New Polymerization Reactions by Dynamic Rare Earth Complexes

1. 稀土金属双（烷基）配合物的合成及转化为阳离子单（烷基）活性物质：近年来，稀土金属双（烷基）配合物受到了广泛的关注，因为由它们制备的这种配合物或阳离子单（烷基）物质有望提供一个空间和电子上更不饱和的金属中心，从而表现出与传统的茂金属不同的独特反应活性。本研究以Ln(CH_2SiMe_3)_3 （2thf）和C_5Me_4HSiMe_3为原料，成功制备了一系列半夹层稀土金属双（烷基）配合物。用类似的方法也得到了两个金属中心由两个磷酸配体桥接的双核稀土金属二（烷基）配合物和非茂金属钇二（烷基）配合物。这些双（烷基）配合物用1等量的[Ph_3C][B(C_6F_5)_4]处理后，可以很容易地转化为相应的阳离子单（烷基）物质。阳离子稀土金属单（烷基）种催化高选择性共聚反应的研究进展：这些阳离子稀土金属可以作为各种烯烃的区域和立体定向聚合和共聚的优良催化剂。它们对苯乙烯与乙烯的异规共聚、乙烯与降冰片烯或二环戊二烯的交替共聚、异戊二烯的等规3,4聚合和顺式1,4聚合均表现出优异的活性和选择性。这些聚合反应大多是稀土金属催化剂所特有的，是以前已知的催化剂体系难以实现的。稀土金属氢化物簇的合成及配合物的协同反应性研究：在研究过程中，我们发现半夹层的稀土金属双（烷基）配合物很容易与H_2反应生成相应的四核八羟基配合物。这些氢化物团簇对各种多键表现出很高的反应活性。例如，与一氧化碳的反应在温和条件下选择性地产生乙烯。少

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