Synthesis, structure, and electrochemical studies of μ3-η2,η2,η2-C 60 triosmium complexes

Article abstract of DOI:10.1021/om980361b

Two μ₃-η²,η²,η²-C ₆₀ complexes, Os₃(CO)₈(PPh₃)(μ₃-η ²,η²,η²-C₆₀) (8) and Os₃(CO)₇(PMe₃)₂(μ ₃-η²,η²,η²-C ₆₀) (9), have been prepared by decarbonylation of Os₃(CO)₉(μ₃-η²,η ²,η²-C₆₀) (6) with Me₃NO/MeCN in the presence of phosphine ligands. The molecular structure of 8 has been determined by a single-crystal X-ray diffraction study. The structure of 8 is derived from that of Os₃(CO)₁₁(PPh₃) by replacing three axial carbonyl ligands with a μ₃-face-capping C₆ ring of C₆₀. The ¹³C NMR spectra (C₆₀ region) of 6 and Os₃(CO)₈(PMe₃)(μ₃-η ²,η²,η²-C₆₀) (7) show 11 sp² and 1 sp³ carbon resonances and 29 sp² and 3 sp³ carbon resonances, respectively, which are consistent with C_3v and C_s symmetric nature of the two complexes in solution. Electrochemical properties of 6, 7, and 9 have been studied by cyclic voltammetry (CV) in 1,2-dichlorobenzene (DCB) solutions. The general features of CV curves have revealed four reversible redox couples for 6 and 7 and three for 9 in the DCB potential window. The μ₃-η²,η²,η²-C ₆₀ complexes, 6, 7, and 9, show a remarkable electrochemical stability compared to the known η²-C₆₀ triosmium carbonyl complexes. The CV results suggest that a C₆₀-mediated electron transfer to the triosmium center takes place in 6 and 7, but three successive C₆₀-localized reductions occur in 9.

Full text of DOI:10.1021/om980361b

Organometallics 1998, 17, 4477-4483
4477
Syn th esis, Str u ctu r e, a n d Electr och em ica l Stu d ies of
µ3-η2,η2,η2-C60 Tr iosm iu m Com p lexes
Hyunjoon Song,† Kwangyeol Lee,† J oon T. Park,*,† and Moon-Gun Choi‡
Department of Chemistry, Korea Advanced Institute of Science and Technology,
Taejon 305-701, Korea, and Department of Chemistry, Yonsei University,
Seoul, 120-749, Korea
Received May 11, 1998
Two µ3-η2,η2,η2-C60 complexes, Os3(CO)8(PPh3)(µ3-η2,η2,η2-C60) (8) and Os3(CO)7(PMe3)2(µ3-
η2,η2,η2-C60) (9), have been prepared by decarbonylation of Os3(CO)9(µ3-η2,η2,η2-C60) (6) with
Me3NO/MeCN in the presence of phosphine ligands. The molecular structure of 8 has been
determined by a single-crystal X-ray diffraction study. The structure of 8 is derived from
that of Os3(CO)11(PPh3) by replacing three axial carbonyl ligands with a µ3-face-capping C6
ring of C60. The 13C NMR spectra (C60 region) of 6 and Os3(CO)8(PMe3)(µ3-η2,η2,η2-C60) (7)
show 11 sp2 and 1 sp3 carbon resonances and 29 sp2 and 3 sp3 carbon resonances, respectively,
which are consistent with C3v and Cs symmetric nature of the two complexes in solution.
Electrochemical properties of 6, 7, and 9 have been studied by cyclic voltammetry (CV) in
1,2-dichlorobenzene (DCB) solutions. The general features of CV curves have revealed four
reversible redox couples for 6 and 7 and three for 9 in the DCB potential window. The
µ3-η2,η2,η2-C60 complexes, 6, 7, and 9, show a remarkable electrochemical stability compared
to the known η2-C60 triosmium carbonyl complexes. The CV results suggest that a C60-
mediated electron transfer to the triosmium center takes place in 6 and 7, but three successive
C60-localized reductions occur in 9.
In tr od u ction
tion of seeing new bonding modes, physical properties,
fluxionality, or reactivities by cooperative interactions
of metal centers. As expected, we have observed a new
bonding mode of a cluster face capping µ3-η2,η2,η2-C60
ligand in 6 and 7 and interesting fluxional processes of
restricted equilibration of in-plane equatorial C60 and
carbonyl ligands via a triply bridged intermediate in the
major isomer of 2 and 5.5 Furthermore, electrochemical
studies of 1, 3, and 4 have revealed the first example of
novel C60-mediated electron transfer to the metal cen-
ter.6 However, the first structural characterization of
the arene-like µ3-η2,η2,η2-C60 ligand has appeared for the
ruthenium analogue of 6 during our investigation.7 As
an extension of our work on this new µ3-η2,η2,η2-C60
ligand, we have been studying reactivities and electro-
chemical properties of µ3-η2,η2,η2-C60 triosmium com-
plexes. Herein we report the synthesis and character-
ization of 6, Os3(CO)8(PPh3)(µ3-η2,η2,η2-C60) (8), and
Os3(CO)7(PMe3)2(µ3-η2,η2,η2-C60) (9) and electrochemical
studies of 6, 7, and 9, together with the crystal structure
of 8.
Exohedral metallofullerenes have recently attracted
much attention1 concerning the effect of metal coordina-
tion on the chemical and physical properties of C60. In
particular, understanding of the metal substituent effect
on the redox properties of C60 is crucial for the develop-
ment of specific electronic and optical applications in
materials science.2 The electrochemical properties of
the metallofullerenes have been scarcely reported, and
detailed studies were precluded due to their electro-
chemical instabilities upon reductions.3
In previous work, we have reported synthesis and
characterization of η2-C60 and µ3-η2,η2,η2-C60 triosmium
cluster complexes, Os3(CO)11-nLn(η2-C60) (n ) 0 (1); n
) 1, L ) MeCN (2) or PPh3 (3); n ) 2, L ) PPh3 (4) or
PMe3 (5)), Os3(CO)9(µ3-η2,η2,η2-C60) (6), and Os3(CO)8-
(PMe3)(µ3-η2,η2,η2-C60) (7).4,5 These metal cluster bound
C60 complexes have been investigated with the expecta-
* To whom correspondence should be addressed. E-mail: jtpark@
sorak.kaist.ac.kr. Fax: +82-42-869-2810.
† Korea Advanced Institute of Science and Technology.
‡ Yonsei University.
Resu lts a n d Discu ssion
(1) (a) Stephens, A.; Green, M. L. H. Adv. Inorg. Chem. 1997, 44, 1.
(b) Sliwa, W. Transition Met. Chem. 1996, 21, 583. (c) Bowser, J . R.
Adv. Organomet. Chem. 1994, 36, 57. (d) Fagan, P. J .; Calabrese, J .
C.; Malone, B. Acc. Chem. Res. 1992, 25, 134.
Syn th esis a n d Ch a r a cter iza tion of 6-9. We have
previously reported the synthesis and characterization
of Os3(CO)9(µ3-η2,η2,η2-C60) (6).5 Its 13C NMR spectrum
of the carbonyl region (188-298 K) showed a single
resonance at δ 176.1 for the nine carbonyls, which
implies the presence of a fast localized 3-fold rotation
(2) Prato, M. J . Mater. Chem. 1997, 7, 1097.
(3) (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.
(4) Park, J . T.; Cho, J .-J .; Song, H. J . Chem. Soc., Chem. Commun.
1995, 15.
(5) Park, J . T.; Song, H.; Cho, J .-J .; Chung, M.-K.; Lee, J .-H.; Suh,
I.-H. Organometallics 1998, 17, 227.
(6) Park, J . T.; Cho, J .-J .; Song, H.; J un, C.-S.; Son, Y.; Kwak, J .
Inorg. Chem. 1997, 36, 2698.
(7) Hsu, H.-F.; Shapley, J . R. J . Am. Chem. Soc. 1996, 118, 9192.
S0276-7333(98)00361-6 CCC: $15.00 © 1998 American Chemical Society
Publication on Web 09/09/1998

4478 Organometallics, Vol. 17, No. 20, 1998
Song et al.
peaks in the M+ multiplet (m/z, found, calcd) are (1778,
1778) for 8 and (1640, 1640) for 9. The carbonyl region
IR spectrum of 8 is similar in pattern to that reported
for 7,5 but slightly shifted to lower energies by ca. 1-6
cm-1 relative to 7, reflecting a poorer donor property of
PPh3 than PMe3. The carbonyl region IR bands of 9
appear in the lower energy region by ca. 24 cm-1
compared to those of 8. The 13C NMR spectrum (CO
region) of 13CO-enriched 8 at 298 K shows two reso-
2
nances at δ 184.8 (d, J PC ) 5.7 Hz) and 177.6 in a 1:3
ratio, whose general features are very similar to those
of 7 (δ 185.4 (d, 2J PC ) 5.9 Hz, 2CO) and 178.5 (s, 6CO))5
and the arene analogue Os3(CO)8(PPh3)(µ3-η2,η2,η2-
2
C6H6) (δ 183.96 (d, J PC ) 8.0 Hz, 2CO) and 177.39 (s,
6CO)).8 The resonances at δ 184.8 with a P-C coupling
and at δ 177.6 can be obviously assigned to the two
carbonyl ligands on the osmium atom coordinated with
PPh3 and the six carbonyl groups on the other two
osmium atoms, respectively. The 13C NMR spectrum
of 13CO-enriched 9 reveals a broad resonance at δ 187.8
and a sharp resonance at 180.0 in a ratio of 4:3, which
can be similarly assigned to the carbonyls on the
phosphine-substituted osmium atoms and those in the
unique Os(CO)3 moiety, respectively. In all of these
complexes, a fast localized 3-fold rotation of ligands
appears to occur on each osmium center. The phos-
phine-substituted osmium center, however, may un-
dergo a restricted 3-fold rotation proposed by Pomeroy
and co-workers,9 without requiring the bulky phosphine
ligand to enter an axial site. The localized 3-fold
rotation of ligands seems to be a general fluxional
process in the µ3-η2,η2,η2-C60 triosmium carbonyl com-
plexes. Complex 7 is much more soluble in dichloroben-
zene than 8, and thus the 13C NMR spectrum of the C60
region has been obtained for 7, as shown in Figure 2.
The Cs symmetric nature of 7 in solution reveals three
sp3 carbon resonances (δ 57.2, 57.1, and 56.7) and 29
resonances comprising 25 and 4 (d, e, h, i denoted as
b) lines in an intensity ratio of 2:1 (see Scheme 1).
The 13C NMR resonances of the C60 moiety for
metallofullerenes have been reported for Rh(NO)(PPh3)2-
(η2-C60) (Cs symmetry, 31 sp2 and 1 sp3 resonances),10
Fe(CO)4(η2-C60) (C2v, 16 sp2 and 1 sp3),11 Os3(CO)9-
(PMe3)2(η2-C60) (C2v, 16 sp2 and 1 sp3),5 and Re2-
(PMe3)4H8(µ-η2,η2-C60) (Cs, 30 sp2 and 2 sp3).3c The
chemical shifts of the C60 sp2 and sp3 carbon atoms are
typically in the regions of δ 175-135 and 85-50,
respectively. In these η2-C60 complexes, the sp2 carbon
atoms adjacent to the sp3 ones (referred to as the C2
atoms) generally resonate at uniquely low fields above
ca. 155 ppm, whereas those adjacent to the C2 atoms
typically appear in the high-field region below ca. 140
ppm.1a If this generality were to hold for the µ3-η2,η2,η2-
C60 moiety in 6, the lowest and the highest field
resonances at δ 153.8 and 142.7 can be assigned to the
c and d type carbons, respectively.
F igu r e 1. 13C NMR spectrum (C60 region) of 6 in 1,2-
dichlorobenzene relative to the external standard dichlo-
romethane-d2.
of three carbonyl groups on each atom. The 13C NMR
spectrum of the C60 region (Figure 1) is now obtained
and reveals 12 resonances, at δ 153.8, 151.4, 148.2,
146.7, 145.1, 145.0, 144.7, 143.9, 143.7, 143.3, 142.7, and
61.2. The four resonances at 151.4, 143.9, 143.3, and
142.7 (dotted line) appear with about half of the
intensity of the other seven resonances except the
resonance at δ 61.2. This observation indicates the
idealized C3v symmetry of 6 in solution, which contains
12 types of carbon atoms of the C60 moiety, i.e., three
carbon atoms of each d, e, h, and i type (bold lines) and
six carbon atoms of each a, b, c, f, g, k, j, and l type, as
shown in Figure 1. The six carbon atoms (a, bold lines)
coordinated to the osmium metal center appear at δ 61.2
as a singlet with a lower intensity.
A triphenylphosphine-substituted complex, Os3(CO)8-
(PPh3)(µ3-η2,η2,η2-C60) (8), has been prepared by initial
decarbonylation of 6 with 1 equiv of Me3NO/MeCN at 0
°C and subsequent thermolysis in chlorobenzene at 100
°C in the presence of triphenylphosphine in 50% yield.
Decarbonylation of 6 with 2 equiv of Me3NO/MeCN at
0 °C followed by treatment with PMe3 at room temper-
ature produces Os3(CO)7(PMe3)2(µ3-η2,η2,η2-C60) (9) in
49% yield. Attempted synthesis of Os3(CO)7(PPh3)2(µ3-
η2,η2,η2-C60) under similar conditions resulted in a lower
(ca. 20%) yield. Complexes 8 and 9 are soluble in
common solvents such as dichloromethane, toluene,
carbon disulfide, and chlorinated benzene to form brown
(8) and grayish green (9) solutions. Formulations of 8
and 9 are established by elemental analyses and by
positive ion FAB mass spectrometry. The molecular ion
(M+) isotope multiplet in the mass spectra of 8 and 9
matches perfectly the calculated pattern: the highest
Electr och em ica l Stu d ies of 6, 7, a n d 9. Electro-
chemical properties of µ3-η2,η2,η2-C60 complexes, 6, 7,
(8) Gallop, M. A.; Gomez-Sal, M. P.; Housecroft, C. E.; J ohnson, B.
F. G.; Lewis, J .; Owen, S. M.; Raithby, P. R.; Wright, A. H. J . Am.
Chem. Soc. 1992, 114, 2502.
(9) Alex, R. F.; Pomeroy, R. K. Organometallics 1987, 6, 2437.
(10) Green, M. L. H.; Stephens, A. H. H. J . Chem. Soc., Chem.
Commun. 1997, 793.
(11) Douthwaite, R. E.; Green, M. L. H.; Stephens, A. H. H.; Turner,
J . F. C. J . Chem. Soc., Chem. Commun. 1993, 1522.

µ3-η2,η2,η2-C60 Triosmium Complexes
Organometallics, Vol. 17, No. 20, 1998 4479
F igu r e 2. 13C NMR spectrum (C60 region) of 7 in 1,2-dichlorobenzene relative to the external standard dichloromethane-
d2. Resonances due to d, e, h, and i carbons are labeled as (b).
Sch em e 1
and 9, have been examined by cyclic voltammetry in 1,2-
dichlorobenzene (DCB) solutions with tetrabuthylam-
F igu r e 3. Cyclic voltammograms of 6, 7, and 9 in dry
monium perchlorate as the supporting electrolyte. Cy-
clic voltammograms (CV) of 6, 7, and 9 are shown in
Figure 3. Half-wave potentials (E1/2) of 6, 7, 9, free C60,
known η2-C60 triosmium complexes (1 and 4), and two
organofullerenes (10 and 11)12 are summarized in Table
1. The general features of CV curves recorded for 6 and
7 reveal four reversible redox couples for 6 and three
redox couples for 7. The third redox wave of 7 corre-
sponds to a two-electron process, while it could be
resolved into two one-electron redox couples at half-
wave potentials of -1.93 and -1.95 V by simulation as
indicated in Table 1. The CV of 9 shows three reversible
one-electron redox processes: the fourth wave is not seen
due to the solvent cutoff. The number of electrons
involved in each redox wave was confirmed by chrono-
amperometry (see the Experimental Section). Each
redox couple of 7 and 9 is shifted to more negative
potential (ca. 75 mV/PMe3) compared to that of 6 due
to the electron-donating nature of the phosphine ligand,
as was previously observed in η2-C60 triosmium com-
plexes.
deoxygenated 1,2-dichlorobenzene (0.1 M [(n-Bu)4N]ClO4).
Scan rate ) 50 mV/s.
130 mV for 6 and 40 mV for 7. Transition metal C60
derivatives that undergo reduction more easily than
unsubstituted C60 are not precedented.3 Such an anodic
shift of the first reduction potential, however, was
observed for organofullerenes such as C60O13 and 1112
(vide infra) and is known to correlate well with the
LUMO energy levels. The third reduction of 6 occurs
at a potential of -1.61 V, with a significant positive shift
(290 mV) relative to that of free C60 at -1.90 V. This
unusually large positive shift suggests that the two
electrons accepted through the C60 ligand in 62- are
delocalized to the triosmium center with its strong
π-acid carbonyl ligands, as was previously proposed for
42- 6 Dianionic species 62- with electron delocalization
.
to the osmium center, therefore, undergoes easier
2-
reduction via the C60 ligand than free C60 to afford
6
3-. It should be mentioned that the direct metal center
reductions (two-electron process) of Os3(CO)12, Os3-
(CO)11(PMe3), and Os3(CO)10(PMe3)2 have been observed
at far more negative potentials of -2.05, -2.22, and
-2.53 V, respectively, under similar conditions. The
fourth reduction potential (-1.74 V) of 6 is very close
The first reduction waves of 6 and 7 are shifted to
more positive potential by ca. 100 and 20 mV, respec-
tively, in comparison with that of free C60. The second
reduction wave of 6 and 7 also shows an anodic shift of
(12) Knight, B.; Martin, N.; Ohno, T.; Orti, E.; Rovita, C.; Veciana,
J .; Vidal-Gancedo, J .; Viruela, P.; Viruela, R.; Wudl, F. J . Am. Chem.
Soc. 1997, 119, 9871.
(13) Suzuki, T.; Maruyama, Y.; Akasaka, T.; Ando, W.; Kobayashi,
K.; Nagase, S. J . Am. Chem. Soc. 1994, 116, 1359.

4480 Organometallics, Vol. 17, No. 20, 1998
Song et al.
+
Ta ble 1. Ha lf-Wa ve P oten tia ls (E1/2 vs E°F c/F c ) of F r ee C60, C60-Tr iosm iu m Com p lexes, a n d
Or ga n ofu ller en es
to the third reduction potential (-1.61 V) and even more
positive than the third reduction of C60 (-1.90 V), which
implies that further electron delocalization from C60 to
the metal center occurred in 63- as well. Comparable
first through third reduction potentials of 7 to those of
free C60 indicate that three successive C60-localized
reductions occur to produce 71-, 72-, and 73-. Similarly,
three redox waves of 9 appear at more negative poten-
tials than those of free C60 by ca. 50-190 mV. The third
and fourth reductions of 7, however, take place es-
sentially at the same potential. This observation fur-
ther supports the conclusion that the electron density
in 73- is also significantly delocalized to the triosmium
center, resulting in a large positive shift of the fourth
reduction potential of 7.
the C60-mediated electron transfer to the triosmium
center. The IR spectra obtained for each anionic species
were very poorly defined, presumably because of incom-
plete reductions of each species during the spectroelec-
trochemical experiment.
Electrochemical studies of transition metal C60 com-
plexes have been reported for metallofullerenes such as
[(Et3P)2M]n(η2-C60) (M ) Ni, Pd, Pt; n ) 1-4),3a (η5-
C9H7)Ir(CO)(η2-C60),3b and Co(NO)(PPh3)2(η2-C60),3c which
revealed C60-localized sequential reductions. These C60-
localized reductions are well documented in both metal-
lofullerenes3 and organofullerenes,12,13 whose redox
potentials are slightly modified in comparison with free
C60 by the metal-to-C60 π-back-donation or the inductive
effect of the attached organic moiety. Either metal
complexation or electron-donating organic addend is
known to raise the energy of the C60-localized LUMO
and thus decreases the electron affinity of C60. Cyclic
voltammetric and IR spectroelectrochemical studies of
η2-C60 triosmium complexes 1, 3, and 4, however,
showed a C60-mediated electron transfer to the trios-
Recently Wudl and co-workers12 reported electro-
chemical studies and quantum-chemical calculation of
spiroannelated methanofullerenes, 10 and 11 (see Table
1), to understand the electronic effect of organic addends
on the molecular orbitals and redox properties of C60.
The anodic shift (81 mV) of the first reduction potential
of 10 with respect to C60 has been explained by the
inductive effect of the electronegative cyclohexadienone
addend on the stabilization of the LUMO localized on
the C60 cage. The dianionic species of 10 and 11 were
proposed to have an open structure where one of the
cyclopropane-C60 bonds is broken and each electron is
localized on both C60 and the addend (cyclohexadienone
for 10 and quinone for 11). 102- and 112- were reported
to undergo reductions through the C60 ligand at poten-
tials -1.602 and -1.670 V, which are very similar to
the reduction potentials of -1.61 V for 12-, -1.76 V for
-1/-2
-2/-3
mium metal center (see E1/2
for 1 and E1/2
for
4 in Table 1).6 This unusual electronic communication
between C60 and the metal center has also been ob-
served in µ3-η2,η2,η2-C60 triosmium complexes 6 and 7.
All the known η2-C60 transition metal complexes un-
dergo metal dissociation in the reduced anions,3,6 be-
cause the additional electrons are accommodated in a
LUMO that is derived from both the 29 double bonds
of C60 and a component of the metal-C60 antibonding
orbital.3c The µ3-η2,η2,η2-C60 triosmium complexes 6, 7,
and 9 with three metal-C60 π-bonds, however, have
shown a remarkable electrochemical stability and a
reversible behavior for redox processes with as many
as four redox couples in the DCB potential window.
Cr ysta l Str u ctu r e of 8‚1.5CS2. The overall molec-
ular geometry and the atomic labeling scheme of 8 are
illustrated in Figure 4. Interatomic distances and
angles are listed in Tables 2 and 3, respectively.
4
2-, and -1.61 V for 62-
potentials among dianionic species 12-, 42-, 62-, 102-
. Similar third reduction
,
and 112- imply that electrons in 12-, 42-, and 62- are
appreciably delocalized to the triosmium addend in
analogy with 102- and 112- with a negative charge on
the addend. IR spectroelectrochemical studies of 6 and
7 have been attempted to obtain definitive evidence for

µ3-η2,η2,η2-C60 Triosmium Complexes
Organometallics, Vol. 17, No. 20, 1998 4481
Ta ble 3. Selected In ter a tom ic An gles (d eg) a n d
Esd ’s for 8‚1.5CS2
(A) Intermetallic Angles
Os(2)-Os(1)-Os(3)
59.64(2) Os(1)-Os(2)-Os(3)
59.01(2)
(B) M-M-CO and M-M-P Angles
Os(2)-Os(1)-C(101)
Os(2)-Os(1)-C(102)
Os(2)-Os(1)-P
92.7(5)
163.2(4)
105.1(1)
80.6(5)
Os(3)-Os(1)-C(101)
Os(3)-Os(1)-C(102)
Os(3)-Os(1)-P
Os(3)-Os(2)-C(201)
Os(3)-Os(2)-C(202)
Os(3)-Os(2)-C(203)
Os(2)-Os(3)-C(301)
Os(2)-Os(3)-C(302)
Os(2)-Os(3)-C(303)
81.6(5)
105.0(4)
162.4(1)
101.0(5)
167.4(4)
83.2(7)
81.8(6)
119.9(6)
143.8(5)
Os(1)-Os(2)-C(201)
Os(1)-Os(2)-C(202)
Os(1)-Os(2)-C(203)
Os(1)-Os(3)-C(301)
Os(1)-Os(3)-C(302)
Os(1)-Os(3)-C(303)
125.4(5)
139.1(7)
96.9(5)
173.1(5)
82.8(5)
(C) Os-C-O, C-Os-C, and C-Os-P Angles
Os(1)-C(101)-O(101) 178(1) Os(1)-C(102)-O(102) 179(1)
Os(2)-C(201)-O(201) 174(2)
Os(2)-C(203)-O(203) 177(2)
Os(3)-C(302)-O(302) 179(2)
Os(2)-C(202)-O(202) 175(1)
Os(3)-C(301)-O(301) 177(2)
Os(3)-C(303)-O(303) 176(2)
C(101)-Os(1)-C(102)
C(102)-Os(1)-P
91.4(6)
C(101)-Os(1)-P
90.9(5)
91.1(4)
93.2(7)
90.0(7)
96.3(7)
C(201)-Os(2)-C(202)
C(202)-Os(2)-C(203)
C(301)-Os(3)-C(303)
91.5(7)
94.9(8)
99.4(8)
C(201)-Os(2)-C(203)
C(301)-Os(3)-C(302)
C(302)-Os(3)-C(303)
(D) Angles Involving Metal-Coordinated Carbon in C60
C(2)-C(1)-C(6)
C(2)-C(3)-C(4)
C(4)-C(5)-C(6)
121(1)
121(1)
121(1)
C(1)-C(2)-C(3)
C(3)-C(4)-C(5)
C(1)-C(6)-C(5)
119(1)
118(1)
120(1)
F igu r e 4. Molecular geometry and atomic-labeling scheme
for 8.
Ta ble 2. Selected In ter a tom ic Dista n ces (Å) a n d
Esd ’s for 8‚1.5CS2
The Os(1)-Os(2) distance (2.956(1) Å) is notably
longer than the other two Os-Os distances (2.888(1)
and 2.907(1) Å), which is apparently ascribed to the
repulsion between the phenyl groups of the phosphine
ligand and the carbonyl ligands on Os(2) atom. The
average Os-Os distance for 8 (2.917(1) Å) is longer than
that for Os3(CO)12 (2.877(3) Å).14 The Os-C(C60) bonds
alternate in length, with the average long distance of
2.31(1) Å and the average short distance of 2.26(3) Å,
which leads to the slight twist of the C6 ring of the C60
ligand over the triangular Os3 framework. However,
the carbon-carbon bonds of the C6 ring do not appear
to alternate in length, ranging from 1.43(2) Å to 1.48-
(2) Å (av 1.46(2) Å). 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° 15
[cf. 40(2)° for 15 and 41(2)° for Pt(PPh3)2(η2-C60)15]. A
small degree of bond alternation, however, has been
observed for the benzene analogue 13 (av 1.43(2) and
av 1.40(2) Å)8 and for the triruthenium complex 12 (av
1.466(15) and 1.427(19) Å).7
(A) Metal-Metal Distances
Os(1)-Os(2)
Os(2)-Os(3)
2.956(1)
2.907(1)
Os(1)-Os(3)
2.888(1)
(B) Metal-Carbon (Carbonyl) Distances
Os(1)-C(101)
Os(2)-C(201)
Os(2)-C(203)
Os(3)-C(302)
1.89(2)
1.92(2)
1.87(2)
1.88(2)
Os(1)-C(102)
Os(2)-C(202)
Os(3)-C(301)
Os(3)-C(303)
1.84(2)
1.92(2)
1.91(2)
1.90(2)
(C) Metal-Phosphorus Distances
Os(1)-P
2.370(4)
(D) Carbon-Oxygen (Carbonyl) Distances
C(101)-O(101)
C(201)-O(201)
C(203)-O(203)
C(302)-O(302)
1.15(2)
1.13(2)
1.15(2)
1.15(2)
C(102)-O(102)
C(202)-O(202)
C(301)-O(301)
C(303)-O(303)
1.16(2)
1.12(2)
1.15(2)
1.15(2)
(E) Metal-Carbon (C60) Distances
Os(1)-C(1)
Os(2)-C(3)
Os(3)-C(5)
2.32(1)
2.31(1)
2.31(1)
Os(1)-C(2)
Os(2)-C(4)
Os(3)-C(6)
2.30(1)
2.22(1)
2.25(1)
(F) Distances within the C60 Ligand
C(1)-C(2)
C(3)-C(4)
C(5)-C(6)
1.43(2)
1.48(2)
1.45(2)
C(2)-C(3)
C(4)-C(5)
C(1)-C(6)
1.45(2)
1.46(2)
1.46(2)
The molecular structure of 8 is derived from that of
Os3(CO)11(PPh3) by replacing three axial carbonyl groups
on three osmium atoms with the C60 ligand. A six-
membered carbon ring (C6 ring) of the C60 ligand
positions centrally over the Os3 framework, as was
shown in Ru3(CO)9(µ3-η2,η2,η2-C60) (12).7 The C6 ring
is essentially parallel with the Os3 plane with a dihedral
angle of 1.2° [cf. 0.9° for 127 and 1.2° for Os3(CO)8(PPh3)-
(µ3-η2,η2,η2-C6H6) (13)8]. The two Os(CO)3 and one Os-
(CO)2(PPh3) units are slightly twisted, all in the same
direction, so that the three axial carbonyls are disposed
in a propeller-like configuration. Each pair of equatorial
ligands is placed one above and one below the Os3 plane.
The bulky phosphine ligand occupies an equatorial
position and is disposed away from the C60 ligand,
presumably due to its unfavorable steric interaction
with the C60 ligand.
All other features of the molecular geometry are
within the expected range. The average C-C bond
length at the junctions of the 5,6 ring is 1.45(2) Å, and
that at the junctions of the 6,6 ring is 1.39(2) Å. The
Os-CO distances range from 1.84(2) to 1.92(2) Å, C-O
bond lengths range from 1.12(2) through 1.16(2) Å, and
Os-C-O angles are in the range of 174(2)-179(2)°.
The CS2 solvate molecules do not enter into any
significant interactions with molecule 8.
(14) Churchill, M. R.; DeBore, B. G. Inorg. Chem. 1977, 16, 878.
(15) Fagan, P. J .; Calabrese, J . C.; Malone, B. Science 1991, 252,
1160.

4482 Organometallics, Vol. 17, No. 20, 1998
Song et al.
Ta ble 4. Cr ysta l a n d Str u ctu r e Deter m in a tion
Da ta for 8‚1.5CS2
Exp er im en ta l Section
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, LLC) was used without
further purification. Anhydrous trimethylamine N-oxide (mp
225-230 °C) was obtained from Me3NO‚2H2O (98%, Aldrich
Chemical Ltd.) by sublimation (three times) at 90-100 °C
formula
fw
system
space group
a, Å
C86H15O8POs3‚1.5CS2
1891.74
monoclinic
C2/c
24.9899(4)
10.0038(1)
45.6698(5)
90.663(1)
11416.4(2)
8
b, Å
c, Å
â, deg
V, Å3
Z
under vacuum. Os3(CO)11(NCMe),16 Os3(CO)9(µ3-η2,η2,η2-C60
)
(6),5 and Os3(CO)8(PMe3)(µ3-η2,η2,η2-C60) (7)5 were prepared by
the literature methods. Carbon-13 (*C) CO enriched com-
plexes were prepared by using Os3(*CO)12 (ca. 35% enrich-
ment).17 Preparative thin layer plates were prepared with
silica gel GF254 (type 60, E. Merck).
D
calcd, Mg m-3
2.201
temp, K
293(2)
λ (Mo KR), Å
0.71073
6.886
0.49-1.00
23468
7926
6896
0.0630
0.1339
µ, mm-1
transmission factors
no. of rflns measd
no. of unique rflns
no. of rflns (Fo > 4σ(Fo))
Infrared spectra were obtained on a Bruker EQUINOX-55
FT-IR spectrophotometer. 1H (300 MHz), 13C (75 MHz), and
31P (122 MHz) NMR spectra were recorded on a Bruker AM-
300 spectrometer. Positive ion FAB mass spectra (FAB+) were
obtained by the staff of the Korea Basic Science Center. All
m/z values are referenced to 192Os. Elemental analyses were
provided by the staff of the Agency for Defense Development.
a
Rf
b
Rw
a
b
2
Rf ) ∑||Fo| - |Fc||/∑|Fo|. Rw ) [∑ω(|Fo| - |Fc|)2/∑ω|Fo| ]1/2
.
13C NMR Da ta (C60 Region ) of 6 a n d 7. Compound 6:
13C{1H} NMR (C6H4Cl2/ext. CD2Cl2, 298 K) δ 153.8 (6C), 151.4
(3C), 148.2 (6C), 146.7 (6C), 145.1 (6C), 145.0 (6C), 144.7 (6C),
143.9 (3C), 143.7 (6C), 143.3 (3C), 142.7 (3C), 61.2 (6C, C60
sp3 carbon). Compound 7: 13C{1H} NMR (C6H4Cl2/ext. CD2-
Cl2, 298 K) δ 156.1 (1C), 154.3 (2C), 152.2 (2C), 151.5(1C),
147.9 (2C), 147.7 (2C), 147.6 (2C), 146.1 (2C), 146.1 (2C), 146.0
(2C), 145.0 (2C), 144.8 (2C), 144.8 (2C), 144.3 (2C), 144.2 (2C),
144.2 (2C), 144.1 (2C), 144.0 (2C), 143.9 (2C), 143.8 (2C), 143.7
(2C), 143.4 (2C), 143.3 (2C), 142.9 (1C), 142.7 (2C), 142.3 (2C),
142.1 (1C), 142.0 (2C), 142.0 (2C), 57.2 (2C, C60 sp3 carbon),
57.1 (2C, C60 sp3 carbon), 56.7 (2C, C60 sp3 carbon).
for C74H18O7P2S2Os3 (9‚CS2): C, 52.3; H, 1.06; S, 3.74. Found:
C, 52.6; H, 0.87; S, 3.75.
Electr och em ica l Mea su r em en ts. Cyclic voltammetry
and chronoamperometry were carried out on a BAS 100B
(Bioanalytical Systems, Inc.) 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 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 1,2-dichlo-
robenzene solution of [(n-Bu)4N]ClO4. The concentrations of
compounds are ca. 3 × 10-4 M. All potentials are 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 vs (time)-1/2 according
to the Cottrell equation.18
X-r a y Str u ctu r e Deter m in a tion for 8‚1.5CS2. Crystals
of 8 suitable for an X-ray analysis were grown at room
temperature from a carbon disulfide solution of 8. A dark
brown crystal with approximate dimensions 0.89 × 0.09 × 0.09
mm was mounted on a glass fiber, transferred to a Siemens
SMART diffractometer/CCD area detector employing a 3 kW
sealed tube X-ray source operating at 2 kW, and centered in
the beam.19 Data were collected at room temperature for 12
h. Preliminary orientation matrix and cell constants were
determined with a set of 20 data frames with 30 s collection
per frame, followed by spot integration and least-squares
refinement. A hemisphere of data was collected using 0.3° ω
scans at 30 s per frame. The raw data were integrated (XY
spot spread ) 1.60, Z spot spread ) 0.6), and the unit cell
parameters were refined using SAINT.20 Data analysis and
absorption correction were performed by using Siemens
XPREP.21 The data were corrected for Lorentz and polariza-
tion effects, but no correction for crystal decay was applied.
Details of the relevant crystallographic data are given in Table
4. Scattering factors and anomalous dispersion terms were
taken from standard tables.
P r epar ation of Os3(CO)8(P P h 3)(µ3-η2,η2,η2-C60) (8). Com-
pound 6 (20.0 mg, 0.0130 mmol) and an excess amount (10.2
mg, 0.0389 mmol) of PPh3 were dissolved in chlorobenzene (20
mL). The solution was cooled to 0 °C, and an acetonitrile
solution (3 mL) of anhydrous Me3NO (1.1 mg, 0.015 mmol) was
added dropwise. 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). The reaction mixture was stirred at 100 °C for 1 h.
The solvent was evaporated, and the residue was purified by
preparative TLC (CS2) to afford compound 8 (11.5 mg, 0.0065
mmol, 50%, Rf ) 0.4) as a brown solid: IR (CS2) ν(CO) 2064
(vs), 2033 (s), 2013 (m), 1999 (m), 1983 (m), 1952(w) cm-1; 1H
NMR (CDCl3, 298 K) δ 7.35 (m, 18H); 31P{1H} NMR (CDCl3,
298 K) δ 9.64 (s); 13C{1H} NMR (C6H4Cl2/ext. CD2Cl2, 298 K)
2
δ 184.8 (d, J PC ) 5.7 Hz, 2CO), 177.6 (s, 6CO); MS (FAB+)
m/z 1778 (M+). Anal. Calcd for C89H15O8PS6Os3 (8‚3CS2): C,
53.3; H, 0.75; S, 9.59. Found: C, 53.6; H, 0.40; S, 10.4.
P r epar ation of Os3(CO)7(P Me3)2(µ3-η2,η2,η2-C60) (9). Com-
pound 6 (30.0 mg, 0.0194 mmol) was dissolved in chloroben-
zene (20 mL), and an excess amount (0.01 mL, 0.1 mmol) of
PMe3 was added. The solution was cooled to 0 °C, and an
acetonitrile solution (6 mL) of anhydrous Me3NO (2.9 mg, 0.039
mmol, 2 equiv) was added dropwise. The reaction mixture was
allowed to warm to room temperature for 1 h. Evaporation of
the solvent and purification by preparative TLC (CS2) produced
compound 9 (15.5 mg, 0.0095 mmol, 49%, Rf ) 0.2) as a black
solid: IR (CS2) ν(CO) 2040 (vs), 2001 (s), 1985 (s), 1972 (m),
1957 (m), 1925(m) cm-1 1H NMR (CDCl3, 298 K) δ 1.92 (d,
;
2J PH ) 10.1 Hz, 18H);13C{1H} NMR (C6H4Cl2/ext. CD2Cl2, 298
K) δ 187.8 (br, 4CO), 180.0 (s, 3CO); 31P{1H} NMR (CDCl3,
298 K) δ -49.6 (s); MS (FAB+) m/z 1640 (M+). Anal. Calcd
(18) Bard, A. J .; Faulkner, L. R. Electrochemical Methods; J ohn
Wiley & Sons: New York, 1980; pp 142-146.
(19) SMART Area-Detector Software Package; Siemens Analytical
Instrumentation, Inc.: Madison, WI, 1995.
(20) SAINT; SAX Area-Detector Integration Program, version 4.050;
Siemens Analytical Instrumentation, Inc.: Madison, WI, 1995.
(21) XPREP: part of the SHELXTL, Crystal Structure Determina-
tion Package, version 5.04; Siemens Analytical Instrumentation, Inc.:
Madison, WI, 1994.
(16) J ohnson, B. F. G.; Lewis, J .; Pippard, D. A. J . Chem. Soc.,
Dalton Trans. 1981, 407.
(17) Clauss, A. D.; Tachikawa, M.; Shapley, J . R.; Pierpont, C. G.
Inorg. Chem. 1981, 20, 1528.

µ3-η2,η2,η2-C60 Triosmium Complexes
Organometallics, Vol. 17, No. 20, 1998 4483
The structure was determined by direct methods; positions
for the osmium atoms were deduced from an E map. One cycle
of isotropic least-squares refinement followed by an un-
weighted difference Fourier synthesis revealed positions for
the osmium and remaining non-hydrogen atoms. Hydrogen
atoms were not included in the final structure factor calcula-
tions. All non-hydrogen atoms were refined with anisotropic
thermal coefficients. Successful convergence of full-matrix
least-squares refinement on F2 was indicated by the maximum
shift/error for the final cycle. The final difference Fourier map
had no significant features. For all computations the SHELX93
4σ(Fo)] were Rf ) 0.0630, Rw ) 0.1339, with (∆/σ)max ) 0.001,
∆Fmax/∆Fmin ) 2.029/-2.277 e/Å3 in the final ∆F map, and S )
1.274.
Ack n ow led gm en t. We are grateful to the Korea
Advanced Institute of Science and Technology (KAIST)
for financial support of this research. We thank Prof.
J . Kwak at KAIST for help in electrochemical measure-
ments.
Su p p or tin g In for m a tion Ava ila ble: A figure of the
molecular geometry with a complete atomic-labeling scheme,
and tables of atomic coordinates and equivalent isotropic
displacement parameters, anisotropic displacement param-
eters, and complete bond lengths and angles for complex 8 (13
pages). Ordering information is given on any current mast-
head page.
package22 was used, and the function minimized was ∑ω(|Fo|
2
- |Fc|)2, with ω ) 1/[σ2(Fo2) + (0.1123P)2], where P ) (Fo
+
2Fc2)/3. The number of parameters refined was 888. Final
reliability factors for 7926 unique observed reflections [Fo
>
(22) Sheldrick, G. M. SHELX93, Program for Crystal Structure
Refinement; University of Go¨ettingen, Germany, 1993.
OM980361B