Living polymerization of ethylene catalyzed by titanium complexes having fluorine-containing phenoxy-imine chelate ligands

Article abstract of DOI:10.1021/ja0117581

Seven titanium complexes bearing fluorine-containing phenoxy-imine chelate ligands, TiCl₂-{η²-1-[C(H) = NR]-2-O-3-^tBu-C₆H₃}₂ [R = 2,3,4,5,6-pentafluorophenyl (1), R = 2,4,6-trifluorophenyl (2), R = 2,6-difluorophenyl (3), R = 2-fluorophenyl (4), R = 3,4,5-trifluorophenyl (5), R = 3,5-difluorophenyl (6), R = 4-fluorophenyl (7)], were synthesized from the lithium salt of the requisite ligand and TiCl₄ in good yields (22%-76%). X-ray analysis revealed that the complexes 1 and 3 adopt a distorted octahedral structure in which the two phenoxy oxygens are situated in the trans-position while the two imine nitrogens and the two chlorine atoms are located cis to one another, the same spatial disposition as that for the corresponding nonfluorinated complex. Although the Ti-O, Ti-N, and Ti-Cl bond distances for complexes 1 and 3 are very similar to those for the nonfluorinated complex, the bond angles between the ligands (e.g., O-Ti-O, N-Ti-N, and Cl-Ti-Cl) and the Ti-N-C-C torsion angles involving the phenyl on the imine nitrogen are different from those for the nonfluorinated complex, as a result of the introduction of fluorine atoms. Complex 1/methylalumoxane (MAO) catalyst system promoted living ethylene polymerization to produce high molecular weight polyethylenes (M_n > 400 000) with extremely narrow polydispersities (M_w/M_n < 1.20). Very high activities (TOF > 20 000 min^-1 atm^-1) were observed that are comparable to those of Cp₂ZrCl₂/MAO at high polymerization temperatures (25, 50°C). Complexes 2-4, which have a fluorine atom adjacent to the imine nitrogen, behaved as living ethylene polymerization catalysts at 50°C, whereas complexes 5-7, possessing no fluorine adjacent to the imine nitrogen, produced polyethylenes having M_w/M_n values of ca. 2 with β-hydrogen transfer as the main termination pathway. These results together with DFT calculations suggested that the presence of a fluorine atom adjacent to the imine nitrogen is a requirement for the high-temperature living polymerization, and the fluorine of the active species for ethylene polymerization interacts with a β-hydrogen of a polymer chain, resulting in the prevention of β-hydrogen transfer. This catalyst system was used for the synthesis of a number of unique block copolymers such as polyethylene-b-poly(ethylene-co-propylene) diblock copolymer and polyethylene-b-poly(ethylene-co-propylene)-b-syndiotactic polypropylene triblock copolymer from ethylene and propylene.

Full text of DOI:10.1021/ja0117581

Published on Web 03/06/2002
Living Polymerization of Ethylene Catalyzed by Titanium
Complexes Having Fluorine-Containing Phenoxy-Imine
Chelate Ligands
Makoto Mitani, Jun-ichi Mohri, Yasunori Yoshida, Junji Saito, Seiichi Ishii,
Kazutaka Tsuru, Shigekazu Matsui, Rieko Furuyama, Takashi Nakano,
Hidetsugu Tanaka, Shin-ichi Kojoh, Tomoaki Matsugi, Norio Kashiwa, and
Terunori Fujita*
Contribution from the R & D Center, Mitsui Chemicals, Inc., 580-32 Nagaura, Sodegaura,
Chiba, 299-0265, Japan
Received July 19, 2001
Abstract: Seven titanium complexes bearing fluorine-containing phenoxy-imine chelate ligands, TiCl2-
{η2-1-[C(H)dNR]-2-O-3-tBu-C6H3}2 [R ) 2,3,4,5,6-pentafluorophenyl (1), R ) 2,4,6-trifluorophenyl (2), R
) 2,6-difluorophenyl (3), R ) 2-fluorophenyl (4), R ) 3,4,5-trifluorophenyl (5), R ) 3,5-difluorophenyl (6),
R ) 4-fluorophenyl (7)], were synthesized from the lithium salt of the requisite ligand and TiCl4 in good
yields (22%-76%). X-ray analysis revealed that the complexes 1 and 3 adopt a distorted octahedral structure
in which the two phenoxy oxygens are situated in the trans-position while the two imine nitrogens and the
two chlorine atoms are located cis to one another, the same spatial disposition as that for the corresponding
nonfluorinated complex. Although the Ti-O, Ti-N, and Ti-Cl bond distances for complexes 1 and 3 are
very similar to those for the nonfluorinated complex, the bond angles between the ligands (e.g., O-Ti-O,
N-Ti-N, and Cl-Ti-Cl) and the Ti-N-C-C torsion angles involving the phenyl on the imine nitrogen
are different from those for the nonfluorinated complex, as a result of the introduction of fluorine atoms.
Complex 1/methylalumoxane (MAO) catalyst system promoted living ethylene polymerization to produce
high molecular weight polyethylenes (Mn > 400 000) with extremely narrow polydispersities (Mw/Mn < 1.20).
Very high activities (TOF > 20 000 min-1 atm-1) were observed that are comparable to those of Cp2ZrCl2/
MAO at high polymerization temperatures (25, 50 °C). Complexes 2-4, which have a fluorine atom adjacent
to the imine nitrogen, behaved as living ethylene polymerization catalysts at 50 °C, whereas complexes
5-7, possessing no fluorine adjacent to the imine nitrogen, produced polyethylenes having Mw/Mn values
of ca. 2 with â-hydrogen transfer as the main termination pathway. These results together with DFT
calculations suggested that the presence of a fluorine atom adjacent to the imine nitrogen is a requirement
for the high-temperature living polymerization, and the fluorine of the active species for ethylene
polymerization interacts with a â-hydrogen of a polymer chain, resulting in the prevention of â-hydrogen
transfer. This catalyst system was used for the synthesis of a number of unique block copolymers such as
polyethylene-b-poly(ethylene-co-propylene) diblock copolymer and polyethylene-b-poly(ethylene-co-pro-
pylene)-b-syndiotactic polypropylene triblock copolymer from ethylene and propylene.
Introduction
method. Recent research effort devoted to the study of soluble,
well-defined transition metal complexes for olefin polymeriza-
There has been great interest in the discovery and develop-
ment of high-performance living olefin polymerization catalysts
based on soluble, well-defined transition metal complexes. This
is because of the usefulness of living olefin polymerization
techniques for the preparation of precisely controlled polymers
such as monodisperse polymers, terminally functionalized
polymers, and block copolymers, all of which are anticipated
to possess novel properties and new uses as high-performance
polymers. However, living olefin polymerization required low
temperatures, normally below room temperature, to suppress
the chain termination or transfer steps (e.g., â-hydride elimina-
tion, â-alkyl elimination, and chain transfer to a cocatalyst),
and thus it generally exhibits low activity with insufficient
molecular weight value, which has restricted the utility of this
tion1,2 has resulted in the introduction of a variety of high-
performance catalysts for the living polymerization of olefins3-15
such as ethylene, propylene, 1-hexene, and higher R-olefins.
Some of the catalysts promote the room-temperature living
polymerization of 1-hexene.7 Some are active for stereospecific
(1) (a) Kaminsky, W.; Ku¨lper, K.; Brintzinger, H. H.; Wild, F. R. W. P. Angew.
Chem., Int. Ed. Engl. 1985, 97, 507-508. (b) Kaminsky, W. Catal. Today
1994, 20, 257-271. (c) Mo¨hring, P. C.; Coville, N. J. J. Organomet. Chem.
1994, 479, 1-29. (d) Brintzinger, H. H.; Fischer, D.; Mu¨lhaupt, R.; Rieger,
B.; Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143-1170.
(e) Kaminsky, W.; Arndt, M.; AdV. Polym. Sci. 1997, 127, 144-187. (f)
Coates, G. W. Chem. ReV. 2000, 100, 1223-1252.
(2) For recent reviews, see: (a) Britovsek, G. J. P.; Gibson, V. C.; Wass, D.
F. Angew. Chem., Int. Ed. 1999, 38, 428-447. (b) Ittel, S. D.; Johnson, L.
K.; Brookhart, M. Chem. ReV. 2000, 100, 1169-1203. And references were
cited in ref 16i.
9
10.1021/ja0117581 CCC: $22.00 © 2002 American Chemical Society
J. AM. CHEM. SOC. 2002, 124, 3327-3336
3327

A R T I C L E S
Mitani et al.
living polymerization of propylene4-6 or 1-hexene.9 In addition,
others are capable of producing R-olefin-based block copoly-
mers.10 There are, however, a limited number of catalysts that
promote room-temperature living ethylene polymerization.11-15
Moreover, the preparation of well-defined ethylene-based block
copolymers has not yet been reported.
Scheme 1
Previously we developed, as a result of ligand-oriented
catalyst design research, a new family of group 4 transition metal
complexes possessing a pair of phenoxy-imine chelate ligands,
named FI Catalysts,16 that show exceptionally high ethylene
polymerization activities. FI Catalysts have been found to
produce various new polymers such as very low molecular
weight polyethylenes and ethylene-propylene copolymers,
(3) (a) Hagihara, H.; Shiono, T.; Ikeda, T. Macromolecules 1998, 31, 3184-
3188. (b) Hasan, T.; Ioku, A.; Nishii, K.; Shiono, T.; Ikeda, T. Macro-
molecules 2001, 34, 3142-3145. (c) Fukui, Y.; Murata, M.; Soga, K.
Macromol. Rapid Commun. 1999, 20, 637-640. (d) Turner, H. W.; Hlatky,
G. G. Exxon, PCT International Application 9112285, 1991 (Chem. Abstr.
1992, 116, 61330t).
(4) (a) Doi, Y.; Keii, T. AdV. Polym. Sci. 1986, 73-4, 201-248. (b) Doi, Y.;
Tokuhiro, N.; Soga, K. Makromol. Chem., Macromol. Chem. Phys. 1989,
190, 643-651 and references therein.
ultrahigh molecular weight polyethylenes and ethylene-pro-
pylene copolymers,16i and high molecular weight poly-1-hexenes
having an atactic structure with considerable regioirregular
units.16e Further studies on the FI Catalysts having heteroatom(s)
and/or heteroatom-containing substituent(s) in the ligand have
led to the discovery of a new series of FI Catalysts having
fluorine atom(s) in the ligand that display unprecedented
catalytic performance for the living polymerization of ethylene.17
In this contribution, we report the syntheses, structures, and
ethylene polymerization behavior of FI Catalysts having fluorine-
containing ligand and introduce a new breakthrough for achiev-
ing high-temperature living ethylene polymerization. In addition,
we describe the preparation of di- and triblock copolymers in
order to demonstrate the usefulness of the catalysts for the
synthesis of the desired precisely controlled polymers.
(5) Tian, J.; Hustad, P. D.; Coates, G. W. J. Am. Chem. Soc. 2001, 123, 5134-
5135.
(6) (a) Saito, J.; Mitani, M.; Mohri, J.; Ishii, S.; Yoshida, Y.; Matsugi, T.;
Kojoh, S.; Kashiwa, N.; Fujita, T. Chem. Lett. 2001, 576-577. (b) Kojoh,
S.; Matsugi, T.; Saito, J.; Mitani, M.; Fujita, T.; Kashiwa, N. Chem. Lett.
2001, 822-823. (c) Saito, J.; Mitani, M.; Onda, M.; Mohri, J.; Ishii, S.;
Yoshida, Y.; Nakano, T.; Tanaka, H.; Matsugi, T.; Kojoh, S.; Kashiwa,
N.; Fujita, T. Macromol. Rapid Commun. 2001, 22, 1072-1075.
(7) (a) Scollard, J. D.; McConville, D. H. J. Am. Chem. Soc. 1996, 118, 10008-
10009. (b) Scollard, J. D.; McConville, D. H.; Vittal, J. J.; Payne, N. C. J.
Mol. Catal. A. 1998, 128, 201-214.
(8) (a) Baumann, R.; Davis, W. M.; Schrock, R. R. J. Am. Chem. Soc. 1997,
119, 3830-3831. (b) Liang, L. C.; Schrock, R. R.; Davis, W. M.;
McConville, D. H. J. Am. Chem. Soc. 1999, 121, 5797-5798. (c)
Mehrkhodavandi, M.; Schrock, R. R. J. Am. Chem. Soc. 2001, 123, 10746-
10747. (d) Y.-M. Jeon, S. J. Park, J. Heo, K. Kim, Organometallics 1998,
17, 3161-3163. (e) Tshuva, E. Y.; Goldberg, I.; Kol, M.; Goldschmidt, Z.
Inorg. Chem. Commun. 2000, 3, 611-614.
(9) (a) Jayaratne, K. C.; Sita, L. R. J. Am. Chem. Soc. 2000, 122, 958-959.
(b) Jayaratne, K. C.; Keaton, R. J.; Henningsen, D. A.; Sita, L. R. J. Am.
Chem. Soc. 2000, 122, 10490-10491. (c) Keaton, R. J.; Jayaratne, K. C.;
Henningsen, D. A.; Koterwas, L. A.; Sita, L. R. J. Am. Chem. Soc. 2001,
123, 6197-6198. (d) Jayaratne, K. C.; Sita, L. R. J. Am. Chem. Soc. 2001,
123, 10754-10755.
(10) (a) Johnson, L. K.; Killian, C. M.; Brookhart, M. J. Am. Chem. Soc. 1995,
117, 6414-6415. (b) Killian, C. M.; Tempel, D. J.; Johnson, L. K.;
Brookhart, M. J. Am. Chem. Soc. 1996, 118, 11664-11665.
(11) Yasuda, H.; Furo, M.; Yamamoto, H.; Nakamura, A.; Miyake, S.; Kibino,
N. Macromolecules 1992, 25, 5115-5116.
(12) (a) Mashima, K.; Fujikawa, S.; Nakamura, A. J. Am. Chem. Soc. 1993,
115, 10990-10991. (b) Mashima, K.; Fujikawa, S.; Urata, H.; Tanaka, E.;
Nakamura, A. J. Chem. Soc., Chem. Commun. 1994, 1623-1624. (c)
Mashima, K.; Fujikawa, S.; Tanaka, Y.; Urata, H.; Oshiki, T.; Tanaka, E.;
Nakamura, A. Organometallics 1995, 14, 2633-2640.
Results and Discussion
Synthesis of Titanium Complexes Having Fluorine-
Containing Phenoxy-Imine Chelate Ligands. A general
synthetic route for the titanium complexes employed in this
study, bis[N-(3-tert-butylsalicylidene)fluoroanilinato]titanium(IV)
dichloride 1-7, is depicted in Scheme 1. The fluorine-containing
phenoxy-imine chelate ligands (a-g), N-(3-tert-butylsali-
cylidene)fluoroaniline, are synthesized in high yields (82-98%)
by the Schiff base condensation of the corresponding fluorine-
containing aniline with 3-tert-butylsalicylaldehyde using an acid
as a catalyst. The desired titanium complexes 1-7 are prepared
in moderate to good yields (22-76%) by the reaction of TiCl4
with 2 equiv of the lithium salt of the fluorine-containing
phenoxy-imine ligands in dried diethyl ether. The overall yields
starting from commercially available 3-tert-butylsalicylaldehyde
are fairly good.
(13) Brookhart, M.; DeSimone, J. M.; Grant, B. E.; Tanner, M. J. Macromol-
ecules 1995, 28, 5378-5380.
(14) Gottfried, A. C.; Brookhart, M. Macromolecules 2001, 34, 1140-1142.
(15) Matsugi, T.; Matsui, S.; Kojoh, S.; Takagi, Y.; Inoue, Y.; Fujita, T.;
Kashiwa, N. Chem. Lett. 2001, 566-567.
(16) (a) Fujita, T.; Tohi, Y.; Mitani, M.; Matsui, S.; Saito, J.; Nitabaru, M.;
Sugi, K.; Makio, H.; Tsutsui, T. Europe Patent, EP-0874005, 1998 (Chem.
Abstr. 1998, 129, 331166). (b) Matsui, S.; Tohi, Y.; Mitani, M.; Saito, J.;
Makio, H.; Tanaka, H.; Nitabaru, M.; Nakano, T.; Fujita, T. Chem. Lett.
1999, 1065-1066. (c) Matsui, S.; Mitani, M.; Saito, J.; Tohi, Y.; Makio,
H.; Tanaka, H.; Fujita, T. Chem. Lett., 1999 1263-1264. (d) Matsui, S.;
Mitani, M.; Saito, J.; Matsukawa, N.; Tanaka, H.; Nakano, T.; Fujita, T.
Chem. Lett. 2000, 554-555. (e) Saito, J.; Mitani, M.; Matsui, S.; Kashiwa,
N.; Fujita, T. Macromol. Rapid Commun. 2000, 21, 1333-1336. (f) Matsui,
S.; Fujita, T. Catal. Today 2001, 66, 63-73. (g) Yoshida, Y.; Matsui, S.;
Takagi, Y.; Mitani, M.; Nitabaru, M.; Nakano, T.; Tanaka, H.; Fujita, T.
Chem. Lett. 2000, 1270-1271. (h) Matsukawa, N.; Matsui, S.; Mitani, M.;
Saito, J.; Tsuru, K.; Kashiwa, N.; Fujita, T. J. Mol. Catal. A 2001, 169,
99-104. (i) Matsui, S.; Mitani, M.; Saito, J.; Tohi, Y.; Makio, H.;
Matsukawa, N.; Takagi, Y.; Tsuru, K.; Nitabaru, M.; Nakano, T.; Tanaka,
H.; Kashiwa, N.; Fujita, T. J. Am. Chem. Soc. 2001, 123, 6847-6856. (j)
Saito, J.; Mitani, M.; Matsui, S.; Tohi, Y.; Makio, H.; Nakano, T.; Tanaka,
H.; Kashiwa, N.; Fujita, T. Macromol. Chem. Phys. 2002, 203, 59-65. (k)
Ishii, S.; Saito, J.; Mitani, M.; Mohri, J.; Matsukawa, N.; Tohi, Y.; Matsui,
S.; Kashiwa, N.; Fujita, T. J. Mol. Catal. A 2002, 179, 11-16. (l) Yoshida,
Y.; Matsui, S.; Takagi, Y.; Mitani, M.; Nakano, T.; Tanaka, H.; Kashiwa,
N.; Fujita, T. Organometallics 2001, 20, 4793-4799. (m) Tian, J.; Coates,
G. W. Angew. Chem., Int. Ed. 2000, 39, 3626-3629.
X-ray Analyses of Complexes 1 and 3. The molecular
structures of complexes 1 and 3 were determined by X-ray
(17) (a) Mitani, M.; Yoshida, Y.; Mohri, J.; Tsuru, K.; Ishii, S.; Kojoh, S.;
Matsugi, T.; Saito, J.; Matsukawa, N.; Matsui, S.; Nakano, T.; Tanaka, H.;
Kashiwa, N.; Fujita, T. WO Pat. 01/55231 A1, 2001. (b) Fujita, T.; Mitani,
M.; Matsui, S.; Saito, J.; Yoshida, Y.; Tohi, Y.; Matsukawa, N.; Ishii, S.;
Mohri, J.; Inoue, Y.; Nakano, T.; Tanaka, H.; Matsugi, T.; Kojoh, S.;
Kashiwa, N. International Symposium on Future Technology for Olefin
and Olefin Polymerization Catalysis, proceedings, Tokyo, March 2001,
Abstr. No. OP-21. (c) Saito, J.; Mitani, M.; Mohri, J.; Yoshida, Y.; Matsui,
S.; Ishii, S.; Kojoh, S.; Kashiwa, N.; Fujita, T. Angew. Chem., Int. Ed.
2001, 40, 2918-2920.
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Polymerization of Ethylene Catalyzed by Ti Complexes
A R T I C L E S
atoms (being situated in the cis-position). Therefore, the spatial
arrangement of complexes 1 and 3 is the same as that of complex
8. Assuming that two chlorine-bound sites are transformed to
olefin polymerization sites while retaining their stereochemical
cis-relationship, active species for olefin polymerization, derived
from complexes 1 and 3, possess two available cis-located sites
convenient for olefin polymerization. Although the Ti-O, Ti-
N, and Ti-Cl bond distances for complexes 1 and 3 are very
similar to those for nonfluorinated complex 8, the bond angles
between the ligands (e.g., O-Ti-O, N-Ti-N, and Cl-Ti-
Cl) are different compared with those for complex 8. Complexes
1 and 3 have the narrower Cl-Ti-Cl and O-Ti-O angles and
wider N-Ti-N angle relative to those for complex 8. In
addition, complexes 1 and 3 possess wider Ti-N-C-C torsion
angles involving the phenyl on the imine nitrogen than complex
8. These differences in the angles probably originate from the
steric repulsion between the fluorine adjacent to the imine
nitrogen and the tert-butyl group in the phenoxy benzene rings
and electronic repulsion between the fluorine adjacent to the
imine nitrogen and the chlorine atoms bound to the titanium
metal. Since the F atoms are situated near Cl atoms, potential
olefin polymerization sites, the F atoms are expected to affect
the olefin polymerization process.
Figure 1. Molecular structure of complex 1 with thermal ellipsoids at 50%
probability level.
Living Ethylene Polymerization Promoted by the Complex
1/MAO System. Ethylene polymerizations with complex 1 and
a typical metallocene, Cp2ZrCl2, as a comparison, using methyl-
alumoxane (MAO) as a cocatalyst, were carried out at 25, 50,
and 75 °C under atmospheric pressure. The results are collected
in Table 2. At 25 °C the activity of the complex 1/MAO catalyst
system was found to be competitive with Cp2ZrCl2/MAO
(entries 1, 2, 7). Thus, complex 1 displayed very high activities
(TOF values: entry 1, 21 200 min-1 atm-1; entry 2, 20 200
min-1 atm-1), the activities being comparable to that exhibited
by Cp2ZrCl2 (TOF value: entry 7, 18 400 min-1 atm-1). It is
noteworthy that the polyethylenes produced with complex
1/MAO possess extremely narrow polydispersities (Mw/Mn )
1.15, 1.13) and high molecular weights (Mn ) 191 000,
412 000). In addition, the Mn value and polymer yield obtained
at 1 min polymerization (entry 2) is practically twice that for
0.5 min polymerization (entry 1). These results suggest that the
ethylene polymerization catalyzed by complex 1/MAO catalyst
system proceeds in a living fashion, though Cp2ZrCl2/MAO
produced polyethylenes having Mw/Mn values of ca. 2, typical
value for nonliving system, under the same conditions. The Mn
(>400 000) represents one of the highest values and, at the same
time, the TOF value (>20 000 min-1 atm-1) is also one of the
highest activities for living ethylene polymerizations. In fact,
the activities displayed by complex 1/MAO are 3 orders of
magnitude larger than those for the known living ethylene
polymerization catalyst systems (TOF values, ca. 20 min-1
atm-1). To the best of our knowledge, this is the first example
of an exceptionally high-speed room-temperature living ethylene
polymerization that produces very high molecular weight
polyethylene with narrow polydispersity (Mw/Mn < 1.20).
Melting temperatures (Tm) of the produced polyethylenes were
137 °C (entry 1) and 135 °C (entry 2), respectively, and 13C
NMR analyses of the polymers indicate that the polyethylenes
have linear structures with virtually no branching. Generally,
an increase in temperature for living polymerization causes chain
transfers, resulting in the loss of living character. Surprisingly,
Figure 2. Molecular structure of complex 3 with thermal ellipsoids at 30%
probability level.
Table 1. Selected Bond Distances (Å), Angles (deg), and Torsion
Angles (deg) for Complexes 1, 3, and 8
complex
1
3
8
Bond Distances
2.2876(7)
2.2578(8)
1.841(1)
1.845(1)
2.234(2)
2.217(2)
1.298(3)
1.296(3)
1.437(3)
Ti-Cl(1)
2.2799(9)
2.2811(9)
1.848(2)
1.872(2)
2.218(2)
2.217(2)
1.298(3)
1.289(3)
1.435(3)
1.451(3)
2.296(2)
2.305(1)
1.851(3)
1.852(3)
2.213(4)
2.236(4)
1.286(6)
1.295(6)
1.441(5)
1.443(6)
Ti-Cl(2)
Ti-O(1)
Ti-O(2)
Ti-N(1)
Ti-N(2)
N(1)-C(7)
N(2)-C(24)
N(1)-C(8)
N(2)-C(25)
1.428(3)
Bond Angles
96.42(3)
163.61(6)
86.94(7)
Cl(1)-Ti-Cl(2)
O(1)-Ti-O(2)
N(1)-Ti-N(2)
98.09(4)
166.99(8)
86.18(8)
103.11(6)
171.6(1)
76.4(1)
Torsion Angles
Ti-N(1)-C(8)-C(9)
-95.5(2)
-106.7(3)
-93.5(3)
-76.9(5)
-63.2(5)
Ti-N(2)-C(25)-C(26) -85.3(3)
crystallography. The structures are shown in Figures 1 and 2,
while key bond distances and angles, together with those for
the corresponding nonfluorinated complex 8,16j are summarized
in Table 1. The X-ray structures of complexes 1 and 3 feature
a distorted octahedral complex in which the titanium is bound
to two cis-coordinated [O, N] chelating ligands (the oxygen
atoms being situated in the trans-position) and the two chlorine
9
J. AM. CHEM. SOC. VOL. 124, NO. 13, 2002 3329

A R T I C L E S
Mitani et al.
Table 2. Results of Ethylene Polymerization with Complex 1/MAOa
entry
complex (µmol)
temp (°C)
time (min)
polymer yield (g)
TOF (min-1‚atm-1
)
M b (×103)
M /M b
n
w
n
1
2
3
4
5
6
7
8
1 (0.5)
1 (0.5)
1 (0.5)
1 (0.5)
1 (1.0)
25
25
50
50
75
75
25
50
0.5
1
0.5
1
0.5
1
1
0.149
0.283
0.172
0.302
0.247
0.453
0.258
0.433
21 200
20 200
24 500
21 500
17 600
16 100
18 400
30 900
191
412
257
424
214
329
157
136
1.15
1.13
1.08
1.13
1.09
1.15
1.73
2.26
1 (1.0)
Cp2ZrCl2 (0.5)
Cp2ZrCl2 (0.5)
1
a Conditions: MAO cocatalyst (1.25 mmol), 1 atm, ethylene feed 100 L/h, 250 mL toluene. b Determined by GPC using polyethylene calibration.
Table 3. Results of Ethylene Polymerization with Complex 1/MAO Using Diluted Ethylene and Various Polymerization Temperaturesa
T ) 25 °C
M b (×103)
T ) 50 °C
M b (×103)
T ) 75 °C
M b (×103)
time (min)
polymer yield (g)
M /M b
polymer yield (g)
M /M b
polymer yield (g)
M /M b
w n
n
w
n
n
w
n
n
3
5
10
15
0.027
0.059
0.113
0.175
35
56
103
144
1.05
1.07
1.09
1.13
0.049
0.100
0.150
54
95
137
1.06
1.14
1.19
0.052
0.122
0.131
82
135
160
1.30
1.65
2.05
a Conditions: 1.0 µmol 1, 1.25 mmol MAO cocatalyst, 1 atm, ethylene/N2 feed 2 L/50 L/h (25, 50 °C), 5 L/50 L/h (75 °C), 250 mL toluene. b Determined
by GPC using polyethylene calibration.
Figure 4. GPC profile of polyethylenes obtained by complex 1/MAO at
25 °C: (a) 3 min, Mn ) 35 000, Mw/Mn ) 1.05 (b) 5 min, Mn ) 56 000,
Figure 3. Plots of Mn and Mw/Mn as a function of polymerization time for
Mw/Mn ) 1.07 (c) 10 min, Mn ) 103 000, Mw/Mn ) 1.09 (d) 15 min, Mn
ethylene polymerization with complex 1/MAO at 25 °C.
) 144 000, Mw/Mn ) 1.13.
as presented in Table 2 (entries 3-6) the complex 1/MAO
molecular weight of the polyethylene was close to that calculated
from the monomer/initiator ratio obtained from the mass of the
polyethylene produced, showing that catalyst efficiency is
substantially quantitative. These results clearly indicate that this
catalyst system promotes highly controlled living ethylene
polymerization at room temperature.
catalyst system produced polyethylenes having extremely narrow
polydispersities (Mw/Mn ) 1.08-1.15) even at 50 and 75 °C.
The temperature tolerance for performing living polymerization
is exceptionally high compared with the known living polym-
erization systems, and therefore, it is of great significance.
To further confirm the living nature of the catalyst system,
Mn and Mw/Mn values for complex 1/MAO at 25 °C were
monitored as a function of polymerization time. Since complex
1/MAO is highly active for ethylene polymerization, long
polymerization time may cause undesirable broadening of
MWD, because of nonhomogenity of the polymerization system
due to excess polymer precipitation. Consequently, we carried
out polymerizations using diluted ethylene with nitrogen under
atmospheric pressure. As shown in Table 3 and Figure 3, a linear
relationship between Mn and polymerization time as well as
narrow Mw/Mn values for all runs (Mw/Mn ) 1.05-1.13) were
found. Moreover, GPC peaks of the produced polyethylene
shifted to higher molecular weight region with an increase in
polymerization time while the monomodal shape was retained,
and no shoulder peak and/or low molecular weight tail was
detected during the course of the polymerization (Figure 4). The
To investigate the living nature of the system at higher
temperatures, Mn and Mw/Mn values vs polymerization time were
plotted for the ethylene polymerization performed at 50 and 75
°C using the same polymerization method. As a result, at 50
°C, a linear relationship between Mn and polymerization time
as well as narrow MWD values for all runs (Mw/Mn ) 1.06-
1.19) were found (Figure 5). On the other hand, at 75 °C, long
polymerization time resulted in broad polydispersities, indicating
that chain termination or transfer and/or catalyst deactivation
was not negligible at the temperature (Figure 6). However, the
Mn value of the polymer increased with increase in polymeri-
zation time, and therefore, complex 1/MAO still possessed some
characteristics of living polymerization at 75 °C. Considering
that MAO is a potential chain transfer agent and, thus, normally
living olefin polymerization can only be achieved using a borate
9
3330 J. AM. CHEM. SOC. VOL. 124, NO. 13, 2002

Polymerization of Ethylene Catalyzed by Ti Complexes
A R T I C L E S
Table 4. Results of Ethylene Polymerization with Complexes
2-7/MAOa
entry
complex
polymer yield (g)
TOF (min-1‚atm-1
)
M b (×103)
M /M b
n
w n
1
2
3
4
5
6
2
3
4
5
6
7
0.081
0.069
0.053
0.372
0.267
0.177
1440
492
76
26500
19000
3160
145
64
13
98
129
128
1.25
1.05
1.06
1.99
1.78
2.18
a Conditions: catalyst (0.4 µmol for entries 1, 6; 1.0 µmol for entry 2;
5.0 µmol for entry 3; 0.5 µmol for entries 4, 5), time (5 min for entries 1,
2, 3, 6; 1 min for entries 4, 5), MAO cocatalyst (1.25 mmol), 50 °C, 1 atm,
ethylene feed 100 L/h, 250 mL toluene. b Determined by GPC using
polyethylene calibration.
Figure 5. Plots of Mn and Mw/Mn as a function of polymerization time for
ethylene polymerization with complex 1/MAO at 50 °C.
Figure 7. Plots of Mn and Mw/Mn vs polymerization time with complex
2/MAO (2.0 µmol catalyst, 1.25 mmol MAO, ethylene/N2 10 L/50 L/h, 50
°C).
imine nitrogen, complexes 2-4, display lower activities (TOF:
Figure 6. Plots of Mn and Mw/Mn as a function of polymerization time for
ethylene polymerization with complex 1/MAO at 75 °C.
2, 1440 min-1 atm-1; 3, 492 min-1 atm-1; 4, 76 min-1 atm-1
)
relative to the complexes having the same number of F atoms
with no fluorine adjacent to the imine nitrogen, complexes 5-7
(TOF: 5, 26 500 min-1 atm-1; 6, 19 000 min-1 atm-1; 7, 3160
min-1 atm-1), suggesting that the fluorine adjacent to the imine
nitrogen suppresses polymerization. The catalytic activities
increased with an increase in the number of F atom in the ligand
(TOF, 2 > 3 > 4 and 5 > 6 > 7), being probably ascribed to
the electron-withdrawing nature of fluorine, resulting in a more
electrophilic titanium center.
It is significant to note that the polyethylenes produced by
complexes 2-4 with fluorine atom(s) adjacent to the imine
nitrogen possess narrow polydispersites (Mw/Mn: 2, 1.25; 3,
1.05; 4, 1.06). The polydispersities suggest that the polymeriza-
tions promoted by complexes 2-4 may proceed through a living
mechanism. A linear increase in Mn vs polymerization time
together with the narrow polydispersity for all runs at 50 °C
(Mw/Mn: 2, 1.03-1.10; 3, 1.04-1.18; 4, 1.06-1.08) (Figures
7-9) confirms that the polymerizations exhibited by complexes
2-4 are living.
Alternatively, the polydispersities of the polyethylenes formed
with complexes 5-7 with no fluorine adjacent to the imine
nitrogen are 1.99, 1.78, and 2.18, respectively, being comparable
to the values obtained with common metallocene catalysts.
Therefore, complexes 5-7 did not promote living polymeriza-
tion of ethylene under the conditions employed. The polymer-
ization behavior of complexes 1-7 clearly indicates that the
presence of a F atom adjacent to the imine nitrogen in the ligand
cocatalyst in place of MAO, the living polymerization exhibited
by complex 1/MAO at high temperatures is significant.
Mechanistic Studies on the Living Ethylene Polymeriza-
tion. Because the corresponding nonfluorinated titanium com-
plex (8) does not promote living ethylene polymerization under
similar conditions,18 we postulated that the fluorine atom(s) in
the ligand is responsible for the high-temperature living po-
lymerization. Consequently, we conducted further research on
the catalysis of titanium complexes possessing fluorine-contain-
ing phenoxy-imine chelate ligands in order to investigate the
role of fluorine atom(s). To this end, six titanium complexes
(2-7) having fluorinated ligands were prepared and investigated
for their potential as ethylene polymerization catalysts at 50
°C. A summary of the ethylene polymerization behavior of
complexes 2-7 is shown in Table 4.
Complexes 2-7 are active toward ethylene polymerization
and produce solid polyethylenes. Catalytic activities and poly-
dispersities of the produced polyethylenes are greatly affected
by the number and the location of the fluorine atom(s) in the
ligand. A comparison of the catalytic activities in Table 4
indicates that the complexes having a F atom adjacent to the
(18) As reported in ref 16b, the corresponding nonfluorinated complex 8
produced polyethylene having an Mw/Mn value of ca. 2.0. However, the
complex possesses some characteristics of living ethylene polymerization
for short time at room temperature, though it displays much lower catalytic
performance compared with complex 1.
9
J. AM. CHEM. SOC. VOL. 124, NO. 13, 2002 3331

A R T I C L E S
Mitani et al.
Figure 10. Structure of an active species (C) derived from complex 1
calculated by DFT. tBu groups are omitted for clarity.
Figure 8. Plots of Mn and Mw/Mn vs polymerization time with complex
3/MAO (1.0 µmol catalyst, 1.25 mmol MAO, ethylene 100 L/h, 50 °C).
Scheme 2
Table 5. F-Hâ Interactions Calculated by DFT
Figure 9. Plots of Mn and Mw/Mn vs polymerization time with complex
4/MAO (5.0 µmol catalyst, 1.25 mmol MAO, ethylene 100 L/h, 50 °C).
is a requirement for the high-temperature living polymerization.
IR analyses of the polyethylenes produced by nonliving type
complexes 5-7 reveal a vinyl end group concentration of ca.
0.1 per 1000 carbon atoms, showing that â-hydrogen transfer
is the main termination pathway for the nonliving type
complexes. Therefore, the fluorine adjacent to the imine nitrogen
is thought to suppress the â-hydrogen transfer.19
As reported, DFT calculations are an effective tool for
analyzing the structure of group 4 transition metal complexes
bearing two phenoxy imine chelate ligands.16i Since the
predicted structures for complexes 1 and 3 using DFT calcula-
tions were consistent with those elucidated by the X-ray analyses
(see the Supporting Information), DFT calculations are also
effective in analyzing the structures of titanium complexes
bearing fluorine-containing phenoxy-imine chelate ligands. The
catalytically active species derived from group 4 transition metal
complexes is now widely regarded to be an alkyl cationic
complex20 (Scheme 2), and thus, DFT calculations were
performed on the alkyl cationic complexes derived from
a F-Hâ distance (Å). b Mulliken charge of the nearest o-F to Hâ.
c Mulliken charge of Hâ. d Electrostatic energy for F-Hâ interaction (kJ/
mol).
complexes 1-4 (C, n-propyl; model for polymer chain) to
investigate the role of the fluorine for the living polymerization.
And the structure of an active species (C) derived from complex
1 is shown in Figure 10. The calculation results suggest that
the fluorine adjacent to the imine nitrogen of the active species
for ethylene polymerization interacts with a â-hydrogen of a
polymer chain (F-Hâ distance: 1, 2.276 Å; 2, 2.362 Å; 3, 2.346
Å; 4, 2.324 Å) (Table 5).21 In addition, electrostatic energy
values between the fluorine adjacent to the imine nitrogen and
the â-hydrogen were estimated to be ca. -30 kJ/mol based on
the calculation results, further confirming the interaction between
the fluorine and the â-hydrogen. The interaction between the
(19) DFT calculations suggest that chain transfer to monomer or to Al is sterically
unfavorable for the complexes employed in this study.
(20) (a) Hlatky, G. G.; Turner, H. W.; Eckman, R. R. J. Am. Chem. Soc. 1989,
111, 2728-2729. (b) Jordan, R. F. AdV. Organomet. Chem. 1991, 32, 325-
387. (c) Sishta, C.; Hathorn, R. M.; Marks, T. J. J. Am. Chem. Soc. 1992,
114, 1112-1114. (d) Yang, X.; Stern, C. L.; Marks, T. J. J. Am. Chem.
Soc. 1994, 116, 10015-10031. (e) Bochmann, M. J. Chem. Soc., Dalton
Trans. 1996, 255-270.
(21) The C-H bond length is considerably elongated (1.113 Å) by the strong
interaction between the â-hydrogen and the o-fluorine, though the C-F
bond length is practically the same.
9
3332 J. AM. CHEM. SOC. VOL. 124, NO. 13, 2002

Polymerization of Ethylene Catalyzed by Ti Complexes
A R T I C L E S
Figure 11. Plots of Mn vs polymerization time with complex 1/MAO using the postpolymerization method.
least for 60 min, even in the absence of ethylene, indicating
the high potential of the system for the synthesis of ethylene-
based block copolymers.
Because the known living olefin polymerization catalysts
generally promote the living polymerization of either ethylene
or R-olefins such as propylene and 1-hexene, the preparation
of ethylene-based block copolymers remains a challenge.
Accordingly, we decided to synthesize block copolymers from
ethylene and propylene since, as reported previously, complex
1/MAO promotes the room-temperature living polymerization
of propylene in addition to ethylene to produce highly syndio-
tactic monodisperse polypropylene.6,17a A new A-B diblock
copolymer, polyethylene-b-syndiotactic polypropylene, was
prepared from ethylene and propylene by the sequential
monomer addition (Table 6, entry 1). Thus, ethylene gas (100
L/h) was introduced to toluene in a reactor. After 5 min, the
ethylene gas feed was stopped and the system was kept under
nitrogen atmosphere. Complex 1 and MAO were added to the
reactor to prepare a polyethylene (PE) segment. After 5 min,
the propylene gas feed (30 L/h, 300 min) was initiated to create
a sequential syndiotactic polypropylene (sPP) segment. The
monomodal GPC curves for the PE A block (Mn ) 115 000,
Mw/Mn ) 1.10) and the final PE-b-PP A-B diblock (Mn )
136 000, Mw/Mn ) 1.15) indicate a shift toward higher molecular
weight range while narrow polydispersity is retained, demon-
strating the creation of the desired block copolymer. The block
copolymer possesses a propylene content of 16.1 mol % (from
NMR analysis), the value being in accordance with the increased
molecular weight for the sPP segment. This is probably the first
synthesis of well-defined block copolymer consisting of poly-
ethylene and syndiotactic polypropylene segments with narrow
polydispersity (Mw/Mn < 1.20). In addition, a new A-B diblock
polymer consisting of crystalline and amorphous segments,
polyethylene-b-poly(ethylene-co-propylene), was also synthe-
sized. After preparation of the first PE block segment by the
same procedure, the second monomer, ethylene/propylene gas
feed (25/75 L/h), was started to produce a sequential poly-
(ethylene-co-propylene) segment. The resulting block copolymer
with a high molecular weight (Mn ) 211 000) and narrow
polydispersity (Mw/Mn ) 1.16) contained 6.4 mol % of
propylene.
Figure 12. GPC profile of polyethylenes obtained with the postpolymer-
ization method; polymer (c) and polymer (f).
fluorine and the â-hydrogen probably mitigates the reactivity
of the â-hydrogen toward the titanium metal and/or a coordi-
nated ethylene, resulting in the prevention of â-hydrogen
transfer.22 The interaction may provide a new breakthrough for
achieving high-temperature living ethylene polymerization.
Application of Complex 1/MAO to the Synthesis of Block
Copolymers. First, we investigated the stability of “living”
polymer chain in the absence of reacting monomers, which
affects the application of the catalyst system to the preparation
of block copolymers.
Thus, treatment of complex 1/MAO with ethylene-saturated
toluene at room temperature under nitrogen atmosphere for 65
min (the ethylene was substantially consumed within 3 min as
indicated by Figure 11, entries 2 and 3) and then the ethylene
gas feed (20 L/h, 2 min) to the polymerization system resulted
in the formation of polyethylene having narrow polydispersity
(Mw/Mn ) 1.14) (GPC traces of polymer c and f are shown in
Figure 12). Therefore, there is practically no chain termination
or transfer operative in the complex 1/MAO catalyst system at
(22) Interestingly, a titanium FI Catalyst having a chlorine adjacent to the imine
nitrogen, bis[N-(3-tert-butylsalicylidene)-2-chloroanilinato]titanium(IV) dichlo-
ride, also promoted ethylene polymerization at 25 °C to produce polyeth-
ylene having narrow polydispersity (1.23), implying that the â-hydrogen
fixation is potentially achieved by any substituent possessing lone-pair
electrons.
9
J. AM. CHEM. SOC. VOL. 124, NO. 13, 2002 3333

A R T I C L E S
Mitani et al.
Table 6. Synthesis of Various Block Copolymers
diblock copolymer
triblock copolymer
prepolymer
propyleneb
contents
propyleneb
contents
entry
1st block
M a, M /M a
2nd block
M a, M /M a
3rd block
M a, M /M a
n
w
n
n
w
n
n
w
n
1
2
3
4
PEc
PE
PE
PE
115 000, 1.10
115 000, 1.10
115 000, 1.10
115 000, 1.10
PPd
E/Pe
E/P
E/P
136 000, 1.15
211 000, 1.16
211 000, 1.16
211 000, 1.16
16.1
6.4
6.4
6.4
PP
PE
235 000, 1.15
272 000, 1.14
14.1
6.6
a Determined by GPC using polypropylene calibration. b Total propylene contents (mol %). Determined by NMR. c Polyethylene. d Polypropylene.
e Ethylene-propylene random copolymer.
were determined using a Waters 150-C gel permeation chromatograph
equipped with three TSKgel columns (two sets of TSKgelGMHHR
Likewise, polyethylene-b-poly(ethylene-co-propylene)-b-syn-
diotactic polypropylene (entry 3) and polyethylene-b-poly-
(ethylene-co-propylene)-b-polyethylene23 (entry 4) triblock co-
polymers were also prepared for the first time using the complex
1/MAO catalyst system by the sequential addition of the
monomers. The peak melting temperatures (Tm) of the block
copolymers are 131 °C (entry 1), 123 °C (entry 2), 123 °C (entry
3), and 120 °C (entry 4), the Tm value being lower than the
corresponding homopolyethylene (133 °C) and homopolypro-
pylene (137 °C). Thus, the usefulness of the catalyst system
for the synthesis of a wide array of block copolymers previously
unavailable with Ziegler-Natta type catalysts has been dem-
onstrated. The block copolymers produced by the catalyst system
are anticipated to display novel properties and uses for high-
performance polymers.
-
H(S)HT and TSKgelGMH6-HTL) at 145 °C using polyethylene or
polypropylene calibration. o-Dichlorobenzene was employed as a
solvent at a flow rate of 1.0 mL/min. Transition melting temperatures
(Tm) of the polymers were determined by DSC with a Shimadzu DSC-
60 differential scanning calorimeter, measured upon reheating the
polymer sample to 200 °C at a heating rate of 10 °C/min. Propylene
contents of the copolymers were determined by 13C NMR analyses.
Preparation of Bis[N-(3-tert-butylsalicylidene)-2,3,4,5,6-pentaflu-
oroanilinato]titanium(IV) Dichloride (1). Ligand Synthesis. To a
stirred mixture of 3-tert-butylsalicylaldehyde (7.50 g, 98% purity, 41.2
mmol) and 2,3,4,5,6-pentafluoroaniline (9.06 g, 49.5 mmol) in toluene
(100 mL) was added p-toluenesulfonic acid (ca. 20 mg) at room
temperature. The resulting mixture was stirred at reflux temperature
for 4 h, and concentration of the reaction mixture in vacuo afforded a
crude imine compound. Purification by column chromatography on
silica gel using n-hexane/AcOEt (100/1) as eluent gave N-(3-tert-
butylsalicylidene)-2,3,4,5,6-pentafluoroaniline (a) (13.98 g, 40.7 mmol)
as yellow crystals in 98% yield: 1H NMR (CDCl3) δ 1.46 (s, 9H, tBu),
6.91 (t, J ) 7.8 Hz, 1H, aromatic-H), 7.23-7.26 (m, 1H, aromatic-H),
7.47 (dd, J ) 7.7, 1.5 Hz, 1H, aromatic-H), 8.81 (s, 1H, CHdN), 12.88
(s, 1H, OH).
Experimental Section
General Comments. Syntheses. Ligand syntheses were carried out
under nitrogen in oven-dried glassware. All manipulations of complex
syntheses were performed with exclusion of oxygen and moisture under
argon using standard Schlenk techniques in oven-dried glassware.
Materials. Dried solvents (diethyl ether, dichloromethane, and
n-hexane) used for complex syntheses were purchased from Wako Pure
Chemical Industries, Ltd., and used without further purification. Toluene
used as a polymerization solvent (Wako Pure Chemical Industries, Ltd.)
was dried over Al2O3 and degassed by bubbling with nitrogen gas.
3-tert-Butylsalicylaldehyde and aniline derivatives for ligand synthesis
were obtained from Aldrich Chemical Co., Inc., Wako Pure Chemical
Industries, Ltd., Acros Organics, or Tokyo Kasei Kogyo Co., Ltd. An
n-butyllithium n-hexane solution and dried n-pentane were purchased
from Kanto Chemical Co., Inc. TiCl4 and Cp2ZrCl2 (Wako Pure
Chemical Industries, Ltd.) were used as received. Ethylene and
propylene were obtained from Sumitomo Seika Co. and Mitsui
Chemicals, Inc., respectively. Bis[N-(3-tert-butylsalicylidene)anilinato]-
titanium(IV) dichloride (8) was synthesized according to the previously
described procedure.16b
Complex Synthesis. To a stirred solution of N-(3-tert-butylsali-
cylidene)-2,3,4,5,6-pentafluoroaniline (4.87 g, 14.0 mmol) in dried
diethyl ether (50 mL) at -78 °C was added a 1.52 M n-butyllithium/
n-hexane solution (9.21 mL, 14.0 mmol) dropwise over a 10-min period.
The solution was allowed to warm to room temperature and stirred for
2 h. The resulting solution was added dropwise over a 10-min period
to a 0.5 M n-heptane solution of TiCl4 (14.0 mL, 7.00 mmol) in dried
diethyl ether (50 mL) at -78 °C. The mixture was allowed to warm to
room temperature and stirred for 18 h. Concentration of the reaction
mixture in vacuo gave a crude product. Dried CH2Cl2 (80 mL) was
added to the crude product, and the mixture was stirred for 15 min and
then filtered. The solid residue was washed with dried CH2Cl2 (30 mL
× 3), and the combined organic filtrates were concentrated in vacuo
to afford a brown solid. Diethyl ether (30 mL) and n-hexane (120 mL)
were added to the solid, and the mixture was stirred for 90 min and
then filtered. The resulting solid was washed with n-hexane (20 mL ×
3) and dried in vacuo to give complex 1 (4.03 g, contains 33 mol % of
diethyl ether, 4.86 mmol) as a reddish brown solid in 69% yield.
Cocatalysts. Methylalmoxane (MAO) was purchased from Albe-
marle as a 1.2 M of a toluene solution, and the remaining trimethyl-
aluminum was evaporated in vacuo prior to use.
1
Ligand and Complex Analyses. H NMR spectra were recorded
Compound 1, as reddish brown crystals: 1H NMR (CDCl3) δ 1.35
(s, 18H, tBu), 7.02 (t, J ) 7.6 Hz, 2H, aromatic-H), 7.29 (dd, J ) 7.6,
1.6 Hz, 2H, aromatic-H), 7.64 (dd, J ) 7.6, 1.6 Hz, 2H, aromatic-H),
8.22 (s, 2H, CHdN), 1.21 (t, J ) 7.0 Hz, (CH3CH2)O), 3.48 (q, J )
7.0 Hz, (CH3CH2)O); FD-MS, 802 (M+). Anal. Found: C, 51.71; H,
4.04; N, 3.79. Calcd for TiC34H26N2O2F10Cl2‚1/3Et2O: C, 51.25; H, 3.57;
N, 3.38.
on a JEOL270 or an NEC-LA500 spectrometer at ambient temperatures.
Chemical shifts for H NMR were referenced to an internal solvent
1
resonance and reported relative to tetramethylsilane. FD-MS spectra
were recorded on an SX-102A instrument from Japan Electron Optics
Laboratory Co., Ltd. Elemental analysis for C, H, and N was carried
out by a CHNO type analyzer from Helaus Co.
Polymer Characterization. 13C or 1H NMR data for polyethylenes
and block copolymers were obtained using o-dichlorobenzene with 20%
benzene-d6 as a solvent at 120 °C. Mn and Mw/Mn values of polymers
Preparation of Bis[N-(3-tert-butylsalicylidene)-2,4,6-trifluoro-
anilinato]titanium(IV) Dichloride (2). Ligand b, N-(3-tert-butylsali-
cylidene)-2,4,6-trifluoroaniline, as an orange oil: 1H NMR (CDCl3) δ
(23) Because propylene is present in the polymerization system during the
creation of the third segment, the third segment is actually an ethylene/
propylene random copolymer with low propylene content (ca. 7 mol %).
t
1.47 (s, 9H, Bu), 6.75-6.91 (m, 3H, aromatic-H), 7.23 (dd, J ) 7.6,
1.6 Hz, 1H, aromatic-H), 7.43 (dd, J ) 7.6, 1.6 Hz, 1H, aromatic-H),
9
3334 J. AM. CHEM. SOC. VOL. 124, NO. 13, 2002

Polymerization of Ethylene Catalyzed by Ti Complexes
A R T I C L E S
Table 7. Summary of Crystallographic Data for Complexes 1 and
3
8.83 (s, 1H, CHdN), 13.35 (s, 1H, OH). Compound 2, as dark red
crystals: 1H NMR (CDCl3) δ 1.31 (s, 18H, tBu), 6.26 (bs, 2H, aromatic-
H), 6.65-6.74 (m, 2H, aromatic-H), 6.96 (t, J ) 7.8 Hz, 2H, aromatic-
H), 7.25 (dd, J ) 7.9, 1.6 Hz, 2H, aromatic-H), 7.56 (dd, J ) 7.9, 1.6
Hz, 2H, aromatic-H), 8.18 (s, 2H, CHdN); FD-MS, 730 (M+). Anal.
Found: C, 55.22; H, 4.07; N, 3.71. Calcd for TiC34H30N2O2F6Cl2: C,
55.83; H, 4.13; N, 3.83.
complex
1‚CH Cl2
3‚C H
5 12
2
A. Crystal Data
empircal formula
fw
C35H28Cl4F10N2O2Ti C29H44Cl2F4N2O2Ti
888.31
767.59
crystal color, habit
crystal size (mm)
crystal system
a (Å)
b (Å)
c (Å)
red, platelet
red, platelet
0.40 × 0.35 × 0.07 0.30 × 0.20 × 0.05
Preparation of Bis[N-(3-tert-butylsalicylidene)-2,6-difluoroanili-
nato]titanium(IV) Dichloride (3). Ligand c, N-(3-tert-butylsali-
cylidene)-2,6-difluoroaniline, as orange crystals: 1H NMR (CDCl3) δ
1.47 (s, 9H, tBu), 6.88 (t, J ) 7.6 Hz, 1H, aromatic-H), 6.95-7.16 (m,
3H, aromatic-H), 7.24 (dd, J ) 7.7, 1.4 Hz, 1H, aromatic-H), 7.42
(dd, J ) 7.7, 1.4 Hz, 1H, aromatic-H), 8.86 (s, 1H, CHdN), 13.50 (s,
1H, OH). Compound 3, as brown crystals: 1H NMR (CDCl3), δ 1.26
monoclinic
11.6786(2)
25.6347(9)
12.3467(1)
92.254(4)
3693.5(1)
P21/n (No. 14)
4
monoclinic
18.447(2)
24.188(5)
8.538(1)
91.557(8)
3808.3(10)
P21/n (No. 14)
4
â (deg)
V (Å3)
space group
Z
t
(s, 18H, Bu), 6.44-6.51 (m, 2H, aromatic-H), 6.87-7.02 (m, 6H,
Dcalcd (g/cm)
1.597
1.213
aromatic-H), 7.25 (dd, J ) 7.5, 1.9 Hz, 2H, aromatic-H), 7.50 (dd, J
) 7.5, 1.9 Hz, 2H, aromatic-H), 8.21 (s, 2H, CHdN), 1.21 (t, J ) 7.0
Hz, (CH3CH2)O), 3.48 (q, J ) 7.0 Hz, (CH3CH2)O); FD-MS, 694 (M+).
Anal. Found: C, 58.89; H, 5.33; N, 3.51. Calcd for TiC34H32N2O2F4-
Cl2‚0.8Et2O: C, 59.20; H, 5.34; N, 3.71.
Preparation of Bis[N-(3-tert-butylsalicylidene)-2-fluoroanilinato]-
titanium(IV) Dichloride (4). Ligand d, N-(3-tert-butylsalicylidene)-
2-fluoroaniline, as a yellow oil: 1H NMR (CDCl3) δ 1.47 (s, 9H, tBu),
6.87 (t, J ) 7.8 Hz, 1H, aromatic-H), 7.12-7.30 (m, 5H, aromatic-H),
7.41 (d, J ) 7.6 Hz, 1H, aromatic-H), 8.70 (s, 1H, CHdN), 13.70 (s,
1H, OH). Compound 4, as dark red crystals: 1H NMR (CDCl3), δ
1.31(s, 18H, tBu), 6.70-7.35 (m, 12H, aromatic-H), 7.42 (dd, J ) 7.8,
1.6 Hz, 2H, aromatic-H), 8.12 (s, 2H, CHdN); FD-MS, 658 (M+).
Anal. Found: C, 61.93; H, 5.17; N, 4.09. Calcd for TiC34H34N2O2F2-
Cl2: C, 61.93; H, 5.20; N, 4.25.
F000
1792.00
6.07
1432.00
4.13
µ (Mo KR) (cm-1
)
B. Data Collection
0.71069
λ (Mo KR) (Å)
T (°C)
2θmax
no. of total reflns
0.71069
25.0
55.0
-160.0
59.9
32621
106.36
no. of unique reflns
9925 (Rint ) 0.076) 8740 (Rint ) 0.019)
C. Structure Solution and Refinement
no. observations
no. variables
refln/parameter ratio
residuals: R, Rw
goodness of fit indicator
max shift/error in final cycle 0.001
max peak in final diff
map (e-/Å3)
9917 (I > 3.00σ(I)) 6988 (I > 2.00σ(I))
487
20.36
0.084, 0.073
1.11
451
15.49
0.053, 0.050
0.81
0.11
0.30
0.02
min peak in final diff
max (e-/Å3)
-0.02
-0.37
Preparation of Bis[N-(3-tert-butylsalicylidene)-3,4,5-trifluoro-
anilinato]titanium(IV) Dichloride (5). Ligand e, N-(3-tert-butylsali-
cylidene)-3,4,5-trifluoroaniline, as yellow crystals: 1H NMR (CDCl3)
t
δ 1.46 (s, 9H, Bu), 6.87-6.99 (m, 3H, aromatic-H), 7.43 (d, J ) 7.8
Hz, 1H, aromatic-H), 8.54 (s, 1H, CHdN), 13.19 (bs, 1H, OH).
included but not refined. All calculations were performed using the
teXan25 crystallographic software package of Molecular Structure Corp.
Experimental data for the X-ray diffraction analyses of complexes 1
and 3 are summarized in Table 7.
Compound 5, as dark red crystals: 1H NMR (CDCl3), δ 1.23-1.61
t
(m, 18H, Bu), 6.64-6.69 (m, 4H, aromatic-H), 6.93-7.33 (m, 4H,
aromatic-H), 7.56-7.72 (m, 2H, aromatic-H), 8.03-8.09 (m, 2H, CHd
N); FD-MS, 730 (M+). Anal. Found: C, 55.96; H, 4.00; N, 3.56. Calcd
for TiC34H30N2O2F6Cl2: C, 55.83; H, 4.13; N, 3.83.
DFT Calculations.26 All calculations were performed at the gradient-
corrected density functional BLYP level by means of the Amsterdam
density functional (ADF) program. We used the triple ú STO basis set
for the zirconium and the double ú STO basis set for the other atoms
to calculate the optimized geometries. For Mulliken population analysis,
the triple ú STO basis set for the zirconium and the double ú plus
polarization STO basis set for the other atoms were used, and the
quasirelativistic correction was also added. The classical electrostatic
energies between the â-hydrogen and the nearest neighboring fluorine
were estimated by the following equation:
Preparation of Bis[N-(3-tert-butylsalicylidene)-3,5-difluoroanili-
nato]titanium(IV) Dichloride (6). Ligand f, N-(3-tert-butylsalicylidene)-
3,5-difluoroaniline, as a yellow oil: 1H NMR (CDCl3) δ 1.46 (s, 9H,
tBu), 6.67-7.44 (m, 6H, aromatic-H), 8.56 (s, 1H, CHdN), 13.30 (s,
1H, OH). Compound 6, as dark red crystals: 1H NMR (CDCl3), δ
t
1.32-1.62 (m, 18H, Bu), 6.33-7.33 (m, 10H, aromatic-H), 7.52-
7.70 (m, 2H, aromatic-H), 8.03-8.10 (m, 2H, CHdN); FD-MS, 694
(M+). Anal. Found: C, 58.83; H, 4.91; N, 3.78. Calcd for TiC34H32N2O2-
F4Cl2: C, 58.72; H, 4.64; N, 4.03.
Preparation of Bis[N-(3-tert-butylsalicylidene)-4-fluoroanilinato]-
titanium(IV) Dichloride (7). Ligand g, N-(3-tert-butylsalicylidene)-
4-fluoroaniline, as an orange oil: 1H NMR (CDCl3) δ 1.47 (s, 9H,
tBu), 6.88 (t, J ) 7.6 Hz, 1H, aromatic-H), 7.04-7.41 (m, 6H, aromatic-
H), 8.59 (s, 1H, CHdN), 13.76 (s, 1H, OH). (7); as brown crystals:
ES ) q(Hâ)q(F)/r(F-Hâ)
Here q(Hâ) and q(F) stand for Mulliken charges of the â-hydrogen and
the nearest neighboring fluorine, respectively, and r(F-Hâ) is the
distance between those two atoms. All units are in atomic unit.
Ethylene Polymerization. General Procedure. Ethylene polym-
erization was carried out under atmospheric pressure in toluene in a
t
1H NMR (CDCl3), δ 1.07-1.61 (m, 18H, Bu), 6.71-7.67 (m, 14H,
aromatic-H), 7.96-8.13 (m, 2H, CHdN); FD-MS, 658 (M+). Anal.
Found: C, 62.04; H, 5.30; N, 3.77. Calcd for TiC34H34N2O2F2Cl2: C,
61.93; H, 5.20; N, 4.25.
(24) Complex 1, SIR97: Altomale, A.; Burla, M. C.; Camalli, M.; Cascarano,
M.; Giacovazzo, C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.;
Spagna, R. J. Appl. Cryst., 1999, 32, 115-119. Complex 3, SIR92:
Altomale, A.; Burla, M. C.; Camalli, M.; Cascarano, M.; Giacovazzo, C.;
Guagliardi, A.; Polidori, G. J. Appl. Cryst. 1994, 27, 435-436.
(25) TeXan: Crystal Structure Analysis Package, Molecular Structure Corp.
(1985 & 1992).
(26) (a) Fonseca Guerra, C.; Snijders, J. G.; te Velde, G., Baerends, E. J. Theor.
Chem. Acc. 1998, 99, 391-403. (b) Deng, L.; Ziegler, T.; Woo, T. K.;
Margl, P.; Fan, L. Organometallics 1998, 17, 3240-3253. (c) R. S.
Mulliken, J. Chem. Phys. 1955, 23, 1833.
X-ray Crystallography. Single crystals of complexes 1 and 3
suitable for an X-ray analysis were grown from a saturated pentane/
CH2Cl2 solution. The X-ray structure analyses data were collected using
a Rigaku RAXIS-RAPID imaging plate diffractometer (complex 1) or
a Rigaku AFC7R diffractometer (complex 3). The structure was solved
by direct method24 and expanded using Fourier techniques. The non-
hydrogen atoms were refined anisotropically. Hydrogen atoms were
9
J. AM. CHEM. SOC. VOL. 124, NO. 13, 2002 3335

A R T I C L E S
Mitani et al.
500-mL glass reactor equipped with a propeller-like stirrer. Toluene
(250 mL) was introduced into the nitrogen-purged reactor and stirred
(600 rpm). The toluene was thermostated to a prescribed polymerization
temperature, and then the ethylene gas feed (100 L/h) was started. After
10 min, polymerization was initiated by adding a toluene solution of
MAO (1.0 M. 1.25 mL) and then a toluene solution of a complex into
the reactor with stirring (600 rpm). After a prescribed time, sec-butyl
alcohol (10 mL) was added to terminate the polymerization. To the
resulting mixture, methanol (250 mL) and concentrated HCl (2 mL)
were added. The polymer was collected by filtration, washed with
methanol (200 mL), and dried in vacuo at 80 °C for 10 h.
Polymerization Using Diluted Ethylene with N2 (Table 3 and
Figure 7). Polymerization using diluted ethylene with N2 was performed
by using ethylene-N2 mixed gas in place of ethylene gas [complex 1:
ethylene/N2 feed 2 L/50 L/h (25, 50 °C), 5 L/50 L/h (75 °C) (Table 3)]
[complex 2: ethylene, 10 L/h; N2, 50 L/h (Figure 7)] using the same
type of equipment and the same manner for the general procedure
described above, except for stirring (400 rpm).
Postpolymerization Method (Figure 11). The postpolymerization
method was carried out using the same type equipment under
atmospheric pressure. Toluene (250 mL) was introduced into the
nitrogen-purged reactor and stirred (300 rpm). The toluene was kept
at 25 °C, and then the ethylene gas feed (100 L/h) was started. After
5 min, the ethylene gas feed was stopped and the toluene solution was
kept under N2. To the resulting toluene solution were added toluene
solutions of MAO (1.0 M, 2.5 mL) and complex 1 (2 mM, 5.0 mL) to
start ethylene polymerization.
PE-E/P-PP Triblock Copolymer (Table 6, Entry 3). After the
preparation of the polyethylene-b-poly(ethylene-co-propylene) segment
using the same method for the preparation of PE-E/P diblock
copolymer, the propylene gas feed (30 L/h) was initiated. After 20 min,
the propylene gas feed was stopped, and the mixture was stirred for
280 min to create the sequential polypropylene (PP) segment. sec-Butyl
alcohol (10 mL) was added to terminate the polymerization. The
resulting mixture was added to acidic methanol (1000 mL) including
concentrated HCl (2 mL). The polymer was collected by filtration,
washed with methanol (200 mL), and dried in vacuo at 130 °C for 10
h.
PE-E/P-PE Triblock Copolymer (Table 6, Entry 4). After the
preparation of the polyethylene-b-poly(ethylene-co-propylene) segment
using the same method for the preparation of PE-E/P diblock copolymer,
the ethylene gas feed (100 L/h) was initiated to create the sequential
polyethylene (PE) segment. After 1 min, sec-butyl alcohol (10 mL)
was added to terminate the polymerization. The resulting mixture was
added to acidic methanol (1000 mL) including concentrated HCl (2
mL). The polymer was collected by filtration, washed with methanol
(200 mL), and dried in vacuo at 130 °C for 10 h.
Conclusion
In conclusion, we have developed a new series of titanium
complexes having fluorine-containing phenoxy-imine chelate
ligands, some titanium FI Catalysts, which are effective catalysts
for the living polymerization of ethylene using MAO as a
cocatalyst. The catalyst systems display very high activities
(TOF value > 20 000 min-1 atm-1) and create high molecular
weight polyethylenes (Mn > 400 000) with extremely narrow
polydispersities (Mw/Mn < 1.20) at very high polymerization
temperatures (25-50 °C). DFT calculations suggest that the
fluorine adjacent to the imine nitrogen of an active species, for
ethylene polymerization, interacts with a â-hydrogen of a
polymer chain to prevent the â-hydrogen transfer, an interaction
providing a new breakthrough for accomplishing high-temper-
ature living ethylene polymerization. Using the FI Catalyst
possessing N-(3-tert-butylsalicylidene)pentafluoroaniline ligands/
MAO system, a number of new block copolymers such as
polyethylene-b-poly(ethylene-co-propylene)-b-syndiotactic poly-
propylene triblock copolymer have been successfully prepared.
The results introduced herein together with our previous results
show that group 4 transition metal complexes having phenoxy-
imine chelate ligands, FI Catalysts, possess high potential for
olefin polymerization, resulting in novel polymers that are
anticipated to exhibit new properties and uses.
Entries 1-5. After a prescribed time, sec-butyl alcohol (10 mL)
was added to terminate the polymerization. Polymer purification and
isolation were performed using the same method as the general
procedure.
Entry 6. After 65 min, the ethylene gas feed (20 L/h) was initiated
to perform postpolymerization. After 2 min, sec-butyl alcohol (10 mL)
was added to terminate the polymerization. Polymer purification and
isolation were performed using the same method as described in the
general procedure.
Synthetic Procedure for Block Copolymers. Block copolymers
were synthesized using the same type of equipment under atmospheric
pressure.
PE-PP Diblock Copolymer (Table 6, Entry 1). Toluene (250 mL)
was introduced into the nitrogen-purged reactor and stirred (300 rpm).
The toluene was kept at 25 °C, and then the ethylene gas feed (100
L/h) was started. After 5 min, the ethylene gas feed was stopped and
the toluene solution was kept under N2 for 5 min. To the resulting
toluene solution were added toluene solutions of MAO (1.0 M, 2.5
mL) and complex 1 (2 mM, 5.0 mL) to produce the polyethylene (PE)
segment. After 5 min, the propylene gas feed (30 L/h) was initiated.
After 20 min, the propylene gas feed was stopped, and the mixture
was stirred for 280 min to create the sequential polypropylene (PP)
segment. sec-Butyl alcohol (10 mL) was added to terminate the
polymerization. The resulting mixture was added to acidic methanol
(1000 mL), including concentrated HCl (2 mL). The polymer was
collected by filtration, washed with methanol (200 mL), and dried in
vacuo at 80 °C for 10 h.
PE-E/P Diblock Copolymer (Table 6, Entry 2). After the
preparation of the polyethylene segment using the same method for
the preparation of the polyethylene segment for PE-PP diblock
copolymer, the ethylene/propylene mixed gas feed (ethylene 25 L/h,
propylene 75 L/h) was initiated. After 3 min, the ethylene/propylene
mixed gas feed was stopped, and the mixture was stirred for 3 min to
create the sequential ethylene/propylene random copolymer (E/P)
segment. sec-Butyl alcohol (10 mL) was added to terminate the
polymerization. The resulting mixture was added to acidic methanol
(1000 mL) including concentrated HCl (2 mL). The polymer was
collected by filtration, washed with methanol (200 mL), and dried in
vacuo at 130 °C for 10 h.
Acknowledgment. We would like to thank Dr. M. Mullins
for his fruitful discussions and suggestions. We are also grateful
to Y. Suzuki, N. Matsukawa, S. Matsuura, T. Hayashi, M.
Nitabaru, Y. Inoue, Y. Takagi, Y. Nakayama, H. Bando, H.
Terao, Y. Tohi, H. Makio, and J. S. Harp for their research and
technical assistance. We would also like to thank M. Onda for
NMR analysis, K. Shiozawa for X-ray analysis, and T. Abiru
for GPC analysis.
Supporting Information Available: Full crystallographic data
and DFT calculation for complexes 1 and 3, detailed synthesis
data for complexes 2-7, and 13C NMR spectrum and GPC and
DSC charts of the polymers.This material is available free of
charge via the Internet at http://pubs.acs.org.
JA0117581
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3336 J. AM. CHEM. SOC. VOL. 124, NO. 13, 2002