Propylene polymerization of ansa-complexes (RXPh) 2C(Cp)(Flu)MCl2 (M = Zr or Hf) with halogen substituents on phenyl groups

Article abstract of DOI:10.1016/j.molcata.2004.10.020

The catalytic properties of (R^XPh)₂C(Cp)(Flu)MCl ₂ complexes (R^X = Cl, F or CF₃; M = Zr or Hf) in propylene polymerization were studied. The results showed dependences of stereospecificity and polymer

Full text of DOI:10.1016/j.molcata.2004.10.020

Journal of Molecular Catalysis A: Chemical 227 (2005) 147–152
Propylene polymerization of ansa-complexes (RXPh)2C(Cp)(Flu)MCl2
(M = Zr or Hf) with halogen substituents on phenyl groups
Jiling Huanga,∗, Yong Zhanga, Xiaoxia Yanga, Wei Chenb, Yanlong Qiana
a
The Laboratory of Organometallic Chemistry, East China University of Science and Technology, 130 Meilong Road,
Shanghai 200237, People’s Republic of China
Research Institute of Petroleum Processing, SINOPEC, 18 Xueyuan Road, Beijing 100083, People’s Republic of China
b
Received 22 June 2004; received in revised form 13 October 2004; accepted 14 October 2004
Available online 26 November 2004
Abstract
The catalytic properties of (RXPh)2C(Cp)(Flu)MCl2 complexes (RX = Cl, F or CF3; M = Zr or Hf) in propylene polymerization were studied.
The results showed dependences of stereospecificity and polymerization activity on the substituent on phenyl group. When RX is CF3, the
activity is 1.38 times of that of the complex with no substituent at 1 atm propylene pressure and is extremely high at 3.0 MPa propylene pressure.
The CF3 group increased the regioirregular insertion during polymerization to produce partially crystalline s-PP. When RX is halogen, the
obtained polymer has higher melting point than that obtained from the complex with no substituent.
© 2004 Elsevier B.V. All rights reserved.
Keywords: Hafnocene complexes; Fluorine; Propylene polymerization; Syndiotactic polypropylene; Zirconocene complexes
1. Introduction
et al. [6,7] synthesized complexes (MeOPh)2C(Cp){2,7-
bis-(t-Bu)-fluorenyl}MCl2, (CH3Ph)2C(Cp){2,7-bis-(t-Bu)-
The bridged metallocene complexes are good catalyst pre-
fluorenyl}MCl2 (M = Zr or Hf) with electron donating
cusors in stereospecific polymerization of ␣-olefins, and were
well studied in the last decade. Me2C(Cp)(Flu)MCl2 (M = Zr,
Hf) synthesized by Even et al. [1] were found highly active
for polymerization of propylene to syndiotactic polypropy-
lene. Then Razavi and Atwood [2] synthesized phenyl substi-
tuted bridged complexes Ph2C(Cp)(Flu)MCl2 (M = Zr or Hf)
fromwhichthesyndiotacticpolypropylenewasobtainedwith
high stereoregularity and high molecular weight. Since then
many interests have been focused on metallocene dichloride
structures with the bridged cylopentadienyl-fluorenyl ligand
skeleton. The substituents on cylopentadienyl or fluorenyl
strongly influence the catalytic activity and stereoselectivity
[3–5]. There are only a few works concerning the influences
of substituents on the phenyl groups of Ph2C(Cp)(Flu)MCl2
(M = Zr or Hf) on propylene polymerization. Kaminsky
groups (Me and MeO) and studied their catalytic be-
havior in propylene polymerization. Now we synthesized
(RXPh)2C(Cp)(Flu)MCl2 complexes (RX = Cl, F or CF3;
M = Zr or Hf) and studied their catalytic behavior in propy-
lene polymerization. It was found that the type and posi-
tion of the substituent influenced not only the activity of the
complex but also the tacticity of the polypropylene. Com-
plex 1 with the CF3 substituent at the meta positions on the
phenyl groups showed the highest activity which was 1.36
times of that of Ph2C(Cp)(Flu)ZrCl2. The obtained polymer
is syndiotactic polypropylene with lower tacticity than highly
crystalline syndiotactic polypropylenes (thermoplastic mate-
rial) from the conventional propylene polymerization catalyst
Ph2C(Cp)(Flu)ZrCl2. The increases in atactic sequences can
improve the machining, transparent and elastomeric proper-
ties of syndiotactic polypropylenes. It is known that some of
the isotactic polypropylenes with atactic blocks have inter-
esting elastomeric properties [8–11]. Elastomeric properties
∗
Corresponding author. Fax: +86 21 54282375.
E-mail address: qianling@online.sh.cn (J. Huang).
1381-1169/$ – see front matter © 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.molcata.2004.10.020

148
J. Huang et al. / Journal of Molecular Catalysis A: Chemical 227 (2005) 147–152
of polypropylene can be obtained by alternating ordered and
disordered stereogenic blocks [12]. Syndiotactic polypropy-
lene with lower tacticity may also have elastomeric properties
[13,14]. Here, we introduced the halogen or CF3 substituent
to phenyl groups in the complex (RXPh)2C(Cp)(Flu)ZrCl2 to
improve the properties of product polypropylene.
From Table 1 we found they all showed high activities in
propylenepolymerization. Especially, theactivityofcomplex
1 is as high as 3.9 × 107 g PP/mol M h at 3.0 MPa and 70 ◦C.
The substituent effects in metallocene catalysts have been
incisively reviewed [15,16]. In the metallocenes [2,7-X2-flu-
CMe2-Cp]ZrCl2, the electron-withdrawing substituent (halo-
gen) is not so effective as the electron-donating substituent
(t-Bu) in enhancing polymerization activity. Siedle et al.
reported that the electron-withdrawing substituents should
accelerate olefin polymerization because they rendered the
metal center more electropositive. But a more electroposi-
tive metal center should have enhanced interactions with the
counter ion of cocatalyst, leading to slower initialization and
propagation [16].
2. Results and discussion
The bridged cylopentadienyl-fluorenyl ligand was pre-
pared analogously to the literature [2,6]. After the conden-
sation of cyclopentadiene with substituted (F, Cl, or CF3)
benzophenons in ethanol and sodium metal for reduction,
the substituted diphenylfulvene was obtained. Then the fluo-
renyl lithium salt was allowed to react with the fulvene. By
hydrolysis the ligand was precipitated from diethyl ether as
whitesolids. Theligandwastreatedwithtwoequivalentsofn-
butyl lithium in diethyl ether and reacted with the equivalent
amount of zirconium tetrachloride or hafnium tetrachloride.
The complexes 1–6 were obtained by recrystallisation from
toluene (Fig. 1).
The complexes 1 and 2 have CF3 substituents at the meta
positions on the phenyl groups. Halogen is at the para posi-
tion on the phenyl group in complexes 4–6. Complex 3 was
synthesized for comparision. They were used for polymer-
ization of propylene in the presence of MAO. The results are
given in Table 1.
The relative activity of complexes (RXPh)2C(Cp)(Flu)-
ZrCl2 for propylene polymerization is in the order
RX = CF3 > H > halogen (F or Cl). At 1 atm propylene pres-
sure, the activity of complex 1 is 26.0 × 105 g PP/mol M h
which is 1.36 times of that of 3. But the activities of com-
plex with halogen substituents are much lower than 3, which
shows the electron-withdrawing effect is not in favor of poly-
merization. The electron-withdrawing substituent can make
metal center more electropositive and form tighter ion pair-
ing. This is not beneficial to polymerization in accordance
with what Siedle et al. reported [16]. But the CF3 substituent
which is electron-withdrawing shows a quite different effect.
So we think the position of substituent on the phenyl group
plays a key role. The CF3 substituent at the meta position is
Fig. 1. Synthesis of complexes 1–6

J. Huang et al. / Journal of Molecular Catalysis A: Chemical 227 (2005) 147–152
149
Table 1
The results of propylene polymerization with complexes 1–6
Tp (◦C)
Activitya (×10−5
)
M × 10−5
ꢀHf (J/g)
b
Tm (◦C)
c
Run no.
Complex
␩
1
2
3
4d
1
30
50
70
70
26.0
19.6
8.41
389
2.46
1.49
0.34
120
24.6
129
5
6
7
2
30
50
70
2.18
1.37
0.88
9
10
3
4
30
50
19.2
14.5
2.96
127
137
45.6
38.5
11
12
13
14
30
50
70
0
7.11
6.90
5.40
2.26
2.46
0.86
0.45
2.48
15
16
5
6
30
0
17.4
2.56
133
41.6
17
30
1.27
Conditions: Ppropylene = 1 atm, time = 0.5 h, [Al]/[M] = 1000, [M] = 0.5 × 10−4 mol/l, 50 ml toluene.
a
g PP/mol M h.
Melting peak temperature of the DSC curve.
Endothermic enthalpies determined by DSC as a parameter of the crystallinity of polymer.
Ppropylene = 3.0 MPa, time = 2 h.
b
c
d
closer to metal in space than halogen substituents at the para
positions. The active center is shielded by six fluorine atoms
and kept away from counter ion charge because the fluorine
atoms and counter ion repel each other. Although the active
center is more electropositive, the loose ion pairing should
prevail and results in enhanced interactions between metal
center and olefin. This is beneficial to the polymerization.
There is also a possibility that the steric hindrance of CF3
group leads to the concomitant changes of the structure of
the complex, facilitating the coordination and insertion of
the propylene in polymerization.
withdraws the electrons away from fluorene, thus drastically
decreasing its basicity (more electropositive). This resulted
in low molecular weights of polymers [17].
The polymer from 3 is highly crystalline syndiotac-
tic polypropylene with very high tacticity ([r] = 97.5%)
[2] and relatively long average syndiotactic block length
(Lsyn = 3 + 2 × rrrr/rrrm), for example, 50–200 monomer
units [13]. Although there are halogen substituents at the para
positions on the phenyl groups, the structure of the complex
4 remains Cs symmetrical. It also produces highly crystalline
syndiotactic polypropylene with [rrrr] = 85.1% ([r] = 95.1%)
and Lsyn = 50 as complex 3. The polypropylene from 4 has
even higher melting point than from 3 (137 ◦C > 127 ◦C)
(Table 2).
The activity of the catalyst depends on the polymerization
temperature. The activities decrease with the rise in polymer-
ization temperature from 30 to 70 ◦C. Complexes 1–6 show
the highest activity at 30 ◦C.
The Cs symmetric structure of complex 1 was destroyed
by the CF3 group at the meta positions on the phenyl groups
nonsymmetrically located. One of the CF3 group bends to-
ward cyclopentadienyl and the other bends toward fluorenyl
The viscosity molecular weight (M ) of polypropylene
␩
produced by complex 1 at 30 ◦C is almost the same as by
complex 4, and lower than that produced by complex 3. It
shows that the CF3 substituents or the fluorine substituents
accelerate the chain transfer rate during polymerization. The
electron-withdrawing effect of the CF3 or fluorine substituent
makes the metal center more electropositive. It tends to catch
␤-H of growing chain or promote other chain transfer re-
actions. Ewen studied complexes Me2C(Cp)(Flu)ZrCl2 with
halogen substituents on fluorene. They think the substituent
1
according to H NMR spectra data. This structure tends to
be C2 symmetrical. According to the 13C NMR spectra of
polymer from 1 the two consecutive isotactic placements (an
[mm] stereodefect) remain constant, but isolated placement
(an [m] stereodefect) increases when compared with poly-
mer from 4. The isolated [m] stereoerrors can arise from site
epimerization (chain migration without insertion) [14]. We
Table 2
Pentad distributions for polypropylene from 1 and 4 at 30 ◦C
Run no.
Complex
rmmr (%)
mmrr (%)
rmrr (%)
rrrr (%)
rrrm (%)
mrrm (%)
1
11
1
4
2.0
1.6
3.9
3.5
8.9
3.0
74.1
85.1
6.4
3.4
4.7
3.4

150
J. Huang et al. / Journal of Molecular Catalysis A: Chemical 227 (2005) 147–152
tic block length. This may improve the elastomeric proper-
ties of the polymer. Average block length, as determined by
a numerical integration of the pentads, has a great effect on
the properties of the polymer. Relatively short average block
lengths, i.e. 6–15 tend to occur in a flexible and rubbery poly-
mer which exhibits good elastic properties as reported by Job
[13]. In addition the partial crystalline polypropylene with
low melting point and ꢀHf has good machining and trans-
parent properties.
3. Conclusions
In summary, the activity and stereoselectivity of complex
(RXPh)2C(Cp)(Flu)MCl2 (M = Zr, Hf) greatly depend on the
type of RX and the position of RX on the phenyl group. The
introduction of CF3 at the meta position on the phenyl group
can increase the activity in polymerization and decrease the
tacticity and crystallinity of the polymer obtained. The com-
plex with a halogen substituent at the para position showed
low activity and produced polymers with high melting point.
Fig. 2. 13C NMR (methyl region) of syndiotactic polypropylene synthesized
using 1/MAO at 30 ◦C.
think during polymerization when the polymer chain is at
the side of CF3 group bending toward cyclopentadienyl, the
chain may tend to migrate to the side where CF3 group bends
to fluorenyl. So the CF3 groups increase the [rmrr] and [rrrm]
pentads in polymer chain (Fig. 2).
The polypropylene from 1 has low tacticity ([r] = 91.6%)
and short average syndiotactic block length (Lsyn = 26). As
a result its melting point is low (120 ◦C) and ꢀHf is small
(24.92 J/g) compared to the polymer obtained from the com-
plex without substituent. Fig. 3 shows its DSC curve is broad.
So it is not highly crystalline syndiotactic polypropylene, but
partial crystalline polypropylene with low average syndiotac-
4. Experimental
All the operations were carried out under a dry argon
atmosphere using standard Schlenk techniques. Toluene,
diethyl ether, and petroleum ether were refluxed over
sodium/benzophenone ketyl, and distilled prior to use. The
cocatalyst 1.53 M methylaluminoxane (MAO) in toluene was
purchased from Witco.
Elemental analyses were carried out on an EA-1106 type
1
analyzer. H NMR were recorded on a Bruker AVANCE
500 MHz spectrometer with TMS as internal standard. MS
spectra were recorded on a HP 5989A instrument. Differ-
ential scanning calorimetry was performed on a Universal
V2.3C TA instrument at a heating rate of 10 ◦C/min. 13C
NMR spectra were recorded on a DR 500 Bruker spectrom-
eter operating at 125.78 MHz in o-dichlorodeuterobenzene.
4.1. Preparation of 1,1ꢀ-(2,4-cyclopentadien-
ylidenemethylene)bis-(3-trifluoromethyl-phenyl)
To a solution of sodium ethoxide prepared from
adding 0.41 g (18.0 mmol) sodium to 20 ml ethanol were
added 5.56 g (18.0 mmol) bis-(3-trifluoromethyl-phenyl)
methanone and 1.48 ml (18.0 mmol) freshly prepared cy-
clopentadiene. Under good stirring for 10 min the yielded
dark red solution was kept at 0 ◦C for 1.5 h. The product was
then collected on a filter, washed with several portion of al-
cohol, and dried, to give a red crystal 4.78 g (yield, 73.4%).
1H NMR (CDCl3, 500 MHz): δ = 6.20 (m, 2H, Cp), 6.66 (m,
2H, Cp), 7.47 (d, J = 7.80 Hz, 2H, Ph), 7.54 (t, J = 7.80 Hz,
2H, Ph), 7.58 (s, 2H, Ph), 7.69 (d, J = 7.80 Hz, 2H, Ph).
1,1ꢀ-(2,4-cyclopentadien-ylidenemethylene)bis-(4-chlor-
o-phenyl) and 1,1ꢀ-(2,4-cyclopentadien-ylidenemethylene)
Fig. 3. DSC Curves of polypropylene obtained from complexes 1, 3, 4 and
5.

J. Huang et al. / Journal of Molecular Catalysis A: Chemical 227 (2005) 147–152
151
bis-(4-fluoro-phenyl) were obtained by using a similar
procedure.
J = 7.16 Hz, Ph), 7.60 (t, 2H, J = 8.37 Hz, fluorenyl), 7.48
(d, 2H, J = 7.44 Hz, Ph), 7.38 (d, 2H, J = 7.16 Hz, Ph), 6.92
(t, 2H, J = 8.60 Hz, fluorenyl), 6.42 (d, 2H, J = 8.60 Hz,
fluorenyl), 6.40 (t, 2H, J = 2.61 Hz, Cp), 5.77 (t, 2H,
J = 2.61 Hz, Cp). LRMS (70 eV): m/z = 511 (100, M+ − Cl,
4.2. Preparation of complex 1
[(C13H8-␮-C(m-CF3-Ph)2-C5H4)ZrCl2]
+
FC CH), 430 (34, {C13H8-µ-C(p-F-Ph)2-C5H4} ), 426
The solution of 6.0 mmol fluorenyl lithium salt in
20 ml ether was added dropwise to a solution of 1.59 g
(6.0 mmol) 1,1ꢀ-(2,4-cyclopentadien-ylidenemethylene)bis-
(3-trifluoromethyl-phenyl) in 40 ml ether. After stirring for
about 2 h, the solution was hydrolyzed by 20 ml water. The
ligand as white solid 1.16 g was precipitated (yield, 45.3%).
To a solution of 1.16 g (2.2 mmol) ligand in 30 ml
ether, 2.2 ml (4.4 mmol) n-butyllithium (2.0 M solution in
n-hexane) was added dropwise at −78 ◦C. After stirring
overnight, 0.51 g (2.2 mmol) ZrCl4 was added and the so-
lution was stirred for 8 h at room temperature, and then evap-
orated to dryness. The residue was recrystallized by toluene
to give 0.90 g (yield, 49%) complex 1 as a red crystal.
(24, M+ − fluorenyl). HRMS: calcd. for C31H20Cl2 F2Zr:
589.9957; found: 589.9936.
4.6. Preparation of complex 5
[(C13H8-␮-C(p-Cl-Ph)2-C5H4)ZrCl2]·1.5 toluene
Complex 5 was synthesized by the procedure similar to
that used for 1.
1H NMR (CDCl3, 500 MHz): δ = 8.22 (d, 2H, J = 8.46 Hz,
fluorenyl), 7.85 (dd, 2H, J1 = 8.43 Hz, J2 = 2.41 Hz, Ph),
7.76 (dd, 2H, J1 = 8.50 Hz, J2 = 2.41 Hz, Ph), 7.60 (t, 2H,
J = 8.46 Hz, fluorenyl), 7.45 (dd, 2H, J1 = 8.43 Hz, J2 = 2.34,
Ph), 7.34 (dd, 2H, J1 = 8.50 Hz, J2 = 2.34, Ph), 7.07 (t, 2H,
J = 8.10 Hz, fluorenyl), 6.44 (d, 2H, J = 8.10 Hz, fluorenyl),
6.40 (t, 2H, J = 2.68, Cp), 5.76 (t, 2H, J = 2.68 Hz, Cp). LRMS
(70 eV): m/z = 622 (18, M+), 511 (20, M+ − p-Cl-Ph), 462
1H NMR (CDCl3, 500 MHz): δ = 8.24 (m, 2H, fluorenyl),
8.19 (m, 2H, Ph), 8.09 (m, 2H, Ph), 7.61–7.64 (m, 5H, Ph
and fluorenyl), 7.53 (t, 1H, J = 8.14 Hz, Ph), 7.06 (t, 2H,
J = 7.80 Hz, fluorenyl), 6.44 (m, 2H, fluorenyl), 6.28 (dd, 2H,
J1 = 11.01 Hz, J2 = 2.03 Hz, Cp), 5.77 (dd, 2H, J1 = 11.01 Hz,
J2 = 2.03 Hz, Cp). LRMS (70 eV): m/z = 690 (10, M+), 530
+
(100, {C13H8-µ-C(p-Cl-Ph)2-C5H4} ). HRMS: calcd. for
C31H20Cl4Zr: 621.9366; found: 621.9380.
+
(100, {C13H8-µ-C(m-CF3-Ph)2-C5H4} ). Anal. calcd. for
C33H20Cl2F6Zr·C7H8: C, 61.21, H, 3.60; found: C, 61.62,
4.7. Preparation of complex 6
[(C13H8-␮-C(p-Cl-Ph)2-C5H4)HfCl2]·1.5 toluene
H, 4.58.
4.3. Preparation of complex 2
[(C13H8-␮-C(m-CF3-Ph)2-C5H4)HfCl2]· toluene
Complex 6 was synthesized by the procedure similar to
that used for 1.
1H NMR (CDCl3, 500 MHz): δ = 8.19 (d, 2H, J = 8.35Hz,
fluorenyl), 7.86 (dd, 2H, J1 = 7.30 Hz, J2 = 2.39 Hz, Ph),
7.76 (dd, 2H, J1 = 7.35 Hz, J2 = 2.39 Hz, Ph), 7.58 (t,
2H, J = 8.35 Hz, fluorenyl), 7.44 (dd, 2H, J1 = 7.30 Hz,
J2 = 2.30 Hz, Ph), 7.34 (dd, 2H, J1 = 7.35 Hz, J2 = 2.30 Hz,
Ph), 7.05 (t, 2H, J = 8.82 Hz, fluorenyl), 6.48 (d, 2H,
J = 8.82 Hz, fluorenyl), 6.34 (t, 2H, J = 2.67 Hz, Cp), 5.71 (t,
2H, J = 2.67 Hz, Cp). LRMS (70 eV): m/z = 712 (100, M+),
601 (82, M+ − p-Cl-Ph), 462 (94, {C13H8-µ-C(p-Cl-Ph)2-
Complex 2 was synthesized by the procedure similar to
that used for 1.
1H NMR (CDCl3, 500 MHz): δ = 8.15–8.23 (m, 4H, Ph
and flurenyl), 8.09 (m, 2H, Ph), 7.57–7.66 (m, 5H, Ph
and flurenyl), 7.54 (t, 1H, J = 8.20 Hz, Ph), 7.04 (t, 2H,
J = 7.81 Hz, fluorenyl), 6.38 (m, 2H, fluorenyl), 6.23 (dd, 2H,
J1 = 10.05 Hz, J2 = 2.02 Hz, Cp), 5.73 (dd, 2H, J1 = 10.05 Hz,
J2 = 2.02 Hz, Cp). LRMS (70 eV): m/z = 778 (8, M+), 530
+
(100, {C13H8-µ-C(m-CF3-Ph)2-C5H4} ). Anal. calcd. for
+
C5H4} ). HRMS: calcd. for C31H20Cl4Hf: 711.9785; found:
C33H20Cl2F6Hf·C7H8: C, 55.09, H, 3.24; found: C, 54.81,
711.9725.
H, 3.36.
4.4. Preparation of complex 3
(C13H8-␮-CPh2-C5H4)ZrCl2
4.8. Polymerization procedure
A 100 ml flask was equipped with a propylene inlet, a mag-
neticstirrer, andavacuumline. Theflaskwasfilledwith50 ml
of freshly distilled toluene. MAO was added, and the flask
was placed in a bath at the desired polymerization tempera-
ture for 10 min. The polymerization reaction was started by
adding a solution of the catalyst precursor with a syringe. The
polymerization was carried out for 0.5 h and then quenched
with 3% HCl in ethanol (50 ml). The precipitated polymer
was filtered and then dried overnight in a vacuum oven at
80 ◦C.
Complex 3 was synthesized according to the literature [2].
4.5. Preparation of complex 4
(C13H8-␮-C(p-F-Ph)2-C5H4)ZrCl2
Complex 4 was synthesized by the procedure similar to
that used for 1.
1H NMR (CDCl3, 500 MHz): δ = 8.22 (d, 2H, J = 8.37 Hz,
fluorenyl), 7.88 (d, 2H, J = 7.44 Hz, Ph), 7.79 (d, 2H,

152
J. Huang et al. / Journal of Molecular Catalysis A: Chemical 227 (2005) 147–152
[6] W. Kaminsky, A. Hopf, C. Piel, J. Organomet. Chem. 684 (2003)
Acknowledgments
200.
[7] W. Kaminsky, A. Hopf, M. Arndt-Rosenau, Marcromol. Symp. 201
(2003) 301.
[8] G.H. Llinas, R.O. Day, M.D. Rausch, J.C.W. Chien, Organometallics
12 (1993) 1283.
[9] J.S. Yoon, Y.S. Lee, E.S. Park, I.M. Lee, D.K. Park, S.O. Jung,
Polym. Eur. J. 36 (2000) 1271.
[10] S. Lin, E. Hauptman, T.K. Lal, R.M. Waymouth, R.W. Quan, A.B.
Ernst, J. Mol. Catal. A: Chem. 136 (1998) 23.
We gratefully acknowledge the financial support from the
Special Funds for Major State Basic Research Projects (G
1999064801), the National Natural Science Foundation of
China (NNSFC) (20372022) and Research Fund for the Doc-
toral Program of Higher Education (RFDP) (20020251002).
[11] R. Schmidt, H.G. Alt, J. Organomet. Chem. 621 (2001) 304.
[12] G.Y. Lee, M. Xue, M.S. Kang, O.C. Kwon, J. Yoon, Y. Lee, H.S.
Kim, H. Lee, I. Lee, J. Organomet. Chem. 558 (1998) 11.
[13] U.S. 5270410 (1993); R.C. Job, Chem. Abstr. 114 (1991) 145225.
[14] R. Leino, F.J. Gomez, A.P. Cole, R.M. Waymouth, Macromolecules
34 (2001) 2072.
[15] P.C. Mohring, N. Coville, J. Organomet. Chem. 479 (1994) 1.
[16] A.R. Siedle, R.A. Newmark, B.F. Duerr, P.C. Leung, J. Mol. Catal.
A: Chem. 214 (2004) 187.
References
[1] J.A. Ewen, R.L. Jones, A. Razavi, J. Am. Chem. Soc. 110 (1988)
6255.
[2] A. Razavi, J.L. Atwood, J. Organomet. Chem. 459 (1993) 117.
[3] A. Razavi, J.L. Atwood, J. Organomet. Chem. 520 (1996) 115.
[4] A. Razavi, U. Thewalt, J. Organomet. Chem. 621 (2001)
267.
[5] H.G. Alt, R. Zenk, J. Organomet. Chem. 522 (1996) 39.
[17] E.P. 0577581 (1994); J.A. Ewen, Chem. Abstr. 112, 84218.