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Queen Elizabeth II Fellows
Dr Eric Wenger
The main topic of our research is
concerned with the stabilisation of reactive organic moieties by
coordination to transition metals and the insertions of unsaturated
molecules into metal-carbon bonds. These reactions are essential to
organic synthesis for the formation of new carbon-carbon bonds and
are often present in catalytic systems. Our investigations are
mainly based on experimental organometallic reactions with the help
of multinuclear spectroscopic techniques, but in recent years
invaluable mechanistic information has also been obtained by DFT
computations.
Organometallic Chemistry of Alkynes
The
study of the insertion reactions of alkynes into the aryl-metal bonds
of pallacycles has been continued both experimentally and
theoretically, but the nature of the highly reactive complexes
involved in the insertion reactions is usually not well defined.
However, data obtained with various complexes containing the
benzylamine moiety
Pd(C6H4CH2NMe2-kC,N)
have shown that the regiochemistry of the insertions of
ester-activated alkynes may be influenced by the electron-density on
the metal, e.g. whether the complex is neutral or cationic. These
reactions seem to take place via a four-coordinate mechanism,
hence exchange of the ligand cis to the reactive
phenyl-palladium bond by the alkyne is the rate-limiting step.
Highly charged complexes show altered regioselectivities which may
result from electrostatic interactions with the incoming alkyne.
These recent results have important impacts for modern catalytic
reactions carried out in water or ionic liquids. (with A.J.
Edwards, A.C. Willis, and S A. Macgregor [Heriot-Watt U., Edinburgh,
UK])
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