Cationic rare earth metal alkyls as novel catalysts for olefin polymerization and copolymerization

Cationic rare earth metal alkyl species, generated by the treatment of mono(cyclopentadienyl) bis(alkyl) rare earth metal complexes with 1 equiv. of a borate compound such as [Ph3C][B(C6F5)4], act as an excellent catalyst for the polymerization and copolymerization of various olefins such as ethylene, 1-hexene, styrene, norbornene, dicyclopentadiene, and isoprene. These catalysts show unprecedented activity and regio- and stereo-selectivity and afford a series of new polymers which are difficult to be prepared previously.