
methods and was refined by full-matrix least-squares methods based
on F2 (SHELX 97).19 All non-hydrogen atoms were refined with
anisotropic thermal coefficients. Details of relevant crystallographic
data for 3a, 4a, and 5 are summarized in Table 4.
3a
4a
5
formula
fw
system
space group
a, Å
C83H14N2O7Os3 C90H21N3O6Os3 C97H28N4O5Os3
1721.56
triclinic
P1h
1810.71
monoclinic
P21/n
12.794(3)
32.934(7)
13.326(3)
90
93.81(3)
90
5603(2)
4
1899.84
triclinic
P1h
10.007
9.9255(7)
14.3279(9)
22.9116(15)
73.164(2)
83.004(2)
75.240(2)
3011.7(3)
2
b, Å
c, Å
13.1496(2)
21.9466(3)
84.321(1)
89.819(1)
71.355(1)
2721.62(6)
2
R, deg
â, deg
γ, deg
V, Å3
Z
D
calcd, Mg m-3 2.101
2.147
2.095
temp, K
λ(Mo KR), Å
µ, mm-1
θ min,max
273(2)
0.71073
7.057
1.64, 26.48
0.0710
0.2083
1.037
273(2)
0.71073
6.861
1.65, 23.00
0.0587
0.1157
1.025
130(2)
0.71073
6.387
0.93, 26.37
0.0624
0.1524
Acknowledgment. This work was supported by the Korea
Research Foundation Grant funded by the Korean Government
(MOEHRD) (KRF-2005-201-C00021) and by the Nano R&D
program (Grant No. 2005-02618) of the Korea Science and
Engineering Foundation (KOSEF) funded by Korean Ministry
of Science & Technology (MOST). This work was also
supported in part by the SRC program (Grant No. R11-2005-
008-03001-0) of the KOSEF through the Center for Intelligent
Nano-Bio Materials at Ewha Womans University.
a
Rf
b
Rw
GOF
1.028
2
a Rf ) ∑||Fo| - |Fc||/∑|Fo|. b Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2
.
Electrochemical Measurements. Cyclic voltammetry was car-
ried out on a AUTOLAB (PGSTAT 10, Eco Chemie, Netherlands)
electrochemical analyzer using the conventional three-electrode
system of a platinum working electrode (1.6 mm diameter disk,
Bioanalytical Systems, Inc.), a platinum counter wire electrode (5
cm length, 0.5 mm diameter wire), and a Ag/Ag+ reference
electrode (0.1 M AgNO3/Ag in acetonitrile with a Vycor salt
bridge). All the measurements were performed at ambient temper-
ature under nitrogen atmosphere in a dry, deoxygenated 0.1 M
chlorobenzene solution of [(n-Bu)4N]ClO4. The concentrations of
compounds were ca. 3 × 10-4 M. All potentials were referenced
to the standard ferrocene/ferrocenium (Fc/Fc+) scale. The relative
number of electrons involved in each reduction process was
obtained from the graph of current versus (time)-1/2 according to
the Cottrell equation.16
Supporting Information Available: IR spectra of 3-5, VT
13C NMR spectra of 3, and details of the crystallographic studies
of 3a, 4a, and 5 (PDF) as well as X-ray crystallographic files for
3a, 4a, and 5 (CIF). This material is available free of charge via
the Internet at http://pubs.acs.org.
OM060566H
(16) Bard, A. J.; Faulkner, L. R. Electrochemical Methods; John Wiley
& Sons: New York, 1980; pp 142-146.
(17) Sheldrick, G. M. SADABS, A program for area detector absorption
corrections; University of Go¨ttingen: Germany, 1994.
(18) Sheldrick, G. M. Acta Crystallogr. A 1990, 46, 467-473.
(19) Sheldrick, G. M. SHELX97, Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Germany, 1997.
X-ray Crystallographic Studies. Crystals of 3a, 4a, and 5
suitable for X-ray analysis were grown by slow solvent diffu-
sion; for 3a with hexane into CS2, for 4a with methanol into