A series of new zirconium complexes bearing bis(phenoxyketimine) ligands: Synthesis, characterization and ethylene polymerization

Article abstract of DOI:10.1016/j.jorganchem.2005.06.029

A series of new zirconium complexes bearing bis(phenoxyketimine) ligands, bis((3,5-di-tert-butyl-C₆H₂-2-O)R₁CN (2-R ₂-C₆H₄))ZrCl₂ {R₁ = Me, R₂ = H (2a); R₁ = Et, R₂ = H (2b); R ₁ = Ph, R₂ = H (2c); R₁ = 2-Me-Ph, R ₂ = H (2d); R₁ = 2-F-Ph, R₂ = H (2e); R ₁ = 2-Cl-Ph, R₂ = H (2f); R₁ = 2-Br-Ph, R ₂ = H (2g); R₁ = Ph, R₂ = Me (2h); R ₁ = Ph, R₂ = F (2i)}, have been prepared, characterized and tested as catalyst precursors for ethylene polymerization. Crystal structure analysis reveals that complex 2c has a six coordinate center in a distorted octahedral geometry with trans-O, cis-N, cis-Cl arrangement which possesses approximate C₂ symmetry. When activated with methylaluminoxane (MAO), complexes 2a-2i exhibited high ethylene polymerization activities of 10 ⁶-10⁸ g PE (mol M h)^-1. Compared with the bis(phenoxyimine) zirconium analogues bis((3,5-di-tert-butyl-C₆H ₂-2-O)CHNC₆H₅)ZrCl₂ (3), the introduction of substituent on the carbon atom of the imine double bond enhanced the catalytic activity and molecular weight of prepared polyethylene. Especially, when the H atom at the carbon atom of the imine double bond was replaced by 2-fluoro-phenyl with strong electronic-withdrawing property, complex 2e displayed the highest catalytic activity, and the polyethylene obtained possessed the highest molecular weight and melt point.

Full text of DOI:10.1016/j.jorganchem.2005.06.029

Journal of Organometallic Chemistry 690 (2005) 4184–4191
www.elsevier.com/locate/jorganchem
A series of new zirconium complexes bearing
bis(phenoxyketimine) ligands: Synthesis, characterization
and ethylene polymerization
a
a,
*
Shangtao Chen a,b, Xiaofan Zhang a,b, Hongwei Ma , Yingying Lu
,
Zhicheng Zhang a,b, Huayi Li a,b, Zhanxia Lu a,b, Nannan Cui a,b, Youliang Hu
a
a
Joint Laboratory of Polymer Science and Materials, Key Laboratory of Engineering Plastics, Institute of Chemistry,
the Chinese Academy of Sciences, Beijing 100080, China
b
Graduate School of the Chinese Academy of Sciences, Beijing 100039, China
Received 7 December 2004; received in revised form 23 June 2005; accepted 24 June 2005
Available online 2 August 2005
Abstract
A series of new zirconium complexes bearing bis(phenoxyketimine) ligands, bis((3,5-di-tert-butyl-C6H2-2-O)R1C@N (2-R2-
C6H4))ZrCl2 {R1 = Me, R2 = H (2a); R1 = Et, R2 = H (2b); R1 = Ph, R2 = H (2c); R1 = 2-Me-Ph, R2 = H (2d); R1 = 2-F-Ph,
R2 = H (2e); R1 = 2-Cl-Ph, R2 = H (2f); R1 = 2-Br-Ph, R2 = H (2g); R1 = Ph, R2 = Me (2h); R1 = Ph, R2 = F (2i)}, have been pre-
pared, characterized and tested as catalyst precursors for ethylene polymerization. Crystal structure analysis reveals that complex 2c
has a six coordinate center in a distorted octahedral geometry with trans-O, cis-N, cis-Cl arrangement which possesses approximate
C2 symmetry. When activated with methylaluminoxane (MAO), complexes 2a–2i exhibited high ethylene polymerization activities
of 106–108 g PE (mol M h)À1. Compared with the bis(phenoxyimine) zirconium analogues bis((3,5-di-tert-butyl-C6H2-2-
O)CH@NC6H5)ZrCl2 (3), the introduction of substituent on the carbon atom of the imine double bond enhanced the catalytic activ-
ity and molecular weight of prepared polyethylene. Especially, when the H atom at the carbon atom of the imine double bond was
replaced by 2-fluoro-phenyl with strong electronic-withdrawing property, complex 2e displayed the highest catalytic activity, and the
polyethylene obtained possessed the highest molecular weight and melt point.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Phenoxyketimine; Zirconium; Ethylene; Polymerization
1. Introduction
ligand design and modification played a key role for
optimizing polymerization activity as well as polymer
microstructure [2]. Advances in the understanding of
homogeneous polymerization mechanism have resulted
in the design and development of highly active single
component non-metallocene [3].
Recently, much attention has been focused on the
early and late transition metal non-metallocene com-
plexes incorporating [N,O] based multidentate ligands
[4]. Grubbs and co-workers [4a,4b] discovered Ni metal
complexes bearing phenoxyimine moieties which exhib-
ited high activity for ethylene copolymerization with
Olefin polymerization by well-defined single-site tran-
sition metal catalysts has attracted considerable atten-
tion in the fields of organometallic chemistry and
polymer chemistry both for academic and industrial
interests [1]. During the past two decades for develop-
ment of new homogeneous transition metal complex,
*
Corresponding author. Tel.: +86 10 6256 2697; fax: +86 10 6255
4061.
E-mail address: yylu@iccas.ac.cn (Y. Lu).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.06.029

S. Chen et al. / Journal of Organometallic Chemistry 690 (2005) 4184–4191
4185
polar monomer to produce functional polyolefin. Al-
most at the same time, scientists at Mitsui Chemicals
developed a series of group IV transition metal com-
plexes bearing bis(phenoxyimine) ligands for a-olefin
polymerization [5,6]. The independent work of them
and other groups [7] indicated that these complexes were
very active catalysts for olefin polymerization and copo-
lymerization. The catalytic activity of these catalysts was
highly dependent on the property of the substituents in
the ortho-position of the phenoxy ring and on the nitro-
gen atom of the imine double bond. The great variety of
these complexes conveniently obtained by changing the
substituents of the phenol and aniline moieties of the
phenoxyimine ligand allows significant modifications
in the steric and electronic features of catalyst. We ex-
pected that the substituent on the carbon atom of the
imine double bond also affects the catalytic performance
of the phenoxy-based complexes. To the best of our
knowledge, there have been very few examples focused
on the effect of substituents at the carbon atom of the
imine double bond on the catalytic activity. Coates
and co-workers [8] found that titanium complexes bear-
ing bis(phenoxyketimine) ligands without fluorine-
containing substituent in the aniline moiety were active
for living ethylene polymerization. Kettunen et al. [9]
prepared nickel metal complex supported by phenoxyk-
etimine ligand, but no result of these complexes for ole-
fin polymerization was reported. In this paper, nine new
zirconium complexes bearing bis(phenoxyketimine) li-
gands, where there are alkyl or aryl groups (R1) on the
carbon atom of the imine double bond, have been syn-
thesized and used for ethylene polymerization. The ste-
ric bulk and electronic effects caused by substituents
on the carbon atom of the imine double bond (R1) on
catalytic activities of ethylene polymerization were
investigated. The preliminary work showed that all these
new zirconium complexes were highly active catalysts
for ethylene polymerization.
2. Results and discussion
2.1. Synthesis and characterization of ligands and
corresponding zirconium complexes
The synthesis of phenoxyketimine ligand and corre-
sponding zirconium complexes was summarized in
Scheme 1. The ligands 1d–1i were prepared in a similar
way as published in [8]. Amides used for the ligand syn-
thesis were prepared by treating equimolar amounts of
acid chloride, aniline, and triethylamine in methylene
chloride at 0 ꢁC and recrystallized before use. The de-
sired ligand was prepared through Friedel-Crafts reac-
tion of imidoyl chlorides generated in situ by the
reaction of amides and PCl5 with 2,4-di-tert-butylphenol
in moderate to good yield. This method was more effi-
cient for the introduction of aryl or electron-withdraw-
ing containing group onto the carbon atom of the
imine double bond compared with the condensation
method between 2-hydroxyl-phenone and aniline
tBu
R2
H2N
R2
OH
R1
O
R1
Cl
N
R1
O
tBu
PCl5
NH
R2
N
OH
tBu
R1
AlCl3
Cl
Et3N
tBu
R2
1d-1i
R2
R2
ZrCl2
1) nBuLi
R1
N
R1
N
OH
tBu
2) 0.5 ZrCl4
O
2
tBu
tBu
tBu
1a-1i
c
2a-2i
a
b
d
e
f
g
h
i
3
R1
R2
Me Et Ph 2-Me-Ph 2-F-Ph
2-Cl-Ph 2-Br-Ph Ph Ph
Me
H
H
H
H
H
H
H
H
F
H
Scheme 1. Synthesis of phenoxyketimine ligands and corresponding zirconium complexes.

4186
S. Chen et al. / Journal of Organometallic Chemistry 690 (2005) 4184–4191
Fig. 1. Thermal ellipsoid drawing of complex 2c. Hydrogen atoms are omitted for clarity.
reported in the literature [9]. Treatment of lithium salt of
the ligand with 0.5 equivalent ZrCl4 in ether gave the
bis(phenoxyketimine) zirconium complex in moderate
yield. Ligands 1d–1i have been well characterized by
1H NMR, 13C NMR, mass spectrometry and elemental
analysis. The formation of the corresponding metal
complexes was supported very well by 1H NMR and ele-
mental analysis. 1H NMR studies showed that these
complexes existed as isomeric mixtures in solution,
which has already been observed by Coates and co-
workers [8] for bis(phenoxyketimine) titanium
complexes and by Fujita and co-workers [10] for
bis(phenoxyimine) group IV complexes. The crystal
structure of 2c has been further studied by X-ray diffrac-
tion analysis. Thermal ellipsoid diagram of complex 2c
was presented in Fig. 1. The data collection and struc-
ture refinement of the analysis were listed in Table 1.
The crystallography study revealed that molecule 2c in
solid state has a six coordinate center in a distorted octa-
hedral geometry with trans-O, cis-N, cis-Cl arrangement
which possesses approximate C2 symmetry. The config-
uration of 2c closely resembles its bis(phenoxyketimine)
titanium [8] and bis(phenoxyimine) zirconium [11] ana-
logues. For complex 2c, the phenyl ring of the aniline
moiety (Ph3) and the phenyl (Ph2) on carbon atom of
the imine double bond orient themselves nearly perpen-
dicular to the phenol plane (Ph1) with dihedral angle as
74.8ꢁ and 78.2ꢁ respectively, while the two phenyl rings
Ph3 and Ph2 tilt to each other at an angle of 56.4ꢁ.
The Zr1–O1–Ph1–C15–N1 combination of 2c is almost
coplanar with an average deviation from the mean plane
cis-location site of the chlorine atoms around the metal
center in the complex indicated its potential as catalyst
precursor for olefin polymerization [12].
Table 1
Crystal data and structure refinement of complex 2c
Empirical formula
Fw
C54H60Cl2N2O2Zr
931.16
Temperature (K)
Crystal size (mm)
Cryst system
Space group
293(2)
0.722 · 0.672 · 0.591
Orthorhombic
P212121
˚
a (A)
16.235(3)
17.165(3)
18.097(4)
˚
b (A)
˚
c (A)
a(ꢁ)
90
90
90
b (ꢁ)
c (ꢁ)
3
˚
V (A )
5043.2(17)
4, 1.226
0.364
Z, calculated density(Mg/m3)
Absorption coefficient (mmÀ1
)
h Range for data collection (ꢁ)
1.73–27.48
Limiting indices
À18 6 h 6 21,
À20 6 k 6 22, À23 6 l 6 23
43268/6239
98.1%
Reflections collected/unique
Completeness to h maximum
Absorption correction
Empirical
Refinement method
Full-matrix least-squares
on F2
Number of data/restraints/parameters
Goodness-of-fit on F2
6239/0/551
1.008
Final R indices [I > 2r(I)]
R indices (all data)
R1 = 0.0311, wR2 = 0.0765
R1 = 0.0372, wR2 = 0.0859
0.381 and À0.401
LargesÀt 3difference peak and hole
˚
(e A
)
˚
of 0.09 A. The Cl–Zr–Cl angle is 99.14ꢁ (Table 2). The

S. Chen et al. / Journal of Organometallic Chemistry 690 (2005) 4184–4191
4187
Table 2
the catalytic activity of ethylene polymerization and
the molecular weight of products as shown in Table 3.
When the methyl substituent was introduced, complex
2a gave higher molecular weight polyethylene (Mw
89,000) with greatly increased catalytic activity of
12.9 kg PE (mmol Zr h)À1. The introduction of ethyl
group led to further increased catalytic activity of
41.1 kg PE (mmol Zr h)À1. For steric consideration of
the substituents H (3) < Me (2a) < Et (2b) of R1, the cat-
alytic activity followed the order 3 < 2a < 2b, while the
molecular weight of PE followed 3 < 2b < 2a. There
was no direct relationship between the catalytic perfor-
mance and the steric bulk of the R1 substituent. This
might be due to the complicated electronic structures be-
tween the complexes resulting from the introduction of
R1 substituent.
˚
Selected bond distances (A) and angles (ꢁ) for complex 2c
˚
Bond distances (A)
Zr(1)–O(2)
Zr(1)–O(1)
Zr(1)–N(1)
Zr(1)–N(2)
Zr(1)–Cl(2)
Zr(1)–Cl(1)
O(1)–C(1)
O(2)–C(28)
N(1)–C(15)
N(1)–C(22)
N(2)–C(42)
N(2)–C(49)
1.973(2)
1.973(2)
2.349(2)
2.381(3)
2.422(1)
2.427(1)
1.333(3)
1.328(3)
1.305(4)
1.457(3)
1.306(4)
1.454(4)
Bond angles (ꢁ)
O(2)–Zr(1)–O(1)
O(2)–Zr(1)–N(1)
O(1)–Zr(1)–N(1)
O(2)–Zr(1)–N(2)
O(1)–Zr(1)–N(2)
N(1)–Zr(1)–N(2)
O(2)–Zr(1)–Cl(2)
O(1)–Zr(1)–Cl(2)
N(1)–Zr(1)–Cl(2)
N(2)–Zr(1)–Cl(2)
O(2)–Zr(1)–Cl(1)
O(1)–Zr(1)–Cl(1)
N(1)–Zr(1)–Cl(1)
N(2)–Zr(1)–Cl(1)
Cl(2)–Zr(1)–Cl(1)
164.38(9)
92.74(8)
75.53(8)
75.32(8)
92.21(9)
79.66(8)
95.31(7)
94.40(6)
166.30(6)
91.68(6)
94.79(6)
95.72(7)
91.19(7)
166.03(6)
99.14(4)
From the ethylene polymerization result listed in Ta-
ble 3, the substituent in the ortho-position of the phenyl
group of R1 exhibited significant effect on catalytic
activity. Compared with 2c, the introduction of methyl
in the ortho-position of R1 (2d) resulted in dramatic de-
crease of catalytic activity to 3.4 kg (mmol Zr h)À1
,
while the introduction of fluorine group (2e) led to a sig-
nificant increase of catalytic activity to 216.3 kg (mmol
Zr h)À1. This enhancement in activity might be due to
the increased positive charge of the metal center caused
by the electron-withdrawing effect of the fluorine con-
taining substituent which favored the coordination of
ethylene monomer with the metal center. As the de-
crease of the electron-withdrawing effect of groups from
F, Cl to Br, the catalytic activity and molecular weight
of polyethylene obtained decreased accordingly. The ste-
ric and electronic effects could be combined together to
account for this. These results indicated that the intro-
duction of electronic withdrawing group led to the in-
crease of catalytic activity for ethylene polymerization.
The effect of the substituent in the ortho-position of
the aniline moiety on catalytic activity has also been
investigated. On the one hand, the introduction of alkyl
group in the ortho-position of the aniline moiety resulted
2.2. Polymerization of ethylene by complexes 2a–2i
The catalytic properties of complexes 2a–2i for ethyl-
ene polymerization were evaluated using MAO as cocat-
alyst. The polymerization was performed in toluene at
atmospheric pressure and the results were listed in Table
3. Bis(phenoxyimine) zirconium complex 3, bearing a
hydrogen at the R1 position yielded polyethylene with
an Mw of 12,000 and an activity of 1.6 kg PE (mmol
Zr h)À1 at 20 ꢁC. Compared with bis(phenoxyimine)
complex 3, the introduction of substituent into the car-
bon atom of the imine double bond greatly enhanced
Table 3
Ethylene polymerization results by complexes 2a–2i in toluene activated with MAOa
Activity (kg (mmol Zr h)À1
)
Tm (ꢁC)
DHf (J/g)
Mw
Mw/Mn
b
b
Run
Complex
Yield (g)
1
2
3
4
5
6
7
8
9
3/0.2 lmol
0.053
0.431
1.373
0.670
0.112
0.721
1.320
0.407
0.057
1.129
1.6
12.9
41.2
20.1
3.4
216.3
39.6
12.2
1.7
127
134
133
133
134
135
132
134
132
133
220.8
207.6
194.0
200.9
226.4
170.4
181.4
191.9
213.1
200.6
12000
89000
40000
31000
41000
165000
53000
32000
104000
71000
1.43
1.97
2.07
1.72
1.92
2.43
1.94
2.03
3.84
2.76
2a/0.2 lmol
2b/0.2 lmol
2c/0.2 lmol
2d/0.2 lmol
2e/0.02 lmolc
2f/0.2 lmol
2g/0.2 lmol
2h/0.2 lmol
2i/0.2 lmol
10
a
33.9
Conditions: 20 ꢁC, Vtotal = 100 mL, Al/Zr = 6000, 0.1 MPa ethylene pressure, polymerization time: 10 min.
Determined by GPC relative to polystyrene standard.
2.12 g polyethylene was produced for 2 min when 0.2 lmol complex was used. In order to eliminate the problem of mass transfer, the amount of
b
c
complex 2e was changed to 0.02 lmol.

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S. Chen et al. / Journal of Organometallic Chemistry 690 (2005) 4184–4191
Table 4
ligands have been synthesized and characterized as de-
signed. The catalytic activities of these compounds for
ethylene polymerization at atmospheric pressure have
been investigated using MAO as the cocatalyst. All
complexes showed high catalytic activities for ethylene
polymerization especially at 20 ꢁC. The introduction of
substituent into the R1 position of the phenoxy-based
ligand enhanced the catalytic activity of the complex
and the molecular weight of polyethylene produced.
The attachment of electron-withdrawing containing
group onto the carbon atom of the imine double bond
led to significant increase in catalytic activity of the
complexes and molecular weight of prepared polyethyl-
ene. Especially, the introduction of 2-fluoro-phenyl
group into the R1 position gave the highest catalyst
activity for ethylene polymerization and the highest
molecular weight and melting point of the obtained
polymers.
Ethylene polymerization results by complexes 2b, 2c and 2e at different
temperaturea
Run
Complex
Yield (g)
Tp (ꢁC)
Activity
(kg (mmol Zr h)À1
)
1
2
3
4
5
6
7
8
9
2b/0.2 lmol
2b/0.2 lmol
2b/0.2 lmol
2b/0.2 lmol
2c/0.2 lmol
2c/0.2 lmol
2c/0.2 lmol
2c/0.2 lmol
2e/0.02 lmol
2e/0.02 lmol
2e/0.02 lmol
2e/0.02 lmol
2e/0.02 lmol
1.052
1.373
0.310
0.021
0.418
0.670
0.174
0.012
0.366
0.721
0.234
0.038
0.010
0
20
40
60
0
20
40
60
0
20
40
60
80
31.6
41.2
9.3
0.6
12.5
20.1
5.2
0.36
109.8
216.3
70.2
11.4
3.0
10
11
12
13
a
Conditions: toluene (Vtotal = 100 mL), 10 min, Al/Zr = 6000,
0.1 MPa ethylene pressure.
in the significant decrease of the catalytic activity. On
the other hand, if the hydrogen atom at the R2 position
was replaced with a fluorine atom, the catalytic activity
was increased to 33.9 kg PE (mmol Zr h)À1. The cata-
lytic increase might be attributed to the stability of metal
center favored by the introduction of substituent with
strong electronic-withdrawing property.
It is interesting to compare the polymerization results
of complex 2e and 2i, whose substituents on carbon
atom and nitrogen atom of the imine double bond were
exchanged between phenyl and 2-fluoro-phenyl. When
2-fluoro-phenyl was on the N atom and phenyl was on
the C atom, complex 2i exhibited an activity as high as
33.9 kg PE (mmol Zr h)À1 and the Mw of product was
71,000. When the two groups were exchanged, complex
2e possessed six times higher catalytic activity and two
times higher Mw of polyethylene than 2i. This result
might suggest that the attachment of electron-withdraw-
ing group in the carbon atom of the imine double re-
sulted in more significant enhancement on the catalytic
properties than that in the nitrogen atom for these
bis(phenoxyketimine) zirconium complexes.
The polymerization of complex 2b, 2c and 2e for ethyl-
ene polymerization has been studied at different tempera-
tures. The results were collected in Table 4. All three
catalysts showed the highest catalytic activity at about
20 ꢁC. Then activity decreased rapidly as the temperature
increased which may be due to the decomposition of the
complexes at high temperature. More detailed work of
these bis(phenoxyketimine) zirconium complexes for ole-
fin polymerization is still under investigation.
4. Experimental
All manipulations of air- and/or moisture sensitive
compounds were carried out using drybox procedures
or standard Schlenk techniques. H NMR (300 MHz)
1
and 13C NMR (75 MHz) spectra were performed on a
Bruker DMX-300 spectrometer. Mass spectra were
carried out with an electron impact (EI) instrument
(Kratos AEI MS-50). Elemental analyses were obtained
using Carlo Erba 1106 and ST02 apparatus. Molecular
weights (Mw and Mn) and polydispersities (Mw/Mn)
were determined by high temperature gel-permeation
chromatography (GPC) on a PL-GPC220 instrument
at 140 ꢁC in trichlorobenzene and the data were
analyzed relative to polystyrene standards. Melting
temperatures (Tm) of polyethylene were measured by a
Perkin–Elmer differential scanning calorimetry (DSC)
operating at a heating rate of 10 ꢁC/min and determined
in the second scan.
Ethylene for polymerization was obtained from
Yanshan Petro-chemical Company SINOPEC China.
Methylaluminoxane (MAO) solution (1.4 M) in toluene
was purchased from Albemarle. nBuLi (1.6 M) in hexane
was purchased from Acros. Ligand 1a–1c [8] and com-
plex 3 [13] were prepared according to published proce-
dures. Amides for the ligand syntheses were prepared by
treating equimolar amounts of acid chloride, aniline,
and triethylamine in methylene chloride at 0 ꢁC. The
amides were recrystallized from hot toluene and dried
before use. All other chemicals were commercially
available and used as received. Toluene, tetrahydrofu-
ran, hexane, and ether were refluxed over sodium-benzo-
phenone and degassed under argon. Methylene chloride
was vigorous degassed to remove oxygen and then
distilled from P2O5. All glasswares were flame dried
before use.
3. Conclusion
In summary, nine new bis(phenoxyketimine) zirco-
nium complexes 2a–2i bearing bis(phenoxyketimine)

S. Chen et al. / Journal of Organometallic Chemistry 690 (2005) 4184–4191
4189
4.1. Synthesis of ligands 1d–1i
d, J = 7.8 Hz), 7.26–7.08 (5H, m), 6.96 (1H, t,
J = 7.5 Hz), 6.86 (2H, d, J = 7.7 Hz), 6.75 (1H, s), 1.51
(9H, s, C(CH3)3), 1.14 (9H, s, C(CH3)3); 13C NMR
(CDCl3, 75 MHz): d 169.9, 158.1, 145.6, 137.8, 135.8,
133.0, 130.9, 128.7, 127.9, 127.0, 126.8, 125.1, 124.4,
123.2, 120.2, 116.5, 33.9, 32.7, 29.9, 28.2; MS (EI): 419
(58, M+), 404 (100, M+ À 15), 376 (22, M+ À 43); Anal.
Calc. for C27H30ClNO: C, 77.21; H, 7.20; N, 3.34. Found:
C, 77.15; H, 7.16; N, 3.36%.
Ligands 1d–1i were prepared in a way similar to
established procedure [8]. The synthetic route is depicted
in Scheme 1. Typically, amide (1 equiv.) and PCl5
(1 equiv.) were combined in a Schlenk flask under argon,
dry methylene chloride was slowly added at 0 ꢁC. The
cold bath was removed, the solution was stirred for
5 h at room temperature. After removing the solvent
under vacuum, the solid residue was dissolved in
methylene chloride and filtered through a celite pad.
The resulting clear solution was transferred via cannula
to a Schlenk flask filled with a slurry of AlCl3
(1.2 equiv.) in methylene chloride at 0 ꢁC. The solution
was stirred for 10 min before 10 mL methylene chloride
solution of 2,4-di-tert-butylphenol (0.95 equiv.) was
added. The reaction mixture was stirred at room
temperature for 24 h. Pouring the resulting solution to
ice water, the organic layer was separated and then
washed with water, 1.0 M Na2CO3 and brine, and dried
over Na2SO4. After filtration and solvent removal, the
residual yellow or orange solid was chromatographed
on silica (10% ethyl acetate/hexane). The solution
obtained was concentrated and placed at À30 ꢁC over-
night. The ligand was obtained as crystal solid in
moderate to good yield (based on phenol employed).
(3,5-Di-tert-butyl-C6H2-2-OH)(2-Me-C6H4)C@NC6H5
(1d): bright yellow solid, yield (64%), 1H NMR (CDCl3,
(3,5-Di-tert-butyl-C6H2-2-OH)(2-Br-C6H4)C@NC6H5
(1g): orange solid, yield (73%), 1H NMR (CDCl3,
300 MHz):
d 14.73 (1H, s, OH), 7.59 (1H, d,
J = 7.8 Hz), 7.51 (1H, s), 7.27 (1H, t, J = 7.4 Hz), 7.22–
7.12 (4H, m), 7.01 (1H, t, J = 7.3 Hz), 6.95 (2H, d,
J = 7.8 Hz), 6.80 (1H, s), 1.57 (9H, s, C(CH3)3), 1.19
(9H, s, C(CH3)3); 13C NMR(CDCl3, 75 MHz): d 171.5,
159.0, 146.3, 138.6, 136.6, 135.9, 131.9, 129.7, 129.6,
127.8, 127.5, 126.4, 125.5, 124.1, 121.2, 117.2, 34.7, 33.5,
30.7, 29.1; MS (EI): 463 (62, M+ À H), 448 (100,
M+ À H À 15), 420 (25, M+ À H À 43). Anal. Calc. for
C27H30BrNO: C, 69.82; H, 6.51; N, 3.02. Found: C,
69.80; H, 6.49; N, 3.04%.
(3,5-Di-tert-butyl-C6H2-2-OH)PhC@N(2-Me-C6H4)
1
(1h): yellow crystal, yield (62.8%), H NMR (CDCl3,
300 MHz):
d 15.15 (1H, s, OH), 7.52 (1H, d,
4J(H,H) = 2.3 Hz), 7.32 (3H, m), 7.19–7.11 (3H, m),
7.00 (1H, d, 4J(H,H) = 2.3 Hz), 6.92 (2H, m), 6.50
(1H, m), 2.34 (3H, s, CH3), 1.57 (9H, s, C(CH3)3),
1.20 (9H, s, C(CH3)3); 13C NMR(CDCl3, 75 MHz): d
174.1, 160.1, 146.2, 138.8, 137.3, 134.9, 130.0, 129.8,
128.8, 128.4, 128.0, 127.9, 126.8, 125.8, 124.3, 121.7,
118.6, 35.3, 34.2, 31.4, 29.6, 18.6; MS (EI): 399(59,
M+), 384(100, M+ À 15), 356(23, M+ À 43), Anal. Calc.
for C28H33NO: C, 84.17; H, 8.32; N, 3.51. Found: C,
83.98; H, 8.29; N, 3.57%.
300 MHz):
d 14.94 (1H, b, OH), 7.44 (1H, d,
3
4J = 1.2 Hz), 7.23 (1H, t, J = 7.8 Hz), 7.15–7.07 (5H,
3
m), 6.96 (1H, t, J = 7.4 Hz), 6.82–6.78 (3H, m), 2.10
(3H, s) (Ph-CH3), 1.52 (9H, s, C(CH3)3), 1.12 (9H, s,
C(CH3)3); 13C NMR (CDCl3, 75 MHz): d 174.0 (N@C),
159.5 (ArC-OH), 146.4, 138.7, 136.9, 134.8, 134.4,
129.7, 128.5, 128.0, 127.7, 125.8, 124.9, 124.3, 121.9,
118.3, 35.0, 33.8, 31.0, 29.3, 19.7; MS (EI): 399 (53,
M+), 384 (100, M+ À 15), 356 (19, M+ À 43); Anal. Calc.
for C28H33NO: C, 84.17; H, 8.32; N, 3.51. Found: C,
84.10; H, 8.36; N, 3.48%.
(3,5-Di-tert-butyl-C6H2-2-OH)(2-F-C6H4)C@NC6H5
(1e): bright orange solid, yield (71%), 1H NMR (CDCl3,
300 MHz): d 14.70 (1H, s, OH), 7.47 (1H, d, 4J =
2.1 Hz), 7.36 (1H, m), 7.13–6.91 (6H, m), 6.87 (1H, s),
6.80 (2H, d, J = 7.8 Hz), 1.51 (9H, s, C(CH3)3), 1.15
(9H, s, C(CH3)3); 13C NMR (CDCl3, 75 MHz): d
(3,5-Di-tert-butyl-C6H2-2-OH)PhC@N(2-F-C6H4) (1i):
yellow crystal, yield (53%), 1H NMR (CDCl3, 300 MHz):
4
d 14.65 (1H, s, OH), 7.51 (1H, d, J(H,H) = 1.4 Hz),
7.33(3H, m), 7.23 (2H, m), 6.94 (4H, m), 6.77 (1H, m),
1.55 (9H, s, C(CH3)3), 1.18 (9H, s, C(CH3)3); 13C NMR
1
(CDCl3, 75 MHz): d 176.9, 159.9, 153.2 (d, JCF
=
244.5 Hz), 139.0, 137.4, 135.6 (d, 2JCF = 12.1 Hz), 135.1,
128.8, 128.5 (d, JCF = 9.1 Hz), 128.1, 127.8, 127.0
3
4
3
(d, JCF = 4.5 Hz), 125.5 (d, JCF = 7.5 Hz), 123.9,
2
123.7, 118.5, 115.6 (d, JCF = 19.6 Hz), 35.3, 34.1, 31.2,
1
169.0 (N@C), 159.3, 158.0 (d, JCF = 247.5 Hz), 147.0,
139.0, 137.1, 130.8 (d, JCF = 7.5 Hz), 130.0 (d, JCF
29.6; MS (EI): m/z 403 (32, M+), 388 (100, M+ À 15),
360 (13, M+ À 43); Anal. Calc. for C27H30FNO: C,
80.36; H, 7.49. N, 3.47; Found: C, 80.34; H, 7.50; N,
3.51%.
=
7.5 Hz), 128.2 (d, JCF = 15.1 Hz), 125.6, 124.4, 123.6
(d, JCF = 7.5 Hz), 122.7 (d, JCF = 15.1 Hz), 121.3,
118.2, 115.3 (d, JCF = 22.5 Hz), 35.1, 33.9, 31.1, 29.4;
MS (EI): 403 (53, M+), 388 (100, M+ À 15), 360 (26,
M+ À 43); Anal. Calc. for C27H30FNO: C, 80.36; H,
7.49; N, 3.47. Found: C, 80.31; H, 7.52; N, 3.40%.
(3,5-Di-tert-butyl-C6H2-2-OH)(2-Cl-C6H4)C@NC6H5
4.2. Synthesis of the complex 2a–2i
To a stirred solution of phenoxyketimine ligand
(1 equiv.) in dried diethyl ether (5 mL) at À78 ꢁC, nBuLi
(1 equiv.) was added dropwise over 5 min. The solution
was allowed to be warmed up to room temperature and
1
(1f): bright yellow solid, yield(69%), H NMR (CDCl3,
300 MHz): d 14.68 (1H, s, OH), 7.45 (1H, s), 7.34 (1H,

4190
S. Chen et al. / Journal of Organometallic Chemistry 690 (2005) 4184–4191
stirred for 3 h. The resulting solution was added slowly
over a 10 min to a slurry of ZrCl4 (0.5 equiv.) in 10 mL
diethyl ether at À78 ꢁC via cannula. The cold bath was
removed and the reaction mixture was stirred at room
temperature overnight. Evaporation of the solvent in
vacuum yielded a crude product. Methylene chloride
(10 mL) was added to the resulting solid, and the
mixture was stirred for 10 min and centrifugated for
30 min. The above clear solution was transferred. The
organic filtrates were concentrated in vacuum. The
resulting product was washed with hexane (10 mL · 3)
and dried to afford the desired complex in moderate
yield.
Bis((3,5-di-tert-butyl-C6H2-2-O)MeC@NC6H5)ZrCl2
(2a): yellow powder, yield (55%), 1H NMR (CDCl3,
300 MHz): isomers, d 7.60 (d, J = 12.6 Hz), 7.51 (d,
J = 3.9 Hz), 7.47–7.34 (m), 7.23–7.15 (m), 6.96 (d,
J = 7.2 Hz), 6.88 (t, J = 7.2 Hz), 6.79 (t, J = 7.2 Hz),
6.48 (d, J = 7.2 Hz), 6.09 (d, J = 7.2 Hz), 5.97 (d,
J = 7.2 Hz), 2.40, 2.23, 2.15, 2.03 (s), 1.58–1.29 (m),
integral ratio of total aliphatic vs. total aromatic region
is 3.2 (expected: 3.0); Anal. Calc. for C44H56Cl2N2O2Z-
r Æ CH2Cl2: C, 60.59; H, 6.55; N, 3.14. Found: C, 59.82;
H, 6.45; N, 3.21%.
300 MHz): isomers, d 7.62, 7.58, 7.46, 7.38 (m), 7.17–
6.42 (m), 1.61 (s), 1.50 (s), 1.45 (s), 1.42 (s), 1.25 (s),
1.22 (s), 1.20 (s), 1.14 (s), 1.08 (s), 1.06 (s), integral ratio
of total aliphatic vs. total aromatic region is 1.7
(expected: 1.6); Anal. Calc. for C54H58Cl2F2N2O2Z-
r Æ CH2Cl2: C, 62.79; H, 5.75; N, 2.66. Found: C,
62.35; H, 5.76; N, 2.66%.
Bis((3,5-di-tert-butyl-C6H2-2-O)(2-Cl-Ph)C@NC6H5)-
1
ZrCl2 (2f): yellow solid, yield (35%), H NMR (CDCl3,
300 MHz): major C2 isomer only, d 7.45 (2H, d,
J = 1.4 Hz), 7.35 (2H, d, J = 7.9 Hz), 7.29–7.09 (10H,
m), 6.98 (2H, t, J = 7.2 Hz), 6.89 (4H, d, J = 7.5 Hz),
6.74 (2H, d, J = 1.7 Hz), 1.52 (18H, s), 1.14 (18H, s).
Anal. Calc. for C54H58Cl4N2O2Zr: C, 64.85; H, 5.85;
N, 2.80. Found: C, 64.56; H, 5.80; N, 2.75%.
Bis((3,5-di-tert-butyl-C6H2-2-O)(2-Br-Ph)C@NC6H5)-
1
ZrCl2 (2g): yellow solid, yield (44%), H NMR (CDCl3,
300 MHz): isomers, d 7.58 (m), 7.42 (d), 7.32 (m), 7.28
(m), 7.14–5.80 (m), 1.60, 1.59, 1.48, 1.45, 1.35, 1.23,
1.16, 1.10, 1.06, 1.04, 1.00 (s), integral ratio of total
aliphatic vs. total aromatic region is 1.65 (expected:
1.6); Anal. Calc. for C54H58Br2Cl2N2O2Zr: C, 59.56;
H, 5.37; N, 2.57. Found: C, 58.91; H, 5.42; N, 2.52%.
Bis(3,5-di-tert-butyl-C6H2-2-O)PhC@N(2-Me-C6H4)-
ZrCl2 (2h): yellow powder, yield (47%), 1H NMR
(CDCl3, 300 MHz): major C2 isomer only, d 7.53 (2H,
s), 7.32 (6H, m), 7.14 (6H, m), 6.95 (2H, s), 6.90 (4H,
m), 6.54 (2H, m), 2.33 (6H, CH3), 1.56 (18H, s), 1.19
(18H, s). Anal. Calc. for C56H64Cl2N2O2Zr: C, 70.12;
H, 6.72; N, 2.92. Found: C, 69.85; H, 6.64; N, 2.84%.
Bis(3,5-di-tert-butyl-C6H2-2-O)PhC@N(2-F-C6H4)Zr-
Bis((3,5-di-tert-butyl-C6H2-2-O)EtC@NC6H5)ZrCl2
(2b): yellow powder, yield (67%), 1H NMR (CDCl3,
300 MHz): isomers, d 7.60 (s), 7.56–7.46 (m), 7.42 (s),
7.37 (m), 7.23–7.16 (m), 6.92–6.85 (m), 6.77 (t,
J = 7.5 Hz), 6.55 (d, J = 7.8 Hz), 6.24 (d, J = 7.8 Hz),
6.06 (d, J = 7.8 Hz), 3.07 (q), 2.74 (q), 2.62 (q), 2.49
(m), 2.35 (m), 1.55, 1.47, 1.42, 1.36 (s), 1.32 (m), 1.25
(m), 1.15 (t), 1.01 (t), 0.88 (m); integral ratio of total ali-
phatic vs. total aromatic region is 3.4 (expected: 3.3);
Anal. Calc. for C46H60Cl2N2O2Zr Æ CH2Cl2: C, 61.36;
H, 6.79; N, 3.04. Found: C, 60.74; H, 6.85; N, 2.96%.
Bis((3,5-di-tert-butyl-C6H2-2-O)PhC@NC6H5)ZrCl2
(2c): bright yellow powder, yield (48%). Single crystals
suitable for X-ray diffraction analysis were grown by
layer diffusion of hexane into a CH2Cl2 solution of com-
1
Cl2 (2i): yellow powder, yield (65%), H NMR (CDCl3,
300 MHz): isomers, d 7.48 (d, J = 2.5 Hz), 7.46 (m), 7.36
(d, J = 2.4 Hz), 7.31 (m), 7.25 (m), 7.21–7.10 (m),
6.96–6.90 (m), 6.83 (d, J = 7.7 Hz), 6.78 (m), 6.69 (t),
6.64 (d, J = 2.4 Hz), 6.61 (d, J = 8.6 Hz), 6.58 (d,
J = 2.4 Hz), 6.45 (d, J = 2.4 Hz), 6.41 (t, J = 7.2 Hz),
6.28 (t, J = 9.6 Hz), 6.18 (m), 1.52 (s), 1.36 (s), 1.25
(s), 1.24 (s), 1.15 (s), 1.06 (s), 1.04 (s), 1.02 (s), integral
ratio of total aliphatic vs. total aromatic region is 1.8
(expected: 1.6); Anal. Calc. for C54H58Cl2F2N2O2Zr:
C, 67.06; H, 6.04; N, 2.90. Found: C, 66.94; H, 5.89;
N, 2.87%.
1
plex 2c at room temperature over a few days. H NMR
(CDCl3, 300 MHz): major C2 isomer only, d 7.50 (2H, s)
7.33 (6H, m), 7.15–7.20 (8H, m), 7.02 (2H, t), 6.93 (2H,
s), 6.85 (4H, d), 1.55 (18H, s), 1.18 (18H, s). Anal. Calc.
for C54H60Cl2N2O2Zr: C, 69.65; H, 6.49; N, 3.01.
Found: C, 69.46; H, 6.42; N, 2.97%.
4.3. X-ray crystallography
Bis((3,5-di-tert-butyl-C6H2-2-O)(2-Me-Ph)C@NC6H5)-
ZrCl2 (2d): yellow powder, yield (43%), 1H NMR (CDCl3,
300 MHz): isomers, d 7.50 (m), 7.43 (d, J = 2.4 Hz), 7.35
(m), 7.27–6.60 (m), 6.49 (d), 6.47 (d), 6.40 (d), 6.32 (t), 6.99
(d), 5.87 (d), 2.16 (s), 2.09 (s), 1.98 (s), 1.88 (s), 1.62 (s), 1.51
(s), 1.48 (s), 1.29 (s), 1.12 (s), 1.05 (s), 1.00 (s), integral ratio
of total aliphatic vs. total aromatic region is 2.0 (expected:
1.9); Anal. Calc. for C56H64Cl2N2O2Zr: C, 70.12; H, 6.72;
N, 2.92. Found: C, 69.51; H, 6.84; N, 2.88%.
Crystals of 2c coated with vaseline were mounted
onto the goniometer and placed on a Rigaku RAXIS
RAPID IP diffractometer with graphite monochro-
˚
mated Mo Ka radiation (k = 0.71073 A) at 293 K. The
structures were solved by direct methods (SHELXS-97)
[14] and refined against all F2 data (SHELXL-97). All
non-hydrogen atoms were refined with anisotropic
thermal parameters. The hydrogen atoms were treated
as idealized contributions.
Bis((3,5-di-tert-butyl-C6H2-2-O)(2-F-Ph)C@NC6H5)-
1
ZrCl2 (2e): yellow solid, yield (62%), H NMR (CDCl3,

S. Chen et al. / Journal of Organometallic Chemistry 690 (2005) 4184–4191
4191
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using a 250 mL glass reactor with magnetic stir bar.
The pressure of ethylene was maintained by an electro-
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prescribed temperature until the solution was saturated
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have
been
deposited
with
the
Cambridge
Crystallographic Data Center, CCDC 244438 for the
complex 2c. Copies of this information may be ob-
tained free of charge from The Director, CCDC, 12
Union Road, Cambridge CB2 1EZ, UK, fax: +44
1223 336033; e-mail: eposit@ccdc.cam.ac.uk or www:
http://ccdc.cam.ac.uk.
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