Ethylene polymerization activity under practical conditions displayed by zirconium complexes having two phenoxy-imine chelate ligands

Article abstract of DOI:10.1016/S1381-1169(01)00050-4

Ethylene polymerization using zirconium complexes having two phenoxy-imine chelate ligands was investigated at 50 and 75°C at 0.9 MPa ethylene pressure. The activity of the proto-catalyst, N-[(3-t-butylsalicylidene)anilinato]zirconium(IV)-dichloride (1), decreased by increasing the polymerization temperature (50°C: 1192kg-PE/mmol-Zr·h, 75°C: 209kg-PE/mmol-Zr·h). The introduction of an electron donating group, such as an n-hexyl and a methoxy group, on the imine nitrogen or at the para-position of phenoxy oxygen in a benzene ring suppressed the activity decrease, however, the activity at 75°C was still lower than that at 50°C. The combination of an n-hexyl or a cyclohexyl group on the imine nitrogen and a methoxy group at the para-position of the phenoxy oxygen enhanced activity at 75°C. Thus, N-[(3-t-butyl-5-methoxysalicylidene)-n-hexylaminato]zirconium(IV)dichloride (5) and N-[(3-t-butyl-5-methoxysalicylidene)cyclohexylaminato]zirconium(IV)dichloride (6) displayed activities of greater than 1000 kg-PE/mmol-Zrh. Moreover, the introduction of an adamantyl or a cumyl group at the position adjacent to the phenoxy oxygen further increased the activity. N-[(3-Adamantyl-5-methoxysalicylidene)cyclohexylaminato]zirconium(IV) dichloride (7), N-[(3-cumyl-5-methoxysalicylidene)-n-hexylaminato]zirconium(IV)dichloride (8), and N-[(3-cumyl-5-methoxysalicylidene)cyclohexylaminato]zirconium(IV)dichloride (9) displayed exceptionally high activity (7: 3052kg-PE/mmol-Zr·h, 8: 7078 kg-PE/mmol-Zr·h, 9: 7224kg-PE/mmol-Zr·h).

Full text of DOI:10.1016/S1381-1169(01)00050-4

Journal of Molecular Catalysis A: Chemical 169 (2001) 99–104
Ethylene polymerization activity under practical conditions
displayed by zirconium complexes having two
phenoxy-imine chelate ligands
Naoto Matsukawa, Shigekazu Matsui, Makoto Mitani, Junji Saito,
Kazutaka Tsuru, Norio Kashiwa, Terunori Fujita∗
R & D Center, Mitsui Chemicals, Inc., 580-32 Nagaura, Sodegaura, Chiba, Japan
Received 25 November 2000; accepted 6 January 2001
Abstract
Ethylene polymerization using zirconium complexes having two phenoxy-imine chelate ligands was investigated at 50
and 75◦C at 0.9 MPa ethylene pressure. The activity of the proto-catalyst, N-[(3-t-butylsalicylidene)anilinato]zirconium(IV)-
dichloride (1), decreased by increasing the polymerization temperature (50◦C: 1192 kg-PE/mmol-Zr·h, 75◦C: 209 kg-
PE/mmol-Zr·h). The introduction of an electron donating group, such as an n-hexyl and a methoxy group, on the imine nitrogen
or at the para-position of phenoxy oxygen in a benzene ring suppressed the activity decrease, however, the activity at 75◦C was
still lower than that at 50◦C. The combination of an n-hexyl or a cyclohexyl group on the imine nitrogen and a methoxy group at
the para-position of the phenoxy oxygen enhanced activity at 75◦C. Thus, N-[(3-t-butyl-5-methoxysalicylidene)-n-hexylami-
nato]zirconium(IV)dichloride (5) and N-[(3-t-butyl-5-methoxysalicylidene)cyclohexylaminato]zirconium(IV)dichloride (6)
displayed activities of greater than 1000 kg-PE/mmol-Zr h. Moreover, the introduction of an adamantyl or a cumyl group at the
position adjacent to the phenoxy oxygen further increased the activity. N-[(3-Adamantyl-5-methoxysalicylidene)cyclohexyla-
minato]zirconium(IV)dichloride (7), N-[(3-cumyl-5-methoxysalicylidene)-n-hexylaminato]zirconium(IV)dichloride (8), and
N-[(3-cumyl-5-methoxysalicylidene)cyclohexylaminato]zirconium(IV)dichloride (9) displayed exceptionally high activity
(7: 3052 kg-PE/mmol-Zr·h, 8: 7078 kg-PE/mmol-Zr·h, 9: 7224 kg-PE/mmol-Zr·h). © 2001 Published by Elsevier Science
B.V.
Keywords: Olefin polymerization catalyst; Polyethylene; Post-metallocene; Phenoxy-imine ligand; Zirconium; FI Catalysts
1. Introduction
development of highly active catalysts at high tem-
peratures has led to industrially useful technologies
since industrial olefin polymerization is conducted at
high temperatures, generally higher than 70◦C, in the
light of chemical engineering requirements.
A recent example is the development of the group
4 metallocenes, which produce a variety of poly-
olefins with novel properties, displaying high activity
at high polymerization temperatures [4–11]. Based
on the metallocene catalysts, the industrial produc-
tion of linear low-density polyethylene, isotactic
The research and development of highly active
olefin polymerization catalysts has significantly con-
tributed to not only academic fields but also to the
industrial domain [1–5]. In particular, historically, the
∗ Corresponding author. Tel.: +81-438-64-2317;
fax: +81-438-64-2375.
E-mail addresses: shigekazu.matsui@mitsui-chem.co.jp
(S. Matsui), terunori.fujita@mitsui-chem.co.jp (T. Fujita).
1381-1169/01/$ – see front matter © 2001 Published by Elsevier Science B.V.
PII: S1381-1169(01)00050-4

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N. Matsukawa et al. / Journal of Molecular Catalysis A: Chemical 169 (2001) 99–104
1
polypropylene, syndiotactic polypropylene, and syn-
diotactic polystyrene, etc. has been commercially
successful. Therefore, much effort has been devoted
to the research and development of transition metal
complexes with a view to creating new industrially
available olefin polymerization catalysts other than
the metallocene catalysts. As a result, recently, a
certain number of high performance new olefin poly-
merization catalysts have been discovered [12,13].
Some of them display a sufficiently high ethylene
polymerization activity for the industrial production
at high polymerization temperatures [14–16].
Recently, we have acquired new zirconium com-
plexes having two phenoxy-imine chelate ligands,
named FI Catalysts, which display a very high
ethylene polymerization activity using MAO as a
co-catalyst at ambient polymerization temperatures
under atmospheric pressure [17,18]. In addition, we
have revealed that the zirconium complexes are capa-
ble of producing polyethylene of low to exceptionally
high molecular weight by selecting the co-catalyst as
well as by changing the ligand structure [19,20]. As a
continuation of this work, we have investigated ethy-
lene polymerization using the zirconium complexes
at high temperatures, aimed at developing industrially
available new olefin polymerization catalysts.
the H NMR were referenced to an internal solvent
resonance and reported relative to tetramethylsilane
(TMS). Elemental analysis for CHN was carried out
by the CHNO type from the Helaus Co. The elemental
analysis for Zr was carried out using the ICP method
by a SHIMADZU ICPS-8000 after dry ashing and di-
lute nitric acid dissolution. The FD–MS spectra were
recorded on a SX-102A from Japan Electron Optics
Laboratory Co., Ltd.
2.1.2. Polymer characterization
The intrinsic viscosity [η] was measured in decalin
at 135◦C using an Ubbelohde viscometer. The viscos-
ity average molecular weight (Mv) values of polyethy-
lene were calculated using the following equation:
[η] = 6.2 × 10−4 Mv0.7 [21].
2.2. General complex synthesis procedure
2.2.1. Ligand Syntheses
Ligand syntheses were carried out under ni-
trogen using oven-dried glassware. Treatment
of an ortho-substituted phenol compound with
para-formaldehyde in the presence of ethylmagne-
siumbromide and triethylamine produced a salicy-
laldehyde compound in 60–80% yield [17,22]. This
compound reacted with a primary amine compound
via Schiff base condensation in ethanol to afford
the corresponding phenoxy-imine ligand in approxi-
mately 80–100% yield [17].
2. Experimental
2.1. General
2.2.2. Complex Syntheses
Dried solvents (tetrahydrofuran (THF), dichloro-
methane) used for complex syntheses were purchased
from Wako Pure Chemical Industries, Ltd., and used
without further purification. n-Heptane (Wako Pure
Chemical Industries, Ltd.) used as a polymerization
solvent was dried over Al2O3 and degassed by the bub-
bling of nitrogen gas. Cp2ZrCl2 (Wako Pure Chemi-
cal Industries, Ltd.) was used without further purifica-
tion. Ethylene was purchased from Sumitomo Seika
Co., Ltd. The co-catalyst, methylalmoxane (MAO)
was purchased from Albemarle as a 1.2 M toluene
solution, and the remaining trimethylaluminum was
evaporated in vacuo prior to use.
All complex synthesis manipulations were per-
formed with the exclusion of oxygen and moisture un-
der argon using standard Schlenk techniques. A typical
procedure for a complexation is as follows: to a stirred
solution of a phenoxy-imine ligand (10.0 mmol) in
THF (100 ml) at −78◦C, an n-butyllithium hexane
solution (10.5 mmol) was added dropwise over a
5 min period. The solution was allowed to warm to
room temperature and stirred for 2 h. The resulting
solution was added dropwise over a 30 min period to
a stirred solution of ZrCl4(THF)2 (5.0 mmol) in THF
(100 ml) at −78◦C. The mixture was allowed to warm
to room temperature and stirred for 15 h. The result-
ing mixture was concentrated in vacuo to give a solid
to which dichloromethane (60 ml) was added, and
the mixture stirred for 5 min. The resulting mixture
2.1.1. Ligand and complex analyses
NMR spectra were recorded on a JEOL270 spec-
trometer at ambient temperatures. Chemical shifts for

N. Matsukawa et al. / Journal of Molecular Catalysis A: Chemical 169 (2001) 99–104
101
was filtered, and then the residue was washed with
dichloromethane. The combined organic filtrates were
concentrated in vacuo to afford the crude complex.
The crude complex was recrystallized from solution
to give a zirconium complex.
12.42%. Calculated for ZrC36H40N2O4Cl2: C, 59.49;
H, 5.55; N, 3.85; Zr, 12.55%. FD–MS, 726 (M+).
2.7. Bis[N-(3-t-butyl-5-methoxysalicylidene)-n-
hexylaminato]zirconium(IV)dichloride (5)
1
2.3. Bis[N-(3-t-butylsalicylidene)anilinato]-
zirconium(IV)dichloride (1)
Yellow powder (22% yield). H NMR (CDCl3): δ.
0.80–1.75 (m, 22H, CH2, CH3), 1.58 (s, 18H, t-Bu),
3.41–3.69 (m, 4H, N–CH2), 3.83 (s, 6H, OMe), 6.69
(s, 2H, aromatic-H), 7.20 (s, 2H, aromatic-H), 8.14
Fluorescent yellow single crystals (52% yield).
1H NMR (CDCl3): δ. 1.33–1.59 (m, 18H, t-Bu),
(s, 2H, CH N). Anal. found: C, 57.98; H, 7.66; N,
=
=
6.78–7.42 (m, 16H, aromatic-H), 8.12 (s, 2H, CH N).
3.66; Zr, 12.40%. Calculated for ZrC36H56N2O4Cl2:
C, 58.20; H, 7.60; N, 3.77; Zr, 12.28%. FD–MS, 742
(M+).
Et2O of crystallization: [1.20 (t, 6H, J = 5.2 Hz,
CH3), 3.48 (q, 4H, J = 5.2 Hz, CH2)]. Anal. found:
C, 60.86; H, 5.36; N, 3.67; Zr, 12.70%. Calculated
for ZrC34H36N2O2Cl2 + Et2O: C, 61.60; H, 6.26; N,
3.78; Zr, 12.31%. FD–MS, 664 (M+) (see [18])
2.8. Bis[N-(3-t-butyl-5-methoxysalicylidene)cyclo-
hexylaminato]zirconium(IV)dichloride (6)
Yellow powder (74% yield). 1H NMR (CDCl3):
δ. 1.58 (s, 18H, t-Bu), 1.16–2.11 (m, 20H, CH2),
3.75–3.95 (m, 2H, CH), 3.80 (s, 6H, OMe), 6.64 (s,
2H, aromatic-H), 7.21 (s, 2H, aromatic-H), 8.19 (s, 2H,
2.4. Bis[N-(3-t-butylsalicylidene)-n-hexylaminato]-
zirconium(IV)dichloride (2)
1
Yellow crystals (35% yield). H NMR (CDCl3): δ.
=
0.90–1.54 (m, 40H, CH2, CH3, t-Bu), 3.40–3.55 (m,
CH N). Anal. found: C, 58.85; H, 7.35; N, 3.59; Zr,
4H, N–CH2), 6.81–7.55 (m, 6H, aromatic-H), 8.08
12.56%. Calculated for ZrC36H52N2O4Cl2: C, 58.51;
(s, 2H, CH N). Anal. found: C, 59.86; H, 7.56; N,
H, 7.09; N, 3.79; Zr, 12.35%. FD–MS, 738 (M+).
=
4.22; Zr, 13.25%. Calculated for ZrC34H52N2O2Cl2:
C, 59.80; H, 7.67; N, 4.10; Zr, 13.36%. FD–MS, 680
(M+).
2.9. Bis[N-(3-adamantyl-5-methoxysalicylidene)-
cyclohexylaminato]zirconium(IV)dichloride (7)
1
2.5. Bis[N-(3-t-butylsalicylidene)cyclohexylaminato]-
zirconium(IV)dichloride (3)
Yellow powder (13% yield). H NMR (CDCl3): δ.
0.87–2.49 (m, 50H, adamantyl-H, cyclohexyl–CH2),
3.79 (s, 6H, OMe), 3.74–4.00 (m, 2H, N–CH), 6.66 (s,
2H, aromatic-H), 7.13 (s, 2H, aromatic-H), 8.19 (s, 2H,
Yellow powder (43% yield). 1H NMR (CDCl3):
δ. 1.55 (s, 18H, t-Bu), 0.80–2.40 (m, 20H, CH2),
3.80–4.00 (m, 2H, CH), 6.79–7.64 (m, 6H, aromatic-H),
=
CH N). Anal. found: C, 64.58; H, 7.19; N, 3.49; Zr,
9.99%. Calculated for ZrC48H64N2O4Cl2: C, 64.40;
=
8.31 (s, 2H, CH N). Anal. found: C, 60.04; H, 7.44; N,
H, 7.21; N, 3.13; Zr, 10.19%. FD–MS, 894 (M+).
4.42; Zr, 13.28%. Calculated for ZrC34H48N2O2Cl2:
C, 60.15; H, 7.13; N, 4.13; Zr, 13.44%. FD–MS, 678
(M+).
2.10. Bis[N-(3-cumyl-5-methoxysalicylidene)-n-
hexylaminato]zirconium(IV)dichloride (8)
1
2.6. Bis[N-(3-t-butyl-5-methoxysalicylidene)anili-
nato]zirconium(IV)dichloride (4)
Yellow powder (32% yield). H NMR (CDCl3): δ.
0.50–2.02 (m, 34H, CH2), 2.38–2.82 (m, 4H, N–CH2),
3.78 (s, 3H, OMe), 3.83 (s, 3H, OMe), 6.37–7.51 (m,
Yellow crystals (68% yield). 1H NMR (CDCl3):
δ. 1.19–1.70 (m, 18H, t-Bu), 3.78 (brs, 6H, OMe),
6.47–7.35 (m, 14H, aromatic-H), 7.90–8.15 (m, 2H,
14H, aromatic-H), 7.85 (s, 2H, CH N). Anal. found:
=
C, 63.89; H, 7.19; N, 3.77; Zr, 10.22%. Calculated
for ZrC46H60N2O4Cl2: C, 63.72; H, 6.97; N, 3.23; Zr,
10.52%. FD–MS, 866 (M+).
=
CH N). Anal. found: C, 59.09; H, 5.61; N, 3.67; Zr,

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N. Matsukawa et al. / Journal of Molecular Catalysis A: Chemical 169 (2001) 99–104
2.11. Bis[N-(3-cumyl-5-methoxysalicylidene)-
cyclohexylaminato]zirconium(IV)dichloride (9)
ture and carefully degassed. Methanol (1000 ml) and
concentrated HCl (5 ml) were added to quench the
catalyst and solubilize the catalyst residue into the
acidic methanol. The resulting precipitate was col-
lected by filtration, washed with methanol (500 ml),
and dried in vacuo at 80◦C for 10 h to give polyethy-
lene.
Yellow powder (52% yield). 1H NMR (CDCl3):
δ. 0.81–2.12 (m, 20H, CH2), 1.84 (s, 6H, Me), 1.98
(s, 6H, Me), 3.54–3.75 (m, 2H, N–CH), 3.84 (s,
3H, OMe), 3.75 (s, 3H, OMe), 6.60–6.73 (m, 2H,
aromatic-H), 7.08–7.45 (m, 12H, aromatic-H), 8.11
=
(s, 2H, CH N). Anal. found: C, 64.44; H, 6.41; N,
3.59; Zr, 10.49%. Calculated for ZrC46H56N2O4Cl2:
C, 64.01; H, 6.54; N, 3.25; Zr, 10.57%. FD–MS, 863
(M+).
3. Results and discussion
A zirconium complex having two phenoxy-imine
chelate ligands, N-[(3-t-butylsalicylidene)anilinato]-
zirconium(IV)dichloride (1), was investigated for
ethylene polymerization using MAO as a cocatalyst
under 0.9 MPa ethylene pressure. At 50◦C, complex
1 displayed a very high activity of 1192 kg-PE/mmol-
Zr·h. However, at 75◦C, the activity decreased to
209 kg-PE/mmol-Zr·h. We assume that the activity
decrease was due to the low thermal stability of the
active species derived from complex 1, namely the
decomposition of the active species at a high temper-
ature. Hence, in order to suppress the decomposition
of the active species caused by the high temperature,
we modified the electronic character of the ligand
by introducing electron-donating group(s) at the R1
and/or R2 positions, since the introduction of electron
donating group(s) is (are) expected to strengthen the
bonds between the zirconium metal and the ligands,
thus, improving the thermal stability of the active
species.
2.12. Ethylene polymerization
Ethylene polymerization was carried out under
0.9 MPa ethylene pressure in n-heptane in a 1000 ml
stainless steel reactor equipped with a propeller-like
stirrer. n-Heptane (500 ml) was introduced into the
reactor under ethylene atmospheric pressure, and the
n-heptane was thermostated to a prescribed polymer-
ization temperature with stirring (150 rpm). A toluene
solution of MAO (1.25 M), and then a toluene solu-
tion of the complex were added to the reactor. For
initiating polymerization, the ethylene gas feed imme-
diately pumped into the reactor up to 0.9 MPa ethy-
lene pressure with vigorous stirring (350 rpm), and
the ethylene pressure was maintained at 0.9 MPa by
continuous ethylene feed. After 15 min, the ethylene
gas feed was ceased to terminate the polymerization.
The resulting mixture was cooled to room tempera-
Fig. 1. Ethylene polymerization activities at 50 and 75◦C displayed by complexes 1–6.

N. Matsukawa et al. / Journal of Molecular Catalysis A: Chemical 169 (2001) 99–104
103
Table 1
Ethylene polymerization results using complexes 1–6a
Entry
Complex
Amount of complex (␮ mol)
Temperature (◦C)
Yield (g)
Activity (kg-PE/mmo1-Zr·h)
Mv/104
1
2
3
4
5
6
7
8
9
10
11
12
13
14
1
1
2
2
3
3
4
4
5
5
6
6
0.05
0.05
0.2
0.2
0.1
0.1
0.1
0.1
0.05
0.05
0.05
0.05
0.2
50
75
50
75
50
75
50
75
50
75
50
75
50
75
14.90
2.61
17.30
6.99
18.78
5.27
8.19
5.51
5.67
12.59
10.22
18.28
1.92
1192
209
346
140
751
211
328
220
454
1008
818
1462
38
4.7
10.0
1.1
2.0
1.5
3.0
36.3
22.7
9.9
3.8
16.8
5.4
Cp2ZrCl2
Cp2ZrCl2
43.1
19.6
0.2
4.86
97
a Conditions: 0.9 MPa ethylene pressure, MAO (Al); 1.25 mmol, n-heptane, 500 ml; polymerization time, 15 min.
The introduction of an n-hexyl or a cyclohexyl
group instead of the phenyl group at the R1 position,
complexes 2 (R1 = n-hexyl) and 3 (R1 = cyclohexyl),
resulted in mitigating the activity decrease, based on
a comparison of the activities at 50 and 75◦C.
Alternatively, the introduction of a methoxy group
at the R2 position, complex 4, also resulted in sup-
pressing the activity decrease. Although the activity
decrease for complexes 2–4 was mitigated compared
to that for complex 1, the absolute activity values dis-
played by complexes 2–4 at 75◦C were nearly equal
to or less than that exhibited by complex 1.
Surprisingly, a combination of an n-hexyl or a cy-
clohexyl group at the R1 position and a methoxy group
at the R2 position was very effective in enhancing the
activity at 75◦C. Complexes 5 (R1 = n-hexyl, R2 =
OMe) and 6 (R1 = cyclohexyl, R2 = OMe) dis-
played activities of 1008 and 1462 kg-PE/mmol-Zr·h
at 75◦C, respectively. These activity values were 5–7
times higher than that displayed by complex 1 at 75◦C,
and moreover, far superior to that of Cp2ZrCl2 (Fig. 1
and Table 1).
We have recently reported that changing the t-butyl
group at the R3 position to an adamantyl or a cumyl
Table 2
Ethylene polymerization results using complexes 7–9a
Entry
1
Complex
R1
R3
Amount of
complex (␮mol)
Temperature (◦C)
50
Yield (g)
9.49
Activity
(kg-PE/mmol-Zr·h)
1898
Mv/104
7
Cyclohexyl
Adamantyl
0.02
32.8
2
3
7
8
Cyclohexyl
n-Hexyl
Adamantyl
Cumyl
0.02
0.01
75
50
15.26
8.12
3052
3250
9.5
13.4
4
5
6
8
9
9
n-Hexyl
Cyclohexyl
Cyclohexyl
Cumyl
Cumyl
Cumyl
0.01
0.01
0.005
75
50
75
17.70
9.16
9.06
7078
3665
7224
3.9
17.2
10.4
a Conditions: 0.9 MPa ethylene pressure, MAO (M); 1.25 mmol, n-heptane, 500 ml; polymerization time, 15 mm.

104
N. Matsukawa et al. / Journal of Molecular Catalysis A: Chemical 169 (2001) 99–104
group, sterically larger than the t-butyl group, en-
hanced the polymerization activity at 25◦C under
ethylene at atmospheric pressure [19,20]. There-
fore, we prepared complexes 7 (R1 = cyclohexyl,
R2 = OMe, R3 = adamantyl), 8 (R1 = n-hexyl,
R2 = OMe, R3 = cumyl) and 9 (R1 = cyclohexyl,
R2 = OMe, R3 = cumyl), and investigated the
complexes for ethylene polymerization at 0.9 MPa
ethylene pressure at 50 and 75◦C (Table 2).
therefore, these complexes possess great potential as
new olefin polymerization catalysts.
Acknowledgements
We would like to thank T. Hayashi, M. Nitabaru, Y.
Tohi, T. Nakano, H. Tanaka, S. Matsuura, S. Ishii, J.
Mohri and A. Valentine for their research and technical
assistance.
As expected, complexes 7–9 displayed much higher
activities at 50 and 75◦C compared to the correspond-
ing complexes having the t-butyl group at the R3
position. Namely, complex 7, having an adamantyl
group at the R3 position, exhibited ethylene polymer-
ization activities of 1898 and 3052 kg-PE/mmol-Zr·h
at 50 and 75◦C, respectively. Furthermore, complexes
8 and 9, both having a cumyl group at the R3 position,
exhibited exceptionally high ethylene polymerization
activities of 3250 and 3665 kg-PE/mmol-Zr·h at 50◦C,
respectively. Moreover, these complexes displayed
higher activities at 75◦C (8: 7078 kg-PE/mmol-Zr·h
and 9: 7224 kg-PE/mmol-Zr·h) than those at 50◦C. As
far as we are aware, the activities displayed by com-
plexes 8 and 9 at 75◦C under 0.9 MPa ethylene pres-
sure, more than 7000 kg-PE/mmol-Zr·h, are some of
the highest values exhibited by olefin polymerization
catalysts under the same or similar polymerization
conditions.
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In this study, we demonstrated that zirconium com-
plexes bearing two phenoxy-imine chelate ligands,
FI Catalysts, displayed very high ethylene polymer-
ization activities at 75◦C under 0.9 MPa ethylene
pressure as a result of a suitable catalyst design.
Although the proto-catalyst 1 displayed decreased ac-
tivity at 75◦C compared to that at 50◦C, introducing
electron-donating groups at the R1 and R2 positions
increased the activity at 75◦C. Moreover, further
improvement in the activity at 75◦C is achieved by
the introduction of an adamantyl or a cumyl group
at the R3 position. Thus, exceptionally high activity,
more than 7000 kg-PE/mmol-Zr h, is attained using
8 and 9, both having a cumyl group at the R3 po-
sition. These results clearly indicate that zirconium
complexes having two phenoxy-imine ligands have
not only potential capacity but also practical use, and
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