Stabilization of (trialkylphosphine)ruthenium alkylidene metathesis catalysts using phosphine exchange

The second-generation Grubbs analogues (H2IMes)RuCl2(CHPh)(PR3) (R = Me, Bu) were essentially metathesis-inactive and air-stable at room temperature but exhibited first-order metathesis with ethyl vinyl ether at elevated temperature. The PMe3 complex underwent second-order ligand exchange with PBu3, indicating different coordination mechanisms (dissociative vs associative) in the two reactions.