New Early Transition Metal Metallocene Chemistry

这项由无机化学、生物无机化学和金属有机化学项目颁发的奖项支持了芝加哥大学的理查德·F·乔丹教授的研究，他的研究旨在开发高效的方法来合成手性金属芳烃-茂金属化合物，并扩大对作为烯烃聚合反应瞬时中间体模型的d0金属烯烃络合物性质的基本了解。钛、锆、氢等早过渡金属的茂金属络合物在有机合成中具有重要意义，而与之密切相关的阳离子络合物是催化烯烃聚合的活性物种。手性环戊二烯-茂金属催化剂是一种重要的立体选择性烯烃聚合催化剂，已被用作其他烯烃反应的对映选择性催化剂或试剂。采用扭曲构象的双酰胺络合物中含有6元螯合环的茂金属化合物，其配体可以控制环戊二烯配体的表面选择性，它们补充了2重对称的rac-茂金属化合物，强烈地不利于介茂金属结构。这项研究的第一部分将：1)发展基于络合控制的盐消除和胺消除反应的简化的ANSA-茂金属合成，2)建立这种方法对具有不同结构的第4族和第3族/稀土的ANSA-茂金属的共性，3)通过研究第4族金属双酰胺配合物的构象和动力学性质，通过合成来理解螯合控制的ANSA-茂金属的立体控制机理，4)设计手性4族金属双酰胺前驱体，用于不对称合成芳香族金属茂金属化合物。本研究的第二部分是以烷氧基茂金属烯烃配合物为模型，研究类似的烷基茂金属烯烃阳离子配合物在烯烃聚合中的应用。醇盐模型体系表现出增强的热稳定性，并且不发生烯烃插入，这使得金属-烯烃键的研究成为可能。这个项目将为研究生和博士后提供挑战有机金属合成、现代光谱方法和机理研究的严格和广泛的培训，并促进目标化合物在经济上重要的催化合成中的应用。我们将设计合成对映体选择性催化试剂的路线，并将使用催化烯烃聚合的络合物模型来深入了解这些催化剂的工作原理。

This award by the Inorganic, Bioinorganic and Organometallic Chemistry program supports research by Professor Richard F. Jordan of the University of Chicago to develop efficient methods for the stereoselective synthesis of chiral ansa-metallocenes and to expand the fundamental understanding of the properties of d0 metal olefin complexes that are models for transient intermediates in olefin polymerization reactions. Metallocene complexes of early transition metals, such as Ti, Zr and Hf, are important in organic synthesis and closely related cationic complexes are the active species in olefin polymerizations. Chiral ansa-metallocenes, in which the two cyclopentadienyl rings are linked, are important stereoselective olefin polymerization catalysts and have been employed as enantioselective catalysts or reagents for other olefin reactions. Metallocene compounds with ligands that can control the face-selectivity of cyclopentadienyl ligands will be prepared involving 6-membered chelate rings in bis-amide complexes that adopt twist conformations, which complement 2-fold symmetric rac-metallocenes and strongly disfavor meso-metallocene structures. This first part of this research will: 1) develop streamlined ansa-metallocene syntheses based on chelate-controlled salt-elimination and amine-elimination reactions, 2) establish the generality of this approach for group 4 and group 3/lanthanide ansa-metallocenes with diverse structures, 3) understand the stereocontrol mechanisms in chelate-controlled ansa-metallocenes with synthesis through studies of the conformational and dynamic properties of group 4 metal bis-amide complexes, and 4) design chiral group-4 metal bis-amide precursors for the enantioselective synthesis of ansa-metallocenes.The second part of this research is to use alkoxy metallocene olefin complexes as models for the similar alkyl metallocene olefin cation complexes that are involved in olefin polymerization. The alkoxide model systems exhibit enhanced thermal stability and do not undergo olefin insertion, which enables studies of the metal-olefin bonding. Models are designed to provide a detailed picture of how d0 metal species bind and activate olefins.This project will provide rigorous and broad training for graduate students and postdoctoral fellows in challenging organometallic synthesis, modern spectroscopic methods and mechanistic studies, and facilitate the application of the targeted compounds in economically important catalytic syntheses.Synthetic routes to enantioselective catalytic reagents will be devised and models of complexes that catalyze the polymerization of olefins will be used to gain insight as to how these catalysts operate.