Syntheses, structure and ethylene polymerization behavior of β-diiminato titanium complexes

Article abstract of DOI:10.1016/j.jorganchem.2005.12.053

A series of new titanium complexes bearing β-diiminato ligands [(Ph)NC(R₁)CHC(R₂)N(Ph)]₂TiCl₂ (4a: R₁ = R₂ = CH₃; 4b: R₁ = R ₂ = CF₃; 4c: R₁

Full text of DOI:10.1016/j.jorganchem.2005.12.053

Journal of Organometallic Chemistry 691 (2006) 2023–2030
www.elsevier.com/locate/jorganchem
Syntheses, structure and ethylene polymerization behavior
of b-diiminato titanium complexes
*
Li-Ming Tang, Yi-Qun Duan, Xiao-Fang Li, Yue-Sheng Li
State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences,
5625# Renmin Dajie, Changchun, Jilin 130022, China
Graduate School of Chinese Academy of Sciences, China
Received 21 July 2005; received in revised form 16 December 2005; accepted 26 December 2005
Available online 13 February 2006
Abstract
A series of new titanium complexes bearing b-diiminato ligands [(Ph)NC(R1)CHC(R2)N(Ph)]2TiCl2 (4a: R1 = R2 = CH3; 4b:
R1 = R2 = CF3; 4c: R1 = Ph, R2 = CH3; 4d: R1 = Ph, R2 = CF3) has been synthesized and characterized. X-ray crystal structures reveal
that complexes 4a and 4c adopt distorted octahedral geometry around the titanium center. With modified methylaluminoxane (MMAO)
as a cocatalyst, complexes 4a–d are active catalysts for ethylene polymerization, and produce high molecular weight polyethylenes. Cat-
alyst activities and the molecular weights of polymers are considerably influenced by the steric and electronic effects of substituents on the
catalyst backbone under the same polymerization condition. With the strong electron-withdrawing groups (CF3) at R1 or/and R2 posi-
tion, complexes 4b and 4d show higher activities than complexes 4a and 4c, respectively.
ꢀ 2006 Elsevier B.V. All rights reserved.
Keywords: Titanium complex; Catalyst; Ethylene; Polymerization
1. Introduction
Recently, our group reported a type of titanium cata-
lysts featuring unsymmetrical bidentate b-enaminoketo-
nato ligands for olefin polymerization. By the variation
In recent years, a significant amount of attentions have
been concentrated on the design and synthesis of highly
active, well-defined or single-site transition metal catalysts
for olefin polymerization [1–3]. Due to the extensive inves-
tigation of complexes with either cyclopentadienyl (Cp) or
indenyl (In) ligands, the new non-Cp ligand environment
has currently attracted more and more interests. For non-
metallocene system with group 4 metals, complexes derived
from benzamidine [4,5], diamine [6–9], phosphine-imide
[10], pyrrolide-imine [11,12] indolide-imine [13], phenoxy-
imine [14–24] and imido [25,26] ligands are reported, many
of them show activities comparable to those of metallocene
catalysts and in some cases promote living polymerization
of a-olefins.
of substituents, we got
a highly efficient catalyst,
[(Ph)NC(CF3)C(H)C(Ph)O]2TiCl2, for the quasi-living eth-
ylene polymerization and ethylene/cyclopentene copoly-
merization [27–29]. The fact that the variation of the
ligand structure may lead to profound changes in the per-
formance of catalyst and the property of polymer prompts
us to introduce the bidentate b-diiminato ligand to group 4
transition metal chemistry. b-Diiminato ligands have been
known for many years and were initially applied in spectro-
scopic studies of coordination compounds [30–32]. In the
last few years b-diiminato has been used as neutral or
monoanionic ligands in wide range of transition metal
[33–47], main group element [48–52] and lanthanide [53]
complexes, some of which display activity for olefin
polymerization.
Although b-diiminato ligand has the isoelectronic rela-
tionship with cyclopentadienyl anion, and the steric and
*
Corresponding author. Fax: +86 431 5685653.
E-mail address: ysli@ciac.jl.cn (Y.-S. Li).
0022-328X/$ - see front matter ꢀ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.12.053

2024
L.-M. Tang et al. / Journal of Organometallic Chemistry 691 (2006) 2023–2030
electronic properties of b-diiminato ligand can be readily
altered through an appropriate choice of b-diketone, no
report on bis(b-diiminato)titanium (IV) catalysts for olefin
polymerization has been published. Jin and Novak tried to
synthesize (b-diiminato)TiCl3 using TiCl4 Æ 2THF, but did
not come true [40]. Budzelaar [36] and Theopold [37]
reported, respectively, Ti(III) complexes which display only
low activities towards olefin polymerization. Collins and
co-workers [34,39] and Jin and Novak [40] prepared, inde-
pendently, the zirconium (IV) complexes with b-diiminato
ligand, and all the complexes show low to moderate cata-
lytic activities towards olefin polymerization. In previous
research work, we found that the introduction of elec-
tron-withdrawing group can increase the activity of b-ena-
minoketonato titanium catalyst [27,29]. This urges us to
investigate the effect of the structure of b-diiminato ligand
on the performance of titanium catalyst. Herein, we report
the syntheses, structures and ethylene polymerization
behaviors of [(Ph)NC(R1)CHC(R2)N(Ph)]2TiCl2.
The crystals of complexes 4a and 4c suitable for X-ray
structure determination were grown from dichlorometh-
ane–hexane solution. The crystallographic data, collec-
tion parameters, and refinement parameters are listed in
˚
Table 1, the selected bond lengths (A) and bond angles
(ꢁ) for complexes 4a and 4c are summarized in Tables
2 and 3, and the molecular structures are shown in Figs.
1 and 2. In solid state, complex 4a adopts distorted octa-
hedral geometry around the titanium center with cis
chlorine atoms, in which the N–Ti–N angles involving
the bis(b-diiminato) ligands deviate from 90ꢁ (N(1)–Ti–
N(2) = 84.85(5)ꢁ, N(3)–Ti–N(4) = 84.67(5)ꢁ). The trans
influence of the chloride is clearly seen by the shorter
Ti–N(3) and Ti–N(1) bond lengths of 2.0994(14) and
˚
2.0857(13) A compared with the Ti–N(2) and Ti–N(4)
˚
distances of 2.1088(14) and 2.1010(13) A, respectively.
Analogously, complex 4c also displays a distorted octa-
hedral geometry at the metal center with two cis chlorine
atoms at an angle of 90.67(7)ꢁ. The angles involving the
metal center and the bis(b-diiminato) ligands deviate
from 90ꢁ (N(1)–Ti–N(2) = 83.86(11)ꢁ). The longer bond
2. Results and discussion
˚
distance Ti–N(2) = 2.130(3) A compared with Ti–N(1) =
˚
2.1. Synthesis and characterization of complexes
2.060(3) A indicates the similar trans influence, but it is
stronger than 4a. Moreover, complex 4c possesses wider
A general synthetic route for new titanium complexes
used in this study is shown in Scheme 1. b-Diimine (2a–
d) were obtained in good yields (2a, 92%; 2b, 65%; 2c,
61%; 2d, 68%) by the condensation of corresponding b-
diketone with aniline in toluene using concentrated hydro-
chloride or titanium tetrachloride as a catalyst. The desired
titanium complexes 4a–d were synthesized under mild con-
ditions in good yields (4a, 58%; 4b, 61%; 4c, 59%; 4d, 63%)
via the reaction of TiCl4 with 2 equivalents of the lithium
salts of b-diimine 3a–d in dry diethyl ether. The resulting
complexes were obtained as dark red to brown crystallized
solids.
Table 1
Crystal data and structure refinements of complexes
Complex
4a
4c
Empirical formula
Formula weight
Crystal system
Space group
C34H34Cl2N4Ti
C44H38Cl2N4Ti Æ 2CH2Cl2
617.45
Monoclinic
P21/n
12.9853(11)
15.3373(13)
16.3887(14)
106.455(10)
3130.3(5)
4
911.44
Orthorhombic
Pbcn
˚
a (A)
11.829(3)
19.862(7)
18.891(6)
90
4438(2)
4
˚
b (A)
˚
c (A)
b (ꢁ)
3
˚
V (A )
Z
Dcalc (Mg/m3)
Absorption
coefficient (mmꢀ1
F(000)
1.310
0.474
1.364
0.591
)
1288
1880
Crystal size (mm)
h Range for data
collection (ꢁ)
Reflections
collected
0.71 · 0.18 · 0.14
1.86–26.01
0.52 · 0.46 · 0.44
2.00–26.02
Ph
R2
2a-d
n-BuLi
Ph
R2
O
O
Ph
R1
NH
N
Ph-NH
2
R1
R2
17285
5515
Independent
6118 (0.0151)
4380 (0.0336)
Psi-scan
reflections (Rint
)
Ph
Absorption correction
Semi-empirical
from equivalents
0.9354 and 0.7288
R2
R1
N
N
Ph
4a-d
Ph
Cl
Cl
NLi
N
Ti
Maximum and
minimum
transmission
Data/restraints/
parameters
0.7809 and 0.7485
TiCl
4
2
R1
6118/0/374
4380/2/253
3a-d
Goodness-of-fit on F2
Final R indices
[I > 2r(I)]: R1, wR2
Largest difference
in peak and hole
1.039
0.0358, 0.0988
0.977
0.0549, 0.0665
a: R1=R2=CH3
b: R1=R2=CF3
c: R1=Ph R2=CH3
d: R1=Ph R2=CF3
0.333 and ꢀ0.182
0.405 and ꢀ0.555
ꢀ3
˚
(e A
)
Scheme 1.

L.-M. Tang et al. / Journal of Organometallic Chemistry 691 (2006) 2023–2030
2025
The X-ray structure analyses and the 1H NMR patterns
of the titanium complexes suggest that complexes 4a and4c
adopt the configuration of cis Cl–Cl. However, chelate
complexes [N,N]2MCl2 probably form five isomers, as
shown in Scheme 2. Fujita and colleagues calculated the
relative formation energies (RFEs) of the titanium com-
plexes bearing two phenoxy-iminato, indolide-iminato or
pyrrolide-iminato chelate ligands which are similar to b-
diiminato ligands, and found that isomer cis-I displays
the lowest RFE, and isomers cis-II and cis-III also exhibit
relatively low RFEs, while isomers trans-I and trans-II
show quite high RFEs [11,13,15]. This means that the tita-
nium complexes bearing two b-diiminato chelate ligands
tend to form isomer cis-I.
Table 2
˚
Selected bond lengths (A) and angles (ꢁ) for complex 4a
˚
Bond distance (A)
Ti–N(1)
Ti–N(2)
Ti–N(3)
Ti–N(4)
Ti–Cl(1)
Ti–Cl(2)
N(1)–C(7)
N(1)–C(1)
2.0857(13)
2.1088(14)
2.0994(14)
2.1010(13)
2.3146(5)
2.3124(5)
1.348(2)
1.452(2)
Bond angles (ꢁ)
N(1)–Ti–N(3)
N(1)–Ti–N(4)
N(3)–Ti–N(4)
N(1)–Ti–N(2)
N(3)–Ti–N(2)
N(4)–Ti–N(2)
N(1)–Ti–Cl(2)
N(3)–Ti–Cl(2)
N(4)–Ti–Cl(2)
N(2)–Ti–Cl(2)
N(1)–Ti–Cl(1)
N(3)–Ti–Cl(1)
N(4)–Ti–Cl(1)
N(2)–Ti–Cl(1)
Cl(2)–Ti–Cl(1)
C(7)–N(1)–C(1)
C(7)–N(1)–Ti
C(1)–N(1)–Ti
87.43(5)
90.88(5)
84.67(5)
84.85(5)
168.49(5)
86.93(5)
178.70(4)
93.57(4)
90.05(4)
94.29(4)
91.20(4)
94.78(4)
177.82(4)
93.91(4)
87.881(19)
115.84(13)
121.81(11)
122.32(10)
The 1H NMR spectra of complexes 4a–d display a single
sharp resonance for the methine proton (@CH–) of the b-
diiminato chelate ligands. 19F NMR spectra of 4d give
two peaks at 50.84 and 51.69 with the ratio of 6:1, suggest-
ing that there exits a few isomers of 4d. 19F NMR spectra
of 4b displaying three peaks also indicates the existence of
isomers.
2.2. Ethylene polymerization
With modified methylaluminoxane (MMAO) as a cocat-
alyst, new titanium complexes 4a–d have been investigated
as the catalysts for ethylene polymerization at room tem-
perature. The results are listed in Table 4. Of the four cat-
alyst systems, complex 4b exhibited the highest catalytic
activity of 312 kg PE/molTi Æ h (Entry 2), followed by com-
plex 4d (288 kg PE/molTi Æ h, Entry 4), 4c (38.4 kg PE/mol-
Ti Æ h, Entry 3) and 4a (2.53 kg PE/molTi Æ h, Entry 1).
Compared 4b with 4a, and 4c with 4a, the introduction
of strong electron-withdrawing group (CF3) at R1 or/and
R2 position is able to considerably increase the polymeriza-
tion activities with orders of magnitude. Furthermore, with
weaker electron-withdrawing group (Ph) at the R1 posi-
tion, complex 4b displays higher activity than complex
4a. These consequences are consistent with our previous
report [24]. The result of ethylene polymerization with
(nacnac)TiCl2 (nacnac = [(Ph)NC(Me)CHC(Me)N(Ph)])
is also listed in Entry 11 of Table 4 [37]. Although the activ-
ity of complex 4a is lower than that of (nacnac)TiCl2, com-
plexes 4b and 4d display much higher activities towards
ethylene polymerization compared with (nacnac)TiCl2.
With the increase of reaction temperature, the activity of
catalyst 4b increases and reaches maximal value of 528 kg
PE/molTi Æ h at ca. 25 ꢁC, and then decreases gradually
(Entries 2, 8–10 in Table 4) due to thermal decomposition
of the catalyst. In addition, the data of entries 2, 5–7 in
Table 4 show that the increase of Al/Ti molar ratio from
1000 to 1500 brings on the enhancement in activity, but
further increasing Al/Ti molar ratio decreases catalyst
activity.
Table 3
˚
Selected bond lengths (A) and angles (ꢁ) for complex 4c
˚
Bond distance (A)
Ti–N(1)
Ti–N(2)
Ti–Cl(1)
N(1)–C(1)
N(1)–C(4)
2.060(3)
2.130(3)
2.3190(13)
1.360(4)
1.438(4)
Bond angles (ꢁ)
N(1)–Ti–N(1)#1
N(1)–Ti–N(2)#1
N(1)#1–Ti–N(2)#1
N(1)–Ti–N(2)
N(1)#1–Ti–N(2)
N(2)#1–Ti–N(2)
N(1)–Ti–Cl(1)#1
N(1)#1–Ti–Cl(1)#1
N(2)#1–Ti–Cl(1)#1
N(2)–Ti–Cl(1)#1
N(1)–Ti–Cl(1)
N(1)#1–Ti–Cl(1)
N(2)#1–Ti–Cl(1)
N(2)–Ti–Cl(1)
Cl(1)#1–Ti–Cl(1)
C(1)–N(1)–C(4)
C(1)–N(1)–Ti
89.19(17)
92.36(12)
83.86(11)
83.86(11)
92.36(12)
174.70(18)
175.21(9)
90.27(9)
92.32(9)
91.41(9)
90.27(9)
175.21(9)
91.41(9)
92.32(9)
90.67(7)
114.4(3)
122.1(2)
122.2(3)
C(4)–N(1)–Ti
Cl–Ti–Cl (90.67(7)ꢁ) angle relative to the complex 4a
(Cl–Ti–Cl = 87.881(19)ꢁ). The differences in bond lengths
and angles probably originate from the steric and elec-
tronic effects.
The polyethylenes produced by 4a–d/MMAO systems
exhibit high molecular weights (62.3–410.7 kg/mol). The
data listed in Table 4 indicate that the molecular weight

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L.-M. Tang et al. / Journal of Organometallic Chemistry 691 (2006) 2023–2030
Fig. 1. Molecular structure of complex 4a with thermal ellipsoids at 30% probability level. Hydrogen atoms are omitted for clarity.
Fig. 2. Molecular structure of complex 4c with thermal ellipsoids at 30% probability level. Hydrogen atoms are omitted for clarity.
of the polyethylene obtained decreases with the increase of
reaction temperature and Al/Ti molar ratio due to increas-
ing b-H elimination reaction and chain transfer reaction to
aluminum compounds. Although b-enaminoketonato tita-
nium complex [(Ph)NC(CF3)C(H)C(Ph)O]2TiCl2 shows
characteristic of quasi-living polymerization [27], b-diimi-
nato titanium catalysts 4a–d produce the polymers with rel-
ative broader molecular weight distribution and do not

L.-M. Tang et al. / Journal of Organometallic Chemistry 691 (2006) 2023–2030
2027
N1
N2
N1
donor titanium (or zirconium) complexes reported [11–13,
25,40]. Melting temperatures (Tms values 134.9–137.8 ꢁC)
measured by DSC also prove the polymer as typical linear
polyethylene.
N2
Cl
N1
Cl
N2
Cl
M
M
M
N1
Cl
N1
Cl
N2
Cl
N2
N2
N1
cis-I
cis-II
cis-III
3. Conclusion
Cl
Ar
M = Ti
N1
Cl
R1
N1
N2
N1
N1
N1
M
Cl
M
Cl
N2
N1
A series of new titanium complexes bearing b-diiminato
ligands (4a–d) have been synthesized, characterized, and
are found to be efficient catalysts for ethylene polymeriza-
tion with MMAO as a cocatalyst under mild conditions.
Polymer yields, catalyst activities as well as molecular
weight are considerably influenced by the steric and elec-
tronic effects of substituents on the catalyst backbone
under the same polymerization condition. With the elec-
tron-withdrawing group (CF3) at R1 or/and R2 position,
complexes 4b and 4d show higher activities than complexes
4a and 4c, respectively.
N2
N2
N2
Ar
N2
R2
trans-II
Scheme 2.
trans-I
reveal the similar characteristic (Entry 2 in Table 4,
PDI = 2.87 for catalyst 4b; Entry 4, PDI = 2.94 for catalyst
4d). High-temperature 13C NMR analysis indicates that the
polymers possess linear structure with virtually no branch-
ing (see Fig. 3), which is in accord with the results of N,N-
Fig. 3. 13C NMR spectrum of polyethylene prepared with complex 4b.
Table 4
The polymerization of ethylene with 4a–d/MMAO catalyst systemsa
b
d
d
Entry
Complex
(lmol)
Al/Ti
(mol ratio)
T (ꢁC)
Pressure
(atm)
Reaction
time (min)
Polymer
(g)
Activity
(kg PE/molTi Æ h Æ atm)
Tm
(ꢁC)
Mgc(Mw
)
Mw=Mn
(kg/mol)
1
2
3
4
5
6
7
8
9
4a (10)
4b (5)
4c (10)
4d (5)
4b (5)
4b (5)
4b (5)
4b (5)
4b (5)
4b (5)
1000
1000
1000
1000
1200
1500
2000
1500
1500
1500
130
25
25
25
25
25
25
25
0
15
1
15
1
1
1
1
1
1
1
30
10
30
10
10
10
10
10
10
10
60
0.19
0.26
2.88
0.24
0.34
0.44
0.38
0.15
0.23
0.07
3.4
2.53
312
38.4
288
408
528
456
180
276
84
135.5
136.1
135.3
137.5
134.3
135.7
137.2
136.8
134.1
135.0
410.7
210.8 (312)
366.3
212.6 (305)
189.8 (298)
163.2
141.1
324.4
76.8
62.3
ND
2.87
ND
2.94
3.32
ND
ND
ND
ND
ND
28.6
50
70
Below 60
10
11
a
e
(nacnac)TiCl2
20
11.3
818
Reaction conditions: toluene 50 mL.
b
c
Melting temperature determined by DSC.
The intrinsic viscosity was measured in decalin.
Determined by GPC using polystyrene standard.
See Ref. [37].
d
e

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L.-M. Tang et al. / Journal of Organometallic Chemistry 691 (2006) 2023–2030
4. Experimental
Calc. for C17H18N2: C, 81.56; H, 3.38; N, 7.82. Found:
C, 81.33; H, 3.45; N, 7.74%.
4.1. General procedures and materials
4.2.3. (Ph)NC(CF3)CHC(CF3)NH(Ph) (2b)
All work involving air and/or moisture-sensitive com-
pounds was carried out using standard Schlenk tech-
niques unless otherwise noted. NMR spectra were
recorded on a Bruker 300 MHz spectrometer at ambient
temperature. 1H NMR and 13C NMR chemical shifts
were referenced to residual 1H and 13C signals of the
deuterated solvents. 19F NMR chemical shifts were refer-
enced to C6F6. The DSC measurements were performed
on a Perkin–Elmer Pyris 1 Differential Scanning Calo-
rimeter at a rate of 10 ꢁC/min. The weight-average
molecular weight ðMwÞ and the polydispersity index
(PDI) of polymer samples were determined via high tem-
perature GPC according to the procedure reported previ-
ously [27]. Elemental analyses were recorded on an
elemental Vario EL spectrometer. The intrinsic viscosity
was measured in decalin. At 135 ꢁC using an Ubbleohed
viscometer, and the average of molecular weight was cal-
culated by following equation [54]:
TiCl4 (2.2 mL, 20 mmol) in 20 mL of toluene was added
dropwise to a solution of aniline (7.3 mL, 80 mmol) in
50 mL of toluene. The resulting mixture was stirred at
90 ꢁC for 30 min followed by the addition of 1,1,1-5,5,5-
hexafluoroacetylacetone (4.16 g, 20 mmol). The reaction
mixture was stirred overnight, poured into dilute Na2CO3
solution, and extracted with methylene chloride. The
organic phase was dried over Na2SO4 and evaporated in
vacuo. The residue was dissolved in ether and treated with
concentrated hydrochloride at 0 ꢁC. Subsequently, the
white precipitate was removed by filtration. The filtrate
was washed with dilute Na2CO3 solution, dried over anhy-
drous Na2SO4, and evaporated. The crude product was
purified by column chromatography on silica gel with
petroleum as the eluent, affording the imine compound
(Ph)NC(CF3)CHC(CF3)NH(Ph) (4.65 g, 13.0 mmol) as a
yellow solid in 65% yield. The other ligands 2c–d were pre-
pared via the same procedure.
½gꢁ ¼ 4:6 ꢂ 10ꢀ4M0g:73
.
4.2.4. Compound 2b
1
Yield: 65%. H NMR (300 MHz, CDCl3): d 11.98 (s,
1-Benzoylacetone, 1,1,1-5,5,5-hexafluoroacetylacetone
and 4,4,4-trifluoro-1-phenyl- 1,3-butanedione were pur-
chased from Aldrich. Diethyl ether, hexane and toluene
were refluxed and distilled from sodium benzophenone
ketyl under nitrogen. Dichloromethane was dried over
CaH2 and distilled before use. Titanium tetrachloride was
distilled prior to use. The n-butyllithium solution in hexane
was purchased from Aldrich. Modified methylaluminoxane
(MMAO, 7% aluminum in heptane solution) was pur-
chased from Akzo Nobel Chemical Inc.
1H, NH), 7.54–6.84 (m, 10H, PhH), 5.81(s, 1H, @CH).
13C NMR (300 MHz, CDCl3): d 148.25 (q, JCCF = 118.8),
141.64, 127.76, 124.72, 122.01, 119.96 (q, JCF = 1127.1),
87.73 (q, JCCCF = 18.3). 19F NMR (C6D6, 300 MHz): d
50.86 (CF3). Anal. Calc. for C17H12F6N2: C, 56.99; H,
3.38; N, 7.82. Found: C, 66.90; H, 3.25; N, 7.70%.
4.2.5. (Ph)NC(CH3)CHC(Ph)NH(Ph) (2c)
1
Yield: 61%. H NMR (300 MHz, CDCl3): d 12.52 (s,
1H, NH), 7.84–6.57 (m, 15H, PhH), 5.09 (s, 1H, @CH),
2.13 (s, 3H, CH3). 13C NMR (300 MHz, CDCl3): d
164.32, 153.63, 148.36, 141.29, 136.37, 127.72, 127.52,
127.35, 127.22, 127.19, 122.02, 121.06, 120.89, 120,47,
100.45, 20.39. Anal. Calc. for C22H20N2: C, 84.58; H,
6.45; N, 8.97. Found: C, 84.68; H, 6.39; N, 8.88%.
4.2. Synthesis of ligands 2a–d
4.2.1. (Ph)NC(CH3)CHC(CH3)NH(Ph) (2a) [30]
To a mixture of acetylacetone (10.25 mL, 100 mmol)
and aniline (18 mL, 200 mmol) in the 100 mL flask in an
ice bath was added concentrated hydrochloride (8.3 mL)
slowly with acute stirring and yellow brown solution was
formed. After stirring for 12 h, plentiful precipitates were
observed. The reaction mixture was filtered and washed
with petroleum ether. The solid was dissolved by addition
of 8 mL CH2Cl2, 50 mL H2O and 20 mL triethylamine.
The aqueous phase was extracted with ether and combined
with organic phase, then dried over Mg2SO4 and evapo-
rated in vacuo. The crude product was recrystallized from
ethanol as yellow crystals in 92% yield.
4.2.6. (Ph)NC(CF3)CHC(Ph)NH(Ph) (2d)
1
Yield: 68%. H NMR (300 MHz, CDCl3): d 13.04 (s,
1H, NH), 7.35–6.76 (m, 15H, PhH), 5.40 (s, 1H, @CH).
13C NMR (300 MHz, CDCl3): d 157.24, 151.03 (q,
JCCF = 108.0), 147.14, 139.45, 135.19, 128.32, 127.81,
127.44, 127.07, 122.78, 121.81, 119.70 (q, JCF = 1149.3),
119.42, 92.34 (q, JCCCF = 15.6). 19F NMR (C6D6,
300 MHz): d 50.27 (CF3). Anal. Calc. for C22H17F3N2: C,
72.12; H, 4.68; N, 7.65. Found: C, 72.39; H, 4.43; N, 7.68%.
4.3. Synthesis of titanium complexes 4a–4d
4.2.2. Compound 2a
1
Yield: 92%. H NMR (300 MHz, CDCl3): d 12.61 (s,
4.3.1. [(Ph)NC(CH3)CHC(CH3)N(Ph)]2TiCl2 (4a)
To a stirred solution of compound 2a (1 g, 4 mmol) in
dried diethyl ether (20 mL) at ꢀ78 ꢁC was added a 1.6 M
n-butyllithium hexane solution (2.5 mL, 4 mmol) dropwise
1H, NH), 7.48–6.63 (m, 10H, PhH), 4.81(s, 1H, @CH),
1.94 (s, 6H, CH3). 13C NMR (300 MHz, CDCl3): d
159.97, 146.35, 129.42, 123.81, 123.15, 98.11, 21.43. Anal.

L.-M. Tang et al. / Journal of Organometallic Chemistry 691 (2006) 2023–2030
2029
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 (0.22 mL, 2 mmol) in dried diethyl
ether (20 mL) at ꢀ78 ꢁC with stirring over 30 min. The
mixture was allowed to warm to room temperature and
stirred for 20 h. The evaporation of the solvent in vacuum
yielded a crude product. To the crude product was added
dried CH2Cl2 (20 mL), the mixture was stirred for 10 min
and then filtered. The filtrate was concentrated in vacuo
and layered with dried n-hexane to gave complex 4a as a
brown solid in 58% yield. The other complexes 4b–d were
prepared by the same procedure with similar yields.
tyl alcohol (10 mL) was added to terminate the polymeriza-
tion reaction, and the ethylene gas feed was stopped. The
resulted mixture was added to acidic methanol. The solid
polyethylene was isolated by filtration, washed with meth-
anol, and dried at 60 ꢁC for 24 h in a vacuum oven.
4.5. Ethylene polymerization under pressured conditions
Pressured polymerization was carried out at 25 ꢁC under
15 atm ethylene pressure in a 100 mL stainless steel reactor
equipped with a propeller-like stirrer. Toluene (50 mL) and
a heptane solution of MMAO were introduced into the
reactor under ethylene at atmospheric pressure. Ethylene
was pumped into the reactor up to 15 atm pressure with
stirring vigorously (600 rpm) at 25 ꢁC. Polymerization
was initiated by the addition of a toluene solution of the
complexes 4a or 4c into the reactor with vigorous stirring
(900 rpm). After a prescribed time, methanol (5 mL) was
added to terminate the polymerization reaction. The reac-
tor was vented and the resulted mixture was added to
acidic methanol. The solid polyethylene was isolated by fil-
tration, washed with methanol, and dried at 60 ꢁC for 24 h
in a vacuum oven.
4.3.2. Complex 4a
1H NMR (300 MHz, CDCl3): d 7.33–7.29 (d, 2H, PhH),
7.16–7.14 (m, 2H, PhH), 7.12(d, 4H, PhH), 6.98–6.94 (d,
2H, PhH), 5.02 (s, 1H, @CH), 2.42 (s, 6H, CH3). Anal.
Calc. for C34H34Cl2N4Ti: C, 66.08; H, 5.51; N, 9.07.
Found: C, 65.91; H, 5.7; N, 9.00%.
4.3.3. [(Ph)NC(CF3)CHC(CF3)NH(Ph)]2TiCl2 (4b)
1
Yield: 61%. H NMR (300 MHz, CDCl3): d 7.30–7.24
(m, 4H, PhH), 7.15 (t, 2H, PhH), 7.10–6.96 (d, 4H,
PhH), 5.81 (s, 1H, @CH). 19F NMR (C6D6, 300 MHz): d
50.27 (CF3, major C2 isomer), 51.46 (CF3, minor C1 iso-
mer), 49.23 (CF3, minor C1 isomer).Anal. Calc. for
C34H22Cl2F12N4Ti: C, 48.98; H, 2.64; N, 6.72. Found: C,
49.56; H, 2.32; N, 6.58%.
4.6. Crystallographic studies
The X-ray crystallographic analyses were performed
using crystals 4a and 4c with the size 0.71 · 0.18 · 0.14
and 0.52 · 0.46 · 0.44 mm, obtained by recrystallization
from dichloromethane/hexane solution at room tempera-
ture. The intensity data were collected with the x scan
mode (293 K) on a Bruker Smart APEX diffractometer
with CCD detector using Mo Ka radiation (k =
4.3.4. [(Ph)NC(CH3)CHC(Ph)NH(Ph)]2TiCl2 (4c)
Yield: 59%. 1H NMR (300 MHz, CDCl3): d 7.46 (d, 2H,
PhH), 7.28–7.26 (m, 6H, PhH), 7.23 (m, 1H, PhH), 7.12 (d,
2H, PhH), 6.96–6.83 (m, 4H, PhH), 5.23 (s, 1H, @CH),
2.63 (s, 3H, CH3). Anal. Calc. for C46H42Cl6N4Ti: C,
60.56; H, 4.61; N, 6.14. Found: C, 61.03; H, 4.72; N, 5.99%.
˚
0.71073 A). Lorentz polarization factors were made for
the intensity data and absorption corrections were per-
formed using SADABS program [55]. The crystal structures
were solved using the SHELXTL program and refined using
full-matrix least-squares [56]. The positions of hydrogen
atoms were calculated theoretically and included in the
final cycles of refinement in a riding model along with
attached carbons.
4.3.5. [(Ph)NC(CF3)CHC(Ph)NH(Ph)]2TiCl2 (4d)
1
Yield: 63%. H NMR (300 MHz, CDCl3): d 7.40–7.31
(m, 10H, PhH), 7.20–7.09 (m, 10H, PhH), 6.99–6.97 (m,
6H, PhH), 6.75–6.72 (m, 4H, PhH), 5.53(s, 2H, @CH).
19F NMR (C6D6, 300 MHz): d 50.84 (CF3, major C2 iso-
mer), 51.69 (CF3, minor C1 isomer). Anal. Calc. for
C44H32Cl2F6N4Ti: C, 62.21; H, 3.80; N, 6.60. Found: C,
62.06, H, 3.94; N, 3.50%.
5. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic Data
Center, CCDC Nos. 278834 and 278835 and for the com-
plexes 4a and 4c. Copies of this information may be
obtained free of charge from The Director, CCDC, 12
Union Road, Cambridge CB2 1EZ, UK (fax: +44 1223
336 033; e-mail: deposit@ccdc.cam.ac.uk or www: http://
ccdc.cam.ac.uk).
4.4. Ethylene polymerization under atmospheric pressure
Ethylene polymerization under atmospheric pressure
was carried out in toluene in a 150 mL glass reactor
equipped with a mechanical stirrer. Toluene (50 mL) was
introduced into the nitrogen-purged reactor and stirred
vigorously (600 rpm). The toluene was kept at a prescribed
polymerization temperature, and then ethylene gas feed
was started. After 15 min, the polymerization was initiated
by the addition of a heptane solution of MMAO and a tol-
uene solution of complexes 4b or 4d into the reactor with
vigorous stirring (900 rpm). After a prescribed time, isobu-
Acknowledgements
The authors are grateful for the financial support by the
National Natural Science Foundation of China (Nos.

2030
L.-M. Tang et al. / Journal of Organometallic Chemistry 691 (2006) 2023–2030
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20334030 and 50525312), and by the Special Funds for Ma-
jor State Basis Research Projects (No. 2005CB623800)
from the Ministry of Science and Technology of China.
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