Evidence for Ruthenium(II) Peralkene Complexes as Catalytic Species during the Isomerization of Terminal Alkenes in Solution

The isomerization (chain-walking) reaction of terminalto internalalkenes is catalyzed by part-per-million amounts of practically anyRu source when the reaction is carried out with a neat terminal alkene.Here, we provide evidence that the soluble starting Ru sources evolveto catalytically active peralkene Ru(II) speciesunder reaction conditions. These species may also explain the isomerizationproducts found during other Ru-catalyzed alkene processes, i.e., alkenemetathesis reactions. A Finke-Watzky mechanism for catalystformation is consistent with the evidence obtained. The isomerization reaction of terminalto internal alkenesis plausibly catalyzed by part-per-million amounts of per-alkene Ru(II)complexes formed in situ from a variety of Ru sources. The reactionproceeds without any additive or solvent, and a Finke-Watzkymechanism for the catalyst formation is in operation here. The insitu transformation of Grubbs-type catalyst explains the commonlyobserved isomerization of alkenes during metathesis reactions.

Automated summary

This study provides evidence that soluble starting Ru sources evolve into catalytically active peralkene Ru(II) species under reaction conditions, which may also explain the isomerization products found during other Ru-catalyzed alkene processes. A Finke-Watzky mechanism for catalyst formation is consistent with the evidence obtained.