Syntheses of methylene-bridged ansa-zirconocene complexes and copolymerization studies of ethylene and norbornene

Article abstract of DOI:10.1016/j.jorganchem.2004.05.015

Methylene-bridged ansa-metallocene complexes bearing substituents on the cyclopentadienyl (Cp) and fluorenyl (Flu) moieties, namely methylene[9-(2,7-di-tert-butyl)fluorenyl (2-(1,3-dimethylcyclopentadienyl)]zirconium dichloride (1a) and its analogue, meth

Full text of DOI:10.1016/j.jorganchem.2004.05.015

Journal of Organometallic Chemistry 689 (2004) 2586–2592
www.elsevier.com/locate/jorganchem
Syntheses of methylene-bridged ansa-zirconocene complexes
and copolymerization studies of ethylene and norbornene
a
Si-Geun Lee , Sung-Don Hong , Young-Whan Park , Boong-Goon Jeong ,
a
a
a
a
a
a,
* b
Dae-Woo Nam , Hye Young Jung , Hyosun Lee *, Kwang Ho Song
a
LG Chemical Ltd./Research Park, Munji-dong, Yuseong-gu, Daejon-city 305-380, Republic of Korea
Department of Chemical and Biological Engineering, Korea University 1,5-ka, Anam-dong, Sungbuk-ku, Seoul 136-701, Republic of Korea
b
Received 2 March 2004; accepted 11 May 2004
Available online 2 July 2004
Abstract
Methylene-bridged ansa-metallocene complexes bearing substituents on the cyclopentadienyl (Cp) and fluorenyl (Flu) moieties,
namely methylene[9-(2,7-di-tert-butyl)fluorenyl(2-(1,3-dimethylcyclopentadienyl))]zirconium dichloride (1a) and its analogue, meth-
ylene[(9-(2,7-di-tert-butyl)fluorenyl(2-(1-methyl-3-phenyl)cyclopentadienyl))]zirconium dichloride (2a), have been prepared from
(2,7-di-tert-butyl)-9-prop-2-ynyl-9H-fluorene (2). This procedure includes the use of 3-bromo-1-propyne which affords the methy-
lene bridging unit by way of an intermolecular Pauson–Khand reaction in which norbornadiene and a pendant alkyne cyclize to
form a ring that later becomes a substituted cyclopentadienyl group. Ethylene–norbornene (E–N) copolymerization was then carried
out using these new complexes (1a and 1b) in the presence of methylaluminoxane (MAO) as a cocatalyst; these activities can be
compared to that of isopropylene[9-fluorenyl-cyclopentadienyl]zirconium dichloride (3a). The activity of catalyst 1a was comparable
to that of 3a but much higher than that of 2a. In addition, 1a shows higher norbornene insertion performance, and gives an E–N
copolymer with a higher glass transition temperature (Tg) than 2a under identical conditions; both 1a and 2a give a lower Tg poly-
mer than 3a does.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: ansa-Zirconocene; Ethylene–norbornene copolymerization; Glass transition temperature (Tg); MAO
1. Introduction
ene copolymerization by rationally designed ansa-metal-
locenes has been demonstrated for substrates including
a-olefins, propene, hexene and various cycloolefins [6].
In particular, ethylene–norbornene (E–N) copolymers
constitute a major commercial family of cyclic olefin
copolymers (COCs), possessing applied mechanical and
optical properties [7]. The novel properties of E–N co-
polymers may be used in place of polycarbonate (PC), ac-
ronitrile–butadiene–styrene (ABS) and glass substrates.
E–N copolymers have also been of particular interest dur-
ing last decade since they have been produced by metallo-
cene catalysts [8]. Thus, the design of new ligands in
metallocene catalysis has led to polymerization activity
control studies, the acceptance of two different comono-
mers, and the stereoregularity of COCs to modulate the
Since the discovery of metallocene/methylaluminox-
ane (MAO) olefin polymerization catalysis by Kaminsky
and Sinn [1], tremendous efforts have been made to
search for novel transition metal catalysts through the
use of appropriate ligand systems [2,3]. In general, the
metallocene ligand geometry and central metal electron-
ics allow for control of: (i) catalytic activity, (ii) olefin
monomer and/or comonomer response, (iii) tacticity
and (iv) polymer molecular weight [4,5]. To date, ethyl-
*
Corresponding author. Tel.: +82-42-866-2758; fax: +82-42-861-
3647.
E-mail address: hyobone@lgchem.com (H. Lee).
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.05.015

S.-G. Lee et al. / Journal of Organometallic Chemistry 689 (2004) 2586–2592
2587
polymerÕs physical properties [9,10]. Recently, Lee et al.
have reported the methylene-bridged ansa-zirconocene
complex, [H2C(Me2C5H2)2]ZrCl2, bearing methyls adja-
cent to the bridge-head carbon. This derivative possesses
exceptional E–N copolymerization activity [11] and the
electronic effect can be tuned through substitution, and
steric hindrance can be minimized to readily accept bulky
substrates such as norbornene. Since the modification of
ligands were limited to only Cp and four methyls on the
carbons adjacent to the bridge-head carbon groups in
the complex [H2C(Me2C5H2)2]ZrCl2, we are interested
in expanding our scope toward designing heavier ligands,
such as those involving indenyl or fluorenyl groups. Spe-
cifically, in the ansa-metallocene complexes bearing a Flu
group, the bulkier substituents at the 2- and 7-position
have shown to allow for higher olefin polymerization ac-
tivity and higher molecular weight polymers, [12] which is
less common and more challenging.
In this work, we report the syntheses of two novel
methylene-bridged zirconocenes, methylene[9-(2,7-di-
tert-butyl)fluorenyl(2-(1,3-dimethylcyclopentadienyl))]
zirconium dichloride (1a) and methylene[(9-(2,7-di-tert-
butyl)fluorenyl(2-(1-methyl-3-phenyl)cyclopentadienyl))]
zirconium dichloride (2a). Their catalytic reactivity to-
ward ethylene–norbornene copolymerization is also
compared to the parent zirconocene 3a [13].
trated in Scheme 1. While an ansa bridge carbon unit is
commonly synthetically incorporated via a fulvene unit,
here the methylene-bridge unit was brought about by an
intermolecular Pauson–Khand reaction at the triple
bond of substrate 2, which later affords the accompany-
ing substituted cyclopentadiene group.
Deprotonation of 2,7-di-tert-butylfluorene (1) with n-
BuLi gave the corresponding mono-anion compound
which when treated with propargyl bromide gave 2 pos-
sessing a pendant alkyne group, in high yield (95%). The
tricyclic compound 3 was then generated by an intermo-
lecular Pauson–Khand reaction with norbornadiene re-
quiring a catalytic amount of Co2(CO)8 [14]. Addition
of Me2CuLi to compound 4 produced the 1,4-addition
product 5. Interestingly, the addition of Me2CuLi to
the unsubstituted analog (3), did not give the 1,4-addi-
tion product. It is believed that compound 3 has poor
solubility at À10 ꢁC in diethyl ether and thus does not
undergo reaction with the cuprate reagent [15], whereas;
the presence of the tert-butyl groups in 4 improves its
solubility, giving 5 in high yield (91%).
The retro-Diels–Alder reaction of 5 was performed at
300 ꢁC to give compound 6. This condition is milder
than that for the retro-Diels–Alder synthesis of
[H2C(Me2C5H2)2]ZrCl2 (420 ꢁC), starting from 1,4-pen-
tadiyne [11]. The 1,2-addition of MeLi and PhLi fol-
lowed by dehydration during aqueous HCl workup,
gave the desired cyclopentadiene compound 7 and 8, re-
spectively, in good yield.
2. Results and discussion
The deprotonation of 7 and 8 with n-BuLi gave the
corresponding dianions which were then treated with
ZrCl4 in hexane to cleanly afford the ansa-zirconocene
complexes 1a and 2a as light red and bright red solids,
respectively. The H NMR spectrum of 2a indicated a
molecular symmetry change from CS in complex 1a to
2.1. Preparation and characterization of complexes 1a
and 2a
1
The new metallocene complexes for E–N copolymer-
ization were synthesized according to the reactions illus-
O
Br
R
R
R
R
R
R
iii
i
ii
R = t-Bu (1)
R = t-Bu (2)
R = H (3)
R = t-Bu (4)
R'
O
R'
O
Cl
Zr
Me
R
R
Cl
R
R
v
R
R
iv
vi
R
R
R = t-Bu (5)
R = t-Bu, R' = Me (7)
R = t-Bu, R' = Ph (8)
R = t-Bu (6)
R = t-Bu, R' = Me [1a]
R = t-Bu, R' = Ph [2a]
Scheme 1. Synthesis of complexes 1a and 2a. (i) n-BuLi; (ii) CO/CO2(CO)8; (iii) Me2CuL; (iv) 300 ꢁC; (v) MeLi or PhLi, then aq. HCl; (vi) n-BuLi
and ZrCl4.

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S.-G. Lee et al. / Journal of Organometallic Chemistry 689 (2004) 2586–2592
C1 with the inclusion of a Cp ring phenyl substituent.
Two doublets are present in the spectrum at d 6.38
and 6.33 (3JH-H =4 Hz) in 2a, compared to the singlet
at d 6.21 in 1a assigned to the Cp-ring hydrogens. Also,
two doublets at d 5.36 and 5.08 (2JH-H =15 Hz) are pres-
ent in 2a, compared to a singlet at d 4.89 for 1a, assigned
to the ansa-bridge hydrogens. Lastly two singlets at d
1.37 and 0.90 are present for 2a, compared to the singlet
at d 1.35 in 1a assigned to the tert-butyl substituent on
the Flu group.
25
20
15
10
5
catalyst 1a (P/A)
catalyst 1a (notP/A)
catalyst 2a
catalyst 3a
0
0
30
60
90
Pressure(psi)
2.2. Copolymerization of ethylene and norbornene with 1a
and 2a and MAO
Fig. 1. Catalyst activity for the E–N copolymerization at different
ethylene pressures (70 ꢁC).
Catalysts 1a and 2a were used in combination with
methylaluminoxane (MAO) for ethylene–norbornene
copolymerization [16] and compared to isopropylene[9-
fluorenylcyclopentadienyl]zirconium dichloride [3a]
activity under identical conditions [17]. The results of
E–N copolymerization are summarized in Table 1.
A comparative reactivity of each catalyst is presented
in Fig. 1, depending on ethylene pressure. The activity
of catalysts increased as the ethylene pressure increases
from 30 to 100 psi for all catalysts (1a–3a) [18]. The ac-
tivity of catalyst 2a was very poor compared to its deriv-
ative catalyst 1a. The replacement of the a-methyl
substituent with a phenyl group on the Cp ring in com-
pound 2a seems to give tremendous hindrance to intro-
ducing an olefin monomer into the active zirconium
center although electronic stabilization of active cat-
ion–anion complex by phenyl group is expected during
polymerization. Moreover the preactivation of catalyst
2a for copolymerization did not increase the activity.
It is probable that the phenyl group causes the inhibition
of the activation of catalyst by MAO.
It is noted that all catalysts show much higher in-
creasing activities as increasing ethylene pressure,
whether the catalyst was preactivated or not. Specifically,
when the copolymerization was carried out after adding
active species by MAO preactivation of catalyst 1a,
resulted in nearly twice as high an activity as that with-
out preactivation (Table 1, entries 1–6). E–N copoly-
merization activity of catalyst 3a, however, was not
affected by the preactivation of the catalyst at all. Thus,
somehow longer time is needed for catalyst 1a to
become an activated cation–anion complex to initiate
polymerization, compared to catalyst 3a. Apparently,
the steric hindrance imparted by the Cp and Flu ring
substituents affects the accessibility of the approaching
cocatalyst MAO; thus it is believed that the preactiva-
tion of catalyst before starting copolymerization is what
resulted in the different activities.
The glass transition temperatures (Tgs) of the result-
ing copolymers as a function of ethylene pressure are
presented for each catalyst in Fig. 2. The copolymer
Table 1
Ethylene–norbornene copolymerizationa results
Entry
Catalyst
Pressure (psi)
Time (min)
Yield (g)b
Activityc
Tg (ꢁC)
Mw
Mw/Mn
1
2
1a
1a
1a
1a
1a
1a
1a
1a
2a
2a
2a
3a
3a
3a
30
60
20
20
20
20
20
20
40
60
20
20
20
20
20
20
5.5
15.0
25.0
2.5
8.33
22.73
37.88
3.78
11.67
25.6
12.1
12.5
0.15
1.52
2.27
13.5
25
185
171
158
186
164
145
157
170
–
138,000
124,000
98,000
139,000
117,000
84,000
116,000
114,000
–
1.8
1.8
1.5
2.1
1.6
1.8
2.0
2.0
–
3
100
30
4d
5d
6d
7d
8d
9
60
7.7
100
60
16.9
16
60
30
25
0.1
1.0
10
11
12
13
14
60
142
122
204
189
188
249,000
270,000
312,000
224,000
256
1.9
2.1
2.3
2.1
1.9
100
30
1.5
8.9
60
100
16.5
22.7
34.4
a
Polymerization conditions: zirconocene 2 lmol, Al/Zr=2000, toluene 150 mL (56 wt% norbornene), Tp =70 ꢁC.
Yield is defined as the weight of copolymer obtained.
Activity in 103 kg COC/mol of Zr h.
Preactivation of catalyst with MAO was not conducted.
b
c
d

S.-G. Lee et al. / Journal of Organometallic Chemistry 689 (2004) 2586–2592
2589
methyl substitutents showed higher copolymerization
activity than for precatalyst 3a. However, owing primar-
ily to substituents effects in norbornene, monomer ac-
ceptance is believed to decrease in the order
2a<1a<3a, judging from the Tg of the resulting poly-
mers. In addition, it was found that the preactivation
of catalysts beforehand was crucial to maximize the cat-
alytic activity for E–N copolymerization, depending on
electronics and sterics imparted to the central metal by
the ansa-metallocene ligand.
200
180
160
140
120
catalyst 1a (P/A)
catalyst 1a (not P/A)
catalyst 2a
catalyst 3a
0
30
60
90
pressure(psi)
4. Experimental
Fig. 2. Glass transition temperature (Tg) of E–N copolymers produced
at different ethylene pressure (70 ꢁC).
4.1. General techniques and reagents
All manipulations were performed under an inert at-
mosphere using a combination of glove box, high vac-
uum, and Schlenk techniques. All solvents were
purchased from Aldrich and purified by distillation
over Na/K alloys with benzophenone ketyl. All avail-
able reagents, including fluorene and 2,7-di-tert-butyl-
fluorene, were purchased commercially and used as
received unless otherwise noted in the experimental
procedure. Compound 3a which can be prepared by
a literature method [13] was purchased here for poly-
merization testing from the Boulder Scientific Com-
pany. The cocatalyst, 10 wt% methylaluminoxane
(MAO) in toluene, purchased from Akzo. The como-
nomer, norbornene (bicyclo[2,2,1]hept-2-ene), was ob-
tained from Aldrich with a purity of 99% and was
further purified prior to use. Ethylene (99.9%) was pu-
rified in columns containing molecular sieves, CuO,
Tg appears to have a linear dependence on the mole ra-
tio of the fed norbornene over ethylene in the copoly-
merization media. These data suggest that as the
ethylene pressure in reaction media increases and the
norbornene content in the copolymer decreases, Tg of
the resulting copolymer decreases [19]. For 1a, the Tg
of copolymer obtained at the same reaction conditions
was lower by 18–36 ꢁC than that for 3a. The Tg of co-
polymer by the catalyst 2a shows a significantly lower
Tg by 15–30 ꢁC than that for complex 1a. It is possible
that catalyst 3a has a higher ability for norbornene in-
corporation, on steric grounds, owing to the absence
of ring substituents. It follows that complex 2a, possess-
ing a Cp-phenyl substituent shows a much larger steric
influence on the incoming bulky norbornene; thus, the
final percentage of polymeric norbornene would be
low. Also, the molecular weight of copolymers (Mw)
for the each catalyst decreases with increasing ethylene
pressure. This suggests that the higher ethylene concen-
tration provides more of a chance for chain transfer by
b-hydride elimination compared to the propagation re-
action [20]. In the E–N copolymer, only bound ethylene
undergoes b-hydride elimination to be chain transferred
(or by extra MAO) which dictates the Mw value. If prop-
agation is fast or dominates over chain transfer then a
higher Mw polymer is obtained. Interestingly, the molec-
ular weight of copolymers by catalyst 1a was much
lower than those for catalyst 2a and 3a, indicating that
Cp-methyl substitution may facilitate chain transfer bet-
ter than Flu-tert-butyl substitution.
1
and Al2O3. H and 13C NMR spectra were obtained
on a Bruker ARX-300 spectrometer. 1H and 13C
NMR chemical shifts are reported in ppm, relative to
SiMe4 (d=0) and referenced internally relative to the
protio solvent impurity (d=7.26 and d=77.0, respec-
tively for CDCl3). All coupling constants are reported
in hertz. Elemental analyses were carried out on a Per-
kin–Elmer 2400 CHN microanalyzer. IR spectra were
obtained on a Bio-Rad FTA-60A instrument. Values
for the glass transition temperature (Tg) were measured
using a TA instrument DSC2010. The sample was first
heated to 300 ꢁC, then cooled to 30 ꢁC (20 ꢁC/min),
and then reheated to 250 ꢁC or 300 ꢁC (20 ꢁC/min).
The data used in this work was taken from the second
heating. The average molecular weight (Mw) and the
molecular weight distribution (MWD) of E–N copoly-
mers were measured by gel permeation chromatogra-
phy (GPC), waters 150 CV equipped with three
Waters chromatographic columns. Chloroform solvent
was used with a flow rate 1 mL/min at 25 ꢁC. Polysty-
rene (PS) standards with a narrow molecular weight
distribution were used for the calibration of molecular
weights versus retention time of the column set.
3. Conclusion
In summary, we have synthesized two new ansa-zirc-
onocene dichlorides with substituents a- to the ansa-
bridge to investigate their E–N copolymerization in
the presence of excess MAO. The precatalyst 1a bearing

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S.-G. Lee et al. / Journal of Organometallic Chemistry 689 (2004) 2586–2592
4.2. 2,7-Di-tert-butyl-9-prop-2-ynyl-9H-fluorene (1)
2.27 (s, 1H), 2.12 (d, 1H, J=5 Hz), 1.39 (s, 9H, t-Bu),
1.36 (s, 9H, t-Bu), 0.96 (d, 1H, J=9 Hz), 0.25 (d, 1H,
J=9 Hz). Anal. Calc. for C32H36O: C, 88.03; H, 8.31.
Found: C, 88.37; H, 8.41%.
To a Schlenk flask containing 2,7-di-tert-butylfluo-
rene (1) (21.2 g, 76.13 mmol) in THF (90.0 mL) n-BuLi
(2.5 M in hexane solution, 36.54 mL, 91.36 mmol) was
slowly added at À78 ꢁC. The solution was warmed to
room temperature and stirred for 4 h, before being
cooled again to À78 ꢁC. Propargyl bromide (8.48 ml,
76.13 mmol, 80% in toluene solution) was added drop-
wise to the solution. The resulting solution was allowed
to warm to room temperature and stirred at room tem-
perature for 5 h before it was poured into cold water
(200 mL). Diethylether (300 mL) was then added and
the mixture was poured into a separatory funnel. The
aqueous layer was removed and the organic portions
were combined and dried over anhydrous MgSO4. After
removal of the solvent by rotary evaporation, the residue
was purified by silica gel column chromatography using
hexane and ethyl acetate as the eluents (20:1 v/v), giving
23 g of product 2 (95%). 1H NMR (CDCl3): d 7.78 (s, 2H,
Ph), 7.64 (d, 2H, Ph, J=8 Hz), 7.42 (d, 2H, Ph, J=8 Hz),
4.02 (t, 1H, J=7 Hz), 2.68 (dod, 2H, CH2, J=7, 3 Hz),
2.17 (s, 1H, CH) 1.40 (s, 18H, t-Bu). 13C NMR (CDCl3):
d 149.8, 146.1, 138.1, 124.5, 121.6, 119.0, 83.4, 69.5,
45.8, 34.9, 31.6, 23.7. Anal. Calc. for C24H28: C, 91.08;
H, 8.92. Found: C, 91.14; H, 8.86%.
4.5. 2-(2,7-Di-tert-butyl-9H-fluoren-9-ylmethyl)-3-meth-
yl-2,3,3a,4,7,7a-hexahydro-4,7-methano-inden-1-one (5)
To a Schlenk flask containing a slurry of CuI (11.4 g,
60 mmol) in Et2O (150 mL), a portion of MeLi (1.4 M in
Et2O solution, 85.7 mL, 90 mmol) was added at À20 ꢁC.
The solution was stirred at À20 ꢁC for 30 min and cooled
to À78 ꢁC. The solid compound 4 (9.5 g, 21.8 mmol) was
added to the solution in one portion. The resulting solu-
tion was allowed to warm to room temperature. The so-
lution was stirred at room temperature for 12 h and was
then poured into a large volume of cold water (200 mL).
The mixture was filtered over celite and the organic layer
was separated. The aqueous solution was re-extracted
with Et2O (50 mL). The organic solutions were then com-
bined, dried over anhydrous MgSO4, filtered and dried in
vacuo. Purification of the crude product was performed
with silica gel column chromatography with hexane
and ethyl acetate as eluents (10:1 v/v) to give 9.0 g of pure
1
white solid (91%). H NMR (CDCl3): d 7.65–7.55 (m,
4H, Ph), 7.45–7.35 (m, 2H, Ph), 6.10–6.20 (m, 2H),
4.21 (t, 1H, J=6 Hz), 3.15 (s, 1H), 2.66 (s, 1H), 2.65–
2.55 (m, 1H), 2.26 (d, 1H, J=9 Hz), 2.12–2.03 (m, 1H),
1.85–1.65 (m, 2H), 1.41 (s, 18H, t-Bu), 1.35–1.20 (m,
2H), 1.06 (d, 1H, J=9 Hz), 0.92 (d, 3H, CH3, J=6
Hz). 13C NMR (CDCl3): 217.3 (carbonyl), 149.5, 149.4,
147.3, 146.9, 138.4, 138.2, 137.3, 124.1, 123.9, 122.1,
121.8, 118.9, 118.8, 57.9, 53.9, 48.5, 46.4, 45.8, 44.8,
44.2, 41.4, 34.8, 31.6, 26.9, 20.5. Anal. Calc. for
C33H40O: C, 87.56; H, 8.91. Found: C, 87.67; H,
8.63%. IR (cmÀ1): 3058, 2959, 1733(CO), 1490, 1483,
1380, 1325, 1260, 797, 710, 619.
4.3. 2-(9H-Fluoren-9-ylmethyl)-3a,4,7,7a-tetrahydro-
4,7-methano-inden-1-one (3)
Compound 3 was synthesized from 9-prop-2-ynyl-
9H-fluorene according to a literature preparation [c].
The crude product was purified by silica gel column
chromatography with hexane and ethyl acetate as the el-
uents (10:1 v/v). After rotatory evaporation, the yield
1
was 73%. H NMR (CDCl3): d 7.75–7.60 (m, 2H, Ph),
7.40–7.50 (m, 2H, Ph), 7.40–7.15 (m, 4H, Ph), 7.32 (d,
1H, Ph, J=8 Hz), 6.45–6.38 (m, 1H), 6.15–5.95 (m,
2H), 4.21 (t, 1H, J=5 Hz), 3.00–2.80 (m, 2H), 2.68 (s,
1H), 2.41 (s, 1H), 2.26 (s, 1H), 2.07 (d, 1H, J=5 Hz),
1.01 (d, 1H, J=9 Hz), 0.39 (d, 1H, J=9 Hz).
4.6. 2-(2,7-Di-tert-butyl-9H-fluoren-9-ylmethyl)-3-meth-
yl-cyclopent-2-enone (6)
A sample of compound 5 (3.5 g, 7.7 mmol) was
placed in a quartz tube that was connected via a flexible
tube to a Schlenk flask. After the system was purged
with nitrogen, the quartz tube was placed in a furnace
whose temperature had been set at 300 ꢁC and the
Schlenk flask was immersed in a liquid nitrogen bath.
After 10 min, the quartz tube was removed from the fur-
nace and was allowed to cool to room temperature. Pu-
rification of the crude product was carried out by silica
gel column chromatography, eluting with hexane and
ethyl acetate (4:1 v/v) to give 1.8 g of product (60%).
1H NMR (CDCl3): d 7.63 (d, 2H, Ph, J=8 Hz), 7.41–
7.35 (m, 4H, Ph), 4.22 (t, 1H, J=8 Hz), 2.5–2.6 (m,
4H), 2.63 (d, 2H, J=8 Hz), 1.68 (s, 3H, CH3), 1.36 (s,
18H, t-Bu). 13C NMR (CDCl3): d 209.5 (carbonyl),
4.4. 2-(2,7-Di-tert-butyl-9H-fluoren-9-ylmethyl)-3a,4,7,
7a-tetrahydro-4,7-methano-inden-1-one (4)
Compound 4 was synthesized from 9-propynyl-(2,7-
di-tert-butyl)fluorene (2) according to a literature proce-
dure [c]. The crude product was purified by silica gel
column chromatography with hexane and ethyl acetate
as the eluents (10:1 v/v). After rotatory evaporation,
1
the yield was 78%. H NMR (CDCl3): d 7.61 (d, 1H,
Ph, J=8 Hz), 7.56 (d, 1H, Ph, J=8 Hz), 7.55 (s, 1H,
Ph), 7.53 (s, 1H, Ph), 7.40 (d, 1H, Ph, J=8 Hz), 7.32
(d, 1H, Ph, J=8 Hz), 6.45–6.38 (m, 1H), 6.15–6.03 (m,
2H), 4.16 (t, 1H, J=6 Hz), 3.06 (dd, 1H, J=15, 6 Hz),
2.89 (dd, 1H, J=15, 5 Hz), 2.68 (s, 1H), 2.44 (s, 1H),

S.-G. Lee et al. / Journal of Organometallic Chemistry 689 (2004) 2586–2592
2591
172.2, 149.6, 147.2, 138.9, 138.1, 124.0, 121.6, 119.0,
44.9, 34.8, 34.5, 31.9, 31.6, 28.8, 17.5. Anal. Calc. for
C28H34O: C, 87.00; H, 8.87. Found: C, 87.08; H,
9.06%. IR (cmÀ1): 2957, 1695 (CO), 1647, 1476, 1398,
1375, 1258, 1171, 911, 820, 731, 621.
mL, 4.58 mmol) was added in a dropwise fashion. After
the solution was stirred at room temperature for 12
hours, the solvent was removed in vacuo and the residue
was washed with pentane (2·30 mL) and dried. The dil-
ithium salt solution was added to ZrCl4 (0.485 g, 2.08
mmol) in n-hexane (30 mL) and the mixture was stirred
for 12 h. The solvent was decanted and the product was
extracted with cyclohexane (ca. 40 mL) to give 0.6 g of
4.7. 2,7-Di-tert-butyl-9-(2,5-dimethyl-cyclopentadienyl-
methyl)-9H- fluorene (7)
1
pure product (1a) (47%). H NMR (CDCl3): d 7.88 (d,
To a Schlenk flask containing complex 6 (5 g, 12.9
mmol) in Et2O (50 mL) was added MeLi (1.5 M in
Et2O, 13.86 mL, 19.4 mmol) at À78 ꢁC. The solution
was allowed to warm to room temperature. After the so-
lutionwas stirredfor20h, water(20mL)wasslowlyadded.
The reaction solvent was removed by way of rotary evap-
oration. Ethyl acetate (150 mL) was then added to the res-
idue and the mixture was poured into a separatory funnel.
The aqueous layer was removed and a 2 N HCl solution
(150 mL) was added. The contents of the separatory fun-
nel were vigorously shaken for 2 min, the aqueous layer
was removed, and the organic layer was washed with con-
centrated NaHCO3 (30 mL). The organic layer was col-
lected and dried over anhydrous MgSO4. After removal
of the solvent by rotary evaporation, the residue was pu-
rified by silica gel column chromatography, eluting with
2H, Ph, J=8 Hz), 7.59 (d, 2H, Ph, J=8 Hz) 7.55 (s,
2H, Ph), 6.21 (s, 2H), 4.89 (s, 2H, CH2), 2.21 (s, 6H,
CH3), 1.35 (s, 18H, t-Bu). 13C NMR (CDCl3): d 125.4,
124.3, 124.1, 122.1, 121.8, 120.6, 118.7, 107.3, 95.7,
69.6, 34.8, 30.9, 21.0, 17.5. Anal. Calc. for C29H34ZrCl2:
C, 63.95; H, 6.29. Found: C, 64.41; H, 6.77%.
4.10. Methylene[(9-(2,7-di-tert-butyl)fluorenyl)(2-(1-me-
thyl)(3-phenyl)cyclopentadienyl)]zirconium dichloride
(2a)
The general procedure for preparing 2a is the same as
preparing complex 1a in Section 4.9, with a correspond-
1
ing yield of 68%. H NMR (CDCl3): d 7.86 (d, 2H, Flu,
J=9 Hz), 7.6–7.55 (m, 4H, Flu 2H and Ph 2H), 7.43 (d,
2H, Flu, J=9 Hz), 7.40–7.28 (m, 2H, Ph), 6.49 (s, 1H,
Ph), 6.38 (d, 1H, Cp, J=4 Hz), 6.33 (d, 1H, Cp, J=4
Hz), 5.36 (d, 1H, CH2, J=15 Hz), 5.08 (d, 1H, CH2,
J=15 Hz), 2.32 (s, 3H, CH3), 1.37 (s, 9H, t-Bu), 0.9 (s,
9H, t-Bu). 13C NMR (CDCl3): d 150.1, 136.4, 129.5,
128.5, 127.9, 127.5, 125.7, 125.4, 124.9, 124.8, 124.7,
124.4, 124.0, 123.6, 122.2, 121.0, 120.8, 120.7, 119.1,
118.6, 93.7, 71.4, 35.3, 31.6, 30.9, 30.0, 22.1, 17.9. Anal.
Calc. for C34H36ZrCl2: C, 67.30; H, 5.98. Found: C,
67.71; H, 6.18%.
1
hexane to give 7 (3.57 g, 72%). H NMR (CDCl3): d
7.71 (d, 2H, Ph, J=8 Hz), 7.45 (d, 2H, Ph, J=8 Hz),
7.40 (s, 2H, Ph), 6.05 (s, 1H), 4.08 (t, 1H, J=9 Hz),
3.05–2.95 (m, 2H), 2.76 (d, 2H, J=9 Hz), 2.01 (s, 3H,
CH3), 1.91 (s, 3H, CH3), 1.44 (s, 18 H, t-Bu). 13C NMR
(CDCl3): d 149.3, 147.3, 144.0, 139.2, 138.7, 138.1,
124.0, 121.6, 118.9, 46.7, 44.0, 34.8, 34.5, 31.6, 30.8,
14.8, 14.2. Anal. Calc. for C29H36: C, 90.57; H, 9.43.
Found: C, 90.86; H, 9.14%. IR (cmÀ1): 2957, 1695 (CO),
1647, 1476, 1398, 1375, 1258, 1171, 911, 820, 731, 621.
4.11. General procedure for the copolymerization of
ethylene–norbornene
4.8. 2,7-Di-tert-butyl-9-(2-methyl-5-phenyl-cyclopenta-
dienylmethyl)-9H-fluorene (8)
Ethylene–norbornene copolymerization was carried
out using a 500 mL jacketed stainless steel reactor,
equipped with a mechanical stirrer. All manipulations
were carried out in an inert atmosphere using a standard
Schlenk technique or a VAC drybox. The norbornene
was dissolved in toluene to obtain 150 mL of a 56%
(by weight) solution. The solution was passed through
the purification column and injected into the reactor.
After the reactor temperature was stabilized, the
MAO-toluene solution (Al/Zr=2000, 2.0 mL, 2.0 mmol,
8.2 wt% in toluene) was injected into the reactor and the
reaction mixture was stirred for 15 min. The catalyst
(2·10À6 mol/L) was added to the reactor and ethylene
was fed at a constant pressure. The polymerization time
was measured from the moment reaction mixture stir-
ring started. After polymerization occurred, the reactor
was vented and the reaction mixture was poured into 2 L
of acetone. The precipitated white polymer was filtered,
The general procedure in Section 4.7 for preparing 7
was followed in preparing compound 8 here. Product 8
was obtained purely by way of silica gel column chroma-
tography, eluting with hexane to give 3.72 g of product
1
(68%). H NMR (CDCl3): d 7.64 (d, 2H, Ph, J=8 Hz),
7.37 (d, 2H, Ph, J=8 Hz), 7.32 (s, 2H, Ph), 7.25–7.15
(m, 5H, Ph), 6.21 (s, 1H), 4.15 (t, 1H, J=8 Hz), 3.45–
3.35 (m, 2H), 2.94 (d, 2H, J=8 Hz), 1.97 (s, 3H, CH3),
1.3 (s, 18H, t-Bu). 13C NMR (CDCl3): d 149.4, 147.1,
145.0, 142.1, 141.2, 138.1, 128.2, 127.8, 127.5, 126.6,
126.0, 124.0, 121.6, 118.9, 46.1, 43.0, 34.8, 31.5, 15.1.
4.9. Methylene[(9-(2,7-di-tert-butyl)fluorenyl-2-(1,3-di-
methyl)cyclopentadienyl)] zirconium dichloride (1a)
To a stirred solution of 7 (0.8 g, 2.08 mmol) in cold
THF (15 mL, À30 ꢁC), n-BuLi (2.5 M in hexane, 1.83

2592
S.-G. Lee et al. / Journal of Organometallic Chemistry 689 (2004) 2586–2592
(e) H. Cherdron, M.-J. Brekner, F. Osan, Angew. Makromol.
Chem. 223 (1994) 121.
washed with acetone and dried in a vacuum oven at 80
ꢁC. In case of preactivation of catalyst, half of the
MAO-toluene (Al/Zr=1000, 1.0 mL, 1.0 mmol, 8.2
wt% in toluene) solution was used as a scavenger in
the polymerization reactor, and the other MAO toluene
solution (Al/Zr=1000, 1.0 mL, 1.0 mmol, 8.2 wt% in tol-
uene) was added to the catalyst toluene solution and
stirred at room temperature for 15 min. After the addi-
tion of preactivated catalyst (2·10À6 mol/L), polymeri-
zation was allowed to start by supplying a constant
ethylene pressure to the reactor.
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analysis, DSC and GPC data collection. Dr. David G.
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