Hoveyda-Type Olefin Metathesis Complexes

This chapter summarizes the work in ruthenium-based olefin metathesis catalyst design, using the chelating benzylidene ligands-that is, Hoveyda-Grubbs type catalysts bearing oxygen and other chelating heteroatoms. It discussess the properties of olefin metathesis catalysts, one cannot disregard the mechanistic studies that were carried out for the chelated benzylidene complexes. The chapter describes the complexes based on the ubiquitous isopropoxy-benzylidene chelating ligand (derived from 2-isopropoxystyrene) with different N-heterocyclic carbene (NHC) groups and their activity in olefin metathesis catalysis. Changes on the classical mesitylene substituted Arduengo NHC may be classified into three main types such as changing the main imidazoline ring, substitutions on the ring backbone, and functionalization of the aromatic moieties bound to the nitrogen atoms. The discovery that anionic ligands freely interchange during the reaction has some serious implications when planning new olefin metathesis catalysts.