希土類の特徴を生かした新規精密エラストマー合成 [in Japanese] Synthesis of Novel Elastomers by Well-Defined Rare Earth Metal Catalysts [in Japanese]
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The cationic rare earth metal alkyl species bearing a bis (phosphine) amide ancillary ligand, generated by treatment of the corresponding dialkyl complexes with one equivalent of a borate compound can serve as an excellent catalyst for the living <i>cis</i>-1, 4 polymerization of both isoprene and butadiene as well as for the living <i>cis</i>-1, 4 copolymerization of isoprene and butadiene. On the other hand, the polymerization of isoprene by the binuclear monocationic monoalkyl species with cyclopentadienyl-phosphide ligands has afforded exclusively isotactic 3, 4-polyisoprene with extremely high regio- and stereoselectivity (3, 4-selectivity: 100%, <i>mmmm</i>>99%). An amidinate-ligated aminobenzylyttrium complex, in combination with [Ph<sub>3</sub>C] [B(C<sub>6</sub>F<sub>5</sub>)<sub>4</sub>], is an excellent catalyst system for the isospecific 3, 4-polymerization of isoprene, while the regio- and stereoselectivity of this polymerization system can be dramatically switched from 3, 4-isospecific to 1, 4-<i>cis</i> selective by the addition of AlMe<sub>3</sub>. Cationic rare-earth hydride clusters, which are made by treating the corresponding neutral complexes with a borate activator, show high regio- and stereoselectivity for the polymerization of 1, 3-cyclohexadiene (CHD) to afford soluble crystalline <i>cis</i>-1, 4-linked poly (CHD) unavailable previously. The syndiospecific living copolymerization of styrene with isoprene has been achieved by use of a cationic half-sandwich scandium alkyl catalyst.
GOMU 81(10), 414-418, 2008-10-15
THE SOCIRETY OF RUBBER SCIENCE AND TECHNOLOGYY, JAPAN