Initiation Kinetics of Latent Olefin Metathesis Precatalysts

Latent catalysts represent a specialized class of precatalysts that remain dormant under ambient conditions until activated by external stimuli to initiate catalytic activity. This study investigates the initiation behavior of latent olefin metathesis precatalysts, focusing on two different types: sulfur‐chelated systems and phosphite‐ligated ruthenium complexes. The initiation process was first monitored in situ by tracking characteristic proton nuclear magnetic resonance ( 1 H‐NMR) signals in the presence of butyl vinyl ether under two activation modes: heating and light irradiation. The analysis for both activation stimuli enabled the determination of initiation rate constants and revealed details of the distinct mechanistic pathways. Moreover, comparing the initiation kinetics and catalytic performance in ring‐closing metathesis (RCM) and ring‐opening metathesis polymerization (ROMP) established structure–activity relationships. The ligand environment was found to significantly modulate precatalyst reactivity, with sulfur‐chelated complexes mostly showing enhanced thermal activity, while phosphite systems demonstrated superior photochemical responsiveness. These findings provide support for advancing the development of next‐generation latent metathesis catalysts with tailored activation profiles for precision polymer synthesis and spatiotemporal control of polymerization processes.