Inorg. Chem. 2006, 45, 3476−3477
Highly Active Titanium-Based Olefin Polymerization Catalysts Supported
by Bidentate Phenoxyamide Ligands
Daniel C. H. Oakes, Vernon C. Gibson,* Andrew J. P. White, and David J. Williams
Imperial College, Exhibition Road, London SW7 2AZ, U.K.
Received January 25, 2006
Scheme 1
Phenoxyamide complexes of Ti-containing 2,6-X2C6H3 (X
) Cl,
Br) substituents, when activated by methyl aluminoxane, afford
catalysts with very high activities for the polymerization of ethylene
and with good incorporation of 1-hexene.
Bidentate phenoxyimine ligands have made a dramatic
impact on group 4 metal olefin polymerization catalysis.1-6
Such ligands are attractive because of their ease of synthesis
and elaboration by straightforward Schiff base condensation
procedures. An additionally attractive yet, to date, little
exploited feature of the reaction chemistry of phenoxyimines
is their ready reduction to phenoxyamines, which may serve
as convenient precursors to phenoxyamide ligands. The wide
range of ligand substitution patterns already elaborated for
their phenoxyimine precursors highlights the potential for
forming a similarly extensive library of dianionic ligands
based on the phenoxide and amide donor combination.
Recently, we described highly active ethylene polymeri-
zation catalysts supported by tridentate phenoxyamide ligands7
but, at the same time, found surprisingly low activities for a
simple bidentate derivative containing the bulky 2,6-Pri2C6H3
imino substituent. Here we show that incorporation of halo
substituents within the amido aryl units leads to catalysts
with dramatically improved ethylene polymerization activities
and excellent 1-hexene incorporation.
according to Scheme 1. Treatment of 1-4 with TiCl2(NMe2)2
gave the phenoxyamide complexes 5-8 with concomitant
formation of dimethylamine. The hydrocarbon derivative 5
retains one molecule of dimethylamine within the metal’s
coordination sphere, whereas complexes 6-8 retain two
molecules, reflecting the enhanced electrophilicity of the
metal center in the halo-substituted products. Crystals of 8
suitable for an X-ray structure determination (see the
Supporting Information for details) were grown from a
saturated pentane solution. The geometry at Ti is slightly
distorted octahedral (Figure 1) with cis angles in the range
of 83.18(14)-94.7(2)°; the trans angles are between 171.3(2)
and 176.42(16)°. The six-membered chelate ring adopts a
shallow boat conformation with O(1) and C(7) lying +0.12
and +0.28 Å, respectively, out of the plane of the other four
atoms, which are coplanar to better than 0.01 Å. The C6F5
ring is oriented orthogonally (ca. 89°) to this latter plane, a
conformation perhaps stabilized by a pair of weak N-H‚‚‚F
interactions. The amide character of the C(7)-N(7) linkage
is clearly evident from its bond length of 1.491(6) Å, and
the Ti-N distance to this formally anionic N [1.965(4) Å]
is very much shorter than those to the neutral dimethylamine
ligands [2.232(5) and 2.243(6) Å]. The geometry at N(7) is
distorted trigonal planar with the N lying ca. 0.07 Å out of
The aminophenol proligands 1-4 were readily synthesized
in good yields via the reduction of the corresponding
iminophenols and isolated as colorless crystalline solids
* To whom correspondence should be addressed. E-mail:
(1) Suzuki, Y.; Terao, H.; Fujita, T. Bull. Chem. Soc. Jpn. 2003, 76, 1493.
(2) Matsui, S.; Fujita, T. Catal. Today 2001, 66, 63.
(3) 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.
(4) Mitani, M.; Mohri, J.; Yoshida, Y.; Saito, J.; Ishii, S.; Tsuru, K.;
Matsui, S.; Furuyama, R.; Nakano, T.; Tanaka, H.; Kojoh, S.-i.;
Matsugi, T.; Kashiwa, N.; Fujita, T. J. Am. Chem. Soc. 2002, 124,
3327.
(5) Saito, J.; Onda, M.; Matsui, S.; Mitani, M.; Furuyama, R.; Tanaka,
H.; Fujita, T. Macromol. Rapid Commun. 2002, 23, 1118.
(6) For a general review, see: Gibson, V. C.; Spitzmesser, S. K. Chem.
ReV. 2003, 103, 283.
(7) Oakes, D. C. H.; Kimberley, B. S.; Gibson, V. C.; Jones, D. J.; White
A. J. P.; Williams, D. J. Chem. Commun. 2004, 2174.
3476 Inorganic Chemistry, Vol. 45, No. 9, 2006
10.1021/ic060146k CCC: $33.50
© 2006 American Chemical Society
Published on Web 04/05/2006