Synthesis of half-titanocenes containing phenoxy-imine ligands and their use as catalysts for olefin polymerization

Article abstract of DOI:10.1021/om700660b

Various half-titanocenes containing phenoxy-imine ligands of the type Cp′TiCl₂[O-2-R¹-6-(R²N=CH)C ₆H₃] [Cp′ = Cp* (C₅Me₅) and R¹, R² = Me, 2,6-ⁱP

Full text of DOI:10.1021/om700660b

Organometallics 2007, 26, 5967-5977
5967
Synthesis of Half-Titanocenes Containing Phenoxy-imine Ligands
and Their Use as Catalysts for Olefin Polymerization
Hao Zhang,†,‡ Shohei Katao,† Kotohiro Nomura,*,† and Jiling Huang*,‡
Graduate School of Materials Science, Nara Institute of Science and Technology,
8916-5 Takayama, Ikoma, Nara 630-0101, Japan, and The Laboratory of Organometallic Chemistry, East
China UniVersity of Science and Technology, 130 Meilong Road, P.O. Box 310,
Shanghai 200237, People’s Republic of China
ReceiVed July 1, 2007
Various half-titanocenes containing phenoxy-imine ligands of the type Cp′TiCl2[O-2-R1-6-(R2NdCH)-
t
t
t
C6H3] [Cp′ ) Cp* (C5Me5) and R1, R2 ) Me, 2,6-iPr2C6H3 (1); Bu, 2,6-iPr2C6H3 (2); Me, Bu (3); Bu,
tBu (4); Cp′ ) 1,2,4-Me3C5H2 and R1, R2 ) Me, 2,6-iPr2C6H3 (5); Cp′ ) Cp and R1, R2 ) Me, 2,6-i-
Pr2C6H3 (6); Me, Bu (7)] were prepared by reaction of Cp′TiCl3 with LiO-2-R1-6-(R2NdCH)C6H3 that
t
were prepared in situ by treating the corresponding phenol with n-BuLi. Cp*TiMe2[O-2-Me-6-{(2,6-i-
Pr2C6H3)NdCH}C6H3](8)waspreparedfromCp*TiMe3 bytreatingwith2-Me-6-{(2,6-iPr2C6H3)NdCH}C6H3-
OH in n-hexane, and the reaction with [PhN(H)Me2][B(C6F5)4] was also explored. Structures for 1-3
and 5-8 were determined by X-ray crystallography, and the imino nitrogen in the phenoxy-imine ligand
was not coordinated to Ti in all cases; the bond angles for Ti-O-C(Ph) were affected by substituents
in both cyclopentadienyl and phenoxy-imine ligands. The catalytic activities for ethylene polymerization
and syndiospecific styrene polymerization using 1-7-MAO catalyst systems were highly affected by
the substituents in both cyclopentadienyl and phenoxy-imine ligands; the Cp* analogues (3, 4) exhibited
notable activities for ethylene polymerization, whereas the Cp analogues (6, 7) showed significant activities
for syndiospecific styrene polymerization. The Cp analogue 6 was also an effective catalyst precursor
for copolymerization of ethylene with norbornene.
of new polymers that are not prepared by conventional Ziegler-
Natta catalysts, as well as by ordinary metallocene type1-4 and/
or “constrained geometry” (linked Cp-amide) type catalysts.4,5
Moreover, the synthesis is not very complicated, and the ligand
modifications sterically and/or electronically should be easier
especially than those in the ordinary linked half-metallocene-
type complexes. We reported that the half-titanocenes containing
Introduction
Design and synthesis of efficient transition metal complex
catalysts toward precise, controlled olefin polymerization has
attracted considerable attention,1-8 and nonbridged half-met-
allocene-type group 4 transition metal complexes of the type
Cp′M(L)X2 (Cp′ ) cyclopentadienyl group; M ) Ti, Zr, Hf; L
) anionic ligand such as OAr, NR2, NdCR2, NdPR3, etc.; X
) halogen, alkyl) have been considered as one of the promising
candidates for new efficient catalysts.8b,9-18 This is because these
complex catalysts exhibit unique characteristics for production
(11) (a) Stephan, D. W.; Stewart, J. C.; Gue´rin, F.; Spence, R. E. v. H.;
Xu, W.; Harrison, D. G. Organometallics 1999, 18, 1116. (b) Stephan, D.
W.; Stewart, J. C.; Brown, S. J.; Swabey, J. W.; Wang, Q. EP881233 A1.
1998. (c) Yue, N.; Hollink, E.; Guerin, F.; Stephan, D. W. Organometallics
2001, 20, 4424. (d) Stephan, D. W.; Stewart, J. C.; Guerin, F.; Courtenay,
S.; Kickham, J.; Hollink, E.; Beddie, C.; Hoskin, A.; Graham, T.; Wei, P.;
Spence, R. E. v. H.; Xu, W.; Koch, L.; Gao, X.; Harrison, D. G.
Organometallics 2003, 22, 1937. (e) Stephan, D. W. Organometallics 2005,
24, 2548.
* Corresponding authors. Fax: +81-743-72-6049. E-mail: nomurak@
ms.naist.jp (Nomura). Fax: +86-21-5428-2375. E-mail: qianling@online.sh.cn
(Huang).
† Nara Institute of Science and Technology.
‡ East China University of Science and Technology.
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10.1021/om700660b CCC: $37.00 © 2007 American Chemical Society
Publication on Web 10/19/2007

5968 Organometallics, Vol. 26, No. 24, 2007
Zhang et al.
Scheme 1
an aryloxo ligand of the type Cp′TiCl2(OAr) (Cp′ ) substituted
cyclopentadienyl; OAr ) aryloxo) exhibited notable catalytic
activities for olefin polymerization,18a,b and we demonstrated
later that a series of these complexes (containing aryloxo, amide,
ketimide ligands) displayed unique characteristics especially for
copolymerization of ethylene with R-olefin,18b,d,19,20 styrene,21
and norbornene.22a,b It was revealed that an efficient catalyst
for desired polymerization can be simply modified by replace-
ment of both the cyclopentadienyl fragment and anionic ancillary
ligands.8b More recently, we had shown that efficient copoly-
merizations of ethylene with cyclohexene (CHE),22c 2-methyl-
1-pentene (2M1P),23 and vinylcyclohexane24 had been achieved
by using these complex catalysts.
Recently, we (group of Qian and Huang)25 and Bochmann26
reported synthesis of half-titanocenes containing phenoxy-imine
ligands (e.g., CpTiCl2[O-2-tBu-6-(RNdCH)C6H3], R ) 2,4,6-
Me3C6H2, C6F5, C6H11,26 etc.) and their use as the catalyst
precursors for olefin polymerization. Since studies concerning
synthesis of various titanium/zirconium complexes containing
bis(phenoxy-imine) ligands for olefin polymerization were made
known by Fujita et al.,27,28 we prepared a series of half-
titanocenes containing substituted cyclopentadienyl and phe-
noxy-imine ligands and tested them as catalyst precursors for
homo- and copolymerization of ethylene with various co-
monomers.
Results and Discussion
1. Synthesis of Various (Cyclopentadienyl)(phenoxy-imi-
ne)titanium Complexes of the Type Cp′TiX2[O-2-R1-6-
(R2NdCH)C6H3] (X ) Cl, Me). A series of substituted
salicylaldimines (imino-phenols), 2-R1-6-(R2NdCH)C6H3OH
t
t
t
[R1, R2 ) Me, 2,6-iPr2C6H3; Bu, 2,6-iPr2C6H3; Me, Bu; Bu,
tBu], were prepared according to the reported procedures, by
reaction of alkyl-substituted salicylaldehyde with 2,6-diisopro-
pylaniline or tert-butylamine, respectively (Scheme 1).27a Vari-
ous half-titanocenes containing phenoxy-imine ligands of the
type Cp′TiCl2[O-2-R1-6-(R2NdCH)C6H3] [Cp′ ) Cp* (C5Me5)
and R1, R2 ) Me, 2,6-iPr2C6H3 (1); tBu, 2,6-iPr2C6H3 (2); Me,
(19) Nomura, K.; Komatsu, T.; Imanishi, Y. J. Mol. Catal. A 2000, 152,
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3797. (b) Wang, W.; Tanaka, T.; Tsubota, M.; Fujiki, M.; Yamanaka, S.;
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Nomura, K. J. Am. Chem. Soc. 2005, 127, 4582.
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tBu (3); Bu, Bu (4); Cp′ ) 1,2,4-Me3C5H2 and R1, R2 ) Me,
t
t
2,6-iPr2C6H3 (5); Cp′ ) Cp and R1, R2 ) Me, 2,6-iPr2C6H3 (6);
t
Me, Bu (7)] were prepared in Et2O by reaction of Cp′TiCl3
with LiO-2-R1-6-(R2NdCH)C6H3, which were prepared in situ
by treating the corresponding phenol with 1.0 equiv of n-BuLi
in Et2O (Scheme 1). Analytically pure samples were collected
as red microcrystals in moderate yields (50.6-72.5%) from a
concentrated dichloromethane solution layered with n-hexane
at -30 °C. The resultant dichloro complexes (1-7) were
identified by 1H and 13C NMR spectra and elemental analyses,
and the structures (for 1-3, 5-7) were determined by X-ray
crystallography as described below (Figures 1 and 2).
The H and 13C NMR spectra for 1-7 were analogous to
1
those reported previously.25-27 For instance, a resonance
ascribed to the imino protons in 1 was observed at 8.54 ppm,
which is slightly downfield from that in the corresponding free
imino phenol (8.28 ppm); a resonance ascribed to the imino
carbon in 1 was observed at 156.9 ppm, whereas the resonance
in the free ligand was observed at 159.2 ppm.
ThedimethylanalogueCp*TiMe2[O-2-Me-6-{(2,6-iPr2C6H3)Nd
CH}C6H3] (8) was prepared in high yield (92%) from Cp*TiMe3
bytreatingwith1.0equivof2-Me-6-{(2,6-iPr2C6H3)NdCH}C6H3-
OH in n-hexane (Scheme 2). The complex 8 was also identified
by H and 13C NMR spectra and elemental analysis, and the
1
structure was determined by X-ray crystallography (Figure 3).
A resonance corresponding to protons for Ti-Me was observed
as one singlet at 0.73 ppm (in C6D6), although the ortho-
substituents in the phenoxy ligand in 8 were different (Me and
the substituted imino), and no significant changes in the
resonance in the 1H NMR spectra (in C6D5CD3) were observed
even at various temperatures (-60 to 60 °C); this was somewhat
different from that in, for example, CpTiMe2(O-2-Np-4,6-t-
Bu2C6H2) (Np ) 1-naphthyl),29 where two resonances ascribed
to Ti-Me were observed. These results suggest that the imino
nitrogen was not coordinated to Ti as described below.
(28) (a) Yoshida, Y.; Matsui, S.; Takagi, Y.; Mitani, M.; Nakano, T.;
Tanaka, H.; Kashiwa, N.; Fujita, T. Organometallics 2001, 20, 4793. (b)
Yoshida, Y.; Saito, J.; Mitani, M.; Takagi, Y.; Matsui, S.; Ishii, S.; Nakano,
T.; Kashiwa, N.; Fujita, T. Chem. Commun. 2002, 1298. (c) Yoshida, Y.;
Mohri, J.; Ishii, S.; Mitani, M.; Saito, J.; Matsui, S.; Makio, H.; Nakano,
T.; Tanaka, H.; Onda, M.; Yamamoto, Y.; Mizuno, A.; Fujita, T. J. Am.
Chem. Soc. 2004, 126, 12023.
(29) Thorn, M. G.; Vilardo, J. S.; Fanwick, P.E.; Rothwell, I. P. Chem.
Commun. 1998, 2427.

Half-Titanocenes Containing Phenoxy-imine Ligands
Organometallics, Vol. 26, No. 24, 2007 5969
Figure 1. ORTEP drawings for Cp*TiCl2[O-2-R1-6-(R2NdCH)C6H3]. R1, R2 ) (a) Me, 2,6-iPr2C6H3 (1), (b) tBu, 2,6-iPr2C6H3 (2), (c) Me,
tBu (3). Thermal ellipsoids are drawn at the 50% probability level and H atoms are omitted for clarity.
Reaction of the dimethyl analogue (8) with [PhN(H)Me2]-
[B(C6F5)4] was explored in C6D5Br, and the protons corre-
sponding to the Me group in the 2,6-iPr2C6H3 group showed
distances and angles are summarized in Table 1. The structure
showed that 1 has a distorted tetrahedral geometry around the
titanium metal center. The Ti-O bond distance in 1 [1.7968-
(16) Å] is slightly longer than those in Cp′TiCl2(O-2,6-iPr2C6H3)
1
two doublets in the H NMR spectrum. Only one resonance
t
corresponding to the Me group was seen at 0.93 ppm, which is
different from that in 8 (0.74 ppm). Moreover the 19F NMR
showed three resonances ascribed to F atoms in the ortho-,
meta-, and para-positions. Although no significant changes were
seen in the resonances ascribed to protons in the phenyl groups
in addition to protons ascribed to PhNMe2, these results presume
the formation of the cationic complex {Cp*TiMe[O-2-Me-6-
{(2,6-iPr2C6H3)NdCH}C6H3]}+[B(C6F5)4]- in situ, although we
could not isolate the complex in a pure form.30
[1.760(4)-1.773(2) Å, Cp′ ) Cp, BuC5H4, Cp*]18a,b and
Cp*TiCl2(O-2,6-Me2C6H3) [1.785(2) Å],31 but are close to those
in Cp*TiCl2(O-2,6-tBu2C6H3) [1.804(2) Å]32 and Cp*TiCl2(O-
(30) A reviewer commented on the possibility of coordination of nitrogen
in the imino group in the proposed cationic complex {Cp*TiMe[O-2-Me-
6-{(2,6-iPr2C6H3)NdCH}C6H3]}+[B(C6F5)4]- and the complex was stabi-
lized by C6D5Br, since there are two isopropyl doublets in the 1H NMR
spectra. However, we could not completely dismiss another possibility,
coordination of PhNMe2, although no significant changes in the resonances
ascribed to the protons were seen. Therefore, K.N. did not describe this
point, although the above assumption would be more likely.
2. Crystal Structure Analysis for Cp′TiX2[O-2-R1-6-
(R2NdCH)C6H3]. The structure for 1 was determined by X-ray
crystallography as shown in Figure 1a, and selected bond
(31) Gomez-Sal, P.; Martin, A.; Mena, M.; Royo, P.; Serrano, R. J.
Organomet. Chem. 1991, 419, 77.

5970 Organometallics, Vol. 26, No. 24, 2007
Zhang et al.
Figure 2. ORTEP drawings for Cp′TiCl2[O-2-Me-6-(R2NdCH)C6H3]. Cp′, R2 ) (a) 1,2,4-Me3C5H2, 2,6-iPr2C6H3 (5), (b) Cp, 2,6-iPr2C6H3
t
(6), (c) Cp, Bu (7). Thermal ellipsoids are drawn at the 50% probability level and H atoms are omitted for clarity.
Scheme 2
2,6-Ph2C6H3) [1.811(3) Å].33 This is explained as due to the
influence of the bulky ortho-substituent, (2,6-iPr2C6H3)NdCH-,
in the phenoxy group. The Ti-Cl distances [2.2643(10), 2.2724-
(13) Å] are similar to those in CpTiCl2(O-2,6-iPr2C6H3) [2.262-
(1) Å],18a,b as well as those in various Cp*TiCl2(OAr) [2.258-
(1)-2.273(6) Å, Ar ) 2,6-Me2C6H3,31 2,6-tBu2C6H3,32 2,6-
Ph2C6H3,33 2,6-Ph2-3,5-tBu2C6H34] except Cp*TiCl2(O-2,6-
iPr2C6H3) [2.305(2) Å].18a,b The Cl-Ti-Cl angle [101.92(5)°]
is slightly smaller than those in Cp*TiCl2(O-2,6-Me2C6H3)
[103.3(2)°]31 and Cp*TiCl2(O-2,6-iPr2C6H3) [103.45(5)°]18a,b and

Half-Titanocenes Containing Phenoxy-imine Ligands
Organometallics, Vol. 26, No. 24, 2007 5971
Figure 3. ORTEP drawings for Cp*TiMe2[O-2-Me-6-{(2,6-iPr2-C6H3)NdCH}C6H3] (8). Thermal ellipsoids are drawn at the 50% probability
level and H atoms are omitted for clarity.
Table 1. Selected Bond Distances (Å) and Angles (deg) for Various Cp*TiCl2[O-2-R1-6-(R2NdCH)C6H3] [R1, R2 ) Me,
t
t
2,6-iPr2C6H3 (1), Bu, 2,6-iPr2C6H3 (2), Me, Bu (3)].
R1, R2
Me, 2,6-iPr2C6H3 (1)
tBu, 2,6-iPr2C6H3 (2)
Me, tBu (3)
Ti(1)-Cl(1)
2.2724(13)
2.2643(10)
1.7968(16)
1.261(3)
1.357(2)
1.421(2)
2.2765(7)
2.2559(8)
1.8001(13)
1.260(2)N(1)-C(17)
1.366(2)
1.426(2)N(1)-C(22)
1.468(2)C(12)-C(17)
102.49(2)
104.31(5)
169.55(13)
2.2596(10)
2.2722(9)
1.808(2)
1.241(4)
1.349(3)
1.469(4)
1.485(4)
104.03(4)
101.10(8)
156.5(2)
102.78(7)
120.8(3)
121.5(3)
Ti(1)-Cl(2)
Ti(1)-O(1)
N(1)-C(18)
O(1)-C(11)
N(1)-C(19)
C(16)-C(18)
1.472(2)
Cl(1)-Ti(1)-Cl(2)
Cl(2)-Ti(1)-O(1)
Ti(1)-O(1)-C(11)
Cl(1)-Ti(1)-O(1)
N(1)-C(18)-C(16)
C(18)-N(1)-C(19)
103.40(4)
102.30(5)
162.16(13)
101.92(5)
122.0(2)
100.23(4)
121.41(18)N(1)-C(17)-C(12)
118.48(18) C(17)-N(1)-C(22)
116.9(2)
larger than those in Cp*TiCl2(O-2,6-tBu2C6H3) [98.10(4)°]31 and
Cp*TiCl2(O-2,6-Ph2C6H3) [98.70(5)°].33 The Ti-O-C(phenyl)
angle [162.16(13)°] is close to that in Cp*TiCl2(O-2,6-Me2C6H3)
[162.3(2)°].29 These results thus indicate that these bond angles
and distances are similar to those in a series of Cp*TiCl2(OAr)
in most cases.
6-(tBuNdCH)C6H3] (3), were also determined by X-ray crys-
tallography (Figures 1b,c, respectively), and selected bond
distances and angles are summarized in Table 1. These
complexes have a distorted tetrahedral geometry around the Ti
metal center, and the imino nitrogens were not coordinated to
Ti. Slight differences in the Ti-O and Ti-Cl bond distances
were seen, but these values are in the same range as in the
various Cp*TiCl2(OAr) introduced above.18a,b,31-34 In contrast,
Ti-O-C(phenyl) bond angles are strongly influenced by the
substituents in both the ortho-phenoxy and the imino
groups, and the bond angle increased in the order 169.55(13)°
Note that the imino-nitrogen was not coordinated to Ti; this
observation is an interesting contrast to that in CpTiCl2[O-2-t-
Bu-6-{(2,4,6-Me3C6H2)NdCH}C6H3] (Ti-N ) 2.268 Å),26
where the Ti atom is five-coordinate with the Cp ligand in the
apical site of a distorted square-pyramid and the N,O-chelating
ligand forms a plane that includes the phenoxide ring and the
imino nitrogen.
t
(2, R1, R2 ) Bu, 2,6-iPr2C6H3) > 162.16(13)° (1, R1, R2 )
Me, 2,6-iPr2C6H3) > 156.5(2)° (3, R1, R2 ) Me, tBu). The bond
angle in 2 is larger than those in ordinary Cp*TiCl2(OAr) [155.5-
(2)-162.3(2)°]31-34 and somewhat similar to that in
The structures for the other Cp* analogues, Cp*TiCl2[O-2-
tBu-6-{(2,6-iPr2C6H3)NdCH}C6H3] (2) and Cp*TiCl2[O-2-Me-
(32) Nomura, K. Tanaka, A.; Katao, S. J. Mol. Catal. A 2006, 254, 197.
(33) Sturla, S. J.; Buchwald, S. L. Organometallics 2002, 21, 739.
(34) Thorn, M. G.; Vilardo, J. S.; Lee, J.; Hanna, B.; Fanwick, P. E.;
Rothwell, I. P. Organometallics 2000, 19, 5636.

5972 Organometallics, Vol. 26, No. 24, 2007
Zhang et al.
Table 2. Selected Bond Distances (Å) and Angles (deg) for Cp′TiCl2[O-2-Me-6-(R2NdCH)C6H3] [Cp′; R2 ) 1,2,4-Me3C5H2,
t
2,6-iPr2C6H3 (5), Cp; 2,6-iPr2C6H3 (6), Cp; Bu (7)]
Cp′ R2
1,2,4-Me3Cp
Cp
Cp
2,6-iPr2C6H3 (5)
2,6-iPr2C6H3 (6)
tBu (7)
Ti(1)-Cl(1)
2.260(2)
2.2623(16)
1.781(3)
2.2546(6)
2.2515(7)
1.7761(14)
1.259(2)N(1)-C(12)
1.363(2)
1.435(2)
1.466(2)C(7)-C(12)
101.79(3)
102.40(4)
166.05(14)
2.2555(4)
2.2592(4)
1.7840(10)
1.2496(17)N(1)-C(13)
1.3633(17)
1.488(2)
1.4751(18)C(11)-C(13)
103.387(19)
103.15(2)
156.40(8)
Ti(1)-Cl(2)
Ti(1)-O(1)
N(1)-C(16)
1.263(6)
O(1)-C(6)
1.370(5)O(1)-C(9)
1.418(6) N(1)-C(17)
1.477(7)
N(1)-C(14)
C(10)-C(16)
Cl(1)-Ti(1)-Cl(2)
Cl(2)-Ti(1)-O(1)
Ti(1)-O(1)-C(6)
Cl(1)-Ti(1)-O(1)
N(1)-C(16)-C(10)
C(16)-N(1)-C(17)
103.53(7)
102.61(11)
171.0(3)Ti(1)-O(1)-C(9)
101.82(13)
121.2(2)
104.87(5)
122.68(18)N(1)-C(12)-C(7)
116.25(17)C(12)-N(1)-C(14)
103.15(2)
121.30(14)N(1)-C(13)-C(11)
119.65(14)C(13)-N(1)-C(14)
121.1(4)
Table 3. Selected Bond Distances (Å) and Angles (deg) for
Cp*TiCl2(O-2,6-iPr2C6H3) [173.0(3)°],18a,b which exhibit notable
catalytic activity for olefin polymerization in the presence of
MAO.
Cp*TiMe2[O-2-Me-6-{(2,6-iPr2-C6H3)NdCH}C6H3] (8)
Bond Distances
Ti(1)-C(1) 2.393(5)
Ti(1)-O(1) 1.813(2)
O(1)-C(13) 1.352(4)
C(18)-C(20) 1.468(4)
Ti(1)-C(2) 2.371(4)
N(1)-C(20) 1.263(5)
N(1)-C(21) 1.415(4)
The structures for Cp′TiCl2[O-2-Me-6-{(2,6-iPr2C6H3)Nd
CH}C6H3] [Cp′ ) 1,2,4-Me3C5H2 (5); Cp′ ) Cp (6)] were also
determined by X-ray crystallography (Figures 2a,b, respectively)
to explore the effect of the cyclopentadienyl fragment by
comparison with 1, and selected bond distances and angles are
summarized in Table 2. Complexes 5 and 6 have a distorted
tetrahedral geometry around the titanium metal center, and the
imino nitrogens were not coordinated to Ti; the results also
showed unique contrast to that in CpTiCl2[O-2-tBu-6-{(2,4,6-
Me3C6H2)NdCH}C6H3].26 The Ti-Cl bond distances for 5 and
6 [2.2515(7)-2.2623(16) Å] are similar or slightly shorter than
those in 1 [2.2643(10) and 2.2724(13) Å], and the Ti-O bond
distances [1.781(3), 1.7761(14) Å for 5, 6, respectively] are
slightly shorter than that in 1 [1.7968(16) Å]. This is explained
as due to an electronic effect in the cyclopentadienyl
fragments, because the Ti-O bond distances increased in the
order 1 (Cp′ ) C5Me5) > 5 (1,2,4-Me3C5H2) > 6 (Cp). In
contrast, the Ti-O-C(phenyl) bond angle increased in the
order 5 [171.0(3)°] > 6 [166.05(14)°] > 1 [162.16(13)°],
although the reason is not clear at this moment. The structure
for CpTiCl2[O-2-Me-6-(tBuNdCH)C6H3] (7) was also
determined, and selected results are summarized in Table 2.
Complex 7 also possesses a distorted tetrahedral geometry
around the titanium metal center, and the imino nitrogen was
not coordinated to Ti. No significant differences in the bond
distances were seen from those in 6, and the Ti-O-C(phenyl)
bond angle [156.40(8)°] is smaller than that in 6 [166.05(14)°]
but similar to that in 3 [156.5(2)°] probably due to the influence
of bulky tert-butyl substituent in the imino group for 3 and 6.
Taking into account these results, we may conclude that the
bond distances and angles [especially Ti-Cl and Ti-O dis-
tances, Ti-O-C(phenyl) angle] are influenced by the substit-
uents in both the cyclopentadienyl and aryloxo (phenoxy-imine)
ligands.
Bond Angles
C(11)-Ti(1)-C(12) 100.86(4)
Ti(1)-O(1)-C(13) 159.1(2)
N(1)-C(20)-C(18) 123.5(3)
C(11)-Ti(1)-O(1) 102.05(15)
C(12)-Ti(1)-O(1) 102.33(13)
C(20)-N(1)-C(21) 117.2(3)
iPr2C6H3]. The Ti-O distance is also slightly longer than in
the dichloro analogue [1, 1.7968(16) Å]. The Ti-O-C(phenyl)
bond angle [159.1(2)°] is smaller than that in Cp*TiMe2(O-
2,6-iPr2C6H3) [168.7(1)°]35 but similar to that in the dichloro
analogue [1, 162.16(13)°].
3. Ligand Effects in Ethylene Polymerization and Syn-
diospecific Styrene Polymerization Using Cp′TiX2[O-2-R1-
6-(R2NdCH)C6H3] (1-8)-MAO Catalyst Systems. Ethylene
polymerizations by Cp′TiCl2[O-2-R1-6-(R2NdCH)C6H3] (1-
7) in the presence of methylaluminoxane (MAO) were examined
to explore the effect of substituents on both the cyclopentadienyl
and the phenoxy-imine ligands toward the catalytic activity
(ethylene 4 atm, 25-70 °C, under the optimized Al/Ti molar
ratio), and the results are summarized in Table 4.
The catalytic activities at 25 °C for ethylene polymerization
using catalyst systems consisting of a series of Cp* analogues,
Cp*TiCl2[O-2-R1-6-(R2NdCH)C6H3] (1-4), and MAO in-
creased in the order (ethylene 4 atm) 11 070 kg PE/mol Ti‚h
(4, R1, R2 ) tBu, tBu, run 9) > 8460 (3, R1, R2 ) Me, tBu, run
t
6) > 6360 (2, R1, R2 ) Bu, 2,6-iPr2C6H3, run 3) > 3540 (1,
R1, R2 ) Me, 2,6-iPr2C6H3, run 1). The results suggest that the
activities are highly affected by the substituents; the bulky
substituents in both the phenoxy group in the ortho-position
(tBu > Me) and the imino group (tBu > 2,6-iPr2C6H3) seem to
be important for high catalytic activity. Both the activities and
the Mw values for resultant polyethylene decreased at higher
temperature. The Cp* analogues showed higher catalytic activi-
ties than the Cp analogues (6, 7) [activities at 25 °C: 3540,
8460 kg PE/mol Ti‚h by 1, 3, respectively, vs 132, 243 kg PE/
mol Ti‚h by 6, 7, respectively], suggesting that an electronic
effect on the Cp′ affects the catalytic activity as seen in the
series Cp′TiCl2(O-2,6-iPr2C6H3) in both ethylene and 1-hexene
polymerizations.18a,b,32 In contrast, the Mw values using the Cp
analogues (6, 7) were higher than those prepared by the Cp*
analogues, although we do not have the exact reason for the
Yellow prism microcrystals of 8 were grown from a
concentrated chilled n-hexane solution, and the structure was
determined by X-ray crystallography (Figure 2). Selected bond
distances and angles are summarized in Table 3. The Ti-C(Me)
bond distances [2.371(14), 2.393(5) Å] as well as the Ti-O
distance [1.813(2) Å] are somewhat longer than those in
Cp*TiMe2(O-2,6-iPr2C6H3) [2.093(3), 2.101(3), and 1.790(2)
Å],35 and this might be due to the influence of the bulky
substituent in 8 [2-Me-6-{(2,6-iPr2C6H3)NdCH}-C6H3 vs 2,6-
(35) Nomura, K.; Fudo, A. Inorg. Chim. Acta 2004, 345, 37.

Half-Titanocenes Containing Phenoxy-imine Ligands
Organometallics, Vol. 26, No. 24, 2007 5973
Table 4. Ethylene Polymerization by
Cp′TiCl2[O-2-R1-6-(R2NdCH)C6H3] (1-8)-MAO Catalyst
Systemsa
Table 5. Syndiospecific Styrene Polymerization by
Cp′TiCl2[O-2-R1-6-(R2NdCH)C6H3] (1-7)-MAO Catalyst
Systemsa
cat.
run (µmol) temp/°C yield/mg
polymer activityb
cat.
polymer
c
c
d
d
Mw ×10-4 Mw/Mn
run (µmol) temp/°C yieldb/mg activityc Mw ×10-4 Mw/Mn
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
1 (0.2)
1 (0.2)
2 (0.2)
2 (0.2)
2 (0.2)
3 (0.2)
3 (0.2)
3 (0.2)
4 (0.2)
4 (0.2)
5 (0.2)
5 (0.2)
6 (2.0)
6 (2.0)
7 (2.0)
7 (2.0)
25
40
25
40
70
25
40
70
25
70
25
40
25
70
25
70
25
118
99
3540
2970
6360
5130
3000
8460
7110
3930
11070
8130
4830
4050
132
2.91
2.57
4.49
3.65
1.14
3.25
2.43
1.93
1.75
1.66
1.45
1.29
1.8
1. 9
2.4
2.2
2.7
2.7
2.7
3.0
2.7
2.4
2.4
2.4
3.1
2.2
3.0
2.9
2.0
18 1 (2.0)
19 1 (2.0)
20 1 (2.0)
21 1 (2.0)
22 2 (2.0)
23 2 (2.0)
24 2 (2.0)
25 2 (2.0)
26 3 (2.0)
27 3 (2.0)
28 4 (2.0)
29 5 (2.0)
30 5 (2.0)
31 5 (2.0)
32 5 (2.0)
33 6 (2.0)
34 6 (2.0)
35 6 (2.0)
36 6 (2.0)
37 7 (2.0)
38 7 (2.0)
39 7 (2.0)
40 7 (2.0)
25
40
55
70
25
40
55
70
55
70
70
25
40
55
70
25
40
55
70
25
40
55
70
47
64
95
184
trace
42
77
126
31
50
trace
44
170
248
298
117
446
665
970
130
546
999
1529
141
192
285
552
19.9
21.3
19.3
18.5
2.2
2.1
2.2
2.3
212
171
100
282
237
131
369
271
161
135
44
126
231
378
93
19.3
18.2
17.1
8.37
8.34
2.3
2.2
2.2
2.2
2.2
150
132
510
744
894
351
1338
1995
2910
390
1638
2997
4587
15.0
2.2
2.2
2.1
2.1
2.1
2.4
2.3
2.5
2.1
2.1
2.1
2.1
109
65.3
224.3
97.1
17.2
14.4
14.3
31
81
36
107
93
243
108
3210
2.67
17d 8(0.2)
2.44
2.47
2.42
1.74
7.55
6.23
5.91
5.84
a Cp′ ) Cp* and R1, R2 ) Me, 2,6-iPr2C6H3 (1), Bu, 2,6-iPrC6H3 (2),
t
Me, Bu (3), Bu, Bu (4); Cp′ ) 1,2,4-Me3C5H2 and R1, R2 ) Me, 2,6-
t
t
t
iPr2C6H3 (5); Cp′, R1 ) Cp, Me and R2 ) 2,6-iPr2C6H3 (6), Bu (7), and
t
Cp*TiMe2[O-2-Me-6-{(2,6-iPr2C6H3)NdCH}C6H3] (8). Conditions: cata-
lyst 0.2 or 2.0 µmol, MAO (prepared by removing AlMe3 and toluene from
PMAO) 3.0 mmol, ethylene 4 atm, toluene total 50 mL, 25 °C, 10 min
(100 mL scale autoclave). b Activity in kg PE/mol Ti‚h. c GPC data in
o-dichlorobenzene vs polystyrene standards. d AliBu3/Ph3CB(C6F5)4/Ti )
500:1:1 (molar ratio).
a Cp′ ) Cp* and R1, R2 ) Me, 2,6-iPr2C6H3 (1), Bu, 2,6-iPrC6H3 (2),
t
t
t
t
Me, Bu (3), Bu, Bu (4); Cp′ ) 1,2,4-Me3C5H2 and R1, R2 ) Me, 2,6-
iPr2C6H3 (5); Cp′, R1 ) Cp, Me and R2 ) 2,6-iPr2C6H3 (6), Bu (7).
t
Conditions: catalyst 2.0 µmol, MAO (prepared by removing AlMe3 and
toluene from PMAO) 3.0 mmol (Al/Ti ) 1500, molar ratio), styrene 10
mL, styrene + toluene total 30 mL, 25 °C, 10 min and 100 mL scale
autoclave. b Yield of acetone-insoluble fraction. c Activity in kg sPS/mol
Ti‚h. d GPC data in o-dichlorobenzene vs polystyrene standards.
better results at this moment.36 The activities of the 1,2,4-
Me3C5H2 analogue (5) were similar to or rather higher than those
of the Cp* analogue (1) under the same conditions (runs 1, 2
vs runs 10, 11).
The observed catalytic activity at 25 °C of the dimethyl
analogue (8)-Ph3CB(C6F5)4 system in the presence of AliBu3
was somewhat similar to that of the dichloro analogue (1) in
the presence of MAO. Since the Mw values for the resultant
polymers prepared by 1 and 8 were close with uniform
distributions (runs 1 and 17), we assume that similar catalytically
active species, Cp′TiR[O-2-Me-6-{(2,6-iPr2C6H3)NdCH}-
C6H3]+ (R ) alkyl), play a role in the ethylene polymerization.
We previously demonstrated that efficient catalyst precursor-
(s) for ethylene (1-hexene) polymerization using the series
Cp′TiCl2(O-2,6-iPr2C6H3) or Cp′TiCl2(NR1R2) in the presence
of MAO can be tuned to efficient catalyst precursor(s) for
syndiospecific styrene polymerization only by modification
(replacement) of the cyclopentadienyl fragment.8b,18d,37 We thus
explored syndiospecific styrene polymerization (at 25-70 °C)
by Cp′TiCl2[O-2-R1-6-(R2NdCH)C6H3] (1-7) to explore the
ligand effects on the catalytic activity. The results are sum-
marized in Table 5.38
possessed rather high molecular weights with uniform molecular
weight distributions in all cases (Mw ) (1.74-21.3) × 104, Mw/
Mn ) 2.06-2.53). The Mw values for resultant syndiotactic
polystyrene prepared by the Cp* analogues (1-3) were higher
than those by the Cp analogues (6, 7), as seen in the previous
report.37b
The catalytic activity at 70 °C using a series of Cp′TiCl2[O-
2-Me-6-{(2,6-iPr2C6H3)NdCH}C6H3]-MAO catalyst systems
increased in the order 6 (Cp′ ) Cp, 2910 kg sPS/mol Ti‚h) >
5 (1,2,4-Me3C5H2, 894) > 1 (Cp*, 552). The results thus clearly
demonstrate that an efficient catalyst precursor for ethylene
polymerization using a series of Cp′TiCl2[O-2-Me-6-{(2,6-i-
Pr2C6H3)NdCH}C6H3] can be tuned to efficient catalyst precur-
sors for syndiospecific styrene polymerization by modification
of the cyclopentadienyl fragment. We believe that the results
presented here show one of the unique characteristics of
nonbridged half-titaniocenes that make them suitable as catalyst
precursors for olefin (styrene) polymerization, as demonstrated
previously.8b
The catalytic activities increased at higher temperature, as
seen previously,37b and the activities at 70 °C were higher than
those at 25 °C; however, complex 4 showed negligible activity.
The resultant polymers were syndiotactic polystyrene (sPS) that
The catalytic activity at 70 °C using a series of Cp*TiCl2-
[O-2-R1-6-(R2NdCH)C6H3]-MAO catalyst systems increased
in the order 1 (R1, R2 ) Me, 2,6-iPr2C6H3, 552 kg sPS/mol
Ti‚h, run 21) > 2 (R1, R2 ) tBu, 2,6-iPr2C6H3, 378, run 25) >
(36) As a reviewer noted, the Mw values for the resultant PEs prepared
by the Cp* analogues [Cp*TiCl2(X) (X ) aryloxo, amide, anilide etc.]-
MAO catalyst systems were generally higher than the Cp analogues, except
the Cp′-ketimide analogues, CpTiCl2(NdCtBu2).8b Although the exact
reason was not clear , the observation might be a promising characteristic
for using the present type of complex for olefin polymerization.
(37) (a) Nomura, K.; Komatsu, T.; Imanishi, Y. Macromolecules 2000,
33, 8122. (b) Byun, D.-J.; Fudo, A.; Tanaka, A.; Fujiki, M.; Nomura, K.
Macromolecules 2004, 37, 5520.
t
t
t
3 (R1, R2 ) Me, Bu, 150, run 27) . 4 (R1, R2 ) Bu, Bu,
trace, run 28). The observed trend was opposite of that in the
ethylene polymerization. Moreover, among the Cp analogues,
CpTiCl2[O-2-R1-6-(R2NdCH)C6H3], activities of 7 (R1, R2 )
tBu, tBu, 4587 kg sPS/mol Ti‚h, run 40) were higher than those
of 6 (R1, R2 ) Me, Bu, 2910, run 36). These facts clearly
t
(38) As reported previously,37 the resultant polymer generally consisted
of (acetone-soluble) atactic polystyrene produced by MAO and (acetone-
insoluble) syndiotactic polystyrene (SPS) prepared by the titanium catalyst.
SPS was isolated as the acetone-insoluble fraction.
suggest that the activities were highly affected by the anionic
donor ligand employed, although the effect should be negligible
if the cationic Ti(III) species are considered as the catalytically

5974 Organometallics, Vol. 26, No. 24, 2007
Zhang et al.
Table 6. Copolymerization of Ethylene with Norbornene (NBE) by Cp′TiCl2[O-2-R1-6-(R2NdC)-C6H3]-MAO Catalyst Systemsa
cat.
(µmol)
NBE concb/
mmol/mL
polymer
yield/mg
NBE cont.d/
mol %
e
e
run
activityc
Mw ×10-4
Mw/Mn
1
41
3
42
43
6
44
45
13
46
47
48
15
49
50
1 (0.2)
1 (5.0)
2 (0.2)
2 (5.0)
2 (5.0)
3 (0.2)
3 (5.0)
3 (5.0)
6 (0.2)
6 (2.0)
6 (5.0)
6 (5.0)
7 (0.2)
7 (5.0)
7 (5.0)
118
359
212
351
116
282
227
159
44
258
621
161
81
3540
431
6360
421
139
8460
272
191
132
774
745
193
243
265
214
2.91
1.65
4.49
1.84
1.35
3.25
1.82
1.18
109
5.01
4.32
3.27
224
1.8
1.9
2.4
2.3
3.1
2.7
2.7
2.6
3.1
2.8
2.4
2.0
3.00
2.8
2.4
0.50
<1.5
5.4
0.20
0.50
0.20
0.50
4.8
0.20
0.50
1.00
7.6
28.1
32.5
0.20
0.50
221
178
4.9
10.1
3.02
2.87
t
t
t
a Cp′ ) Cp* and R1, R2 ) Me, 2,6-iPr2C6H3 (1), Bu, 2,6-iPrC6H3 (2), Me, Bu (3); Cp′, R1 ) Cp, Me and R2 ) 2,6-iPr2C6H3 (6), Bu (7). Conditions:
toluene 50 mL, MAO (prepared by removing AlMe3 and toluene from PMAO) 3.0 mmol, ethylene 4 atm, 25 °C, 10 min. b Norbornene (NBE) concentration
charged. c Activity in kg polymer/mol Ti‚h. d NBE content (mol %) estimated by 13C NMR spectra. e GPC data in o-dichlorobenzene vs polystyrene standards.
Table 7. Copolymerization of Ethylene with 1-Hexene by
active species.39,40 Taking into account the above results, the
Cp′TiCl2[O-2-R1-6-(R2NdC)C6H3]-MAO Catalyst Systemsa
catalytic activity of a series of Cp′TiCl2[O-2-R1-6-(R2NdCH)-
C6H3]-MAO catalyst systems was highly affected by substit-
uents in both the cyclopentadienyl and phenoxy-imine ligands.
cat.
polymer
1-hexene
run (µmol) yield/mg activityb contentc Mw ×10-4 Mw/Mn
d
d
51 1 (5.0)
52 2 (5.0)
53 3 (5.0)
54 5 (5.0)
189
146
184
43
227
175
221
52
3.2
2.7
2.2
0.79
0.56
0.39
0.4
2.9e
2.9e
2.3e
2.5e
4. Copolymerization of Ethylene with Norbornene and
1-Hexene by Cp′TiX2[O-2-R1-6-(R2NdCH)C6H3] (1-7)-
MAO Catalyst Systems. Copolymerizations of ethylene with
norbornene (NBE) using a series of Cp′TiX2[O-2-R1-6-(R2-
NCH)C6H3] (1-3, 6 ,7)-MAO catalyst systems were con-
ducted, because CpTiCl2(NdCtBu2) exhibited both remarkable
catalytic activity and efficient NBE incorporation for ethylene/
NBE copolymerization41 and the activity as well as NBE
incorporations were dependent upon the anionic donor ligand
employed.41 The results are summarized in Table 6.42,43
a Cp′ ) Cp* and R1, R2 ) Me, 2,6-iPr2C6H3 (1), Bu, 2,6-iPrC6H3 (2),
t
t
Me, Bu (3); Cp′ ) 1,2,4-Me3C5H2 and R1, R2 ) Me, 2,6-iPr2C6H3 (5).
Conditions: catalyst 5.0 µmol, toluene 40 mL, MAO (prepared by removing
AlMe3 and toluene from PMAO) 3.0 mmol, ethylene 4 atm, 25 °C, 10
min., 1-hexene, 0.2 mmol/mL. b Activity in kg polymer/mol Ti‚h. c 1-
Hexene content (mol %) estimated by 13C NMR spectra. d GPC data in
o-dichlorobenzene vs polystyrene standards. e Trace amount of high Mw
shoulder (Mw ) 263.4) was observed in the GPC trace.
The catalytic activities of the Cp* analogues (1-3) signifi-
cantly decreased in the presence of NBE; the resultant copoly-
mers possessed low NBE content, suggesting that these com-
plexes showed inefficient NBE incorporation. In contrast, the
catalytic activities of the Cp analogues (6, 7) increased or did
not change in the presence of NBE (NBE 0.50 mmol/mL); 6
showed better NBE incorporation than 7 and the Cp* analogues
(1-3) under the same conditions. These results clearly indicate
that an efficient catalyst precursor for the ethylene copolym-
erization can be tuned to an efficient catalyst precursor for
ethylene/NBE copolymerization by modification of both Cp′
and anionic donor ligands.8b,41
The resultant copolymers especially prepared by the 6-MAO
catalyst system possessed rather high molecular weights with
unimodal molecular weight distributions (runs 46-48); reso-
nances corresponding to the isolated, alternating NBE sequences
in addition to NBE dyads were observed in the 13C NMR spectra
for the resultant poly(ethylene-co-NBE)s.43 The NBE incorpora-
tion by 6 was slightly less efficient than that by CpTiCl2(NdCt-
Bu2) [NBE 40.7-41.5 mol %41 vs 32.5 mol % by 6 (run 48),
ethylene 4 atm, NBE 1.00 mmol/mL], suggesting that 6 is suited
as the catalyst precursor for efficient NBE incorporation.
However, the activity decreased at high NBE concentration (run
48).
(39) Example of a mechanistic study concerning both styrene polymer-
ization and propylene/styrene copolymerization: (a) Grassi, A.; Zambelli,
A.; Laschi, F. Organometallics 1996, 15, 480-482. (b) Mahanthappa, M.
K.; Waymouth, R. M. J. Am. Chem. Soc. 2001, 123, 12093-12904. (c)
Minieri, G.; Corradini, P.; Guerra, G.; Zambelli, A.; Cavallo, L. Macro-
molecules 2001, 34, 5379-5385.
(40) Related mechanistic study concerning syndiospecific styrene po-
lymerization and ethylene/styrene copolymerization: Zhang, H.; Byun, D.-
J.; Nomura, K. Dalton Trans. 2007, 1802.
Copolymerization of ethylene with 1-hexene with the Cp*
and 1,2,4-Me3C5H2 analogues (1-3, 5)-MAO catalyst systems
was conducted, and the results are summarized in Table 7. The
catalytic activities of the Cp* analogues-MAO catalyst systems
decreased in the presence of 1-hexene (runs 51-53), and the
resultant polymers possessed low molecular weights with rather
broad molecular weight distributions. The 1-hexene contents
in the resultant copolymers were low, suggesting that these
complexes were not suited as the catalyst precursor for the
copolymerization; the results are similar to that for CpTiCl2[O-
2,4-tBu2-6-{(C6F5)NdCH}-C6H2] reported previously.26a The
activity of the 1,2,4-Me3C5H2 analogue (5) was low, and those
of the Cp* analogues were higher than that of 1,2,4-Me3C5H2.
In conclusion, we have prepared a series of Cp′TiCl2[O-2-
R1-6-(R2NdCH)C6H3] [Cp′ ) Cp* (C5Me5) and R1, R2 ) Me,
(41) Nomura, K.; Wang, W.; Fujiki, M.; Liu, J. Chem. Commun. 2006,
2659.
(42) Selected examples of copolymerization of ethylene with NBE using
metallocenes and linked half-titanocene including an estimation of NBE
content in the poly(ethylene-co-NBE)s: (a) Provasoli, A; Ferro, D. R.; Tritto,
I.; Boggioni, L. Macromolecules 1999, 32, 6697. (b) Tritto, I.; Marestin,
C.; Boggioni, L.; Zetta, L.; Provasoli, A.; Ferro, D. R. Macromolecules
2000, 33, 8931. (c) Tritto, I.; Marestin, C.; Boggioni, L.; Sacchi, M. C.;
Brintzinger, H.-H.; Ferro, D. R. Macromolecules 2001, 34, 5770. (d) Tritto,
I.; Boggioni, L.; Jansen, J. C.; Thorshaug, K.; Sacchi, M. C.; Ferro, D. R.
Macromolecules 2002, 35, 616. (e) Thorshaug, K.; Mendichi, R.; Boggioni,
L.; Tritto, I.; Trinkle, S.; Friedrich, C.; Mu¨lhaupt, R. Macromolecules 2002,
35, 2903. (f) Tritto, I.; Boggioni, L.; Ferro, D. R. Macromolecules 2004,
37, 9681.
(43) Selected 13C NMR spectra for resultant poly(ethylene-co-NBE)s are
shown in the Supporting Information.
t
t
t
t
2,6-iPr2C6H3 (1); Bu, 2,6-iPr2C6H3 (2); Me, Bu (3); Bu, Bu

Half-Titanocenes Containing Phenoxy-imine Ligands
Organometallics, Vol. 26, No. 24, 2007 5975
ranging from <102 to <2.8 × 108 MW) at 140 °C using
o-dichlorobenzene containing 0.05 wt/v% 2,6-di-tert-butyl-p-cresol
as the solvent. The molecular weight was calculated by a standard
procedure based on the calibration with standard polystyrene
samples.
(4); Cp′ ) 1,2,4-Me3C5H2 and R1, R2 ) Me, 2,6-iPr2C6H3 (5);
t
Cp′ ) Cp and R1, R2 ) Me, 2,6-iPr2C6H3 (6); Me, Bu (7)],
and the structures were determined by X-ray crystallography.
The imino nitrogen atoms in 1-3 and 5-8 were not coordinated
to Ti in all cases, and these are unique contrasts to those reported
previously25-28 and may suggest the presence of an equilibrium
between coordination and dissociation of the nitrogen to Ti in
the catalytic reaction. The bond angles for Ti-O-C(Ph) were
affected by substituents in both the cyclopentadienyl and
phenoxy-imine ligands. The catalytic activities for ethylene
polymerization and syndiospecific styrene polymerization using
1-7-MAO catalyst systems were highly affected by the
substituents in both the cyclopentadienyl and the phenoxy-imine
ligands; the Cp* analogues (3, 4) exhibited remarkable catalytic
activities for ethylene polymerization, whereas the Cp analogues
(6, 7) showed notable catalytic activities for syndiospecific
styrene polymerization. The Cp analogue 6 showed efficient
NBE incorporation in the ethylene/NBE copolymerizations,
whereas the activities of the Cp* analogues decreased in the
presence of NBE. These results suggest that efficient catalyst
precursors for the desired (co)polymerizations can be tuned by
modification (replacement) of the cyclopentadienyl fragment.
Synthesis of Cp*TiCl2[O-2-Me-6-{(2,6-iPr2C6H3)NdCH}-
C6H3] (1). Into a stirred Et2O (10 mL) solution containing 2-Me-
6-(2,6-iPr2C6H3)NdCH-C6H3OH (443 mg, 1.5 mmol), n-BuLi (1.0
mL, 1.58 M in hexane, 1.0 equiv) was added dropwise at -30 °C.
The reaction mixture was warmed slowly to room temperature and
was stirred for 4 h. The solution was then chilled at -30 °C, and
the chilled solution was added into a Et2O solution containing
Cp*TiCl3 (435 mg, 1.5 mmol) at -30 °C. The reaction mixture
was then warmed slowly to room temperature and was stirred for
an additional 14 h. The mixture was then filtered through a Celite
pad, and the filter cake was washed with Et2O (15 mL × 2). The
combined filtrate and wash were taken to dryness under reduced
pressure to give a red-orange solid. The solid was then dissolved
in a minimum amount of CH2Cl2 layered by a small amount of
hexane. The chilled solution gave red prism shaped microcrystals.
Yield: 486 mg (59.1%). 1H NMR (CDCl3): δ 8.54 (s, 1H, -CHd
N-), 7.04-7.21 (m, 6H, Ar-H), 3.05 (m, 2H, (CH3)2CH-), 2.22
(s, 3H, CH3C6H3), 2.10 (s, 15H, C5(CH3)5), 1.15 (d, 12H, J ) 6.4
Hz, (CH3)2CH-). 13C NMR (CDCl3): δ 163.9, 156.9, 149.6, 137.1,
133.8, 133.4, 129.9, 126.4, 124.7, 123.8, 123.0, 122.6, 28.0, 23.0,
17.2, 13.1. Anal. Calcd for C30H39Cl2NOTi: C, 65.70; H, 7.17; N,
2.55. Found: C, 65.41; H, 7.01; N, 2.49.
Synthesis of Cp*TiCl2[O-2-tBu-6-{(2,6-iPr2C6H3)NdCH}-
C6H3] (2). Synthesis of 2 was carried out by the same procedure
as that for 1 except that Cp*TiCl3 (500 mg, 1.73 mmol) and 2-t-
Bu-6-(2,6-iPr-C6H3NdCH)C6H3OH (403 mg, 1.73 mmol)
in place of 2-Me-6-(2,6-iPr2C6H3)NdCH-C6H3OH were used.
Yield: 621 mg (60.8%). 1H NMR (CDCl3): δ 8.61 (s, 1H, -CHd
N-), 7.47 (dd, 1H, Ar-H), 7.12-7.05 (m, 2H, Ar-H), 3.00 (m, 2H,
(CH3)3CH-), 2.02 (s, 15H, C5(CH3)5), 1.42 (s, 9H, C(CH3)3), 1.16
(d, J ) 7.0 Hz, 12H, (CH3)2CH). 13C NMR (CDCl3): δ 165.4,
156.9, 149.2, 140.3, 137.2, 134.0, 130.1, 128.4, 125.7, 123.9, 122.9,
122.5, 35.3, 30.6, 28.0, 22.7, 13.2. Anal. Calcd for C33H45Cl2-
NOTi: C, 67.12; H, 7.68; N, 2.37. Found: C, 67.01; H, 7.63; N,
2.28.
Experimental Section
General Procedures. All experiments were carried out under a
nitrogen atmosphere in a Vacuum Atmospheres drybox unless
otherwise specified. Anhydrous grade tetrahydrofuran, diethyl ether,
hexane, dichloromethane, and toluene (Kanto Kagaku Co. Ltd) were
transferred into a bottle containing molecular sieves (mixture of 3
Å and 4 Å 1/16, and 13X) under a nitrogen stream in the drybox
and were used without further purification. CpTiCl3 and Cp*TiCl3
were purchased from Strem Chemical Co., Ltd. Styrene of reagent
grade (Kanto Kagaku Co. Ltd.) was stored in a freezer after passing
through an alumina short column under nitrogen flow in the drybox.
Ethylene for polymerization was of polymerization grade (purity
>99.9%, Sumitomo Seika Co., Ltd.) and was used as received.
Reagent grade [PhN(H)Me2][B(C6F5)4] (Asahi Glass Co. Ltd.), and
AliBu3 (Kanto Kagaku Co. Ltd.) were stored in the drybox and
were used as received. Elemental analyses were performed by using
a PE2400II Series (Perkin-Elmer Co.). Some analysis runs were
employed twice to confirm the reproducibility in independent
analysis/synthesis runs.
Synthesis of Cp*TiCl2[O-2-Me-6-(tBuNdCH)C6H3] (3). Syn-
thesis of 3 was carried out by the same procedure as that for 1
except that Cp*TiCl3(579 mg, 2.0 mmol) and 2-Me-6-(tBuNdCH)-
C6H3OH(383mg,2.0mmol)inplaceof2-Me-6-(2,6-iPr2C6H3)NdCH-
1
All H and 13C NMR spectra were recorded on a JEOL JNM-
1
C6H3OH were used. Yield: 476 mg (53.6%). H NMR (CDCl3):
LA400 spectrometer (399.65 MHz, 1H). All deuterated NMR
solvents were stored over molecular sieves under a nitrogen
atmosphere, and all chemical shifts are given in ppm and are
referenced to Me4Si. 13C NMR spectra for polyethylene and
polystyrene were recorded on a JEOL JNM-LA400 spectrometer
(100.40 MHz, 13C) with proton decoupling. The pulse interval was
5.2 s, the acquisition time was 0.8 s, the pulse angle was 90°, and
the number of transients accumulated was ca. 6000. The analysis
samples of copolymers were prepared by dissolving polymers in a
mixed solution of 1,2,4-trichlorobenzene/benzene-d6 (90/10 wt), and
the spectra were measured at 110 °C. The NBE contents in the
δ 8.67 (s, 1H, -CHdN-), 7.79 (dd, 1H, Ar-H), 7.14 (m, 1H, Ar-
H), 6.94 (t, 1H, J ) 7.7 Hz, Ar-H), 2.26 (s, 3H, CH3C6H3), 2.17
(s,15H, C5(CH3)5), 1.27 (s, 9H, C(CH3)3). 13C NMR (CDCl3): δ
162.8, 151.2, 132.8, 132.2, 128.7, 127.6, 124.7, 122.9, 57.6, 29.6,
16.7, 12.8. Anal. Calcd for C22H31Cl2NOTi: C, 59.48; H, 7.03; N,
3.15. Found: C, 59.40; H, 7.00; N, 3.10.
Synthesis of Cp*TiCl2[O-2-tBu-6-(tBuNdCH)C6H3] (4). Syn-
thesis of 4 was carried out by the same procedure as that for 1
except that Cp*TiCl3(500 mg, 1.73 mmol) and 2-tBu-6-(tBuNd
CH)-C6H3OH (403 mg, 1.73 mmol) in place of 2-Me-6-(2,6-i-
Pr2C6H3)NdCH-C6H3OH were used. Yield: 438 mg (50.6%). 1H
NMR (CDCl3): δ 8.70 (s, 1H, -CHdN-), 7.94 (d, 1H, J ) 7.7
Hz, Ar-H), 7.33 (d, 1H, J ) 7.7 Hz, Ar-H), 6.99 (t, 1H, J ) 7.7
Hz, Ar-H), 2.12 (s, 15H, C5(CH3)5), 1.37 (s, 9H, C(CH3)3), 1.28
(s, 9H, C(CH3)3). 13C NMR (CDCl3): δ 164.5, 151.7, 138.9, 133.4,
129.4, 128.3, 125.9, 122.8, 57.9, 35.1, 30.4, 29.5, 13.03. Anal. Calcd
for C20H27Cl2NOTi: C, 57.71; H, 6.54; N, 3.37. Found: C, 57.62;
H, 6.52; N, 3.35.
resultant poly(ethylene-co-norbornene)s were estimated by the 13
C
NMR spectra of copolymer according to the previous reports,22,43
and the 1-hexene contents in poly(ethylene-co-1-hexene)s were also
estimated according to the previous reports.20,44
Molecular weights and molecular weight distributions for the
poly(ethylene-co-styrene)s were measured by gel permeation chro-
matography (Tosoh HLC-8121GPC/HT) with a polystyrene gel
column (TSK gel GMHHR-H HT × 2, 30 cm × 7.8 mm i.d.),
Synthesis of (1,2,4-Me3C5H2)TiCl2[O-2-Me-6-{(2,6-iPr2C6H3)-
NdCH}C6H3] (5). Synthesis of 5 was carried out by the same
procedure as that for 1 except that (1,2,4-Me3)CpTiCl3 (392 mg,
1.50 mmol) was used. Yield: 443 mg (56.7%). 1H NMR (CDCl3):
(44) Assignments of resonances in the 13C NMR spectra and estimation
of 1-hexene content in poly(ethylene-co-1-hexene)s: Randall, J. C. JMS
ReV. Macromol. Chem. Phys. 1989, C29 (2&3), 201.

5976 Organometallics, Vol. 26, No. 24, 2007
Table 8. Crystal Data and Structure Refinement Parameters for Complexes 1, 2, 3, and 5
Zhang et al.
1
2
3
5
empirical formula
fw
C30H39Cl2NOTi
548.45
C33H45Cl2NOTi
590.53
C22H31Cl2NOTi
444.3
C28H35Cl2NOTi
520.4
cryst color, habit
cryst size (mm)
cryst syst
space group
a (Å)
red, prism
red, prism
red, platelet
0.80 × 0.80 × 0.25
triclinic
red, platelet
0.80 × 0.42 × 0.30
monoclinic
P21/c (#14)
14.914(5)
0.80 × 0.80 × 0.36
monoclinic
Cc (#9)
23.967(10)
8.126(4)
0.80 × 0.80 × 0.60
orthorhombic
Pbca (#61)
18.083(3)
15.268(3)
23.643(5)
P1h (#2)
7.405(3)
9.169(5)
17.929(10)
80.16
b (Å)
c (Å)
15.886(5)
24.206(10)
15.972(6)
R (deg)
â (deg)
107.487(18)
82.88(2)
72.895(19)
1142.8(9)
2
104.932(12)
γ (deg)
volume (Å3)
Z
2966.9(20)
4
1.228
6527.4(22)
8
1.202
5541.3(34)
8
1.247
D
calc (g/cm3)
1.291
F(000)
1160.00
14 169
5737
355
1.024
2512.00
57 211
5108
388
1.007
468.00
11 291
4093
275
1.003
0.0541; 0.1142
2192.00
47 817
7236
665
1.001
no. of reflns measd
no. of observns
no. of variables
goodness-of-fit
residuals: R1; wR2
0.0335; 0.0873
0.0370; 0.0976
0.0669; 0.1310
δ 8.58 (s, 1H, -CHdN-), 7.13-7.07 (m, 6H, Ar-H), 6.17 (s, 2H,
C5H2), 2.96 (m, 2H, 2(CH3)3CH-), 2.34 (s, 3H, CH3C6H3), 2.16
(s, 6H, C5(CH3)2), 2.08 (s, 3H, C5(CH3)), 1.16 (d, J ) 6.9 Hz, 12H,
2(CH3)2CH). 13C NMR (CDCl3): δ 165.8, 157.1, 149.4, 137.3,
135.7, 135.3, 133.9, 129.4, 126.2, 125.0, 124.0, 123.6, 122.9, 121.9,
27.9, 23.3, 17.2, 16.1, 14.6. Anal. Calcd for C28H35Cl2NOTi: C,
64.63; H, 6.78; N, 2.69. Found: C, 64.63; H, 6.90; N, 2.64.
Synthesis of CpTiCl2[O-2-Me-6-{(2,6-iPr2C6H3)NdCH}C6H3]
(6). Synthesis of 6 was carried out by the same procedure as that
for 1 except that CpTiCl3 (262 mg, 1.2 mmol) and 2-Me-6-(2,6-i-
Pr2C6H3)NdCH-C6H3OH (354 mg, 1.20 mmol) were used.
Yield: 407 mg (70.9%). 1H NMR (CDCl3): δ 8.54 (s, 1H, -CHd
N-), 8.01 (d, 1H, J ) 6.2 Hz Ar-H), 7.35-7.09 (m, 5H, Ar-H),
6.66 (s, 5H, C5H5), 2.97 (m, 2H, 2(CH3)2CH-), 2.35 (s, 3H,
CH3C6H3), 1.17 (d, J ) 7.0 Hz, 12H, 2(CH3)2CH-). 13C NMR
(CDCl3) δ: 167.1, 157.7, 149.3, 137.1, 133.9, 128.1, 125.4, 124.7,
123.9, 122.7, 121.0, 27.8, 23.2, 16.8. Anal. Calcd for C25H29Cl2-
NOTi: C, 62.78; H, 6.11; N, 2.93. Found (1): C, 62.70; H, 6.01;
N, 2.90. Found (2): C, 62.68; H, 5.99; N, 2.87.
12.4. Anal. Calcd for C32H45NOTi: C, 75.72; H, 8.94; N, 2.76.
Found: C, 75.86; H, 9.06; N, 2.75.
Reaction of Cp*TiMe2[O-2-Me-6-{(2,6-iPr-C6H3)NdCH}-
C6H3] (8) with [PhN(H)Me2][B(C6F5)4]. A solution of 8 (31 mg,
0.061mmol) in bromobenzene-d5 was added dropwise to a
solution of [PhN(H)Me2][B(C6F5)4] (56 mg, 0.061mmol) in bro-
mobenzene-d5 at -30 °C. The resulting mixture was shaken and
was then transferred into a Young’s Teflon NMR tube to measure
the NMR spectroscopic data at room temperature (25 °C). 1H NMR
(C6D5Br): δ 8.64 (s, 1H, -CHdN-), 7.36-6.57 (m, 11H, Ar-H),
2.84 (s, 2H, (CH3)3CH-), 2.62 (s, 6H, NMe2), 2.01 (s, 3H,
CH3C6H3), 1.43 (s, 15H, C5(CH3)5), 1.28 (d, 3H, J ) 6.6 Hz, (CH3)2-
CH-), 1.12 (d, 3H, J ) 6.6 Hz, (CH3)2CH-), 0.93 (s, 3H, Ti-
Me), 0.12 (s, 3H, CH4). 19F NMR (C6D5Br): δ -133.37, -163.85,
-167.66.
Crystallographic Analysis. All measurements were made on a
Rigaku RAXIS-RAPID imaging plate diffractometer with graphite-
monochromated Mo KR radiation. All structures were solved by
direct methods and expanded using Fourier techniques,45 and the
non-hydrogen atoms were refined anisotropically. Hydrogen
atoms were included but not refined. All calculations were
performed using the Crystal Structure46,47 crystallographic software
package. Selected crystal collection parameters are summarized in
Tables 8 and 9.
Synthesis of CpTiCl2[O-2-Me-6-(tBuNdCH)C6H3] (7). Syn-
thesis of 7 was carried out by the same procedure as that for 1
except that CpTiCl3(327 mg, 1.50 mmol) and 2-Me-6-(tBuNCH)-
C6H3OH(287mg,1.5mmol)inplaceof2-Me-6-(2,6-iPr2C6H3)NdCH-
1
C6H3OH were used. Yield: 407 mg (72.5%). H NMR (CDCl3):
Polymerization of Ethylene. Ethylene polymerizations were
conducted in toluene by using a 100 mL scale autoclave. Solvent
(29.0 mL) and MAO as a white solid (174 mg, 3.0 mmol), prepared
by removing toluene and AlMe3 from commercially available MAO
(PMAO-S, Tosoh Finechem Co.), were charged into the autoclave
in the drybox, and the apparatus was placed under ethylene
atmosphere (1 atm). After the addition of a toluene solution (1.0
mL) containing a prescribed amount of 1 via a syringe, the reaction
apparatus was pressurized to 3 atm (total 4 atm), and the mixture
was stirred magnetically for 10 min. After the above procedure,
ethylene was purged, and the mixture was then poured into EtOH
(150 mL) containing HCl (10 mL). The resultant polymer was
collected on a filter paper by filtration and was adequately washed
δ 8.66 (s, 1H, -CHdN-), 7.75 (d, 1H, J ) 7.7 Hz, Ar-H), 7.19
(d, 1H, J ) 7.3 Hz, Ar-H), 7.01 (t, 1H, J ) 7.5 Hz, Ar-H), 6.66 (s,
5H, C5H5), 2.27 (s, 3H, CH3C6H3), 1.31 (s, 9H, C(CH3)3). 13C NMR
(CDCl3): δ 167.1, 151.5, 132.3, 127.3, 126.5, 124.6, 124.2, 121.0,
57.7, 29.6, 16.7. Anal. Calcd for C17H21Cl2NOTi: C, 54.58; H,
5.66; N, 3.74. Found: C, 54.15; H, 5.62; N, 3.50.
Synthesis of Cp*TiMe2[O-2-Me-6-{(2,6-iPr-C6H3)NdCH}-
C6H3] (8). Into a stirred solution of Cp*TiMe3 (114 mg, 0.5 mmol)
in dry n-hexane (20 mL) 2-Me-6-{(2,6-iPr-C6H3)NdCH}C6H3-
OH (148 mg, 0.5 mmol) was added dropowise at -30 °C. The
reaction mixture was warmed slowly to room temperature and was
stirred for 4 h. The mixture was then filtered through a Celite pad,
and the filter cake was washed with hexane (10 mL × 2). The
combined filtrate and wash were taken to dryness under reduced
(45) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.; de
Delder, R.; Israel, R.; Smits, J. M. M. DIRDIF94; The DIRDIF94 program
system, Technical report of the crystallography laboratory; University of
Nijmegen: The Netherlands, 1994.
(46) CrystalStructure 3.6.0, Crystal Structure Analysis Package; Rigaku
and Rigaku/MSC: The Woodlands, TX, 2000-2004.
(47) Watkin, D. J., Prout, C. K. Carruthers, J. R.; Betteridge, P. W.
CRYSTALS Issue 10; Chemical Crystallography Laboratory: Oxford, UK,
1996.
1
pressure to give a yellow solid. Yield: 234 mg (92%). H NMR
(C6D6): δ 8.78 (s, 1H, -CHdN-), 8.62 (d, 1H, J ) 7.7 Hz, Ar-
H), 7.21-6.97 (m, 5H, Ar-H), 3.34 (t, H, J ) 6.8 Hz, (CH3)3CH-
), 2.21 (s, 3H, CH3C6H3), 1.67 (s, 15H, C5(CH3)5), 1.32 (d, 12H, J
) 7.0 Hz, (CH3)2CH-), 0.73 (s, 6H, Ti-CH3). 13C NMR (C6D6):
δ 168.4, 165.2, 161.8, 159.5, 152.6, 140.7, 135.0, 130.5, 127.1,
126.2, 125.4, 124.5, 124.0, 123.9, 122.4, 57.4, 28.3, 24.1, 18.3,

Half-Titanocenes Containing Phenoxy-imine Ligands
Organometallics, Vol. 26, No. 24, 2007 5977
Table 9. Crystal Data and Structure Refinement Parameters for Complexes 6, 7, and 8
6
7
8
empirical formula
fw
C25H29Cl2NOTi
478.32
C17H21Cl2NOTi
374.16
C32H45NOTi
507.61
cryst color, habit
cryst syst
space group
a (Å)
b (Å)
c (Å)
red, prism
orthorhombic
Pbca (#61)
13.129(4)
14.930(3)
24.791(6)
orange, prism
monoclinic
P21/a (#14)
13.556(6)
7.224(3)
18.814(7)
102.982(18)o
1795.2(12)
4
yellow, block
monoclinic
Cc (#9)
24.043(3)
8.1281(8)
16.5418(17)
108.631(3)o
3063.2(6)
4
â (deg)
volume (Å3)
Z
4859.3(20)
8
1.308
D
calc (g/cm3)
1.384
1.101
F(000)
2000.00
0.80 × 0.60 × 0.60
43 760
5515
300
776.00
1096.00
cryst size (mm)
no. of reflns measd
no. of observns
no. of variables
goodness-of-fit on F2
residuals: R1; wR2
0.80 × 0.70 × 0.50
0.80 × 0.80 × 0.60
16 760
11 753
3493
220
0.999
0.0259; 0.0798
3483
361
0.999
0.0364; 0.0828
1.013
0.0443; 0.0973
with EtOH and then dried in Vacuo. Polymerization results in Table
4 are data at the optimized Al/Ti molar ratios.
of 1-hexene was charged and the total volume of toluene and
1-hexene was set to 40 or 50 mL.
Syndiospecific Polymerization of Styrene. Toluene (19 mL),
styrene (10 mL), and the MAO solid (174 mg, 3.0 mmol) were
added into the autoclave (100 mL scale stainless steel) in the drybox,
and the reaction apparatus was then replaced and filled with nitrogen
at room temperature (25 °C). A toluene solution (1.0 mL) containing
a prescribed amount of 1 was then added into the autoclave. The
mixture was magnetically stirred for 10 min, and the mixture was
then poured into EtOH (50 mL) containing HCl (5 mL). The
resultant polymer was collected on a filter paper by filtration and
was adequately washed with EtOH and then dried in Vacuo.
According to a previous report,21 the resultant polymer mixture was
separated into two fractions, and atactic polystyrene prepared only
by MAO itself was extracted with acetone; syndiotactic polystyrene
prepared by 1-MAO catalyst was isolated as the acetone-insoluble
fraction.
Copolymerization of Ethylene with Norbornene and 1-Hex-
ene. Experimental procedures for the copolymerization of ethylene
with norbornene were the same as those for the ethylene polym-
erization described above except that a prescribed amount of
norbornene was added into the autoclave. Experimental procedures
for the ethylene/1-hexene polymerizations were the same as those
for the ethylene polymerizations except that a prescribed amount
Acknowledgment. K.N. expresses his heartfelt thanks to
Tosoh Finechem Co. for donating MAO (PMAO-S), and to Prof.
Michiya Fujiki (NAIST) for helpful comments. The present
research is partly supported by a Grant-in-Aid for Scientific
Research (B) from the Japan Society for the Promotion of
Science (JSPS, No. 18350055). Z.H. expresses his thanks to
JSPS for a postdoctoral fellowship (P04129).
Supporting Information Available: CIF files for complexes
Cp*TiCl2[O-2-R1-6-(R2NdCH)C6H3] [R1, R2 ) Me, 2,6-iPr2C6H3
t
t
(1), Bu, 2,6-iPrC6H3 (2), Me, Bu (3)], (1,2,4-Me3C5H2)TiCl2[O-
2-Me-6-{(2,6-iPrC6H3)NdCH}C6H3] (5), CpTiCl2[O-2-R1-6-(R2Nd
CH)C6H3] [R1, R2 ) Me, 2,6-iPr2C6H3 (6), Cp, Me, Bu (7)], and
t
Cp*TiMe2[O-2-Me-6-{(2,6-iPr2C6H3)NdCH}C6H3] (8). 1H and 19
F
NMR spectrum for reaction of 8 with 1.0 equiv of [PhN(H)Me2]-
[B(C6F5)4], 13C NMR spectra for poly(ethylene-co-NBE)s and poly-
(ethylene-co-1-hexene)s, and the structure reports for 1-3 and 5-8.
These materials are available free of charge via the Internet at
http://pubs.acs.org.
OM700660B