Specialized Ruthenium Olefin Metathesis Catalysts Bearing Bulky Unsymmetrical NHC Ligands: Computations, Synthesis, and Application

Second-generation
ruthenium olefin metathesis catalysts were investigated
with systematic variation of the unsymmetrical uNHC ligands. Depending
on the uNHC steric bulk, the catalysts exhibited different activity
and selectivity in metathesis reactions. DFT calculations and X-ray
crystallographic data were used to understand the influence of uNHC
ligand structure on the catalyst properties. Furthermore, the catalysts
were examined in the context of reactions that are problematic for
general-purpose Ru catalysts, including industrially important self-cross
metathesis of α-olefins and ethenolysis of ethyl oleate.