Titanium and zirconium catalysts with [N,O] ligands: Syntheses, characterization, and their catalytic properties for olefin polymerization

Article abstract of DOI:10.1021/om3007568

A series of titanium and zirconium complexes L₂MCl₂ bearing salicylbenzoxazole ligands 2-(5-R-benzoxazol-2-yl)-6-R ¹-4-R²-phenol (L) (2a, M = Ti, R¹ = R ² = ^tBu, R = H; 2j, M = Ti, R¹ = cumyl, R ² = ^tBu, R = H; 2k, M = Ti, R¹ = Ad, R ² = ^tBu, R = H; 3a, M = Zr, R¹ = R² = ^tBu, R = H; 3b, M = Zr, R¹ = R² = ^tBu, R = CH₃; 3c, M = Zr, R¹ = R² = ^tBu, R = ^tBu; 3d, M = Zr, R¹ = R² = ^tBu, R = Cl; 3e, M = Zr, R¹ = R² = ^tBu, R = NO₂; 3f, M = Zr, R¹ = H, R² = H, R = H; 3g, M = Zr, R¹ = CH₃, R² = H, R = H; 3h, M = Zr, R¹ = ^tBu, R² = H, R = H; 3i, M = Zr, R¹ = ^tBu, R² = CH₃, R = H; 3j, M = Zr, R¹ = cumyl, R² = ^tBu, R = H; 3k, M = Zr, R¹ = Ad, R² = ^tBu, R = H) were synthesized. All the ligands and the metal complexes were fully characterized by ¹H and ¹³C NMR spectra and elemental analyses. The molecular structures of 3b,d,i,j were determined by single-crystal X-ray diffraction methods. Upon activation with methylaluminoxane (MAO), the zirconium complexes 3a-e,h-k bearing a bulky substitute on the ortho position of the phenol ring show high activities for ethylene polymerization and produced high-molecular-weight polyethylenes. For the titanium complexes, only trace polymers were obtained on activatation with MAO. The oligomerization of 1-hexene was also conducted by the zirconium complexes 3a-k, but only low molecular weights and stereoirregular oligomers were obtained.

Full text of DOI:10.1021/om3007568

Article
pubs.acs.org/Organometallics
Titanium and Zirconium Catalysts with [N,O] Ligands: Syntheses,
Characterization, and Their Catalytic Properties for Olefin
Polymerization
Xiao-Chao Shi and Guo-Xin Jin*
Shanghai Key Laboratory of Molecular Catalysis and Innovative Material, Department of Chemistry, Fudan University, 200433
Shanghai, People's Republic of China
S
* Supporting Information
ABSTRACT: A series of titanium and zirconium complexes
L2MCl2 bearing salicylbenzoxazole ligands 2-(5-R-benzoxazol-
2-yl)-6-R1-4-R2-phenol (L) (2a, M = Ti, R1 = R2 = tBu, R = H;
2j, M = Ti, R1 = cumyl, R2 = tBu, R = H; 2k, M = Ti, R1 = Ad,
R2 = tBu, R = H; 3a, M = Zr, R1 = R2 = tBu, R = H; 3b, M = Zr,
t
R1 = R2 = tBu, R = CH3; 3c, M = Zr, R1 = R2 = Bu, R = tBu;
3d, M = Zr, R1 = R2 = tBu, R = Cl; 3e, M = Zr, R1 = R2 = tBu,
R = NO2; 3f, M = Zr, R1 = H, R2 = H, R = H; 3g, M = Zr, R1 =
CH3, R2 = H, R = H; 3h, M = Zr, R1 = tBu, R2 = H, R = H; 3i,
M = Zr, R1 = tBu, R2 = CH3, R = H; 3j, M = Zr, R1 = cumyl, R2
t
t
= Bu, R = H; 3k, M = Zr, R1 = Ad, R2 = Bu, R = H) were
synthesized. All the ligands and the metal complexes were fully
1
characterized by H and 13C NMR spectra and elemental
analyses. The molecular structures of 3b,d,i,j were determined by single-crystal X-ray diffraction methods. Upon activation with
methylaluminoxane (MAO), the zirconium complexes 3a−e,h−k bearing a bulky substitute on the ortho position of the phenol
ring show high activities for ethylene polymerization and produced high-molecular-weight polyethylenes. For the titanium
complexes, only trace polymers were obtained on activatation with MAO. The oligomerization of 1-hexene was also conducted
by the zirconium complexes 3a−k, but only low molecular weights and stereoirregular oligomers were obtained.
Inspired by the success of the salicylaldiminato catalyst study,
group 4 transition metals based on several similar types of
[N,O] ligands have been reported, such as β-ketoimine (II),7
salicylpyridine (III),8 salicyloxazoline (IV),9 and so on.10−12
Among these ligands, salicyloxazoline had some potential
advantages over the salicylaldiminates, such as the stabilization
of the imine functionality. Floriani first investigated group 4
transition-metal complexes bearing salicyloxazoline ligands, but
low activity for ethylene polymerization was observed.9a
Introduction of sterically demanding substituents at the
oxazoline ring as well as the ortho position of the phenol
ring improved the catalytic ability sharply. Bochmann and Scott
reported zirconium complexes based on salicyloxazoline ligands
with steric substituents showing extremely active ethylene
polymerization catalysts up to 2.8 × 108 g of PE mol−1 h−1 in a
period of 1 min.9c However, these Zr catalysts were unstable
during the catalytic process and the activity decayed rather
rapidly. Half-sandwich group 4 complexes containing salicylox-
azoline ligands have also been synthesized and investigated for
ethylene polymerization and copolymerization with 1-hexene.9d
Previously, our group have designed and synthesized a series
of bidentate monoanionic [N,O] ligands, and their titanium,
INTRODUCTION
■
In the past decade, considerable effort has been devoted to the
development of non-metallocene catalysts for olefin polymer-
ization.1−6 The group 4 transition metal complexes based on
salicylaldiminato ligands, called FI catalysts, have been one of
the most exciting improvements.1 Those based on salicylaldi-
minato complexes of titanium/zirconium have shown unique
olefin polymerization catalytic ability to produce polyethylene
or polypropylene with high molecular weight and narrow
molecular weight distribution.2,3 Numerous studies have proved
the catalytic behaviors, and the microscopic structures of the
polymers are highly affected by the substituent on both the
phenoxy and the imino groups. Fujita found that a bulkier alkyl
substituent at the ortho-substituted position of the phenol ring
enhanced the polymerization activity significantly.2a Fujita and
Coates respectively reported titanium catalysts containing an
ancillary fluorinated imino group for living ethylene polymer-
ization and syndiotactic polymerization of propylene.2b,3
Moreover, group 4 non-metallocene catalysts have been
instrumental in studying polymerization mechanisms, inves-
tigating structure−property relationships, and synthesizing
polymers with tailored microstructures and desired physical
properties. Therefore, the study of new salicylaldiminato group
4 metal complexes as olefin polymerization catalysts has
attracted much attention and is an ever-growing area.
Received: August 7, 2012
© XXXX American Chemical Society
A
dx.doi.org/10.1021/om3007568 | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
powders in moderate yields. A general synthetic route for
titanium and zirconium complexes is shown in Scheme 2. The
zirconium complexes were obtained by treatment of 2 equiv of
the sodium salts of the salicylbenzoxazole ligands with ZrCl4 in
tetrahydrofuran (THF) at −78 °C. The purification was
performed by recrystallization from a mixture of CH2Cl2 and n-
hexane. The synthetic route for titanium complexes had some
difference from that for zirconium complexes. The proligands
La, Lj, and Lk were deprotonated by nBuLi in diethyl ether and
then treated with 0.5 equiv of TiCl4 at −78 °C to afford the the
desired titanium complexes 2a,j,k as red powders in high yields.
All of the titanium and zirconium complexes had good
solubility in polar organic solvents such as CH2Cl2 and THF
and were insoluble in apolar organic solvents such as hexane
and pentane. These complexes have been fully characterized by
NMR and elemental analyses. The chemical shifts of phenoxy
protons in ligands La−Lk are all around 12 ppm, and the
disappearance of the signals in complexes 2a,j,k and 3a−k
suggested the formation of new compounds.
Single crystals of 3b,d,i,j suitable for X-ray diffraction were
obtained from CH2Cl2/hexane solutions at low temperature. In
the solid state, 3b,d,i,j possessed a distorted-octahedral and
nearly C2 symmetric geometry. The distorted-octahedral
zirconium center is chelated by two ligands with two cis
nitrogen atoms, two trans oxygen atoms, and two cis chloride
atoms, completing the coordination sphere. The cis position of
the two chelated chlorides indicated the potential catalytic
ability of the zirconium complexes for ethylene polymerization.
The structure of complex 3b is given in Figure 1, and selected
bond lengths and angles for complexes 3b,d,i,j are summarized
in Table 1.
chromium, nickel, copper, and iridium complexes showed high
catalytic activities for norbornene, MMA, styrene, and ethylene
polymerization.11,13 We have reported that the titanium and
zirconium complexes containing salicylbenzothiazole [N,O]
ligands were efficient catalysts for ethylene polymerization.11
Moreover, the half-sandwich titanium salicylbenzoxazole
complexes and salicylbenzothiazole complexes were also
synthesized and tested for ethylene polymerization by our
group, and the catalytic results exhibited notable differences
originating from the salicylbenzoxazole and salicylbenzothiazole
ligands.14 In comparison with the salicyloxazoline ligands,
salicylbenzoxazole ligands have a stronger conjugative effect,
which was thought to have significant influence on the metal
center and the active center of the catalyst during the catalytic
reaction. Considering the unique properties of the salicylben-
zoxazole ligands, we were encouraged to develop group 4 metal
complexes containing salicylbenzoxazole ligands and investigate
their catalytic behaviors for olefin polymerization. Herein, we
report the syntheses and molecular structures of the titanium
and zirconium complexes bearing salicylbenzoxazole ligands
with different substituents, especially attaching bulk R1 (V), and
investigate their catalytic behaviors for ethylene polymerization.
The oligomerization of 1-hexene catalyzed by zirconium
complexes is also reported briefly.
In complex 3b, the Zr−O bond length is 1.994(3) Å, similar
to that in 3d (1.989(2) Å). The bond lengths of Zr−N in 3b,d
are 2.358(4) and 2.344(3) Å individually, and very similar bond
lengths for Zr−Cl were also observed in 3b (2.427(2) Å) and
3d (2.4136(11) Å). On comparison with the related
salicyloxazoline zirconium complex bis[2-(6-tert-butylsalicyli-
dene)-5,5′-dimethyloxazoline]ZrCl2 reported by Scott and
salicylaldiminato zirconium complex bis[2-(6-tert-
butylsalicylidene)anilinato]ZrCl2 reported by Fujita, little
difference was observed in the bond lengths of Zr−O, Zr−N,
and Zr−Cl.2a,9c The O1−Zr−O1i angle in complexes 3b,d are
166.84(18) and 165.83(13)°, which is very near to those of the
SYNTHESIS AND DISCUSSION
■
The salicylbenzoxazole ligands La−Lk were synthesized
according to our previous report in two steps: condensation
of the corresponding salicyaldehyde with o-aminophenol and
then oxidation with PhI(OAc)2 in refluxing acetonitrile
(Scheme 1).14,15 The desired products were separated through
column chromatography on silica gel as white to yellow
zirconium complexes reported by Fujita.2 In complex 3i, the
c
Zr−O bond distance is 2.000(7) Å, which is close to those in
3b,d and its corresponding zirconium complex bearing a
Scheme 1. Synthesis of the Ligands
B
dx.doi.org/10.1021/om3007568 | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Scheme 2. Synthesis of the Titanium and Zirconium Complexes
substiuent on the ortho position of the phenol ring, the bond
lengths and bond angles have no obvious differences from those
in 3b,d.
ETHYLENE POLYMERIZATION
■
With MAO as a cocatalyst, the titanium and zirconium
complexes were investigated for the polymerization of ethylene
under atmospheric pressure. For the titanium complexes 2a,j,k,
trace polymers were obtained even over the long period of 10
h. The trace activity toward ethylene polymerization of the
titanium complexes and the reported geometry of the titanium
complex bearing salicylbenzothiazole ligand convinced us that
the two chloride atoms were positioned in a trans fashion,
which did not provided two available cis-located sites for
efficient ethylene polymerization.11 More efficient than their
corresponding titanium analogues, the zirconium complexes
3a−e,h−k, which had a bulky substituent on the ortho position
of the phenol ring in the salicylbenzoxazole ligand, showed
good activities for ethylene polymerization under the initiation
of MAO. The results of the ethylene polymerization are
summarized in Table 2.
Figure 1. Structure of complex 3b (thermal ellipsoids are drawn at the
30% probability level). Hydrogen atoms and uncoordinated solvent are
omitted for clarity.
salicylbenzothiazole ligand.11 The O1−Zr−O1i angle in
complex 3i is 172.7(4)°, much larger than those observed in
3b,d and their corresponding salicylbenzothiazole zirconium
complexes; a similar phenomenon is also found for the angle
Cl1−Zr1−Cl1i. In complex 3j, which bears a bulky adamantyl
Table 1. Selected Bond Lengths (Å) and Angles (deg) for Complexes 3b,d,i,j
3b
3d
3i
3j
Bond Lengths
1.989(2)
Zr−O1
1.994(3)
1.994(3)
2.358(4)
2.358(4)
2.427(2)
2.427(2)
2.000(7)
2.000(7)
2.318(7)
2.318(7)
2.433(3)
2.433(3)
2.002(3)
1.992(3)
2.343(3)
2.314(3)
2.4208(10)
2.4074(10)
Zr−O (1i or 3)
Zr−N1
1.989(2)
2.344(3)
Zr−N(1i or 2)
Zr−Cl1
2.344(3)
2.4136(11)
2.4136(11)
Bond Angles
165.83(13)
80.13(14)
100.60(6)
76.82(9)
Zr−Cl(1i or 2)
O1−Zr−O(1i or 3)
N1−Zr−N(1i or 2)
Cl1−Zr−Cl(1i or 2)
N1−Zr1−O1
166.84(18)
79.51(19)
100.61(10)
76.79(12)
93.00(13)
90.67(12)
166.02(9)
172.7(4)
79.5(4
167.71(11)
78.39(11)
103.07(3)
76.22(11)
91.69(11)
93.61(8)
106.17(15)
76.9(3)
N1−Zr1−O(1i or 3)
N1−Zr1−Cl1
92.25(9)
97.4(3)
90.28(8)
88.43(19)
161.96(18)
N1−Zr1−Cl(1i or 2)
166.61(7)
160.82(8)
C
dx.doi.org/10.1021/om3007568 | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
effect could be also observed in our investigation. When R1 =
H, Me, only trace polymers and low catalytic abilities were
obtained under the optimized conditions. When the R1 is
changed to the bulkier tert-butyl, the catalytic ability of 3h
soared to 9.63 × 106 g of PE (mol of Zr)−1 h−1 (mol/L of
ethylene)−1, nearly 20 times higher than that of 3g.
Alternatively, replacement of the tert-butyl group at the R1
position in complex 3a with the sterically larger adamantyl
group or a cumyl group enhanced the polymerization activity of
the complexes (entries 22 and 26) and slightly increased the Mv
values of the resultant polymers, in comparison to complex 3a.
Complexes 3j,k displayed activities of 10.00 (Mv = 3.11 × 105 g
mol−1) and 7.23 × 106 g of PE (mol of Zr)−1 h−1 (mol/L of
ethylene)−1 (Mv = 3.15 × 105 g mol−1), respectively. It is
believed that the introduction of bulkier alkyl substituents at
the R1 position results in an effective separation between the
cationic active species and the anionic cocatalyst, thus
enhancing the catalytic ability of the procatalyst toward
ethylene.9c On changing different R2 substituents, the catalytic
activities varied in the order 3h (with H) > 3i (with Me) > 3a
Table 2. Ethylene Polymerization Results with Titanium and
Zirconium Complexes
a
Al/Zr
ratio
temp/
°C
time/
min
b
c
entry cat.
yield/g activity
Mv
1
3a
3b
3c
3c
3c
3c
3c
3c
3c
3c
3c
3c
3d
3d
3d
3d
3e
3f
1500
1500
500
30
30
30
30
30
30
30
30
0
15
15
15
15
15
15
15
15
15
15
15
15
15
5
0.426
0.770
0.168
0.586
0.632
0.460
0.372
0.225
0.365
0.443
0.108
trace
5.82
10.53
2.30
8.02
8.64
6.29
5.09
3.08
3.01
9.21
11.46
3.12
3.01
2.93
2.92
3.07
2.94
2.95
2.90
3.14
2.95
2.95
2
3
4
1000
1500
2000
2500
3000
1500
1500
1500
1500
1500
1500
1500
1500
1500
1500
1500
1500
1500
1500
1500
1500
1500
1500
1500
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
50
75
100
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
1.523
0.720
2.529
2.989
0.742
trace
20.82
29.54
17.29
10.22
10.14
2.97
2.97
3.05
3.06
3.00
30
60
15
60
60
15
15
15
5
t
(with Bu), and the electronic effects might be the most
important factor for R2. Introduction of a substituent group at
the R3 position showed an amazing influence on the catalytic
ability of the zirconium complexes. The catalytic activities
varied in the order 3d (with Cl) > 3b (with Me) > 3e (with
3g
3h
3i
0.134
0.704
0.465
0.731
0.317
1.066
1.686
0.529
trace
0.46
9.63
3.01
3.69
3.08
3.11
3.06
3.12
3.21
3.15
6.36
t
NO2) > 3a (with Bu) > 3i (with H). The activity of 3a was
3j
10.00
13.01
7.29
5.82 × 106 g of PE (mol of Zr)−1 h−1 (mol/L of ethylene)−1,
while complex 3d presented the highest activity, up to 20.82 ×
106 g of PE (mol of Zr)−1 h−1 (mol/L of ethylene)−1, 4 times
that of 3a. The catalytic lifetimes of the zirconium complexes
were also investigated, and we fortunately found that these
catalysts were very long-lived at 30 °C. The relationship
between the polymerization time and the polymer yield
indicated that complexes 3d,j had a catalytic lifetime of at
least 1 h, as shown in Figure 2.
3j
3j
30
60
15
60
3j
5.76
3k
2j
7.23
a
Conditions: complex, 2.5 μmol; solvent, toluene; Vtotal = 50 mL;
b
ethylene pressure, 1 atm. Activity in units of 106 g of PE (mol of
Zr)−1 h−1 (mol/L of ethylene)−1 (ethylene concentration in toluene at
1 atm: 0.194 mol/L at 0 °C, 0.117 mol/L at 30 °C, 0.077 mol/L at 50
c
°C, and 0.015 mol/L at 75 °C). Mv measured by the Ubbelohde
calibrated viscosimeter technique, in units of 105 g mol−1.
The catalytic conditions for ethylene polymerization have
been optimized by procatalyst 3c, and the most important
catalytic conditions Al/Zr and reaction temperature were
investigated in detail. Along with an increase of Al/Zr at 30 °C
as observed in Table 2, the catalytic ability of 3c first increased
to reach the maximum activity of 8.64 × 106 g of PE (mol of
Zr)−1 h−1 (mol/L of ethylene)−1 at a Al/Zr molar ratio of 1500
(entry 5, Table 2) and then decreased gradually. The influence
of Al concentration on the termination of polymer chains can
readily clarify such a phenomenon.16 In contrast to the notable
change in activity, the increase of the Al/Zr molar ratio has a
negative effect on the viscosity average molecular weight (Mv)
of the obtained polymers. The reaction temperature also
influenced the catalytic ability significantly, and the productiv-
ities were increased from 3.01 × 106 to 11.46 × 106 g of PE
(mol of Zr)−1 h−1 (mol/L of ethylene)−1 with an elevation of
the temperature to 75 °C, but when the temperature was
increased to 100 °C, only trace polymer was obtained, due to
the ultralow ethylene concentration in toluene (runs 5 and 9−
12, Table 2). The Mv values of the resultant polymers decreased
slightly as the reaction temperature was increased.
Figure 2. Lifetime plot of ethylene polymerization for complexes 3d,j
at 30 °C. Reaction conditions: zirconium complex 2.5 μmol, Al/Zr =
1500, ethylene 1 bar, toluene 50 mL.
Upon activation with MAO, the zirconium complexes 3a−k
show low to moderate catalytic activity for 1-hexene
oligomerization, and 3e exhibited the peak activity with 7.03
× 103 g of 1-hexene (mol of Zr)−1 h−1. The molecular weights
of the obtained oligomers were very low, such as 710 g mol−1
for 3b calculated from the 13C NMR spectrum.17 The
oligomers produced by the zirconium complex are shown by
The substituents R1, R2, and R3 had a significant effect on the
catalytic ability. As in previous literature reports, the steric
hindrance of R1 in the typical FI catalyst had a vital influence on
catalytic activity in non-metallocene systems.2a,9c,11 The same
D
dx.doi.org/10.1021/om3007568 | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
1
Synthesis of Ligand Lc. A procedure similar to that used for the
preparation of La was employed. Yield: 1.42 g (37.5%). 1H NMR (500
MHz, CDCl3, ppm): δ 11.97 (s, 1H, Ph-OH), 7.90 (s, 1H, Ph-H), 7.71
(s, 1H, Ph-H), 7.51 (s, 1H, Ph-H), 7.32 (d, 1H, Ph-H), 7.10 (d, 1H,
Ph-H), 1.50 (s, 9H, −C(CH3)3), 1.40(s, 9H, −C(CH3)3), 1.38 (s, 9H,
−C(CH3)3). 13C NMR (125 MHz, CDCl3, ppm): 164.4, 156.5, 150.9,
145.2, 144.3, 140.2, 138.6, 130.9, 129.0, 128.3, 126.5, 125.1, 115.9,
110.2, 35.6, 34.8, 31.5, 31.3, 29.8. Anal. Calcd for C25H33NO2: C,
79.11; H, 8.76; N, 3.69. Found: C, 79.29; H, 8.75; N, 3.58.
Synthesis of Ligand Ld. A procedure similar to that used for the
preparation of La was employed. Yield: 0.93 g (26.0%). 1H NMR (500
MHz, CDCl3, ppm): δ 11.73 (s, 1H, Ph-OH), 7.92 (s, 1H, Ph-H), 7.66
(s, 1H, Ph-H), 7.60 (s, 1H, Ph-H), 7.49 (d, 1H, Ph-H), 7.31 (d, 1H,
Ph-H), 2.43 (s, 3H, −CH3), 1.57 (s, 9H, −C(CH3)3), 1.44 (s, 9H,
−C(CH3)3). 13C NMR (125 MHz, CDCl3, ppm): 165.4, 156.2, 147.7,
141.4, 141.3, 137.5, 130.5, 129.1, 125.4, 121.4, 119.0, 111.3, 109.4,
35.5, 34.6, 31.6, 29.6. Anal. Calcd for C21H24ClNO2: C, 70.48; H, 6.76;
N, 3.91. Found: C, 71.01; H, 6.52; N, 3.89.
Synthesis of Ligand Le. A procedure similar to that used for the
preparation of La was employed. Yield: 1.01 g (27.4%). 1H NMR (500
MHz, CDCl3, ppm): δ 11.45 (s, 1H, Ph-OH), 8.57 (s, 1H, Ph-H), 8.33
(d, 1H, Ph-H), 7.88 (s, 1H, Ph-H), 7.73 (d, 1H, Ph-H), 7.57 (s, 1H,
Ph-H), 1.48 (s, 9H, −C(CH3)3), 1.37 (s, 9H, −C(CH3)3). 13C NMR
(125 MHz, CDCl3, ppm): 167.0, 156.5, 152.7, 145.7, 141.8, 140.8,
137.8, 129.9, 121.5, 121.3, 115.2, 110.8, 108.8, 35.4, 34.5, 31.5, 29.5.
Anal. Calcd for C21H24N2O4: C, 68.46; H, 6.57; N, 7.60. Found: C,
68.59; H, 6.44; N, 7.81.
Synthesis of Ligand Lf. A procedure similar to that used for the
preparation of La was employed. Yield: 0.60 g (28.2%). 1H NMR (500
MHz, CDCl3, ppm): δ 11.45 (s, 1H, Ph-OH), 7.96 (d, 1H, Ph-H),
7.67 (m, 1H, Ph-H), 7.54 (m, 1H, Ph-H), 7.40 (m, 1H, Ph-H), 7.32
(m, 2H, Ph-H), 7.11 (d, 1H, Ph-H), 6.97 (t, 1H, Ph-H). 13C NMR
(125 MHz, CDCl3, ppm): 163.0, 158.8, 149.2, 140.1, 133.7, 127.2,
125.4, 125.1, 119.7, 119.3, 117.5, 110.6. Anal. Calcd for C13H9NO2: C,
73.92; H, 4.29; N, 6.63. Found: C, 73.45; H, 4.13; N, 6.46.
Synthesis of Ligand Lg. A procedure similar to that used for the
preparation of La was employed. Yield: 0.76 g (33.6%). 1H NMR (500
MHz, CDCl3, ppm): δ 11.63 (s, 1H, Ph-OH), 7.84 (d, 1H, Ph-H),
7.66 (m, 1H, Ph-H), 7.54 (m, 1H, Ph-H), 7.32 (m, 2H, Ph-H), 6.87 (t,
1H, Ph-H), 2.33 (s, 1H, −CH3). 13C NMR (125 MHz, CDCl3, ppm):
163.4, 157.2, 149.2, 140.2, 134.6, 126.6, 125.3, 124.8, 119.2, 119.1,
110.7, 109.9, 16.1. Anal. Calcd for C14H11NO2: C, 74.65; H, 4.92; N,
6.22. Found: C, 73.95; H, 4.89; N, 6.39.
Synthesis of Ligand Lh. A procedure similar to that used for the
preparation of La was employed. Yield: 0.96 g (32.0%). 1H NMR (500
MHz, CDCl3, ppm): δ 12.09 (s, 1H, Ph-OH), 7.92 (d, 1H, Ph-H),
7.70 (m, 1H, Ph-H), 7.59 (m, 1H, Ph-H), 7.44 (d, 1H, Ph-H), 7.36 (m,
2H, Ph-H), 6.94 (t, 1H, Ph-H), 1.49 (s, 9H, −C(CH3)3). 13C NMR
(125 MHz, CDCl3, ppm): 163.7, 158.0, 149.2, 140.0, 137.9, 130.8,
125.3, 125.0, 119.1, 118.9, 110.7, 35.2, 29.5. Anal. Calcd for
C17H17NO2: C, 76.38; H, 6.41; N, 5.24. Found: C, 75.96; H, 6.63;
N, 5.19.
an H NMR analysis of the unsaturated chain end groups:
vinylidene (δ 4.68 and 4.76 ppm) and vinylene end groups (δ
5.3 ppm) in around a 2/5 ratio.
CONCLUSION
■
A family of group 4 precatalysts supported by salicylbenzox-
azole ligands bearing various substituents has been designed
and synthesized. X-ray diffraction studies indicated a distorted-
octahedral and nearly C2 symmetric geometry of the zirconium
complexes. In comparison with the high productivities of their
zirconium analogues, the titanium complexes 2a,j,k were almost
inactive toward olefin polymerization upon activation with
methylaluminoxane. This work has shown that the steric
hindrance and the electronic effect of the ligands remarkably
affect the catalytic activities of the zirconium precatalysts. When
a bulky substituent was attached at the ortho position of the
phenol ring, 3a−e,h−k showed high activities for ethylene
polymerization up to 29.54 × 106 g of PE (mol of Zr)−1 h−1
(mol/L of ethylene)−1 over a period of 5 min. The substituent
on the benzoxazole also affected the catalytic ability of the
zirconium complexes strongly, and the highest ability was
observed when R = Cl. The lifetimes of the catalysts 3d,j were
more than 1 h. All of the obtained polymers had high molecular
weights, around 105 g mol−1, and the ligands had no significant
influence on the Mv values of the polymers. The zirconium
complexes could also catalyze the oligomerization of 1-hexene
to give low molecular weights and stereoirregular oligomers.
EXPERIMENTAL SECTION
■
General Considerations. All the operations were carried out
under a pure argon atmosphere using standard Schlenk techniques.
Tetrahydrofuran (THF), hexane, and toluene were distilled from
sodium−benzophenone. Dichloromethane was distilled from calcium
hydride. Commercial reagents, namely nBuLi, methylaluminoxane
(MAO), ZrCl4, and TiCl4, were purchased from Acros Co. and used
without further purification. The ligands La−Lk were prepared
according to the literature.14,15 Other commercially available reagents
were purchased and used without purification. 1H (500 MHz) and 13
NMR (125 MHz) measurements were obtained on a Bruker AC500
spectrometer in CDCl3 solution. Elemental analyses for C, H, and N
were carried out on an Elementar III Vario EI analyzer.
Synthesis of Ligand La. A solution of 3,5-di-tert-butylsalicylalde-
hyde (2.34 g, 10 mmol), o-aminophenol (2.21 g, 10 mmol), and few
drops of acetic acid in 50 mL of methanol was refluxed with stirring for
10 h under nitrogen. When the resulting mixture was cooled to room
temperature, PhI(OAc)2 (3.54 g, 11 mmol) was added and the mixture
immediately turned black. After the mixture was refluxed again for 1 h
in open air, the solvent was evaporated to dryness and the black crude
product was chromatographed on silica gel with hexane/EtOAc 10/1
C
1
Synthesis of Ligand Li. A procedure similar to that used for the
preparation of La was employed. Yield: 1.16 g (41.2%). 1H NMR (500
MHz, CDCl3, ppm): δ 11.89 (s, 1H, Ph-OH), 7.73 (s, 1H, Ph-H), 7.70
(m, 1H, Ph-H), 7.58 (m, 1H, Ph-H), 7.36 (m, 2H, Ph-H), 7.27 (s, 1H,
Ph-H), 2.37 (s, 3H, Ph−CH3), 1.52 (s, 9H, −C(CH3)3). 13C NMR
(125 MHz, CDCl3, ppm): 163.8, 156.0, 149.2, 140.1, 137.7, 132.1,
127.8, 125.2, 124.9, 119.1, 110.6, 110.3, 35.1, 29.6. Anal. Calcd for
C18H19NO2: C, 76.84; H, 6.81; N, 4.98. Found: C, 77.15; H, 6.99; N,
4.92.
Synthesis of Ligand Lj. A procedure similar to that used for the
preparation of La was employed. Yield: 1.03 g (30.5%). 1H NMR (500
MHz, CDCl3, ppm): δ 12.01 (s, 1H, Ph-OH), 7.91 (s, 1H, Ph-H), 7.67
(d, 1H, Ph-H), 7.60 (d, 1H, Ph-H), 7.46 (s, 1H, Ph-H), 7.36 (m, 2H,
Ph-H), 2.25 (s, 6H, Ph-C(CH2)3−), 2.12 (m, 3H, −CH(CH2)3−),
1.82 (s, 6H, −CH(CH2)2−), 1.39 (s, 9H, −C(CH3)3). 13C NMR (125
MHz, CDCl3, ppm): 164.2, 156.2, 149.1, 141.3, 140.1, 137.5, 128.6,
125.1, 124.9, 121.1, 119.0, 110.6, 109.8, 41.4, 40.4, 37.6, 37.2, 34.6,
to give the pure product La (1.02 g, 32.0%) as a white powder. H
NMR (500 MHz, CDCl3, ppm): δ 11.94 (s, 1H, Ph-OH), 7.91 (s, 1H,
Ph-H), 7.70 (m, 1H, Ph-H), 7.60 (m, 1H, Ph-H), 7.51 (s, 1H, Ph-H),
7.32 (m, 2H, Ph-H), 1.51 (s, 9H, −C(CH3)3), 1.38 (s, 9H,
−C(CH3)3). 13C NMR (125 MHz, CDCl3, ppm): 164.1, 156.0,
149.2, 141.2, 140.2, 137.3, 128.6, 125.2, 124.9, 121.4, 119.1, 110.6,
109.9, 35.4, 34.5, 31.7, 29.6. Anal. Calcd for C21H25NO2: C, 77.98; H,
7.79; N, 4.33. Found: C, 78.17; H, 7.64; N, 4.43.
Synthesis of Ligand Lb. A procedure similar to that used for the
preparation of La was employed. Yield: 1.14 g (33.7%). 1H NMR (500
MHz, CDCl3, ppm): δ 12.03 (s, 1H, Ph-OH), 7.95 (s, 1H, Ph-H), 7.57
(s, 1H, Ph-H), 7.48 (s, 1H, Ph-H), 7.47 (d, 1H, Ph-H), 7.17 (d, 1H,
Ph-H), 2.49 (s, 3H, −CH3), 1.58 (s, 9H, −C(CH3)3), 1.44 (s, 9H,
−C(CH3)3). 13C NMR (125 MHz, CDCl3, ppm): 164.2, 155.9, 147.4,
141.2, 140.3, 137.3, 134.8, 128.4, 126.2, 121.3, 119.1, 110.0, 109.9,
35.4, 34.5, 31.7, 29.6, 21.6. Anal. Calcd for C22H27NO2: C, 78.30; H,
8.06; N, 4.15. Found: C, 78.81; H, 8.15; N, 4.24.
E
dx.doi.org/10.1021/om3007568 | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
31.6, 29.2. Anal. Calcd for C27H31NO2: C, 80.76; H, 7.78; N, 3.49.
Found: C, 81.24; H, 7.63; N, 3.55.
Anal. Calcd for C44H52Cl2N2O4Zr: C, 63.29; H, 6.28; N, 3.35. Found:
C, 62.87; H, 6.52; N, 3.38.
Synthesis of Ligand Lk. A procedure similar to that used for the
preparation of La was employed. Yield: 1.03 g (30.5%). 1H NMR (500
MHz, CDCl3, ppm): δ 11.59 (s, 1H, Ph-OH), 7.98 (s, 1H, Ph-H), 7.72
(s, 1H, Ph-H), 7.58 (m, 2H, Ph-H), 7.30 (m, 6H, Ph-H), 7.18 (m, 1H,
Ph-H), 1.83 (s, 6H, Ph−C(CH3)2−), 1.46 (s, 9H, −C(CH3)3). 13C
NMR (125 MHz, CDCl3, ppm): 163.7, 155.3, 150.8, 149.2, 141.2,
140.1, 136.8, 128.8, 128.0, 125.7, 125.3, 124.9, 121.8, 119.0, 110.6,
110.1, 32.6, 34.6, 31.7, 29.6. Anal. Calcd for C26H27NO2: C, 81.01; H,
7.06; N, 3.63. Found: C, 80.84; H, 7.21; N, 3.69.
Synthesis of 3c. A procedure similar to that used for the
1
preparation of 3a was employed. Yield: 0.239 g (52.1%). H NMR
(500 MHz, CDCl3, ppm): δ 8.00 (s, 1H, Ph-H), 7.74 (s, 1H, Ph-H),
7.36 (s, 1H, Ph-H), 7.29 (d, 1H, Ph-H), 7.18 (d, 1H, Ph-H), 1.67 (s,
9H, −C(CH3)3), 1.40(s, 9H, −C(CH3)3), 0.88 (s, 9H, −C(CH3)3).
13C NMR (125 MHz, CDCl3, ppm): 165.3, 159.1, 149.7, 146.2, 143.3,
140.1, 137.6, 131.4, 129.1, 128.3, 124.1, 122.7, 114.5, 109.9, 35.6, 34.9,
34.8, 31.6, 31.2, 29.8. Anal. Calcd for C50H64Cl2N2O4Zr: C, 65.33; H,
7.02; N, 3.05. Found: C, 65.87; H, 7.32; N, 3.13.
Synthesis of 2a. A solution of n-Butyllithium in hexane was added
dropwise to a stirred solution of La (0.184 g, 1.00 mmol) in dried
diethyl ether (10 mL) at −78 °C. The mixture was warmed to room
temperature and stirred for 2 h. The resulting mixture was added
dropwise to a solution of TiCl4 (0.5 mmol) in dried diethyl ether (10
mL) at −78 °C with stirring. The mixture was warmed to room
temperature and stirred for 12 h. Then, the reaction mixture was
concentrated in vacuo to give a red solid. A 20 mL portion of CH2Cl2
was added to the solid, and the mixture was stirred for 10 min and
filtered. The filtrate was concentrated to 2 mL in vacuo and hexane
Synthesis of 3d. A procedure similar to that used for the
preparation of 3a was employed. Yield: 0.240 g (54.8%). H NMR
1
(500 MHz, CDCl3, ppm): δ 7.89 (s, 1H, Ph-H), 7.80 (s, 1H, Ph-H),
7.57 (s, 1H, Ph-H), 7.38 (d, 1H, Ph-H), 7.19 (d, 1H, Ph-H), 1.71 (s,
9H, −C(CH3)3), 1.36 (s, 9H, −C(CH3)3). 13C NMR (125 MHz,
CDCl3, ppm): 166.3, 159.3, 146.8, 143.6, 139.9, 138.4, 132.3, 131.6,
126.6, 122.7, 119.1, 113.7, 111.3, 35.6, 34.8, 31.4, 29.7. Anal. Calcd for
C42H46Cl4N2O4Zr: C, 57.59; H, 5.29; N, 3.20. Found: C, 58.02; H,
5.12; N, 3.32.
Synthesis of 3e. A procedure similar to that used for the
1
1
added to yield a red solid. Yield: 0.258 g (67.7%). H NMR (500
preparation of 3a was employed. Yield: 0.245 g (54.7%). H NMR
MHz, CDCl3, ppm): δ 8.06 (s, 1H, Ph-H), 7.81 (s, 1H, Ph-H), 7.50
(m, 2H, Ph-H), 7.37 (m, 1H, Ph-H), 7.05 (m, 1H, Ph-H), 1.68 (s, 9H,
−C(CH3)3), 1.45 (s, 9H, −C(CH3)3). 13C NMR (125 MHz, CDCl3,
ppm): 163.7, 161.8, 148.2, 144.5, 139.0, 138.3, 131.2, 126.2, 122.9,
118.9, 116.2, 110.8, 35.7, 34.9, 31.5, 29.9. Anal. Calcd for
C42H48Cl2N2O4Ti: C, 66.06; H, 6.34; N, 3.67. Found: C, 66.12; H,
6.11; N, 3.79.
(500 MHz, CDCl3, ppm): δ 8.37 (s, 1H, Ph-H), 8.22 (s, 1H, Ph-H),
7.94 (m, 2H, Ph-H), 7.64 (m, 1H, Ph-H), 1.69 (s, 9H, −C(CH3)3),
1.38 (s, 9H, −C(CH3)3). 13C NMR (125 MHz, CDCl3, ppm): 168.1,
159.9, 154.7, 146.0, 144.2, 140.2, 138.2, 134.1, 122.8, 122.4, 115.0,
113.0, 111.2, 35.7, 34.8, 31.3, 29.5. Anal. Calcd for C42H46Cl4N4O8Zr:
C, 56.24; H, 5.17; N, 6.25. Found: C, 56.02; H, 5.31; N, 6.31.
Synthesis of 3f. A procedure similar to that used for the
1
Synthesis of 2j. A procedure similar to that used for the
preparation of 3a was employed. Yield: 0.198 g (68.1%). H NMR
1
preparation of 2a was employed. Yield: 0.332 g (72.4%). H NMR
(500 MHz, CDCl3, ppm): δ 7.89 (s, 1H, Ph-H), 7.59 (m, 1H, Ph-H),
7.43 (m, 2H, Ph-H), 7.15 (m, 2H, Ph-H), 6.88 (t, 1H, Ph-H). We
could not obtain a perfect 13C NMR spectrum due to the poor
solubility. Anal. Calcd for C26H16Cl2N2O4Zr: C, 53.61; H, 2.77; N,
4.81. Found: C, 53.97; H, 2.89; N, 4.91.
(500 MHz, CDCl3, ppm): δ 8.04 (s, 1H, Ph-H), 7.77 (s, 1H, Ph-H),
7.47 (d, 1H, Ph-H), 7.39 (d, 1H, Ph-H), 7.22 (m, 1H, Ph-H), 7.02 (m,
1H, Ph-H), 2.43 (s, 6H, Ph-C(CH2)3−), 2.10 (s, 3H, −CH(CH2)3−),
1.73−1.99 (m, 6H, −CH(CH2)2−), 1.45 (s, 9H, −C(CH3)3). 13C
NMR (125 MHz, CDCl3, ppm): 163.7, 162.1, 148.3, 144.5, 139.4,
138.4, 131.6, 126.1, 125.6, 122.8, 119.1, 116.3, 110.7, 40.6, 37.9, 36.9,
35.0, 31.7, 31.6, 29.2, 22.7, 14.2. Anal. Calcd for C54H60Cl2N2O4Ti: C,
70.51; H, 6.57; N, 3.05. Found: C, 69.88; H, 6.64; N, 3.19.
Synthesis of 3g. A procedure similar to that used for the
1
preparation of 3a was employed. Yield: 0.145 g (47.5%). H NMR
(500 MHz, CDCl3, ppm): δ 7.91 (d, 1H, Ph-H), 7.71 (d, 1H, Ph-H),
7.41 (m, 2H, Ph-H), 7.25 (m, 1H, Ph-H), 7.18 (m, 2H, Ph-H), 2.53 (s,
3H, −CH3). We could not obtain a perfect 13C NMR spectrum due to
the poor solubility. Anal. Calcd for C28H20Cl2N2O4Zr: C, 55.08; H,
3.30; N, 4.59. Found: C, 54.96; H, 3.22; N, 4.63.
Synthesis of 2k. A procedure similar to that used for the
1
preparation of 2a was employed. Yield: 0.313 g (68.2%). H NMR
(500 MHz, CDCl3, ppm): δ 8.12 (s, 1H, Ph-H), 7.66 (s, 1H, Ph-H),
7.44 (m, 2H, Ph-H), 7.02−7.34 (br, 7H, Ph-H), 1.48 (s, 3H, Ph-
C(CH3)2−), 1.45 (s, 9H, −C(CH3)3), 1.43 (s, 3H, Ph−C(CH3)2−).
13C NMR (125 MHz, CDCl3, ppm): 163.8, 161.1, 157.4, 148.9, 148.5,
144.1, 138.6, 131.2, 126.9, 126.1, 125.1, 124.8, 123.0, 116.3, 109.9,
42.5, 34.8, 31.7. Anal. Calcd for C52H52Cl2N2O4Ti: C, 70.35; H, 5.90;
N, 3.16. Found: C, 69.55; H, 5.62; N, 3.19.
Synthesis of 3h. A procedure similar to that used for the
1
preparation of 3a was employed. Yield: 0.189 g (54.5%). H NMR
(500 MHz, CDCl3, ppm): δ 8.02 (d, 1H, Ph-H), 7.60 (d, 1H, Ph-H),
7.51 (d, 1H, Ph-H), 7.37 (m, 2H, Ph-H), 7.03 (m, 1H, Ph-H), 1.62 (s,
9H, −C(CH3)3). We could not obtain a perfect 13C NMR spectrum
due to the poor solubility. Anal. Calcd for C34H32Cl2N2O4Zr: C, 58.78;
H, 4.64; N, 4.03. Found: C, 59.12; H, 4.58; N, 4.09.
Synthesis of 3a. To a mixture of NaH (0.024 g, 1.0 mmol) and La
(0.323 g, 1.00 mmol) was added 10 mL of THF at −78 °C. The
solution was warmed to room temperature and stirred for 4 h. The
mixture was filtered, and the filtrate was added to a solution of ZrCl4
(0.117 g, 0.5 mmol) in 10 mL of THF at −78 °C. The resulting clear
solution was warmed to room temperature and kept stirring overnight.
The solvent was removed under vacuum, and the residue was extracted
in 20 mL of CH2Cl2 to remove NaCl salt. Removal of volatiles under
Synthesis of 3i. A procedure similar to that used for the
1
preparation of 3a was employed. Yield: 0.219 g (60.5%). H NMR
(500 MHz, CDCl3, ppm): δ 7.81 (s, 1H, Ph-H), 7.58 (s, 1H, Ph-H),
7.47 (m, 2H, Ph-H), 7.27 (m, 1H, Ph-H), 7.08 (s, 1H, Ph-H), 2.39 (s,
3H, −CH3), 1.61 (s, 9H, −C(CH3)3). 13C NMR (125 MHz, CDCl3,
ppm): 165.0, 159.2, 148.3, 140.1, 137.7, 134.8, 129.9, 126.4, 125.8,
118.9, 114.6, 110.7, 35.2, 29.7, 21.2. Calcd for C36H36Cl2N2O4Zr: C,
59.82; H, 5.02; N, 3.88. Found: C, 59.43; H, 4.96; N, 3.83.
1
vacuum afforded a light yellow powder of 3a (0.231 g, 57.4%). H
NMR (500 MHz, CDCl3, ppm): δ 7.95 (s, 1H, Ph-H), 7.50−7.70 (m,
4H, Ph-H), 7.07 (m, 1H, Ph-H), 1.61 (s, 9H, −C(CH3)3), 1.38 (s, 9H,
−C(CH3)3). 13C NMR (125 MHz, CDCl3, ppm): 166.0, 153.1, 148.3,
142.2, 140.2, 134.3, 130.5, 124.9, 123.2, 121.5, 119.1, 112.9, 109.1,
35.7, 34.9, 31.5, 29.6. Anal. Calcd for C42H48Cl2N2O4Zr: C, 62.51; H,
6.00; N, 3.47. Found: C, 63.20; H, 6.23; N, 3.39.
Synthesis of 3j. A procedure similar to that used for the
preparation of 3a was employed. Yield: 0.280 g (58.2%). H NMR
1
(500 MHz, CDCl3, ppm): δ 7.95 (s, 1H, Ph-H), 7.71 (s, 1H, Ph-H),
7.47 (m, 2H, Ph-H), 7.25 (s, 1H, Ph-H), 7.01 (s, 1H, Ph-H), 2.43 (s,
6H, Ph-C(CH2)3−), 2.14 (m, 3H, −CH(CH2)3−), 1.75 (m, 6H,
−CH(CH2)2−), 1.38 (s, 9H, −C(CH3)3). 13C NMR (125 MHz,
CDCl3, ppm): 165.2, 159.4, 148.2, 143.2, 140.0, 137.6, 131.7, 126.2,
125.6, 122.8, 119.0, 114.3, 110.6, 40.6, 37.8, 36.9, 34.8, 31.7, 31.5, 29.2,
22.7, 14.2. Anal. Calcd for C54H60Cl2N2O4Zr: C, 67.34; H, 6.28; N,
2.91. Found: C, 67.98; H, 6.01; N, 3.09.
Synthesis of 3b. A procedure similar to that used for the
1
preparation of 3a was employed. Yield: 0.261 g (62.5%). H NMR
(500 MHz, CDCl3, ppm): δ 7.93 (s, 1H, Ph-H), 7.76 (s, 1H, Ph-H),
7.33 (m, 2H, Ph-H), 7.01 (s, 1H, Ph-H), 1.98 (s, 3H, −CH3), 1.71 (s,
9H, −C(CH3)3), 1.37 (s, 9H, −C(CH3)3). 13C NMR (125 MHz,
CDCl3, ppm): 165.0, 159.1, 150.8, 146.4, 143.2, 139.7, 137.6, 135.7,
131.0, 127.3, 122.7, 119.0, 114.5, 109.9, 35.6, 34.8, 31.5, 29.8, 21.0.
Synthesis of 3k. A procedure similar to that used for the
1
preparation of 3a was employed. Yield: 0.259 g (55.7%). H NMR
(500 MHz, CDCl3, ppm): δ 8.02 (s, 1H, Ph-H), 7.76 (s, 1H, Ph-H),
F
dx.doi.org/10.1021/om3007568 | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
7.56 (m, 2H, Ph-H), 6.73−7.25 (br, 7H, Ph-H), 1.73 (s, 6H, Ph-
C(CH3)2−), 1.43 (s, 9H, −C(CH3)3). 13C NMR (125 MHz, CDCl3,
ppm): 165.0, 158.6, 149.3, 148.2, 142.7, 137.6, 131.2, 127.5, 125.9,
125.6, 125.0, 123.3, 114.4, 110.2, 42.5, 34.7, 31.6. Anal. Calcd for
C52H52Cl2N2O4Zr: C, 67.08; H, 5.63; N, 3.01. Found: C, 67.13; H,
5.89; N, 3.14.
X-ray Crystallography. For complexes 3b,d,i,j, a single crystal
suitable for X-ray analysis was sealed into a glass capillary; all the
intensity data of the single crystal were collected on the CCD-Bruker
Smart APEX system. All determinations of the unit cell and intensity
data were performed with graphite-monochromated Mo Kα radiation
(λ = 0.710 73 Å) or Cu Kα radiation (λ = 1.541 78 Å). All data were
collected at room temperature or −100 °C using the ω scan technique.
These structures were solved by direct methods, using Fourier
techniques, and refined on F2 by a full-matrix least-squares method.
The PLATON SQUEEZE12 process was used to omit solvent
molecules, and the structures were refined to convergence. All the
non-hydrogen atoms were refined anisotropically, and all the hydrogen
atoms were included but not refined. Crystallographic data are
summarized in the Supporting Information.
(2) (a) 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.
(b) Mitani, M.; Mohri, J.; Yoshida, Y.; Saito, J.; Ishii, S.; Tsuru, K.;
Matsui, S.; Furuyama, R.; Nakano, T.; Tanaka, H.; Kojoh, S.; Matsugi,
T.; Kashiwa, N.; Fujita, T. J. Am. Chem. Soc. 2002, 124, 3327.
(3) (a) Tian, J.; Coates, G. W. Angew. Chem., Int. Ed. 2000, 39, 3626.
(b) Hustad, P. D.; Tian, J.; Coates, G. W. J. Am. Chem. Soc. 2002, 124,
3614.
(4) Capacchione, C.; Proto, A.; Ebeling, H.; Mulhaupt, R.; Spaniol, T.
̈
P.; Moller, K.; Okuda, J. J. Am. Chem. Soc. 2003, 125, 4964.
̈
(5) (a) Kojoh, S.; Matsugi, T.; Saito, J.; Mitani, M.; Fujita, T.;
Kashiwa, N. Chem. Lett. 2001, 822. (b) Busico, V.; Cipullo, R.;
Friederichs, N.; Ronca, S.; Talarico, G.; Togrou, M.; Wang, B.
Macromolecules 2004, 37, 8201.
(6) (a) Luo, S.; Vela, J.; Lief, G. R.; Jordan, R. F. J. Am. Chem. Soc.
2007, 129, 8946. (b) Kochi, T.; Noda, S.; Yoshimura, K.; Nozaki, K. J.
Am. Chem. Soc. 2007, 129, 8948. (c) Yang, X.; Liu, C.; Wang, C.; Sun,
X.; Guo, Y.; Wang, X.; Wang, Z.; Xie, Z.; Tang, Y. Angew. Chem., Int.
Ed. 2009, 48, 8099.
Ethylene Polymerization. A 100 mL flask was equipped with an
ethylene inlet, a magnetic stirrer, and a vacuum line. The flask was
filled with 30 mL of freshly distilled toluene, MAO (10 wt % in
toluene) was added, and the flask was placed in a bath at the desired
polymerization temperature for 10 min. The polymerization reaction
was started by adding a toluene solution of the desired catalyst
precursor with a syringe. Then the solvent toluene was added to bring
the total volume of the solution to 50 mL. The polymerization was
carried out for the desired time and temperature and then quenched
with 3% HCl in ethanol (250 mL). The precipitated polymer was
filtered and then dried overnight in a vacuum oven at 80 °C.
1-Hexene Polymerizations. A dry 25 mL flask with a magnetic
stirrer was charged with 5 mL of 1-hexene at 30 °C. The
polymerization reaction was started by injection of a mixture of 1.6
mL of MAO and 5 μmol of the catalyst in toluene, and the total
volume of the reaction system was kept at 10 mL, adjusted with
toluene. After 20 h, the polymerization was quenched by injecting
acidified methanol (HCl (3 M)/methanol 1/1), Oligo(1-hexenes)
were purified by passing their hexane solution through a pipet
containing silica gel.
(7) (a) Li, X. F.; Dai, K.; Ye, W. P.; Pan, L.; Li, Y. S. Organometallics
2004, 23, 1223. (b) Tang, T. L.; Li, Y. G.; Ye, W. P.; Li, Y. S. J. Polym.
Sci., Part A: Polym. Chem. 2006, 44, 5846. (c) Ye, W. P.; Zhan, J.; Pan,
L.; Hu, N. H.; Li, Y. S. Organometallics 2008, 27, 3642. (d) Elo, P.;
Parssinen, A.; Nieger, M.; Leskela, M.; Repo, T. J. Organomet. Chem.
̈
̈
2009, 694, 2927. (e) Ye, W. P.; Shi, X. C.; Li, B.; Liu, J.; Li, Y. S.;
Cheng, Y. X.; Hu, N. H. Dalton Trans. 2010, 39, 9000.
(8) (a) Kui, S. C. F.; Zhu, N.; Chan, M. C. W. Angew. Chem., Int. Ed.
2003, 42, 1628. (b) Chan, M. C. W.; Kui, S. C. F.; Cole, J. M.;
McIntyre, G. J.; Matsui, S.; Zhu, N.; Tam, K. H. Chem. Eur. J. 2006, 12,
2607. (c) Tam, K. H.; Lo, J. C. Y.; Guo, Z.; Chan, M. C. W. J.
Organomet. Chem. 2007, 692, 4750. (d) Tam, K. H.; Chan, M. C. W.;
Kaneyoshi, H.; Makio, H.; Zhu, N. Organometallics 2009, 28, 5877.
(e) Zuccaccia, C.; Busico, V.; Cipullo, R.; Talarico, G.; Froese, R. D. J.;
Vosejpka, P. C.; Hustad, P. D.; Macchioni, A. Organometallics 2009,
28, 5455.
(9) (a) Cozzi, P. G.; Floriani, C. Inorg. Chem. 1995, 34, 2921.
(b) Cozzi, P. G.; Gallo, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C.
Organometallics 1995, 14, 4994. (c) Bott, R. K. J. B.; Hammond, M.;
Horton, P. N.; Lancaster, S. J.; Bochmann, M.; Scott, P. Dalton Trans.
2005, 3611. (d) Coles, S. R.; Clarkson, G. J.; Gott, A. L.; Munslow, I.
J.; Spitzmesser, S. K.; Scott, P. Organometallics 2006, 25, 6019.
(e) Gott, A. L.; Clarke, A. J.; Clarkson, G. J.; Munslow, I. J.; Wade, A.
R.; Scott, P. Organometallics 2008, 27, 2706.
ASSOCIATED CONTENT
* Supporting Information
■
S
Figures, a table, and CIF files giving structures and crystallo-
graphic data for 3b,d,i,j. This material is available free of charge
via the Internet at http://pubs.acs.org.
(10) (a) Niemeyer, J.; Kehr, G.; Frohlich, R.; Erker, G. Chem. Eur. J.
̈
2008, 14, 9499. (b) Niemeyer, J.; Kehr, G.; Frohlich, R.; Erker, G.
Dalton Trans. 2009, 3731.
̈
AUTHOR INFORMATION
Corresponding Author
(11) Jia, A. Q.; Jin, G. X. Dalton Trans. 2009, 8838.
■
(12) Elo, P.; Parssinen, A.; Rautiainen, S.; Nieger, M.; Leskela, M.;
̈
̈
Repo, T. J. Organomet. Chem. 2010, 695, 11.
*E-mail: gxjin@fudan.edu.cn. Fax: +86-21-65641740. Tel: +86-
21-65643776.
(13) (a) Huang, Y. B.; Jin, G. X. Dalton Trans. 2009, 767. (b) Huang,
Y. B.; Yu, W. B.; Jin, G. X. Organometallics 2009, 28, 4170. (c) Zhang,
D.; Jin, G. X.; Hu, N. H. Chem. Commun. 2002, 574. (d) Zhang, D.;
Jin, G. X.; Hu, N. H. Eur. J. Inorg. Chem. 2003, 8, 1570. (e) Zhang, D.;
Jin, G. X. Appl. Catal. A: Gen. 2004, 262, 85. (f) Zhang, D.; Jin, G. X.;
Weng, L. H.; Wang, F. S. Organometallics 2004, 23, 3270. (g) Guo, C.;
Zhang, D.; Wang, F.; Jin, G. X. J. Catal. 2005, 234, 356. (h) Wang, H.
Y.; Meng, X.; Jin, G. X. Dalton Trans. 2006, 2579. (i) Tang, G. R.; Jin,
G. X. Dalton Trans. 2007, 3840. (j) Meng, X.; Tang, G. R.; Jin, G. X.
Chem. Commun. 2008, 3178. (k) Jia, A. Q.; Jin, G. X. Organometallics
2009, 28, 1872.
(14) Shi, X. C.; Jin, G. X. Dalton Trans. 2011, 40, 1.
(15) Asada, H.; Ozeki, M.; Fujiwara, M.; Matsushita, T. Polyhedron
2002, 1139.
(16) Chen, E. Y. X.; Marks, T. J. Chem. Rev. 2000, 100, 1391.
(17) (a) Mazzeo, M.; Lamberti, M.; Daniela Pappalardo, D.;
Annunziata, L.; Pellecchia, C. J. Mol. Catal. A: Chem. 2009, 297, 9.
(b) Pan, Y.; Xu, T. Q.; Ge, Y. S.; Lu, X. B. Organometallics 2011, 30,
Notes
The authors declare no competing financial interest.
REFERENCES
■
(1) For reviews see: (a) Ittel, S. D.; Johnson, L. K.; Brookhart, M.
Chem. Rev. 2000, 100, 1169. (b) Coates, G. W.; Hustad, P. D.;
Reinartz, S. Angew. Chem., Int. Ed. 2002, 41, 2236. (c) Gibson, V. C.;
Spitzmesser, S. K. Chem. Rev. 2003, 103, 283. (d) Bianchini, C.;
Giambastiani, G.; Rios, I. G.; Mantovani, G.; Meli, A.; Segarra, A. M.
Coord. Chem. Rev. 2006, 250, 1391. (e) Janiak, C.; Lassahn, P.-G.;
Lozan, V. Macromol. Symp. 2006, 236, 88. (f) Gibson, V. C.; Redshaw,
C.; Solan, G. A. Chem. Rev. 2007, 107, 1745. (g) Matsugi, T.; Fujita, T.
Chem. Soc. Rev. 2008, 37, 1264. (h) Makio, H.; Fujita, T. Acc. Chem.
Res. 2009, 42, 1532. (i) Nakamura, A.; Ito, S.; Nozaki, K. Chem. Rev.
2009, 109, 5215. (j) Makio, H.; Terao, H.; Iwashita, A.; Fujita, T.
Chem. Rev. 2011, 111, 2363.
G
dx.doi.org/10.1021/om3007568 | Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
5687. (c) Xu, T. Q.; Liu, J.; Wu, G. P.; Lu, X. B. Inorg. Chem. 2011, 50,
10884.
H
dx.doi.org/10.1021/om3007568 | Organometallics XXXX, XXX, XXX−XXX