New titanium complexes bearing two indolide-imine chelate ligands for the polymerization of ethylene

Article abstract of DOI:10.1021/ma0122268

New titanium complexes 5-8 with two indolide-imine chelate ligands [7-(RN=CH)C₈H₅N]₂TiCl₂ (R: 5, phenyl; 6, 2,6-difluorophenyl; 7, 2,4,6-trifluorophenyl; 8, pentafluorophenyl) were synthesized and investigated as ethylene polymerization catalysts. On activation with methylalumoxane (MAO), all of the complexes were active ethylene polymerization catalysts at 25 °C to produce linear polyethylenes. The catalytic activity (TOF) increased sharply with the number of fluorine atom in the ligand. In addition, complexes 5-8 potentially exhibit the characteristics of a living ethylene polymerization. Complexes 6 and 7 promoted room temperature living ethylene polymerization to produce polyethylenes having extremely narrow molecular weight distributions (6, M_w/M_n 1.09-1.14; 7, M_w/M_n 1.05-1.23). On the other hand, at -10 °C complex 8 afforded monodisperse polyethylenes (M_wM_n 1.12-1.25), with exceptionally high activities for a living ethylene polymerization (TOF: maximum 1155 min^-1 atm^-1). Using complex 7/MAO catalyst system, a polyethylene-b-poly(ethylene-co-propylene) block copolymer was successfully synthesized.

Full text of DOI:10.1021/ma0122268

4880
Macromolecules 2002, 35, 4880-4887
New Titanium Complexes Bearing Two Indolide-Imine Chelate
Ligands for the Polymerization of Ethylene
Tom oa k i Ma tsu gi, Sh igek a zu Ma tsu i, Sh in -ich i Kojoh , Yu k ih ir o Ta k a gi,
Yosh ih isa In ou e, Ta k a sh i Na k a n o, Ter u n or i F u jita ,* a n d Nor io Ka sh iw a
R&D Center, Mitsui Chemicals, Inc., 580-32 Nagaura, Sodegaura-City, Chiba 299-0265, J apan
Received December 21, 2001; Revised Manuscript Received March 25, 2002
ABSTRACT: New titanium complexes 5-8 with two indolide-imine chelate ligands [7-(RNdCH)C8H5N]2-
TiCl2 (R: 5, phenyl; 6, 2,6-difluorophenyl; 7, 2,4,6-trifluorophenyl; 8, pentafluorophenyl) were synthesized
and investigated as ethylene polymerization catalysts. On activation with methylalumoxane (MAO), all
of the complexes were active ethylene polymerization catalysts at 25 °C to produce linear polyethylenes.
The catalytic activity (TOF) increased sharply with the number of fluorine atom in the ligand. In addition,
complexes 5-8 potentially exhibit the characteristics of a living ethylene polymerization. Complexes 6
and 7 promoted room temperature living ethylene polymerization to produce polyethylenes having
extremely narrow molecular weight distributions (6, Mw/Mn 1.09-1.14; 7, Mw/Mn 1.05-1.23). On the other
hand, at -10 °C complex 8 afforded monodisperse polyethylenes (Mw/Mn 1.12-1.25), with exceptionally
high activities for a living ethylene polymerization (TOF: maximum 1155 min-1 atm-1). Using complex
7/MAO catalyst system, a polyethylene-b-poly(ethylene-co-propylene) block copolymer was successfully
synthesized.
In tr od u ction
bidentate ligands26 [e.g., phenoxy-imine,27,28 pyrrolide-
imine,29 imine-pyridine,27e and phenoxy-pyridine30
ligands], which exhibit high catalytic performance for
olefin polymerization including living olefin polymeri-
zation.27h-j,l,n,29c Further investigation along this re-
search line has led to the discovery of titanium com-
plexes bearing unsymmetrical bidentate indolide-imine
chelate ligands, which display high ethylene polymer-
ization activities and, moreover, can promote living
ethylene polymerization to produce polyethylenes with
extremely narrow molecular weight distributions.31
Therefore, in this article, we describe the synthesis and
ethylene polymerization behavior of a series of titanium
complexes having two indolide-imine chelate ligands.
In addition, we introduce the preparation of a polyeth-
ylene-b-poly(ethylene-co-propylene) block copolymer,
and its evaluation results using transmission electron
microscopy (TEM).
During the past two decades, studies on single-site
catalysts for olefin polymerization have been actively
pursued in both academic and industrial research
groups.1-9 This is because single-site catalysts possess
well-defined structures and, thus, provide a better
opportunity for rational catalyst design than the het-
erogeneous Ziegler-Natta catalysts. The vast majority
of the catalysts investigated are group 4 metallocene
derivatives though some are known to involve one
cyclopentadienyl (Cp) ligand. Therefore, recently, tran-
sition metal complexes with no Cp ligand(s) have
received increased attention as potentially viable olefin
polymerization catalysts. Recent progress in the rational
design of well-defined transition metal complexes has
resulted in the introduction of quite a few high-
performance olefin polymerization catalysts, other than
group 4 metallocene catalysts, based on both early and
late transition metal complexes. Examples of high-
performance catalysts feature chelating ligands such as
diimine ligand (with Ni and Pd),10 phenoxy-imine
ligand (with Ni),11 diimine-pyridine ligand (with Fe and
Co),12 amino-tropone ligand (with Ni),13 diamide ligand
(with Ti),14 diamide-ether ligand (with Ti, Zr, Hf),15
phosphine-imide ligand (with Ti),16 pyrrolide-imine
ligand (with Cr and Zr),17 tris(pyrazolyl)borate ligand
(with Ti),18 bisphenoxy-amine ligand (with Zr),19 and
amide-pyridine ligand (with Ta).20 Many of the com-
plexes show activities comparable to those of group 4
metallocene catalysts and in some cases promote copo-
lymerization of ethylene or R-olefins with polar olefins
to produce functionalized polyolefins.10b,11b In addition,
some function as living olefin polymerization catalysts
to provide a variety of monodisperse polymers including
polyolefinic block copolymers.10c,14b,15a,19b,21-25 Conse-
quently, the development of high-performance olefin
polymerization catalysts has been achieved at a rapid
pace.
Resu lts a n d Discu ssion
A general preparation route for titanium complexes
utilized in this work is shown in Scheme 1. 7-Formylin-
dole was synthesized according to the literature.32
The indolide-imine ligands 1-4, 7-(N-arylimino-
methyl)indole, are prepared in high yields (1, 98%; 2,
64%; 3, 72%; 4, 70%) from the condensation of the
appropriate aniline compound with 7-formylindole in
toluene using acetic acid or p-toluenesulfonic acid as a
catalyst. The titanium complexes 5-8 possessing two
indolide-imine ligands, bis[7-(N-aryliminomethyl)in-
dolinyl]titanium(IV) dichloride, are synthesized in mod-
erate yields (5, 36%; 6, 27%; 7, 29%; 8, 47%) in diethyl
ether or toluene by treating TiCl4 with 2 equiv of the
lithium salt of the indolide-imine ligand.
The 1H NMR spectra of titanium complexes 5-8
exhibit a single sharp peak assigned to the methine
proton (-CdN-H) of the indolide-imine chelate ligand,
being consistent with a six-coordinate octahedral struc-
ture. The titanium complexes could exhibit five idealized
octahedral isomeric structures A-E (Scheme 2) because
Previously, in our laboratories, we have developed
transition metal complexes featuring unsymmetrical
10.1021/ma0122268 CCC: $22.00 © 2002 American Chemical Society
Published on Web 05/25/2002

Macromolecules, Vol. 35, No. 13, 2002
New Titanium Complexes 4881
Sch em e 1
Sch em e 2
F igu r e 1. Calculated structure of ethylene coordinated active
species generated from complex 5.
Ta ble 1. Eth ylen e P olym er iza tion Resu lts Usin g
Com p lexes 5-8a
c
yield
(g)
TOFb (min-1
Mw
c
entry
complex
atm-1
)
(10-4
)
Mw/ Mn
1
2
3
4
5
6
7
8
0.043
0.050
0.240
0.951
31
36
171
677
1.38
1.24
4.65
1.14
1.13
1.11
1.93
they possess two unsymmetrical bidentate ligands.
Thus, the complexes potentially have more than one
active species for olefin polymerization.
32.3
a
Conditions: 25 °C, 0.1 MPa pressure, polymerization time; 10
min, ethylene 100 L/h, complex; 5.0 µmol; cocatalyst MAO (Al) 1.25
Since, as reported,27e,29 DFT calculations are an
effective tool for analyzing the structures of group 4
transition metal complexes, DFT calculations were
performed on a methyl cationic complex, an initial active
species generated from complex 5 with MAO for ethyl-
ene polymerization, to obtain information on the struc-
ture of an active species. The cationic complex was
suggested to possess a distorted octahedral coordination
structure around the titanium metal, an isomer-A-type
structure, in which a methyl group and a coordinated
ethylene are situated at an angle of 63.9° (Figure 1),
showing that for ethylene polymerization the cationic
complex has a pair of available cis-located sites, which
are trans to the imine nitrogens in the ligand. Likewise,
the calculations indicated that the methyl cationic
complexes originated from complexes 6-8 also adopt an
isomer-A-type structure (methyl-Ti-coordinated ethyl-
ene angle; 6, 70.4°; 7, 71.2°; 8, 74.4°). Therefore,
complexes 5-8 were suggested to possess two available
cis-located sites, a prerequisite for efficient olefin po-
lymerization, and at the same time, the same stereo-
chemical relationship between the active sites and the
imine nitrogens as the previously reported group 4
transition metal complexes with phenoxy-imine or
pyrrolide-imine chelate ligands, which display high
ethylene polymerization activities.
E t h ylen e P olym er iza t ion Beh a vior of Com -
p lexes 5-8/MAO Ca ta lyst System s. Complexes 5-8
were investigated for their potential as ethylene polym-
erization catalysts at 25 °C under atmospheric pressure
using methylalumoxane (MAO) as a cocatalyst. The
results are summarized in Table 1. All of the complexes
are active ethylene polymerization catalysts to produce
crystalline polyethylenes. The activities (TOF) obtained
were in the range of 31-677 min-1 atm-1. The basic
trend observed regarding catalytic activity is that
increase in the number of fluorine atoms in the ligand
resulted in enhanced catalytic activity (e.g., complex 8
is over 20 times more active than the corresponding
b
mmol, solvent; toluene 250 mL. TOF: [polymer yield (g)]/28.05/
[complex (mol)]/[polymerization time (min)]. c Mw, Mn values; GPC
analysis.
nonfluorinated complex 5). These results provide a clear
demonstration that the electrophilicity of the titanium
center in active species plays a dominant role in
determining the catalytic activity, unlike the group 4
metallocene catalysts whose activity is decreased by the
introduction of electron-withdrawing substituent(s) in
Cp ligand.33,34 An explanation for the activity enhance-
ment resulting from the introduction of electron-
withdrawing fluorine atom(s) in the ligand is that a
more electrophilic titanium center, generated by a more
electron-withdrawing ligand, results in increase metal-
carbon reactivity, leading to reduced activation energy
for ethylene insertion. The activity, TOF 677 min-1
atm-1, exhibited by complex 8 is very high for a titanium
complex with no Cp ligand(s) and is comparable to
that displayed by the highly active titanium complex
with two phosphinimide ligands reported by Stephan
et al.16 (TOF 693 min-1 atm-1, 25 °C, atmospheric
pressure).
Complexes 5-8 provided polyethylenes having mod-
erate to high molecular weight values (Mw 13 800-
323 000). The polyethylenes exhibit the peak melting
temperature (Tm) in the range 132.2-134.2 °C. 13C NMR
analyses indicate that the polyethylenes possess linear
structures with virtually no branching. Analyses of the
polyethylene end groups by 13C NMR as well as IR show
that the polyethylenes are essentially saturated, indi-
cating that â-hydride elimination is negligible as a chain
termination process concerning complexes 5-8/MAO
catalyst systems. GPC analyses of the polymers revealed
that the polyethylenes produced by complexes 5-7
possess extremely narrow molecular weight distribu-
tions (Mw/Mn 1.11-1.14) whereas that formed with
complex 8 has an Mw/Mn value of 1.93. The Mw/Mn
values suggest that complexes 5-7/MAO catalyst sys-

4882 Matsugi et al.
Macromolecules, Vol. 35, No. 13, 2002
F igu r e 4. Plot of polymer yield as a function of polymerization
time for the polymerization of ethylene using complex 6/MAO
(25 °C).
F igu r e 2. Plot of polymer yield as a function of polymerization
time for the polymerization of ethylene using complex 5/MAO
(25 °C).
F igu r e 5. Plot of Mn and Mw/Mn as a function of polymer
yield for the polymerization of ethylene using complex 6/MAO
(25 °C).
F igu r e 3. Plot of Mn and Mw/Mn as a function of polymer
yield for the polymerization of ethylene using complex 5/MAO
(25 °C).
time, indicating that the catalyst deactivation was
negligible under the conditions employed. The plots of
Mn and Mw/Mn vs polymer yield are shown in Figure 5.
A linear relationship between Mn and the polymer yield
as well as narrow Mw/Mn values for all runs (Mw/Mn
1.05-1.23) were found (Figure 5). Likewise, linear
relationships vis-a`-vis the polymer yield vs polymeri-
zation time and Mn and Mw/Mn values vs polymer yield
were found for complex 7/MAO catalyst system (see the
Supporting Information). These results indicate that
complexes 6 and 7/MAO catalyst systems promote the
living polymerization of ethylene at 25 °C. These are
rare examples of room temperature living ethylene
polymerizations. Considering that the MAO used as the
cocatalyst is a potential chain transfer agent, the room
temperature living ethylene polymerizations exhibited
by complexes 6 and 7 are highly significant. The
activities, TOF 124-188 min-1 atm-1, displayed by
complex 7 are very high for a polymerization proceeding
in a living fashion. As listed in Table 2, at 50 °C complex
7 was capable of producing polyethylene having reason-
ably narrow molecular weight distribution (Mw/Mn 1.24)
though at 75 °C the complex furnished polyethylene
with broad molecular weight distribution (Mw/Mn 15.9)
probably due to considerable catalyst deactivation.
tems may have the characteristics of a living ethylene
polymerization under the given conditions despite the
use of MAO, a potential chain transfer agent, as the
cocatalyst.
Deta iled Stu d y on Eth ylen e P olym er iza tion Be-
h a vior of Com p lexes 5-8/MAO. Ethylene polymer-
izations using complex 5-8/MAO were further investi-
gated to elucidate the catalytic performance of complexes
5-8/MAO catalyst systems.
Com p lex 5/MAO Ca ta lyst System . The polymer
yield-polymerization time and Mn and Mw/Mn values-
polymer yield relationships were plotted for the polym-
erization with complex 5/MAO catalyst system at 25 °C
under ethylene at atmospheric pressure (Figures 2 and
3). As shown in Figure 2, an increase of polymer yield
against polymerization time showed gradual saturation
behavior despite the sufficiently low polymer yields and
Mn values of the polyethylenes, indicating that some
catalyst deactivation occurred during the polymeriza-
tion. However, the Mn value increased proportionally
with the polymer yield, and the narrow Mw/Mn value
was retained during the course of the polymerization
(Figure 3). These results suggest that complex 5/MAO
catalyst system possesses the considerable character-
istics of living ethylene polymerization at room temper-
ature though some catalyst deactivation is observed
under the given conditions.
Com p lex 8/MAO Ca ta lyst System . The plot of
polymer yield vs polymerization time and the plot of
Mn and Mw/Mn vs polymer yield are shown in Figures 6
and 7.
Although an increase of polymer yield vs the polym-
erization time and that of Mn vs polymer yield showed
gradual saturation behavior, the produced polymer
Com p lexes 6 a n d 7/MAO Ca ta lyst System s. Fig-
ure 4 shows the plot of polymer yield as a function of
polymerization time with respect to the polymerization
of ethylene using complex 6/MAO catalyst system. The
polymer yield increased linearly with the polymerization

Macromolecules, Vol. 35, No. 13, 2002
New Titanium Complexes 4883
Ta ble 2. Eth ylen e P olym er iza tion Resu lts w ith Com p lex
7/MAO Ca ta lyst System a
Ta ble 3. Effects of MAO or H2 on Eth ylen e
P olym er iza tion Beh a vior of Com p lex 8/MAO Ca ta lyst
System a
c
temp
(°C)
yield
(g)
TOFb (min-1
Mw
c
entry
atm-1
)
(10-4
)
Mw/ Mn
H2
TOFb
c
MAO
entry (mmol) (L/h)
feed yield (min-1
Mw
1
2
3
25
50
75
0.240
0.242
0.063
171
173
44.9
4.65
6.61
31.2
1.11
1.24
15.9
atm-1
)
(10-4
)
Mw/Mn
[N]d
c
(g)
1
2
3
4
5
6
7
0.5
1.25
2.5
5.0
12.5
0
0
0
0
0
0.41
0.79
0.97
1.19
1.42
0.64
0.50
290
563
689
848
1013
459
358
40.0
40.2
42.0
40.5
43.8
3.06
2.84
2.29
2.09
1.97
1.79
2.04
0.62
1.12
1.05
1.23
1.28
11.7
16.5
a
Conditions: 0.1 MPa pressure, polymerization time; 10 min,
ethylene 100 L/h, complex 7; 5.0 µmol; cocatalyst MAO (Al) 1.25
b
mmol, solvent; toluene 250 mL. TOF: [polymer yield (g)]/28.05/
[complex (mol)]/[polymerization time (min)]. c Mw, Mn values; GPC
2.5
2.5
5
10
1.96
1.25
analysis.
a
Conditions: 25 °C, 0.1 MPa pressure, polymerization time; 10
min, toluene; 250 mL, ethylene; 100 L/h, complex 8; 5.0 µmol.
b
TOF: [polymer yield (g)]/28.05/[complex (mol)]/[polymerization
time (min)]. c Mw, Mn values; GPC analysis. [N] ) number of
polymer chains (mol [PE]/mol [cat.]).
d
F igu r e 6. Plot of polymer yield as a function of polymerization
time for the polymerization of ethylene using complex 8/MAO
(25 °C).
F igu r e 8. Plot of polymer yield as a function of polymerization
time for the polymerization of ethylene using complex 8/MAO
(-10 °C).
F igu r e 7. Plot of Mn and Mw/Mn as a function of polymer
yield for the polymerization of ethylene using complex 8/MAO
(25 °C).
chain number, calculated from the polymer yield and
Mn value, suggested that each molecule of catalyst
makes approximately one polymer chain. IR analyses
showed that the polyethylenes formed with complex 8
possess essentially saturated end groups. In addition,
changing the Al/Ti ratio gave rise to practically no
changes in molecular weight. These results show that
the polymerization process is not only devoid of chain
termination via â-hydride elimination, but also it pro-
ceeds without chain transfer to the aluminum cocatalyst
though some catalyst deactivation may be involved in
the process. The increase in Mw/Mn value during the
course of polymerization results mainly from the inho-
mogeneity of the polymerization system because of high
molecular weight and insoluble polymers. As listed in
Table 3, hydrogen works as an effective chain transfer
agent in the polymerization of ethylene with complex 8
to give lower molecular weight polyethylenes with
increased number of polymer chains per catalyst mol-
ecule.
F igu r e 9. Plot of Mn and Mw/Mn as a function of polymer
yield for the polymerization of ethylene using complex 8/MAO
(-10 °C).
Ethylene polymerizations using complex 8/MAO were
carried out at a lower temperature of -10 °C and at a
lower catalyst concentration. The polymer yield-po-
lymerization time and Mn and Mw/Mn values-polymer
yield relationships are plotted (Figures 8 and 9).
The Mn value increased proportionally with the po-
lymerization time, and at the same time, the narrow
Mw/Mn value was retained during the polymerization
(Mw/Mn 1.12-1.25), indicating that complex 8/MAO
promotes living ethylene polymerization at -10 °C. It
is noteworthy that the activities exhibited by complex
8/MAO, TOF 979-1155 min-1 atm-1, are 2 orders of
magnitude greater than those obtained with common
living ethylene polymerization systems (TOF ca. 20

4884 Matsugi et al.
Macromolecules, Vol. 35, No. 13, 2002
Ta ble 4. P r ep a r a tion of P E-b-p oly(eth ylen e-co-p r op ylen e)
a n d Its Segm en tsa
a
time
yield
(g)
Mn
Pb
(mol %)
a
entry (min) monomer
(10-4
)
Mw/ Mn
1c
2
3
5-50
5
50
E to E/P
E
E/P
0.45
0.16
0.38
3.14
1.52
2.41
1.17
1.05
1.22
8.0
0
19.5
a
Conditions: 2.0 °C, 0.1 MPa pressure, complex 7; 10 µmol,
MAO(Al) 2.50 mmol (Al). Toluene (250 mL) saturated with
b
ethylene employed as a solvent. Mw, Mn values; GPC analysis.
c Total propylene contents in the resulting polymers; IR analysis.
d
After ethylene (100 L/h, 5 min) polymerization, the feeding gas
was changed from ethylene to mixed gas (ethylene/propylene )
30/70 L/h, 50 min).
F igu r e 10. GPC traces of the polymers: (a) polyethylene
(Table 4, entry 2); (b) PE-b-poly(ethylene-co-propylene) (Table
4, entry 1).
F igu r e 11. TEM micrographs of (A) PE-b-poly(ethylene-co-
propylene) and (B) polyethylene and poly(ethylene-co-propy-
lene) blend polymer (blend conditions; toluene, reflux temper-
ature, 1 h).
min-1 atm-1). Moreover, these activities represent some
of the highest activities reported to date for titanium-
based ethylene polymerization catalysts with no Cp
ligands at atmospheric pressure conditions.
molecular-weight region (Figure 10), demonstrating the
creation of the target block copolymer. The poly(ethylene-
co-propylene) segment of the block copolymer is esti-
mated to contain 19.5 mol % of propylene, based on the
control experiment (Table 4, entry 3). The peak melting
temperature (Tm) of the resulting block polymer and the
corresponding PE homopolymer were determined from
DSC measurements. The PE-b-poly(ethylene-co-propy-
lene) displays a lower Tm, 126.8 °C, relative to that of
the PE homopolymer (134.1 °C, entry 2). The decrease
in Tm vis-a`-vis the block copolymer is probably due to
the fact that the crystalline state is disturbed by the
segregation process of incompatible components consist-
ing of crystalline PE and amorphous poly(ethylene-co-
propylene) segments which are chemically linked, fur-
ther confirming the formation of the block copolymer.
This is a rare example of the synthesis of ethylene-based
polyolefinic block copolymer consisting of crystalline and
amorphous segments.27h,i Further information on the
properties of the block copolymer is provided by trans-
mission electron microscopy (TEM). TEM was applied
to study the morphology difference between the PE-b-
poly(ethylene-co-propylene) and the corresponding PE/
poly(ethylene-co-propylene) blend polymer (blend con-
ditions; toluene, reflux temperature, 1 h). The TEM
image of the block copolymer is quite different from that
of the blend polymer as can be seen in Figure 11. Thus,
the TEM micrograph of the press sheet made of the
block copolymer shows well-defined morphology of mi-
crophase separation. In Figure 11A, white domains
corresponding to the PE segment form a fine nanostruc-
ture, whereas those for the blend polymer (Figure 11B)
display the grown lamellar structures of PE, and the
poly(ethylene-co-propylene) exists among the PE lamel-
lar structures. These results indicate that the block
copolymer has a high potential as a compatibilizer.
Although the catalytic activity shows a marked
dependency on the number of fluorine atoms in the
ligand with respect to the complexes used in this study,
complex 5 having no fluorine in the ligand inserts
ethylene in a living fashion. Therefore, the realization
of the living polymerization by the complexes is probably
ascribed to the bulky and rigid indolide-imine ligands,
which suppress chain termination or transfer steps,
unlike titanium complexes having fluorine-containing
phenoxy-imine ligands in which the presence of fluo-
rine(s) is a requirement for living polymerization.
Syn t h esis of P E -b-p oly(et h ylen e-co-p r op ylen e)
Block Cop olym er Usin g Com p lex 7/MAO Ca ta lyst
System . The usefulness of living olefin polymerization
catalysts is largely proportional to their potential for
preparing polyolefinic block copolymers, which may be
applied to a broad spectrum of areas including compati-
bilizers, elastomers, and composite materials. Thus, we
decided to synthesize a well-defined polyethylene-b-poly-
(ethylene-co-propylene) A-B diblock copolymer com-
prised of crystalline and amorphous segments in order
to show the usefulness of the catalyst system. Treatment
of complex 7 (10.0 µmol)/MAO (2.50 mmol) catalyst
system with ethylene (100 L/h) for 5 min and then with
ethylene-propylene (ethylene, 30 L/h; propylene, 70
L/h) for 50 min at 2 °C resulted in the formation of a
well-defined high molecular weight PE-b-poly(ethylene-
co-propylene) block copolymer having extremely narrow
polydispersity. An overlay of the unimodal GPC elution
curves for the PE A block (Mn 15 200, Mw/Mn 1.05) and
the final PE-b-poly(ethylene-co-propylene) A-B diblock
(Mn 31 400, Mw/Mn 1.17) indicates a shift toward higher
molecular weight region due to the subsequent copo-
lymerization step without providing any peak in the low-

Macromolecules, Vol. 35, No. 13, 2002
New Titanium Complexes 4885
mL) at room temperature. The mixture was stirred for 3 h at
Con clu sion
room temperature and then concentrated in vacuo to afford 1
In conclusion, a series of titanium complexes 5-8
featuring a pair of indolide-imine chelate ligands have
been introduced, which possess high catalytic perfor-
mance for the polymerization of ethylene using MAO
as a cocatalyst. Complexes 5-8 can polymerize ethylene
in a living fashion to form linear polyethylenes. Thus,
complexes 6 and 7 conduct room temperature living
ethylene polymerization to provide polyethylenes with
extremely narrow molecular weight distributions. In
addition, complex 8 having pentafluorophenyl in the
ligand at -10 °C promote high-speed living ethylene
polymerization to produce monodisperse polyethylenes
with high molecular weight values. The catalytic activi-
ties displayed by complex 8 are 2 orders of magnitude
larger than those of common living ethylene polymer-
ization catalysts. Moreover, with complex 7/MAO cata-
lyst system, a PE-b-poly(ethylene-co-propylene) block
copolymer has been successfully prepared, which may
be useful as a compatibilizer. Therefore, the titanium
complexes described herein represent a notable addition
to the limited list of high-performance titanium com-
plexes with no Cp ligands for olefin polymerization.
1
(1.78 g, 8.10 mmol) as yellow oil in 98% yield. H NMR (270
MHz, CDCl3): δ. 6.55 (dd, 1H, indole ring aromatic H), 7.1-
7.4 (m, 6H, indole ring aromatic H and benzene ring aromatic
H), 7.73 (d, 1H, indole ring aromatic H), 8.63 (s, 1H, CHdN),
10.76 (bs, 1H, NH). 13C NMR (100 MHz, CDCl3): 102.4, 119.3,
119.4, 120.9, 124.6, 125.1, 125.8, 126.6, 128.5, 129.3, 133.8,
151.9, 161.3. FD-MS (m/z) 220 (M+).
7-(2,3,4,5,6-F(P h )NCH)C8H5NH (4). p-Toluenesulfonic acid
monohydrate (20 mg) was added to a stirred solution of
7-formylindole (1.60 g, 11.0 mmol) and pentafluoroaniline (2.11
g, 11.5 mmol) in dried toluene (50 mL) at room temperature.
The mixture was stirred for 2 h at 40 °C, and then the toluene
was evaporated in vacuo at 40 °C to give a residue. The residue
was dissolved in dried toluene (50 mL) and stirred for 1 h at
40 °C. The toluene was evaporated in vacuo to give a solid
residue. To the residue, dichloromethane (15 mL) and hexane
(30 mL) were added, and the resulting mixture was filtered
through a glass filter. The filtrate was concentrated in vacuo
to give a solid. Recrystallization from dried ethyl acetate (5
mL) and n-hexane (30 mL) yielded 4 (2.39 g, 7.70 mmol) as a
pale yellow solid in 70% yield; mp 157 °C. 1H NMR (270 MHz,
CDCl3): δ. 6.66 (dd, 1H, indole ring aromatic H), 7.23 (m, 1H,
indole ring aromatic H), 7.39 (dd, 1H, indole ring aromatic H),
7.48 (dd, 1H, indole ring aromatic H), 7.89 (d, 1H, J ) 7.6 Hz,
indole ring aromatic H), 8.88 (m, 1H, CHdN), 10.58 (bs, 1H,
NH). 13C NMR (100 MHz, CDCl3): 102.7, 118.7, 119.4, 125.5,
126.1, 126.5, 128.0, 128.9, 133.7, 136.8-136.9, 139.0-139.5,
141.6-141.8, 141.7, 169.0. C15H7N2F5 310.23. Calcd: C, 58.08;
H, 2.27; N, 9.03. Found: C, 58.10; H, 2.30; N, 8.91. FD-MS
(m/z) 310 (M+).
Exp er im en ta l Section
Gen er a l P r oced u r es a n d Ma ter ia ls. All manipulations
of air- and/or water-sensitive materials were carried out under
a dry nitrogen atmosphere using standard Schlenk cannula
techniques or in a conventional nitrogen-filled glovebox.
Dried solvents (diethyl ether, ethanol, dichloromethane
(CH2Cl2), n-hexane, n-pentane, and toluene) used for ligand
and complex syntheses were purchased from Wako Pure
Chemical Industries, Ltd., and used without further purifica-
tion. 7-Formylindole was prepared according to an established
procedure. TiCl4 was purchased from Aldrich Chemical Co.,
Inc. Ethylene was obtained from Sumitomo Seika Co., Ltd.
Methylalumoxane (MAO) was purchased from Albemarle as
a 1.2 M toluene solution, and the remaining trimethylalumi-
num was evaporated in vacuo prior to use. Toluene used as a
polymerization solvent (Wako Pure Chemical Industries, Ltd.)
was dried over Al2O3. All other chemicals were obtained
commercially and used as received.
Liga n d a n d Com p lex An a lyses. 1H NMR spectra were
recorded on a J EOL 270 spectrometer (270 MHz) in CDCl3
with tetramethylsilane as the internal standard at ambient
probe temperature (25 °C). Chemical shifts were reported in
δ units. The melting point (mp) of a ligand was measued by a
melting point microapparatus from Yanagimoto Seisakusho.
FD-MS spectra were recorded on an SX-102A from J apan
Electron Optics Laboratory Co., Ltd. Elemental analysis for
CHN was performed by a CHNO type from Helaus Co.
P olym er An a lyses. 13C NMR spectra for polyethylene were
recorded on an NEC-LA500 spectrometer (125 MHz) using
o-dichlorobenzene with 20% benzene-d6 as a solvent at 120 °C.
Molecular weight distribution (Mw/Mn) values of polymers were
determined using a Waters 150-C gel permeation chromato-
graph at 145 °C using polyethylene calibration and equipped
with three TSKgel columns (two sets of TSKgelGMHHR-H(S)-
HT and TSKgelGMH6-HTL). o-Dichlorobenzene was used as
a solvent at a flow rate of 1.0 mL/min. Vinyl end group
concentration of the polyethylenes and propylene contents of
the copolymers were determined by IR analyses using FT/IR-
350 from J ASCO Co. Peak melting temperatures (Tm) of the
polymers were determined by DSC with a Shimazu DSC-60
differential scanning calorimeter, measured upon reheating
the polymer sample to 200 °C at a heating rate of 10 °C/min.
Transmission electron microscopy (TEM) images were obtained
using a HITACHI H-8100 transmission electron microscopy.
Com p lex Syn th eses. 7-(P h NCH)C8H5NH (1). Acetic acid
(0.3 mL) was added to a stirred solution of 7-formylindole (1.20
g, 8.27 mmol) and aniline (0.77 g, 8.27 mmol) in ethanol (40
7-(2,6-F (P h )NCH)C8H5NH (2). 2 was prepared using a
procedure similar to that for 4; mp 119 °C. 1H NMR (270 MHz,
CDCl3): δ. 6.64 (dd, 1H, indole ring aromatic H), 6.95-7.12
(m, 3H, benzene ring aromatic H), 7.24 (t, 1H, indole ring
aromatic H), 7.38 (dd, 1H, indole ring aromatic H), 7.47 (dd,
1H, indole ring aromatic H), 7.84 (d, 1H, J ) 8.1 Hz, indole
ring aromatic H), 8.92 (m, 1H, CHdN), 10.80 (bs, 1H, NH).
13C NMR (100 MHz, CDCl3): 102.4, 111.7-112.0, 119.2, 119.4,
125.1-125.3, 125.4, 125.5, 127.3, 128.1-128.3, 128.7, 133.7,
154.3-156.8, 167.2. FD-MS (m/z) 256 (M+).
7-(2,4,6-F (P h )NCH)C8H5NH (3). 3 was prepared using a
1
procedure similar to that for 4; mp 103 °C. H NMR (CDCl3):
δ. 6.64 (dd, 1H, indole ring aromatic H), 6.73-6.87 (m, 2H,
benzene ring aromatic H), 7.22 (t, 1H, indole ring aromatic
H), 7.38 (dd, 1H, indole ring aromatic H), 7.45 (dd, 1H, indole
ring aromatic H), 7.84 (d, 1H, J ) 7.8 Hz, indole ring aromatic
H), 8.91 (m, 1H, CHdN), 10.70 (bs, 1H, NH). 13C NMR (100
MHz, CDCl3): 100.4-101.0, 102.4, 119.3, 119.4, 124.8-125.0,
125.1, 125.5, 127.3, 128.7, 133.7, 154.3-157.0, 157.5-160.3,
167.0. FD-MS (m/z) 274 (M+).
[7-(P h NCH)C8H5N]2TiCl2(5). To a stirred solution of 1
(0.85 g, 3.86 mmol) in dried diethyl ether (15 mL) at -78 °C,
a 1.56 M n-butyllithium hexane solution (2.50 mL, 3.90 mmol)
was added dropwise over a 15 min period. The mixture was
allowed to warm to room temperature and stirred for 4 h. The
resulting solution was added dropwise over a 20 min period
to a 0.5 M n-heptane solution of TiCl4 (3.86 mL, 1.93 mmol)
in dried diethyl ether (6 mL) at -78 °C with stirring. The
mixture was allowed to warm to room temperature and stirred
overnight. Evaporation of the solvent in vacuo yielded a crude
product. To the crude product, dried CH2Cl2 (30 mL) was
added, and the mixture was stirred for 10 min and filtered.
The filtrate was evaporated in vacuo to afford a solid residue.
To the solid residue, dried CH2Cl2 (3.0 mL) and dried n-hexane
(20 mL) were added, and the mixture was stirred for 10 min.
Filtration gave 5 (0.39 g, 0.69 mmol) as a dark purple solid in
36% yield; mp >300 °C. 1H NMR(CDCl3): δ 6.01 (m, 2H, indole
ring aromatic H), 6.7-7.3 (m, 4H, indole ring aromatic H +
10H, benzene ring aromatic H), 7.55 (m, 2H, indole ring
aromatic H), 8.24 (s, 2H, CHdN), 8.35 (m, 2H, indole ring
aromatic H). 13C NMR data for complex 5 were not available
since complex 5 was unstable in solution and thus decomposed
during the 13C NMR measurement. C30H22N4Cl2Ti: Calcd: C,

4886 Matsugi et al.
Macromolecules, Vol. 35, No. 13, 2002
64.66; H, 3.98; N, 10.05. Found: C, 64.18; H, 4.10; N, 10.21.
FD-MS (m/z) 556 (M+).
added to the acidic methanol (1 L including 2 mL of concen-
trated HCl). The solid polyethylene was recovered by filtration,
washed with methanol (200 mL × 2), and dried (vacuum oven
at 80 °C, overnight).
[7-(2,3,4,5,6-F (P h )NCH)C8H5N]2TiCl2 (8). To a stirred
solution of 4 (1.00 g, 3.22 mmol) in dried toluene (30 mL) at 0
°C, a 1.56 M n-butyllithium hexane solution (2.17 mL, 3.38
mmol) was added dropwise over a 5 min period. The mixture
was allowed to warm to room temperature and stirred for 4
h. The resulting mixture was added dropwise over a 20 min
period to a 0.5 M n-heptane solution of TiCl4 (3.22 mL, 1.61
mmol) in dried toluene (15 mL) at -78 °C with stirring. The
mixture was allowed to warm to room temperature and stirred
overnight. Evaporation of the solvent in vacuo yielded a crude
product. To the crude product, dried CH2Cl2 (20 mL) was
added, and the mixture was stirred for 10 min and filtered.
The solid residue was washed with dried CH2Cl2 (20 mL × 3),
and the combined organic filtrates were concentrated in vacuo
to afford a dark purple solid. The solid was recrystallized from
a dried CH2Cl2/dried n-hexane (1/1) solution (20 mL) at room
temperature to give 8 (0.56 g, 0.76 mmol) as dark purple
crystals in 47% yield; mp >300 °C. 1H NMR(CDCl3): δ 6.21
(d, 2H, J ) 3.2 Hz, indole ring aromatic H), 7.18-7.25 (m, 2H,
indole ring aromatic H), 7.40 (d, 2H, J ) 7.0 Hz, indole ring
aromatic H), 7.84 (d, 2H, J ) 6.8 Hz, indole ring aromatic H),
8.22 (d, 2H, J ) 2.7 Hz, indole ring aromatic H), 8.32 (s, 2H,
CHdN). 13C NMR (100 MHz, CDCl3): 104.2, 118.9, 122.2,
125-129, 128.9, 130.4, 131.3, 136-142, 139.8, 145.3, 173.2;
P r ep a r a tion of a P E-b-p oly(eth ylen e-co-p r op ylen e)
Block Cop olym er . To a nitrogen-purged 500 mL glass reactor
equipped with a mechanical stirrer, a temperature probe, and
a condensor, toluene (250 mL) was introduced and stirred
vigorously (600 rpm). The toluene was kept at 2 °C using an
ice-cold water bath, and then the ethylene gas feed (100 L/h)
was started. After 15 min, polymerization was initiated by the
addition of a 1.25 M toluene solution of MAO (2.0 mL, 2.5
mmol) and then a 0.002 M toluene solution of complex 7 (5.0
mL, 0.01 mmol) into the reactor with vigorous stirring (600
rpm). After 5 min, the feed gas was changed from ethylene to
ethylene/propylene (30/70 L/h). After 50 min, the polymeriza-
tion was terminated by the addition of isobutyl alcohol (10 mL).
The resulting mixture was added to the acidic methanol (1000
mL including 2 mL of concentrated HCl). The polymer was
collected by filtration, washed with methanol (200 mL × 2),
and dried (vacuum oven at 120 °C, overnight).
P r ep a r a tion of P E/p oly(eth ylen e-co-p r op ylen e) Blen d
Sa m p le for TEM Mea su r em en t. Polyethylene (200 mg,
Table 4, entry 2) and ethylene/propylene copolymer (920 mg,
Table 4, entry 3) and toluene (40 mL) were introduced to a
nitrogen-purged 200 cm3 reactor, and the contents were
magnetically stirred for 5 min under nitrogen at room tem-
perature. The mixture was heated at reflux temperature for
1 h with stirring. The resulting solution was poured into
methanol (500 mL) at 60 °C. The precipitated polymer was
collected by filtration, washed with methanol (200 mL × 2),
and dried (vacuum oven at 80 °C, overnight).
C
30H12N4F10Cl2Ti 737.20: Calcd: C, 48.88; H, 1.64; N, 7.60.
Found: C, 48.40; H, 1.73; N, 7.72. FD-MS (m/z) 737 (M+).
[7-(2,6-F (P h )NCH)C8H5N]2TiCl2(6). 6 was prepared using
a procedure similar to that for 8; mp >300 °C. 1H NMR-
(CDCl3): δ 5.98 (d, 2H, J ) 3.24 Hz, indole ring aromatic H),
6.14 (m, 2H, benzene ring aromatic H), 6.73-6.78 (m, 4H,
benzene ring aromatic H), 7.10 (t, 2H, J ) 7.6 Hz, indole ring
aromatic H), 7.31 (d, 2H, J ) 5.4 Hz, indole ring aromatic H),
7.66 (dd, 2H, indole ring aromatic H), 8.19 (dd, 2H, indole ring
aromatic H), 8.31 (s, 2H, NdCH). 13C NMR (100 MHz,
CDCl3): 103.6, 110.4-112.0, 116.9, 119.3, 121.4, 125-127,
128.7, 128.9, 130.1, 140.0, 145.5, 153.5-156.0, 172.2. C30H18N4F4-
Cl2Ti: Calcd: C, 57.26; H, 2.88; N, 8.90. Found: C, 56.56; H,
3.20; N, 9.12. FD-MS (m/z) 628 (M+).
TEM An a lysis. Ultrathin (ca. 100 nm) sections of the
polymers that had been pressed to give sheets and dyed with
RuO4 were prepared with a Reica Ultracut microtome equipped
with a diamond knife at -100 °C. The specimens were
examined with a Hitachi H-8100 transmission electron mi-
croscopy operating at 100 kV.
Ack n ow led gm en t. We thank Dr. M. Mullins for his
fruitful discussions and suggestions. We also thank Y.
Suzuki, Y. Yoshida, M. Mitani, J . Saito, H. Makio, S.
Matsuo, H. Kaneko, Y. Tohi, Y. Nakayama, S. Mats-
uura, J . Mohri, S. Ishii, K. Tsuru, N. Matsukawa, Y.
Sonobe, R. Furuyama, H. Bando, H. Terao, and J . S.
Harp for their research and technical assistance.
[7-(2,4,6-F (P h )NCH)C8H5N]2TiCl2(7). 7 was prepared us-
1
ing a procedure similar to that for 8; mp >300 °C. H NMR-
(CDCl3): δ 5.85-5.95 (m, 2H, benzene ring aromatic H), 6.10
(d, 2H, J ) 3.2 Hz, indole ring aromatic H), 6.49-6.55 (m, 2H,
benzene ring aromatic H), 7.14 (t, 2H, J ) 7.6 Hz, indole ring
aromatic H), 7.33 (dd, 2H, indole ring aromatic H), 7.73 (dd,
2H, indole ring aromatic H), 8.20 (dd, 2H, indole ring aromatic
H), 8.29 (s, 2H, NdCH). 13C NMR (100 MHz, CDCl3): 98.9-
99.1, 99.6-100.9, 103.8, 119.2, 128.0-13.6, 128.6, 129.6, 139.8,
145.4, 153.5-160.8, 172.6. C30H16N4F6Cl2Ti: Calcd: C, 54.17;
H, 2.42; N, 8.42. Found: C, 54.15; H, 2.09; N, 8.23. FD-MS
(m/z) 664 (M+).
Su p p or tin g In for m a tion Ava ila ble: Calculated struc-
tures of ethylene coordinated active species, plot of polymer
yield as a function of polymerization time, plot of Mn and Mw/
Mn as a function of polymer yield, DSC measurements of PE
and PF-b-poly(ethylene-co-propylene), and tables of ethylene
polymerization results with complex/MAO catalyst systems.
This material is available free of charge via the Internet at
http://pubs.acs.org.
DF T Ca lcu la tion s.35 All calculations were performed at the
gradient corrected density functional BLYP level by means of
the Amsterdam Density Functional (ADF 2001.01) program.
We used the triple-ê STO basis set for the titanium and the
double-ê STO basis set for the N, O, and methyl as a model of
a polymer chain and the single-ê STO basis set on the other
atoms to calculate the optimized geometries. For energy calcu-
lations, the triple-ê STO basis set for the titanium and the
double-ê plus polarization STO basis set for the other atoms
were used, and the quasi-relativistic correction was also added.
Eth ylen e P olym er iza tion . Ethylene polymerization was
carried out under atmospheric pressure in toluene using a 500
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Macromolecules, Vol. 35, No. 13, 2002
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