Reactivity and Selectivity in Ruthenium Sulfur‐Chelated Diiodo Catalysts

A trifluoromethyl sulfur‐chelated ruthenium benzylidene, Ru‐S‐CF3‐I, was synthesized and characterized. This latent precatalyst provides a distinct activity and selectivity profiles for olefin metathesis reactions depending on the substrate. For example, 1,3‐divinyl‐hexahydropentalene derivatives were efficiently obtained by ring‐opening metathesis (ROM) of dicyclopentadiene (DCPD). Ru‐S‐CF3‐I also presented a much more effective photoisomerization process from the inactive cis‐diiodo to the active trans‐diiodo configuration after exposure to 510 nm (green light), allowing for a wide scope of photoinduced olefin metathesis reactions. DFT calculations suggest a faster formation and enhanced stability of the active trans‐diiodo species of Ru‐S‐CF3‐I compared with Ru‐S‐Ph‐I, explaining its higher reactivity. In addition, the photochemical release of chloride anions by irradiation of Cl‐BODIPY in the presence of DCPD derivatives with diiodo Ru benzylidenes, led to in situ generation of chloride complexes, which quickly produced the corresponding cross‐linked polymers. Thus, novel selective pathways that use visible light to guide olefin metathesis based synthetic sequences is presented. A diiodo trifluoromethyl sulfur‐chelated ruthenium benzylidene complex was synthesized as precatalyst for olefin metathesis, allowing ring‐opening metathesis of dicyclopentadiene in the presence of a methylene donor to produce 1,3‐divinyl‐hexahydropentalenes and depolymerization of polybutadiene upon green light irradiation. The selectivity displayed by the catalyst is attained through a fine balance between its rate of pre‐activation and deactivation.