Deep Red to Near-Infrared Light-Controlled Ruthenium-Catalyzed Olefin Metathesis

A system has been developed to activate a latent ruthenium olefin metathesis catalyst using deep red to near-infrared light (600-800 nm) in conjunction with an osmium(II) photocatalyst that is directly excited to its triplet state via spin-forbidden excitation. An excited-state single-electron reduction of a latent solvent-coordinated, cationic precatalyst is proposed as the operating mechanism for activation and photocontrol, as probed via in situ LED NMR kinetic studies and cyclic voltammetry. Excellent levels of spatiotemporal control are found under light irradiation. NIR olefin metathesis exhibits improved light penetration through barriers over shorter wavelengths of light, a control element that was deployed to mold dicyclopentadiene via ring-opening metathesis polymerization.