APPLICATIONS OF CHLORO-ARYLOXIDE COMPLEXES OF TUNGSTEN IN OLEFIN METATHESIS - THE RING-OPENING METATHESIS POLYMERIZATION OF DICYCLOPENTADIENE

The chloro-aryloxide complexes of tungsten WCl6-x(OAr)x (x = 2, 3, 4; OAr = substituted phenoxide), when associated with alkyl-aluminium, alkyl-tin or alkyl-lead compounds, are effective catalysts in the ring-opening metathesis polymerization of dicyclopentadiene. The polymer structure depends on the nature of the cocatalyst. With alkyl-aluminium compounds, the reaction results in the formation of a highly crosslinked polymer. Depending on the nature of the aryloxide ligand, reaction times vary from a few seconds to a few minutes. Aryloxide ligands with 4-methoxy or 2,6-di-isopropyl substituents lead to induction periods compatible with RIM (Reaction Injection Molding) techniques; tentative interpretations of these induction periods are given. With alkyl-tin or alkyl-lead cocatalysts, the chloro-aryloxide complexes lead to soluble poly-dicyclopentadienes; analysis of these polymers show that only the norbornene ring is cleaved and that there is no C = C double bond loss during polymerization.