Synthesis and Reactivity of an Olefin Metathesis-Catalyzing Ruthenium Complex with a Selenoether Moiety in the Benzylidene Ligand.

A Hoveyda-Grubbs (HG)-type olefin metathesis complex with a selenoether moiety at the terminus of phenoxy moiety was synthesized. The complex showed direct selenium-atom coordination to the ruthenium center, resulting in higher thermodynamic stability compared with the parent HG catalyst. The selenium atom binding enhanced the tolerance to protic solvent molecules in ring-closing metathesis of N-tosyldiallylamide and diethyl diallylmalonate, and also in the cross metathesis between 3-butenylbenzoate and methyl acrylate. The large activation enthalpy observed in the reaction with n-butyl vinyl ether indicated an increased contribution of the "dissociative mechanism" during the initiation of the catalytic cycle. Introducing coordinative atoms or functional groups at the terminal of the phenoxy moiety is a useful strategy to regulate the thermostability of HG-type olefin metathesis catalysts.