New Polymerization Reactions by Dynamic Rare Earth Complexes

1.稀土金属双(烷基)配合物的合成及其转化为阳离子单(烷基)活性物种：近年来，稀土金属双(烷基)配合物或由其制备的阳离子单(烷基)配合物有望提供空间和电子上更不饱和的金属中心，从而显示出不同于传统茂金属的独特反应活性，因此引起了人们的极大关注。本研究以Ln(CH_2SiMe_3)_3(2thf)和C_5Me_4HSiMe_3为原料，成功地合成了一系列半夹心稀土双(烷基)配合物，并以类似的方法合成了双核稀土双(烷基)配合物，其中两个金属中心由两个磷基配体桥联，非茂稀土双(烷基)配合物。用1当量的[Ph_3C][B(C_6F_5)_4]处理这些双(烷基)络合物可以很容易地转化为相应的阳离子单(烷基)物种。Hi…的开发由阳离子稀土金属单(烷基)物种催化的选择性更高的共聚反应：这些阳离子稀土金属物种可以作为各种烯烃的区域和立体定向聚合和共聚的优秀催化剂。它们对苯乙烯与乙烯的间规共聚、乙烯与降冰片烯或双环戊二烯的交替共聚、异戊二烯的等规3，4-聚合和活性顺-1，4-聚合均表现出良好的活性和选择性。这些聚合反应大多是稀土金属催化剂所特有的，用已知的催化体系很难实现。稀土金属氢化物簇合物的合成及其协同反应性研究：在这些研究过程中，我们发现半夹心稀土金属双(烷基)络合物很容易与H_2反应生成相应的四核八氢络合物。这些氢化物簇合物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的条件下选择性地产生了乙烯。较少

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