Latent Olefin Metathesis Catalysts Featuring Chelating Alkylidenes

The synthesis of a series of ruthenium-based metathesis catalysts featuring imine donors chelated through the alkylidene group is described. The relative placement of the imine carbon−nitrogen double bond (exocyclic vs endocyclic) has a major impact on the initiation behavior. When used in metathesis applications, catalysts with an endocyclic imine bond show latent behavior and a high degree of tunability. The incorporation of additional donor atoms is an additional strategy for controlling initiation behavior. These latent catalysts could be useful in high-temperature applications.