New titanium complexes having two pyrrolide-imine chelate ligands: Syntheses, structures, and ethylene polymerization behavior

Article abstract of DOI:10.1021/om010468q

New titanium complexes 1-4 having two nonsymmetric bidentate pyrrolide-imine chelate ligands, [2-(RNCH)C₄H₃N]₂TiCl₂ (1, R = Ph; 2, R = Et; 3, R = n-hexyl; 4, R = cyclohexyl), are prepared in good yields from the lithium salt of the corresponding ligands and TiCl₄. Complex 1 is suggested by DFT calculations to adopt a distorted-octahedral structure in which the two pyrrolide-N atoms are situated in trans positions, while the two imine-N atoms and the two Cl atoms are located cis to one another. The spatial disposition elucidated by X-ray crystallographic analysis of complex 1 is consistent with the preferred structure predicted by DFT calculations. The molecular structures of complexes 2 and 4 established by X-ray analyses are very similar to that of complex 1. DFT calculations suggest that an active species derived from complex 1, for ethylene polymerization, possesses cis-located active sites trans to the imine-N atoms. These complexes were investigated as ethylene polymerization catalysts. Using methylalumoxane (MAO) as a cocatalyst, these complexes display very high activities and produce high-molecular-weight polyethylenes. Among them, complex 4 exhibits the highest activity (14 100 kg of polymer/((mol of Ti) h) comparable to that of Cp₂TiCl₂ with a very high molecular weight (M_v) value of 2 601 000. Alternatively, using Ph₃CB(C₆F₅)_4/i-Bu₃Al as a cocatalyst, these complexes produce ultrahigh-molecular-weight polyethylenes (M_v > 4 000 000) with high activities (1500-2000 kg of polymer/((mol of Ti)/h).

Full text of DOI:10.1021/om010468q

Organometallics 2001, 20, 4793-4799
4793
New Tita n iu m Com p lexes Ha vin g Tw o P yr r olid e-Im in e
Ch ela te Liga n d s: Syn th eses, Str u ctu r es, a n d Eth ylen e
P olym er iza tion Beh a vior
Yasunori Yoshida, Shigekazu Matsui, Yukihiro Takagi, Makoto Mitani,
Takashi Nakano, Hidetsugu Tanaka, Norio Kashiwa, and Terunori Fujita*
R&D Center, Mitsui Chemicals, Inc., 580-32 Nagaura, Sodegaura, Chiba, J apan
Received J une 4, 2001
New titanium complexes 1-4 having two nonsymmetric bidentate pyrrolide-imine chelate
ligands, [2-(RNCH)C4H3N]2TiCl2 (1, R ) Ph; 2, R ) Et; 3, R ) n-hexyl; 4, R ) cyclohexyl),
are prepared in good yields from the lithium salt of the corresponding ligands and TiCl4.
Complex 1 is suggested by DFT calculations to adopt a distorted-octahedral structure in
which the two pyrrolide-N atoms are situated in trans positions, while the two imine-N
atoms and the two Cl atoms are located cis to one another. The spatial disposition elucidated
by X-ray crystallographic analysis of complex 1 is consistent with the preferred structure
predicted by DFT calculations. The molecular structures of complexes 2 and 4 established
by X-ray analyses are very similar to that of complex 1. DFT calculations suggest that an
active species derived from complex 1, for ethylene polymerization, possesses cis-located
active sites trans to the imine-N atoms. These complexes were investigated as ethylene
polymerization catalysts. Using methylalumoxane (MAO) as a cocatalyst, these complexes
display very high activities and produce high-molecular-weight polyethylenes. Among them,
complex 4 exhibits the highest activity (14 100 kg of polymer/((mol of Ti) h) comparable to
that of Cp2TiCl2 with a very high molecular weight (Mv) value of 2 601 000. Alternatively,
using Ph3CB(C6F5)4/i-Bu3Al as a cocatalyst, these complexes produce ultrahigh-molecular-
weight polyethylenes (Mv > 4 000 000) with high activities (1500-2000 kg of polymer/((mol
of Ti)/h).
In tr od u ction
borate ligands,10 zirconium complexes with diamide
ligands11 or bis(phenoxy)-amine ligands,12 and tanta-
lum complexes with amide-pyridine ligands.13 These
complexes display activities comparable to those of the
group 4 metallocene catalysts.
Research and development of highly active, well-
defined group 4 metallocene catalysts has stimulated
the progress of organometallic chemistry and catalyst
chemistry.1 In addition, the above research and develop-
ment has revolutionized polymer chemistry to create a
variety of polymers having novel properties and uses.2
Therefore, after the discovery of the metallocene cata-
lysts, well-defined transition-metal complexes have been
intensively investigated, aiming at discovering highly
active new olefin polymerization catalysts.3 Recent
advances in the design and synthesis of well-defined
transition-metal complexes have spurred the rapid
development of highly active olefin polymerization
catalysts. Thus, quite a few highly active olefin poly-
merization catalysts based on both early- and late-
transition-metal complexes have been developed. No-
table examples are nickel complexes with diimine
ligands4 or phenoxy-imine ligands,5 iron or cobalt
complexes with diimine-pyridine ligands,6 titanium
complexes with diamide ligands,7 phosphine-imide
ligands,8 indolide-imine ligands,9 or tris(pyrazolyl)-
Previously, we have investigated well-defined transi-
tion-metal complexes featuring nonsymmetric bidentate
ligand(s)14 on the basis of the ligand-oriented catalyst
(4) (a) J ohnson, L. K.; Killian, C. M.; Brookhart, M. J . Am. Chem.
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H.; Bansleben, D. A.; Day, M. W. Organometallics 1998, 17, 3149. (b)
Younkin, T. R.; Connor, E. F.; Henderson, J . I.; Friedrich, S. K.; Grubbs,
R. H.; Bansleben, D. A. Science 2000, 287, 460.
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Am. Chem. Soc. 1996, 118, 10008.
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X.; Brown, S. J .; Swabey, J . W.; Wang, Q.; Xu, W.; Zoricak, P.; Harrison,
D. G. Organometallics 1999, 18, 2046.
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J .; Howard, P. Chem. Commun. 1998, 313.
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(3) For reviews: (a) Britovsek, G. J . P.; Gibson, V. C.; Wass, D. F.
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10.1021/om010468q CCC: $20.00 © 2001 American Chemical Society
Publication on Web 10/10/2001

4794 Organometallics, Vol. 20, No. 23, 2001
Yoshida et al.
design concept15h to develop highly active new olefin
polymerization catalysts. As a result of this study, we
have developed a new family of group 4 transition-metal
complexes possessing two phenoxy-imine chelate li-
gands, named FI Catalysts, displaying high catalytic
performance for olefin polymerization,15 including living
olefin polymerization.16 These results inspired us to
conduct further investigation along this research line.
Recently, we have turned our efforts to group 4 transi-
tion metal complexes having two pyrrolide-imine che-
late ligands17 because the active species of these com-
plexes for olefin polymerization may have cis-located
active sites trans to the imine-N atoms, the same as the
active species of highly active group 4 transition-metal
complexes having two phenoxy-imine chelate ligands.15
In this paper, we describe the syntheses and structures
of new titanium complexes bearing two pyrrolide-imine
chelate ligands. Ethylene polymerization results using
these titanium complexes in the presence of methyl-
alumoxane or Ph3CB(C6F5)4/i-Bu3Al are also presented
in order to introduce the high potential of these com-
plexes for olefin polymerization.
Sch em e 1
Ch a r t 1. F ive Id ea lized Octa h ed r a l Str u ctu r es
a n d Th eir Rela tive F or m a tion En er gies Ba sed on
Isom er A
Resu lts a n d Discu ssion
Syn th esis of Tita n iu m Com p lexes Ha vin g Tw o
P yr r olid e-Im in e Liga n d s. A general synthetic route
for the titanium complexes with two pyrrolide-imine
ligands18,19 used in this study is shown in Scheme 1.
(14) Pioneering work concerning this field: (a) Bei, X.; Swenson, D.
C.; J ordan, R. F. Organometallics 1997, 16, 3282. (b) Tsukahara, T.;
Swenson, D. C.; J ordan, R. F. Organometallics 1997, 16, 3303. (c) Kim,
I.; Nishihara, Y.; J ordan, R. F.; Rogers, R. D.; Rheingold, A. L.; Yap,
P. A. Organometallics 1997, 16, 3314. (d) J ones, D.; Roberts, A.; Cavell,
K.; Keim, W.; Englert, U.; Skelton, B. W.; White, A. H. J . Chem. Soc.,
Dalton Trans. 1998, 255.
(15) (a) Fujita, T.; Tohi, Y.; Mitani, M.; Matsui, S.; Saito, J .;
Nitabaru, M.; Sigi, K.; Makio, H.; Tsutsui, T. Eur. Pat. 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. (c) Matsui, S.; Mitani, M.; Saito, J .; Tohi, Y.;
Makio, H.; Tanaka, H.; Fujita, T. Chem. Lett. 1999, 1263. (d) Matsui,
S.; Mitani, M.; Saito, J .; Matsukawa, N.; Tanaka, H.; Nakano, T.;
Fujita, T. Chem. Lett. 2000, 554. (e) Mitani, M.; Fujita, T. Chem. Chem.
Ind. 2000, 53, 691. (f) Tohi, Y.; Mitani, M.; Tanaka, H.; Fujita, T. Catal.
Catal. 2000, 42, 310. (g) Saito, J .; Mitani, M.; Matsui, S.; Kashiwa,
N.; Fujita, T. Macromol. Rapid Commun. 2000, 21, 1333. (h) Matsui,
S.; Fujita, T. Catal. Today 2001, 66, 61. (i) Matsukawa, N.; Matsui,
S.; Mitani, M.; Saito, J .; Tsuru, K.; Kashiwa, N.; Fujita, T. J . Mol.
Catal. A 2001, 169, 99. (j) Matsui, S.; Inoue, Y.; Fujita, T. J . Synth.
Org. Chem., J pn. 2001, 59, 232. (k) 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. (l) Saito, J .; Mitani, M.; Matsui, S.; Tohi, Y.; Makio,
H.; Nakano, T.; Tanaka, H.; Kashiwa, N.; Fujita, T. Macromol. Chem.
Phys., in press. (m) Ishi, S.; Saito, J .; Mitani, M.; Mohri, J .; Matsukawa,
N.; Tohi, Y.; Matsui, S.; Kashiwa, N.; Fujita, T. J . Mol. Catal. A, in
press. (n) Inoue, Y.; Nakano, T.; Tanaka, H.; Kashiwa, N.; Fujita, T.
Chem. Lett. 2000, 1060.
(16) (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.; Yoshida, Y.; Tohi, Y.; Matsui, S.; Mitani, M.; Kojoh, S.;
Kashiwa, N. Catal. Catal. 2001, 43, 67. (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. (d) Saito, J .; Mitani, M.; Mohri,
J .; Ishii, S.; Yoshida, Y.; Matsugi, T.; Kojoh, S.; Kashiwa, N.; Fujita,
T. Chem. Lett. 2001, 576. (e) Saito, J .; Mitani, M.; Onda, M.; Mohri,
J .; Ishii, S.; Yoshida, Y.; Matsugi, T.; Kojoh, S.; Kashiwa, N.; Fujita,
T. Macromol. Rapid Commun. 2001, 22, 1072. (f) Kojoh, S.; Matsugi,
T.; Saito, J .; Mitani, M.; Fujita, T.; Kashiwa, N. Chem. Lett. 2001, 822.
(17) (a) Matsui, S.; Nitabaru, M.; Yoshida, Y.; Mitani, M.; Fujita,
T. Eur. Pat. 1008595, 2000; Chem. Abstr. 2000, 133, 43969. (b) Yoshida,
Y.; Matsui, S.; Takagi, Y.; Mitani, M.; Nitabaru, M.; Nakano, T.;
Tanaka, H.; Fujita, T. Chem. Lett. 2000, 1270. (c) Yoshida, Y.; Matsui,
S.; Takagi, Y.; Mitani, M.; Nitabaru, M.; Nakano, T.; Tanaka, H.;
Kashiwa, N.; Fujita, T. Catal. Catal. 2001, 43, 103.
The pyrrolide-imine ligands of structures 1a -4a are
prepared (yields: 1a , 65%; 2a , 66%; 3a , 96%; 4a , 96%)
by the Schiff-base condensation of the desired primary
amine with pyrrole-2-carboxaldehyde in dry EtOH using
formic acid as a catalyst. The titanium complexes
bearing two pyrrolide-imine ligands 1-4 are obtained
as black powders (yields: 1, 79%; 2, 58%; 3, 37%; 4, 38%)
by the treatment of TiCl4 with 2 equiv of the lithium
salt of the pyrrolide-imine ligand in dry diethyl ether.
The overall yields starting from pyrrole-2-carboxalde-
hyde are fairly good (1, 51%; 2, 38%; 3, 36%; 4, 36%).
1
Str u ctu r e of Com p lex 1. The H NMR spectra of
complexes 1-4 display a single sharp resonance for the
methine proton (-HNdC-) of the pyrrolide-imine
chelate ligands, consistent with an octahedral coordina-
tion structure.
Five idealized octahedral structures (A-E, Chart 1)
in which the titanium is bound to two cis-coordinated
pyrrolide-imine chelate ligands are possible for each
complex because the titanium complex possesses two
nonsymmetric bidentate ligands. The relative formation
energies for these five possible isomers of complex 1
were calculated using DFT to establish the most stable
isomeric structure. Structure A was predicted to be the
most favored (see Chart 1). The calculations suggest
(18) Gibson, V. C.; Maddox, P. J .; Newton, C.; Redshaw, C. Solan,
G. A.; White, A. J . P.; Williams, D. J . Chem. Commun. 1998, 1651.
(19) Matsuo, Y.; Mashima, K.; Tani, K. Chem. Lett. 2000, 1114.

Ti Complexes with Pyrrolide-Imine Ligands
Organometallics, Vol. 20, No. 23, 2001 4795
Ta ble 1. Su m m a r y of Cr ysta llogr a p h ic Da ta for Com p lexes 1, 2, a n d 4
1
2
4
formula
fw
cryst syst
space group
a (Å)
b (Å)
c (Å)
â (deg)
V (Å)
C
22H18N4Cl2Ti
C14H18N4Cl2Ti
361.13
monoclinic
P21/n
7.922(2)
17.862(8)
11.866(2)
97.18(1)
1665.9(9)
4
C22H30N4Cl2Ti
469.31
monoclinic
P21/n
14.064(9)
11.446(2)
14.354(2)
92.06(3)
2309(1)
4
457.22
monoclinic
P21/n
11.606(2)
14.200(2)
14.294(2)
113.59(1)
2158.9(6)
4
1.407
6.59
Mo KR, 0.710 69
296 K
Z
F(calcd) (g cm-3
)
1.440
8.32
Mo KR, 0.710 70
150K
1.350
6.18
Mo KR, 0.710 70
150K
µ (cm-1
λ (Å)
T
)
2θmax (deg)
no. of obsd rflns
55.0
5482
55.2
3490
57.1
4797
no. of unique rflns
5175
3462
4699
F000
936
0.031
0.029
744
0.151
0.222
984
0.114
0.116
Ra
b
Rw
a
2
2
2
b
R ) ∑(||Fo| - |Fc||)/∑|Fo| (complex 1); R ) ∑(|Fo| - |Fc| )/∑|Fo| (complexes 2 and 4). Rw ) [∑w(|Fo| - |Fc|)2/∑w(|Fo|)2]1/2 (complex 1);
Rw ) [∑w(|Fo| - |Fc| )2/∑w(|Fo| )2]1/2 (complexes 2 and 4).
2
2
2
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for Com p lexes 1, 2, a n d 4
1
2
4
Distances
Ti-Cl(1)
Ti-Cl(2)
Ti-N(1)
Ti-N(2)
Ti-N(3)
Ti-N(4)
2.2506(7)
2.2598(6)
2.043(2)
2.215(2)
2.033(2)
2.185(2)
2.275(1)
2.285(1)
2.044(3)
2.168(3)
2.049(3)
2.174(3)
2.3542(8)
2.208(1)
2.040(2)
2.130(2)
2.033(2)
2.231(2)
Angles
Cl(1)-Ti-Cl(2)
Cl(1)-Ti-N(1)
Cl(1)-Ti-N(2)
Cl(1)-Ti-N(3)
Cl(1)-Ti-N(4)
Cl(2)-Ti-N(1)
Cl(2)-Ti-N(2)
Cl(2)-Ti-N(3)
Cl(2)-Ti-N(4)
N(1)-Ti-N(2)
N(1)-Ti-N(3)
N(1)-Ti-N(4)
N(2)-Ti-N(3)
N(2)-Ti-N(4)
N(3)-Ti-N(4)
97.82(3)
101.77(5)
90.95(4)
91.68(5)
165.45(4)
91.31(5)
165.47(4)
104.10(5)
93.03(4)
75.50(6)
158.04(6)
87.60(6)
87.12(6)
80.54(5)
76.22(6)
97.86(4)
103.69(9)
87.13(8)
90.17(9)
165.06(10)
89.00(9)
165.89(9)
100.29(9)
91.38(9)
77.0(1)
162.2(1)
88.1(1)
92.9(1)
86.7(1)
76.6(1)
100.40(4)
101.20(6)
91.64(6)
90.15(6)
166.67(5)
90.72(5)
163.51(5)
101.30(6)
93.03(4)
75.80(7)
161.77(7)
89.51(7)
89.80(7)
83.25(7)
77.57(7)
F igu r e 1. Molecular structure of complex 1. Thermal
ellipsoids at the 50% level are shown. Hydrogen atoms are
omitted for clarity.
in trans positions (pN-Ti-pN, 158.04(6)°; Ti-pN,
2.033(2) and 2.043(2) Å), while the two iN atoms (iN-
Ti-iN, 80.54(5)°; Ti-iN, 2.185(2) and 2.215(2) Å) and
the two Cl atoms are oriented cis to each other (Cl-
Ti-Cl, 97.82(3)°; Ti-Cl, 2.2506(7) and 2.2598(6) Å) at
the central titanium metal. Thus, the spatial disposition
predicted by DFT calculations is in good accordance with
the results of the X-ray analysis, suggesting that DFT
calculations are an effective tool for analyzing the
molecular structure of a titanium complex having two
pyrrolide-imine chelate ligands.
The Ti-pN, Ti-iN, and Ti-Cl bond distances of
complex 1 are similar to those in known titanium
complexes.20 The cis angles associated with the che-
lated pyrrolide-imine ligands are acute (75.50(6) and
76.22(6)°). Alternatively, other cis angles between the
ligands lie in the range of 80.54(5)° (iN-Ti-iN) to
101.77(5)° (pN-Ti-Cl), but most of the cis angles are
around 90°, implying that constraints imposed by the
chelation and steric interactions between the ligands
are not significant for complex 1. The trans angles
between the ligands range from 158.04(6)° (pN-Ti-pN)
that complex 1 adopts a distorted-octahedral structure
in which two pyrrolide-N (pN) atoms are trans (pN-
Ti-pN, 172.5°; Ti-pN, 2.067 Å) and two imine-N (iN)
atoms (iN-Ti-iN, 90.0°; Ti-iN, 2.128 Å) and two Cl
atoms are cis (Cl-Ti-Cl, 97.3°; Ti-Cl, 2.353 Å). In the
predicted structure the phenyl group on the iN swings
out of the plane formed by the pyrrolide-imine chelate
ring, forming a dihedral angle of 52.7°. In structure A,
the short Ti-pN bonds are trans to each other to reduce
steric congestion of the ligands. In addition, the pN can
participate in Ti-pN π-bonding using different Ti d
orbitals.
The molecular structure of complex 1 was established
by a crystallographic analysis. The crystallographic
data, collection parameters, and refinement parameters
are summarized in Table 1. Selected bond angles and
distances for complex 1 are listed in Table 2.
As shown in Figure 1, complex 1 adopts a distorted-
octahedral geometry of the structure A type, having
molecular C2 symmetry. The two pN atoms are situated
(20) Bynum, R. V.; Hunter, W. E.; Rogers, R. D.; Atwood, J . L. Inorg.
Chem. 1980, 19, 2368.

4796 Organometallics, Vol. 20, No. 23, 2001
Yoshida et al.
F igu r e 3. Molecular structure of complex 2. Thermal
ellipsoids at the 50% level are shown. Hydrogen atoms are
omitted for clarity.
F igu r e 2. Calculated structure of the cationic active
species generated from neutral complex 1.
to 165.47(4)° (Cl-Ti-iN). The five-membered chelate
rings are substantially flat and appear not to be
significantly strained. The phenyl group on iN swings
out of the plane formed by the chelate ring, making
dihedral angles of 50.8(2) and 55.1(3)°, the values being
in good accordance with those predicted by DFT calcula-
tions.
The catalytically active species derived from group 4
transition-metal complexes is known to be an alkyl
cationic complex.21 The results of DFT calculations on
a methyl cationic complex generated from complex 1,
an initially active species derived from complex 1 with
MAO for ethylene polymerization, indicate that the
cationic complex has cis-located active sites; a methyl
group and a coordinated ethylene are in a cis configu-
ration (77.4°) and are trans to the iN’s (Figure 2). Thus,
the stereochemical relationship between the active sites
and the iN’s of the active species generated from
complex 1 is the same as that for the active species of
highly active group 4 transition-metal complexes having
two phenoxy-imine chelate ligands,15 which has cis-
located active sites trans to the iN’s. The results of DFT
calculations as well as X-ray analysis suggest that
complex 1 has a high potential for olefin polymerization.
Str u ctu r es of Com plexes 2-4. The molecular struc-
tures of complexes 2 and 4 were also elucidated by X-ray
analyses. ORTEP views for complexes 2 and 4 are
shown in Figures 3 and 4, and crystallographic details
and selected bond distances and angles are listed in
Tables 1 and 2. The molecular structures of complexes
2 and 4 are very similar to that of complex 1, suggesting
that substituents on iN give rise to no significant
structural change of the complex. We assume that
complex 3 adopts the similar structure.
F igu r e 4. X-ray structure of complex 4. Thermal ellipsoids
at the 50% level are shown. Hydrogen atoms are omitted
for clarity.
Ta ble 3. Eth ylen e P olym er iza tion Resu ltsa
activity
yield
(g)
(kg of polymer/
((mol of Ti) h))
entry
complex
Mv
cocatalyst MAO
1
2
3
4
5
1
2
3
4
0.50
0.03
0.07
1.18
1.39
6000
400
800
14 100
16 700
75 000
412 000
441 000
2 601 000
1 253 000
Cp2TiCl2
cocatalyst Ph3CB(C6F5)4/i-Bu3Al
6
7
8
9
10
1
2
3
4
0.16
0.14
0.13
0.17
0.29
1900
1700
1500
2000
3500
4 739 000b
4 654 000b
4 901 000b
4 029 000b
773 000
Cp2TiCl2
a
Conditions: ethylene atmospheric pressure; ethylene gas flow,
100 L/h; toluene, 250 mL; polymerization temperature, 25 °C;
polymerization time, 5 min; complex, 1 µmol; cocatalyst MAO
(purchased from Albemarle), 1.25 mmol; Ph3CB(C6F5)4, 6 µmol;
b
i-Bu3Al, 0.25 mmol. Polymer did not dissolve completely in
decalin under the intrinsic viscosity measurement conditions.
These values were obtained from the polyethylene soluble in
decalin under the intrinsic viscosity measurement conditions.
Eth ylen e P olym er iza tion . Ethylene polymerization
behavior of complexes 1-4 were investigated in toluene
at 25 °C using MAO as a cocatalyst under ethylene at
atmospheric pressure. Polymerization results are sum-
marized in Table 3. Complex 1 (R ) Ph) displayed an
activity of 6000 kg of polymer/((mol of Ti) h). This
activity is very high for a titanium complex having no
Cp ligands, under atmospheric pressure conditions. The
(21) (a) Tjaden, E. B.; J ordan, R. F. Macromol. Symp. 1995, 89, 231.
(b) Tjaden, E. B.; Swenson, D. C.; J ordan, R. F. Organometallics 1995,
14, 371.

Ti Complexes with Pyrrolide-Imine Ligands
Organometallics, Vol. 20, No. 23, 2001 4797
viscosity-average molecular weight (Mv) value of the
polymer was 75 000. The molecular weight distribution
(Mw/Mn) of the polyethylene was 2.21 (Mn ) 30 000, Mw
) 67 000, GPC), indicating that the polymer is produced
by a single-site catalyst. Complexes 2 and 3 (2, R ) Et;
3, R ) n-hexyl) exhibited lower activities of 400 and 800
kg of polymer/((mol of Ti) h) with high Mv values of
412 000 and 441 000, respectively. Interestingly, com-
plex 4 (R ) cyclohexyl) showed a very high activity of
14 100 kg of polymer/((mol of Ti) h) with a very high
Mv value of 2 601 000.22-24 To our knowledge, the
activity, 14 100 kg of polymer/((mol of Ti) h), represents
one of the highest values reported to date for homoge-
neous titanium complexes with no Cp ligand and is
comparable to those of Cp2TiCl2 (entry 5) and titanium
tris(pyrazolyl)borate complexes.10,25,26 The basic trend
observed concerning the activity is that an increase in
the bulk of R group on the iN results in enhanced
activity. The enhancement in activity may be attributed
to the effective separation between the cationic active
species and the anionic cocatalyst as a result of the
attachment of bulkier alkyl substituents to the iN.
Using Ph3CB(C6F5)4/i-Bu3Al as a cocatalyst in the place
of MAO, these complexes provided polyethylenes which
did not dissolve completely in decalin under the intrinsic
viscosity measurement conditions, exhibiting high ac-
tivities (1, 1900 kg of polymer/((mol of Ti) h); 2, 1700
kg of polymer/((mol of Ti) h); 3, 1500 kg of polymer/((mol
of Ti) h); 4, 2000 kg of polymer/((mol of Ti) h)). The Mv
values for the soluble part of the polyethylenes are
4 739 000 (complex 1), 4 654 000 (complex 2), 4 901 000
(complex 3), and 4 029 000 (complex 4), suggesting that
the polyethylenes formed with complexes 1-4/Ph3CB-
(C6F5)4/i-Bu3Al cocatalyst systems are of exceptionally
high molecular weight. Considering the great difference
in molecular weight values obtained using MAO and
Ph3CB(C6F5)4/i-BuAl as cocatalysts, the structures of the
active species may be different depending on the co-
catalyst employed.29
In conclusion, we have prepared new titanium com-
plexes having two nonsymmetric bidentate pyrrolide-
imine chelate ligands using the previously studied
highly active FI Catalysts (group 4 transition-metal
complexes having two phenoxy-imine chelate ligands)
as a guide. X-ray analyses as well as DFT calculations
indicate that these complexes adopt a distorted-octa-
hedral structure with a trans-pN, cis-iN, and cis-Cl
arrangement. An active species generated from complex
1 is suggested by DFT calculations to possess cis-located
active sites trans to the iN’s. While the choice of
cocatalyst system has an effect on the catalytic perfor-
mance of these titanium complexes, the highest activity
obtained with MAO is comparable to that of Cp2TiCl2.
Moreover, the molecular weight values obtained with
Ph3CB(C6F5)4/i-Bu3Al are exceptionally high and are
some of the highest values encountered in homogeneous
olefin polymerization catalysts, including the group 4
metallocene catalysts. The results introduced herein in
combination with our previous results9,15-17 suggest that
group 4 transition-metal complexes bearing two non-
symmetric bidentate ligands are potentially viable
catalysts for olefin polymerization.
(22) Ethylene polymerization results using TiCl4/MAO: activity, 90
kg of polymer/((mol of Ti) h); Mv, 296 000. Polymerization conditons
were the same as those for entries 1-5, except for the catalyst amount
(5 µmol) and polymerization time (30 min).
Exp er im en ta l Section
(23) Ethylene polymerization results using other titanium complexes
having two pyrrolide-imine chelate ligands/MAO are as follows. [2-(4-
CH3O-C6H4-NCH)C4H3N]2TiCl2: activity, 3800 kg of polymer/((mol
of Ti) h); Mv, 271 000. [2-(4-CF 3-C6H4-NCH)C4H3N]2TiCl2; activity,
800 kg of polymer/((mol of Ti) h); Mv, 335 000. [2-(3,5-(CF 3)2-C6H3-
NCH)C4H3N]2TiCl2: activity, 500 kg of polymer/((mol of Ti) h); Mv,
1 191 000. Polymerization conditions were the same as those for entries
1-5. The introduction of 4-CH3O, 4-CF3, and 3,5-(CF3)2 into the phenyl
group resulted in a decrease in activity and an increase in Mv. [2-(4-
CH3O-C6H4-NCH)C4H3N]2TiCl2: overall yield 46%; 1H NMR (270
MHz, CDCl3, δ) 3.78 (t, J ) 7 Hz, 6H, CH3O-), 6.06 (dd, J ) 2 Hz,
2H, pyrrole ring aromatic H), 6.42 (d, J ) 2 Hz, 2H, pyrrole ring
aromatic H), 6.6-7.8 (m, 2H, pyrrole ring aromatic H + 8H, benzene
ring aromatic H + 2H, -CHdN-); FD-mass m/z 516 (M+). Anal. Calcd
for C24H22N4TiCl2: C, 53.57; H, 4.50; N, 11.36. Found: C, 53.52; H,
4.35; N, 11.69. [2-(4-CF 3-C6H4-NCH)C4H3N]2TiCl2: overall yield 46%;
1H NMR (270 MHz, CDCl3, δ) 6.18 (dd, J ) 2 Hz, 2H, pyrrole ring
aromatic H), 6.64 (d, J ) 2 Hz, 2H, pyrrole ring aromatic H), 7.00-
8.00 (m, 2H, pyrrole ring aromatic H + 8H, benzene ring aromatic H
+ 2H, -CHdN-) [Et2O of crystallization, δ 1.20 (t, J ) 5 Hz, 3H, CH3-
), 3.48 (q, J ) 5 Hz, 2H, -CH2-)]; FD-mass m/z 592 (M+). Anal. Calcd
for C24H16F6N4TiCl2‚1/2Et2O: C, 49.55; H, 3.36; N, 8.89. Found: C,
49.92; H, 3.37; N, 9.42. [2-(3,5-(CF 3)2-C6H3-NCH)C4H3N]2TiCl2:
overall yield 33%; 1H NMR (270 MHz, CDCl3, δ) 6.18 (dd, J ) 2 Hz,
2H, pyrrole ring aromatic H), 6.64 (d, J ) 2 Hz, 2H, pyrrole ring
aromatic H), 7.36 (s, 4H, benzene ring aromatic H), 7.62 (d, J ) 2 Hz,
2H, pyrrole ring aromatic H), 7.80 (s, 2H, benzene ring aromatic H),
7.90 (s, 2H, -CHdN-); FD-mass m/z 728 (M+). Anal. Calcd for
C26H14F12TiCl2: C, 42.83; H, 1.94; N, 7.68. Found: C, 42.52; H, 2.13;
N, 7.91.
Gen er a l Com m en ts. All manipulations of air- and/or
water-sensitive compounds were performed under a dry ni-
trogen atmosphere using standard Schlenk techniques or in a
dry nitrogen glovebox.
Dried solvents (ethanol, diethyl ether, tetrahydrofuran
(THF), dichloromethane (CH2Cl2), and n-hexane) used for
ligand and complex syntheses were purchased from Wako Pure
Chemical Industries, Ltd., and used without further purifica-
tion. Aniline derivatives and pyrrole-2-carboxaldehyde were
purchased from Tokyo Kasei Kogyo Co., Ltd. An n-butyllithium
hexane solution and TiCl4 were obtained from Kanto Chemical
Co., Inc. and Aldrich Chemical Co., Inc., respectively.
Toluene used as a polymerization solvent (Wako Pure
Chemical Industries, Ltd.) was dried over Al2O3. Methanol and
isobutyl alcohol were purchased from Wako Pure Chemi-
cal Industries, Ltd. Ethylene was purchased from Sumitomo
Seika Co., Ltd. Methylalumoxane (MAO) was obtained from
Albemarle as a 1.2 M toluene solution, and the remaining
trimethylaluminum was evaporated in vacuo prior to use.
Cp2TiCl2 (Tokyo Kasei Kogyo Co., Ltd.), i-Bu3Al (Tosoh-Akuzo
Co., Ltd.), and Ph3CB(C6F5)4 (Asahi Glass Co., Ltd.) were used
as received.
(24) For propylene polymerization at 25 °C at atmospheric pressure,
the complex 4/MAO produced syndiotactic-rich polymer with low
activity.
(27) Warren, T. H.; Schrock, R. R.; Davis, W. M. Organometallics
1996, 15, 562.
(28) Gue´rin, F.; McConville, D. H.; Vittal, J . Organometallics 1996,
15, 5586.
(29) One possible explanation for the Mv difference is that, in the
case of Ph3CB(C6F5)4/i-Bu3Al cocatalyst, the pyrrolide-imine ligand
of the complex is converted to a pyrrolide-amine ligand by the
reduction with i-Bu3Al and/or its contaminant aluminum hydride
compounds. The reduction of an imine to an amine has been observed
for Ti or Zr complexes having two phenoxy-imine ligands/Ph3CB-
(C6F5)4/i-Bu3Al catalyst systems.15k,l
(25) Although the corresponding zirconium complexes possess prac-
tically the same molecular structure, they display considerably lower
activities for the polymerization of ethylene under the same or similar
conditions.19,26 It is likely that strong binding of the cocatalyst to the
electrophilic zirconium metal center27,28 may result in reducing space
for ethylene’s coordination to the metal and its insertion into the
metal-carbon bond.
(26) Yoshida, Y.; Matsui, S.; Nitabaru, M.; Fujita, T. Unpublished
results.

4798 Organometallics, Vol. 20, No. 23, 2001
Yoshida et al.
1H NMR spectra were recorded on a J EOL270 spectrometer
in CDCl3 with tetramethylsilane as the internal standard at
ambient probe temperature (25 °C). Chemical shifts were
reported in δ units.
FD-MS spectra were recorded on an SX-102A from J apan
Electron Optics Laboratory Co., Ltd.
as eluent to afford a flesh-colored solid. Recrystallization from
n-hexane gave 1 as a flesh-colored powder in 65% yield (5.98
1
g, 35.2 mmol). H NMR (270 MHz, CDCl3, δ): 6.30 (dd, J ) 2
Hz, 1H, pyrrole ring aromatic H), 6.69 (d, J ) 2 Hz, 1H, pyrrole
ring aromatic H), 6.89 (d, J ) 2 Hz, 1H, pyrrole ring aromatic
H), 7.1-7.5 (m, 5H, benzene ring aromatic H), 8.29 (s, 1H,
-CHdN-), 9.85 (br s, 1H, pyrrole ring NH). FD-mass: m/z
170. Anal. Calcd for C11H10N2: C, 77.62; H, 5.92; N, 16.46.
Found: C, 77.73; H, 5.84; N, 16.33.
Elemental analysis for CHN was performed by a CHNO type
from Helaus Co.
All calculations were performed using the gradient-corrected
density functional method BLYP, by means of the Amsterdam
Density Functional (ADF ver2.3.0) program.30 For geometry
optimizations, we used a triple-ú basis set on Ti and a double-ú
STO basis set on N, Cl, and atoms constituting the ethylene
and methyl group as a polymer model. A single-ú STO basis
set was employed on the other atoms. For energy calculations,
a triple-ú STO basis set on Ti and a double-ú plus polarization
STO basis set on the other atoms are used and the quasi-
relativistic correction is also added.
[2-(P h NCH)C4H3N]2TiCl2 (1). To a stirred solution of 1a
(1.035 g, 6.08 mmol) in dried diethyl ether (15.5 mL) at -78
°C was added dropwise a 1.54 M n-butyllithium hexane
solution (4.15 mL, 6.38 mmol) over a 5 min period. The mixture
was warmed to room temperature and stirred for 4 h. The
resulting mixture was added dropwise over a 30 min period
to a 0.5 M n-heptane solution of TiCl4 (6.08 mL, 3.04 mmol)
in dried diethyl ether (15.5 mL) at -78 °C with stirring. The
mixture was warmed to room temperature and stirred for 12
h. Then, the reaction mixture was filtered through a glass
filter, and the filtrate was concentrated in vacuo to give a solid.
Dried diethyl ether (20 mL) was added to the solid, and the
mixture was stirred for 10 min and filtered. The filtrate was
concentrated in vacuo to yield a black solid. CH2Cl2 (5 mL)
and n-hexane (10 mL) were added to the solid, and the mixture
was stirred for 1 h and then filtered. Evaporation of the solvent
gave 1 (1.10 g, 2.40 mmol) as a black solid in 79% yield. 1H
NMR (270 MHz, CDCl3, δ): 6.0-7.9 (m, 6H, pyrrole ring
aromatic H + 10H, benzene ring aromatic H), 7.80 (s, 2H,
-CHdN-). FD-mass: m/z 456 (M+). Anal. Calcd for C22H18N4-
TiCl2: C, 57.80; H, 3.97; N, 12.25. Found: C, 58.29; H, 3.95;
N, 12.62.
Single crystals of complex 1, 2, and 4 suitable for X-ray
analysis were grown from hexane/CH2Cl2 solutions. Details of
the crystal data are listed in Table 1.
Data collection for complex 1 was performed on a Rigaku
AFC7R diffractometer with graphite-monochromated Mo KR
radiation at 296 K. The data were corrected for Lorentz and
polarization effects, but no decay collection was applied. The
structure was solved by direct methods (SIR92)31 and expanded
using Fourier techniques (DIRDIF94).32 The non-hydrogen
atoms were refined anisotropically. Hydrogen atoms were
refined isotropically.
Data collections for complex 2 and 4 performed made on a
Rigaku RAXIS-IV imaging plate diffractometer with graphite-
monochromated Mo KR radiation at 150 K. The data were
corrected for Lorentz and polarization effects, but no decay
collection was applied. The structure was solved by heavy-atom
Patterson methods (PATTY)33 and expanded using Fourier
techniques (DIRDIF94).32 The non-hydrogen atoms were re-
fined anisotropically. Hydrogen atoms were included but not
refined.
All calculations were performed using the teXsan crystal-
lographic software package34 of Molecular Structure Corp.
Intrinsic viscosity [η] was measured in decalin at 135 °C
using an Ubbelohde viscometer (polyethylene 25 mg/decalin
25 mL). Viscosity average molecular weight (Mv) values of
polyethylenes were calculated from the equation [η] ) (6.2 ×
10-4)Mv0.7. The molecular weight distribution (Mw/ Mn) value
of polyethylene was determined using a Waters 150-C gel
permeation chromatograph at 145 °C using polyethylene cali-
bration and equipped with three TSKgel columns (two sets of
TSKgelGMHHR-H(S)HT and TSKgelGMH6-HTL). o-Dichloro-
benzene was employed as a solvent at a flow rate of 1.0 mL/
min.
Com plex Syn th esis. 2-(P h NCH)C4H3NH (1a). To a stirred
solution of pyrrole-2-carboxyaldehyde (5.07 g, 53.3 mmol) in
dried ethanol (150 mL), aniline (4.96 g, 53.3 mmol) and formic
acid (1 mL), as a catalyst, were added. The reaction mixture
was stirred for 72 h at room temperature. Evaporation of the
ethanol gave a solid residue, which was purified by column
chromatography on silica gel using hexane/ethyl acetate (9/1)
2-(EtNCH)C4H3NH (2a ). 2a was prepared using a proce-
dure similar to that for 1a . 1H NMR (270 MHz, CDCl3, δ): 1.26
(t, J ) 7 Hz, 3H, CH3-), 3.56 (q, J ) 7 Hz, 2H, -CH2-), 6.26
(dd, J ) 2 Hz, 1H, aromatic H), 6.43 (d, J ) 2 Hz, 1H, aromatic
H), 6.89 (d, J ) 2 Hz 1H, aromatic H), 8.13 (s, 1H, -CHdN-
), 9.20 (br s, 1H, pyrrole ring NH). FD-mass: m/z 122. Anal.
Calcd for C7H10N2: C, 68.82; H, 8.25; N, 22.93. Found: C,
68.39; H, 8.30; N, 23.12.
[2-(EtNCH)C4H3N]2TiCl2 (2). 2 was prepared using a
procedure similar to that for 1. 1H NMR (270 MHz, CDCl3, δ):
1.05 (t, J ) 7 Hz, 6H, CH3-), 3.09 (q, J ) 7 Hz, 4H, -CH2-),
6.30 (dd, J ) 2 Hz, 2H, aromatic H), 6.58 (d, J ) 2 Hz, 2H,
aromatic H), 7.80 (d, J ) 2 Hz, 2H, aromatic H), 8.00 (s, 2H,
-CHdN-). FD-mass: m/z 360 (M+). Anal. Calcd for C14H18N4-
TiCl2: C, 46.57; H, 5.02; N, 15.52. Found: C, 47.01; H, 4.97;
N, 15.94.
2-(n -h exyl-NCH)C4H3NH (3a ). 3a was prepared using a
1
procedure similar to that for 1a . H NMR (270 MHz, CDCl3,
δ): 0.90 (d, J ) 7 Hz, 3H, CH3-), 1.30 (m, 6H, n-hexyl H),
1.65 (dd, J ) 7 Hz, 2H, n-hexyl H), 3.52 (t, 2H, J ) 7 Hz,
n-hexyl H), 6.24 (dd, J ) 2 Hz, 1H, aromatic H), 6.45 (d, J )
2 Hz, 1H, aromatic H), 6.88 (d, J ) 2 Hz, 1H, aromatic H),
8.08 (s, 1H, -CHdN-), 9.48 (br s, 1H, pyrrole ring NH). FD-
mass: m/z 178. Anal. Calcd for C11H18N2: C, 74.11; H, 10.18;
N, 15.71. Found: C, 73.95; H, 10.93; N, 15.99.
[2-(n -h exyl-NCH)C4H3N]2TiCl2 (3). 3 was prepared by the
procedure outlined for 1. The yield was 37%. 1H NMR (270
MHz, CDCl3, δ): 0.8-1.6 (m, 22H, n-hexyl H), 2.7-3.3 (m, 4H,
n-hexyl H), 6.30 (dd, J ) 2 Hz, 2H, aromatic H), 6.58 (d, J )
2 Hz, 2H, aromatic H), 7.80 (d, J ) 2 Hz, 2H, aromatic H),
7.88 (s, 2H, -CHdN-). FD-mass: m/z 472 (M+). Anal. Calcd
for C22H34N4TiCl2: C, 55.83; H, 7.24; N, 11.84. Found: C,
55.49; H, 7.04; N, 12.23.
(30) Guerra, C. F.; Snijders, J . G.; te Velde, G.; Baerends, E. J . Theor.
Chem. Acta 1998, 99, 391.
(31) SIR92: Altomare, A.; Cascarano, M.; Giacovazzo, C.; Guagliardi,
A. J . Appl. Crystallogr. 1994, 26, 343.
(32) DIRDIF94: Beurskens, P. T.; Admiraal, G.; Beurskens, G.;
Bosman, W. P.; de Gelder, R.; Israel, R.; Smits, J . M. M. In The
DIRDIF-94 Program System; Technical Report of the Crystallography
Laboratory; University of Nijmegen, Nijmegen, The Netherlands, 1994.
(33) PATTY: Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bos-
man, W. P.; de Gelder, R.; Israel, R.; Smits, J . M. M. In The DIRDIF-
94 Program System; Technical Report of the Crystallography Labo-
ratory; University of Nijmegen, Nijmegen, The Netherlands, 1994.
(34) teXsan: Crystal Structure Analysis Package; Molecular Struc-
ture Corpo., The Woodlands, TX, 1985 and 1999.
2-(cycloh exyl-NCH)C4H3NH (4a ). 4a was prepared using
a procedure similar to that for 1a . 1H NMR (270 MHz, CDCl3,
δ): 1.1-1.9 (m, 10H, cyclohexyl H), 3.0-3.2 (m, 1H, cyclohexyl
H), 6.21 (dd, J ) 2 Hz, 1H, aromatic H), 6.48 (d, J ) 2 Hz, 1H,
aromatic H), 6.89 (d, J ) 2 Hz, 1H, aromatic H), 8.13 (s, 1H,
-CHdN-), 8.35 (br s, 1H, pyrrole ring NH). FD-mass: m/z:

Ti Complexes with Pyrrolide-Imine Ligands
Organometallics, Vol. 20, No. 23, 2001 4799
176. Anal. Calcd for C11H16N2: C, 74.96; H, 9.15; N, 15.89.
Found: C, 74.54; H, 9.31; N, 15.93.
mL, 0.25 mmol), a 0.002 M solution of complex in toluene (0.5
mL, 1 µmol), and then a 0.002 M solution of Ph3CB(C6F5)4 in
toluene (3 mL, 6 µmol) were added, in this order, into the
reactor.
[2-(cycloh exyl-NCH)C4H3N]2TiCl2 (4). 4 was prepared by
the procedure outlined for 1. The yield was 38%. 1H NMR (270
MHz, CDCl3, δ): 0.7-2.7 (m, 22H, cyclohexyl H), 6.28 (dd, J
) 2 Hz, 2H, aromatic H), 6.60 (d, J ) 2 Hz, 2H, aromatic H),
7.80 (d, J ) 2 Hz, 2H, aromatic H), 8.00 (s, 2H, -CHdN-).
FD-mass: m/z 468 (M+). Anal. Calcd for C22H30N4TiCl2: C,
56.31; H, 6.44; N, 11.94. Found: C, 56.79; H, 6.71; N, 12.12.
Eth ylen e P olym er iza tion . Ethylene polymerization was
performed in a glass flask (500 mL) equipped with a mechan-
ical stirrer, a temperature probe, and a condenser. Toluene
(250 mL) was introduced to the nitrogen-purged reactor and
stirred 600 rpm. The solvent was kept at the prescribed
polymerization temperature, and then the ethylene gas feed
(100 L/h) was started. After 10 min, polymerization was
initiated by the addition of 1.25 M solution of MAO in toluene
(1 mL, 1.25 mmol) and then a 0.002 M solution of a complex
in toluene (0.5 mL, 1 µmol) into the reactor. The polymeriza-
tion was quenched after the prescribed time by the addition
of isobutyl alcohol (5 mL). The resulting mixture was added
to the acidic methanol (1000 mL including 5 mL of concen-
trated HCl). The polyethylene was collected by filtration,
washed with methanol, and then dried at 80 °C in vacuo for
10 h. In the case of using Ph3CB(C6F5)4/i-Bu3Al cocatalyst in
the place of MAO, a 0.5 M solution of i-Bu3Al in toluene (0.5
Ack n ow led gm en t. We thank Dr. T. Oshiki, Okaya-
ma University, for X-ray measurement and analysis. We
also thank Associate Professor K. Mashima, Osaka
University, for his fruitful discussion and suggestions.
We acknowledge stimulating discussions with Dr. M.
Mullins. We also thank M. Nitabaru, J . Saito, Y. Inoue,
Y. Suzuki, S. Ishii, K. Tsuru, N. Matsukawa, J . Mohri,
S. Matsuura, Y. Nakayama, Y. Sonobe, R. Furuyama,
H. Bandoh, H. Terao, S. Kojoh, H. Kaneko, S. Matsuo,
T. Matsugi, K. Sugimura, T. Hayashi, J . S. Harp, A.
Valentine for their research and technical assistance.
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates and
Biso/Beq values, anisotropic displacement
parameters, and bond distances and angles for complexes 1,
2, and 4 and text giving synthetic procedures for complexes
1-4. These materials are available free of charge via the
Internet at http://pubs.acs.org.
OM010468Q