ISSN 1070-4272, Russian Journal of Applied Chemistry, 2007, Vol. 80, No. 9, pp. 1515!1522. + Pleiades Publishing, Ltd., 2007.
Original Russian Text + M.Yu. Malinskaya, N.I. Ivancheva, I.I. Oleinik, G.A. Tolstikov, S.S. Ivanchev, 2007, published in Zhurnal Prikladnoi Khimii,
2007, Vol. 80, No. 9, pp. 1479!1488.
Catalytic Activity of Systems Based on Titanium
Bis(phenoxy Imine) Complexes: Effect of the Ligand Structure
M. Yu. Malinskaya, N. I. Ivancheva, I. I. Oleinik, G. A. Tolstikov, and S. S. Ivanchev
St. Petersburg Branch, Boreskov Institute of Catalysis, Siberian Division, Russian Academy of Sciences,
St. Petersburg, Russia
Vorozhtsov Novosibirsk Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences,
Received July 22, 2007
Abstract-Polymerization of ethylene at 30370oC in the presence of catalytic systems based on titanium
bis(phenoxy imine) complexes of various structures, activated with methylalumoxane, was studied. An attempt
was made to systematize the effect of substituents in ligands, to find correlations, to account for the results
obtained, and to reveal conditions under which the reaction occurs by the [living] polymerization mechanism.
Some properties and structural features of the polyethylenes obtained were determined.
The recently discovered new class of postmetallo-
cene catalysts of ethylene and a-olefin polymeriza-
tion, based on transition metal phenoxy imine com-
plexes, attracts attention of many research teams.
Particularly active studies are performed by the team
headed by T. Fujita (Mitsui Chem. Inc.), who pub-
lished numerous papers on the synthesis of phenoxy
imine complexes of zirconium, titanium, and other
transition metals and examined their catalytic activity
in polymerization of ethylene and a-olefins .
Somewhat later reviews written by other authors were
published [4, 5].
The published studies revealed high capability of
phenoxy imine catalytic systems for incorporation into
the polymeric chain of a-olefins of various structures,
including sterically hindered and even polar mono-
mers. These studies demonstrated the possibility of
controlling the formation of the macrochain forming
in the course of polymerization and of expanding the
assortment of the synthesized polymers by involving
new monomers into the copolymerization. It was
found that one of the factors responsible for the high
catalytic activity of systems based on transition metal
phenoxy imine complexes is the polydentate coordina-
tion mode, with intense electron exchange between
the transition metal ion and unsymmetrical ligands.
Therefore, the structure and electronic properties of
the ligands exert a strong effect on the activity and
selectivity of catalytic systems based on phenoxy
imine complexes. Variation of the structure of phen-
oxy imine ligands is widely used in searching for
new catalysts showing high activity and stability
under the polymerization conditions.
Even in their first papers , Fujita et al. con-
sidered the dependence of the catalytic activity of
phenoxy imine complexes (with methylalumoxane,
MAO, as cocatalyst) on the kind of transition metal,
with the complexes of Zr, Ti, Hf, and V as examples.
They were also the first to analyze the influence ex-
erted on the catalytic activity by the size of substitu-
ents in the imine and phenoxy moieties. The main
conclusions made in these papers are as follows.
(1) The phenoxy imine catalytic systems contain-
ing an aldimine group show higher activity than their
analogs with a ketimine group.
(2) Small substituents at the imine N atom do not
prevent approach of the monomer to the active center
of the propagating chain.
(3) A bulky substituent near the phenoxyl oxygen
atom sterically protects it from the electrophilic attack
of Lewis acids present in the polymerization medium
and favors efficient separation of the cationic active
species and anionic fragments of the cocatalyst.
(4) Fluorinated substituents at the imine nitrogen
atom ensure the occurrence of the polymerization by
the [living] mechanism.
These conclusions were based on the results of
experimental studies of a relatively limited number of