Synthesis, characterization and properties of new organocobalt complexes containing η5-functionally substituted cyclopentadienyl and [60]fullerene ligands

Article abstract of DOI:10.1016/S0022-328X(03)00632-6

The organocobalt complexes containing functionally substituted cyclopentadienyl ligands (η⁵-RC₅H₄) Co(PPh₃)₂ (1a, R = EtO₂C; 1b, R=MeCO) were synthesized by reactions of the corresponding f

Full text of DOI:10.1016/S0022-328X(03)00632-6

Journal of Organometallic Chemistry 681 (2003) 264Á268
/
www.elsevier.com/locate/jorganchem
Synthesis, characterization and properties of new organocobalt
complexes containing h5-functionally substituted cyclopentadienyl
and [60]fullerene ligands
Li-Cheng Song a,*, Peng-Chong Liu a, Qing-Mei Hu a,b, Guo-Liang Lu a,
Guang-Feng Wang a
a State Key Laboratory of Elemento-Organic Chemistry, Department of Chemistry, Nankai University, Tianjin 300071, China
b Laboratory of Organometallic Chemistry, Chinese Academy of Sciences, Shanghai 200032, China
Received 7 May 2003; received in revised form 26 June 2003; accepted 26 June 2003
Abstract
The organocobalt complexes containing functionally substituted cyclopentadienyl ligands (h5-RC5H4)Co(PPh3)2 (1a, Rꢀ
1b, RꢀMeCO) were synthesized by reactions of the corresponding functionalized cyclopentadienides RC5H4Na with (PPh3)3CoCl
in 65 and 85% yields, respectively. The ligand exchange reaction of 1a with PhCÅ
CPh afforded (h5-EtO2CC5H4)Co(PPh3)( h2-PhCÅ
CPh) (2a) in 72% yield, whereas (h5-RC5H4)Co(PPh3)2 (1a, Rꢀ
EtO2C; 1b, RꢀMeCO; 1c, RꢀH) reacted with C60 through ligand
exchange to give (h5-RC5H4)Co(PPh3)(h2-C60) (3a, Rꢀ
EtO2C; 3b, RꢀMeCO; 3c, RꢀH) in 34Á68% yields. 3a could be also
obtained similarly by ligand exchange reaction of 2a with C60 in 83% yield. In addition, reaction of 2a or 3a with excess iodine I2
produced (h5-EtO2CC5H4)Co(PPh3)(I)2 (4a) in 90Á
91% yields. The new compounds 1a, 1b, 2a, 3aÁ3c and 4a were characterized by
1H-NMR, 31P-NMR, IR, UVÁ
Vis spectra and elemental analysis, whereas the reverse saturable absorption properties of the
/EtO2C;
/
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organocobalt fullerene complexes 3a and 3c along with C60 were studied by Z-scan method.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Organocobalt complexes; [60]Fullerene complexes; Synthesis; Reverse saturable absorption
1. Introduction
ligands [5]. In this article, we wish to report the
formation and characterization of the new complexes
containing h5-functionally substituted cyclopentadienyl
In recent years, the organocobalt complexes contain-
ing functionally substituted cyclopentadienyl ligands
have played an important role in the development of
organocobalt chemistry. However, the studies in this
area were mainly focused on the transformation reac-
tions of the functional groups on the cyclopentadienyl
ligands (h5-RC5H4)Co(PPh3)2 (1a, Rꢀ
/
EtO2C; 1b,
MeCO), and a series of ligand exchange reactions
occurring at the cobalt metal center with PhCÅCPh,
C60 and I2, leading to the corresponding new cobalt
complexes (h5-EtO2CC5H4)Co(PPh3) (h2-PhCÅ
CPh)
(2a), (h5-RC5H4)Co(PPh3)(h2-C60) (3a, Rꢀ
EtO2C; 3b,
MeCO; 3c, Rꢀ
H) and (h5-EtO2CC5H4)Co(PPh3)(I)2
/
/
ring [1Á4], while no report is so far concerned about the
/
/
ligand exchange reactions with fullerenes that take place
at the cobalt metal center, although a few of such
reactions are known to occur with other common
/
(4a), respectively. Furthermore, the reverse saturable
absorption properties of organocobalt fullerene com-
plexes were first studied by Z-scan method, which
indicated that the organocobalt [60]fullerene complexes
3a and 3c possess much better reverse saturable absorp-
tion properties than C60 itself.
* Corresponding author. Tel.: ꢁ
2350-4853.
E-mail address: lcsong@public.tpt.tj.cn (L.-C. Song).
/
86-22-2350-4452; fax: ꢁ86-22-
/
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00632-6

L.-C. Song et al. / Journal of Organometallic Chemistry 681 (2003) 264Á
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265
Scheme 1.
Scheme 3.
2. Results and discussion
the order of PPh3B
/
PhCÅ
/
CPhB
/
C60B
/
2I. This is be-
cause that the stronger electron-withdrawing ability of
the ligands L would make the weaker p-back donation
from cobalt metal center to functionally substituted
cyclopentadienyl ligand [7].
In the 1H-NMR spectra, while the protons of the
parent cyclopentadienyl ring in 3c showed one singlet at
4.32 ppm, those of the substituted cyclopentadienyl
rings in 1a, 1b, 2a, 3a, 3b and 4a exhibited two singlets in
2.1. Synthesis and characterization of (h5-RC5H4)-
Co(PPh3)2 (1a, RꢀEtO2C; 1b, Rꢀ
MeCO), (h5-
EtO2CC5H4)Co(PPh3)(h2-PhCÅCPh) (2a), (h5-
RC5H4)Co(PPh3)(h2-C60) (3a, Rꢀ
EtO2C; 3b,
MeCO; 3c, Rꢀ
H) and (h5-EtO2CC5H4)Co(PPh3)(I)2
(4a)
/
/
/
/
/
We found that 1a and 1b could be prepared by
reaction of the corresponding functionalized cyclopen-
tadienides RC5H4Na with (PPh3)3CoCl in benzene/THF
at room temperature in 65 and 85% yields, respectively
(Scheme 1), whereas further reaction of 1a with diphe-
nylacetylene in benzene at room temperature, through
ligand exchange reaction produced 2a in 72% yield
(Scheme 2).
the range 3.33Á5.90 ppm, the downfield one being
/
assigned to H2 and H5 protons and the upfield one to
H3 and H4 protons since the substituents EtO2C and
MeCO are both electron-withdrawing [8].
Although numerous transition-metal h2-[60]fullerene
complexes have been reported so far [9], little is known
for the complexes in which C60 is directly bound to
cobalt atom in an h2-fashion [10]. In this article, as part
of our fullerene project [11], we report the above two
Interestingly, we further found that the [60]fullerene
organocobalt complexes (h5-RC5H4)Co(PPh3)(h2-C60)
routes for synthesizing such complexes. 3aÁ3c are very
/
(3a, Rꢀ
prepared by ligand exchange reaction of 1aÁ
RꢀH [6]) with C60 in toluene at room temperature in
34Á68% yields, whereas 3a could be also obtained by a
/
EtO2C; 3b, MeCO; 3c, Rꢀ/H) could be
air-sensitive, dark-green solids, which do not dissolve in
hexane and acetone but are fairly soluble in benzene,
/1c (1c,
/
toluene, CS2, CHCl3 and THF. The solutions of 3aÁ3c
/
/
in such solvents are extremely air-sensitive and ther-
mally unstable, which decompose to give C60 completely
within 24 h even at room temperature under an argon
atmosphere. The elemental data coincide with their
formulas, while the FAB-MS spectra displayed their
molecular ion [Mꢁ] peaks and the fragment ion [C60]ꢁ
peak, respectively. Except the IR bands mentioned
ligand exchange reaction of 2a with C60 in 83% yield
(Scheme 3).
Finally, we found that both 2a and 3a reacted with
excess iodine I2 in CH2Cl2 at room temperature,
through ligand exchange reactions, to give 4a in 90Á
91% yields (Scheme 4).
All the complexes 1a, 1b, 2a, 3aÁ
/
/3c and 4a prepared
above, 3aÁ
the region 523Á
the C60 cage [12]. The UVÁ
/
3c each showed four absorption bands in
1434 cmꢂ1, which are characteristic of
Vis spectra of 3a and 3c
above are air-sensitive, which were characterized by
elemental analysis and spectroscopy. The IR spectra of
1a, 1b, 2a, 3a, 3b and 4a each displayed one absorption
/
/
band in the range 1666Á
functionalities in EtO2C and MeCO groups. For the
complexes with
general formula of (h5-
EtO2CC5H4)Co(PPh3)L (1a, LꢀPPh3; 2a, LꢀPhCÅ
CPh; 3a, LꢀC60; 4a, Lꢀ2I), the nCÄO values increase
in the order of 1a (1686 cmꢂ1)B2a (1696 cmꢂ1)B
3a
(1713 cmꢂ1)B4a (1724 cmꢂ1). This implies that the
/
1724 cmꢂ1 for the carbonyl
displayed two intense bands between 200 and 400 nm,
which are very close to those of free C60; the small
a
changes in their UVÁVis spectra, as compared with free
/
C60, may be regarded as an evidence for the h2-
coordinating fashion of the C60 ligand through its [6:6]
bond to the cobalt metal center [10]. In addition, each of
/
/
/
/
/
/
/
the 31P-NMR spectra of 3aÁ
3c exhibited one singlet at
/
/
electron-withdrawing effects of the ligands L increase in
Scheme 2.
Scheme 4.

266
L.-C. Song et al. / Journal of Organometallic Chemistry 681 (2003) 264Á268
/
ca. 50 ppm, which is also consistent with the structures
described in Scheme 3.
Table 1
The minimum relative transmission values (Tmin) and the reverse
saturable absorption coefficients (Da) of C60, 3a and 3c
Da (cm2 Wꢂ1
)
2.2. Reverse saturable absorption properties of (h5-
RC5H4)Co(PPh3)(h2-C60) (3a and 3c) and C60
Tmin
C60
3a
0.60
0.43
0.34
3.9ꢃ
9.9ꢃ
1.3ꢃ
/
10ꢂ10
10ꢂ10
10ꢂ9
/
3c
/
The nonlinear optical properties of [60]fullerene and
its derivatives have attracted much attention, largely due
to their potential applications as optical limiting materi-
commercially. MeCOC5H4Na [1], EtO2CC5H4Na [3],
CpCo(PPh3)2 [6] and (PPh3)3CoCl [17] were prepared
als [13Á16]. Recently, we studied the nonlinear optical
/
reverse saturable absorption properties of the triplet
excited state of C60 and its derivatives 3a and 3c by
means of Z-scan techniques. Fig. 1 presents the reverse
saturable absorption curves of C60, 3a and 3c, and the
reverse saturable absorption coefficients calculated from
the minimum relative transmission values are listed in
Table 1.
according to literature methods. Products 2a, 3aÁ
4a were separated by column chromatography (1.5ꢃ
cm2, silica gel) and purified by recrystallization from
/
3c and
/
30
toluene/petroleum ether at low temperature (ꢂ
/
20Á0 8C)
/
under anaerobic conditions. H- and 31P-NMR spectra
were recorded on a Bruker AC P200 and a Varian
1
Mercury VX300 spectrometer, respectively. UVÁVis
/
As can be seen from Fig. 1 and Table 1, the minimum
transmission values (Tmin) of 3a and 3c are remarkably
lower than that of free C60 and the reverse saturable
absorption coefficients (Da) of 3a and 3c are as large as
ca. 2.5 and 3.3 times of [60]fullerene, respectively. These
suggest that 3a and 3c possess stronger reverse saturable
absorption behavior than C60 itself, since Tmin and,
particularly, Da obtained under the same power density
and the same concentration of the samples can reflect
the magnitude of reverse saturable absorption. It follows
that the reverse saturable absorption property of free
C60 has been well improved through its coordination
with cobalt atom in organometallic compounds.
and IR spectra were determined using a Shimadzu UV
240 and a Bio-Rad FTS 135 spectrometer, respectively.
Elemental analysis was performed on an Elementar
Vario EL analyzer, while FAB-MS spectra were deter-
mined by a Zabspec spectrometer. Melting points were
determined in a sealed capillary by a Yanaco MP-500
apparatus and are uncorrected.
3.1. Preparation of (h5-EtO2CC5H4)Co(PPh3)2 (1a)
A 50 ml three-necked flask equipped with a magnetic
stir-bar, a serum cap and a nitrogen inlet tube was
charged with 1.90 g (2.16 mmol) of (PPh3)3CoCl, 20 ml
of benzene and 0.50 g (3.10 mmol) of EtO2CC5H4Na in
4 ml of THF. The mixture was stirred at room
temperature for 2 h and then 10 ml of water was added.
The organic layer was separated from the mixture, dried
over sodium sulfate and filtered. The filtrate was
concentrated to ca. 8 ml under reduced pressure, and
then 8 ml of petroleum ether was added to give a
precipitate. The precipitate was washed with petroleum
ether and dried in vacuo to give 1.00 g (65%) of 1a as
dark-red powders. m.p.: 154 8C (dec.). Anal. Found: C,
3. Experimental
All reactions were carried out under a highly purified
nitrogen atmosphere using standard Schlenk or vacuum-
line techniques. Toluene, benzene and tetrahydrofuran
were dried and deoxygenated by distillation from Na/
benzophenone ketyl. All organic solvents and water
were bubbled with nitrogen before use for at least 15 and
30 min, respectively. [60]Fullerene (99.9%) was available
Fig. 1. Reverse saturable absorption curves of the toluene solutions (1.0ꢃ
10-3 mol/l) of C60, 3a and 3c.
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L.-C. Song et al. / Journal of Organometallic Chemistry 681 (2003) 264Á
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267
73.03; H, 5.51. Calc. for C44H39CoO2P2: C, 73.33; H,
5.45%. IR (KBr disk, cmꢂ1): nCÄO 1686s. 1H-NMR
ene, nm): l (log o) 282.0 (1.535), 336.0 (1.370). FAB-MS
m/z: 1178[Mꢁ].
(C6D6): dꢀ
H3, H4), 4.49 (q, Jꢀ
H5), 7.07Á
7.78 (m, 30H, 6C6H5) ppm.
/
1.31(t, Jꢀ
/
7.0 Hz, 3H, CH3), 4.20 (s, 2H,
Similarly, when 0.038 g (0.06 mmol) of 2a was used
instead of 1a, 0.049 g (83%) of 3a was also obtained.
/
7.0 Hz, 2H, CH2), 4.85 (s, 2H, H2,
/
3.5. Preparation of (h5-MeCOC5H4)Co(PPh3)(h2-C60)
(3b)
3.2. Preparation of (h5-MeCOC5H4)Co(PPh3)2 (1b)
Similar to the preparation of 3a, when 0.035 g (0.051
mmol) of 1b was used instead of 1a, 0.039 g (68%) of 3b
was obtained as dark-green powders. m.p.: 80 8C (dec.).
Anal. Found: C, 88.95; H, 2.14. Calc. for C85H22CoOP:
C, 88.85; H, 1.93%. IR (KBr disk, cmꢂ1): nC60 526vs,
577s, 1183m, 1430s; nCÄO 1669s. 1H-NMR (CS2,
The flask described above was charged with 1.90 g
(2.16 mmol) of (PPh3)3CoCl, 20 ml of benzene and 0.406
g (3.12 mmol) of MeCOC5H4Na in 4 ml of THF. After
the same procedure as in the preparation of 1a, 1.30 g
(85%) of 1b was obtained as dark-red powders. m.p.:
121 8C (dec.). Anal. Found: C, 74.71; H, 5.15. Calc. for
CD3COCD3 lock signal): dꢀ
(s, 2H, H3, H4), 5.46 (s, 2H, H2, H5), 7.38Á
3C6H5) ppm. 31P-NMR (C6D6): dꢀ
51.71 ppm. FAB-
MS m/z: 1148[Mꢁ].
/2.54 (s, 3H, CH3), 3.56
C43H37CoOP2: C, 74.78; H, 5.40%. IR (KBr disk,
cmꢂ1): nCÄO 1666s. H-NMR (CD3COCD3): dꢀ
1
/7.94 (m, 15H,
/
3.03
(s, 3H, CH3), 3.33 (s, 2H, H3, H4), 4.66 (s, 2H, H2, H5),
7.17Á7.33 (m, 30H, 6C6H5) ppm.
/
/
3.6. Preparation of (h5-C5H5)Co(PPh3)(h2-C60) (3c)
3.3. Preparation of (h5-EtO2CC5H4)Co(PPh3)(h2-
PhCÅCPh) (2a)
/
Similar to the preparation of 3a, when 0.033 g (0.05
mmol) of (h5-C5H5)Co(PPh3)2 was used instead of 1a,
0.190 g (34%) of 3c was obtained as dark-green powders.
m.p.: 110 8C (dec.). Anal. Found: C, 90.21; H, 1.58.
Calc. for C83H20CoP: C, 90.06; H, 1.82%. IR (KBr disk,
cmꢂ1): nC60 523vs, 580m, 1179m, 1417s. 1H-NMR (CS2,
The flask described above was charged with 0.60 g
(0.83 mmol) of 1a, 8 ml of benzene and 0.135 g (0.76
mmol) of diphenylacetylene. The mixture was stirred at
room temperature for 2 h. Solvent was removed and the
residue was subjected to column chromatography. The
major green band was eluted using benzene to give 0.35
g (72%) of 2a as green powders. m.p.: 99 8C (dec.). Anal.
Found: C, 75.33; H, 5.38. Calc. for C40H34CoO2P: C,
CD3COCD3 lock signal): dꢀ
/
4.32 (s, 5H, C5H5), 6.69Á
/
7.36 (m, 15H, 3C6H5) ppm. 31P-NMR (C6D6): dꢀ
/53.11
ppm. UVÁVis (toluene, nm): l (log o) 283.1 (0.773),
/
337.7 (0.693). FAB-MS m/z: 1106[Mꢁ].
75.47; H, 5.35%. IR (KBr disk, cmꢂ1): nCÄO 1696s, nCÅC
1
3.7. Preparation of (h5-EtO2CC5H4)Co(PPh3)I2 (4a)
1827m. H-NMR (C6D6): dꢀ
/
1.08 (t, Jꢀ
7.0 Hz, 2H, CH2), 5.06 (s, 2H, H3,
H4), 5,32 (s, 2H, H2, H5), 7.04Á
8.15 (m, 25H, 5C6H5)
ppm. UVÁVis (toluene, nm): l (log o) 282.0 (1.960),
/7.0 Hz, 3H,
CH3), 4.19 (q, Jꢀ
/
/
The flask described above was charged with 0.087 g
(0.140 mmol) of 2a, 10 ml of dichloromethane and 0.072
g (0.28 mmol) of I2. The mixture was stirred at room
temperature for 0.5 h and then was subjected to column
chromatography. The dark-blue band was eluted with
dichloromethane, from which 0.09 g (90%) of 4a was
obtained as dark-blue powders. m.p.: 138 8C (dec.).
Anal. Found: C, 43.69; H, 3.60. Calc. for
/
288.0 (1.695), 298.0 (1.660) ppm.
3.4. Preparation of (h5-EtO2CC5H4)Co(PPh3)(h2-C60)
(3a)
The flask described above was charged with 0.036 g
(0.05 mmol) of C60 and 20 ml of toluene. The C60
solution was stirred at room temperature and 0.04 g
(0.06 mmol) of 1a in 6 ml of toluene was added
gradually. The mixture was stirred for 2 h at this
temperature and then was subjected to column chroma-
tography. The main green band was eluted using toluene
to give 0.025 g (43%) of 3a as dark-green powders. m.p.:
135 8C (dec.). Anal. Found: C, 87.40; H, 1.95. Calc. for
C86H24CoO2P: C, 87.61, H 2.05%. IR (KBr disk, cmꢂ1):
C26H24CoI2O2P: C, 43.85; H, 3.40%. IR (KBr disk,
1
cmꢂ1): nCÄO 1724s. H-NMR (CDCl3): dꢀ
/
1.44 (t, Jꢀ
7.2
7.80 (m, 15H,
/
7.2 Hz, 3H, CH3), 4.19 (s, 2H, H3, H4), 4.45 (q, Jꢀ
Hz, 2H, CH2), 5.90 (s, 2H, H2, H5), 7.47Á
3C6H5) ppm.
/
/
Similarly, when using 0.012 g (0.01 mmol) of 3a
instead of 2a, 0.0065 g (91%) of 4a was obtained.
3.8. Determination of the reverse saturable absorption
properties of 3a and 3c and C60
1
nC60 523vs, 580m, 1179m, 1434s; nCÄO 1713s. H-NMR
(CS2, CD3COCD3 lock signal): dꢀ
3H, CH3), 3.60 (q, Jꢀ6.7 Hz, 2H, CH2), 3.93 (s, 2H,
H3, H4), 4.68 (s, 2H, H2, H5), 6.70-7.30 (m, 15H, 3C6H5)
ppm. 31P-NMR (C6D6): dꢀ
50.76 ppm. UVÁVis (tolu-
/
0.60 (t, Jꢀ
/
6.7 Hz,
/
The reverse saturable absorption properties of 3a and
3c and C60 were determined by the Z-scan method [18].
The wave length, pulse width and pulse frequency of the
/
/

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L.-C. Song et al. / Journal of Organometallic Chemistry 681 (2003) 264Á268
/
[6] H. Yamazaki, Y. Wakatsuki, J. Organomet. Chem. 139 (1977)
157.
laser beam (generated by a T49-ZE quadruple Nd:YAG
laser manufactured by Beijing Radio Equipment Plant)
are 532 nm, 18 ns and 10 Hz, respectively. The laser
beam passed through a lens (15-cm focal length), and
irradiated on a sample cell (5-mm in thickness), which
[7] J.P. Collman, L.S. Hegedus, Principles and Applications of
Organotransition Metal Chemistry, University Science Books,
Mill Valley, CA, 1980, p. 86.
[8] L.-C. Song, J.-Y. Shen, Q.-M. Hu, X.-Y. Huang, Organometallics
14 (1995) 98.
was filled with a 1.0ꢃ
10ꢂ3 mol/l toluene solution of 3a,
/
[9] A.L. Balch, M.M. Olmstead, Chem. Rev. 98 (1998) 2123.
[10] A.N. Chernega, M.L.H. Green, J. Haggiitt, A.H.H. Stephens, J.
Chem. Soc. Dalton Trans. (1998) 755.
3c or C60. The transmitted light was detected by an LPE-
1B laser power/energy detector manufactured by Beijing
Wu-Ke Photoelectric Technology Company. The inten-
sity values of the transmitted light were recorded at
[11] (a) L.-C. Song, J.-T. Liu, Q.-M. Hu, G.-F. Wang, P. Zanello, M.
Fontani, Organometallics 19 (2000) 5342;
(b) L.-C. Song, Y.-H. Zhu, Q.-M. Hu, J. Chem. Res. Synop.
(2000) 316.;
every 1-cm of the Z-value in the range 0Á20 cm, with
/
which the absorption curves were drawn and the
coefficients of reverse saturable absorption were calcu-
lated.
(c) P. Zanello, F. Laschi, M. Fontani, L.-C. Song, Y.-H. Zhu, J.
Organomet. Chem. 593Á594 (2000) 7;
/
(d) Y.-H. Zhu, L.-C. Song, Q.-M. Hu, C.-M. Li, Org. Lett. 1
(1999) 1693;
(e) L.-C. Song, Y.-H. Zhu, Q.-M. Hu, Polyhedron 16 (1997)
2141;
Acknowledgements
(f) L.-C. Song, Y.-H. Zhu, Q.-M. Hu, Polyhedron 17 (1998)
469;
We are grateful to the National Natural Science
Foundation of China and the State Key Laboratory of
Organometallic Chemistry for financial support of this
work.
(g) Y.-L. Song, G.-Y. Fang, Y.-X. Wang, S.-T. Liu, C.-F. Li, L.-
C. Song, Y.-H. Zhu, Q.-M. Hu, Appl. Phys. Lett. 74 (1999)
332;
(h) L.-C. Song, Y.-H. Zhu, Q.-M. Hu, J. Chem. Res. Synop.
(1999) 56.;
(i) L.-C. Song, J.-T. Liu, Q.-M. Hu, L.-H. Weng, Organometallics
19 (2000) 1643.
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