A Hoveyda–Grubbs‐Type Olefin Metathesis Catalyst Bearing a Fluorinated Unsymmetrical NHC Ligand

A novel Hoveyda–Grubbs’ second‐generation‐type ruthenium complex featuring an unsymmetrical N‐heterocyclic carbene (uNHC) ligand with N‐cyclohexyl, N’‐ ortho ‐difluorophenyl substituents and syn phenyl groups on the backbone was synthesised and fully characterised. Its catalytic performance was evaluated in representative ring‐closing metathesis (RCM), cross‐metathesis (CM) and ring‐opening metathesis polymerisation (ROMP) reactions and compared with that of a non‐fluorinated analogue. The introduction of fluorine affects both the stability and catalytic performance of the resulting complex by modulating the steric and electronic properties of the NHC ligand. In RCM reactions, the fluorinated catalyst showed improved activity relative to the non‐fluorinated counterpart, whereas in CM reactions similar activity and selectivity were observed for both catalysts. In the ROMP copolymerisation of norbornene with cis‐ cyclooctene, the fluorinated complex exhibited lower chemoselectivity in the formation of alternating copolymers.