An Initiation Kinetics Prediction Model Enables Rational Design of Ruthenium Olefin Metathesis Catalysts Bearing...

Area of Science:

• Organometallic Chemistry
• Catalysis
• Computational Chemistry

Background:

• Olefin metathesis is a crucial reaction in organic synthesis.
• Second-generation ruthenium catalysts offer improved performance but require precise initiation rate control.
• Predicting catalyst initiation is challenging due to complex mechanisms.

Purpose of the Study:

• To develop and validate a computational model for predicting initiation rates of second-generation ruthenium olefin metathesis catalysts.
• To enable rational design of catalysts with tailored initiation kinetics.
• To synthesize and characterize novel ruthenium catalysts with modified chelating benzylidene ligands.

Main Methods:

• Computational modeling based on a single thermodynamic parameter.
• Synthesis of thirteen ruthenium catalysts with varied alkoxy groups on the chelating benzylidene.
• Kinetic studies using UV/Vis spectroscopy and NMR spectroscopy.
• Structural characterization via X-ray crystallography.

Main Results:

• The computational model accurately predicted the initiation kinetics of the synthesized ruthenium catalysts.
• Catalysts with varied steric bulk on the alkoxy groups showed predictable changes in initiation rates.
• A dicyclohexylmethoxy-substituted catalyst exhibited one of the fastest initiation rates for Hoveyda-Grubbs-type complexes, as predicted by the model.
• The model's compatibility was confirmed for catalysts with alternative N-heterocyclic carbene (NHC) ligands and disubstituted alkoxy benzylidenes.

Conclusions:

• A computational approach based on a single thermodynamic parameter effectively predicts initiation rates for second-generation ruthenium olefin metathesis catalysts.
• This model facilitates the rational design of catalysts with desired initiation properties.
• The findings pave the way for developing highly efficient ruthenium catalysts for various applications.