Computational Investigations of Ruthenium-Catalyzed Olefin Metathesis and Rhodium-Catalyzed Olefin Hydroboration Reactions

Transition metal catalysis has proven to be a powerful strategy for olefin functionalization and polymerization reactions. Ancillary ligands play an important role in controlling the reactivity and selectivity of these catalytic reactions. Mechanistically guided rational design of ancillary ligands to achieve desired reaction outcomes has been a long-standing challenge in transition metal catalyzed olefin hydrofunctionalization and metathesis reactions because multiple properties of the ligand, including electron donating ability, steric hindrance, and ligand flexibility, could contribute simultaneously to affect the reaction mechanism, reactivity, and selectivity. To date, development of new catalytic systems has been largely dependent on trial-and-error, as well as chemical intuition. Computational investigation is emerging as an effective tool to provide molecular level understanding of reaction mechanisms, substrate effects, and ligand effects. These theoretical insights can rationalize experimental observations and facilitate ligand design. In this thesis, I present a series of computational studies to probe ligand effects in transition metal catalyzed olefin metathesis and hydroboration reactions. The specific catalytic systems investigated include effects of phosphine ligands on the initiation rate of 2nd generation Grubbs catalyst, effects of switchable N-heterocyclic carbene (NHC) ligands on reactivity of Ru-catalyzed ring-opening metathesis polymerization reactions, and effects of NHC, phosphine, and asymmetric phosphite ligands on reactivity, regio-, and stereoselectivity of Rh-catalyzed olefin hydroboration reactions.