Synthesis and characterization of titanium complexes bearing two β-enaminoketonato ligands with electron-withdrawing groups and their behavior in ethylene polymerization

Article abstract of DOI:10.1021/om700803u

A series of new titanium complexes with two asymmetric bidentate β-enaminoketonato (N,O) ligands (4b-t), [RN=C(CF₃)CHC(t-Bu)O] ₂TiCl₂ (4b, R = -C₆H₄F(o); 4c, R = -C₆H₄F(m);4d, R = -C₆H₄F(p); 4e, R = -C₆H₃F₂(2,3); 4f, R = -C₆H ₃F₂(2,4); 4g, R = -C₆H₃F ₂(3,5); 4h, R = -C₆H₃F₂(2,6); 4i, R = -C₆H₃F₂(3,4); 4j, R = -C₆H ₃F₂(3,5); 4k, R = -C₆H₂F ₃(2,3,4); 4l, R = -C₆H₂F₃(3,4,5); 4m, R = -C₆H₄CF₃(o); 4n, R = -C ₆H₄CF₃(m); 4o, R = -C₆H ₄CF₃(p); 4p, R = -C₆H₄Cl(p); 4q, R = -C₆H₄I(p); 4r, R = -C₆H₄NO ₂(p); 4s, R = -CH₂C₆H₃; 4t, R = -C₆H₁₁), have been synthesized and characterized. X-ray crystal structures suggest that complexes 4a-d, 4j, and 4m all adopt a distorted octahedral geometry around the titanium centers. Two chlorine atoms in complexes 4a-d and 4j are in cw-configuration, while those of complex 4m are trans. NMR spectra and X-ray structure analyses reveal that the conformational isomers of some complexes, such as 4b, in which the two β-enaminoketonato ligands bear asymmetrical N-phenyl rings, exist both in solution and in solid state. With modified methylaluminoxane (MMAO) as a cocatalyst, complexes 4b-1 and 4n-q are highly active toward ethylene polymerization and produce high molecular weight polyethylenes. The catalytic activities are significantly enhanced by introducing electron-withdrawing groups (EWG), such as fluorine and chlorine atom(s) or the trifluoromethyl group, into suitable positions on the N-aryl rings. The titanium complex 4m is inactive toward ethylene polymerization due to the trans-configuration of the two chlorine atoms. In addition, the titanium complexes display low catalytic activity for ethylene polymerization only if the N-substituents are not aromatic.

Full text of DOI:10.1021/om700803u

3642
Organometallics 2008, 27, 3642–3653
Articles
Synthesis and Characterization of Titanium Complexes Bearing Two
ꢀ-Enaminoketonato Ligands with Electron-Withdrawing Groups
and Their Behavior in Ethylene Polymerization
Wei-Ping Ye,†,‡ Jie Zhan,†,‡ Li Pan,† Ning-Hai Hu, and Yue-Sheng Li*,†
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry,
Chinese Academy of Sciences, Changchun 130022, People’s Republic of China, and Graduate School of
the Chinese Academy of Sciences, Changchun Branch, People’s Republic of China
ReceiVed August 6, 2007
A series of new titanium complexes with two asymmetric bidentate ꢀ-enaminoketonato (N,O) ligands
(4b-t), [RNdC(CF3)CHC(t-Bu)O]2TiCl2 (4b, R ) -C6H4F(o); 4c, R ) -C6H4F(m);4d, R ) -C6H4F(p);
4e, R ) -C6H3F2(2,3); 4f, R ) -C6H3F2(2,4); 4g, R ) -C6H3F2(2,5); 4h, R ) -C6H3F2(2,6); 4i, R )
-C6H3F2(3,4); 4j, R ) -C6H3F2(3,5); 4k, R ) -C6H2F3(2,3,4); 4l, R ) -C6H2F3(3,4,5); 4m, R )
-C6H4CF3(o); 4n, R ) -C6H4CF3(m); 4o, R ) -C6H4CF3(p); 4p, R ) -C6H4Cl(p); 4q, R ) -C6H4I(p);
4r, R ) -C6H4NO2(p); 4s, R ) -CH2C6H5; 4t, R ) -C6H11), have been synthesized and characterized.
X-ray crystal structures suggest that complexes 4a-d, 4j, and 4m all adopt a distorted octahedral geometry
around the titanium centers. Two chlorine atoms in complexes 4a-d and 4j are in cis-configuration,
while those of complex 4m are trans. NMR spectra and X-ray structure analyses reveal that the
conformational isomers of some complexes, such as 4b, in which the two ꢀ-enaminoketonato ligands
bear asymmetrical N-phenyl rings, exist both in solution and in solid state. With modified methylalu-
minoxane (MMAO) as a cocatalyst, complexes 4b-l and 4n-q are highly active toward ethylene
polymerization and produce high molecular weight polyethylenes. The catalytic activities are significantly
enhanced by introducing electron-withdrawing groups (EWG), such as fluorine and chlorine atom(s) or
the trifluoromethyl group, into suitable positions on the N-aryl rings. The titanium complex 4m is inactive
toward ethylene polymerization due to the trans-configuration of the two chlorine atoms. In addition, the
titanium complexes display low catalytic activity for ethylene polymerization only if the N-substituents
are not aromatic.
workers developed nickel and palladium catalysts based on
chelating diimine ligands,10 Grubbs and his colleagues reported
neutral nickel catalysts based on chelating phenoxyimine
ligands,11 Brookhart and Gibson reported independently iron
and cobalt catalysts based on chelating diimine-pyridine
ligands,12,13 and Fujita and Coates discovered titanium and
zirconium catalysts based on chelating phenoxyimine ligands.14,15
This research promoted the development of a non-metallocene
catalyst for olefin polymerization. Subsequent research dem-
onstrated that subtle variation of the ligands, including steric
Introduction
In recent years, significant attention has focused on the design
and synthesis of highly active, well-defined or single-site
transition metal catalysts for olefin polymerization.1 After the
extensive investigation of the transition metal complexes with
cyclopentadienyl (Cp) or derivate ligands, the new non-Cp
ligand environment has currently attracted more and more
interest,2–9 which brought about the discovery of a variety of
non-metallocene catalysts. For example, Brookhart and co-
* To whom correspondence should be addressed. Fax: +86-431-5262124.
E-mail: ysli@ciac.jl.cn.
(7) Xu, T.; Mu, Y.; Gao, W.; Ni, J.; Ye, L.; Tao, Y. J. Am. Chem. Soc.
2007, 129, 2236.
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† State Key Laboratory of Polymer Physics and Chemistry.
‡ Graduate School of the Chinese Academy of Sciences.
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Shi, L. P. Organometallics 2006, 25, 3259. (b) Li, W.; Sun, H.; Chen, M.;
Wang, Z.; Hu, D.; Shen, Q.; Zhang, Y. Organometallics 2005, 24, 5925.
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Shi, L. P.; Tang, Y. Macromol. Rapid Commun. 2005, 26, 1609.
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R. H.; Bansleben, A.; Day, M. W. Organometallics 1998, 17, 3149. (b)
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10.1021/om700803u CCC: $40.75
2008 American Chemical Society
Publication on Web 07/12/2008

Titanium Complexes Bearing Two ꢀ-Enaminoketonato
Organometallics, Vol. 27, No. 15, 2008 3643
Scheme 1. General Synthetic Route of the Titanium Comp-
lexes Used in This Study
and electronic effects, can greatly influence the performance of
catalysts in olefin polymerization. For example, Mazzeo and
co-workers found that the isotacticities of the polypropenes
obtained by a series of titanium catalysts bearing phenoxyimine
ligands were considerably influenced by the o-phenoxy halide
substituents.16 Tang and his colleagues reported a series of
titanium complexes bearing monoanionic tridentate ligands and
found their polymerization behavior for olefins was also greatly
influenced by the ligand structure.6a Especially, Fujita and
Coates found that the polymerization behavior of the titanium
catalysts bearing phenoxyimine ligands were obviously influ-
enced by introducing fluorine atom(s) to the ligands: catalytic
activity increased with increasing number of fluorine atoms, and
only the titanium complexes with fluorine atom(s) adjacent to
the imine nitrogen promoted living ethylene polymerization
under similar conditions.14c,15c
Recently we reported a type of titanium catalyst with
chelating asymmetrical bidentate ꢀ-enaminoketonato ligands,
[PhNC(R2)C(H)C(R1)O]2TiCl2, for olefin polymerization.17
As the ꢀ-enaminoketonato ligand has multiple sites for
introducing or changing the substituents, the steric and
electronic requirements of the metal center can be modulated
easily by varying the ligand structure. By variation of the
substituents (R1 and R2), we obtained a series of highly
efficient catalysts toward ethylene polymerization and eth-
ylene/R-olefin or cycloolefin copolymerizations.18 Among all
the catalysts studied, catalyst 4a (R1 ) t-Bu, R2 ) CF3)
showed the highest activity under the same conditions. The
fact that the variation of the ligand structure may lead to
profound changes in the performance of the catalyst and the
properties of the polymers prompts us to synthesize new
titanium complexes [(EWG)ArNdC(CF3)CHC(t-Bu)O]2TiCl2
by introducing the fluorine atoms or other EWG to the
ꢀ-enaminoketonato ligands and investigate the effect of these
EWGs on the polymerization behavior of olefins. Herein, we
describe the synthesis, characterization, and ethylene polym-
erization behavior of these titanium complexes bearing
aromatic-substituted ꢀ-enaminoketonato ligands.
Results and Discussion
Synthesis and Characterization of New Titanium
Complexes. New titanium complexes 4b-q used here were
synthesized according to the modified procedures reported
previously as shown in Scheme 1.17 ꢀ-Enaminoketonates 2b-s
were obtained in moderate to high yields (2b, 58%; 2c, 69%;
2d, 75%; 2e, 71%; 2f, 61%; 2g, 74%; 2h, 64%; 2i, 72%; 2j,
80%; 2k, 78%; 2l, 62%; 2m, 67%; 2n, 79%; 2o, 82%; 2p, 86%;
2q, 59%; 2r, 57%; 2s, 46%) by the condensation of 1,1,1-
trifluoro-5,5-dimethyl-2,4-hexanedione with the corresponding
aniline derivatives in toluene containing a little p-toluenesulfonic
acid as a catalyst. ꢀ-Enaminoketonate 2t was not obtained via
the same method probably due to the strong basicity of
cyclohexylamine and the strong acidity of the ꢀ-diketonate. This
compound was prepared in poor yield (35%) by the reaction of
the ꢀ-diketonate with cyclohexylamine in toluene using TiCl4
as a catalyst. The titanium complexes 4b-t were prepared under
moderate conditions in good yields (4b, 67%; 4c, 78%; 4d, 76%;
4e, 73%; 4f, 84%; 4g, 65%, 4h, 80%, 4i, 67%; 4j, 65%; 4k,
67%; 4l, 70%; 4m, 76%; 4n, 82%; 4o, 86%; 4p, 71%; 4q, 76%;
4r, 66%; 4s, 73%; 4t, 61%) by the reaction of TiCl4 with 2
equiv of the lithium salts of ꢀ-enaminoketonato 3b-t in dry
diethyl ether. The resulting complexes were obtained as dark
red crystalline solids.
The chelate complexes [O,N]2TiCl2 probably exist as five
configurational isomers, as shown in Scheme 2. The relative
formation energies (RFE) of these isomers were calculated using
density functional theory (DFT) for the representative com-
plexes, 4a-d, 4m, and 4n, and are summarized in Table 1. The
data listed in Table 1 indicate that the isomer cis-I, of all the
complexes except for 4m, in which two oxygen atoms are trans,
and the two nitrogen atoms and two chlorine atoms are in cis
positions, displays the lowest RFE and is the most stable.
However, for complex 4m, isomer trans-II, in which two
oxygen atoms, two nitrogen atoms, and two chlorine atoms are
all in trans configuration, displays the lowest RFE and is the
most stable. This result could be caused by the large volume of
the ortho-trifluoromethyl groups on the N-aryl moieties. These
calculated results are further confirmed by crystallographic
analyses.
(13) (a) Britovsek, G. P. J.; Gibson, V. C.; Kimberley, B. S.; Maddox,
P. J.; McTavish, S. J.; Solan, G. A.; White, A. J. P.; Williams, D. J. Chem.
Commun. 1998, 849. (b) Britovsek, G. J. P.; Bruce, M.; Gibson, V. C.;
Kimberley, B. S.; Maddox, P. J.; Mastroianni, S. S.; McTavish, J.; Redshaw,
C.; Solan, G. A.; Stro¨mberg, S.; White, A. J. P.; Williams, D. J. J. Am.
Chem. Soc. 1999, 121, 8728.
(14) (a) Saito, J.; Mitani, M.; Mohri, J.; Yoshida, Y.; Mastui, S.; Ishii,
S.; Kojoh, S.; Kashiwa, N.; Fujita, T. Angew. Chem., Int. Ed. 2001, 40,
2918. (b) 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. (c) Mitani, M.; Mohri,
J.; Yoshida, Y.; Saito, J.; Ishii, S.; Tsuru, K.; Matsui, S.; Furuyama, R.;
Nakano, T.; Tanaka, H.; Kojoh, S.-I.; Matsugi, T.; Kashiwa, N.; Fujita, T.
J. Am. Chem. Soc. 2002, 124, 3327. (d) Mitani, M.; Furuyama, R.; Mohri,
J.; Saito, J.; Ishii, S.; Terao, H.; Kashiwa, N.; Fujita, T. J. Am. Chem. Soc.
2002, 124, 7888. (e) Mitani, M.; Furuyama, R.; Mohri, J.; Saito, J.; Ishii,
S.; Terao, H.; Nakano, T.; Tanaka, H.; Fujita, T. J. Am. Chem. Soc. 2003,
125, 4293.
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123, 5134. (b) Hustad, P. D.; Coates, G. W. J. Am. Chem. Soc. 2002, 124,
11578. (c) Mason, A. F.; Tian, J.; Hustad, P. D.; Lobkovsky, E. B.; Coates,
G. W.; Israel, J. Chem. 2002, 42, 301. (d) Reinartz, S.; Mason, A. F.;
Lobkovsky, E. B.; Coates, G. W. Organometallics 2003, 22, 2542. (e)
Mason, A. F.; Coates, G. W. J. Am. Chem. Soc. 2004, 126, 10798. (f) Mason,
A. F.; Coates, G. W. J. Am. Chem. Soc. 2004, 126, 16326.
(16) Mazzeo, M.; Strianese, M.; Lamberti, M.; Santoriello, I.; Pellecchia,
C. Macromolecules 2006, 39, 7812–7820.
(17) (a) Li, X. F.; Dai, K.; Ye, W. P.; Pan, L.; Li, Y. S. Organometallics
2004, 23, 1223. (b) Tang, L. M.; Hu, T.; Bo, Y. J.; Li, Y. S; Hu, N. H. J.
Organomet. Chem. 2005, 690, 3135.
The molecular structures of complexes 4a-d, 4j, and 4m
were confirmed by single-crystal X-ray structure analyses.

3644 Organometallics, Vol. 27, No. 15, 2008
Ye et al.
the 19F NMR spectra of 4b, there are also four resonances
(-115.5, -117.9, -118.4, -121.1 ppm) in the ratio 14:6:
15:2 for the two fluorine atoms on N-aryl moieties of the
ligands. The number of signals, which is more than the
previous results, revealed that there are not less than two
isomers in the solution, because one isomer shows not more
Scheme 2. Structures of Five Configurational Isomers of the
Titanium Complex
1
than two signals in the H NMR for two methine protons
and in the 19F NMR for two fluorine atoms on the imine
1
phenyl ring. A variable-temperature H NMR experiment in
the range 20-150 °C revealed a trend of gradual coalescence
of the signals of the isomers with an increase in temperature
(Figure 4). These data were consistent with a rotational barrier
to interconversion of the isomers of 4b. Due to the rotation
of the N1-C15 and N2-C1 bonds, complex 4b possibly
exists as three relatively stable conformational isomers
(Scheme 3), with RFE values of 4.915 kJ/mol (I), 0 kJ/mol
(II), and 3.341 kJ/mol (III), respectively, according to DFT
calculation. On the basis of the RFE values, the ratio of the
three conformational isomers was calculated to be 0.26:1.0:
0.14 by the Boltzman distribution.19 The most abundant
isomer is thought to be the lowest energy conformational
isomer (II), in which one fluorine atom of the N-aryl is
oriented to the chlorine atom and the other fluorine atom of
the N-aryl is away from the chlorine atom. This supposition
Crystals suitable for X-ray diffraction were grown from hexane
solutions at -20 °C. The crystallographic data together with
the collection and refinement parameters are summarized in
Table 2. The molecular structures of 4a, 4b, and 4m are shown
in Figures 1–3; 4c, 4d, and 4j are shown in Figures S1-S3,
respectively. The selected bond lengths and bond angles are
summarized in Table 3. Just like complex 4u reported
previously,17b in the solid state, these complexes all adopt
distorted octahedral geometry around the titanium center. For
complexes 4a-d and 4j, the two oxygen atoms are situated in
trans position, while the two nitrogen atoms are in cis position
to each other, and so are the two chlorine atoms around the
central titanium metal. However, for complex 4m, the two
oxygen atoms, the two nitrogen atoms, and the two chlorine
atoms are all in trans position (Cl-Ti-Cl angle, 180.0°;
N-Ti-N angle, 180.00(10)°; O-Ti-O angle, 180.0°) around
the central titanium metal.
1
can be confirmed by the H NMR spectra: the two methine
protons of asymmetric conformational isomer II show two
different signals, while the two methine protons of symmetric
conformational isomers I and III show only one signal, and
the ratio of the methine protons almost accords with the ratio
of the three conformational isomers calculated.
The RFE values of the three isomers of the other complexes
are also calculated by DFT and summarized in Table 4. The
data indicate that the most stable conformational isomer is
II for the complexes bearing an ortho-fluorine atom on each
N-aryl ring, while for those complexes with a meta-fluorine
atom or trifluoromethyl group but not an ortho-fluorine atom,
the most stable conformational isomer is III. The H-H
COSY spectra (Figure 5) also confirm that complex 4c
displays three conformational isomers. These spectra show
clearly four unrelated resonances (5.8-6.2 ppm) for the
methine protons of the ligands. A similar phenomenon of
two rotational isomers was observed in t-Bu2(2-
C6H4Ph)PNTi(CH2Ph)3 by Stephan and his co-workers20a,b
and in the heteroligated (salicylaldiminato)(ꢀ-enaminoketon-
ato) titanium complexes reported by Lancaster’s group.20c
The Ti-Cl bond distances for complexes 4b (2.2793 Å),
4c (2.2755 Å), and 4d (2.2712 Å) are close to that of complex
4a (2.2787 Å), but obviously longer than that of complex 4j
(2.2623 Å). Complexes 4b (Cl-Ti-Cl, 98.09°), 4c (Cl-Ti-Cl,
99.85°), and 4d (Cl-Ti-Cl, 100.04°) show narrower
Cl-Ti-Cl angles compared with complex 4a (Cl-Ti-Cl,
100.76°), while complex 4j (Cl-Ti-Cl, 100.35°) exhibits
Cl-Ti-Cl angles similar to complex 4a. These differences
in bond length and angles probably originate from the steric
hindrance and electronic effects caused by fluorine atom(s)
introduced.
Interestingly, the X-ray diffraction of a single crystal
displays two different signals (F5 and F5′) in the ratio of
6:4 for complex 4b, which has only one fluorine atom
adjacent to each imine group, suggesting that two or more
isomers of 4b exist in the solid state. In our previous work,17
the 1H NMR spectra of titanium complexes 4a and 4u
displayed a single sharp resonance for the methine proton
(-CHdC-) of the ꢀ-enaminoketonato chelate ligands in
accordance with only one isomer of octahedral coordination
structure. Complexes 4d, 4h, 4j, 4l, and 4o-t are similar to
4a and 4u, with only a single sharp resonance for the methine
proton, respectively. By contrast, for complexes 4b, 4c, 4e-g,
4i, 4k, and 4n, of which the two ꢀ-enaminoketonato ligands
bear asymmetric N-phenyl rings, the 1H NMR and 19F NMR
data in CDCl3 solution at 25 °C suggest that there are not
Ethylene Polymerization. With MMAO as a cocatalyst,
new titanium complexes 4b-r, bearing EWG on their
ligands, have been investigated as effective catalysts for
ethylene polymerization at room temperature under atmo-
spheric pressure. The results are summarized in Table 5. The
data demonstrate that the introduction of EWG onto the N-
aryl moiety significantly affects catalytic activity and the
properties of the resultant polymers. The melting temperatures
of the resultant polyethylene are between 135 and 140 °C,
suggesting the resultant polymers are linear polyethylene.
Furthermore, the linear structure of the polyethylenes was
also proved by 13C NMR analysis.
(18) (a) Tang, L. M.; Duan, Y. Q; Li, Y. S. J. Polym. Sci. Part A: Polym.
Chem. 2005, 43, 1681. (b) Tang, L. M.; Hu., T.; Pan., L.; Li, Y. S. J. Polym.
Sci. Part A: Polym. Chem. 2005, 43, 6323.
1
less than two isomers. For example, the H NMR spectrum
(CDCl3, 300 MHz) of complex 4b shows four resonances
(6.09, 6.02, 5.98, 5.87 ppm) in the ratio 10:4:2:11 for the
two methine protons of the ligands, and in o-C6D4Cl2 there
are even five different resonances for the same protons. In
(19) According to the Boltzman distribution, the ratio of the confor-
mational isomers based on the relative energy of the isomers, NI:NII:NIII
)
-∆EII
e-∆E /RT:e
/RT:e-∆EIII/RT. Atkins, P. W., Ed. Physical Chemistry;
I
Oxford University Press: London, 1978; pp 12, 659 ff.

Titanium Complexes Bearing Two ꢀ-Enaminoketonato
Organometallics, Vol. 27, No. 15, 2008 3645
Table 1. Relative Formation Energies (RFE) of the Five Different Configuration Isomers of Some Representative Titanium Complexes (kJ/mol)
Table 2. Crystal Data and Structure Refinements of Complexes 4a-d, 4j, and 4m
4a
4b
4c
4d
4j
4m
empirical formula
fw
crystal system
space group
a (Å)
C
28H30Cl2F6N2O2Ti
C
28H28Cl2F8N2O2Ti
C
28H28Cl2F8N2O2Ti
C
28H26Cl2F8N2O2Ti
C
28H26Cl2F10N2O2Ti
C
30H28Cl2F12N2O2Ti
659.34
orthorhombic
Pbca
19.2495(11)
16.5177(9)
19.7412(11)
90
6276.9(6)
1.395
695.32.
tetragonal
P42/n
25.7113(7)
25.7113(7)
9.8977(6)
90
6543.1(5), 8
1.408
0.498
695.32
monoclinic
C2/c
12.840(2)
15.936(2)
15.369(2)
94.637(2)
3134.4(8), 4
1.473
695.32
monoclinic
P21/n
8.5961(5)
35.172(2)
10.6131(6)
102.4990(10)
3132.7(3),4
1.474
731.33
monoclinic
P21/n
13.9050(8)
16.9870(10)
15.1935(9)
99.9150(10)
3535.2(4), 4
1.415
795.34
monoclinic
P21/c
9.6966(9)
8.6009(8)
20.8763(19)
102.9830(10)
1696.6(3), 2
1.557
b (Å)
c (Å)
ꢀ (deg)
V (Å3), Z
density (Mg/m3)
absorp coeff (mm-1
F(000)
)
0.506
2704
0.520
1416
0.520
1416
0.474
1530
0.507
804
2816
cryst size (mm)
θ range for data
collection (deg)
0.44 × 0.39 × 0.16 0.48 × 0.28 × 0.10 0.41 × 0.14 × 0.11 0.36 × 0.23 × 0.12 0.43 × 0.13 × 0.07 0.39 × 0.16 × 0.06
1.92 to 26.02
1.58 to 26.04
2.04 to 25.34
2.05 to 26.05
1.83 to 26.04
2.00 to 26.02
no. of reflns collected
no. of indep reflns
absorption correction
33 618
35 598
7986
17 525
20 253
9112
6179 (Rint ) 0.0291) 6445 (Rint ) 0.0327) 2877 (Rint ) 0.0379) 6162 (Rint ) 0.0260) 6954 (Rint ) 0.0366) 3322 (Rint ) 0.0324)
semiempirical from equivalents
max. and min. transmn 0.9239 and 0.8065
0.9510 and 0.7954
6445/6/412
0.9441 and 0.8164
2877/0/ 198
0.9426 and 0.8345
6162/36/ 378
0.9698 and 0.8213
6954/2/440
0.9688 and 0.8252
3322/ 0/226
no. of data/restraints/
6179/2/406
params
goodness-of-fit
on F2
1.021
1.138
1.109
1.011
0.968
1.016
final R indices [I >
2σ(I)]: R1, wR2
largest diff peak
0.0400, 0.1056
0.425 and -0.354
0.0560, 0.1833
1.618 and -0.256
0.0632, 0.1390
0.897 and -0.362
0.0681,0.1965
1.371 and -0.573
0.0507, 0.1622
0.957 and -0.276
0.0448,0.1017
0.486 and -0.234
and hole (e Å-3
)
Introduction of electron-withdrawing fluorine atoms into
a ꢀ-enaminoketonato ligand will decrease the electron density
on “N” coordinated to the metal titanium, which will decrease
the electron density of the center titanium. Accordingly, it
will make ethylene coordinate to the center titanium much
easier and enhance catalytic activity. As a result, fluorinated
complexes 4b-d, with one fluorine atom on the each N-aryl
moiety, all display much higher activities toward ethylene
polymerization (8.40, 9.24, and 9.60 kg PE/mmolTi · h,
respectively) than complex 4a (4.32 kg PE/mmolTi · h).
Although the electronic effect of an ortho-fluorine atom is
similar to that of a para one,22 complex 4b, in which the
N-aryl moiety bears one ortho-fluorine atom, displays lower
activity than that of 4d, with one fluorine atom at the para-
position on its N-aryl moiety. One probable reason is that
the steric effect of ortho-fluorine atoms of an N-aryl moiety
of the ligand hinders ethylene access to the center titanium,
leading to a decreased rate of ethylene polymerization.
The data listed in Table 5 also indicate that the polyeth-
ylenes obtained from complexes 4b-d all display high
molecular weights like that obtained from complex 4a. It is
noteworthy that a relatively narrow molecular weight dis-
tribution (PDI ) 1.5) of the polymer produced by complex
4b was observed (entry 2), although it displays more than
one conformational isomer in solution. This result indicates
that the active centers of complex 4b from different confor-
mational isomers are identical or very similar to each other.
In order to further clarify this point, we studied the active
intermediates in ethylene polymerization of complex 4b by
1H NMR spectroscopy. It is well known that the process of
(20) (a) Ghesner, I.; Fenwick, A.; Stephan, D. W. Organometallics 2006,
25, 4985–4995. (b) Graham, T. W.; Kickham, J.; Courtenay, S.; Wei, P.;
Stephan, D. W. Organometallics 2004, 23, 3309. (c) Pennington, D. A.;
Harrington, R. W.; Clegg, W; Bochmann, M; Lancaster, S. J. J. Organomet.
Chem. 2006, 691, 3183.
(21) Vanka, K.; Xu, Z.; Ziegler, T. Organometallics 2004, 23, 2900–
2910.
(22) Morison, R. T., Boyd R. M., Ed. Organic Chemistry, 4th ed.; Allyn
and Bacon, Inc.: Boston, 1983; pp 614-620.

3646 Organometallics, Vol. 27, No. 15, 2008
Ye et al.
meta-fluorine atoms,22 the titanium center of complex 4j is more
strongly electrophilic than complexes 4e-g and 4i, which will
considerably slow the ethylene migration to the metal carbon
bond and decrease catalytic activity.
It is significant to note that the polyethylenes produced
by complexes 4e-h, similar to complex 4b, with fluorine
atom(s) adjacent to the imine nitrogen also display narrower
molecular weight distributions (entries 5-8, PDI ) 1.5-1.6).
Alternatively, broader molecular weight distributions of the
polyethylenes yielded by other complexes with no fluorine
adjacent to the imine nitrogen are comparable to the values
yielded by complex 4a (entry 1, PDI ) 1.8). These results
clearly indicate that the presence of a fluorine atom adjacent
to the imine nitrogen in the ligand accelerates the chain
propagation and decelerates the chain transfer. Perhaps the
ortho-fluorine atoms provide a compact transition state that
assists chain propagation.24 These results are similar to those
of the phenoxyimine titanium catalysts studied by Fujita and
Coates.14c,24
By introducing an extra fluorine atom to complex 4i, we
obtained complexes 4k and 4l, which show lower activities (4.80
and 2.76 kg PE/mmolTi · h, respectively) than 4i (7.08 kg PE/
mmolTi · h). The low activities of 4k and 4l may be attributed
to their stronger electrophilic titanium centers and the lower
stability of the catalytic species originating from the strong
electron-withdrawing effect. These results indicate that the
catalytic activity decrease with further increase of the fluorine
atoms on N-aryl ring in general.
We also explored the effect of reaction parameters such as
ethylene pressure, catalyst concentration, and reaction time on
the ethylene polymerization behavior of some selected fluori-
nated complexes. The typical polymerization results are sum-
marized in Table 6. Compared with the results obtained at
atmospheric pressure, larger differences at 4 atm ethylene
pressure in catalytic activities were observed while the catalytic
activity decreased in the same order: 4d > 4c > 4b, 4f > 4k,
4j (entries 2, 4, 11-14). The observed catalytic activities
changed only slightly if 4b was used, whereas that of 4k shows
larger changes at various catalyst concentrations (entries 5-10).
Both analogues exhibited rather high catalytic activity for at
least 15 min (entries 15-18). For both 4b and 4k, the effect of
ethlene pressure on catalytic activity was nonlinear (entries
1-4).
With other EWGs introduced to the ꢀ-enaminoketonato
ligands, similar results were observed. For example, aromatic-
chlorine/iodine-substituted complexes 4p and 4q also display
much higher catalytic activities (8.16 and 7.56 kg PE/mmolTi · h,
respectively) than nonsubstituted complex 4a, but lower than
the corresponding aromatic-fluorine-substituted complex 4d.
This order of the catalytic activities indicates that the fluorine
atom can enhance the catalytic activity more effectively than
other halogen substituents. Interestingly, complex 4o, with a
trifluoromethyl group as a nonconjugated electron-withdrawing
group in para-position, also shows much higher activity (7.08
kg PE/mmolTi · h) compared with complex 4a. However,
complex 4m, with an ortho-trifluoromethyl group does not
exhibit any catalytic activity due to the trans-configuration of
the two cholorine atoms. In addition, complex 4r, bearing
strongly electron-withdrawing para-nitro substituents, on the
N-aryl moieties of the ligands, displays much lower catalytic
activity (1.20 kg PE/mmolTi · h) than its mother complex 4a.
Figure 1. Molecular structure of complex 4a with thermal ellipsoids
at the 30% probability level. Hydrogen atoms are omitted for clarity.
the activation of titanium complexes by MMAO includes two
steps: first, the alkylation of the precatalyst, and second, the
cationation of the alkyl complex.23 By mixing precatalyst
4b and dried MMAO, we found that the conformational
isomerization of the precatalyst and the cationic alkyl
complex generated on catalyst activation was very different.
As shown in Figure 6, when the Al/Ti molar ratio was about
25, the signal of an alkyl complex was generated (δ ) 5.83
ppm). If the Al/Ti molar ratio increased to 50, the signal of
the precatalyst (5.96-6.16) almost disappeared. It is clearly
observed that the methine proton (-CHdC-) of the ꢀ-e-
naminoketonato chelate ligands in the alkyl complex displays
only a single sharp signal, which means the alkyl complex
or the cation exists as only one conformation, while the
dichlorides 4b have three conformational isomers.
Interestingly, with two fluorine atoms on the N-aryl moiety
of the ligand, complexes 4e-j show more complicated
catalytic behavior compared with 4b-d. Among these
catalysts, complexes 4e-g and 4i show similar catalytic
activities toward ethylene polymerization (7.44, 7.20, 7.80,
and 7.08 kg PE/mmolTi · h, respectively), which are much
higher than 4a (4.32 kg PE/mmolTi · h), but lower than 4b-d,
and complex 4j displays somewhat lower catalytic activity
(4.08 kg PE/mmolTi · h) than 4a, while complex 4h exhibits
much lower catalytic activity (1.56 kg PE/mmolTi · h) than
4a.
Compared with complex 4b or 4d, complexes 4e-g and 4i,
which bear two fluorine atoms on each ligand, show similar
catalytic activities due to the similar electronic effect. Obviously,
the titanium center of complex 4h is more crowded than those
of complexes 4e-g, which hinders the coordination of ethylene
and considerably decreases catalytic activity toward ethylene
polymerization. Due to the stronger inductive effect of four
(23) (a) Makio, H.; Fujita, T. Macromol. Symp. 2004, 213, 221–233.
(b) Bryliakov, K. P.; Kravtsov, E. A.; Pennington, D. A.; Lancaster, S. J.;
Bochmann, M.; Brintzinger, H. H.; Talsi, E. P. Organometallics 2005, 24,
5660–5664. (c) Volkis, V.; Rodensky, M.; Lisovskii, A.; Balazs, Y.; Eisen,
M. S. Organometallics 2006, 25, 4934–4937. (d) Gornshtein, F.; Kapon,
M.; Botoshansky, M.; Eisen, M. S. Organometallics 2007, 26, 497–507.
(24) (a) Talarico, G.; Busico, V.; Cavallo, L. Organometallics 2004,
23, 5989–5993. (b) Busico, V.; Talarico, G.; Cipullo, R. Macromol. Symp.
2005, 226, 1–16.

Titanium Complexes Bearing Two ꢀ-Enaminoketonato
Organometallics, Vol. 27, No. 15, 2008 3647
Figure 2. Molecular structure of complex 4b. Occupancy factors for F5 and F5′ are 0.6 and 0.4, respectively, with thermal ellipsoids at the
30% probability level. Hydrogen atoms are omitted for clarity.
state, these complexes all adopt distorted octahedral geometry
around the titanium center. For all the complexes except for
4m, the two chlorine atoms are in a cis-position to each other.
However, for complex 4m, with a bulky CF3 in the ortho-
position of each N-aryl ring, the two chlorine atoms are in a
trans-position around the central titanium metal. In addition,
the complexes bearing two ligands of which the N-aryl is
asymmetrical, such as 4b, display not less than two conforma-
tional isomers in both the solid state and solution. With MMAO
as a cocatalyst, most titanium complexes are efficient precata-
lysts for ethylene polymerization. Catalytic activity and polymer
property are influenced significantly by the structure of the
ꢀ-enaminoketonato ligand. Both electronic effects (including
conjugative and inductive effects) and steric effects of the ligand
considerably influence the ethylene polymerization behavior of
the titanium complexes. Introduction of one fluorine atom, an
electron-withdrawing group, into each N-aryl ring causes an
enhancement in catalytic activity by about 100%. However,
further introducing fluorine atoms into the ligands results in a
decrease in catalytic activity. The presence of a fluorine atom
Figure 3. Molecular structure of complex 4m with thermal
adjacent to the imine nitrogen in the ligand suppresses ꢀ-hy-
ellipsoids at the 30% probability level. Hydrogen atoms are omitted
drogen transfer to some extent, like the case of FI catalysts.
for clarity.
Introducing a bulky substituent, even with a strong EWG, into
the ortho-position of the imine group of the ligands results in
the trans-configuration of the two chlorine atoms of the titanium
complex, and such a complex will be inactive toward ethylene
polymerization. Furthermore, the titanium complex displays only
low catalytic activity for ethylene polymerization if there is no
conjugation between the ꢀ-enaminoketonato and the substituent
linking the imine group.
Perhaps, in this case, the catalytic species is less stable, and
some deactivation reaction takes place.
In order to study the effect of ꢀ-enaminoketonato ligand
conjugacy on the catalytic activity of the titanium complex, we
synthesized complexes 4s and 4t without a conjugated phenyl.
The two complexes show only extremely low activities (0.036
and 0.048 kg PE/mmolTi · h), which clearly indicates that a
conjugated system is essential for the polymerization in this
Experimental Section
system.
General Procedures and Materials. All air- and moisture-
sensitive compounds were manipulated using standard Schlenk
techniques or in a glovebox under an argon atmosphere. NMR data
Conclusions
A series of novel titanium complexes (4b-t) bearing two
ꢀ-enaminoketonato ligands with or without electron-withdrawing
group(s) have been synthesized and characterized. In the solid
of the ligands and the complexes were obtained on a Bruker 300
MHz spectrometer at ambient temperature with CDCl3 as a solvent
(dried by MS 4 Å). The 19F NMR data of the complexes were

3648 Organometallics, Vol. 27, No. 15, 2008
Ye et al.
Table 3. Selected Bond Lengths (Å) and Angles (deg) for Complexes 4a-d, 4j, and 4m
4a
4b
4c
4d
4j
4m
Bond Distances
1.878(2)
Ti-O (1)
Ti-O (2)
Ti-N (1)
Ti-N (2)
Ti-Cl (1)
Ti-Cl (2)
1.8748(14)
1.9000(14)
2.2025(16)
2.1891(17)
2.2844(6)
2.2729(6)
1.865 (2)
1.886 (2)
2.215(3)
2.210 (3)
2.2767 (11)
2.2819 (10)
1.884(3)
1.879(3)
2.207(3)
2.197(3)
2.2761(12)
2.2663(12)
1.890 (2)
1.8737 (19)
2.183(2)
2.235 (2)
2.2637 (8)
2.2608 (9)
1.9006(15)
1.9006(15)
2.1736(19)
2.1736(19)
2.2926(6)
2.2926(6)
1.878(2)
2.197(3)
2.197(3)
2.2755(11)
2.2755(11)
Bond Angles
84.02 (15)
169.11 (16)
99.85 (8)
N (1)-Ti-N (2)
O (1)-Ti-O (2)
Cl (1)-Ti-Cl (2)
N (1)-Ti-O (1)
N (1)-Ti-O (2)
N (1)-Ti -Cl (1)
83.89 (6)
170.35 (7)
100.76 (3)
82.33 (6)
89.92 (6)
87.20 (5)
85.61 (10)
167.17 (10)
98.09 (4)
90.60 (10)
81.31 (10)
86.41 (8)
83.91(12)
168.60(13)
100.04(5)
89.42 (12)
81.53 (12)
88.73(8)
83.17 (8)
170.48 (9)
100.35 (3)
81.53 (8)
91.19 (8)
91.25 (6)
180.00(10)
180.0
180.0
83.61(7)
96.39(7)
93.18(5)
82.29 (11)
89.61 (11)
88.16 (8)
obtained with fluorobenzene as internal standard (δF ) -112.6
ppm).25 The variable-temperature 1H NMR data of complex 4b
were obtained on a Varian Unity-400 MHz spectrometer from 293
to 423 K with o-C6D4Cl2 as a solvent. Elemental analyses were
performed on a Perkin-Elmer Series II CHN/O analyzer 2400. DSC
measurements were performed on a Perkin-Elmer Pyris 1 dif-
ferential scanning calorimeter. Melting temperatures were recorded
in the second heating run at a heating rate of 10 °C/min. The
to use. The 1.6 M n-butyllithium solution in hexane was purchased
from Acros. Modified methylaluminoxane (MMAO, 7% aluminum
in heptane solution) was purchased from Akzo Nobel Chemical
Inc. Dried MMAO was prepared from commercial MMAO by
removal of the solvent in vacuo at 50 °C. Commercial ethylene
was directly used for polymerization without further purification.
Complexes 4a and 4u were synthesized according to the procedure
reported previously.17b
Synthesis of Ligands 2b-t. o-FPhNdC(CF3)CHC(t-Bu)OH
(2b). To a stirred solution of 1,1,1-trifluoro-5,5-dimethyl-2,4-
hexanedione (4.9 g, 25 mmol) in dried toluene (50 mL) were
added 2-fluoroaniline (2.22 g, 20 mmol) and p-toluenesulfonic
acid (ca. 20 mg) as a catalyst at room temperature. The mixture
was heated and refluxed, and the water formed was removed
azotropically using a Dean-Stark apparatus for 24 h. During the
stirring period, a light yellow solution was formed. Evaporation
of toluene gave a deep yellow oil. The crude product was purified
by column chromatography on silica gel with petroleum
ether-ethyl acetate (200:1) as an eluent, affording 2b (3.37 g,
11.7 mmol) as a light yellow oil in 58% yield. 1H NMR (CDCl3):
δ 11.46 (s, 1H, O-H), 7.21-7.02 (m, 4H, Ph-H), 5.90 (s, 1H,
dCH), 1.14 (s, 9H, t-Bu). 13C NMR (CDCl3): δ 206.82, 156.61,
146.60, 127.56, 127.45, 124.91, 123.10, 118.97, 114.88, 91.08,
42.04, 25.93. Anal. Calcd for C14H15F4NO: C, 58.13; H, 5.23;
N, 4.84. Found: C, 58.00; H, 5.19; N, 4.80.
j
number-average molecular weights (Mn) and polydispersity indexes
(PDI) of the polymers obtained were determined in 1,2,4-tirchlo-
robenzene at 150 °C on a high-temperature GPC using a PL-GPC
220 instrument equipped with three PLgel 10 µm mixed-B LS
columns.17
Dried diethyl ether, hexane, and toluene were purified by an M.
Braun solvent purification system (SPS). 1,1,1-Trifluoro-5,5-
dimethyl-2,4-hexanedione was synthesized according to the litera-
ture.26 Aniline derivatives for ligand synthesis were purchased from
Aldrich Chemical or Acros Organics and used without further
purification. Commercial titanium tetrachloride was distilled prior
m-FPhNdC(CF3)CHC(t-Bu)OH (2c). Compound 2c was
prepared via a procedure similar to that for 2b as a light yellow
oil in 69% yield. 1H NMR (CDCl3): δ 11.75 (s, 1H, O-H),
7.15-6.81 (m, 4H, Ph-H), 5.87 (s, 1H, dCH), 1.13 (s, 9H, t-Bu).
13C NMR (CDCl3): δ 208.22, 163.09, 147.23, 140.10, 130.43,
121.55, 120.53, 113.87, 113.20, 92.42, 43.38, 27.29. Anal. Calcd
for C14H15F4NO: C, 58.13; H, 5.23; N, 4.84. Found: C, 58.31;
H, 5.27; N, 4.79.
p-FPhNdC(CF3)CHC(t-Bu)OH (2d). Compound 2d was pre-
pared via a procedure similar to that for 2b as a light yellow
solid in 75% yield. 1H NMR (CDCl3): δ 11.65 (s, 1H, O-H),
7.13-6.69 (m, 4H, Ar), 5.84 (s, 1H, dCH), 1.18 (s, 9H, t-Bu).
13C NMR (CDCl3): δ 206.74, 160.44, 146.83, 132.94, 127.14,
119.19, 114.73, 90.03, 41.94, 26.03. Anal. Calcd for
C14H15F4NO: C, 58.13; H, 5.23; N, 4.84. Found: C, 58.24; H,
5.20; N, 4.86.
2,3-F2PhNdC(CF3)CHC(t-Bu)OH (2e). Compound 2e was
prepared via a procedure similar to that for 2b as a light yellow
oil in 71% yield. 1H NMR (CDCl3): δ 11.73 (s, 1H, O-H),
7.14-6.96 (m, 3H, Ar), 6.02 (s, 1H, dCH), 1.23 (s, 9H, t-Bu).
13C NMR (CDCl3): δ 207.88, 150.69, 146.19, 147.14, 128.02,
Figure 4. Variable-temperature 1H NMR spectra of 4b in
o-C6D4Cl2.
Scheme 3. Structures of Three Conformational Isomers of
Complex 4b
(25) Davis, F. A.; Han, W; Murphy, C. K. J. Org. Chem. 1995, 60,
4730.
(26) Schlesinger, H. I.; Brown, H. C.; Katz, J. J.; Archer, S.; Lad, R. A.
J. Am. Chem. Soc. 1953, 75, 2446.

Titanium Complexes Bearing Two ꢀ-Enaminoketonato
Organometallics, Vol. 27, No. 15, 2008 3649
Table 4. Relative Formation Energies (RFE) of the Three Different Conformational Isomers of Some Titanium Complexes (kJ/mol)
123.23, 119.98, 115.64, 114.46, 92.91, 43.02, 26.62. Anal. Calcd
for C14H14F5NO: C, 54.73; H, 4.59; N, 4.56. Found: C, 54.59;
H, 4.55; N, 4.52.
2,4-F2PhNdC(CF3)CHC(t-Bu)OH (2f). Compound 2f was
prepared via a procedure similar to that for 2b as a light yellow
oil in 61% yield. 1H NMR (CDCl3): δ 11.27 (s, 1H, O-H),
7.22-6.76 (m, 3H, Ar), 5.84(s, 1H, dCH), 1.15 (s, 9H, t-Bu).
13C NMR (CDCl3): δ 207.00, 160.72, 157.31, 146.89, 129.25,
119.04, 121.08, 110.30, 103.42, 91.14, 42.12, 25.91. Anal. Calcd
for C14H14F5NO: C, 54.73; H, 4.59; N, 4.56. Found: C, 54.67;
H, 4.63; N, 4.53.
2,5-F2PhNdC(CF3)CHC(t-Bu)OH (2g). Compound 2g was
prepared via a procedure similar to that for 2b as a light yellow
oil in 74% yield.
7.26-6.90 (m, 3H, Ar), 6.02 (s, 1H, dCH), 1.22 (s, 9H, t-Bu).
13C NMR (CDCl3): δ 207.00, 157.17, 152.46, 145.54, 126.13,
119.11, 115.47, 113.16, 113.06, 92.35, 42.20, 25.79. Anal. Calcd
for C14H14F5NO: C, 54.73; H, 4.59; N, 4.56. Found: C, 54.86;
H, 4.54; N, 4.59.
2,6-F2PhNdC(CF3)CHC(t-Bu)OH (2h). Compound 2h was
prepared via a procedure similar to that for 2b as a deep yellow
oil in 64% yield. 1H NMR (CDCl3): δ 11.03 (s, 1H, O-H),
7.30-6.91 (m, 3H, Ar), 6.02 (s, 1H, dCH), 1.23 (s, 9H, t-Bu).
13C NMR (CDCl3): δ 207.12, 158.86, 147.39, 128.22, 118.87,
114.30, 110.51, 91.59, 42.17, 25.82. Anal. Calcd for
C14H14F5NO: C, 54.73; H, 4.59; N, 4.56. Found: C, 54.66; H,
4.63; N, 4.59.
1H NMR (CDCl3): δ 11.58 (s, 1H, O-H),
3,4-F2PhNdC(CF3)CHC(t-Bu)OH (2i). Compound 2i was
prepared via a procedure similar to that for 2b as a deep yellow
solid in 72% yield. 1H NMR (CDCl3): δ 11.73 (s, 1H, O-H),
7.17-6.93 (m, 3H, Ar), 5.88 (s, 1H, dCH), 1.22 (s, 9H, t-Bu).
13C NMR (CDCl3): δ207.77, 150.01, 149.27, 147.90, 134.38,
122.32, 120.04, 117.06, 115.53, 91.81, 42.89, 26.68. Anal. Calcd
for C14H14F5NO: C, 54.73; H, 4.59; N, 4.56. Found: C, 54.57; H,
4.55; N, 4.53.
3,5-F2PhNdC(CF3)CHC(t-Bu)OH (2j). Compound 2j was
prepared via a procedure similar to that for 2b as a light yellow oil
in 80% yield. 1H NMR (CDCl3): δ 11.75 (s, 1H, O-H), 6.68-6.60
(m, 3H, Ar), 5.92 (s, 1H, dCH), 1.14 (s, 9H, t-Bu). 13C NMR
(CDCl3): δ 207.05, 161.94, 145.08, 139.59, 119.07, 107.32, 100.80,
92.22, 42.13, 25.75. Anal. Calcd for C14H14F5NO: C, 54.73; H,
4.59; N, 4.56. Found: C, 54.79; H, 4.60; N, 4.51.
2,3,4-F3PhNdC(CF3)CHC(t-Bu)OH (2k). Compound 2k was
prepared via a procedure similar to that for 2b as a light yellow oil
in 78% yield. 1H NMR (CDCl3): δ 11.38 (s, 1H, O-H), 7.07-6.91
(m, 2H, Ar), 6.01 (s, 1H, dCH) 1.22 (s, 9H, t-Bu). 13C NMR
1
Figure 5. H-1H COSY spectra of complex 4b. The resonances
at 5.8-6.2 ppm) are for the methine protons of the ligands, and
those at 6.4-7.4 ppm are for the aromatic protons.

3650 Organometallics, Vol. 27, No. 15, 2008
Ye et al.
Table 5. Polymerization of Ethylene by 4a-t/MMAO Systemsa
b
c
d
d
j
j
j
entry
complex (µmol)
polymer (g)
activity
Tjm (°C)
jjjMn (kg/mol)
jMwjMn
1
2
3
4
5
6
7
8
4a (1.0)
4b (1.0)
4c (1.0)
4d (1.0)
4e(1.0)
0.36
0.70
0.77
0.80
0.62
0.60
0.65
0.13
0.59
0.34
0.40
0.23
trace
0.40
0.59
0.68
0.63
0.10
0.03
0.04
4.32
8.40
9.24
9.60
7.44
7.20
7.80
1.56
7.08
4.08
4.80
2.76
138.6
140.0
140.7
140.1
137.8
140.9
138.1
137.3
137.1
137.2
136.7
136.0
221
285
157
228
286
249
204
79.0
180
169
251
32.0
1.8
1.5
2.1
1.9
1.6
1.6
1.6
1.5
1.9
2.0
2.1
2.3
4f (1.0)
4g (1.0)
4h(1.0)
4i (1.0)
4j (1.0)
4k (1.0)
4 L (1.0)
4m (10)
4n (1.0)
4o (1.0)
4p (1.0)
4q (1.0)
4r (1.0)
4s (10)
9
10
11
12
13
14
15
16
17
18
19
20
4.80
7.08
8.16
7.56
1.20
0.036
0.048
135.4
139.1
138.9
136.9
134.7
232
227
249
277
2.0
2.1
2.0
2.1
4t (10)
a Reaction conditions: 1 atm of ethylene pressure, Al/Ti (mol ratio) ) 2000, toluene 50 mL, polymerization for 5 min. b kg of PE/mmolTi · h.
c Melting temperature measured by DSC. d Number-average molecular weight and polydispersity index of the resultant polyethylene determined by GPC
using polystyrene standard.
m-CF3PhNdC(CF3)CHC(t-Bu)OH (2n). Compound 2n
was prepared via a procedure similar to that for 2b as a brown-
yellow solid in 79% yield. 1H NMR (CDCl3): δ 11.83 (s, 1H, O-H),
7.54-7.30 (m, 4H, Ar), 5.91 (s, 1H, dCH), 1.16 (s, 9H, t-Bu).
13C NMR (CDCl3): δ 207.11, 145.89, 137.90, 130.74, 128.60,
127.81, 122.25, 121.57, 125.62, 115.49, 91.50, 42.14, 25.90. Anal.
Calcd for C15H15F6NO: C, 53.10; H, 4.46; N, 4.13. Found: C, 53.24;
H, 4.42; N, 4.09.
p-CF3PhNdC(CF3)CHC(t-Bu)OH (2o). Compound 2o was
prepared via a procedure similar to that for 2b as a deep yellow oil
in 82% yield. 1H NMR (CDCl3): δ 12.11 (s, 1H, O-H), 7.70-7.32
(dd, 4H, Ar), 6.02(s, 1H, dCH), 1.24 (s, 9H, t-Bu). 13C NMR
(CDCl3): δ 207.16, 145.45, 140.66, 127.39, 125.27, 123.97, 123.04,
119.31, 92.09, 42.20, 25.87. Anal. Calcd for C15H15F6NO: C, 53.10;
H, 4.46; N, 4.13. Found: C, 53.01; H, 4.49; N, 4.16.
p-ClPhNdC(CF3)CHC(t-Bu)OH (2p). Compound 2p was
prepared via a procedure similar to that for 2b as a light yellow oil
in 86% yield. 1H NMR (CDCl3): δ 11.72(s, 1H, O-H), 7.25-7.04
1
Figure 6. H NMR spectra of 4b (a); 4b/dried-MMAO samples
(b, c) [Al:Ti ) 25 (b); Al:Ti ) 50 (c)]; dried-MMAO (d) (room
temperature, benzene-d6). Asterisks mark the methine proton
(-CHdC-) signals of the alkyl complex generated. The resonances
at 4.54, 4.82 ppm are for the protons of the dried MMAO, and
those at 5.86-6.16 ppm are for the methane protons of the ligands.
(dd, 4H, Ar), 5.86 (s, 1H, dCH) 1.15 (s, 9H, t-Bu). 13C NMR
(CDCl3): δ 206.95, 146.34, 135.67, 131.56, 128.17, 126.20, 119.18,
90.66, 42.08, 26.11. Anal. Calcd for C14H15ClF3NO: C, 55.00; H,
4.95; N, 4.58. Found: C, 54.84; H, 4.90; N, 4.62.
p-IPhNdC(CF3)CHC(t-Bu)OH (2q). Compound 2q was pre-
pared via a procedure similar to that for 2b as a light yellow solid
in 59% yield. 1H NMR (CDCl3): δ 11.80 (s, 1H, O-H), 7.68-6.95
(dd, 4H, Ar), 5.93 (s, 1H, dCH) 1.21 (s, 9H, t-Bu). 13C NMR
(CDCl3): δ 207.86, 146.99, 138.11, 137.89, 127.48, 120.12, 91.82,
91.37, 43.04, 27.08. Anal. Calcd for C14H15F3INO: C, 42.34; H,
3.81; N, 3.53. Found: C, 42.51; H, 3.77; N, 3.58.
(CDCl3): δ 208.43, 150.61, 148.08, 148.00, 140.45, 123.82, 123.46,
116.19, 111.45, 93.19, 43.43, 26.96. Anal. Calcd for C14H13F6NO:
C, 51.70; H, 4.03; N, 4.31. Found: C, 51.79; H, 3.99; N, 4.35.
3,4,5-F3PhNdC(CF3)CHC(t-Bu)OH (2l). Compound 2l was
prepared via a procedure similar to that for 2b as an off-white solid
in 62% yield. 1H NMR (CDCl3): δ 11.70 (s, 1H, O-H), 6.91-6.81
(m, 2H, Ar), 5.98 (s, 1H, dCH), 1.21 (s, 9H, t-Bu). 13C NMR
(CDCl3): δ 208.27, 150.88, 146.21, 138.69, 133.66, 119.98, 110.62,
92.93, 43.19, 26.84. Anal. Calcd for C14H13F6NO: C, 51.70; H,
4.03; N, 4.31. Found: C, 51.68; H, 3.97; N, 4.27.
o-CF3PhNdC(CF3)CHC(t-Bu)OH (2m). Compound 2m was
prepared via a procedure similar to that for 2b as a light yellow oil
in 67% yield. 1H NMR (CDCl3): δ 11.66 (s, 1H, O-H), 7.62-7.31
(m, 4H, Ar), 5.94 (s, 1H, dCH), 1.16 (s, 9H, t-Bu). 13C NMR
(CDCl3): δ 206.81, 146.05, 135.46, 131.37, 127.91, 125.94, 125.43,
125.15, 122.60, 119.05, 92.21, 42.06, 25.84. Anal. Calcd for
C15H15F6NO: C, 53.10; H, 4.46; N, 4.13. Found: C, 53.28; H, 4.41;
N, 4.08.
p-O2NPhNdC(CF3)CHC(t-Bu)OH (2r). Compound 2r was
prepared via a procedure similar to that for 2b as a brown oil in
1
57% yield. H NMR (CDCl3): δ 11.95 (s, 1H, O-H), 8.13-7.20
(dd, 4H, Ar), 6.01 (s, 1H, dCH) 1.12 (s, 9H, t-Bu). 13C NMR
(CDCl3): δ 208.75, 145.56, 145.29, 144.74, 125.21, 123.93, 120.50,
95.46, 44.37, 27.14. Anal. Calcd for C14H15F3N2O3: C, 53.17; H,
4.78; N, 8.86. Found: C, 53.32; H, 4.73; N, 8.82.
PhCH2NdC(CF3)CHC(t-Bu)OH (2s). Compound 2s was pre-
pared via a procedure similar to that for 2b as colorless oil in 46%
yield. 1H NMR (CDCl3): δ 10.38 (s, 1H, O-H), 7.34-7.17 (m, 5H,
Ph), 5.68 (s, 1H, dCH), 4.42 (d, 2H, CH2), 1.08 (s, 9H, t-Bu). 13
C
NMR (CDCl3): δ 207.09, 148.63, 137.19, 128.87, 127.88, 127.39,
120.38, 88.78, 48.14, 42.67, 27.19. Anal. Calcd for C15H18F3NO:
C, 63.15; H, 6.36; N, 4.91. Found: C, 63.35; H, 6.41; N, 4.94.

Titanium Complexes Bearing Two ꢀ-Enaminoketonato
Organometallics, Vol. 27, No. 15, 2008 3651
Table 6. Polymerization of Ethylene by Some Selected Catalytic Systemsa
b
entry
complex
complex dosage (µmol)
ethylene pressure (atm)
time (min)
yield (g)
activity
1
2
3
4
5
6
7
8
4d
4d
4k
4k
4b
4b
4b
4k
4k
4k
4b
4c
4f
1.0
1.0
1.0
1.0
0.2
0.5
1.0
0.5
1.0
2.0
1.0
1.0
1.0
1.0
0.5
0.5
0.5
0.5
2
4
2
4
1
1
1
1
1
1
4
4
4
4
1
1
1
1
5
5
5
5
5
5
5
5
5
5
5
5
5
1.23
1.60
0.50
0.70
0.14
0.40
0.70
0.082
0.40
0.50
0.88
1.13
0.84
0.60
0.74
0.92
0.13
0.15
14.7
19.2
6.0
8.4
8.40
9.60
8.40
1.97
4.80
3.0
10.5
13.6
10.1
7.2
9
10
11
12
13
14
15
16
17
18
4j
5
4b
4b
4k
4k
10
15
10
15
8.9
7.4
1.56
1.20
a Reaction conditions: Al/Ti (mol ratio) ) 2000, toluene 50 mL. b kg of PE/mmolTi · h.
C6H11NdC(CF3)CHC(t-Bu)OH (2t). According to the
literature,27 to a well-stirred solution of 1,1,1-trifluoro-5,5-dimethyl-
2,4-hexanedione (4.9 g, 25 mmol) and cyclohexylamine (14.3 mL,
125 mmol) in dry toluene (100 mL) under N2 was added dropwise
TiCl4 (2.0 mL, 18.75 mmol) in 30 mL of dry toluene over a period
of 1 h. The dark brown reaction mixture was stirred for 1 h and
then heated to 130 °C overnight. After being cooled to room
temperature, the reaction mixture was diluted with ether (200 mL)
and was stirred until the color of the precipitate totally changed to
light yellow. The mixture was filtered through Celite, and the
collected precipitate was washed with ether. Concentration of the
combined filtrate and washes gave the crude product, which was
fractionated, giving a 35% yield of the ligand as a light yellow oil,
98.31, 40.47, 27.67. 19F NMR (300 MHz, CDCl3): δ -60.7, -60.6,
-112.9, -111.5, -111.3, -111.2. Anal. Calcd for C28H28
Cl2F8N2O2Ti: C, 48.37; H, 4.06; N, 4.03. Found: C, 48.51; H, 4.03;
N, 3.98.
[p-FPhNdC(CF3)CHC(t-Bu)O]2TiCl2 (4d). Complex 4d was
prepared via a procedure similar to that for 4b as red crystals in
76% yield. 1H NMR (CDCl3): 7.18-6.50 (m, 8H, Ar), 5.88 (s,
1H, dCH), 0.95 (s, 18H, t-Bu). 13C NMR (CDCl3): 194.13, 161.01,
158.26, 143.29, 128.36, 123.45, 120.05, 115.60, 114.92, 98.28,
40.31, 27.65. 19F NMR (CDCl3): δ -52.1, -109.9. Anal. Calcd
for C28H28Cl2F8N2O2Ti: C, 48.37; H, 4.06; N, 4.03. Found: C, 48.19;
H, 4.01; N, 3.99.
-
[2,3-F2PhNdC(CF3)CHC(t-Bu)O]2TiCl2 (4e). Complex 4e was
prepared via a procedure similar to that for 4b as red crystals in
73% yield. 1H NMR (CDCl3): δ 7.15-6.80 (t, 1H, Ar), 6.20-5.83
(q, 2H, dCH), 1.02 (q, 18H, t-Bu). 13C NMR (CDCl3): 195.88,
159.74, 152.36, 143.73, 137.41, 136.56, 124.35, 122.89, 120.67,
98.64, 40.77, 27.62. 19F NMR (CDCl3): δ -63.0, -63.4, -136.1,
-137.4, -138.6, -145.5. Anal. Calcd for C28H26Cl2F10N2O2Ti: C,
45.99; H, 3.58; N, 3.83. Found: C, 45.83; H, 3.59; N, 3.78.
[2,4-F2PhNdC(CF3)CHC(t-Bu)O]2TiCl2 (4f). Complex 4f was
prepared via a procedure similar to that for 4b as red crystals in
84% yield. 1H NMR (CDCl3): δ 7.28-6.66 (m, 6H, Ar), 6.04-5.84
(q, 1H, dCH), 0.98 (q, 18H, t-Bu). 13C NMR (CDCl3): 195.37,
162.96, 160.27, 155.38, 130.11, 125.68, 120.65, 110.34, 104.97,
98.17, 40.65, 27.69. 19F NMR (CDCl3): δ -63.1, -63.5, -110.4,
-10.9, -111.1, -112.8. Anal. Calcd for C28H26Cl2F10N2O2Ti: C,
45.99; H, 3.58; N, 3.83. Found: C, 45.92; H, 3.56; N, 3.79.
[2,5-F2PhNdC(CF3)CHC(t-Bu)O]2TiCl2 (4g). Complex 4g was
prepared via a procedure similar to that for 4b as red crystals in
65% yield. 1H NMR (CDCl3): δ 7.15-6.72 (m, 6H, Ar), 6.05, 6.02
(d, 2H, dCH), 1.06 (q, 18H, t-Bu). 13C NMR (CDCl3): 195.89,
160.06, 156.14, 149.84, 137.05, 120.16, 116.84, 115.83, 114.40,
98.37, 40.83, 27.71. 19F NMR (CDCl3): δ -63.3, -63.6, -117.2,
-118.4, -121.8, -124.6. Anal. Calcd for C28H26Cl2F10N2O2Ti: C,
45.99; H, 3.58; N, 3.83. Found: C, 46.12; H, 3.54; N, 3.78.
[2,6-F2PhNdC(CF3)CHC(t-Bu)O]2TiCl2 (4h). Complex 4h was
prepared via a procedure similar to that for 4b as a red solid in
1
boiling at 98 °C at 4 mmHg. H NMR (CDCl3): δ 10.46 (s, 1H,
O-H), 5.62 (s, 1H, dCH), 3.44 (s, 1H, CH), 1.95-1.30 (m, 10H,
CH2), 1.16 (s, 9H, t-Bu). 13C NMR (CDCl3): δ 205.56, 147.25,
119.22, 86.18, 52.31, 41.32, 33.49, 26.14, 24.09, 23.41. Anal. Calcd
for C14H22F3NO: C, 60.63; H, 8.00; N, 5.05. Found: C, 60.47; H,
7.94; N, 5.01.
Synthesis of Titanium Complexes 4b-t. [o-FPhNd
C(CF3)CHC(t-Bu)O]2TiCl2 (4b). To a stirred solution of com-
pound o-FPhNdC(CF3)C(H)C(t-Bu)OH (2b, 1.16 g, 4 mmol) in
dried diethyl ether (20 mL) at -78 °C was added dropwise a 1.6
M n-butyllithium hexane solution (2.5 mL, 4 mmol) over 5 min.
The mixture was allowed to warm to room temperature and stirred
for 2.5 h. Then the mixture was added dropwise to TiCl4 (2 mmol)
in dried diethyl ether (30 mL) at -78 °C with stirring over 30 min.
The mixture was allowed to warm to room temperature and stirred
overnight. The evaporation of the solvent under vacuum yielded a
crude product. To the crude product was added 30 mL of dried
hexane, and the mixture was stirred for 10 min at 60 °C and then
filtered. The deep red solution was cooled to -35 °C slowly to
1
give red crystals (0.89 g) in 67% yield as the product. H NMR
(CDCl3): δ 7.30-6.92 (m, 8H, Ar), 6.00-5.79 (q, 2H, dCH), 0.95
(q, 18H, t-Bu). 13C NMR (CDCl3): 195.13, 160.24, 155.34, 136.78,
129.79, 128.70, 125.55, 123.74, 116.77, 98.91, 40.89, 28.11. 19F
NMR (CDCl3): δ -63.5, -63.2, -63.1, -115.5, -117.9, -118.4,
-121.1. Anal. Calcd for C28H28Cl2F8N2O2Ti: C, 48.37; H, 4.06;
N, 4.03. Found: C, 48.48; H, 4.01; N, 4.08.
[m-FPhNdC(CF3)CHC(t-Bu)O]2TiCl2 (4c). Complex 4c was
prepared via a procedure similar to that for 4b as red crystals in
78% yield. 1H NMR (CDCl3): δ 7.33-6.42 (m, 8H, Ar), 6.05-5.88
(q, 2H, dCH), 1.02 (q, 18H, t-Bu). 13C NMR (CDCl3): 194.29,
163.64, 158.12, 148.73, 129.63, 122.54, 119.67, 114.76, 110.12,
1
80% yield. H NMR (CDCl3): δ 7.13-6.76 (m, 6H, Ar), 5.98 (s,
1H, dCH), 0.98 (s, 18H, t-Bu). 13C NMR (CDCl3): 194.78, 160.05,
155.22, 126.95, 125.78, 117.59, 110.98, 110.70, 110.72, 97.51,
39.70, 26.61. 19F NMR (CDCl3): δ -65.9, -112.4, -113.8. Anal.
Calcd for C28H26Cl2F10N2O2Ti: C, 45.99; H, 3.58; N, 3.83. Found:
C, 45.74; H, 3.54; N, 3.87.
[3,4-F2PhNdC(CF3)CHC(t-Bu)O]2TiCl2 (4i). Complex 4i was
prepared via a procedure similar to that for 4b as red crystals in
67% yield. 1H NMR (CDCl3): δ 7.20-6.41 (m, 6H, Ar), 6.08-5.92
(27) Siemens. ASTRO, SAINT, and SADABS. Data Collection and
Processing Software for the SMART System; Siemens Analytical X-ray
Instruments Inc.: Madison, WI, 1996.

3652 Organometallics, Vol. 27, No. 15, 2008
Ye et al.
(q, 2H, dCH), 1.06 (q, 18H, t-Bu). 13C NMR (CDCl3): 195.26,
159.95, 152.23, 147.26, 143.72, 123.24, 121.24, 118.51, 116.80,
112.29, 40.91, 27.92. 19F NMR (CDCl3): δ -60.4, -134.6, -136.3,
-138.9. Anal. Calcd for C28H26Cl2F10N2O2Ti: C, 45.99; H, 3.58;
N, 3.83. Found: C, 45.81; H, 3.53; N, 3.86.
[3,5-F2PhNdC(CF3)CHC(t-Bu)O]2TiCl2 (4j). Complex 4j was
prepared via a procedure similar to that for 4b as red crystals in
65% yield. 1H NMR (CDCl3): δ 6.77 (d, 2H, Ar), 6.63 (t, 2H, Ar),
6.12 (d, 2H, Ar), 5.94 (s, 2H, dCH), 1.00 (q, 18H, t-Bu). 13C NMR
(CDCl3): 195.10, 163.85, 160.54, 158.52, 149.27, 120.87, 110.90,
106.36, 102.44, 98.29, 40.58, 27.63. 19F NMR (CDCl3): δ -60.7,
-107.9, -109.9. Anal. Calcd for C28H26Cl2F10N2O2Ti: C, 45.99;
H, 3.58; N, 3.83. Found: C, 45.78; H, 3.55; N, 3.79.
119.35, 98.75, 92.02, 40.77, 28.05. 19F NMR (CDCl3): δ -60.3.
Anal. Calcd for C28H28Cl2F6I2N2O2Ti: C, 36.91; H, 3.10; N, 3.07.
Found: C, 36.78; H, 3.04; N, 3.03.
[p-O2NPhNdC(CF3)CHC(t-Bu)O]2TiCl2 (4r). Complex 4r was
prepared via a procedure similar to that for 4b as red crystals in
66% yield. 1H NMR (CDCl3): δ 6.77 (d, 2H, Ar), 6.63 (t, 2H, Ar),
6.12 (d, 2H, Ar), 5.94 (s, 1H, dCH), 1.00 (s, 18H, t-Bu). 19F NMR
(CDCl3): δ -60.3. Anal. Calcd for C28H28Cl2F6N4O6Ti: C, 44.88;
H, 3.77; N, 7.48. Found: C, 44.62; H, 3.73; N, 7.53.
[PhCH2NdC(CF3)CHC(t-Bu)O]2TiCl2 (4s). Complex 4s was
prepared via a procedure similar to that for 4b as a black solid in
73% yield. 1H NMR (CDCl3): δ 7.39-7.07 (m, 10H, Ar), 6.11 (s,
2H, dCH), 4.87 (d, 2H, CH2), 4.65 (d, 2H, CH2), 5.94 (s, 1H,
dCH), 1.04 (q, 18H, t-Bu). 13C NMR (CDCl3): 194.01, 160.27,
138.13, 128.55, 127.23, 126.56, 121.27, 99.34, 58.26, 40.56, 27.86.
19F NMR (CDCl3): δ -62.6. Anal. Calcd for C30H34Cl2F6N2O2Ti:
C, 52.42; H, 4.99; N, 4.08. Found: C, 52.29; H, 4.95; N, 4.03.
[C6H11NdC(CF3)CHC(t-Bu)O]2TiCl2 (4t). Complex 4t was
prepared via a procedure similar to that for 4b as red crystals in
[2,3,4-F3PhNdC(CF3)CHC(t-Bu)O]2TiCl2 (4k). Complex 4k
was prepared via a procedure similar to that for 4b as red crystals
1
in 4k in 67% yield. H NMR (CDCl3): δ 7.08-6.86 (m, 4H, Ar),
6.23-5.88 (q, 2H, dCH), 1.11 (q, 18H, t-Bu). 13C NMR (CDCl3):
196.85, 160.63, 151.93, 148.56, 133.25, 123.20, 120.97, 117.17,
111.26, 98.72, 41.27, 27.98. 19F NMR (CDCl3): δ -62.9, -63.1,
-63.5, -133.0, -134.6, -139.3, -157.0, -159.3. Anal. Calcd for
C28H24Cl2F12N2O2Ti: C, 43.83; H, 3.15; N, 3.65. Found: C, 43.71;
H, 3.09; N, 3.68.
1
61%. H NMR (CDCl3): δ 6.29 (s, 2H, dCH), 3.85 (s,2H, CH),
2.05-1.35 (m, 20H, CH2), 1.05 (s, 18H, t-Bu). 19F NMR (CDCl3):
δ -61.1. Anal. Calcd for C28H42Cl2F6N2O2Ti: C, 50.09; H, 6.31;
N, 4.17. Found: C, 49.86; H, 6.25; N, 4.24.
[3,4,5-F3PhNdC(CF3)CHC(t-Bu)O]2TiCl2 (4l). Complex 4l
was prepared via a procedure similar to that for 4b as red crystals
in 70% yield. 1H NMR (CDCl3): δ 6.97 (m, 2H, Ar), 6.24 (m, 2H,
Ar), 6.05 (s, 2H, dCH), 1.10 (s, 18H, t-Bu). 13C NMR (CDCl3):
196.05, 159.38, 152.66, 149.23, 142.66, 138.99, 114.85, 112.40,
107.72, 98.57, 40.99, 27.90. 19F NMR (CDCl3): δ -60.5, -131.7,
-132.6, -133.6, -161.1. Anal. Calcd for C28H24Cl2F12N2O2Ti: C,
43.83; H, 3.15; N, 3.65. Found: C, 43.67; H, 3.10; N, 3.61.
[o-CF3PhNdC(CF3)CHC(t-Bu)O]2TiCl2 (4m). Complex 4m
was prepared via a procedure similar to that for 4b as red crystals
X-ray Crystallography. Single crystals of complexes 4a-d, 4j,
and 4m suitable for X-ray structure determination were grown from
a hexane solution at -20 °C in a glovebox, thus maintaining a
dry, O2-free environment. X-ray intensities of complexes 4a-d,
4j, and 4m were collected on a Bruker Smart CCD diffractometer
equipped with graphite-monochromated Mo KR radiation (λ)
0.71073 Å) at 187 K. Empirical absorption corrections were applied
to the data using the SADABS program.28 The structures were
solved by the direct method and refined by full-matrix least-squares
on F2 using the SHELXTL-97 program.29 All of the non-hydrogen
atoms were refined anisotropically. Crystallographic data and other
pertinent information for 4a-d, 4j, and 4m are summarized in Table
2. Selected bond lengths and angles are listed in Table 3.
Computational Details. Initial conformations of 4a-d, 4j, and
4m were obtained from their crystal data collected on an X-ray
diffractometer and taken as input structures for geometry optimiza-
tion in the Amsterdam Density Functional program package (ADF
2006.1b).30 The thus located low-energy conformers were modified
to build the initial structures of isomers and other catalysts, which
are optimized in ADF again. The calculations were carried out at
the level of gradient-corrected density functional theory using the
Becke-Perdew exchange-correlation functional.31 A standard
double STO basis set with polarization function (DZP) was
employed for all atoms except Ti, which was described by a triple-ꢁ
plus polarization STO basis (TZP). The frozen core approximation
was employed for the 1s electrons of the C, O, and F atoms, up to
and including the 2p of the Cl atoms and the 3p electrons of Ti.
All stationary points were optimized without any symmetry and
geometry constraints. Numerical integrations were performed with
the integration precision of 4.0, and the default ADF values were
chosen for the self-consistent-field (SCF) and geometry optimization
convergence criteria.
1
in 76% yield. H NMR (CDCl3): δ 7.69-7.33 (m, 8H, Ar), 6.01
(s, 2H, dCH), 0.89 (s, 18H, t-Bu). 13C NMR (CDCl3): 195.34,
157.68, 145.18, 136.43, 132.43, 131.17, 129.51, 128.23, 125.39,
119.38, 98.86, 41.02, 27.66. 19F NMR (CDCl3): δ -61.0, -62.5.
Anal. Calcd for C30H28Cl2F12N2O2Ti: C, 45.31; H, 3.55; N, 3.52.
Found: C, 45.21; H, 3.51; N, 3.47.
[m-CF3PhNdC(CF3)CHC(t-Bu)O]2TiCl2 (4n). Complex 4n
was prepared via a procedure similar to that for 4b as red crystals
1
in 82% yield. H NMR (CDCl3): δ 7.61-6.92 (m, 8H, Ar), 5.98
(q, 2H, dCH), 0.95 (q, 18H, t-Bu). 13C NMR (CDCl3): 194.50,
158.69, 147.83, 131.05, 130.62, 129.65, 125.29, 123.57, 120.69,
118.02, 98.12, 40.44, 27.40. Anal. Calcd for C30H28Cl2F12N2O2Ti:
C, 45.31; H, 3.55; N, 3.52. Found: C, 45.18; H, 3.52; N, 3.48.
[p-CF3PhNdC(CF3)CHC(t-Bu)O]2TiCl2 (4o). Complex 4o was
prepared via a procedure similar to that for 4b as red crystals in
1
86% yield. H NMR (CDCl3): δ 7.55 (d, 2H, Ar), 7.50 (d, 2H,
Ar), 7.32 (d, 2H, Ar), 6.77 (d, 2H, Ar), 5.88 (s, 2H, dCH), 0.90
(s, 18H, t-Bu). 13C NMR (CDCl3): 194.84, 158.20, 150.40, 129.20,
127.28, 125.76, 125.53,125.24, 122.43, 118.29, 98.27, 40.41, 27.48.
19F NMR (CDCl3):
δ -60.3, -62.0. Anal. Calcd for
C30H28Cl2F12N2O2Ti: C, 45.31; H, 3.55; N, 3.52. Found: C, 45.19;
H, 3.52; N, 3.47.
[p-ClPhNdC(CF3)CHC(t-Bu)O]2TiCl2 (4p). Complex 4p was
prepared via a procedure similar to that for 4b as red crystals in
1
71% yield. H NMR (CDCl3): δ 7.24 (d, 2H, Ar), 7.22 (m, 4H,
(28) Sheldrick, G. M. SHELXL-97, A Program for Crystal Structure
Refinement; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(29) (a) Denmark, S. E.; Rivera, I. J. Org. Chem. 1994, 59, 6887–6889.
(b) Dai, W; Srinivasan, R; Katzenellenbogen, J. A. J. Org. Chem. 1989,
54, 2204–2208.
(30) (a) ADF2006.01; SCM, Theoretical Chemistry, Vrije Universiteit:
Amsterdam, The Netherlands. (b) te Velde, G.; Bickelhaupt, F. M.; van
Gisbergen, S. J. A.; Fonseca Guerra, C.; Baerends, E. J.; Snijders, J. G.;
Ziegler, T. J. Comput. Chem. 2001, 22, 931. (c) Fonseca Guerra, C.;
Snijders, J. G.; te Velde, G.; Baerends, E. J. Theor. Chem. Acc. 1998, 99,
391.
Ar), 6.55 (d, 2H, Ar), 5.88 (s, 1H, dCH), 0.95 (s, 18H, t-Bu). 13
C
NMR (CDCl3): 194.79, 158.55, 146.21, 132.88, 129.05, 128.43,
123.61, 119.25, 98.74, 40.72, 27.99. 19F NMR (CDCl3): δ -60.3.
Anal. Calcd for C28H28Cl4F6N2O2Ti: C, 46.18; H, 3.88; N, 3.85.
Found: C, 46.02; H, 3.83; N, 3.88.
[p-IPhNdC(CF3)CHC(t-Bu)O]2TiCl2 (4q). Complex 4q was
prepared via a procedure similar to that for 4b as red crystals in
1
76% yield. H NMR (CDCl3): δ 7.67 (d, 2H, Ar), 7.02 (m, 4H,
Ar), 6.45 (d, 2H, Ar), 5.93 (s, 1H, dCH), 1.04 (s, 18H, t-Bu). 13
C
(31) (a) Becke, A. Phys. ReV. A 1988, 38, 3098. (b) Perdew, J. P. Phys.
ReV. B 1986, 34, 7406–7406. (c) Perdew, J. P. Phys. ReV. B 1986, 33, 8822.
NMR(CDCl3):194.85,158.36,147.48,137.93,137.32,129.11,124.28,

Titanium Complexes Bearing Two ꢀ-Enaminoketonato
Organometallics, Vol. 27, No. 15, 2008 3653
1
Ethylene Polymerization. Polymerization was carried out under
atmospheric pressure in toluene in a 150 mL glass reactor equipped
with a mechanical stirrer. Toluene (50 mL) was introduced into
the argon-purged reactor and stirred vigorously (600 rpm). The
toluene was kept at a prescribed polymerization temperature, and
then the ethylene gas feed was started. After 15 min, the polym-
erization was initiated by the addition of a heptane solution of
MMAO and a toluene solution of one of the titanium complexes
into the reactor with vigorous stirring (600 rpm). After a prescribed
time, isobutyl alcohol (10 mL) was added to terminate the
polymerization reaction, and the ethylene gas feed was stopped.
The resulting mixture was added to the acidic methanol. The solid
polyethylene was isolated by filtration, washed with methanol, and
dried at 60 °C for 24 h in a vacuum oven.
transferred into a Young’s Teflon NMR tube to measure the H
NMR spectroscopic data at room temperature (25 °C).
Acknowledgment. The authors are grateful for a subsidy
provided by the National Natural Science Foundation of
China (Nos. 20734002 and 50525312) and by the Special
Funds for Major State Basis Research Projects (No.
2005CB623800) from the Ministry of Science and Technol-
ogy of China.
Supporting Information Available: CIF files giving complete
X-ray experimental details and tables of bond lengths, angles, and
positional parameters for complexes 4a-d, 4j, and 4m. The
molecular structures of 4c, 4d, and 4j are shown in Figures S1-S3,
respectively. These materials are available free of charge via the
Internet at http://pubs.acs.org.
Study of the Active Intermediates by 1H NMR. A solution of
4b (3.5 mg, 5 µmol) in benzene-d6 was added dropwise to a solution
of dried MMAO (7.3 mg, 125 µmol or 14.6 mg, 250 µmol) in
benzene-d6. The resulting mixture was shaken and was then
OM700803U