<i>Z</i>‑Selective Ethenolysis with
a Ruthenium Metathesis Catalyst: Experiment and Theory
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Abstract
The <i>Z</i>-selective ethenolysis activity of chelated
ruthenium metathesis catalysts was investigated with experiment and
theory. A five-membered chelated catalyst that was successfully employed
in <i>Z</i>-selective cross metathesis reactions has now
been found to be highly active for <i>Z</i>-selective ethenolysis
at low ethylene pressures, while tolerating a wide variety of functional
groups. This phenomenon also affects its activity in cross metathesis
reactions and prohibits crossover reactions of internal olefins via
trisubstituted ruthenacyclobutane intermediates. In contrast, a related
catalyst containing a six-membered chelated architecture is not active
for ethenolysis and seems to react through different pathways more
reminiscent of previous generations of ruthenium catalysts. Computational
investigations of the effects of substitution on relevant transition
states and ruthenacyclobutane intermediates revealed that the differences
of activities are attributed to the steric repulsions of the anionic
ligand with the chelating groups