Theoretical Attempts: "In Silico Olefin Metathesis"-How Can Computers Help in the Understanding of Metathesis Mechanisms and in Catalysts Development?

This chapter presents the main achievements obtained computationally in the field of Ru-catalyzed olefins metathesis, starting with the events associated with activation of the (pre)catalyst. It describes events inside the catalytic cycle and description of the mechanisms leading to catalyst deactivation. It also focuses on catalysts bearing an N-heterocyclic carbene (NHC) ligand. The accepted mechanism for both Mo and Ru catalysts can be divided into three separate events: initiation, propagation, and termination. A small energy barrier prevents the coordinated olefin from reacting with the Ru-alkylidene bond, thus precipitating into the metallacycle, which is the most stable structure along the reaction pathway. NHC-based Ru-catalysts are highly dynamic structures with practical consequences in catalysis.