New Polymerization Reactions by Dynamic Rare Earth Complexes

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1. Synthesis of Rare Earth Metal Bis(alkyl) Complexes and Conversion into Cationic Mono(alkyl) Active Species : Recently, considerable attention has been directed to rare earth metal bis(alkyl) complexes, since such complexes or cationic mono(alkyl) species prepared from them are expected to provide a sterically and electronically more unsaturated metal center and thus to show unique reactivity that differs from those of the conventional metallocenens. In this study, a series of half-sandwich rare earth metal bis(alkyl) complexes have been successfully prepared from Ln(CH_2SiMe_3)_3 (2thf) and C_5Me_4HSiMe_3. Binuclear rare earth metal bis(alkyl) complexes, in which the two metal centers are bridged by two phosphido ligands, and non-metallocene yttrium bis(alkyl) complexes have also been obtained in an analogous way. These bis(alkyl) complexes can be readily converted to the corresponding cationic mono(alkyl) species by treating with 1 equiv of [Ph_3C][B(C_6F_5)_4].2. Development of Hi … More ghly Selective Copolymerization Reactions Catalyzed by Cationic Rare Erath Metal Mono(alkyl) Species : These cationic rare earth metal species can act as excellent catalysts for the region-and stereospecific polymerization and copolymerization of various olefins. They exhibit excellent activities and selectivity for syndiospecific copolymerization of styrene with ethylene, alternating copolymerization of ethylene with norbornene or dicyclopentadiene, and isospecific 3,4-polymerization and living cis-1,4-polymerization of isoprene. Most of these polymerization reactions are unique to the rare earth metal catalysts, and are difficult to achieve by previously known catalyst systems.3. Synthesis of Rare Earth Metal Hydride Clusters and Studies on Synergistic Reactivity of These Complexes : In the course of these studies, we found that the half-sandwich rare earth metal bis(alkyl) complexes can readily react with H_2 to afford the corresponding tetranuclear octahydrido complexes. These hydride clusters exhibit high reactivities towards various multiple bonds. For example, the reaction with carbon monoxide afforded selectively ethylene under mild conditions. Less