Zirconium complexes with pendant aryloxy groups attached to the metallocene moiety by ethyl or hexyl spacers

Article abstract of DOI:10.1016/j.poly.2013.08.066

Four zirconium complexes with pendant aryloxy groups attached to the metallocene moiety by ethyl or hexyl spacers have been synthesized and characterized by spectroscopic methods and HR-MS or elemental analysis. The solid state structure of bis[{6-(2,6-dimethylphenoxy)hexyl}cyclopentadienyl] zirconium dichloride was determined by single crystal X-ray diffraction. The prepared complexes were tested as catalyst precursors in the polymerization of ethylene upon activation with MAO. The results showed a marked effect of the spacer length on the catalytic activity, while only a minor effect of the substitution on the aryl group, which affected its steric properties.

Full text of DOI:10.1016/j.poly.2013.08.066

Polyhedron 67 (2014) 205–212
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Zirconium complexes with pendant aryloxy groups attached
to the metallocene moiety by ethyl or hexyl spacers
Won Seok Cho a,1, So Han Kim a,1, Da Jung Kim a, Sang-deok Mun a, Ran Kim a, Min Jeong Go b,
Myung Hwan Park c, Min Kim a, Junseong Lee b, , Youngjo Kim a,
⇑
⇑
a Department of Chemistry, Chungbuk National University, 52 Naesudong-ro, Heungdeok-gu, Cheongju, Chungbuk 361-763, Republic of Korea
b Department of Chemistry, Chonnam National University, Gwangju 500-757, Republic of Korea
c Department of Chemistry Education, Chungbuk National University, 52 Naesudong-ro, Heungdeok-gu, Cheongju, Chungbuk 361-763, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 13 July 2013
Accepted 30 August 2013
Available online 11 September 2013
Four zirconium complexes with pendant aryloxy groups attached to the metallocene moiety by ethyl or
hexyl spacers have been synthesized and characterized by spectroscopic methods and HR-MS or elemen-
tal analysis. The solid state structure of bis[{6-(2,6-dimethylphenoxy)hexyl}cyclopentadienyl]zirconium
dichloride was determined by single crystal X-ray diffraction. The prepared complexes were tested as cat-
alyst precursors in the polymerization of ethylene upon activation with MAO. The results showed a
marked effect of the spacer length on the catalytic activity, while only a minor effect of the substitution
on the aryl group, which affected its steric properties.
Keywords:
Zirconocene
Metallocene
Aryloxy-functionalized cyclopentadienyl
X-ray crystal structure
Polyethylene
Ó 2013 Elsevier Ltd. All rights reserved.
Catalyst
1. Introduction
and Zr) [16], (R-MeO(CH2)nCHMeCp)2MCl2 (n = 0, 1; M = Ti and
Zr) [17], (2-MeOPhCR2Cp)2TiCl2 (R2 = Me2, MeEt, and Et2) [18],
Since catalysts for ethylene and propylene polymerization
were pioneered by Ziegler and Natta in the 1950s [1,2], com-
plexes of group IV elements with ligands such as mono-cyclo-
pentadienyl (Cp), bis-Cp, and ansa-type bridged Cp have been
tested to catalyze olefin polymerization [3–6]. The development
of new metallocene compounds with ether functionalized side
chain attached to Cp ring is also attractive as such catalysts could
avoid the infringement of existing patents. The side chains may
also act as coordinating groups during catalysis [7–10]. Side
chains have been imputed to stabilize unstable active species,
prolonging their lifetimes, and to alter the electronic and steric
environments around the metal centers [7–10]. Ether linkage
could also be used for anchorage to silica supports to make het-
erogeneous catalysts [11].
(2-THF-CH2Cp)2ZrCl2 [19], (R3SiOCp)2TiCl2 (R3 = Me2But, Et3, and
i-Pr3) [20], and (4-C5H11-4-C6H10PhOCH2CH2CH2CH2CH2CH2Cp)2
TiCl2 [21]. Most reports of metallocene with pendant ether
functionalized Cp ligands have focused on compounds containing
one or two methylene spacers between the Cp and ether groups
[12–19]; much less attention has been directed towards longer
methylene spacers and/or aryloxy group attached to Cp ring
[21,22]. Only two examples of titanocene [21] or zirconocene
[22] complexes with hexyl spacers between the Cp ring and aryl-
oxy groups have been reported in the literature. However, in the
case of zirconocene complexes, their exact synthetic routes and
spectroscopic data were not provided in the patent literature [22].
This work reports the development of zirconocene complexes
with Cp ring and aryloxy group linked by ethyl or hexyl spacers
such as (2-phenoxyethyl)cyclopentadienyl, {2-(2,6-dimethylphen-
There are few reported metallocene compounds with ether
functionalized side chains. Examples include (ROCH2CH2Cp)2MCl2
(M = Ti and Zr; R = Me [12,13], R = isobornyl, menthyl, and fenchyl
[13]), [CH3CH2CH2OCH2CH2O(CH2)nCp]2ZrCl2 (n = 2, 4, 6, 8) [14],
(MeO-4-PhCH2Cp)2TiCl2 [15], (MeOCH2CH2CH2Cp)2MCl2 (M = Ti
oxy)ethyl}cyclopentadienyl,
(6-phenoxyhexyl)cyclopentadienyl,
and [6-(2,6-dimethylphenoxy)hexyl]cyclopentadienyl ligands. No-
vel zirconocene chloride complexes containing these functional-
ized Cp rings were synthesized here and their catalysis of the
polymerization of ethylene was investigated. In addition, the solid
state structure of zirconium complex with [6-(2,6-dimethylphen-
oxy)hexyl]cyclopentadienyl ligand was confirmed by single crystal
X-ray diffraction.
⇑
Corresponding authors. Tel.: +82 43 261 3395; fax: +82 43 267 2279.
E-mail addresses: leespy@chonnam.ac.kr (J. Lee), ykim@chungbuk.ac.kr (Y. Kim).
These authors contributed equally to this work.
1
0277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2013.08.066

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W.S. Cho et al. / Polyhedron 67 (2014) 205–212
1H NMR (CDCl3, 300.13 MHz, ppm): d 7.02–6.90 (m, 3H, ArH),
2. Experimental
2.1. General procedure
3.94 (t, J = 4.5 Hz, 2H, OCH2CH2OH), 3.89 (t, J = 4.5 Hz, 2H, OCH2-
CH2OH), 2.38 (s, 1H, –OH), 2.28 (s, 6H, ArMe2).
13C{1H} NMR (CDCl3, 75.46 MHz, ppm): d 155.2, 130.8, 128.9,
124.0 (Ar), 72.89 (OCH2CH2OH), 62.31 (OCH2CH2OH), 16.19
(ArMe2).
All manipulations were carried out under a dinitrogen atmo-
sphere using standard Schlenk and glove box techniques. [23]. All
other chemicals were from Aldrich and were used as supplied un-
less otherwise indicated. MAO was from Albemarle (Albemarle
PMAO 10% solution, 1.5 M concentration). Zr(NMeEt)4 was from
DNF Co., Ltd., in Korea. All solvents such as toluene, diethyl ether,
and n-hexane were dried by distillation from sodium diphenylketyl
under dinitrogen and were stored over 3 Å activated molecular
sieves [24]. CDCl3 was dried over 4 Å activated molecular sieves
and used after vacuum transfer to a Schlenk tube equipped with
a J. Young valve [24].
HRMS Exact mass calculated for C10H14NaO2 [M+Na]+:
189.0891, found: 189.0886.
2.3.3. Synthesis of C6H5OCH2CH2CH2CH2CH2CH2OH (3L1)
A light yellow oil 3L1 was prepared in a yield of 86.1% (16.7 g)
by the reaction between phenol (9.41 g, 100 mmol), NaOH (8.00 g,
200 mmol), and 6-chloro-1-hexanol (14.3 g, 105 mmol) in a man-
ner analogous to the procedure for 1L1.
1H NMR (CDCl3, 400.15 MHz, ppm): d 7.25 (m, 3H, ArH), 6.88
(m, 2H, ArH), 3.94 (t, J = 5.1 Hz, 2H, ArOCH2), 3.40 (t, J = 5.4 Hz,
2H, CH2OH), 1.90–1.48 (m, 8H, –CH2–), 1.52 (s, 1H, OH).
13C{1H} NMR (CDCl3, 100.63 MHz, ppm): d 158.0, 128.4, 119.5,
113.5 (Ar), 66.59 (ArOCH2), 32.72 (CH2OH), 31.69, 28.11, 26.92,
24.31 (–CH2–).
2.2. Measurements
1H and 13C{1H} NMR spectra were recorded at ambient temper-
ature on AVANCE III-400 or Bruker DPX-300 NMR spectrometer
using standard parameters. All chemical shifts are reported in d
units with reference to the residual peaks of CDCl3 for proton
(7.24 ppm) and carbon (77.0 ppm) chemical shifts. HRMS was per-
formed by maXis 4G (Hybrid LC/Q-TOF system). Elemental analy-
ses were performed using an EA 1110-FISONS analyzer (CE
Instruments). The polymers’ thermal properties were investigated
by Thermal Analyst Q200 differential scanning calorimetry (DSC)
under dinitrogen at a heating rate of 10 °C/min. The results of the
second scan were recorded to eliminate differences from the sam-
ple history. The polymers’ molecular weights and molecular
weight distributions were determined at 140 °C in 1,2,4-trichloro-
benzene by PL 220 + 220R GPC (Polymer Laboratories) calibrated
with standard polystyrenes.
HRMS Exact mass calculated for C12H19O2 [M+H]+: 195.1385,
found: 195.1380.
2.3.4. Synthesis of Me2C6H3OCH2CH2CH2CH2CH2CH2OH (4L1)
A yellow oil 4L1 was prepared in a yield of 73.9% (16.4 g) by the
reaction between 2,6-dimethylphenol (12.2 g, 100 mmol), NaOH
(8.00 g, 200 mmol), and 6-chloro-1-hexanol (14.3 g, 105 mmol) in
a manner analogous to the procedure for 1L1.
1H NMR (CDCl3, 300.13 MHz, ppm): d 6.99 (d, J = 7.2 Hz, 2H,
ArH), 6.89 (t, J = 7.4 Hz, 1H, ArH), 3.74 (t, J = 6.5 Hz, 2H, ArOCH2),
3.65 (t, J = 6.5 Hz, 2H, CH2OH), 2.25 (s, 6H, ArMe2), 1.82–1.43 (m,
8H, –CH2–), 1.23 (s, 1H, OH).
13C{1H} NMR (CDCl3, 75.46 MHz, ppm): d 151.5, 130.9, 128.7,
123.6 (Ar), 72.09 (ArOCH2), 62.93 (CH2OH), 32.70, 30.38, 25.98,
25.69 (–CH2–), 16.25 (ArMe2).
2.3. Synthesis
HRMS Exact mass calculated for C14H23O2 [M+H]+: 223.1698,
found: 223.1693.
Compounds C6H5OCH2CH2Cp (1L4) [25], Me2C6H3OCH2CH2Br
(2L3) [26], C6H5OCH2CH2CH2CH2CH2CH2Br (3L3) [27], and Me2C6-
H3OCH2CH2CH2CH2CH2CH2Br (4L3) [28] were reported previously;
however, they were achieved in a different way and with different
results including yields and spectroscopic data.
2.3.5. Synthesis of C6H5OCH2CH2OSO2Me (1L2)
Triethylamine (6.00 mL, 43.0 mmol) was added to 1L1 (5.53 g,
40.0 mmol) in dichloromethane (30 mL) at 0 °C and stirred for
10 min. Methanesulfonyl chloride (3.70 mL, 47.8 mmol) was then
added dropwise via cannula at 0 °C. The reaction mixture was
warmed to room temperature and stirred for 3 h. The reaction
was stopped by the addition of water (50 mL) and the organic por-
tion was separated. The aqueous layer was extracted three times
with dichloromethane (3 Â 50 mL) and the combined organic por-
tions were dried over MgSO4 and filtered. The removal of solvent at
reduced pressure gave the desired product 1L2 (8.24 g,
yield = 95.3%) as a yellow oil.
2.3.1. Synthesis of C6H5OCH2CH2OH (1L1)
A mixture of phenol (9.41 g, 100 mmol) and NaOH (8.00 g,
200 mmol) in water (40 mL) was stirred for 10 min. 2-Chloroetha-
nol (8.53 g, 106 mmol) was added dropwise and refluxed for 40 h.
The aqueous layer was extracted three times with dichlorometh-
ane (3 Â 40 mL), and the combined organic portions were washed
with H2O (3 Â 30 mL). The resulting residue was dried over MgSO4
and filtered. The removal of solvent at reduced pressure gave the
desired product 1L1 as colorless oil (7.33 g, yield = 53.1%).
1H NMR (CDCl3, 300.13 MHz, ppm): d 7.28 (t, J = 7.9 Hz, 2H,
ArH), 6.99–6.90 (m, 3H, ArH), 4.05 (t, J = 4.5 Hz, 2H, OCH2CH2OH),
3.93 (t, J = 4.5 Hz, 2H, OCH2CH2OH), 2.75 (s, 1H, OH).
1H NMR (CDCl3, 300.13 MHz, ppm): d 7.28 (t, J = 7.9 Hz, 2H,
ArH), 7.00–6.87 (m, 3H, ArH), 4.54 (m, 2H, OCH2CH2OSO2Me),
4.21 (m, 2H, OCH2CH2OSO2Me), 3.06 (s, 3H, SMe).
13C{1H} NMR (CDCl3, 75.46 MHz, ppm): d 157.8, 129.5, 121.5,
114.4 (Ar), 68.11 (OCH2CH2OSO2Me), 65.58 (OCH2CH2OSO2Me),
37.59 (SMe).
13C{1H} NMR (CDCl3, 75.46 MHz, ppm): d 158.5, 129.4, 121.0,
114.4 (Ar), 69.97 (OCH2CH2OH), 61.22 (OCH2CH2OH).
HRMS Exact mass calculated for C8H10NaO2 [M+Na]+: 161.0578,
found: 161.0573.
HRMS Exact mass calculated for C9H12O4SNa [M+Na]+:
239.0354, found: 239.0347.
2.3.2. Synthesis of Me2C6H3OCH2CH2OH (2L1)
2.3.6. Synthesis of Me2C6H3OCH2CH2OSO2Me (2L2)
A yellow solid 2L1 was prepared in a yield of 51.4% (8.54 g) by
the reaction between 2,6-dimethylphenol (12.2 g, 100 mmol),
NaOH (8.00 g, 200 mmol), and 2-chloroethanol (8.53 g, 106 mmol)
in a manner analogous to the procedure for 1L1.
A yellow oil 2L2 was prepared in a yield of 88.0% (8.60 g) by the
reaction between 2L1 (6.65 g, 40.0 mmol), triethylamine (6.00 mL,
43.0 mmol), and methanesulfonyl chloride (3.70 mL, 47.8 mmol) in
a manner analogous to the procedure for 1L2.

W.S. Cho et al. / Polyhedron 67 (2014) 205–212
207
1H NMR (CDCl3, 300.13 MHz, ppm): d 7.02–6.92 (m, 3H, ArH),
4.52 (t, J = 4.2 Hz, 2H, OCH2CH2OSO2Me), 4.02 (t, 2H, J = 4.2 Hz,
OCH2CH2OSO2Me), 3.08 (s, 3H, SMe), 2.28 (s, 6H, ArMe2).
13C{1H} NMR (CDCl3, 75.46 MHz, ppm): d 154.7, 130.5, 128.8,
124.2 (Ar), 69.16 (OCH2CH2OSO2Me), 68.88 (OCH2CH2OSO2Me),
37.40 (SMe), 16.01 (ArMe2).
2.3.11. Synthesis of C6H5OCH2CH2CH2CH2CH2CH2Br (3L3)
A yellow oil 3L3 was prepared in a yield of 76.3% (5.89 g) by the
reaction between 3L2 (8.17 g, 30.0 mmol) and LiBr (13.0 g,
150 mmol) in a manner analogous to the procedure for 1L3.
1H NMR (CDCl3, 400.15 MHz, ppm): d 7.25 (m, 2H, ArH), 6.89
(m, 3H, ArH), 3.93 (t, J = 5.1 Hz, 2H, ArOCH2), 3.63 (t, J = 5.2 Hz,
2H, CH2Br), 1.79 – 1.39 (m, 8H, –CH2–).
HRMS Exact mass calculated for C11H16O4SNa [M+Na]+:
267.0667, found: 267.0661.
13C{1H} NMR (CDCl3, 100.63 MHz, ppm): d 159.0, 129.4, 120.5,
114.4 (Ar), 67.66 (ArOCH2), 62.80 (CH2Br), 32.62, 29.21, 25.86,
25.50 (–CH2–).
2.3.7. Synthesis of C6H5OCH2CH2CH2CH2CH2CH2OSO2Me (3L2)
A yellow oil 3L2 was prepared in a yield of 94.5% (10.3 g) by the
reaction between 3L1 (7.77 g, 40.0 mmol), triethylamine (6.00 mL,
43.0 mmol), and methanesulfonyl chloride (3.70 mL, 47.8 mmol) in
a manner analogous to the procedure for 1L2.
HRMS Exact mass calculated for C12H18BrO [M+H]+: 257.0541,
found: 257.0536.
2.3.12. Synthesis of Me2C6H3OCH2CH2CH2CH2CH2CH2Br (4L3)
A yellow oil 4L3 was prepared in a yield of 79.2% (6.78 g) by the
reaction between 4L2 (9.01 g, 30 mmol) and LiBr (13.0 g,
150 mmol) in a manner analogous to the procedure for 1L3.
1H NMR (CDCl3, 300.13 MHz, ppm): d 7.00 (d, J = 7.6 Hz, 2H,
ArH), 6.92 (t, J = 7.4 Hz, 1H, ArH), 3.75 (t, J = 6.5 Hz, 2H, ArOCH2),
3.42 (t, J = 6.4 Hz, 2H, CH2Br), 2.26 (s, 6H, ArMe2), 1.93–1.52 (m,
8H, –CH2–).
1H NMR (CDCl3, 400.15 MHz, ppm): d 7.25 (m, 2H, ArH), 6.87
(m, 3H, ArH), 4.21 (t, J = 6.5 Hz, 2H, ArOCH2), 3.93 (t, J = 6.4 Hz,
2H, CH2OSO2Me), 2.97 (s, 3H, SMe), 1.80–1.45 (m, 8H, –CH2–).
13C{1H} NMR (CDCl3, 100.63 MHz, ppm): d 158.9, 129.3, 120.4,
114.3 (Ar), 69.92 (CH2O), 67.36 (ArOCH2), 37.17 (SMe), 28.94,
28.93, 25.45, 25.10 (–CH2–).
HRMS Exact mass calculated for C13H21SO4 [M+H]+: 273.1161,
found: 273.1155.
13C{1H} NMR (CDCl3, 75.46 MHz, ppm): d 155.9, 130.9, 128.7,
123.6 (Ar), 71.89 (ArOCH2), 33.85 (CH2Br), 32.73, 30.23, 28.07,
25.39 (–CH2–), 16.25 (ArMe2).
2.3.8. Synthesis of Me2C6H3OCH2CH2CH2CH2CH2CH2OSO2Me (4L2)
A yellow oil 4L2 was prepared in a yield of 93.3% (11.2 g) by the
reaction between 4L1 (8.89 g, 40.0 mmol), triethylamine (6.00 mL,
43.0 mmol), and methanesulfonyl chloride (3.70 mL, 47.8 mmol) in
a manner analogous to the procedure for 1L2.
HRMS Exact mass calculated for C14H22BrO [M+H]+: 285.0854,
found: 285.0848.
2.3.13. In situ generation of C6H5OCH2CH2Cp (1L4)
1H NMR (CDCl3, 300.13 MHz, ppm): d 7.00 (d, J = 7.6 Hz, 2H,
ArH), 6.91 (t, J = 6.6 Hz, 1H, ArH), 4.23 (t, J = 6.5 Hz, 2H, ArOCH2),
3.74 (t, J = 6.4 Hz, 2H, CH2OSO2Me), 2.99 (s, 3H, SMe), 2.25 (s, 6H,
ArMe2), 1.82–1.49 (m, 8H, –CH2–).
A solution of LiCp (1.58 g, 21.9 mmol) in THF (20 mL) was added
dropwise to solution of 1L3 (4.03 g, 20.0 mmol) in THF (30 mL) at
À60 °C. The reaction mixture was then warmed to room tempera-
ture and stirred for 12 h. The reaction was stopped by the addition
of 30 mL saturated aqueous NH4Cl and the organic portion was
separated. The mixture was extracted with diethyl ether
(2 Â 50 mL) and the combined organic portions were dried over
MgSO4, filtered, and evaporated to dryness. Colorless oil 1L4 was
obtained and used without further purification (1.31 g, 35.2%).
13C{1H} NMR (CDCl3, 75.46 MHz, ppm): d 155.9, 130.8, 128.7,
123.6 (Ar), 71.80 (ArOCH2), 69.96 (CH2O), 37.30 (SMe), 30.17,
29.06, 25.63, 25.38 (–CH2–), 16.20 (ArMe2).
HRMS Exact mass calculated for C15H25O4S [M+H]+: 301.1474,
found: 301.1469.
2.3.9. Synthesis of C6H5OCH2CH2Br (1L3)
2.3.14. In situ generation of Me2C6H3OCH2CH2Cp (2L4)
1L2 (6.49 g, 30.0 mmol) in acetone (20 mL) was added dropwise
to LiBr (13.0 g, 150 mmol) in 100 mL acetone at room temperature.
After stirring for 24 h, a reaction was stopped by the addition of
water (50 mL) and the organic portion was separated. The aqueous
layer was extracted three times with diethyl ether (3 Â 50 mL) and
the combined organic portions were dried over MgSO4. Filtration
followed by evaporation gave the desired product 1L3 (4.08 g,
yield = 67.6%) as a yellow oil.
Pale yellow oil 2L4 was prepared in a yield of 51.3% (2.20 g) by
the reaction between 2L3 (4.58 g, 20.0 mmol) and LiCp (1.58 g,
21.9 mmol) in a manner analogous to the procedure for 1L4.
2.3.15. In situ generation of C6H5OCH2CH2CH2CH2CH2CH2Cp (3L4)
Pale yellow oil 3L4 was prepared in a yield of 92.8% (4.50 g) by
the reaction between 3L3 (5.14 g, 20.0 mmol) and LiCp (1.58 g,
21.9 mmol) in a manner analogous to the procedure for 1L4.
1H NMR (CDCl3, 300.13 MHz, ppm): d 7.28 (t, J = 7.9 Hz, 2H,
ArH), 7.00–6.89 (m, 3H, ArH), 4.28 (t, J = 4.5 Hz, 2H, OCH2CH2Br),
3.62 (t, J = 4.5 Hz, 2H, OCH2CH2Br).
2.3.16. In situ generation of Me2C6H3OCH2CH2CH2CH2CH2CH2Cp (4L4)
Pale yellow oil 4L4 was prepared in a yield of 83.6% (4.52 g) by
the reaction between 4L3 (5.69 g, 20.0 mmol) and LiCp (1.58 g,
21.9 mmol) in a manner analogous to the procedure for 1L4.
13C{1H} NMR (CDCl3, 75.46 MHz, ppm): d 158.1, 129.6, 121.4,
114.7 (Ar), 67.77 (OCH2CH2), 29.11 (OCH2CH2Br).
HRMS Exact mass calculated for C8H9BrNaO [M+Na]+: 222.9734,
found: 222.9729.
2.3.17. Synthesis of (C6H5OCH2CH2Cp)2ZrCl2 (1)
2.3.10. Synthesis of Me2C6H3OCH2CH2Br (2L3)
(Route 1) A solution of 1L4 (0.933 g, 5.01 mmol) in diethyl ether
(20 mL) was treated with n-butyllithium (5.25 mmol, 2.1 mL of
2.5 M solution in hexane) at À78 °C. The reaction mixture was then
warmed to room temperature and stirred overnight. All volatiles
were removed and the remaining ivory solid was dried under vac-
uum after washed twice with n-hexane. Into a precooled flask con-
taining ZrCl4 (0.466 g, 2.00 mmol) and lithiated 1L4 (0.773 g,
4.02 mmol) powders was added diethyl ether (40 mL) at À78 °C
with vigorous stirring. The reaction mixture was warmed to room
temperature over 2 h and stirred overnight at this temperature.
The yellow solution was filtered through Celite and concentrated
A yellow oil 2L3 was prepared in a yield of 74.2% (5.10 g) by the
reaction between 2L2 (7.32 g, 30.0 mmol) and LiBr (13.0 g,
150 mmol) in a manner analogous to the procedure for 1L3.
1H NMR (CDCl3, 300.13 MHz, ppm): d 7.04–6.96 (m, 3H, ArH),
4.10 (t, J = 6.2 Hz, 2H, OCH2CH2Br), 3.67 (t, J = 6.2 Hz, 2H, OCH2CH2-
Br), 2.32 (s, 6H, ArMe2).
13C{1H} NMR (CDCl3, 75.46 MHz, ppm): d 155.0, 130.7, 128.9,
124.1 (Ar), 71.39 (OCH2CH2Br), 30.15 (OCH2CH2Br), 16.29 (ArMe2).
HRMS Exact mass calculated for C10H14BrO [M+H]+: 229.0228,
found: 229.0222.

208
W.S. Cho et al. / Polyhedron 67 (2014) 205–212
to about 10 mL. Overnight cooling at –20 °C after the addition of
10 mL of n-hexane afforded 0.366 g (34.4%) of yellow crystals of 1.
(Route 2) Zr(NMeEt)4 (0.809 g, 2.50 mmol) in hexane (10 mL)
was added dropwise via cannula with vigorous stirring to a flask
precooled at À78 °C containing freshly obtained 1L4 (0.933 g,
5.01 mmol) in hexane (10 mL). The reaction mixture was allowed
to warm slowly to room temperature over 2 h. After 12 h stirring,
all volatiles were evaporated under the reduced pressure, leaving
yellow oil, to which methylene chloride (20 mL) was added. Me3-
SiCl (1.36 g, 12.5 mmol) was added slowly via syringe at 0 °C with
vigorous stirring. The reaction mixture was slowly allowed to
warm to room temperature over 20 min and then stirred for
12 h. The solvent evaporated to afford the desired product 1 as a
deep yellow solid. (1.14 g, yield = 85.5%).
Elemental Anal. Calc. for C38H50Cl2O2Zr: C, 65.12; H, 7.19.
Found: C, 65.38; H, 7.42%.
2.4. X-ray structure determination of 4
Crystallographic assessment of 4 was performed at ambient
temperature using a Bruker APEXII CCD area detector diffractome-
ter with graphite-monochromated Mo K
a (k = 0.71073 Å) radia-
tion. A single crystal of suitable size and quality was selected and
mounted on a glass capillary using ParatoneÒ oil and centered in
the X-ray beam using a video camera. Multi-scan reflection data
were collected with a frame width of 0.5° in w and h and 5 s expo-
sures per frame. Determination of cell parameters, data reduction,
and empirical absorption corrections were conducted using the
programs APEX2, SAINT and SADABS, respectively [29]. The structure
of 4 was solved by direct methods and refined to convergence
using full matrix least-squares with anisotropic thermal parame-
ters for all non-hydrogen atoms using the SHELXTL program package
[30]. The molecular structure of 4 (Fig. 2) was drawn using the pro-
gram DIAMOND [31]. Details of the crystallographic data and param-
eters are listed in Table 1.
1H NMR (CDCl3, 300.13 MHz, ppm): d 7.26 (t, J = 7.6 Hz, 4H,
ArH), 6.95–6.86 (m, 6H, ArH), 6.33 (s, 8H, Cp-H), 4.15 (t,
J = 6.1 Hz, 4H, OCH2CH2OCp), 3.12 (t, J = 6.1 Hz, 4H, OCH2CH2Cp).
13C{1H} NMR (CDCl3, 75.46 MHz, ppm): d 158.6, 131.0, 129.5,
120.8, 117.7, 114.5, 112.2 (Ar, Cp), 67.37 (OCH2CH2Cp), 30.15
(OCH2CH2Cp).
Elemental Anal. Calc. for C26H26Cl2O2Zr: C, 58.63; H, 4.92.
Found: C, 58.58; H, 5.01%.
2.5. Ethylene polymerization
2.3.18. Synthesis of (Me2C6H3OCH2CH2Cp)2ZrCl2 (2)
A deep yellow solid 2 was prepared in a yield of 71.9% (2.11 g)
by the reaction between Zr(NMeEt)4 (1.62 g, 5.00 mmol), 2L4
(2.14 g, 10.0 mmol), and Me3SiCl (2.72 g, 25.0 mmol) in a manner
analogous to the synthetic route 2 for 1.
Ethylene was polymerized in 250 mL Schlenk flask. Toluene, the
polymerization solvent, was distilled from sodium diphenylketyl
under dinitrogen immediately before use. Toluene (50 mL), MAO
(20 mmol or 10 mmol), and zirconium compounds (5
lmol or
1H NMR (CDCl3, 300.13 MHz, ppm): d 6.98–6.89 (m, 6H, ArH),
6.37 (s, 8H, Cp-H), 3.92 (t, J = 6.3 Hz, 4H, OCH2CH2OCp), 3.13 (t,
J = 6.3 Hz, 4H, OCH2CH2Cp), 2.15 (s, 12H, ArMe2).
10 mol) were sequentially injected into the flask at the desired
l
polymerization temperature. The mixtures were then saturated
with 1 bar ethylene, which was kept constant. After 3 min or 1 h,
polymerizations were terminated by venting the ethylene gas
and quenching with a small volume of MeOH. The polymer was
isolated by filtration, sequentially washed with MeOH, 10% HCl
in MeOH, and then dried in vacuo at 50 °C for 12 h.
13C{1H} NMR (CDCl3, 75.46 MHz, ppm): d 155.6, 131.5, 130.9,
128.8, 123.8, 117.7, 112.3 (Ar, Cp), 71.55 (OCH2CH2Cp), 31.39
(OCH2CH2Cp), 16.24 (ArMe2).
Elemental Anal. Calc. for C30H34Cl2O2Zr: C, 61.21; H, 5.82.
Found: C, 61.33; H, 5.94%.
3. Results and discussion
2.3.19. Synthesis of (C6H5OCH2CH2CH2CH2CH2CH2Cp)2ZrCl2 (3)
A deep yellow solid 3 was prepared in a yield of 70.1% (2.26 g)
by the reaction between Zr(NMeEt)4 (1.62 g, 5.00 mmol), 3L4
(2.42 g, 10.0 mmol), and Me3SiCl (2.72 g, 25.0 mmol) in a manner
analogous to the synthetic route 2 for 1.
The aim of this work is the synthesis, characterization, and the
comparison of ethylene polymerization behaviors of novel zirco-
nium complexes with pendant aryloxy groups attached to the
metallocene moiety by –CH2CH2– and –CH2CH2CH2CH2CH2CH2–
spacers. The final products synthesized were bis[(2-phenoxyeth-
yl)cyclopentadienyl]zirconium dichloride (1), bis[{2-(2,6-dimeth-
1H NMR (CDCl3, 400.15 MHz, ppm): d 7.25 (m, 5H, ArH), 6.89
(m, 5H, ArH), 6.26 (t, J = 2.1 Hz, 3H, Cp-H), 6.18 (t, J = 2.1 Hz, 3H,
Cp-H), 3.92 (t, J = 5.2 Hz, 4H, ArOCH2), 2.62 (t, J = 6.2 Hz, 4H, CH2-
Cp), 1.77–1.36 (m, 16H, –CH2–).
ylphenoxy)ethyl}cyclopentadienyl]zirconium
dichloride
(2),
bis[(6-phenoxyhexyl)cyclopentadienyl]zirconium dichloride (3),
and bis[{6-(2,6-dimethylphenoxy)hexyl}cyclopentadienyl]zirco-
nium dichloride (4) (See Fig. 1). The synthetic routes to complexes
1–4 are outlined in Scheme 1. To introduce two different ancillary
groups such as Cp ring and aryloxy group at the ends of the ethyl or
hexyl spacer, a set of stepwise reactions was performed.
13C{1H} NMR (CDCl3, 100.63 MHz, ppm): d 158.1, 134.0, 128.4,
119.5, 115.7, 113.5, 111.2, (Ar and Cp), 66.70 (ArOCH2), 29.54 (CH2-
Cp), 29.07, 28.19, 28.01, 24.79 (–CH2–).
Elemental Anal. Calc. for C34H42Cl2O2Zr: C, 63.33; H, 6.57.
Found: C, 63.49; H, 6.38%.
The preparation of 2-phenoxyethan-1-ol (1L1) was achieved by
the reaction of phenol, 2-chloroethanol, and NaOH in water. Suit-
able workup gave 1L1 as colorless oil in 53.1% yield and the subse-
quential reaction between 1L1 and MsCl in the presence of NEt3
afforded 2-phenoxyethyl methanesulfonate (1L2) in 95.3% yield
after aqueous workup. Excess NEt3 was necessary for the success-
ful synthesis of compound 1L2, which was treated with LiBr in ace-
tone to give (2-bromoethoxy)benzene (1L3) as a yellow oil in 67.6%
yield. 1L3 was a critical intermediate in the synthesis of the desired
ligand 1L4; an attempt at the direct nucleophilic substitution of
1L2 with LiCp to prepare 1L4 yielded only the starting materials
after workup (Scheme 1). Compound 1L4 formed in 35.2% yield
when compound 1L3 reacted with lithium cyclopentadienylide in
THF. It was used without further purification and easily decom-
2.3.20. Synthesis of (Me2C6H3OCH2CH2CH2CH2CH2CH2Cp)2ZrCl2 (4)
The desired product 4 as an orange-yellow solid was prepared
from Zr(NMeEt)4 (0.186 g, 0.575 mmol), 4L4 (0.311 g, 1.15 mmol),
and Me3SiCl (0.313 g, 2.88 mmol) in a yield of 84.3% (0.340 g) in
a manner analogous to the synthetic route 2 for 1.
1H NMR (CDCl3, 300.13 MHz, ppm): d 6.99 (d, J = 7.5 Hz, 4H,
ArH), 6.88 (t, J = 4.1 Hz, 2H, ArH), 6.28 (t, J = 2.6 Hz, 4H, Cp-H),
6.19 (t, J = 2.6 Hz, 4H, Cp-H), 3.72 (t, J = 6.5 Hz, 4H, ArOCH2), 2.64
(t, J = 7.7 Hz, 4H, CH2Cp), 2.24 (s, 12H, ArMe2), 1.79–1.23 (m, 16H,
–CH2–).
13C{1H} NMR (CDCl3, 75.46 MHz, ppm): d 156.0, 135.0, 130.9,
128.7, 123.6, 116.7, 112.2, (Ar and Cp), 72.09 (ArOCH2), 30.60 (CH2-
Cp), 30.33, 30.13, 29.23, 25.93 (–CH2–), 16.27 (ArMe2).

W.S. Cho et al. / Polyhedron 67 (2014) 205–212
209
Table 1
Crystallographic data and parameters for compound 4.
4
C
Empirical formula
Formula weight
Crystal system
Space group
Unit cell dimensions
a (Å)
38H50O2Cl2Zr
700.90
monoclinic
P21/c
15.338(3)
18.181(3)
13.854(2)
90
b (Å)
c (Å)
a
(°)
b (°)
110.189(8)
90
3626.1(10)
4
1.284
0.481
c
(°)
V (Å3)
Z
Dcalc (g/cm3)
l
(mmÀ1
)
F(000)
1472
Index ranges
h range (°)
Reflections collected
À21 6 h 6 22, À25 6 k 6 27, À20 6 l 6 20
1.41 6 h 6 32.02
52011
Independent reflections
Number of observed reflections (I > 2
Number of parameters refined
12225
6206
392
r(I))
GOF (I > 2
r(I))
0.998
R1 (all data)
0.1196
0.0462
a
R1(I > 2r(I))
wR2 (all data)
0.1380
0.1061
0.695 and À0.522
a
wR2(I > 2
r(I))
Largest difference in peak and hole (e ÅÀ3
)
P
P
P
P
a
R1
=
||Fo| – |Fc||/ |Fo| and wR2 = { [w(Fo2 – Fc2)2]/ [w(Fo2)2]}1/2
.
copy and HR-mass spectrometry or elemental analysis. The NMR
spectra are in accord with the suggested structures and all proton
and carbon chemical shifts appeared in the expected ranges. The
NMR signals were sharp and variable-temperature studies showed
no evidence of inter- or intra-molecular ligand exchange at ambi-
ent temperature.
O
O
O
O
Cl
Cl
Cl
Cl
Zr
Zr
Recrystallization from dichloromethane/diethyl ether at À20 °C
gave 4 as an orange-yellow crystalline solid suitable for X-ray dif-
fraction analysis, which assessed its solid-state structure (Fig. 2).
Tables 1 and 2 list detailed crystallographic data and selected
interatomic distances and angles, respectively. The zirconium com-
plex 4 crystallized in the space group P21/c and different views of
the structure (Fig. 2(a)–(c)) show that chlorine atoms and the cen-
troids of the Cp ring formed a considerably distorted pseudo-tetra-
hedral coordination geometry around the zirconium with angles
ranging from 95.15° (Cl1–Zr–Cl2) to 131.61° (Ccent1–Zr–Ccent2).
The Cp rings were slightly staggered, with side chains arranged
at the open side of the stacking. The structure of 4 showed that
the complex’s aryloxy groups were far from the zirconium center,
with neither intra- nor inter-molecular interactions occurring be-
tween the O atom and the Zr center. The plane perpendicular to
2
1
O
O
O
O
Cl
Cl
Cl
Cl
Zr
Zr
3
4
Fig. 1. Sketches of the synthesized complexes.
the Cl1–Zr–Cl2 plane and bisecting the Cl1–Zr–Cl2 angle was
r-
posed even at room temperature through an intramolecular Diels–
Alder reaction. Straightforward metallation of 1L4 with Zr(NMeEt)4
followed by the treatment of trimethylsilyl chloride gave bis[(2-
phenoxyethyl)cyclopentadienyl]zirconium dichloride (1) as a deep
yellow crystalline solid in 85.5% yield. The reaction between two
equivalents lithiated 1L4 and ZrCl4 also gave the desired product
1 with a poor yield of 34.4%, suggesting that the mild reaction con-
ditions of amine elimination were required. Complexes 2–4 were
prepared in a manner analogous to the multistep synthetic route
for 1 via amine elimination process. Like other zirconocene dichlo-
rides, complexes 1–4 were comparably stable in air and were freely
soluble in polar organic solvents and toluene but insoluble in
hydrocarbon solvents such as n-hexane and n-pentane. All com-
pounds were fully characterized by 1H and 13C{1H} NMR spectros-
symmetric; the C2 symmetric axis bisected the Cl1–Zr–Cl2 angle,
giving 4 a pseudo-C2v symmetry. The bond distance data (Table 2)
show that the Cp’ ring formed largely uniform Zr–CCp distances,
averaging 2.504 Å with a small standard deviation of 0.020 Å, indi-
cating that two Cp’ rings were bonded to the Zr atom in the usual
g
5 fashion. Zr–Ccent1 and Zr–Ccent2 lengths were 2.196 and 2.202 Å,
respectively. The Ccent1–Zr–Ccent2 angle (131.61(5)°) was found to
be similar to that of other zirconocene complexes [32]. A similar
trend was shown by the Cl1–Zr–Cl2 angle (95.15(3)°). The substit-
uents of the Cp ligand were oriented in the lateral sector in oppo-
site directions to each other. The Zr–Cl bond lengths were
2.4506(8) Å and 2.4554(9) Å. An acute dihedral angle of 51.13(6)°
was found between the two p-ring planes.

210
W.S. Cho et al. / Polyhedron 67 (2014) 205–212
Scheme 1. Synthetic routes to 1–4.
Fig. 2. X-ray molecular structure of compound 4 with 50% thermal ellipsoids. H atoms are omitted for clarity. (a) Side view. (b) Front view. (c) Top view (Aryl rings are
omitted for clarity.).
Ethylene polymerization involving compounds 1–4 and MAO as
a cocatalyst were performed at 50 °C (Table 3, entries 1–3, 6). To
compare catalytic property with those of 1–4, polymerization with
Cp2ZrCl2 was also performed under similar condition (Table 3, en-
try 9). The polymerization results at 50 °C show that the catalytic
activity was closely related to the distance between Cp ring and
aryloxy groups in complexes 1–4. Even though the doubled con-
ZrCl2 [19]. This behavior can be explained by the possible forma-
tion of -donated complex with direct contacts between donor
r
oxygen atoms of short ether linkage and the cationic zirconium
center during the polymerization [33]. In contrast with these re-
sults, 3 and 4 with long spacers between Cp ring and aryloxy group
behave as a highly active single-site catalyst. Complexes 3, 4, and
Cp2ZrCl2 could catalyze ethylene polymerizations well at 50 °C
within just 3 min. The activities of compounds 3 and 4 at 50 °C
were about 87% and 48% of that of Cp2ZrCl2, respectively. This rel-
atively small decrease of activity for 3 and 4 can be explained that
the molecular structure in Fig. 2, where the aryoxy group is far
centration of catalyst (10 lmol) and elongated polymerization
time (1 h) were applied, 1 and 2 produced trace amount of polyeth-
ylene. The similar observations were reported in the literature for
[CH3CH2CH2OCH2CH2O(CH2)2Cp]2ZrCl2 [14] and (3-THF-CH2Cp)2-

W.S. Cho et al. / Polyhedron 67 (2014) 205–212
211
Table 2
The data given in Table 3 and Fig. 3(a) clearly indicate that the cat-
alytic activity of 3/MAO and 4/MAO systems towards synthesis of
polyethylene increases as temperature rose from 50 to 90 °C. Both
systems showed that activity increased sharply with heating to
70 °C and then increased smoothly with further heating to 90 °C.
However, Cp2ZrCl2 showed the maximum activity in 70 °C. Com-
plexes 3, 4, and Cp2ZrCl2 yielded high-density polyethylene with
Mw of 35300–273000, 68000–491000, and 21400–148000,
respectively (Table 3, entries 3–11). As shown in Fig. 3(b), the tem-
perature of the polymerization significantly affected the polymers’
molecular weights, consistently decreasing them at higher temper-
ature. A similar trend of lowering polyethylene’s Tm with increas-
ing temperature was observed. Interestingly, 4/MAO produced
polyethylene with a very high molecular weight of 491000 at
50 °C (Table 3, entry 6). The produced polyethylene showed a
slightly higher Mw/Mn of 2.72–5.38 (Table 3, entries 3–8) than that
formed using other zirconocenes [3–6], suggesting that chain
transfer reactions occurred due to the coordination of oxygen
atoms of the pendant groups of 3 or 4 with the Al centers of
MAO. Furthermore, 3/MAO system showed better catalytic activity
than 4/MAO system; however, 4/MAO system produced polyethyl-
ene with higher molecular weight.
Selected interatomic distances (Å) and angles (°) of compound 4.
Distances
Zr–Cl1
Zr–C1
Zr–C3
2.4506(8)
2.524(3)
2.477(3)
2.520(3)
2.529(3)
2.485(3)
2.1961(13)
1.420(4)
1.406(4)
1.409(4)
1.407(4)
1.402(4)
1.513(4)
Zr–Cl2
Zr–C2
Zr–C4
2.4554(9)
2.503(3)
2.486(3)
2.536(3)
2.485(3)
2.497(3)
2.2023(13)
1.401(4)
1.410(4)
1.414(4)
1.411(4)
1.402(4)
1.503(3)
Zr–C5
Zr–C20
Zr–C22
Zr–C24
Zr–Ccent2
C2–C3
C4–C5
C20–C21
C22–C23
C24–C20
C20–C25
Zr–C21
Zr–C23
Zr–Ccent1
C1–C2
C3–C4
C5–C1
C21–C22
C23–C24
C1–C6
a
b
Angles
Cl1–Zr–Cl2
95.14(3)
105.70(4)
105.88(4)
178.56(4)
112.20(4)
114.5(2)
C
cent1–Zr– Ccent2
131.61(5)
106.82(5)
105.80(4)
179.03(5)
111.77(5)
114.3(2)
C
C
C
cent1–Zr–Cl1
cent2–Zr–Cl1
cent1–C1–C6
Ccent1–Zr–Cl2
Ccent2–Zr–Cl2
Ccent2–C20–C25
C20–C25–C26
C30–O2–C31
C1–C6–C7
C11–O1–C12
a
Ccent1 = centroid of C1, C2, C3, C4, and C5.
Ccent2 = centroid of C20, C21, C22, C23, and C24.
b
In summary, bis[(2-phenoxyethyl)cyclopentadienyl]zirconium
dichloride (1), bis[{2-(2,6-dimethylphenoxy)ethyl}cyclopentadi-
enyl]zirconium
dichloride
(2),
bis[(6-phenoxyhexamethyl-
away from the metal center, is predominantly maintained in
solution.
ene)cyclopentadienyl]zirconium dichloride (3), and bis[{6-(2,6-
dimethylphenoxy)hexamethylene}cyclopentadienyl]zirconium
dichloride (4) were prepared in five steps from inexpensive, com-
mercially available materials. They are zirconium complexes con-
taining Cp ring and aryloxy group linked by –CH2CH2– or –
CH2CH2CH2CH2CH2CH2– spacers. In the presence of MAO cocata-
lyst, complexes 1 and 2 showed very low catalytic activity towards
Generally, the metallocene catalysts containing oxygen atoms
have been known to produce polyethylene with low molecular
weight and somewhat broader molecular weight distribution
[14]. Unexpectedly, 3 and 4 gave polyethylene with much higher
molecular weight than that of Cp2ZrCl2. The introduction of long
chain aryloxy group in Cp2ZrCl2 induces the small decrease in cat-
alytic activity as well as a large increase in molecular weight.
Molecular weight distributions were also somewhat broad in our
systems. The resulting polyethylene’s Tm and Tc are indicative of
high-density polyethylene.
In order to further investigate the characteristics of catalyst for
the polymerization reaction, the ethylene polymerizations for
compounds 3, 4, and Cp2ZrCl2, which showed the good catalytic
activity at 50 °C, were carried out at various temperatures under
the fixed MAO concentration (Table 3, entries 3–11). Generally,
the activity in the olefin polymerization using homogenous cata-
lysts increases along with the raised polymerization temperature.
Table 3
Ethylene polymerization data for catalysts 1–4 and Cp2ZrCl2 in the presence of
cocatalyst MAO.
e
Entry Cat.
Tp
Polymer
Ac
Tm
Tc
Mw
Mw/
Mn
e
(°C) (g)
(°C)d
(°C)d
f
f
1a
1
2
3
50
50
50
70
90
50
70
90
0.0215
2.2
2.9
134.3 114.2
133.3 114.3
–
–
f
f
2a
0.0294
0.514
0.673
0.746
0.285
0.515
0.665
0.593
1.287
1.135
–
–
3b
4b
5b
6b
7b
8b
9b
10b
11b
2060 135.9 113.3 273,000 3.24
2690 132.4 116.9 117,000 2.72
2980 128.9 116.1 35,300
1140 133.6 115.7 491,000 3.77
2060 132.3 116.7 144,000 4.83
2660 131.5 116.4 68,800
2370 136.2 117.6 148,000 3.02
5150 133.2 119.0 36,400
4540 129.7 116.3 21,400
5.38
4
3.23
Cp2ZrCl2 50
70
90
2.89
3.56
a
Polymerization Condition: [Zr] = 10
lmol, [MAO] = 20 mmol, [Al]/[Zr] = 2000,
ethylene 1 bar, toluene 50 mL, 1 h.
b
Polymerization Condition: [Zr] = 5
lmol, [MAO] = 10 mmol, [Al]/[Zr] = 2000,
ethylene 1 bar, toluene 50 mL, 3 min.
c
Activity = kg polymer/(mol Zr  hr  bar).
d
e
f
Determined by DSC.
Fig. 3. (a) Catalytic activities and (b) Mw of polyethylene vs. polymerization
temperature for complexes 3 (d), 4 (N), and Cp2ZrCl2 (j).
Determined by GPC.
Not determined.

212
W.S. Cho et al. / Polyhedron 67 (2014) 205–212
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Acknowledgments
We thanks the financial support from the National Research
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Appendix A. Supplementary data
CCDC 856703 contains the supplementary crystallographic data
for 4. These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ,
UK; fax: (+44) 1223 336 033; or e-mail: deposit@ccdc.cam.ac.uk.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.poly.2013.08.066.
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