Organometallics 2011, 30, 669–675 669
DOI: 10.1021/om100112x
Synthesis of the Binuclear Half-Metallocene Chromium(III) Aryloxides
[Cp0Cr(OAr)Cl]2 and Their Catalytic Properties for Ethylene
Polymerization in the Presence of Alkylaluminum Cocatalyst
Mingtai Sun, Ying Mu,* Yang Liu, Qiaolin Wu, and Ling Ye
State Key Laboratory for Supramolecular Structure and Materials, School of Chemistry, Jilin University,
2699 Qianjin Street, Changchun 130012, People’s Republic of China
Received February 11, 2010
A number of new chloride-bridged binuclear half-metallocene chromium(III) aryloxide complexes
[Cp0Cr(OAr)Cl]2 (Cp0 = C5H5 (1, 2), C5Me5 (3, 4); Ar = 2,6-iPr2C6H3 (1, 3), 2,6-tBu2C6H3 (2, 4))
have been synthesized from the reaction of Cp0CrCl2(THF) with the lithium salt of the corresponding
aryloxide ligand in THF. All complexes have been characterized by elemental analyses, 1H NMR, IR,
and UV-vis spectroscopy. The molecular structures of complexes 1 and 3 were determined by X-ray
crystallography. Upon activation with a small amount of AlR3, all complexes 1-4 show high
catalytic activity for ethylene polymerization, producing high-molecular-weight polyethylene. The
effects of polymerization conditions such as polymerization temperature, alkyl aluminum cocatalyst,
and Al/Cr molar ratio on the catalytic activity and properties of the produced polyethylene were
investigated.
Introduction
dedicated to design well-defined chromium-based catalysts and
to explore their catalytic performance for homogeneous model
systems.1a It was reported that chromium(III) complexes5,6
bearing β-diketiminate ligands and salicylaldiminato ligands
are active catalysts for ethylene polymerization and exhibit
lower catalytic activity upon activation with MAO com-
pared to systems activated with alkylaluminum chloride or
trialkylaluminum (AlR3). Chromium(III) complexes bear-
ing triazacyclohexane,7a diphosphine ligands,7b and other
neutral donor ligands7c were also reported to show good cata-
lytic activity for ethylene polymerization, and some chro-
mium(III) complexes with diphosphine ligands7d are extremely
active and selective ethylene trimerization catalysts. In addi-
tion, cyclopentadienyl-amine,8a,b cyclopentadienyl-phosphine,8c
Chromium-based olefin polymerization catalysts have
attracted intensive attention in the past decades due to their
applications in polyolefin industry.1-3 Heterogeneous chromium-
based olefin polymerization catalysts of the Phillips and
Union Carbide systems (Cr/SiO2) have been widely used in
the commercial production of polyolefins.4 To understand
the nature of the active species of the Phillips and Union
Carbide catalysts, a considerable amount of effort has been
*To whom correspondence should be addressed. Tel: (86)-431-
85168376. Fax: (86)-431-85193421. E-mail: ymu@jlu.edu.cn.
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2011 American Chemical Society
Published on Web 02/01/2011
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