New titanium complexes having two indolide-imine chelate ligands for living ethylene polymerization

Article abstract of DOI:10.1246/cl.2001.566

Three new titanium complexes having two indolide-imine ligands were synthesized and investigated as ethylene polymerization catalysts. These complexes using MAO as a cocatalyst promoted ethylene polymerization at 25 °C to produce polyethylenes (M_n: 11000-41800) having narrow molecular weight distributions (M_w/M_n: 1.11-1.14), displaying very high activities (52-288 kg-PE/mol-Ti·h·atm).

Full text of DOI:10.1246/cl.2001.566

566
Chemistry Letters 2001
New Titanium Complexes Having Two Indolide-Imine Chelate Ligands
for Living Ethylene Polymerization
Tomoaki Matsugi, Shigekazu Matsui, Shin-ichi Kojoh, Yukihiro Takagi,
Yoshihisa Inoue, Terunori Fujita,* and Norio Kashiwa
R&D Center, Mitsui Chemicals, Inc., 580-32 Nagaura, Sodegaura, Chiba 299-0265
(Received March 9, 2001; CL-010207)
Three new titanium complexes having two indolide-imine
ligands were synthesized and investigated as ethylene polymer-
ization catalysts. These complexes using MAO as a cocatalyst
promoted ethylene polymerization at 25 °C to produce polyeth-
ylenes (Mn:11000–41800) having narrow molecular weight dis-
tributions (Mw/Mn: 1.11–1.14), displaying very high activities
(52–288 kg-PE/mol-Ti·h·atm).
The development of high performance living olefin poly-
merization catalysts has been the subject of extensive study for
many years since living olefin polymerization is a powerful tool
for creating precisely-controlled polymers such as monodis-
perse polymers, end-functionalized polymers, and block
copolymers.1,3k The living olefin polymerization requires low
temperatures to suppress the side reactions, namely chain termi-
nation or transfer reactions and, thus, it generally produces a
relatively low molecular weight polymer, displaying low activi-
ty. Much research effort devoted to the study on soluble, well-
defined transition metal complexes for olefin polymerization2
has resulted in the introduction of a variety of living olefin
polymerization catalysts working at relatively high tempera-
tures. There are, however, a limited number of examples of
room-temperature living ethylene polymerizations using solu-
ble, well-defined transition metal complexes so far.1f,1g,1o
Recently, we have found, as a result of ligand-oriented cat-
alyst design research, that transition metal complexes having
non-symmetric bidentate ligand(s) (e.g., phenoxy-imine ligand,
pyrrolide-imine ligand, and imine-pyridine ligand) exhibit high
catalytic performance for olefin polymerization. 3 These results
inspired us to conduct further study on transition metal com-
plexes having non-symmetric bidentate ligand(s) as potentially
viable olefin polymerization catalysts.
The activities obtained were in the range of 52–288 kg-
PE/mol-Ti·h·atm. In all cases, solid polyethylene was obtained.
The melting temperature (Tm) of the polyethylenes, based on
DSC measurement, lies in the range of 132.2–134.2 °C, sug-
gesting that the polyethylenes possess a linear structure. GPC
analyses revealed that the polyethylenes produced at 25 °C pos-
sess narrow molecular weight distributions (Mw/Mn: 1.11–1.14,
entries 1–3) for their high molecular weights (Mn:
11000–41800). The Mw/Mn values suggest that complexes 1–3
/ MAO catalyst systems have the character of living polymer-
ization. Initiation efficiencies for the polymerization are more
than 71%.7 Interestingly, ethylene polymerization using com-
plex 3 / MAO at 50 °C for 10 min produced polyethylene hav-
ing a reasonably narrow molecular weight distribution (Mw/Mn:
1.24, Mn: 53200), displaying higher catalytic activity (290 kg-
PE/mol-Ti·h·atm) (entry 4). A comparison of the polymeriza-
tion results of entries 1–3 indicates that the substituents on the
imine nitrogen influenced catalytic activities. The introduction
of fluorine atoms to the benzene ring on imine nitrogen is sup-
posed to enhance the electrophilicity of the titanium metal in
active species for olefin polymerization. Thus, concerning the
titanium complexes we studied, the electrophilicity of the titani-
In this paper, we introduce three titanium complexes, bear-
ing two indolide-imine chelate ligands, which promote living
ethylene polymerization at room temperature.
A general synthetic route for titanium complexes employed
in this study is shown in Scheme 1. The indolide-imine ligands
of general structures A–C, namely 7-(N-aryliminomethyl)
indole ligands, are prepared in high yields (A: 98%, B: 64%, C:
72%) by the Schiff-base condensation of the desired primary
amine with 7-formylindole.4 The titanium complexes possess-
ing two indolide-imine ligands, namely bis[7-(N-arylimi-
nomethyl)indolinyl]titanium(IV) dichloride complexes, are
obtained as dark purple powder in moderate yields (1: 36%, 2:
27%, 3: 29%) by the treatment of TiCl4 with 2 equiv of the
lithium salt of the indolide-imine ligand. 5
Complexes 1–3 were investigated as ethylene polymeriza-
tion catalysts using MAO as a cocatalyst for 10 min at 25 °C
under atmospheric pressure.6 The results are collected in Table 1.
Copyright © 2001 The Chemical Society of Japan

Chemistry Letters 2001
567
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um metal in active species probably plays a predominant role in
determining the polymerization activity. The highest activity
(288 kg-PE/mol-Ti·h·atm) (entry 3) is extremely high through
the polymerization proceeded in a living fashion.
Catalytic performance of complex 3 / MAO catalyst sys-
tem was further investigated since this catalyst system exhibited
the highest catalytic activity and the narrowest molecular
weight value. Mn and Mw/Mn values of complex 3 / MAO were
monitored as a function of polymer yield at 25 °C. As shown in
Figure 1, the Mn value increased proportionally with the poly-
mer yield while the narrow Mw/Mn value was retained, further
confirming a living polymerization.
2
3
4
5
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1
Complex 1: H NMR (270 MHz, CDCl3, 25 °C, TMS); δ
In summary, three new titanium complexes with two
indolide-imine chelate ligands were prepared and found to be
room-temperature living ethylene polymerization catalysts.
The influence of substitution groups of the ligands and cocata-
lysts as well as potential applications of the catalyst systems are
under active investigation.
6.01 (d, 2H), 6.7–7.3 (m, 4H(indole-H) + 10H(phenyl-H)),
7.55 (d, 2H), 8.24 (s, 2H), 8.35 (d,2H). Anal. Calcd for
C30H22N4Cl2Ti: C, 64.66. H, 3.98; N, 10.05%. Found: C,
64.18. H, 4.10; N, 10.21%. FD-mass: m/z: 556(M+).
1
Complex 2: H NMR (270 MHz, CDCl3, 25 °C, TMS); δ
5.98 (d, 2H), 6.14 (m, 2H), 6.74 (d, 2H), 6.77 (d, 2H), 7.10
(t, 2H), 7.31 (m, 2H), 7.65 (m, 2H), 8.18 (m, 2H), 8.31 (s,
2H). FD-mass: m/z: 628(M+). Reasonable elemental analysis
data were not obtained since complex 2 was unstable and
References and notes
1
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1
decomposed on standing. Complex 3: H NMR (270MHz,
CDCl3, 25 °C, TMS); δ 5.98 (m, 2H), 6.08 (d, 2H), 6.51 (m,
2H), 7.14 (t, 2H), 7.33 (m, 2H), 7.73 (m, 2H), 8.20 (m, 2H),
8.29 (s, 2H). Anal. Calcd for C30H16N4 F6Cl2Ti: C, 54.17. H,
2.42; N, 8.42%. Found: C, 54.15. H, 2.09; N, 8.23%. FD-
mass: m/z: 664(M+).
General polymerization procedure: Flow of ethylene gas
(100 L/h) was charged into 250 mL of toluene at 25 °C. To
this solution, MAO (Albemarle MAO, 1.2 M toluene solu-
tion) and a toluene solution of a complex was added at the
desired polymerization temperature. After the prescribed
time, 25 mL of isobutyl alcohol was added to terminate the
polymerization.
6
7
Although initiation efficiency cannot be discussed accurately
for such low polymer yields, the values suggest the high effi-
ciency for generating active species.