Interference 103,482
Ewen et al., U.S. 4,892,851, describes metallocene
catalysts which are said to be useful for preparing
syndiotactic polyolefins, particularly polypropylenes, and
processes for the preparation of syndiotactic polyolefins
using the metallocene catalysts. The reference does not
specifically describe a metallocene catalyst which is defined
or encompassed by Claims 4-6, 8, and 12-37 of Dolle
Application 08/147,006. Moreover, Ewen et al, U.S. 4,892,851
would have led persons having ordinary skill in the art to
believe that all the metallocene compounds therein generically
described are syndiospecific, i.e., are useful exclusively for
preparing polyolefins having syndiotactic stereochemical
structures.
See the teaching of Ewen et al., U.S. 4,892,851 (EE I), at
column 13, line 59, to column 14, line 5 (emphasis added):
It should be further understood that the
syndiospecific catalysts of the present invention are
not limited to the specific structures recited in the
Examples, but rather, include catalysts described by
the general formula given herein in which one Cp ring
is substituted in a substantially different manner so
as to be sterically different. In the Examples above,
the rings included an unsubstituted Cp ring and a Cp
ring substituted to form a fluorenyl radical, but
similar results are obtainable through the use of other
ligands consisting of bridged Cp rings in which one of
the Cp rings is substituted in a substantially different
manner from the other Cp ring, e.g., an indenyl radical
and a Cp ring, a tetramethyl substituted Cp ring and a
103
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