Rare‐Earth Metallocenes for Polymerization of Olefins and Conjugated Dienes: from Fundamental Studies to Olefin Block Copolymers

Abstract

The various steps in the mechanism of olefin polymerizations mediated by neutral rare earth metallocene complexes are discussed. The complexes are either trivalent hydride and alkyl rare earth compounds or divalent metallocenes that are activated by the monomer via an oxidation step. The stereospecific polymerizations of conjugated dienes based on the association of a cationic metallocene complex and an alkylaluminum and the polymerization mechanism based on monomer insertion into an aluminum‐carbon bond are also discussed. The exploitation of metallocene complexes for the copolymerization of olefins with conjugated dienes is the subject of a third part of this review. The synthesis of new elastomers called ethylene butadiene rubber (EBR) is highlighted. Finally, the use of rare‐earth metallocenes in macromolecular engineering is detailed. This includes the synthesis of functional polyolefins and block copolymers including thermoplastic elastomers.