Synthesis, characterization, and catalytic properties of new half-sandwich zirconium(iv) complexes

Article abstract of DOI:10.1039/c2dt12105k

A number of new half-sandwich zirconium(iv) complexes bearing N,N-dimethylaniline-amido ligands with the general formula Cp*ZrCl ₂[ortho-(RNCH₂)(Me₂N)C₆H ₄] [R = 2,6-Me₂C₆H₃ (1), 2,6- ⁱPr₂C₆H₃ (2), ⁱPr (3), ^tBu (4)] were synthesized by the reaction of Cp*ZrCl ₃ with the corresponding ortho-(Me₂N)C₆H ₄CH₂NRLi. All new zirconium complexes were characterized by ¹H and ¹³C NMR, elemental analyses and single crystal X-ray diffraction analysis. The molecular structural analysis reveals that the NMe₂ group does not coordinate to the zirconium atom in all cases. Complexes 1-4 all have a pseudo-tetrahedral coordination environment in their solid state structures and adopt a three-legged piano stool geometry for the zirconium atoms with the amide N atom and the two Cl atoms being the three legs and the Cp* ring being the seat. Variable-temperature ¹H NMR experiments for all complexes 1-4 were performed to investigate the possible intramolecular interaction between the N atom in the NMe₂ group and the central zirconium atom in solution. Upon activation with Al ⁱBu₃ and Ph₃CB(C₆F₅) ₄, complexes 1-4 all exhibit moderate to good catalytic activity for ethylene polymerization and copolymerization with 1-hexene, producing linear polyethylene or poly(ethylene-co-1-hexene) with moderate molecular weight and reasonable 1-hexene incorporation. The Royal Society of Chemistry 2012.

Full text of DOI:10.1039/c2dt12105k

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PAPER
Synthesis, characterization, and catalytic properties of new half-sandwich
zirconium(IV) complexes†
Kefeng Liu,a,b Qiaolin Wu,a Xuyang Luo,a Wei Gaoa and Ying Mu*a
Received 4th November 2011, Accepted 16th December 2011
DOI: 10.1039/c2dt12105k
A number of new half-sandwich zirconium(IV) complexes bearing N,N-dimethylaniline-amido ligands
with the general formula Cp*ZrCl2[ortho-(RNCH2)(Me2N)C6H4] [R = 2,6-Me2C6H3 (1), 2,6-iPr2C6H3
(2), iPr (3), tBu (4)] were synthesized by the reaction of Cp*ZrCl3 with the corresponding ortho-(Me2N)
C6H4CH2NRLi. All new zirconium complexes were characterized by 1H and 13C NMR, elemental
analyses and single crystal X-ray diffraction analysis. The molecular structural analysis reveals that the
NMe2 group does not coordinate to the zirconium atom in all cases. Complexes 1–4 all have a pseudo-
tetrahedral coordination environment in their solid state structures and adopt a three-legged piano stool
geometry for the zirconium atoms with the amide N atom and the two Cl atoms being the three legs and
the Cp* ring being the seat. Variable-temperature 1H NMR experiments for all complexes 1–4 were
performed to investigate the possible intramolecular interaction between the N atom in the NMe2 group
and the central zirconium atom in solution. Upon activation with AliBu3 and Ph3CB(C6F5)4, complexes
1–4 all exhibit moderate to good catalytic activity for ethylene polymerization and copolymerization with
1-hexene, producing linear polyethylene or poly(ethylene-co-1-hexene) with moderate molecular weight
and reasonable 1-hexene incorporation.
copolymerization with α-olefins. In addition, some non-metallo-
Introduction
cene types of zirconium complexes were also synthesized and
studied as catalysts for olefin polymerization.21,22 Recently, we
Group 4 metallocene catalysts have attracted extensive interest in
academic and industrial institutes due to their unique properties
and advantages as olefin polymerization catalysts. Many research
efforts have been focused on the development of new homo-
geneous metallocene catalysts for producing high performance
polyolefin materials with tailored structures and properties.1–6
Zirconocene complexes have been widely explored as efficient
catalysts for ethylene7 and propylene4,8 polymerization and
copolymerization with higher α-olefins.9 Some nonbridged and
bridged zirconocene complexes have been found to exhibit
unique catalytic characteristics for stereospecific polymerization
of propylene.10–14 Since constrained geometry and nonbridged
monocyclopentadienyl titanium complexes have been known to
be good catalysts for ethylene copolymerization with α-olefins,15
some nonbridged monocyclopentadienyl zirconium complexes
reported a number of monocyclopentadienyl zirconium anilide
complexes Cp*ZrCl2[N(2,6-R1 C6H3)R2] which exhibit moder-
2
ate catalytic activity for ethylene copolymerization with 1-
hexene and produce copolymers with relatively high molecular
weight and reasonable 1-hexene incorporation.23 To further
modify the structure of the half-sandwich zirconium complexes,
we have synthesized a number of new monocyclopentadienyl
zirconium(IV) complexes bearing a N,N-dimethylaniline-amido
ligand with the general formula Cp*ZrCl2[ortho-(RNCH2)
i
(Me2N)C6H4] [R = 2,6-Me2C6H3 (1), 2,6-iPr2C6H3 (2), Pr (3),
tBu (4)], and investigated their catalytic properties for ethylene
polymerization. Herein we report the synthesis, characterization
and crystal structure of these half-sandwich zirconium com-
plexes, as well as their catalytic performance for ethylene
polymerization and copolymerization with 1-hexene.
bearing
a
benzamidinate,16 aryloxy,17 salicylaldiminato,18
β-diketiminate19 or imino-quinolinol20 ligand were also syn-
thesized and tested as catalysts for ethylene polymerization and
Results and discussion
aState Key Laboratory for Supramolecular Structure and Materials,
School of Chemistry, Jilin University, 2699 Qianjin Street, Changchun,
130012, People’s Republic of China. E-mail: ymu@jlu.edu.cn;
Fax: (+86)-431-85193421; Tel: (+86)-431-85168376
Synthesis and characterization of new compounds
The free ligands ortho-(Me2N)C6H4CH2NHR [R
= 2,6-
i
t
Me2C6H3 (HLa), 2,6-iPr2C6H3 (HLb), Pr (HLc), Bu (HLd)]
were synthesized according to a literature precedure.24 The new
zirconium(IV) complexes 1–4 were synthesized in Et2O by the
reaction of Cp*ZrCl3 with ortho-(Me2N)C6H4CH2NRLi which
were prepared in situ by treating the corresponding ortho-
bKey Laboratory of Biofuels, Qingdao Institute of Bioenergy and
Bioprocess Technology, Chinese Academy of Sciences, 189 Songling
road, Qingdao, 266101, People’s Republic of China
†CCDC reference numbers 851873–851876. For crystallographic data
in CIF or other electronic format see DOI: 10.1039/c2dt12105k
This journal is © The Royal Society of Chemistry 2012
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Scheme 1 The synthetic procedure of complexes 1–4.
(Me2N)C6H4CH2NHR with 1 equiv of nBuLi in n-hexane as
shown in Scheme 1. Analytical pure samples were obtained as
orange or pale-yellow crystalline solids in moderate yields
(65–80%) from a concentrated dichloromethane solution layered
with n-hexane at −30 °C. These new zirconium complexes 1–4
were all characterized by 1H and 13C NMR spectroscopy,
elemental analyses, and single-crystal X-ray diffraction analysis
Fig. 1 Variable-temperature 1H NMR spectra of complex 4 in CDCl3.
1
The H NMR spectra of complexes 1–4 show that the reson-
ances of the N–CH2 protons appear at 5.20, 4.97, 4.67, and
4.23 ppm, respectively, which are obviously shifted down-field
in comparison to the corresponding signals in the free ligands
(4.17, 4.07, 3.85 and 3.79 ppm, respectively). The resonance of
the N-CHMe2 proton (4.60 ppm) in complex 3 is also shifted
toward down-field compared with the corresponding signal in
the free ligand HLc (2.77 ppm). On the other hand, the reson-
ances for the methyl protons in the N-2,6-Me2C6H3 group in
complex 1 (1.77 ppm) and the methine protons in the
N-2,6-iPr2C6H3 group in complex 2 (3.26 ppm) are shifted to
up-field from those in the corresponding free ligands (2.30 and
3.41 ppm for HLa and HLb, respectively). The above obser-
vations are indicative of the formation of the Zr–N (amide) bond
in these complexes. The resonances of the NMe2 protons in com-
plexes 1 (2.03 ppm) and 2 (2.16 ppm) are obviously shifted up-
field from those in the corresponding free ligands (2.72 and
2.73 ppm for HLa and HLb, respectively), while the resonances
for the NMe2 protons in complexes 3 (2.69 ppm) and 4
(2.71 ppm) are almost the same as those in the free ligands HLc
(2.70 ppm) and HLd (2.71 ppm). The single crystal X-ray dif-
fraction analysis indicates that the NMe2 group does not coordi-
nate to the central zirconium atom in these complexes in the
Scheme 2 Possible dynamic processes which may be responsible for
the phenomena observed in the variable-temperature 1H NMR exper-
iments with complex 4.
1
observed for complexes 1–3 in similar variable-temperature H
NMR experiments. In addition, the resonance of the NMe2
protons shows little change with changing the temperature,
which is in contrast to the proposed process A. It is obvious that
the observed phenomena with complex 4 are more likely caused
i
solid state. For complex 2, the four methyl groups in the two Pr
substituents give two sets of doublets (0.71 and 1.23 ppm) in its
1H NMR spectrum and correspondingly two signals (24.8 and
25.6 ppm) in its 13C NMR spectrum due to the restricted rotation
of the 2,6-iPr2C6H3 group about the N–C bond.15p,23,25
t
by process B since the bulky Bu group on the amido N atom in
complex 4 would slow down the rotation rate of the amido group
about the Zr–N bond.
It was noticed that the N–CH2 protons in complex 4 show a
broad signal around 4.23 ppm at room temperature (293 K).
Variable-temperature H NMR experiments indicate that the res-
Crystal structures of complexes 1–4
1
onance gets sharp at 313 K, but splits into two signals with
decreasing the temperature and becomes a pair of doublets (3.42
and 4.89 ppm, JH-H = 16 Hz) at 233 K as shown in Fig. 1.
These phenomena may result from possible coordination of the
NMe2 group to the central Zr atom (process A) or restricted
rotation of the amido group about the Zr–N bond (process B) at
low temperature as illustrated in Scheme 2. If the NMe2 group
can coordinate to the central Zr atom at low temperatures, similar
results should be observed for complexes 1, 2 and 3. However,
no obvious change for the signals of the N–CH2 protons was
Molecular structures of complexes 1–4 were determined by
single crystal X-ray diffraction analysis. The ORTEP drawings
of their molecular structures together with data of selected bond
lengths and angles are given in Figs 2–5, respectively. Detailed
crystallography information can be found in the supplementary
information.† Crystallographic data indicate that complexes 1–3
crystallize in a monoclinic system with space group P21/C while
2
ˉ
complex 4 crystallizes in a triclinic system with space group P1.
Complexes 1–4 all have a pseudo-tetrahedral coordination
environment around their metal centers in the solid state
3462 | Dalton Trans., 2012, 41, 3461–3467
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Fig. 4 A perspective view of 3 with thermal ellipsoids drawn at the
30% probability level. Hydrogens are omitted for clarity. Selected bond
distances (Å) and angles (°): Cp*(cent)–Zr(1) = 2.198, Zr(1)–N(1) =
2.007(2), Zr(1)–Cl(1) = 2.4221(7), Zr(1)–Cl(2) = 2.4198(7), Cl(1)–Zr
(1)–Cl(2) = 104.80(3), N(1)–Zr(1)–Cl(1) = 109.05(6), N(1)–Zr(1)–Cl(2)
= 103.25(6), C(11)–N(1)–Zr(1) = 144.40(17), C(20)–N(1)–Zr(1) =
100.35(15), C(11)–N(1)–C(20) = 115.2(2), Cp*(cent)–Zr(1)–Cl(1) =
110.9, Cp*(cent)–Zr(1)–Cl(2) = 112.7, Cp*(cent)–Zr(1)–N (1) = 115.4.
Fig. 2 A perspective view of 1 with thermal ellipsoids drawn at the
30% probability level. Hydrogens are omitted for clarity. Selected bond
distances (Å) and angles (°): Cp*(cent)–Zr(1) = 2.202, Zr(1)–N(1) =
2.0177(18), Zr(1)–Cl(1) = 2.4155(6), Zr(1)–Cl(2) = 2.4149(6), Cl(1)–Zr
(1)–Cl(2) = 107.10(2), N(1)–Zr(1)–Cl(1) = 104.46(5), N(1)–Zr(1)–Cl(2)
= 106.13(5), C(11)–N(1)–Zr(1) = 143.53(15), C(19)–N(1)–Zr(1) =
101.65(13), C(11)–N(1)–C(19) = 113.87(17), Cp*(cent)–Zr(1)–Cl(1) =
110.8, Cp*(cent)–Zr(1)–Cl(2) = 111.2, Cp*(cent)–Zr(1)–N(1) = 116.6.
Fig. 5 A perspective view of 4 with thermal ellipsoids drawn at the
30% probability level. Hydrogens are omitted for clarity. Selected bond
distances (Å) and angles (°): Cp*(cent)–Zr(1) = 2.216, Zr(1)–N(1) =
2.0218(16), Zr(1)–Cl(1) = 2.4180(5), Zr(1)–Cl(2) = 2.4231(5), Cl(1)–Zr
(1)–Cl(2) = 100.18(2), N(1)–Zr(1)–Cl(1) = 102.42(5), N(1)–Zr(1)–Cl(2)
= 107.45(5), C(11)–N(1)–Zr(1) = 101.86(11), C(20)–N(1)–Zr(1) =
140.00(12), C(11)–N(1)–C(20) = 117.19(15), Cp*(cent)–Zr(1)–Cl(1) =
110.6, Cp*(cent)–Zr(1)–Cl(2) = 111.3, Cp*(cent)–Zr(1)–N(1) = 122.1.
longer than those in complexes 1 (2.0177 Å), 3 (2.007 Å) and 4
(2.0218 Å). The average Zr–Cl distances in complexes 1
(2.4152 Å), 2 (2.3985 Å), 3 (2.4210 Å) and 4 (2.4206 Å) are
close to those reported in complexes Cp*ZrCl2[N(2,6-R2C6H3)
Fig. 3 A perspective view of 2 with thermal ellipsoids drawn at the
30% probability level. Hydrogens are omitted for clarity. Selected bond
distances (Å) and angles (°): Cp*(cent)–Zr(1) = 2.220, Zr(1)–N(1) =
2.040(9), Zr(1)–Cl(1) = 2.387(4), Zr(1)–Cl(2) = 2.410(4), Cl(1)–Zr(1)–
Cl(2) = 105.30(17), N(1)–Zr(1)–Cl(1) = 103.9(3), N(1)–Zr(1)–Cl(2) =
103.0(3), C(11)–N(1)–Zr(1) = 124.9(7), C(23)–N(1)–Zr(1) = 121.1(7),
C(11)–N(1)–C(23) = 113.7(8), Cp*(cent)–Zr(1)–Cl(1) = 109.9, Cp*
(cent)–Zr(1)–Cl(2) = 109.2, Cp*(cent)–Zr(1)–N(1) = 123.9.
i
(CH3)] (R = Pr, 2.414 Å; R = Me, 2.403 Å).23 The Cp*(cent)–
Zr distances in complexes 1 (2.202 Å), 2 (2.220 Å), 3 (2.198 Å)
and 4 (2.216 Å) are close to those reported in complexes
i
Cp*ZrCl2[N(2,6-R2C6H3)(CH3)] (R = Pr, 2.197 Å; R = Me,
2.214 Å).23 The Cl(1)–Zr(1)–Cl(2) angles in these complexes
decrease in the order of 1 (107.10°) > 2(105.30°) > 3 (104.80) >
4 (100.18°) with the change in the steric bulk of the N–R group.
The sum of the bond angles around the N atom is close to 360°
for all complexes, indicating the N atom forming bonds with sp2
orbitals in these complexes. The Cp*(cent)–Zr(1)–N(1) angles in
complex 2 (123.9°) and complex 4 (122.1°) are larger than those
in complexes 1 (116.6°) and 3 (115.4°), which is obviously
caused by the bulky N–R group in the former complexes.
structures and adopt a three-legged piano stool geometry with
the N(1) atom and the two Cl atoms being the three legs and the
Cp* ring being the seat. As seen in previously reported com-
plexes Cp*MCl2[N(2,6-R2C6H3)(CH3)] (M = Ti, Zr; R = Me,
iPr),15p,23 the aryl ring directly bonded to the N(1) atom in
complex 1 is nearly parallel to the Cp* ring with an angle of
11.5°. The Zr–N(1) distance in complex 2 (2.040 Å) is slightly
This journal is © The Royal Society of Chemistry 2012
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Table 1 A summary of ethylene polymerization catalyzed by 1–4/AliBu3/Ph3CB(C6F5)4 systemsa
c
Run
Catalyst
T/°C
Al/Zr mol ratio
Yield (g)
Activityb
Mwc ×10−4
Mw/Mn
Tmd(°C)
1
2
3
4
5
6
7
8
1
2
3
4
4
4
4
4
80
80
80
60
80
80
100
80
350
350
350
250
250
350
350
450
0.971
0.742
1.032
0.404
0.772
1.135
0.845
0.880
1942
1482
2064
808
1544
2270
1690
1760
12.4
8.69
12.2
7.91
7.60
6.79
3.45
3.60
2.09
2.45
2.24
2.26
2.04
2.25
2.10
2.22
138.3
137.9
139.3
139.8
139.7
137.8
138.6
137.9
a Polymerization conditions: toluene 70 mL, catalyst 2 μmol Zr, B/Zr molar ratio 1.5, time 15 min, ethylene pressure 5 bar. b Activity in g PE (mmol
Zr)−1 h−1 c Determined by GPC in o-dicholobenzene vs. polystyrene standard. d Determined by DSC at a heating rate of 10 °C min−1 and the data
.
from the second scan are used.
Table 2 A summary of ethylene/1-hexene copolymerization catalyzed by 1–4/AliBu3/Ph3CB(C6F5)4 systemsa
d
Run
Catalyst
Yield (g)
Activityb
1-hexene contentc(mol%)
Mwd x 10−4
Mw/Mn
Tme(°C)
1
2
3
4
1
2
3
4
0.847
0.825
1.004
1.155
1694
1650
2008
2310
3.22
3.00
0.55
3.76
11.4
7.69
10.2
5.81
3.51
3.34
3.68
3.12
128.4
128.9
129.2
127.2
a Polymerization conditions: toluene + 1-hexene total 70 mL, catalyst 2 μmol Zr, Al/Zr molar ratio 350, B/Zr molar ratio 1.5, time 15 min, temperature
80 °C, ethylene pressure 5 bar. b Activity in g polymer (mmol Zr)−1 h−1 c Calculated based on 13C NMR spectra. d Determined by GPC in
o-dicholobenzene vs. polystyrene standard. e Determined by DSC at a heating rate of 10 °C min−1 and the data from the second scan are used.
.
Polymerization reaction
ethylene homopolymerization reaction: 4 > 3 > 1 > 2. The
obtained poly(ethylene-co-1-hexene)s were analyzed by 13C
NMR and GPC. Based on the 13C NMR analysis,26 the comono-
mer content in the poly(ethylene-co-1-hexene)s was calculated
and the data are listed in Table 2. It can be seen from these
results that the comonomer incorporation ability of these catalyst
systems is evidently dependent on the structure of the catalyst.
The comonomer content of the copolymers obtained with com-
plexes 1, 2 and 4 is obviously higher than that of the copolymer
produced by complex 3 under similar conditions. It has been
known that the comonomer incorporation ability of a catalyst
system can be affected by several factors.27 In the present work,
the steric bulk of the amido ligand seems to be a major issue. A
large steric hindrance from the ligands would weaken the inter-
action between the cationic catalyst and the anionic cocatalyst
species, which would favor the coordination of the comonomer
to the metal center of the catalyst. GPC analysis on the copoly-
mers reveals that the poly(ethylene-co-1-hexene)s produced by
Ethylene polymerization using complexes 1–4 as precatalysts
under different conditions was studied in detail and the results
are summarized in Table 1. Upon activation with AliBu3 and
Ph3CB(C6F5)4, complexes 1–4 all exhibit good catalytic activity
for ethylene polymerization. Under similar conditions, the cata-
lytic activity decreases in the order of 4 > 3 > 1 > 2, indicating
that the catalytic activity of these zirconium complexes is
remarkably influenced by the nature of the substituents on the
amido ligands. As observed in other zirconocene catalyst
systems, the catalytic activity of these zirconium catalyst systems
is dependent on the Al/Zr molar ratio. The maximal catalytic
activities were obtained at Al/Zr molar ratios of about 350. The
catalytic activity of these catalyst systems was also examined at
different polymerization temperatures and the maximal values
were observed around 80 °C. The molecular weight of the
obtained polyethylenes by these catalysts is moderate (Mw
=
3.6–13.0 × 104 g mol−1). As expected, the molecular weight of
the polyethylenes decreases with the increase in the Al/Zr molar
ratio and the elevation in polymerization temperature, due to the
acceleration of the chain transfer reaction to alkylaluminum in
the former case and the decrease in the concentration of ethylene
in toluene with increasing the polymerization temperature in the
latter case. In addition, the melting temperatures of the obtained
polyethylenes are in the range of 136–140 °C, being typical for
linear polyethylene
these catalysts possess moderate molecular weight (Mw
=
6.8–12.0 × 104 g mol−1). The molecular weight distribution is
basically unimodal and narrow, being characteristic for metallo-
cene polyolefins. In addition, the melting temperatures of the
resultant copolymers are in the range of 127–130 °C.
Conclusions
Copolymerization of ethylene with 1-hexene with complexes
1–4 as precatalysts was also explored and the copolymerization
results are summarized in Table 2. The catalytic activity of these
catalysts for the ethylene/1-hexene copolymerization under
similar conditions changes in the same order as observed in the
A number of new half-sandwich zirconium (IV) complexes 1–4
of the type Cp*ZrCl2[ortho-(RNCH2)(Me2N)C6H4] were syn-
thesized by the reaction of Cp*ZrCl3 with ortho-C6H4(NMe2)
CH2NRLi in moderate yields. All new complexes were charac-
terized by 1H and 13C NMR, elemental analyses, and single
3464 | Dalton Trans., 2012, 41, 3461–3467
This journal is © The Royal Society of Chemistry 2012

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crystal X-ray diffraction analysis. The molecular structural analy-
sis reveals that the NMe2 group does not coordinate to the zirco-
nium atom in all cases. Complexes 1–4 all have a pseudo-
tetrahedral coordination environment in their solid state struc-
tures and adopt a three-legged piano stool geometry for the zir-
conium atoms with the amide N atom and the two Cl atoms
being the three legs and the Cp* ring being the seat. Upon acti-
vation with AliBu3/Ph3CB(C6F5)4, complexes 1–4 all exhibit
good catalytic activity for ethylene polymerization and ethylene/
1-hexene copolymerization, producing moderate molecular
weight polyethylenes and relatively high molecular weight poly
(ethylene-co-1-hexene)s with reasonable 1-hexene incorporation.
organic phase was separated, dried over anhydrous MgSO4,
filtered and concentrated by distillation under reduced pressure
to give the final product HLc (2.44 g, 12.7 mmol, 89%) as an
1
orange oil. H NMR (CDCl3, 300 MHz, 298 K): δ 7.29 (d, 1 H,
3
3
ArH, JH-H = 7.5 Hz), 7.21 (t, 1 H, ArH, JH-H = 8.1 Hz), 7.10
3
3
(d, 1 H, ArH, JH-H = 8.1 Hz), 7.02 (t, 1 H, ArH, JH-H = 7.8
Hz), 3.85 (s, 2 H, NCH2), 2.78 (sept, 1 H, CHMe2, JH-H = 6.3
3
Hz), 2.70(s, 6 H, N(CH3)2), 1.93 (br, 1 H, NH), 1.08 (d, 6 H,
3
CHMe2, JH-H = 6.0 Hz) ppm. 13C NMR(CDCl3, 75 MHz,
298 K): δ 152.6, 135.0, 129.7, 127.4, 123.2, 119.3, 48.0, 47.9,
44.9, 22.9 ppm.
Synthesis of ortho-C6H4NMe2CH2NHtBu (HLd). HLd was
synthesized using a procedure identical to that for HLc with
ortho-C6H4(NMe)2CHO (2.12 g, 14.2 mmol) and tBuNH2
(1.04 g, 14.2 mmol) as the starting materials. The Schiff base
product ortho-C6H4NMe2CHvNtBu (2.67 g, 13.1 mmol) was
obtained in a yield of 92%.1H NMR (CDCl3, 300 MHz, 298 K):
Experimental section
General comments
All manipulations involving air and moisture sensitive com-
pounds were carried out under nitrogen atmosphere (ultra-high
purity) using either standard Schlenk techniques or glove box
techniques. Toluene, diethyl ether, THF, and n-hexane were dis-
tilled under nitrogen in the presence of sodium and benzophe-
none. CH2Cl2 and 1-hexene were purified by distilling over
calcium hydride before use. Cp*ZrCl3,28 HLa, HLb, ortho-
3
δ 8.59 (s, 1 H, CH = N), 7.82 (d, 1 H, ArH, JH-H = 7.8 Hz),
3
7.32 (t, 1 H, ArH, JH-H = 7.8 Hz), 6.05–7.08 (m, 2 H, ArH),
t
2.76 (s, 6 H, N(CH3)2), 1.32 (s, 9 H, Bu) ppm. The final
product HLd (2.50 g, 12.1 mmol, 93%) was obtained as an
1
orange oil. H NMR (CDCl3, 300 MHz, 298 K): δ 6.98–7.36
(m, 4 H, ArH), 3.79 (s, 2 H, NCH2), 2.71(s, 6 H, N(CH3)2), 1.18
(s, 9 H, tBu) ppm. 13C NMR (CDCl3, 75 MHz, 298 K): δ 152.4,
135.6, 130.0, 127.3, 123.3, 119.1, 50.3, 44.9, 43.4., 29.0 ppm.
C6H4(NMe)2CHO24 and Ph3CB(C6F5)4 were prepared accord-
29
ing to literature procedures. Polymerization grade ethylene was
further purified by passage through columns of 5 Å molecular
sieves and MnO. AliBu3, nBuLi, and ZrCl4 were purchased from
Aldrich or Acros. 1H and 13C NMR spectra were measured using
a Varian Mercury-300 NMR spectrometer. 13C NMR spectra of
the copolymers were recorded on a Varian Unity-400 NMR
spectrometer at 125 °C with o-C6D4Cl2 as the solvent. Molecular
weight and molecular weight distribution of the polymer
samples were measured on a PL-GPC 220 at 140 °C with 1,2,4-
trichlobenzene as the solvent. The melting points of the poly-
mers were measured by differential scanning calorimetry (DSC)
on a NETZSCH DSC 204 at a heating/cooling rate of 10 °C
min−1 from 35 to 180 °C and the data from the second heating
scan were used.
Lithium salt of ligand ortho-C6H4NMe2CH2NH(2,6-Me2-
C6H3) (LiLa). A solution of n-BuLi (4.8 mL, 1.6 M in n-
hexane, 7.7 mmol) was added slowly to solution of (ortho-
C6H4NMe2CH2)(2,6-Me2C6H3)NH (1.92 g, 7.55 mmol) in
hexane at −30 °C, and the reaction mixture was allowed to warm
to room temperature and stirred over night. The resultant precipi-
tates were collected on a frit, washed with n-hexane, and dried
under vacuum to give LiLa in a yield of 83% (1.63 g,
6.27 mmol).
Lithium salts LiLb, LiLc, and LiLd were prepared in the
same way as described above for LiLa
Synthesis of complex 1. LiLa (0.523 g, 2.01 mmol) was
added to a suspension of Cp*ZrCl3 (0.669 g, 2.01 mmol) in
40 ml of diethyl ether at −30 °C. The reaction mixture was
allowed to warm to room temperature and stirred for 15 h. After
removal of the solvent, the crude product was extracted with
CH2Cl2. Recrystallization from CH2Cl2/n-hexane gave pure
complex 1 as orange crystals (0.859 g, 1.57 mmol, 78%). Anal.
Calcd. for C27H36Cl2N2Zr (550.70): C, 58.9; H, 6.59; N, 5.09.
Synthesis of ortho-C6H4NMe2CH2NHiPr (HLc). ortho-
i
C6H4(NMe)2CHO (2.24 g, 15.0 mmol) and PrNH2 (0.887 g,
15.0 mmol) were dissolved in 20 mL of methanol. To the
mixture was added a catalytic amount of formic acid. The reac-
tion mixture was stirred and heated to reflux for 8 h. The solvent
was removed under reduced pressure to leave the Schiff base
product ortho-C6H4NMe2CHvNiPr as an orange oil (2.71 g,
1
Found: C, 58.5; H, 6.48; N, 5.06. H NMR (CDCl3, 300 MHz,
1
298 K): δ 8.03 (d, 1 H, ArH, 3JH-H = 7.5 Hz), 7.14 (t, 1 H, ArH,
14.3 mmol, 95%). H NMR (CDCl3, 300 MHz, 298 K): δ 8.61
3
3
3JH-H = 7.5 Hz), 6.98 (t, 1 H, ArH, JH-H = 7.5 Hz), 6.76–6.91
(s, 1 H, CH = N), 7.84 (d, 1 H, ArH, JH-H = 7.2 Hz), 7.33 (t, 1
3
3
H, ArH, JH-H = 7.5 Hz), 7.03 (d, 1 H, ArH, JH-H = 7.5 Hz),
(m, 4 H, ArH), 5.21 (s, 2 H, NCH2), 2.04 (s, 6 H, N(CH3)2),
1.88 (s, 15 H, CpMe5), 1.78 (s, 6 H, PhMe2) ppm.13C NMR
(CDCl3, 75 MHz, 298 K): δ 154.7, 145.6, 134.5, 133.6, 132.6,
128.6, 127.4, 125.0, 124.6, 124.0, 120.2, 45.3, 44.5, 18.4,
11.3 ppm.
3
7.02 (t, 1 H, ArH, JH-H = 7.2 Hz), 3.58 (sept, 1 H, CHMe2,
3JH-H = 6.3 Hz), 2.76 (s, 6 H, N(CH3)2), 1.27 (d, 6 H, CHMe2,
3JH-H = 6.3 Hz) ppm. The Schiff base compound was dissolved
in THF (50 mL). To the solution was slowly added 0.542 g of
LiAlH4 (14.3 mmol) at 0 °C. The mixture was allowed to warm
to room temperature and stirred over night. The reaction was
quenched with 20 mL of water and the insoluble solids were
filtered off. Further 40 mL of H2O was added to the filtrate and
the product was extracted with 50 mL of diethyl ether. The
Synthesis of complex 2. Complex 2 was synthesized using a
procedure identical to that for complex 1 with LiLb (0.493 g,
1.56 mmol) and Cp*ZrCl3 (0.519 g, 1.56 mmol) as the starting
materials. 0.637 g pure product (1.05 mmol, 67%) was obtained
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Table 3 Crystallographic parameters, data collections, and structure refinements for complexes 1–4
Complexes
1
2
3
4
Formula
Fw
C27H36Cl2N2Zr
550.70
C31H44Cl2N2Zr
606.80
C22H34Cl2N2Zr
488.63
C23H36Cl2N2Zr
502.66
Wavelength(Å)
Crystal system
Space group
0.71073
Monoclinic
P21/c
0.71073
Monoclinic
P21/c
0.71073
Monoclinic
P21/c
0.71073
Triclinic
ˉ
P1
a/Å
b/Å
c/Å
α (°)
8.5545(5)
13.5020(8)
23.1132(14)
90
93.1080(10)
90
20.13(2)
8.833(10)
19.65(2)
90
116.601(15)
90
10.2590(6)
14.6848(8)
16.2009(9)
90
100.5010(10)
90
8.0251(6)
11.4954(8)
13.8983(10)
105.0150(10)
94.0820(10)
98.1910(10)
1217.87(15)
2
β (°)
γ (°)
V/Å3
2665.7(3)
4
3125(6)
4
2399.8(2)
4
Z
F(000)
1144
1.372
0.630
1272
1.290
0.544
1016
1.352
0.690
524
1.371
0.682
Dc/g cm−3
μ/mm−1
θ range (deg)
No. of reflns
No. of indep. reflns
R(int)
Data/restraints/parameters
GOF
1.75–26.03
16223
5247
0.0311
5247/2/306
1.030
2.07–25.25
27146
5539
0.1307
5539/12/337
1.131
1.89–25.04
13582
4227
0.0290
4227/1/257
1.048
1.86–26.03
7365
4682
0.0113
4682/0/263
1.037
R1, Rw [I > 2σ(I)]
R1, Rw (all data)
Max(min) diff peak/e Å−3
0.0325, 0.0737
0.0413, 0.0782
0.370, −0.240
0.1051, 0.2428
0.1605, 0.2709
0.987, −1.436
0.0320, 0.0730
0.0432, 0.0775
0.477, −0.207
0.0260, 0.0658
0.028, 0.0675
0.338, −0.311
as orange crystals. Anal. Calcd. for C31H44Cl2N2Zr(606.80): C,
61.4; H, 7.31; N, 4.62. Found: C, 61.1; H, 7.38; N, 4.58. H
152.7, 131.0, 130.8, 127.7, 124.5, 122.5, 118.8, 58.1, 45.2, 35.6,
32.0, 12.2 ppm.
1
NMR (CDCl3, 300 MHz, 298 K): δ 6.98–7.36 (m, 7 H, ArH),
3
4.97 (s, 2 H, NCH2), 3.26 (sept, 2 H, CH(CH3)2, JH-H = 6.6
X-ray structural analysis of complexes 1–4
Hz), 2.18 (s, 15 H, CpMe5), 2.16 (s, 6 H, N(CH3)2), 1.23 (d, 6
H, CH(CH3)2, 3JH-H = 6.6 Hz), 0.71 (d, 6 H, CH(CH3)2, 3JH-H
=
Single crystals of complexes 1–4 suitable for X-ray crystal struc-
tural analysis were obtained from CH2Cl2/n-hexane (v/v =
1–2 : 10) mixed solvent system. The data were collected on a
6.6 Hz) ppm. 13C NMR (CDCl3, 75 MHz, 298 K): δ 153.9,
146.9, 134.7, 131.5, 128.1, 127.1, 125.4, 124.6, 124.4, 121.5,
53.6, 45.7, 27.9, 25.6, 24.8, 12.2 ppm.
Rigaku RAXIS-RAPID diffractometer with Mo-Kα (λ
=
0.71073 Å) radiation. All structures were solved by direct
method30 and refined by full-matrix least-squares on F2. All
non-hydrogen atoms were refined anisotropically, and the hydro-
gen atoms were included in idealized positions. All calculations
were performed using the SHELXTL crystallographic software
packages.31 Details of the crystallographic parameters, data col-
lections, and structure refinements are summarized in Table 3.
Synthesis of complex 3. Complex 3 was synthesized using a
procedure identical to that for complex 1 with LiLc (0.369 g,
1.86 mmol) and Cp*ZrCl3 (0.619 g, 1.86 mmol) as the starting
materials. 0.635 g pure product (1.30 mmol, 70%) was obtained
as orange crystals. Anal. Calcd. for C22H34Cl2N2Zr(488.63): C,
1
54.1; H, 7.01; N, 5.73. Found: C, 53.7; H, 7.08; N, 5.69. H
NMR (CDCl3, 300 MHz, 298 K): δ 6.98–7.32 (m, 4 H, ArH),
4.67 (s, 2H, NCH2), 4.60 (sept, 1 H, CH(CH3)2,3JH-H = 6.0 Hz),
2.69 (s, 6 H, N(CH3)2), 2.07 (s, 15 H, CpMe5), 1.07 (d, 6 H, CH
Polymerization reactions
3
(CH3)2, JH-H = 6.0 Hz) ppm. 13C NMR (CDCl3, 75 MHz,
The ethylene polymerization experiments were carried out as
follows: a dry 250 mL steel autoclave with a magnetic stirrer
was charged with 60 mL of toluene, thermostated at a desired
temperature and saturated with ethylene (1.0 atm). The polymer-
ization reaction was started by addition of a mixture of catalyst
and AliBu3 in toluene (5 mL) and a solution of Ph3CB(C6F5)4 in
toluene (5 mL) at the same time. The vessel was pressurized to
5 atm with ethylene immediately and the pressure was kept by
continuous feeding of ethylene. The reaction mixture was stirred
at the desired temperature for 15 min. The polymerization was
then quenched by injecting acidified methanol [HCl (3 M)/metha-
nol = 1 : 1], and the polymer was collected by filtration, washed
with water, methanol, and dried at 60 °C in vacuo to a constant
weight. For the ethylene/1-hexene copolymerization exper-
iments, appropriate amounts of 1-hexene were added in toluene.
298 K): δ 135.9, 128.2, 127.1, 124.3, 123.0, 118.9, 114.6, 46.7,
46.1, 44.9, 22.0, 11.7 ppm.
Synthesis of complex 4. Complex 4 was synthesized using a
procedure identical to that for complex 1 with LiLd (0.385 g,
1.81 mmol) and Cp*ZrCl3 (0.602 g, 1.81 mmol) as the starting
materials. 0.646 g pure product (1.29 mmol, 71%) was obtained
as pale yellow crystals. Anal. Calcd. for C23H36Cl2N2Zr
(502.66): C, 55.0; H, 7.22; N, 5.57. Found: C, 54.6; H, 7.26; N,
1
5.59. H NMR (CDCl3, 300 MHz, 298 K): δ 7.78 (d, 1 H, ArH,
3
3JH-H = 7.5 Hz), 7.19 (t, 1 H, ArH, JH-H = 7.2 Hz), 7.09 (d, 1
H, ArH, 3JH-H = 7.5 Hz), 7.02(t, 1 H, ArH, 3JH-H = 7.2 Hz), 4.23
(s, 2 H, NCH2), 2.71(s, 6 H, N(CH3)2), 2.18 (s, 15 H, CpMe5),
t
1.05 (s, 9 H, Bu) ppm. 13C NMR (CDCl3, 75 MHz, 298 K): δ
3466 | Dalton Trans., 2012, 41, 3461–3467
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Organometallics, 1996, 15, 1572; (i) A. L. MacKnight, M. A. Masood,
R. M. Waymouth and D. A. Straus, Organometallics, 1997, 16, 2879;
( j) K. Nomura, N. Naga, M. Miki, K. Yanagi and A. Imai, Organometal-
lics, 1998, 17, 2152; (k) K. Nomura, K. Oya, T. Komatsu and
Y. Imanishi, Macromolecules, 2000, 33, 3187; (l) K. Nomura, K. Itagaki
and M. Fujiki, Macromolecules, 2005, 38, 2053; (m) K. Nomura, J. Liu,
M. Fujiki and A. Takemoto, J. Am. Chem. Soc., 2007, 129, 14170;
(n) K. Nomura and K. Fujii, Macromolecules, 2003, 36, 2633;
(o) P. J. Sinnema, T. P. Spaniol and J. Okuda, J. Organomet. Chem.,
2000, 598, 179; (p) K. Liu, Q. Wu, W. Gao, Y. Mu and L. Ye,
Eur. J. Inorg. Chem., 2011, 1901.
Acknowledgements
This work was supported by the National Natural Science Foun-
dation of China (Nos. 21074043 and 51173061).
Notes and references
1 G. W. Coates and R. M. Waymouth, Science, 1995, 267, 217.
2 A. L. McKnight and R. M. Waymouth, Chem. Rev., 1998, 98, 2587.
3 H. G. Alt and A. Köppl, Chem. Rev., 2000, 100, 1205.
4 H. H. Brintzinger, D. Fischer, R. Mülhaupt, B. Rieger and R.
M. Waymouth, Angew. Chem., Int. Ed. Engl., 1995, 34, 1143.
5 R. J. Long, V. C. Gibson and A. J. P. White, Organometallics, 2008, 27,
235.
6 (a) K. Nomura, J. Liu, S. Padmanabhan and B. Kitiyanan, J. Mol. Catal.
A: Chem., 2007, 267, 1; (b) K. Nomura,, Dalton Trans., 2009 (41), 8811.
7 L. Iaao, L. Caporaso, G. Senatore and L. Oliva, Macromolecules, 1999,
32, 6913.
8 (a) Y. Obora, C. L. Stern, T. J. Marks and P. N. Nickias, Organometallics,
1997, 16, 2503; (b) N. Schneider, M. E. Huttenloch, U. Stehling,
R. Kirsten, F. Schaper and H. H. Brintzinger, Organometallics, 1997, 16,
3413; (c) A. J. Puranen, M. Klinga, M. Leskelä and T. Repo, Organo-
metallics, 2004, 23, 3759.
9 (a) Y.-X. Chen and T. J. Marks, Organometallics, 1997, 16, 3649;
(b) R. Goretzki and G. Fink, Macromol. Rapid Commun., 1998, 19, 511;
(c) H. Hagihara, K. Tsuchihara, K. Takeuchi, M. Murata, H. Ozaki and
T. Shiono, J. Polym. Sci., Part A: Polym. Chem., 2004, 42, 52.
10 (a) E. Hauptman, R. M. Waymouth and J. Ziller, J. Am. Chem. Soc.,
1995, 117, 11586; (b) S. Lin and R. M. Waymouth, Acc. Chem. Res.,
2002, 35, 765.
11 (a) Y. X. Chen, M. D. Rausch and J. C. W. Chien, Macromolecules,
1995, 28, 5399; (b) D. M. Shin, V. H. Pham, K. W. La, I. K. Song and
J. S. Chung, Res. Chem. Intermed., 2008, 34, 687.
12 (a) L. Izzo, M. Napoli and L. Oliva, Macromolecules, 2003, 36, 9340;
(b) L. Caporaso, L. Izzo, I. Sisti and L. liva, Macromolecules, 2002, 35,
4866.
13 (a) R. Quijada, J. L. Guevara, G. B. Galland, F. M. Rabagliati and J.
M. Lopez-Majada, Polymer, 2005, 46, 1567; (b) J. W. Zhang, B.-G. Li,
H. Fan and S. P. Zhu, J. Polym. Sci., Part A: Polym. Chem., 2007, 45,
3562; (c) H. Lasarov, K. Mönkkönen and T. T. Pakkanen, Macromol.
Chem. Phys., 1998, 199, 1939.
16 (a) R. Gòmez, R. Duchateau, A. N. Chernega, J. H. Teuben,
F. T. Edelmann and M. L. H. Green, J. Organomet. Chem., 1995, 491,
153.
17 (a) A. Antiñolo, F. Carrillo-Hermosilla, A. Corrochano, J. Fernández-
Baeza, A. Lara-Sanchez, M. R. Ribeiro, M. Lanfranchi, A. Otero,
M. A. Pellinghelli, M. F. Portela and J. V. Santos, Organometallics, 2000,
19, 2837; (b) J.-Y. Liu, S. R. Liu, B. X Li, Y.-G. Li and Y.-S. Li, Organo-
metallics, 2011, 30, 4052.
18 (a) R. K. J. Bott, D. L. Hughes, M. Schormann, M. Bochmann and S.
J. Lancaster, J. Organomet. Chem., 2003, 665, 135; (b) W. Huang,
X. Sun, H. Ma and J. Huang, Inorg. Chim. Acta., 2010, 363, 2009.
19 (a) A. R. Cabrera, Y. Schneider, M. Valderrama, R. Fröhlich, G. Kehr,
G. Erker and R. S. Rojas, Organometallics, 2010, 29, 6104;
(b) R. Vallmerhaus, M. Rahim, R. Tomaszewski, S. Xin, N. J. Taylor and
S. Collins, Organometallics, 2000, 19, 2161.
20 P. Hu, F. Wang and G.-X. Jin, Organometallics, 2011, 30, 1008.
21 (a) S. Matsui, M. Mitani, J. Saito, Y. Tohi, H. Makio, N. Matsukawa,
Y. Takagi, K. Tsuru, M. Nitabaru, T. Nakano, H. Tanaka, N. Kashiwa and
T. Fujita, J. Am. Chem. Soc., 2001, 123, 6847; (b) T. Matsugi and
T. Fujita, Chem. Soc. Rev., 2008, 37, 1264.
22 (a) S.-D. Bai, H. Tong, J. Guo, M.-S. Zhou, D.-S. Liu and S.-F. Yuan,
Polyhedron, 2010, 29, 262; (b) M.-S. Zhou, S. Zhang, H. Tong,
W.-H. Sun and D.-S. Liu, Inorg. Chem. Commun., 2007, 10, 1262;
(c) S.-F. Yuan, S.-D. Bai, D.-S. Liu and W.-H. Sun, Organometallics,
2010, 29, 2132; (d) S.-F. Yuan, X. Wei, H. Tong, L,. Zhang, D.-S. Liu
and W.-H. Sun, Organometallics, 2010, 29, 2085.
23 K. Liu, Q Wu, W Gao and Y Mu, Dalton Trans., 2011, 40, 4715.
24 A. Gao, Y. Mu, J. Zhang and W. Yao, Eur. J. Inorg. Chem., 2009, 3613.
25 (a) P. G. Hayes, G. C. Welch, D. J. H. Emslie, C. L. Noack, W. E. Piers
and M. Parvez, Organometallics, 2003, 22, 1577; (b) J. D. Scollard, D.
H. McConville, N. C. Payne and J. J. Vittal, Macromolecules, 1996, 29,
5241.
14 (a) L. Resconi, R. L. Jones, A. L. Rheingold and G. P. A. Yap, Organo-
metallics, 1996, 15, 998; (b) L. Resconi, R. L. Jones, E. Albizzati,
I. Camurati, F. Piemontesi, F. Guglielmi and G. Balbontin, Polym. Prepr.
(Am. Chem. Soc. Div. Polym. Chem.), 1994, 35, 663.
26 J. C. Randall, J. Macromol. Sci. Rev. Macromol. Chem. Phys., 1989, C29
(2&3), 201.
27 (a) K. Nomura, K. Fujita and M. Fujiki, J. Mol. Catal. A: chem., 2004,
220, 133; (b) D. J. Cho, C. J. Wu, S. S, W.-S. Han, S. O. Kang and B.
Y. Lee, Organometallics, 2006, 25, 2133.
28 P. T. Wolczanski and J. E. Bercaw, Organometallics, 1982, 1, 793.
29 (a) A. G. Massey and A. J. Park, J. Organomet. Chem., 1964, 2, 245;
(b) A. G. Massey and A. J. Park, J. Organomet. Chem., 1966, 5, 218;
(c) J. C. W. Chien, W. M. Tsai and M. D. Rasch, J. Am. Chem. Soc.,
1991, 113, 8570.
15 (a) J. A. M. Canich, G. G. Hlatky, H. W. Turner, US Pat., 542236, 1990;
(b) J. A. M. Canich, US Pat., 5026789, 1991; (c) J. A. M. Canich, Eur.
Pat. Appl., 420436, 1991; (d) J. C. Stevens, F. J. Timmers, D. R. Wilson,
G. F. Schmidt, P. N. Nickias, R. K. Rosen, G. W. Knight, S. -Y. Lai,
Eur. Pat. Appl., 416815, 1991; (e) J. C. Stevens, D. R. Nelthamer,
Eur. Pat. Appl., 418022, 1991; (f) D. D. Devore, F. J. Timmers,
D. L. Hasha, R. K. Rosen, T. J. Maks, P. A. Deck and C. L. Stern, Orga-
nometallics, 1995, 14, 3132; (g) K. E. du Plooy, U. Moll, S. Wocadlo,
W. Massa and J. Okuda, Organometallics, 1995, 14, 3129;
(h) D. W. Carpenetti, L. Kloppenburg, J. T. Kupec and J. L. Petersen,
30 SMART and SAINT software packages, Siemens Analytical X-ray instru-
ments, Inc., Madison, WI, 1996
31 G. M. Sheldrick, SHELXTL, Version 5.1, Siemens Industrial Automation,
Inc., 1997
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