Synthesis, structures, and olefin polymerization characteristics of group 4 catalysts [Zr{(OAr)2py}Cl2(D)] (D = O-donors, Cl[HPR 3]) supported by tridentate pyridine-2,6-bis(aryloxide) ligands

Article abstract of DOI:10.1021/om050864z

The Zr(IV) complexes [Zr(L¹)X₂(D)] [H ₂L¹ = 2,6-di(3-tert-butyl-5-methylphen-2-ol)pyridine; X = Cl, D = thf (1), OEt₂ (2), acetophenone (3), benzophenone (4), 2-acetonaphthone (5), Cl[fHPR₃

Full text of DOI:10.1021/om050864z

Organometallics 2006, 25, 785-792
785
Synthesis, Structures, and Olefin Polymerization Characteristics of
Group 4 Catalysts [Zr{(OAr)2py}Cl2(D)] (D ) O-Donors, Cl[HPR3])
Supported by Tridentate Pyridine-2,6-bis(aryloxide) Ligands
Michael C. W. Chan,*,§ Ka-Ho Tam,† Nianyong Zhu,† Pauline Chiu,† and
Shigekazu Matsui‡
Department of Biology and Chemistry, City UniVersity of Hong Kong, Tat Chee AVenue, Kowloon,
Hong Kong, China, Department of Chemistry and HKU-CAS Joint Laboratory for New Materials,
The UniVersity of Hong Kong, Pokfulam Road, Hong Kong, China, and R&D Center,
Mitsui Chemicals, Inc., 580-32 Nagaura, Sodegaura, Chiba 299-0265, Japan.
ReceiVed October 6, 2005
The Zr(IV) complexes [Zr(L1)X2(D)] [H2L1 ) 2,6-di(3-tert-butyl-5-methylphen-2-ol)pyridine; X )
Cl, D ) thf (1), OEt2 (2), acetophenone (3), benzophenone (4), 2-acetonaphthone (5), Cl[HPR3] {R )
Me (6), Et (7); R3 ) Me2Ph (8)}; X ) CH2Ph (9)] have been synthesized, and the crystal structures of
3, 4, and 7 have been determined. These catalysts, assisted by the robustness and chelating strength of
the pyridine-bis(phenolate) moiety, exhibit excellent activities for ethylene polymerization in conjunction
with MAO. Studies to assess the impact of the donor group during the catalytic process suggest that the
same active species is generated by 1-8/MAO and the donor group does not play an active role. Even
higher activities are observed for the 1/iBu3Al/Ph3CB(C6F5)4 system in ethylene polymerization and
propylene copolymerization reactions (36 590 and 15 700 g of polymer (mmol of catalyst)-1 h-1,
respectively), with the latter displaying good C3 incorporation (25.4 mol % C3). Insight into the catalytic
behavior of the 1/MAO system has been derived from GPC and NMR characterization of the polymers
prepared under different reaction conditions. 1H and 13C NMR end-group analyses reveal resonances for
saturated methyl chain-end groups only and undetectable or negligible levels of unsaturated vinyl chain
ends. This indicates that for the polymerization chain-transfer mechanism, the conventional â-H transfer
reactions to the metal/monomer are insignificant and the unusual chain transfer to Al pathway is vastly
dominant.
co-workers have pioneered a family of bis(phenoxyimine) group
4 polyolefin catalysts that are remarkable for their ultrahigh
activities and versatile polymerization capabilities.3 The ability
of tetradentate [O2L2] (L ) imine, amine, sulfide) ligands to
mediate octahedral catalytic centers has also been extensively
explored.4 Linearly linked [O2L2] auxiliaries typically coordinate
to the metal in a “R-cis” configuration to afford C2-symmetric
structures, and this has been instrumental in the development
Introduction
Aryloxide- and alkoxide-based chelating ligands have proved
to be a success story in the advancement of post-metallocene
polyolefin catalysts.1 The underlying design strategy has targeted
non-cyclopentadienyl species that are isoelectronic with the
[Cp2Zr] moiety, and the employment of multidentate alkoxide
auxiliaries has expanded the range of environments around the
catalytic active site. Bidentate ligand sets of the type [O,O] and
[O,L]2 have been particularly prominent.2 Notably, Fujita and
(3) (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. (c) Mitani, M.; Furuyama, R.;. Mohri, J.;
Saito, J.; Ishii, S.; Terao, H.; Nakano, T.; Tanaka, H.; Fujita, T. J. Am.
Chem. Soc. 2003, 125, 4293. (d) Mitani, M.; Nakano, T.; Fujita, T. Chem.
Eur. J. 2003, 9, 2396. (e) Mitani, M.; Saito, J.; Ishii, S.; Nakayama, Y.;
Makio, H.; Matsukawa, N.; Matsui, S.; Mohri, J.; Furuyama, R.;. Terao,
H.; Bando, H.; Tanaka, H.; Fujita, T. Chem. Rec. 2004, 4, 137. (f) Makio,
H.; Fujita, T. Bull. Chem. Soc. Jpn. 2005, 78, 52.
* To whom correspondence should be addressed. E-mail:
mcwchan@cityu.edu.hk. Fax: +852 2788 7406.
§ City University of Hong Kong.
† The University of Hong Kong.
‡ Mitsui Chemicals, Inc.
(1) Reviews: (a) Gibson, V. C.; Spitzmesser, S. K. Chem. ReV. 2003,
103, 283. (b) Suzuki, Y.; Terao, H.; Fujita, T. Bull. Chem. Soc. Jpn. 2003,
76, 1493. (c) Kawaguchi, H.; Matsuo, T. J. Organomet. Chem. 2004, 689,
4228.
(2) (a) van der Linden, A.; Schaverien, C. J.; Meijboom, N.; Ganter, C.;
Orpen, A. G. J. Am. Chem. Soc. 1995, 117, 3008. (b) Matilainen, L.; Klinga,
M.; Leskela¨, M. J. Chem. Soc., Dalton Trans. 1996, 219. (c) Bei, X.;
Swenson, D. C.; Jordan, R. F. Organometallics 1997, 16, 3282. (d)
Tsukahara, T.; Swenson, D. C.; Jordan, R. F. Organometallics 1997, 16,
3303. (e) Kim, I.; Nishihara, Y.; Jordan, R. F.; Rogers, R. D.; Rheingold,
A. L.; Yap, G. P. A. Organometallics 1997, 16, 3314. (f) Fokken, S.;
Spaniol, T. P.; Okuda, J.; Sernetz, F. G.; Mu¨lhaupt, R. Organometallics
1997, 16, 4240. (g) Hustad, P. D.; Tian, J.; Coates, G. W. J. Am. Chem.
Soc. 2002, 124, 3614. (h) Oakes, D. C. H.; Kimberley, B. S.; Gibson, V.
C.; Jones, D. J.; White, A. J. P.; Williams, D. J. Chem. Commun. 2004,
2174. (i) Jones, D. J.; Gibson, V. C.; Green, S. M.; Maddox, P. J.; White,
A. J. P.; Williams, D. J. J. Am. Chem. Soc. 2005, 127, 11037.
(4) (a) Tjaden, E. B.; Swenson, D. C.; Jordan, R. F.; Petersen, J. L.
Organometallics 1995, 14, 371. (b) Repo, T.; Klinga, M.; Pietika¨inen, P.;
Leskela¨, M. Uusitalo, A.-M.; Pakkanen, T.; Hakala, K.; Aaltonen, P.;
Lo¨fgren, B. Macromolecules 1997, 30, 171. (c) Woodman, P. R.; Munslow,
I. J.; Hitchcock, P. B.; Scott, P. J. Chem. Soc., Dalton Trans. 1999, 4069.
(d) Corden, J. P.; Errington, W.; Moore, P.; Wallbridge, M. G. H. Chem.
Commun. 1999, 323. (e) Toupance, T.; Dubberley, S. R.; Rees, N. H.;
Tyrrell, B. R. Mountford, P. Organometallics 2002, 21, 1367. (f) Lavanant,
L.; Chou, T.-Y.; Chi, Y.; Lehmann, C. W.; Toupet, L.; Carpentier, J. F.
Organometallics 2004, 23, 5450. (g) Cuomo, C.; Strianese, M.; Cuenca,
T.; Sanz, M.; Grassi, A. Macromolecules 2004, 37, 7469. (h) Yao, Y.; Ma,
M.; Xu, X.; Zhang, Y.; Shen, Q.; Wong, W.-T. Organometallics 2005, 24,
4014.
10.1021/om050864z CCC: $33.50 © 2006 American Chemical Society
Publication on Web 01/06/2006

786 Organometallics, Vol. 25, No. 3, 2006
Chan et al.
of catalysts for the isospecific polymerization of 1-hexene5 and
styrene,6 the former in a living fashion.
Scheme 1
The focus on polyolefin catalysts supported by tridentate
alkoxide ligands has been less intense. Pioneered by Kakugo7
using the thio-bis(phenoxide) group, dianionic [O,L,O] ligands
can adopt fac or mer geometry depending on the bite angle and
flexibility of the backbone,8 and interesting copolymerization
studies have been reported.9 However, many of the resultant
catalysts are characterized by modest activities and fragile,
noninert ligand frameworks, and this is especially true for donor-
bis(alkoxide) derivatives.10 Hence the factors affecting catalyst
performance and polymerization behavior for tridentate systems
have yet to be elucidated. Kol and Goldschmidt have recently
described a class of bis(benzyl) group 4 complexes with
tetradentate ligands derived from amine-bis(aryloxide) plus a
sidearm O-, N-, or S-donor, which display excellent activities
in the polymerization of 1-hexene.11 The significance of the
pendant arm has been emphasized because it is proposed to play
a crucial role in determining the rates of the propagation and
termination processes, thought to remain attached to the catalytic
site, and is instrumental in achieving high activities. Indeed,
the analogous tridentate amine-bis(aryloxide) catalysts without
a sidearm donor have been observed to deactivate rapidly and
give only traces of oligomers.
We became attracted to the application of tridentate pyridine-
2,6-bis(aryloxide) groups as supporting ligands for polyolefin
catalysts. We envisaged that the pyridine-bis(aryloxide) unit
would provide a rigid and stable platform with chemically robust
and strongly chelating functionalities. Our preliminary report12
on the solvent-bound catalyst [Zr{(OAr)2py}Cl2(thf)] described
impressive activities for ethylene polymerization despite simi-
larities with Kol’s tridentate congeners. We now present a
detailed account of the preparation, characterization, and olefin
polymerization behavior of a series of Zr(IV) complexes
[Zr{(OAr)2py}Cl2(D)], where D represents a variety of O-donors
(ethers, ketones) and Cl[HPR3] moieties. Complexes bearing
different D groups are readily accessible and several crystal
structures have been determined, while the impact of the donor
upon the catalytic center and polymerization process has been
probed. Significantly, excellent activities are observed for
ethylene polymerization and copolymerization reactions, and
the polymer characterization data indicate that the polymeriza-
tion chain-transfer pathway is dominated by chain transfer to
Al.
Results and Discussion
Synthesis and Characterization. The symmetric tert-butyl-
bearing pyridine-2,6-bis(phenol) H2L1 was obtained in multi-
gram quantities by the Ni(dppe)Cl2-catalyzed coupling reaction
of the Grignard reagent derived from the substituted 2-bromo-
anisole with 2,6-dibromopyridine,13 followed by demethylation
with molten pyridine hydrochloride at 210 °C.14 On the basis
of established procedures for related group 4 complexes,2d,10a
we attempted to synthesize the [Zr(L1)Cl2] target by the slow
addition of Li2L1 to ZrCl4 in toluene and THF or Et2O at -78
°C. This yielded the solvated complexes [Zr(L1)Cl2(D)] [D )
thf (1), OEt2 (2)] in moderate yields (ca. 60%). However,
considerable care must be taken for this procedure in order to
avert the facile formation of the bis-ligand species [Zr(L1)2],
which becomes the major product if the rate of addition for
Li2L1 is excessive, if ketone/phosphine donors are used, or in
the absence of a strongly donating solvent/ligand. A more
convenient preparative route to complexes 1-5 involves the
treatment of Zr(CH2Ph)2Cl2 with H2L1 in toluene in the presence
of excess donor (Scheme 1). The importance of the donor group
is underscored by the observation that in their absence,
intractable yellow precipitates are produced. Rather than Zr-
coordinated PR3 species, the use of phosphine donors in this
reaction afforded 6-8, which contain three chloride ligands
bound to the anionic zirconium fragments and protonated
phosphine moieties, as demonstrated by the X-ray structural
determination of 7 (see below).
(5) Tshuva, E. Y.; Goldberg, I.; Kol, M. J. Am. Chem. Soc. 2000, 122,
10706.
(6) (a) Capacchione, C.; Proto, A.; Eberling, H.; Mu¨lhaupt, R.; Mo¨ller,
K.; Spaniol, T. P.; Okuda, J. J. Am. Chem. Soc. 2003, 125, 4964. (b)
Capacchione, C.; Manivannan, R.; Barone, M.; Beckerle, K.; Centore, R.;
Oliva, L.; Proto, A.; Tuzi, A.; Spaniol, T. P.; Okuda, J. Organometallics
2005, 24, 2971.
(7) Miyatake, T.; Mizunuma, K.; Seki, Y.; Kakugo, M. Makromol. Chem.,
Rapid Commun. 1989, 32, 1131.
(8) (a) Fokken, S.; Spaniol, T. P.; Kang, H.-C.; Massa, W.; Okuda, J.
Organometallics 1996, 15, 5069. (b) Nakayama, Y.; Watanabe, K.; Ueyama,
N.; Nakamura, A.; Harada A.; Okuda, J. Organometallics 2000, 19, 2498.
(c) Aihara, H.; Matsuo, T.; Kawaguchi, H. Chem. Commun. 2003, 2204.
(d) Trianionic [O,O,O] analogue: Matsuo, T.; Kawaguchi, H.; Sakai, M.
J. Chem. Soc., Dalton Trans. 2002, 2536. (e) Cyclometalated [O,N,C]
analogue: Kui, S. C. F.; Zhu, N.; Chan, M. C. W. Angew. Chem., Int. Ed.
2003, 42, 1628.
(9) (a) Miyatake, T.; Mizunuma, K.; Kakugo, M. Makromol. Chem.,
Macromol. Symp. 1993, 66, 203. (b) Sernetz, F. G.; Mu¨lhaupt, R.; Fokken,
S.; Okuda, J. Macromolecules 1997, 30, 1562.
(10) (a) Mack, H.; Eisen, M. S. J. Chem. Soc., Dalton Trans. 1998, 917.
(b) Shao, P.; Gendron, R. A. L.; Berg, D. J.; Bushnell, G. W. Organo-
metallics 2000, 19, 509. (c) Gauvin, R. M.; Osborn, J. A.; Kress, J.
Organometallics 2000, 19, 2944. (d) Manivannan, R.; Sundararajan, G.
Macromolecules 2002, 35, 7883.
(11) (a) Tshuva, E. Y.; Goldberg, I.; Kol, M.; Weitman, H.; Goldschmidt,
Z. Chem. Commun. 2000, 379. (b) Tshuva, E. Y.; Goldberg, I.; Kol, M.;
Goldschmidt, Z. Organometallics 2001, 20, 3017. (c) Tshuva, E. Y.;
Groysman, S.; Goldberg, I.; Kol, M.; Goldschmidt, Z. Organometallics 2002,
21, 662. (d) Groysman, S.; Goldberg, I.; Kol, M.; Genizi, E.; Goldschmidt,
Z. Organometallics 2004, 23, 1880. (e) Groysman, S.; Tshuva, E. Y.;
Goldberg, I.; Kol, M.; Goldschmidt, Z.; Shuster, M. Organometallics 2004,
23, 5291.
The bis(benzyl) Zr(IV) derivative of L1 can also be synthe-
sized, but a judicious choice of reaction solvent is required. Slow
addition of H2L1 to Zr(CH2Ph)4 in Et2O or pentane at -78 °C
resulted in the precipitation of the five-coordinate Zr(L1)(CH2Ph)2
(9) as a pale yellow solid. In contrast, employment of a solvent
in which 9 readily dissolves (e.g., toluene, THF) yielded
significant amounts of the octahedral product [Zr(L1)2]. All
1
complexes have been fully characterized by H, 13C, and 31P
(for 6-8) NMR spectroscopy. The broad 1H NMR resonances
for the ether and ketone donor groups are attribute to their
displacement/recoordination or restricted rotation. The pro-
1
tonation of the phosphine atom in 6-8 is evident in their H
(13) Holligan, B. M.; Jeffery, J. C.; Norgett, M. K.; Schatz, E.; Ward,
M. D. J. Chem. Soc., Dalton Trans. 1992, 3345.
(14) Dietrich-Buchecker, C.; Sauvage, J. P. Tetrahedron 1990, 46, 503.
(12) Chan, M. C. W.; Tam, K. H.; Pui, Y. L.; Zhu, N. J. Chem. Soc.,
Dalton Trans. 2002, 3085.

Group 4 Catalysts [Zr{(OAr)2py}Cl2(D)]
Organometallics, Vol. 25, No. 3, 2006 787
Table 1. Comparison of Selected Bond Lengths (Å) and
Angles (deg) for 3, 4, and 7
3
4
7
Zr1-N1
Zr1-O1
Zr1-O2
Zr-Cl
2.428(2)
1.954(2)
1.959(2)
2.427(1)
2.439(1)
2.206(2)
2.407(4)
1.961(4)
1.960(4)
2.441(2)
2.406(2)
2.250(4)
2.465(3)
1.967(2)
1.956(2)
2.520(1), 2.466(1), 2.437(1)
Zr-O(ketone)
O1-Zr1-O2
Cl1-Zr1-Cl2
156.3(1)
96.14(4)
155.0(1)
97.19(7)
157.8(1)
93.17(4)
(ca. 6.0 to 7.0 ppm) and 31P (-1.7 to -18.8 ppm) NMR spectra
1
from the appearance of JPH coupling (488-526 Hz).
Crystal Structures: Comparison of Different Donor
Groups. The molecular structures of complexes 3, 4, and 7
(Table 1 and Figure 1) have been determined by X-ray
crystallography and can be compared with the previously
reported structures of 1 and 2.12 The pyridine-2,6-bis(phenoxide)
unit L1 chelates to the distorted octahedral Zr core in 3, 4, and
7 in a tridentate meridional manner, and its nonplanarity is
manifested in dihedral angles of ca. 40-50° between the
aromatic rings. It is of interest to correlate the Zr-O(donor)
bond lengths in these structures. The respective distances in 1-4
(2.247(3), 2.295(2), 2.206(2), and 2.250(4) Å) are elongated
relative to that in the seminal metallocene cation [Cp2ZrMe-
(thf)]+ (2.122(14) Å)15 but noticeably shorter than those in
related catalysts such as Kol’s amine-bis(aryloxide) derivative
supported by a sidearm methoxy donor (Zr-OMe 2.447(3) Å)11c
and Okuda’s complexes bearing tridentate Cp-amido-methoxy
donor ligands (Zr-OMe 2.330(4) and 2.375(2) Å).16 The
molecular structure of 7 confirms the anionic nature of the Zr
moiety and the absence of a Zr-P interaction. The Zr-Cl bond
lengths for the trans chloride groups (2.520(1) and 2.466(1) Å)
are partially longer than for the cis chlorides in 3 and 4 (ca.
2.41-2.44 Å), presumably because these π-donors are compet-
ing for the same Zr d-orbital in the former case. Of course, cis
configurations of the chloride ligands in these structures are
important for their deployment as polyolefin catalysts. The
crystal structure of the bis-ligand complex [Zr(L1)2] has also
been determined (see Supporting Information). The symmetric
structure belongs to the tetragonal crystal system and the
octahedral molecule is highly compact and spherical, which may
explain the high tendency for its formation.
Polymerization Studies: Trends in Ethylene Polymeriza-
tion. The 1/MAO system displays excellent activities for
ethylene polymerization, and an investigation into its catalytic
characteristics was undertaken (Table 2). The highly active
nature of 1 is illustrated by the appearance of exotherms (up to
∼60 °C) after ca. 3 min. Catalytic rates are noticeably reduced
at 1 and 65 °C, although the latter may be influenced by
diffusion-controlled factors. The polymerization efficiency of
1 is enhanced after the appearance of the exotherm (6 min: 7030
g mmol-1 h-1), and an activity of 7880 g mmol-1 h-1 is
observed using 2000 equiv of MAO, corresponding to a turnover
frequency value of 2.81 × 105 h-1 atm-1
.
Figure 1. Perspective views of (from top) 3, 4, and 7 (30%
probability ellipsoids).
Polymer Characterization: Impact of Polymerization
Conditions and Insight into Chain-Transfer Mechanism.
GPC analysis of the polymer samples produced by 1/MAO has
been performed (Table 2 and Figure 2). In general, the materials
exhibit low molecular weights (Mpk 1000-1800) and broad
polydispersities (Mw/Mn 11-22; partly as a result of high MW
tails). The exceptions are the polymers from the 1 (high MW
1
and distinctly bimodal) and 65 (Mw/Mn 1.4) °C runs. H and
13C NMR spectroscopy has also been employed to characterize
the polymers, all of which are highly linear polyethylene (see
Supporting Information for examples). Saliently, only resonances
for saturated methyl chain-end groups are observed (2.2-28.5
methyls per 1000 C), and the levels of vinyl hydrogens
(15) Jordan, R. F.; Bajgur, C. S.; Willett, R.; Scott, B. J. Am. Chem.
Soc. 1986, 108, 7410.
(16) Amor, F.; Butt, A.; du Plooy, K. E.; Spaniol, T. P.; Okuda, J.
Organometallics 1998, 17, 5836.

788 Organometallics, Vol. 25, No. 3, 2006
Table 2. Ethylene Polymerization Data for 1/MAOa
Chan et al.
catalyst
(µmol)
MAO
(mmol/equiv)
temp
(°C)
time
(min)
yield
(g)
Tm
(°C)
chain-end gpd
(methyl, vinyl)
c
c
c
activityb
Mw
Mn
Mw/Mn
Mpk
1800
4.72
4.72
4.72/1000
4.72/1000
20
1
2
2
0.92
0.23
5850
1450
129
134
46 000
220 000
2100
17 000
21.7
13.2
11.6, 0
2.2, 0e
i: 24 000,
ii: 432 000
1000
4.72
4.72
3.15
4.72/1000
4.72/1000
6.30/2000
65
20
20
2
0.31
3.32
2.44
1990
7030
7880
111
127
125
1100
36 000
16 000
800
1800
1400
1.4
19.8
11.4
28.5, 0f
13.3, 0
18.4, 0e
6g
5g
1500
1000
a Conditions: 50 mL of toluene, 1 atm pressure of ethylene. b Activity in g(polymer) (mmol catalyst)-1 h-1 c Determined by GPC at 135 °C using
.
polyethylene standards. d Results from 13C NMR analysis, given per 1000 carbon atoms. e Results from 1H NMR analysis. f 1H NMR analysis gave 29.6
methyl and 0.1 vinyl chain ends per 1000 carbon atoms. g An exotherm was observed.
in propagation and chain-transfer rates during polymerization
are less significant for higher Al concentrations, and (2) lower
MW material, as the chain-transfer rate to Al would increase
to afford shorter polymer chains.
The GPC data imply that the rate of chain transfer to Al alters
according to temperature (Table 2). At 1 °C, the chain-transfer
rate is slow and high MW material is produced (see following
section for explanation of bimodality). Higher temperatures
should yield greater propagation and chain-transfer rates,
culminating in enhanced activities and decreased MW, respec-
tively (e.g., experiments accompanied by an exotherm display
lower MW). At 65 °C, we suggest that the reduction in activity
may partly be caused by the consumption of Al species at
elevated chain-transfer rates. In addition, we note that the GPC
and NMR data of the 65 °C run, especially the narrow
Figure 2. GPC traces of PE samples prepared by 1/MAO (refer
polydispersity (1.4) and high level of saturated chain ends (∼30
to Table 2).
per 1000 C), show distinct similarities with those for the
remarkably efficient “Fe-catalyzed polyethylene chain growth
corresponding to unsaturated chain ends are undetectable/
negligible (or extremely low in the case of the 65 °C run). With
reaction on Zn” reported by Gibson and co-workers.22
Addition of Trimethylaluminum (TMA) to 1/MAO: Dem-
onstrating Chain Transfer to Al. To gain further evidence
for the chain transfer to Al pathway, we have studied the
catalytic properties of 1/MAO in the presence of varying
amounts of TMA as chain-transfer agent and characterized the
resultant polymer samples (Table 3). Polymerization conditions
(0.5 °C, 100 equiv of MAO) have been carefully chosen to gave
high MW materials in the absence of TMA, and the Tm values
are clearly higher than for runs at 20 °C. Respectable activities
are observed, and a downward trend is apparent for increasing
TMA concentrations. While insoluble polymers are produced
in the absence of and for 100 equiv of added TMA, the
remaining materials have been analyzed by GPC (Figure 3).
The polymer for 200 equiv of TMA is bimodal in nature, with
a greater proportion in the higher MW fraction. For 500 equiv
of TMA, the bimodality remains, but the lower MW fraction is
now dominant. This trend is continued for 1000 equiv of TMA,
where only the low MW portion at Mpk 11 000 is detected.
regard to the polymerization chain-transfer mechanism, the
absence of unsaturated Vinyl chain ends strongly indicates that
the normally preValent â-H transfer reactions to the metal or
monomer are insignificant and signify that chain transfer to Al
is Vastly dominant. It is interesting to note that the unusual chain
transfer to Al pathway, which has been reported for group 4
metallocenes17 and more recently for post-metallocene sys-
tems,18,19 typically occurs concomitantly with â-H transfer and
is rarely observed as the solitary chain-transfer process.20,21
The chain transfer to Al mechanism, which is dependent upon
the alkyl Al concentration, can be invoked (rather than multiple
active sites) to explain the broad polydispersities. Namely, the
expected change in the concentration of Al species during
polymerization would lead to a variable chain-transfer rate with
time, and hence a broadening of the MW distribution. Further-
more, increasing the MAO concentration to 2000 equiv (Figure
2) has resulted in (1) a narrower Mw/Mn value, since changes
1
Chain-end group analysis by H NMR spectroscopy reveals
(17) (a) Chien, J. C. W.; Wang, B.-P. J. Polym. Sci. A 1990, 28, 15. (b)
Resconi, L.; Piemontesi, F.; Granciscono, G.; Abis, L.; Fiorani, T. J. Am.
Chem. Soc. 1992, 114, 1025. (c) Mogstad, A.-L.; Waymouth, R. M.
Macromolecules 1992, 25, 2282. (d) Leino, R.; Luttikhedde, H. J. G.;
Lehmus, P.; Wile´n, C.-E.; Sjo¨holm, R.; Lehtonen, A.; Seppa¨la¨, J. V.;
Na¨sman, J. H. Macromolecules 1997, 30, 3477. (e) Byun, D.-J.; Kim, S.
Y. Macromolecules 2000, 33, 1921.
(18) (a) Small, B. L.; Brookhart, M. Bennett, A. M. A. J. Am. Chem.
Soc. 1998, 120, 4049. (b) Britovsek, G. J. P.; Bruce, M.; Gibson, V. C.;
Kimberley, B. S.; Maddox, P. J.; Mastroianni, S.; McTavish, S. J.; Redshaw,
C.; Solan, G. A.; Stro¨mberg, S.; White, A. J. P.; Williams, D. J. J. Am.
Chem. Soc. 1999, 121, 8728.
(19) (a) Murtuza, S.; Casagrande, O. L., Jr.; Jordan, R. F. Organometallics
2002, 21, 1882. (b) Michiue, K.; Jordan, R. F. Macromolecules 2003, 36,
9707. (c) Michiue, K.; Jordan, R. F. Organometallics 2004, 23, 460.
(20) (a) Scollard, J. D.; McConville, D. H.; Vittal, J. J.; Payne, N. C. J.
Mol. Catal. A 1998, 128, 201. (b) Tsubaki, S.; Jin, J.; Sano, T.; Uozumi,
T.; Soga, K. Macromol. Chem. Phys. 2001, 202, 1757.
saturated methyl fragments exclusively, the level of which
consistently increases for higher TMA concentrations. None of
the samples contained observable levels of hydrogens for
unsaturated vinyl end groups. Furthermore, the samples exhibit
a well-resolved triplet signal for the chain-end methyl group,
suggesting that significant amounts of short chain branching is
unlikely. These obserVations are entirely consistent with chain
transfer to Al as the sole chain-transfer mechanism during
polymerization.
The bimodal characteristics of the polymers are tentatively
rationalized by the following: (1) the initial rate of chain transfer
(22) (a) Britovsek, G. J. P.; Cohen, S. A.; Gibson, V. C.; van Meurs, M.
J. Am. Chem. Soc. 2004, 126, 9913. (b) van Meurs, M.; Britovsek, G. J. P.;
Gibson, V. C.; Cohen, S. A. J. Am. Chem. Soc. 2005, 127, 9913.
(21) Saito, J.; Tohi, Y.; Matsukawa, N.; Mitani, M.; Fujita, T. Macro-
molecules 2005, 38, 4955.

Group 4 Catalysts [Zr{(OAr)2py}Cl2(D)]
Organometallics, Vol. 25, No. 3, 2006 789
Table 3. Polymerization Data for 1/MAO in the Presence of Trimethylaluminum (TMA)a
catalyst
(µmol)
TMA
(mmol/equiv)
yield
(g)
Tm
(°C)
chain-end gpe
(methyl, vinyl)
c
c
c
Al/Zr
activityb
Mw
Mn
Mw/Mn
Mpk
8.49
8.34
8.18
0
100
200
300
0.83
0.82
0.53
585
595
390
134
136
137
d
d
f
0.834/100
1.636/200
1.2, 0
1.7, 0
668 000
261 000
14 000
26 000
9800
25.7
26.6
2.5
i: 609 000,
ii: 12 000
i: 13 000,
ii: 568 000
11 000
8.02
8.02
4.010/500
600
0.28
0.39
205
290
136
133
3.2, 0
8.020/1000
1100
5400
f
a Conditions: 50 mL of toluene, 100 equiv of MAO, 1 atm pressure of ethylene, 0.5 °C, polymerization time 10 min. b Activity in g(polymer) (mmol
1
catalyst)-1 h-1
.
c Determined by GPC at 135 °C using polyethylene standards. d Polymer was insoluble under analysis conditions. e Results from H NMR
analysis, given per 1000 carbon atoms. f Spectrum was too broad to allow integration.
â-diketiminato ligands have been isolated.25 Nevertheless, highly
active polyethylene catalysts derived from cationic iron and
cobalt pyridine-2,6-bis(imino) complexes bearing thf and CH3CN
donors have been described.26 In this work, we have prepared
a series of Zr(IV) catalysts containing different O-donors and
Cl[HPR3] fragments, and comparative polymerization experi-
ments have been carried out simultaneously using the same batch
of MAO in order to probe the role of the donor group and
ascertain whether the donor remains bound to the Zr core during
catalysis and replaces the function of the “sidearm donor”
reported by Kol.11
Although variations in the activities of 1-8 are observed
(Table 4), differences within the respective ketone and Cl[HPR3]
series are also evident, and no distinct trends are apparent.
Characterizations of the polymer samples are more informa-
tive: the Tm values of all materials fall within a narrow range.
GPC analysis of 1-5 (Figure 4) reveals low MW materials,
the properties and profiles of which are very similar (e.g., Mw/
Mn 3.7-4.5). 1H NMR analysis also indicates that the polymers
obtained from 1-5 are comparable, and the levels of methyl
chain-end groups correspond closely (11.8-13.2 methyls per
1000 C). Like in Tables 2 and 3, none of the samples exhibit
resonances for vinyl hydrogens, which signifies the absence of
unsaturated chain ends and the dominance of the chain transfer
to Al pathway (over â-H transfer). On the basis of Table 4 and
the polymer characterization data, we propose that (1) the
influence of the donor group during polymerization is minimal,
(2) the same active species (i.e., [(L1)ZrR]+) is generated by
1-8/MAO, and (3) the donor group is sequestered by the MAO
cocatalyst26 and does not actively participate in the polymeri-
zation reaction. We attribute the apparent differences in activities
for 1-8 to slight variations in catalyst as well as Al concentra-
tions in each run, while the initiation period for each catalyst
may also fluctuate.
Figure 3. Addition of TMA to 1/MAO: effects upon MW
distribution (refer to Table 3).
to Al is highest and yields the lower MW fraction; (2) as the
Al species is consumed and its concentration quickly depletes
and becomes limiting, abrupt reduction in the rate of chain
transfer to Al occurs and results in formation of the higher MW
portion; (3) at 0.5 °C, the Al-chain-transfer rate can also drop
as the catalyst becomes embedded in the polymer. Like the 2000
MAO experiment, the 1000 equiv of TMA run yields narrower
polydispersity and a lower MW polymer. The general trend of
declining activities at greater TMA concentrations can be
attributed to coordination of TMA to the catalytically active
species to generate [(L1)ZrR(µ-Me)AlMe2]+, suppressing the
propagation rate. The exception is the 1000 equiv of TMA run;
we propose that enhancement of the chain-transfer rate at such
high Al concentrations may overcompensate activity-wise for
the diminishing effects of TMA coordination. Overall, the Al-
chain-transfer characteristics of 1 appear to bear greater
resemblance to the Ti diamide,20 Fe pyridine-2,6-bis(imine),18
and Zr bis(phenoxyimine)21 catalysts rather than the Ti tris-
(pyrazolyl)borate19 system. Namely, in the case of 1, we believe
that the dominance of the chain transfer to Al pathway is related
to the creation of a highly accessible active site after loss of a
labile donor group (see below), in a manner analogous to that
reported for the Ti diamide system.20
Homo- and Copolymerization Studies on 1 with Different
Cocatalysts. Catalyst 1 was selected for large-scale ethylene
polymerization and copolymerization experiments with pro-
pylene and norbornene using MAO or iBu3Al/Ph3CB(C6F5)4 as
the cocatalyst (Table 5). For ethylene polymerization, an
excellent activity of 5700 g mmol-1 h-1 is observed for 1/MAO
(considering the Al/Zr ratio is only 250), although the 1/iBu3Al/
Ph3CB(C6F5)4 system displays a substantially superior activity
of 36 590 g mmol-1 h-1 (at a reduced catalyst concentration).
Role of Donor Group. The excellent activities for the
1/MAO system are intriguing given the presence of the thf
ligand at the oxophilic Zr(IV) center. This is in stark contrast
to the well-established suppression in catalytic efficiency for
the solvated [Cp2ZrMe(L)]+ cations (L ) thf, amine).23 Reduced
activities for the living polymerization of 1-hexene by coordi-
natively unsaturated chelating diamide Ti(IV) derivatives have
been attributed to binding of the toluene solvent at the cationic
active site,24 while thf-solvated Sc(III) complexes bearing related
i
In general, the use of the Bu3Al/borate cocatalyst leads to
elevated homo- and copolymerization activities and slightly
lower MW materials.
(25) (a) Lee, L. W. M.; Piers, W. E.; Elsegood, M. R. J.; Clegg, W.;
Parvez, M. Organometallics 1999, 18, 2947. (b) Hayes, P. G.; Piers, W.
E.; R. McDonald, J. Am. Chem. Soc. 2002, 124, 2132.
(26) Britovsek, G. J. P.; Gibson, V. C.; Spitzmesser, S. K.; Tellman, K.
P.; White, A. J. P.; Williams, D. J. J. Chem. Soc., Dalton Trans. 2002,
1159.
(23) Jordan, R. F. AdV. Organomet. Chem. 1991, 32, 325.
(24) Scollard, J. D.; McConville, D. H. J. Am. Chem. Soc. 1996, 118,
10008.

790 Organometallics, Vol. 25, No. 3, 2006
Table 4. Comparison of Ethylene Polymerization Data for Catalysts Bearing Different Donor Groupsa
Chan et al.
catalyst
(µmol)
yield
(g)
Tm
(°C)
chain-end gpe
(methyl, vinyl)
c
c
c
activityb
Mw
Mn
Mw/Mn
Mpk
1 (5.66)
2 (5.66)
3 (5.76)
4 (5.70)
5 (5.86)
6 (5.78)
7 (5.72)
8 (5.70)
0.97
0.70
0.71
0.52
0.98
1.03
0.82
0.94
3450
2580
2050
2010
2990
3535
3170
3215
126
127
126
130
127
125
126
125
8000
9700
7600
8000
8200
2000
2100
2000
2200
2100
4.0
4.5
3.7
3.7
3.9
1800
1700
1800
1800
1900
13.2, 0
12.0, 0
12.6, 0
12.8, 0
11.8, 0
d
d
d
d
d
d
a Conditions: 35 mL of toluene, 1000 equiv of MAO, 1 atm pressure of ethylene, 20 °C, polymerization time 3 min. b The reported activity, in g(polymer)
(mmol catalyst)-1 h-1, is the mean value of 3 separate sets of polymerization runs for 1-8 using the same batch of MAO. c Determined by GPC at 135 °C
1
using polyethylene standards. d Not recorded. e Results from H NMR analysis, given per 1000 carbon atoms.
Table 5. Homo- and Copolymerization Results for 1a
activityb
Mv
notes
c
reaction
yield (g)
1/MAO
PE
2.37
0.89
0.44
3.05d
6.54
3.32
5700
2150
530
36 590
15 700
7970
8.03 × 105
3.29 × 105
4.50 × 105
1.93 × 105
2.21 × 104
1.83 × 105
T
m 137 °C
EPR
COC
PE
EPR
COC
<5 mol % C3e
T
T
m 132 °C
m 134 °C
1/iBu3Al/Ph3CB(C6F5)4
25.4 mol % C3f
Tm 130 °C
a Conditions: 250 mL of toluene, 5 µmol of catalyst, cocat. MAO (250 equiv) or Bu3Al/Ph3CB(C6F5)4 (50/1.2 equiv, respectively, vs 1), 1 atm olefin
feed, 25 °C, PE (ethylene polymerization, 5 min): C2 ) 100 L h-1, EPR (ethylene-propylene copolymerization, 5 min): C2/C3 ) 100/100 L h-1, COC
i
(ethylene-norbornene copolymerization, 10 min): C2 ) 50 L h-1 and NB ) 1 g. b Activity in g(polymer) (mmol catalyst)-1 h-1 c Determined by intrinsic
.
0.7
viscosity [η] of polymer at 135 °C in decalin and calculated using [η] ) 6.2 × 10-4Mv
.
d 1 µmol of catalyst. e Estimated by IR analysis (polymer was
insoluble under H NMR analysis conditions). f Determined by H NMR analysis.
1
1
Ph3CB(C6F5)4 exhibit poor NB incorporation in ethylene-
norbornene copolymerization, as implied by the high PE-like
Tm values. We note that Fujita et al. have investigated the
i
contrasting effects of the MAO and Bu3Al/Ph3CB(C6F5)4
cocatalysts upon the reactivity of bis(phenoxyimine) Zr catalysts,
with the latter showing suppressed activities.3a,29 The reasons
for the reversal of this trend for catalyst 1 and the superior
performance of the 1/iBu3Al/Ph3CB(C6F5)4 system are currently
unclear, although at high Al/MAO levels, it is apparent that
the coordination of Al species to the catalytic site may reduce
activities.
Concluding Remarks
Figure 4. GPC traces of PE samples prepared by 1-5/MAO (refer
to Table 4).
Despite reports regarding the poor catalytic activities of group
4 complexes supported by tridentate amine-bis(aryloxide)
ligands, we have established that the related pyridine-2,6-bis-
(aryloxide) Zr system can exhibit exceptional activities for olefin
polymerization. Compared to aliphatic alkoxide analogues, the
tridentate pyridine-2,6-bis(aryloxide) moiety is a rigid and
chemically inert ligand framework and is expected to be more
resistant to alkyl aluminum-induced catalyst decomposition and
rearrangement reactions. It is also pertinent to refer to calcula-
tions by Musaev and Morokuma30 on the related 2,2′-thio-bis-
(4-methyl-6-tert-butylphenoxide) Ti complexes,7,9 which pre-
dicted that strong binding by the central chelating unit in
tridentate [O,L,O] catalysts, like the pyridine group in [Zr(L1)-
Cl2(thf)] (1), would lead to lower ethylene insertion barriers
and hence enhanced activities.
Notable results have been obtained in ethylene-propylene
copolymerization reactions.27 The 1/iBu3Al/Ph3CB(C6F5)4 sys-
tem exhibits an impressive activity of 15 700 g mmol-1 h-1
,
and a poly(ethylene-co-propylene) (EPR) material with good
C3 content (25.4 mol % C3) is produced. The activity and
degree of C3 incorporation can be compared with the per-
formance of the Zr bis(phenoxyimine)/MAO and -/iBu3Al/
Ph3CB(C6F5)4 systems and that of Cp2ZrCl2/MAO (22 000,
600-8000, and 22 000 g mmol-1 h-1, respectively; 10.1, 20.7-
23.7, and 25.6 mol % C3, respectively) under similar
conditions,3a,28 although the level of C3 incorporation is clearly
inferior to that of Me2X(3-RCp)(9-Flu)ZrCl2/MAO (>50 mol
i
% C3; X ) C, Si; R ) Me, Pr).27d In contrast, the 1/MAO
system yields decreased activities and very low C3 content, the
latter indicated by IR analysis and the appearance of Tm (132
°C) for the resultant polymer. Both 1/MAO and 1/iBu3Al/
Several of the [Zr(L1)Cl2(donor)] derivatives have been
structurally characterized, and the importance of the donor group
with respect to complex formation, isolation, and solubility has
been indicated. Careful investigation of the behavior of catalysts
(27) (a) Kravchenko, R.; Waymouth, R. M. Macromolecules 1998, 31,
1. (b) Galimberti, M.; Piemontesi, F.; Mascellani, N.; Camurati, I.; Fusco,
O.; Destro, M. Macromolecules 1999, 32, 7968. (c) Wang, W.-J.; Zhu, S.;
Park, S.-J. Macromolecules 2000, 33, 5770. (d) Fan, W.; Leclerc, M. K.;
Waymouth, R. M. J. Am. Chem. Soc. 2001, 123, 9555.
(28) Ishii, S.; Saito, J.; Matsuura, S.; Suzuki, Y.; Furuyama, R.; Mitani,
M.; Nakano, T.; Kashiwa, Fujita, T. Macromol. Rapid Commun. 2002, 23,
693.
(29) Makio, H.; Fujita, T. Bull. Chem. Soc. Jpn. 2005, 78, 52.
(30) (a) Froese, R. D. J.; Musaev, D. G.; Matsubara, T.; Morokuma, K.
J. Am. Chem. Soc. 1997, 119, 7190. (b) Froese, R. D. J.; Musaev, D. G.;
Morokuma, K. Organometallics 1999, 18, 373. (c) Vyboishchikov, S. F.;
Musaev, D. G.; Froese, R. D. J.; Morokuma, K. Organometallics 2001, 20,
309.

Group 4 Catalysts [Zr{(OAr)2py}Cl2(D)]
Organometallics, Vol. 25, No. 3, 2006 791
of a suitable donor solvent/ligand (e.g., THF). Data for [Zr(L1)2]:
1H NMR (300 MHz, C6D6): 1.13 (s, 18H, tBu), 2.32 (s, 6H, Me),
7.18-7.23 (m, 1H, py-H4), 7.25 (s, 2H, Ar), 7.33-7.36 (m, 4H,
py-H3,5 and Ar). 13C NMR (75 MHz, C6D6): 21.18 (Me), 29.61
(CMe3), 34.83 (CMe3); methine carbons: 123.26, 128.93, 130.50,
139.08; 4° carbons: 125.76, 126.63, 138.18, 156.52, 156.80. EI-
MS (+ve, m/z): 894 (100%) [M+].
General Synthetic Procedure for Complexes 3-8. A solution
of H2L1 (0.200 g, 0.50 mmol) in toluene (35 mL) was slowly added
at -78 °C to Zr(CH2Ph)2Cl2(OEt2)(dioxane)0.5 (0.246 g, 0.53 mmol)
in toluene (25 mL) in the presence of excess ketone (5-10 mmol)
or phosphine (ca. 20 mmol). The resultant pale yellow solution
was stirred for 1 h at -78 °C and for 12 h at room temperature.
Filtration and concentration of this mixture gave a pale yellow solid,
which was recrystallized from toluene to yield yellow crystals.
bearing different O-donors and Cl[HPR3] groups and analysis
of the resultant polymers suggest that a single active species is
responsible and the donor group is unlikely to perform an active
role during the polymerization process. While the activity of
1/MAO is among the highest reported for non-Cp aryloxide or
alkoxide derivatives at such MAO concentrations, the best
activities in this work are reserved for the 1/iBu3Al/Ph3CB-
(C6F5)4 system. Catalytic efficiencies of 36 590 and 15 700 g
mmol-1 h-1 are observed for ethylene polymerization and
ethylene-propylene copolymerization, respectively, with the
latter incorporating a respectable degree of propylene (25.4 mol
%). The polymerization characteristics of 1/MAO have been
studied by modification of reaction conditions such as temper-
ature, time, and particularly Al concentration (with MAO
cocatalyst and TMA chain-transfer agent). Polymer character-
[Zr(L1)Cl2(OdCPhMe)] (3). Acetophenone (1 mL, 8.6 mmol)
1
ization by GPC and H and 13C NMR spectroscopy clearly
was used. Yield: 0.22 g, 61%. 1H NMR (400 MHz, CD2Cl2): 1.43
signifies that 1/MAO constitutes a rare catalytic system where
the conventional â-H transfer processes to the metal/monomer
are shut down and the chain-transfer mechanism is overwhelm-
ingly (or exclusively) dominated by chain transfer to Al.
t
(s, 18H, Bu), 2.32 (s, 6H, Me), 2.47 (br, 3H, MeCdO), 7.13 (s,
2H, Ar), 7.18 (s, 2H, Ar), 7.32 (br, 2H, PhCdO), 7.62 (t, 1H, J )
7.4 Hz), 7.67 (br, 2H, PhCdO), 7.84 (d, J ) 7.9 Hz, 2H, py-H3,5),
8.07 (t, J ) 7.9 Hz, 1H, py-H4). 13C NMR (126 MHz, CD2Cl2):
20.9 (MeCdO), 29.7 (CMe3), 35.0 (CMe3); methine carbons: 124.3,
129.0, 129.8, 130.0, 130.9, 137.1, 140.7; 4° carbons: 127.7, 129.3,
Experimental Section
137.5, 154.1, 160.0. EI-MS (+ve, m/z): 563 (100%) [M+
-
General Considerations. All reactions were performed under a
nitrogen atmosphere using standard Schlenk techniques or in a
Braun drybox. All solvents were appropriately dried and distilled,
then degassed prior to use. 1H and 13C NMR spectra were recorded
on a Bruker 500 DRX, 400 DRX, or 300 FT-NMR spectrometer
(ppm) using Me4Si as internal standard. 31P NMR spectra were
recorded on the Bruker 400 DRX and referenced to external 85%
H3PO4. Peak assignments were based on combinations of DEPT-
135 and 2-D 1H-1H, 13C-1H, and NOE correlation NMR experi-
ments. Mass spectra (EI) were obtained on a Finnigan MAT 95
mass spectrometer. Elemental analyses were performed by Medac
Ltd., UK. For polymer analysis, melting points were determined
PhC(O)Me]. Anal. Calcd for C35H39NO3Cl2Zr‚0.5C7H8 (729.90):
C, 63.35; H, 5.94; N, 1.92. Found: C, 63.08; H, 5.93; N, 1.78.
[Zr(L1)Cl2(OdCPh2)] (4). Benzophenone (1.8 g, 9.9 mmol) was
used. Yield: 0.26 g, 65%. 1H NMR (400 MHz, CD2Cl2): 1.44 (s,
t
18H, Bu), 2.30 (s, 6H, Me), 6.93 (s, 2H, Ar), 7.15 (s, 2H, Ar),
7.24 (br m, 4H, Ph2CdO), 7.53 (br m, 4H, Ph2CdO), 7.57 (br m,
2H, Ph2CdO), 7.60 (d, J ) 7.9 Hz, 2H, py-H3,5), 7.85 (t, J ) 7.8
Hz, 1H, py-H4). 13C NMR (126 MHz, CD2Cl2): 20.9 (Me), 29.8
(CMe3), 35.0 (CMe3); methine carbons: 123.9, 128.4, 129.7, 129.8,
132.6, 135.3, 140.2; 4° carbons: 127.7, 129.1, 137.4, 153.9, 159.7.
EI-MS (+ve, m/z): 563 (100%) [M+ - Ph2CdO]. Anal. Calcd for
C40H41NO3Cl2Zr (745.90): C, 64.41; H, 5.54; N, 1.88. Found: C,
64.79; H, 5.29; N, 2.04.
1
by differential scanning calorimetry on a Perkin-Elmer DSC7. H
and 13C NMR data for polymer samples were obtained in p-xylene-
d10 at 110 °C and 1,2,4-trichlorobenzene/C2D2Cl4 at 130 °C,
respectively. Gel permeation chromatographs were obtained on a
Waters 150CV [columns supplied by Shodex (807, 806, and 804)]
at 135 °C using polyethylene standard reference material NBS1484a.
Methylaluminoxane (MAO, 10 wt % solution in toluene) was
purchased from Aldrich and used as received. Ethylene (BOC,
polymer grade) was passed through Drierite and P2O5. By following
the synthetic procedure for Zr(CH2Ph)2Cl2(OEt2)2,31 the complex
Zr(CH2Ph)2Cl2(OEt2)(dioxane)0.5 was isolated as an orange crystal-
[Zr(L1)Cl2(OdCNpMe)] (5). 2-Acetonaphthone (NpC(O)Me,
1
0.84 g, 4.9 mmol) was used. Yield: 0.24 g, 62%. H NMR (400
MHz, CD2Cl2): 1.44 (s, 18H, tBu), 2.31 (s, 6H, Me), 2.59 (br, 3H,
MeCdO), 7.15 (s, 2H, Ar), 7.16 (s, 2H, Ar), 7.56 (t, J ) 7.2 Hz,
1H, Np), 7.58 (br, 1H, Np), 7.67 (t, J ) 7.6 Hz, 1H, Np), 7.70 (br,
1H, Np), 7.80 (br, 2H, Np), 7.85 (d, J ) 7.9 Hz, 2H, py-H3,5), 8.07
(t, J ) 7.9 Hz, 1H, py-H4), 8.35 (br, 1H, Np). 13C NMR (126 MHz,
CD2Cl2): 20.9 (Me), 29.8 (CMe3), 35.0 (CMe3); methine carbons:
124.3, 124.4, 127.6 (br), 128.0, 128.9 (br), 129.8, 130.0, 130.6 (br),
131.0 (br), 135.0 (br), 140.7; 4° carbons: 127.7, 129.3, 137.6, 154.2,
160.1. EI-MS (+ve, m/z): 563 (100%) [M+ - NpC(O)Me]. Anal.
Calcd for C39H41NO3Cl2Zr (733.89): C, 63.83; H, 5.63; N, 1.91.
Found: C, 63.65; H, 5.63; N, 1.96.
1
line solid and characterized by H NMR spectroscopy to contain
the O-donor ligands in the stoichiometry shown. Zr(CH2Ph)4 was
prepared according to the published method.32 The syntheses of
ligand H2L1 and complexes 1 and 2 were previously given.12
Improved Synthesis of [Zr(L1)Cl2(thf)] (1). A solution of H2L1
(0.345 g, 0.86 mmol) in toluene (15 mL) and THF (8 mL) was
slowly added at -78 °C to Zr(CH2Ph)2Cl2(OEt2)(dioxane)0.5 (0.400
g, 0.86 mmol) in toluene (15 mL) and THF (8 mL). The resultant
yellow solution was stirred for 1 h at -78 °C and for 12 h at room
temperature. Filtration and concentration of this mixture gave a
pale yellow solid, which was recrystallized from toluene to yield
large yellow crystals. Yield: 0.45 g, 77%. All characterization data
were identical to those previously reported.
[Zr(L1)Cl3][HPMe3] (6). Trimethylphosphine (3 mL, 29 mmol)
was used. Yield: 0.21 g, 57% yield. 1H NMR (400 MHz,
CD2Cl2): 1.54 (s, 18H, tBu), 1.78 (dd, J ) 15.2, 4.5 Hz, 9H, PCH3),
2.30 (s, 6H, Me), 6.14 (br virtual s, HP), 7.08 (s, 2H, Ar), 7.22 (s,
2H, Ar), 7.73 (d, J ) 7.9 Hz, 2H, py-H3,5), 7.97 (t, J ) 7.9 Hz,
1H, py-H4). 13C NMR (126 MHz, CD2Cl2): 5.8 (d, 1JPC ) 54 Hz,
PCH3), 20.6 (Me), 29.8 (CMe3), 34.7 (CMe3); methine carbons:
123.7, 129.2, 129.5, 139.6; 4° carbons: 127.6, 127.8, 136.6, 154.5,
1
159.2. 31P[1H] NMR (CD2Cl2): -4.90 (d, JPH ) 511 Hz). EI-MS
(+ve, m/z): 563 (100%) [M+ - (PMe3H)Cl]. Anal. Calcd for
C30H41NO2Cl3PZr (676.21): C, 53.29; H, 6.11; N, 2.07. Found:
C, 53.37; H, 6.00; N, 2.26.
[Zr(L1)2] was isolated as the major product from the original
reaction procedure (slow addition of Li2L1 to ZrCl4 in toluene at
-78 °C)12 if the addition of Li2L1 was accelerated or in the absence
[Zr(L1)Cl3][HPEt3] (7). Triethylphosphine (3 mL, 20.3 mmol)
was used. Yield: 0.23 g, 60%. 1H NMR (400 MHz, CD2Cl2): 1.21
(dt, J ) 19.9, 7.7 Hz, 9H, PCH2CH3), 1.55 (s, 18H, tBu), 2.18 (br
(31) Wengrovius, J. H.; Schrock, R. R. J. Organomet. Chem. 1981, 205,
319.
(32) Zucchini, U.; Albizzati, E.; Giannini, U. J. Organomet. Chem. 1971,
26, 357.
1
m, 6H, PCH2CH3), 2.33 (s, 6H, Me), 6.48 (br d, JPH ) 488 Hz,
1H, HP), 7.09 (s, 2H, Ar), 7.22 (s, 2H, Ar), 7.73 (d, J ) 7.9 Hz,

792 Organometallics, Vol. 25, No. 3, 2006
Chan et al.
2H, py-H3,5), 7.97 (t, J ) 7.9 Hz, 1H, py-H4). 13C NMR (126 MHz,
V ) 3815.1(13) Å3, Z ) 4, Dc ) 1.339 g cm-3, µ(Mo KR) ) 0.467
mm-1, F(000) ) 1594, T ) 253(2) K, 2θmax ) 50.7°, h -11 to 11;
k -22 to 22; l -22 to 23, 10554 indep reflns (Rint ) 0.0515), 863
variable parameters, R1 ) 0.057 (I > 2σ(I)), wR2 ) 0.142,
GOF(F2) ) 0.960, largest diff peak/hole ) 0.79/-0.48 e Å-3. For
7: C33H47NO2Cl3PZr, fw ) 718.29, monoclinic, P21/n, a )
12.324(3) Å, b ) 17.074(3) Å, c ) 17.421(4) Å, â ) 96.72(3)°, V
) 3640.5(13) Å3, Z ) 4, Dc ) 1.310 g cm-3, µ(Mo KR) ) 0.594
mm-1, F(000) ) 1496, T ) 253(2) K, 2θmax ) 50.7°, h -14 to 14;
k -20 to 19; l -18 to 20, 6117 indep reflns (Rint ) 0.0375), 381
variable parameters, R1 ) 0.041 (I > 2σ(I)), wR2 ) 0.104, GOF(F2)
1
CD2Cl2): 6.4 (br s, PCH2CH3), 9.9 (d, JPC ) 48 Hz, PCH2CH3),
20.6 (Me), 29.7 (CMe3), 34.7 (CMe3); methine carbons: 123.7,
129.1, 129.4, 139.4; 4° carbons: 127.6, 136.6, 154.6, 159.2. 31P
NMR (CD2Cl2): -18.78. EI-MS (+ve, m/z): 563 (100%) [M+
-
(PEt3H)Cl]. Anal. Calcd for C33H47NO2Cl3PZr (718.29): C, 55.18;
H, 6.59; N, 1.95. Found: C, 55.36; H, 6.46; N, 1.60.
[Zr(L1)Cl3][HPMe2Ph] (8). Dimethylphenylphosphine (3 mL,
1
21.1 mmol) was used. Yield: 0.22 g, 56% yield. H NMR (400
t
MHz, CDCl3): 1.54 (s, 18H, Bu), 2.03 (br, 6H, PCH3), 2.33 (s,
6H, Me), 7.09 (s, 2H, Ar), 7.22 (s, 2H, Ar), 7.58 (br, 2H, PhP),
7.68 (br, 3H, PhP), 7.74 (d, J ) 7.9 Hz, 2H, py-H3,5), 7.98 (t, J )
7.9 Hz, 1H, py-H4). 13C NMR (126 MHz, CDCl3): 20.6 (Me), 29.1
(PCH3; 1JPC coupling obscured by CMe3 peak), 29.7 (CMe3), 34.7
(CMe3); methine carbons: 120.1 (br), 123.7, 126.2 (br), 129.2,
129.5, 131.4 (br), 139.5; 4° carbons: 127.6, 127.7, 136.6, 154.6,
) 0.998, largest diff peak/hole ) 0.85/-0.65 e Å-3
.
Polymerization Procedures. Schlenk-line ethylene polymeri-
zation runs were carried out under atmospheric pressure in toluene
in a 100 mL glass reactor containing a magnetic stir bar. The stirred
solution containing the catalyst was thermostated to the required
temperature and purged with ethylene for 15 min. Polymerization
was initiated by adding a toluene solution of methylaluminoxane
(MAO), and the reactor was maintained under 1 atm of ethylene
for the duration of the polymerization. After the prescribed time,
HCl-acidified methanol (40 mL) was added to terminate the
polymerization, and the ethylene gas feed was stopped. The resultant
solid polymer was collected by filtration, washed with acidified
methanol, and dried under vacuum at 80 °C for 12 h.
Large-scale ethylene polymerization tests were carried out under
atmospheric pressure in toluene in a 500 mL glass reactor equipped
with a propeller-like stirrer. Toluene (250 mL) was introduced into
the nitrogen-purged reactor and stirred (600 rpm). The toluene was
thermostated to 25 °C, and the ethylene gas feed (100 L/h) was
then started. After 15 min, polymerization was initiated by adding
toluene solutions of the cocatalyst, then catalyst, into the reactor
with vigorous stirring (600 rpm). After the prescribed time, isobutyl
alcohol (10 mL) was added to terminate the polymerization, and
the ethylene gas feed was stopped. To the resulting mixture were
added methanol (1000 mL) and concentrated HCl (2 mL). The
polymer was collected by filtration, washed with methanol (200
mL), and dried in vacuo at 80 °C for 10 h. Ethylene-propylene
copolymerization was performed using a procedure similar to that
for ethylene polymerization, except ethylene (100 L/h) and pro-
pylene (100 L/h) were used. After the polymerization was termi-
nated, concentrated HCl (2 mL) was added to the resulting mixture,
and the mixture was washed with water (250 mL × 3) and
concentrated in vacuo. The resultant polymer was dried in vacuo
at 130 °C for 10 h. Ethylene-NB copolymerization was performed
using a similar procedure, except NB (1 g) was added to the toluene
before the ethylene gas feed (50 L/h) was started.
1
159.3. 31P[1H] NMR (CD2Cl2): -1.73 (d, JPH ) 526 Hz). EI-MS
(+ve, m/z): 563 (100%) [M+ - (PMe2PhH)Cl]. Anal. Calcd for
C35H43NO2Cl3PZr (738.28): C, 56.94; H, 5.87; N, 1.90. Found:
C, 56.72; H, 5.80; N, 1.95.
[Zr(L1)(CH2Ph)2] (9). A solution of H2L1 (0.230 g, 0.57 mmol)
in diethyl ether (15 mL) was slowly added to Zr(CH2Ph)4 (0.260
g, 0.57 mmol) in diethyl ether (15 mL) at -78 °C. The resultant
mixture was stirred for 30 min at -78 °C and for 10 h at room
temperature to give a bright yellow cloudy solution. Concentration
and storage of the solution at -78 °C for 12 h gave a bright yellow
crystalline solid. Yield: 0.24 g, 62%. 1H NMR (400 MHz, C6D6):
t
1.74 (s, 18H, Bu), 2.27 (s, 6H, Me), 2.67 (s, 4H, CH2), 6.56 (t, J
) 7.3 Hz, 2H, p-Ph), 6.76 (m, 6H, m-Ph and Ar-H6), 6.80 (t, J )
7.6 Hz, 1H, py-H4), 6.92 (d, J ) 7.8 Hz, 2H, py-H3,5), 7.00 (d, J
) 7.3 Hz, 4H, o-Ph), 7.35 (s, 2H, Ar-H4). 13C NMR (126 MHz,
C6D6): 21.17 (Me), 30.74 (CMe3), 35.37 (CMe3), 59.53 (CH2, 1JCH
) 134.5 Hz), 123.43 (p-Ph), 124.68 (py-C3,5), 129.51 (o-Ph), 129.80
(m-Ph), 130.10 (Ar-C4), 130.59 (Ar-C6), 138.49 (py-C4); 4°
carbons: 127.77, 128.56, 136.52, 138.16, 154.78, 159.62. Anal.
Calcd for C41H45NO2Zr (675.04): C, 72.95; H, 6.72; N, 2.07.
Found: C, 73.03; H, 6.42; N, 2.14.
X-ray Crystallography. Crystals mounted in a glass capillary
were used for data collection at -20 °C on a MAR diffractometer
with a 300 mm image plate detector using graphite-monochroma-
tized Mo KR radiation (λ ) 0.71073 Å). Data collection was made
with 2° oscillation steps of æ, 420 s exposure time, and scanner
distance at 120 mm, and 100 images were collected. The images
were interpreted and intensities integrated using the program
DENZO, and the structure was solved by direct methods employing
the SIR-97 program on a PC.33 For 3: C35H39Cl2NO3Zr‚C6D6, fw
) 767.98, monoclinic, P21/n, a ) 15.432(3) Å, b ) 16.281(3) Å,
c ) 17.126(3) Å, â ) 115.36(3)°, V ) 3888.2(12) Å3, Z ) 4, Dc
) 1.312 g cm-3, µ(Mo KR) ) 0.457 mm-1, F(000) ) 1584, T )
253(2) K, 2θmax ) 50.7°, h -18 to 18; k -19 to 19; l -18 to 18,
6301 indep reflns (Rint ) 0.0468), 433 variable parameters, R1 )
0.036 (I > 2σ(I)), wR2 ) 0.092, GOF(F2) ) 0.986, largest diff
Acknowledgment. We are grateful to the Research Grants
Council of the Hong Kong SAR, China [HKU 7095/00P], City
University of Hong Kong, and The University of Hong Kong
for financial support, and Dr. Duncan F. Wass and Steven C.
F. Kui for technical assistance.
peak/hole ) 0.38/-0.46 e Å-3. For 4: C40H41NO3Cl2Zr‚(C7H8)0.25
,
fw ) 768.93, triclinic, P1h (#2), a ) 10.743(2) Å, b ) 18.631(4)
Å, c ) 19.868(4) Å, R ) 81.32(3)°, â ) 81.24(3)°, γ ) 78.01(3)°,
Supporting Information Available: CIF files for 3, 4, 7, and
1
Zr(L1)2; perspective view of Zr(L1)2; H and 13C NMR spectra of
selected polyethylene samples. This material is available free of
charge via the Internet at http://pubs.acs.org.
(33) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, G.; Giacovazzo,
C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, R. J. Appl.
Crystallogr. 1998, 32, 115.
OM050864Z