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Professor Schrock is interested broadly in synthetic and mechanistic organotransition
metal and inorganic chemistry, catalysis, and polymers.
The research area of longest standing concerns complexes that contain
metal-carbon multiple bonds, usually alkylidene complexes (M=CHR) where
the metal is usually W or Mo in its highest possible oxidation state.
The primary goal is to synthesize and characterize complexes that are
catalysts for the metathesis of olefins and that have predictable and
controllable activities. The most important present application is the
catalytic synthesis of small enantiomerically pure organic molecules from
racemic precursors, e.g., "desymmetrization" of a triene with
an enantiomerically pure catalyst to give a cyclic product as one enantiomer.
Asymmetric metathesis studies rely on the development of new catalysts
that contain enantiomerically pure ligands such as 3,3'-disubstituted
biphenolates and binaptholates, and facile new routes to them. He also
is interested in the synthesis and development of new acetylene metathesis
catalysts, and in designing new ligands and exploring new catalytic reactions
involving organometallic species.
A second area of research concerns the reduction of dinitrogen in a well-defined
manner, the ultimate goal being activation and reduction of dinitrogen
using protons and electrons. Molybdenum complexes that contain a triamidoamine
ligand with 3,5-[2,4,6-i-Pr3C6H2]2C6H3 (hexaisopropylterphenyl) groups
on the amido nitrogens are of special interest since many derivatives
that one might expect to be involved in a catalytic reduction of dinitrogen
at a single metal center can be prepared and characterized. Moreover,
it has now been shown for the first time that dinitrogen can reduced to
ammonia catalytically under carefully controlled conditions with an efficiency
in reducing equivalents of ~65%. This is the first time that dinitrogen
has been reduced catalytically in a knowledgeable manner at room temperature
and pressure. These results suggest that the single molybdenum center
in FeMo nitrogenase may be the site of the reduction of dinitrogen to
ammonia. A wide variety of related triamido/amine ligands for Mo have
been prepared and new diamido/bisdonor ligands are being evaluated for
vanadium dinitrogen chemistry.
A third area of research concerns the controlled synthesis of specialty
polymers with alkylidene catalysts by either ring-opening metathesis polymerization
(ROMP) of cyclic olefins (e.g., norbornenes or cyclobutenes) or by cyclopolymerization
of 1,6-heptadiynes to yield polyenes. ROMP polymerizations are employed
for the synthesis of elastomeric triblock copolymers, in particular polymerizations
that involve bimetallic initiators. Cyclopolymerization of diethyldipropargylmalonate
and related species yields polymers that contain five- or six-membered
rings incorporated into polyene chains. These polyenes are relatively
air stable and dark red to purple. The object is to design catalysts that
will yield polymers that contain only five- or six-membered rings in a
living fashion and with total control over chain length. It ultimately
then will be possible to correlate polymer structure and chain length
with physical and other properties characteristic of highly conjugated
polyenes.
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