Synthesis and characterization of μ3-η2,η2,η2- C60 trirhenium hydrido cluster complexes

Article abstract of DOI:10.1021/om0101341

The reaction of C₆₀ with Re₃(μ-H)₃(CO)₁₁(NCMe) in refluxing chlorobenzene produces Re₃(μ-H)₃(CO)₉(μ₃- η²,η²,η²-C₆₀) (1) in 50% yield. Initial decarbonylation of 1 with Me₃NO/MeCN followed by reaction with PPh₃ in boiling chlorobenzene affords Re₃(μ-H)₃(CO)₈(PPh₃)- (μ₃-η²,η²,η²- C₆₀) (2) in a low yield (26%). Treatment of 1 with PhCH₂N=PPh₃ at room temperature gives a benzyl isocyanide substituted product Re₃(μ-H)₃(CO)₈(CNCH₂Ph) (μ₃ η²,η²,η²-C₆₀) (3) in 53% yield. Compounds 1, 2, and 3 have been isolated as crystalline solids and characterized by spectroscopic (infrared, mass, ¹H, ³¹P, and ¹³C NMR) and analytical data. The structure of 3 has been determined by a single-crystal X-ray diffraction study. The C₆₀ ligand is coordinated to the trirhenium triangle in a μ₃-η²,η²,η² bonding mode, and the benzyl isocyanide ligand occupies an axial position of a rhenium atom. Electrochemical properties of 1 and 2 have been studied by cyclic voltammetry (CV) in chlorobenzene (CB) solutions. The general features of CV curves have revealed four reversible redox couples for 1 and 2 in the CB potential window. The CV results suggest that a C₆₀-mediated electron transfer to the trirhenium center takes place in 1^2- species for 1 and 2^3- for 2.

Full text of DOI:10.1021/om0101341

Organometallics 2001, 20, 3139-3144
3139
Syn th esis a n d Ch a r a cter iza tion of µ3-η2,η2,η2-C60
Tr ir h en iu m Hyd r id o Clu ster Com p lexes
Hyunjoon Song,† Yumi Lee,† Zel-Ho Choi,† Kwangyeol Lee,† J oon T. Park,*,†
J uhyoun Kwak,† and Moon-Gun Choi‡
Department of Chemistry and School of Molecular Science (BK21), Korea Advanced Institute of
Science and Technology, Taejon 305-701, Korea, and Department of Chemistry,
Yonsei University, Seoul, 120-749, Korea
Received February 20, 2001
The reaction of C60 with Re3(µ-H)3(CO)11(NCMe) in refluxing chlorobenzene produces
Re3(µ-H)3(CO)9(µ3-η2,η2,η2-C60) (1) in 50% yield. Initial decarbonylation of 1 with Me3NO/
MeCN followed by reaction with PPh3 in boiling chlorobenzene affords Re3(µ-H)3(CO)8(PPh3)-
(µ3-η2,η2,η2-C60) (2) in a low yield (26%). Treatment of 1 with PhCH2NdPPh3 at room
temperature gives a benzyl isocyanide substituted product Re3(µ-H)3(CO)8(CNCH2Ph)(µ3-
η2,η2,η2-C60) (3) in 53% yield. Compounds 1, 2, and 3 have been isolated as crystalline solids
1
and characterized by spectroscopic (infrared, mass, H, 31P, and 13C NMR) and analytical
data. The structure of 3 has been determined by a single-crystal X-ray diffraction study.
The C60 ligand is coordinated to the trirhenium triangle in a µ3-η2,η2,η2 bonding mode, and
the benzyl isocyanide ligand occupies an axial position of a rhenium atom. Electrochemical
properties of 1 and 2 have been studied by cyclic voltammetry (CV) in chlorobenzene (CB)
solutions. The general features of CV curves have revealed four reversible redox couples for
1 and 2 in the CB potential window. The CV results suggest that a C60-mediated electron
transfer to the trirhenium center takes place in 12- species for 1 and 23- for 2.
In tr od u ction
cyclohexatriene-like bonding mode, µ3-η2,η2,η2-C60, is a
dominant one in these cluster complexes. In our previ-
ous work, some of triosmium-C60 complexes have re-
vealed an unusual electronic communication between
metal cluster and C60 centers,4b,8 which may be useful
for the development of specific electronic application in
materials science. We have recently demonstrated that
the existing C60 bonding modes on the cluster frame-
work can be converted to new ones by modifying the
coordination sphere of metal centers to which C60 is
coordinated. The first example of reversible intercon-
version between µ-η2,η2-C60 and µ3-η2,η2,η2-C60 has been
observed on an Os5C cluster framework by addition or
elimination of 2e-donor ligands such as carbon monoxide
and benzyl isocyanide.5 Our further efforts have resulted
in transformation of µ3-η2,η2,η2-C60 to a new σ-type
µ3-η1,η2,η1-C60 ligand on a triosmium cluster framework
upon insertion of a benzyl isocyanide ligand into an
Os-Os bond.9 As an extension of our work on these
metal cluster-C60 complexes, we employed as a metal
cluster moiety the trirhenium hydridocarbonyl group,
Re3(µ-H)3(CO)9, which is isoelectronic with Os3(CO)9.
Herein we report the synthesis and characterization of
a C60-trirhenium hydridocarbonyl complex, Re3(µ-H)3-
(CO)9(µ3-η2,η2,η2-C60) (1), and its substitution prod-
ucts, Re3(µ-H)3(CO)8L(µ3-η2,η2,η2-C60) (L ) PPh3 (2);
PhCH2NC (3)).
The interaction between metal clusters and a carbon
cluster C60 is one of the most interesting topics in the
area of exohedral metallofullerene chemistry.1 In par-
ticular, the metal cluster-C60 complexes among met-
allofullerenes can be viewed as molecular analogues of
metal and carbon hybrid materials, namely, carbon
nanotubes on one hand and metal nanoparticles on the
other, which receive much current attention due to their
potential for future technological applications.2 Since
our initial report on metal cluster-C60 complexes,3
subsequent development in π-complex chemistry has
resulted in η2-C60, µ-η2,η2-C60, and µ3-η2,η2,η2-C60 com-
plexes mainly in group 8 metals such as Os3,4 Os5C,5
Ru3,6 Ru5C, Ru6C, and PtRu5C,7 and the face-capping
* To whom correspondence should be addressed. E-mail: jtpark@
mail.kaist.ac.kr. Fax: +82-42-869-2810.
† Korea Advanced Institute of Science and Technology.
‡ Yonsei University.
(1) (a) Balch, A. L.; Olmstead, M. M. Chem. Rev. 1998, 98, 2123.
(b) Stephens, A. H. H.; Green, M. L. H. Adv. Inorg. Chem. 1997,
44, 1.
(2) (a) Yakobson, B. I.; Smalley, R. E. Am. Sci. 1997, 85, 324. (b)
Dresselhaus, M. S.; Dresselhaus, G.; Eklund, P. C. Science of Fullerenes
and Carbon Nanotubes; Academic Press: San Diego, 1996. (c) Schmid,
G. Clusters and Colloids. From Theory to Applications; VCH: Wein-
heim, 1994.
(3) Park, J . T.; Cho, J .-J .; Song, H. Chem. Commun. 1995, 15.
(4) (a) Park, J . T.; Song, H.; Cho, J .-J .; Chung, M.-K.; Lee, J .-H.;
Suh, I.-H. Organometallics 1998, 17, 227. (b) Song, H.; Lee, K.; Park,
J . T.; Choi, M.-G. Organometallics 1998, 17, 4477. (c) Song, H.; Lee,
K.; Park, J . T.; Chang, H. Y.; Choi, M.-G. J . Organomet. Chem. 2000,
599, 49.
(7) (a) Lee, K.; Hsu, H.-F.; Shapley, J . R. Organometallics 1997, 16,
3876. (b) Lee, K.; Shapley, J . R. Organometallics 1998, 17, 3020.
(8) Park, J . T.; Cho, J .-J .; Song, H.; J un, C.-S.; Son, Y.; Kwak, J .
Inorg. Chem. 1997, 36, 2698.
(5) Lee, K.; Lee, C. H.; Song, H.; Park, J . T.; Chang, H. Y.; Choi,
M.-G. Angew. Chem., Int. Ed. 2000, 39, 1801.
(6) (a) Hsu, H.-F.; Shapley, J . R. J . Am. Chem. Soc. 1996, 118, 9192.
(b) Hsu, H.-F.; Shapley, J . R. J . Organomet. Chem. 2000, 599, 97.
(9) Song, H.; Lee, K.; Lee, C. H.; Park, J . T.; Chang, H. Y.; Choi,
M.-G. Angew. Chem., Int. Ed. 2001, 40, 1500.
10.1021/om0101341 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 06/07/2001

3140 Organometallics, Vol. 20, No. 14, 2001
Song et al.
NC ligands occupy an axial position, respectively. The
1H NMR spectra of 2 and 3 show two hydridic reso-
nances (2; δ -14.5 (J PH ) 15.2 Hz) and -15.6, 3; δ -14.8
and -15.3) with an intensity ratio of 2:1, respectively.
The 31P{1H} NMR spectrum of 2 shows a singlet at δ
8.9. Complex 3 is much more soluble in CS2 than 2, and
thus 13C NMR spectrum has been obtained for 3. The
13C{1H} NMR spectrum (CO region, 298 K) of 3 exhibits
four resonances at δ 189.5, 186.8, 184.3, and 183.6 in a
ratio of 2:2:2:2 for the eight carbonyls. The four signals
can be assigned to a pair of axial carbonyls and three
inequivalent pairs of equatorial carbonyls, which implies
no carbonyl fluxionality in 3 in contrast to 1. The Cs
symmetric nature of 3 reveals three sp3 carbon reso-
nances (δ 82.1, 77.2, and 67.3) and 29 sp2 carbon
resonances comprised of 25 and 4 (δ 150.2, 144.0, 143.7,
and 142.7 denoted as •) lines in an intensity ratio of 2:1
(see the bottom spectrum of Figure 1). The IR spectra
(CO region) of 2 and 3 are similar to each other, but
are different from that of Os3(CO)8(PPh3)(µ3-η2,η2,η2-
C60), in which the phosphine ligand occupies an equato-
rial site.4b
The axial preference of PPh3 and PhCH2NC ligands
in 2 and 3 could be explained by both steric and
electronic reasons. Equatorial sites at each rhenium
center are sterically very conjested with six coordina-
tion, and intramolecular axial interaction is diminished
by the lengthening of the Re-Re bonds due to the
bridging hydrides (vide infra).11 Donor ligands such as
PPh3 and PhCH2NC coordinated trans to a hydride
ligand (equatorial site) are electronically disfavored with
respect to those trans to an electron-withdrawing C60
ligand (axial site).12
Cr ysta l Str u ctu r e of 3‚CS2. The overall molecular
geometry and the atomic labeling scheme of 3 are
illustrated in Figure 2. Interatomic distances and angles
are listed in Tables 1 and 2, respectively. Compound 3
has a triangle of rhenium atoms, with the three edges
bridged by hydride ligands. All the rhenium atoms bear
four terminally bonded (CO, PhCH2NC, and C60) 2e-
donor ligands, so that the coordination around each
rhenium atom is nearly octahedral. It has an idealized
Cs symmetry, with a mirror plane containing the Re(1)
atom and bisecting the Re(2)-Re(2)′ bond. A benzyl
isocyanide ligand is coordinated to the Re(1) atom in
an axial position and lies in the mirror plane. The axial
isocyanide ligand and two axial carbonyls are parallel
with respect to the normal vector of the Re3 plane.
However, in other structurally characterized Ru3 and
Os3 complexes, such as Ru3(CO)9(µ3-η2,η2,η2-C60),6a Os3-
(CO)8(PPh3)(µ3-η2,η2,η2-C60),4b Os3(CO)7(PMe3)2(µ3-η2,η2,η2-
C60),4c and Os3(CO)6(PMe3)3(µ3-η2,η2,η2-C60),4c carbonyl
and phosphine ligands on each metal center are slightly
twisted all in the same direction and the three axial
carbonyls are disposed in a propeller-like configuration.
This structural difference is likely to be ascribed to the
elongated Re-H-Re bonds (av 3.189(1) Å) due to the
hydride ligands,11 which compares with Ru-Ru (av
2.88(1) Å for Ru3(CO)9(µ3-η2,η2,η2-C60),6a and Os-Os (av
2.917 (1) Å for Os3(CO)8(PPh3)(µ3-η2,η2,η2-C60)4b) bond
lengths. The angle between equatorial carbonyls (av
Resu lts a n d Discu ssion
Syn th esis a n d Ch a r a cter iza tion of 1-3. A chlo-
robenzene solution of C60 and excess (2 equiv) Re3(µ-
H)3(CO)11(NCMe) was heated at reflux for 3 h. Evapo-
ration of the solvent and purification by TLC (silica gel,
CS2) afforded Re3(µ-H)3(CO)9(µ3-η2,η2,η2-C60) (1) as a red
brown solid (Rf ) 0.9, 50%). Initial decarbonylation of
1 with Me3NO/MeCN and subsequent reaction with
PPh3 in boiling chlorobenzene gave Re3(µ-H)3(CO)8-
(PPh3)(µ3-η2,η2,η2-C60) (2) as a brown solid (26%), whereas
treatment of 1 with PhCH2NdPPh3 at room tempera-
ture produced a benzyl isocyanide substituted product,
Re3(µ-H)3(CO)8(PhCH2NC)(µ3-η2,η2,η2-C60) (3), as a red
brown solid (53%). Triphenylphosphinalkylimine re-
agents are known to react with metal carbonyl com-
plexes to yield metal isocyanide substituted com-
pounds.10 Compounds 1 and 3 are soluble in CS2 and
chlorinated benzenes, but 2 is sparingly soluble in these
solvents.
Formulation of the µ3-η2,η2,η2-C60 trirhenium hydrido
complexes, 1-3, is supported by both elemental analysis
and the molecular ion (M+) multiplet in the FAB
positive ion mass spectrum (MS) of each compound. The
M+ multiplet in the MS of 1-3 matches perfectly the
calculated pattern [the highest peak in the M+ multiplet
(m/z, found, calcd); 1 (1534, 1534), 2 (1769, 1769), and
3 (1624, 1624)].
The NMR data indicates an idealized C3v symmetry
for 1 in solution similar to the previously reported
Os3(CO)9(µ3-η2,η2,η2-C60).4 The 13C{1H} NMR spectrum
(CO region, 298 K) shows a single resonance at δ 183.2
for the nine carbonyls, which implies the presence of a
fast localized 3-fold rotation of three carbonyl groups
on each rhenium atom at room temperature. The 13C
NMR spectrum of the C60 region (see the top spectrum
of Figure 1) reveals 12 resonances at δ 152.7, 150.0,
147.6, 146.5, 145.4, 144.7, 144.6, 143.6, 143.3, 142.6,
141.3, and 76.8. The four sp2 carbon resonances (three
carbon atoms each) at δ 150.0, 143.6, 143.3, and 142.6
labeled as “•” appear with about half of the intensity of
the other seven sp2 carbon resonances (six carbon atoms
each). The unique high-field signal at δ 76.8 is assigned
to an sp3 carbon resonance (six carbon atoms) directly
bonded to the rhenium atoms. This high-field chemical
shift is comparable to those of Os3(CO)9(µ3-η2,η2,η2-C60)
(δ 61.2)4b and Ru3(CO)9(µ3-η2,η2,η2-C60) (δ 73.3).6b The
general features of the IR spectrum of 1 are quite
similar to those of Os3(CO)9(µ3-η2,η2,η2-C60).4b
Both spectroscopic data and structural characteriza-
tion (vide infra) indicate that compounds 2 and 3 have
a Cs symmetric nature, in which the PPh3 and PhCH2-
(11) Churchill, M. R.; DeBoer, B. G.; Rotella, F. J . Inorg. Chem. 1976,
15, 1843.
(10) Lin, Y.-W.; Gau, H.-M.; Wen, Y.-S.; Lu, K.-L. Organometallics
1992, 11, 1445.
(12) Beringhelli, T.; D’Alfonso, G.; Freni, M.; Ciani, G.; Moret, M.;
Sironi, A. J . Chem. Soc., Dalton Trans. 1989, 1143.

µ3-η2,η2,η2-C60 Trirhenium Hydrido Complexes
Organometallics, Vol. 20, No. 14, 2001 3141
F igu r e 1. 13C NMR spectrum (C60 region, 100 MHz) of 1 (a) and 3 (b).
Ta ble 1. Selected In ter a tom ic Dista n ces (Å) a n d
Esd ’s for 3‚CS2
(A) Metal-Metal Distances
Re(1)-Re(2)
3.1858(8)
Re(2)-Re(2)′
3.194(1)
(B) Metal-Carbon (Carbonyl and Isocyanide) Distances
Re(1)-C(101)
Re(2)-C(202)
Re(1)-C(400)
1.94(2)
1.91(2)
2.00(2)
Re(2)-C(201)
Re(2)-C(203)
1.95(2)
1.94(2)
(C) Carbon-Nitrogen and Carbon-Oxygen Distances
C(101)-O(101)
C(202)-O(202)
C(400)-N(1)
1.13(2)
1.18(2)
1.16(3)
C(201)-O(201)
C(203)-O(203)
1.13(2)
1.14(2)
(D) Metal-Hydride Distances
Re(1)-H(2)
Re(2)-H(2)
1.7(1)
1.9(1)
Re(2)-H(1)
1.71(7)
2.33(1)
(E) Metal-Carbon (C60) Distances
Re(1)-C(1)
Re(2)-C(3)
2.27(1)
2.32(1)
Re(2)-C(2)
(F) Distances within the C60 Ligand
C(1)-C(1)′
C(2)-C(3)
1.49(3)
1.44(2)
C(1)-C(2)
C(3)-C(3)′
1.48(2)
1.49(2)
(G) Distances within the Isocyanide Ligand
C(400)-N(1)
C(401)-C(402)
1.16(3)
1.54(4)
N(1)-C(401)
1.51(3)
ring) of the C60 ligand positions centrally over the Re3
framework (Re(1)-C(1) ) 2.27(1) Å, Re(2)-C(2) )
2.33(1) Å, and Re(2)-C(3) ) 2.34(1) Å). The C60 ring is
essentially parallel with the Re3 plane with a dihedral
angle of 1.3° [cf. 0.9° for Ru3(CO)9(µ3-η2,η2,η2-C60),6a 1.2°
for Os3(CO)8(PPh3)(µ3-η2,η2,η2-C60),4b and 1.3° for Os3-
(CO)7(PMe3)2(µ3-η2,η2,η2-C60)4c]. The C6 ring is pulled
away from the C60 surface, consistent with the change
in the hybridization to sp3. The average angle between
the metal-coordinated C-C bond vector at the 6,6 ring
junction and the plane defined by one of the two carbon
atoms and its two neighboring sp2 and sp3 carbon atoms
is 35(1)°, which is larger than the free C60 value of 31°.14
F igu r e 2. Molecular geometry and atomic labeling scheme
for 3. Solvate molecule and disordered atoms are omitted
for clarity.
C-Re-C ) 88.7(8)°) is smaller than those for Os3-
(CO)8(PPh3)(µ3-η2,η2,η2-C60) (av 95.6°), indicating that
equatorial sites in compound 3 are more conjested than
those of group 8 metal complexes because of the steric
effect of the hydride ligands. The average Re-H bond
distance (1.8(1) Å) is comparable with that for Re3-
(µ-H)3(CO)11(PPh3) (1.822(8) Å).13
All other features of the molecular geometry are
within the expected range. The average C-C bond
The C60 ligand is coordinated to the Re3 triangle in a
µ3-η2,η2,η2-C60 fashion. A six-membered carbon ring (C6
(13) Wei, C.-Y.; Garlaschelli, L.; Bau, R.; Koetzle, T. F. J . Organomet.
Chem. 1981, 213, 63.
(14) Fagan, P. J .; Calabrese, J . C.; Malone, B. Acc. Chem. Res. 1992,
25, 134.

3142 Organometallics, Vol. 20, No. 14, 2001
Song et al.
Ta ble 2. Selected In ter a tom ic An gles (d eg) a n d
Esd ’s for 3‚CS2
(A) Intermetallic Angles
Re(2)-Re(1)-Re(2)′ 60.17(2) Re(1)-Re(2)-Re(2)′ 59.92(1)
(B) M-M-CO and M-M-CN Angles
Re(2)-Re(1)-C(101) 103.9(5) Re(2)′-Re(1)-C(1A) 163.1(5)
Re(1)-Re(2)-C(201) 94.9(4)
Re(1)-Re(2)-C(202) 106.3(5)
Re(1)-Re(2)-C(203) 164.2(4) Re(2)′-Re(2)-C(201) 95.2(4)
Re(2)′-Re(2)-C(202) 165.0(5) Re(2)′-Re(2)-C(203) 105.5(4)
Re(2)-Re(1)-C(400) 97.4(5)
(C) Re-C-O, Re-C-C, and C-Re-C Angles
Re(1)-C(101)-O(101) 179(1) Re(2)-C(201)-O(201) 178(1)
Re(2)-C(202)-O(202) 178(1) Re(2)-C(203)-O(203) 178(1)
Re(1)-C(400)-N(1)
179(2) C(101)-Re(1)-C(400) 89.9(6)
C(101)-Re(1)-C(101)′ 91.2(9) C(201)-Re(2)-C(202) 91.7(6)
C(202)-Re(2)-C(203) 87.5(7) C(201)-Re(2)-C(203) 92.3(6)
(D) Angles Involving Metal-Coordinated Carbon in C60
C(1)′-C(1)-C(2)
C(2)-C(3)-C(3)′
119.4(7)
120.0(6)
C(1)-C(2)-C(3)
121(1)
length at the junction of the 5,6 ring is 1.45(2) Å, and
that at the junction of the 6,6 ring is 1.39(2) Å. The
Os-CO distances range from 1.91(2) to 1.95(2) Å, C-O
bond lengths range from 1.13(2) to 1.18(2) Å, and
Os-C-O angles are in the range 178(1)-179(1)°. The
CS2 solvate molecules do not enter into any significant
interactions with molecule 3.
Electr och em ica l Stu d ies of 1 a n d 2. Electrochemi-
cal properties of 1 and 2 have been examined by cyclic
voltammetry in chlorobenzene (CB) solutions with tet-
rabutylammonium perchlorate as the supporting elec-
trolyte. Cyclic voltammograms (CV) of 1 and 2 are
shown in Figure 3. Half-wave potentials (E1/2) of free
C60, 1, 2, and known triosmium µ3-η2,η2,η2-C60 complexes
are summarized in Table 3. The general features of CV
curves recorded for 1 and 2 reveal four reversible redox
couples for 1 and three redox couples for 2 within the
solvent cutoff. The third redox wave of 2 corresponds
to a two-electron process, while it could be resolved into
two one-electron redox couples at half-wave potentials
of -1.75 and -1.77 V by simulation as indicated in
Table 3.
The first and second reduction waves of 1 are shifted
to more positive potential by ca. 110 and 190 mV,
respectively, in comparison with those of free C60. These
positive potential shifts by the metal cluster addend on
C60 have been previously observed in triosmium µ3-
η2,η2,η2-C60 complexes as shown in Table 3. The third
reduction potential (-1.34 V) of 1 is very close to the
second reduction potential (-1.24 V) and even more
positive than the second reduction of C60 (-1.43 V). This
unusually large anodic shift implies that two electrons
accepted through the C60 ligand in 12- are significantly
delocalized to the trirhenium center. Dianionic species
12- with electron delocalization to the metal center,
F igu r e 3. Cyclic voltammograms of 1 and 2 in dry
deoxygenated chlorobenzene (0.1 M [(n-Bu)4N][ClO4]). Scan
rate ) 5 mV/s.
with the negative shifts (ca. 85 mV) observed in the
phosphine-substituted triosmium µ3-η2,η2,η2-C60 com-
plexes.4b The first through third reduction potentials of
2 are comparable to those of free C60 with anodic shifts,
which indicates that three successive C60-localized
reductions occur to produce 2-, 22-, and 23-. The third
and fourth reductions of 2, however, take place at very
close potentials. This observation also supports the
conclusion that the electron density in 23- is signifi-
cantly delocalized to the trirhenium center, resulting
in a large positive shift of the fourth reduction potential
of 2.
The general electrochemical properties of 1 and 2 are
analogous to those of Os3(CO)9(µ3-η2,η2,η2-C60) (4) and
Os3(CO)8(PMe3)(µ3-η2,η2,η2-C60) (5), respectively.4b The
electron delocalization takes place in 12- species for 1
and 23- for 2. The donor effect of the substituted
phosphine ligand results in more negative reduction
potentials and significantly affects the electrochemical
pathways in these C60-metal cluster complexes. The
C60-mediated electronic communication between C60 and
metal cluster centers has been clearly observed in these
C60-trirhenium cluster complexes as well and seems to
be a unique general property of C60-metal cluster
complexes compared to monometallic C60 complexes
(e.g., [(Et3P)2M]n(η2-C60) (M ) Ni, Pd, Pt; n ) 1-4),15a
(η5-C9H7)Ir(CO)(η2-C60),15b and Co(NO)(PPh3)2(η2-C60)15c),
which showed only C60-localized sequential reductions.
Trirhenium centers display a more facile electronic
communication with C60 than triosmium centers in
electronic communication between C60 and metal cluster
moieties based on the observed reduction potentials
(E1/2-2/-3 ) -1.34 (1) vs -1.61 (4) and E1/2-3/-4 ) -1.77
(2) vs -1.95 (5)) in Table 3. The µ3-η2,η2,η2-C60 metal
cluster complexes have shown a remarkable electro-
therefore, undergoes much easier reduction via the C60
2-
ligand than free C60
to afford 13-. This electron
delocalization is also reflected in the fourth reduction
of 1 with an anodic shift. The direct metal center
reduction of Re3(µ-H)3(CO)12 has been observed at far
more negative potential of -2.17 V under similar
conditions.
The first and second reductions of 2 take place at
more negative potentials than those of 1 by 90 and 110
mV, respectively, revealing the electron-donating nature
of the phosphine ligand. These values are consistent
(15) (a) Lerke, S. A.; Parkinson, B. A.; Evans, D. H.; Fagan, P. J . J .
Am. Chem. Soc. 1992, 114, 7807. (b) Koefod, R. S.; Xu, C.; Lu, W.;
Shapley, J . R.; Hill, M. G.; Mann, K. R. J . Phys. Chem. 1992, 96, 2928.
(c) Chernega, A. N.; Green, M. L. H.; Haggitt, J .; Stephens, H. H. J .
Chem. Soc., Dalton Trans. 1998, 755.

µ3-η2,η2,η2-C60 Trirhenium Hydrido Complexes
Organometallics, Vol. 20, No. 14, 2001 3143
Ta ble 3. Ha lf-Wa ve P oten tia ls (E1/2 vs E°F c/F c ) of C60, 1, 2, a n d Tr iosm iu m µ3-η2,η2,η2-C60 Com p lexes
+
0/-1
-1/-2
-2/-3
-3/-4
compound
E1/2
E1/2
E1/2
E1/2
solvent
ref
C60
1
2
-1.06
-0.95
-1.04
-1.08
-0.98
-1.06
-1.43
-1.91
-2.38
CB
CB
CB
DCB
DCB
DCB
this work
this work
this work
4b
4b
4b
-1.24
-1.35
-1.46
-1.33
-1.42
-1.34
-1.75
-1.90
-1.61
-1.93
-1.73
-1.77
-2.38
-1.74
-1.95
C60
Os3(CO)9(µ3-η2,η2,η2-C60) (4)
Os3(CO)8(PMe3)(µ3-η2,η2,η2-C60) (5)
Ta ble 4. Cr ysta l a n d Str u ctu r e Deter m in a tion
chemical stability, which will be promising in the future
technological applications as electronic materials.
Da ta for 3‚CS2
formula
fw
C76H10NO8Re3•CS2
1623.54
Exp er im en ta l Section
system
space group
a, Å
orthorhombic
Pnma
19.405(2)
13.163(1)
20.044(2)
5119.8(7)
4
2.205
233(2)
0.71073
7.230
1.85° e θ e 23.28°
-21 e h e 21, -14 e k e 14,
-22 e l e 22
31 107
3882
Gen er a l Com m en ts. All reactions were carried out under
a nitrogen atmosphere with use of standard Schlenk tech-
niques. Solvents were dried appropriately before use. C60
(99.5%, Southern Chemical Group) and triphenylphosphine
(99%, Aldrich) were used without further purification. Anhy-
drous trimethylamine N-oxide (mp 225-230 °C) was obtained
from Me3NO‚2H2O (98%, Aldrich) by sublimation (3 times) at
90-100 °C under vacuum. Re3(µ-H)3(CO)11(NCMe)16 and
b, Å
c, Å
V, Å3
Z
D
calcd, Mg m-3
temp, K
λ(Mo KR), Å
17
PhCH2NdPPh3 were prepared according to the literature
µ, mm-1
methods. Preparative thin-layer chromatography (TLC) plates
were prepared with silica gel GF254 (type 60, E. Merck).
Infrared spectra were obtained on a Bruker EQUINOX-55
θ range for collection
index ranges
1
FT-IR spectrophotometer. H (400 MHz), 13C (100 MHz), and
no. of rflns measd
no. of unique rflns
no. of rflns (I > 2σ(I))
31P (162 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
Center, 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.
3299
a
Rf
0.0526
0.1524
1.033
b
Rw
GOF
Rf ) ∑||Fo| - |Fc||/∑|Fo|. Rw ) [∑w(|Fo| - |Fc|)2/∑w|Fo| ]1/2
.
a
b
2
P r ep a r a tion of Re3(µ-H)3(CO)9(µ3-η2,η2,η2-C60) (1). A
chlorobenzene solution (60 mL) of Re3(µ-H)3(CO)11(NCMe) (2
equiv, 151.7 mg, 0.167 mmol) and C60 (1 equiv, 60.0 mg, 0.0833
mmol) was heated at reflux for 3 h. Evaporation of the solvent
and purification by preparative TLC (CS2) produced compound
1 (63.3 mg, 0.0413 mmol, 50%, Rf ) 0.9) as a red-brown solid:
IR (CS2) ν(CO) 2074 (s), 2048 (s), 2008 (m), 1987 (m), 1927
(m) cm-1; 1H NMR (400 MHz, CS2/ext. CD2Cl2, 298 K) δ -15.1
(s); 13C{1H} NMR (100 MHz, CS2/ext. CD2Cl2, 298 K) δ 183.2
(s, 9CO), 152.7 (6C), 150.0 (3C), 147.6 (6C), 146.5 (6C), 145.4
(6C), 144.7 (6C), 144.6 (6C), 143.6 (3C), 143.3 (3C), 142.6 (3C),
141.3 (6C), 76.8 (6C, C60 sp3 carbon); MS (FAB+) m/z 1536 (M+).
Anal. Calcd for C69H3O9Re3: C, 54.0; H, 0.20. Found: C, 54.1;
H, 0.48.
mmol, 53%, Rf ) 0.5) as a red brown solid: IR (cyclohexane)
ν(NC) 2178 (m); ν(CO) 2060 (vs), 2043 (s), 2011 (s), 1986 (m),
1971 (s), 1954 (m) cm-1; H NMR (400 MHz, CDCl3, 298 K) δ
1
7.6-7.3 (m, 5H), 5.3 (s, 2H), -14.8 (s, 2H), -15.3 (s, 1H); 13C-
{1H} NMR (100 MHz, CS2/ext. CD2Cl2, 298 K) δ 189.5 (2CO),
186.8 (2CO), 184.3 (2CO), 183.6 (2CO), 156.8 (2C), 153.5 (2C),
152.4 (2C), 151.0 (2C), 150.2 (1C), 147.9 (2C), 147.9 (2C), 147.6
(2C), 146.6 (2C), 146.4 (2C), 146.4 (2C), 145.6 (2C), 145.4 (2C),
145.1 (2C), 145.1 (2C), 145.0 (2C), 144.9 (2C), 144.8 (2C), 144.8
(2C), 144.6 (2C), 144.0 (1C), 143.7 (1C), 143.5 (2C), 143.2 (2C),
142.7 (1C), 142.5 (2C), 141.5 (2C), 141.4 (2C), 140.2 (2C), 132.0
(1C, NC), 130.5 (2C, phenyl), 130.3 (2C, phenyl), 128.2 (2C,
phenyl), 82.1 (2C, C60 sp3), 77.2 (2C, C60 sp3), 67.3 (2C, C60 sp3),
49.7 (1C, PhCH2); MS (FAB+) m/z 1625 (M+). Anal. Calcd for
P r epar ation of Re3(µ-H)3(CO)8(P P h 3)(µ3-η2,η2,η2-C60) (2).
An acetonitrile solution (1 mL) of anhydrous Me3NO (1.5 mg,
0.020 mmol) was added dropwise to a chlorobenzene solution
(20 mL) of compound 1 (30 mg, 0.0196 mmol) at 0 °C. The
reaction mixture was allowed to warm to room temperature
for 30 min. After evaporation of the solvent in vacuo, the
residue was dissolved in chlorobenzene (20 mL) containing
PPh3 (15.3 mg, 0.0583 mmol). The resulting solution was
heated at reflux for 90 min. Evaporation of the solvent and
purification by TLC (CS2) gave compound 2 (9.2 mg, 0.0052
mmol, 26%, Rf ) 0.6) as a brown solid: IR (CS2) ν(CO) 2059
(vs), 2041 (s), 1995 (sh), 1989 (s), 1977 (m), 1961 (m), 1923
(m) cm-1; 1H NMR (400 MHz, CS2/ext. CD2Cl2, 298 K) δ 8.1-
7.8 (m, 15H), -14.5 (d, J PH ) 15.2 Hz, 2H), -15.6 (s, 1H); 31P-
{1H} NMR (162 MHz, CS2/ext. CD2Cl2, 298 K) δ 8.9 (s); MS
(FAB+) m/z 1770 (M+). Anal. Calcd for C86H18O8PRe3: C, 58.4;
H, 1.03. Found: C, 58.5; H, 1.06.
C
76H10NO8Re3: C, 56.2; H, 0.62; N, 0.86. Found: C, 56.0; H,
0.64; N, 0.90.
Electr och em ica l Mea su r em en ts. Cyclic voltammetry was
carried out with a BAS 100B (Bioanalytical Systems, Inc.)
electrochemical analyzer using the conventional three-elec-
trode system of a platinum working electrode (1.6 mm diam-
eter disk, Bioanalytical Systems, Inc.), a platinum counter wire
electrode (5 cm length of 0.5 mm diameter wire), and a
Ag/Ag+ reference electrode (0.1 M AgNO3/Ag in acetonitrile
with a Vycor salt bridge). All measurements were performed
at ambient temperature 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.
X-r a y Str u ctu r e Deter m in a tion for 3‚CS2. Crystals of 3
suitable for an X-ray diffraction study were grown by slow
diffusion of hexane into a carbon disulfide solution of 3 at room
temperature. A brownish black crystal of 3 (0.62 × 0.14 × 0.12
mm) was mounted on a Simens SMART diffractometer/CCD
area detector. Preliminary orientation matrix and cell con-
stants were determined from three series of ω scans at
different starting angles. Each series consisted of 15 frames
collected at intervals of 0.3° ω scan with the exposure time of
P r ep a r a tion of Re3(µ-H)3(CO)8(P h CH2NC)(µ3-η2,η2,η2-
60) (3). A chlorobenzene solution (20 mL) of 1 (30.0 mg, 0.0196
C
mmol) and Ph3PdNCH2Ph (14.4 mg, 0.0392 mmol) was stirred
at room temperature for 3.5 h. Evaporation of the solvent and
separation by TLC (CS2) afforded compound 3 (16.7 mg, 0.0103
(16) Bruce, M. I.; Low, P. J . J . Organomet. Chem. 1996, 519, 221.
(17) Lee, K.-W.; Singer, L. A. J . Org. Chem. 1974, 39, 3780.

3144 Organometallics, Vol. 20, No. 14, 2001
Song et al.
10 s per frame. A total of 31 107 reflections collected at 233 K
were corrected for Lorentz and polarization effects, but no
correction for crystal decay was applied. Details of relevent
crystallographic data are summarized in Table 4.
R1 ) 5.26%, wR2 ) 15.24% ((∆/σ)max ) 0.000, ∆Fmax/∆Fmin
2.575/-3.771 e Å-3 in final ∆F map), and GOF ) 1.033.
)
Ack n ow led gm en t. This work was supported by the
National Research Laboratory (NRL) Program of the
Korean Ministry of Science & Technology (MOST) and
the Korea Science Engineering Foundation (Project No.
1999-1-122-001-5).
The structure of 3 was solved by direct and different Fourier
methods and was refined by the full-matrix least-squares
methods based on F2. The crystallographic mirror plane passed
through Re(1) and the midpoint of the Re(2)-Re(2)′ bond so
that four atoms of the isocyanide ligand, four atoms of the C60
ligand, and one bridging hydride atom were located on the
mirror plane. Five carbon atoms of the benzyl isocyanide ligand
were disordered in two orientations (see Supporting Informa-
tion), with their positions and thermal parameters fixed due
to high thermal motions. Other non-hydrogen atoms were
refined with anisotropic thermal coefficients. Three bridging
hydrogen atoms were directly located from the E-map and
refined isotropically. For all computations the SHELX97
package was used, and the function minimized was ∑w(|Fo| -
Su p p or tin g In for m a tion Ava ila ble: A figure of disor-
dered geometry for complex 3 with a complete atomic labeling
scheme, and tables of atomic coordinates and equivalent
isotropic displacement parameters, anisotropic displacement
parameters, and complete bond lengths and angles. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM0101341
|Fc|)2, with w ) 1/[σ2(Fo2) + (0.1123P)2], where P ) (Fo2 + 2Fc )/
2
3.18 The number of parameters refined was 405, and the final
(18) Sheldrick, G. M. SHELX97, Program for Crystal Structure
reliability factors for 3882 unique reflections (I > 2σ(I)) were
Refinement; University of Go¨ettingen: Germany, 1997.