New Early Transition Metal Metallocene Chemistry

该奖项由无机、生物无机和有机金属化学项目颁发，支持芝加哥大学Richard F. Jordan教授的研究，以开发手性环金属茂物立体选择性合成的有效方法，并扩大对烯烃聚合反应中瞬态中间体模型的60种金属烯烃配合物性质的基本理解。Ti、Zr和Hf等早期过渡金属的茂金属配合物在有机合成中起重要作用，密切相关的阳离子配合物是烯烃聚合反应中的活性物质。由两个环戊二烯环相连的手性环金属茂烯是重要的立体选择性烯烃聚合催化剂，已被用作其它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配合物中的6元螯合环，制备了具有控制环戊二烯基配体表面选择性的茂金属化合物，这种配合物补充了2倍对称的非对称茂金属，并且强烈反对中茂金属结构。本研究的第一部分将：1)基于螯合物控制的盐消除反应和胺消除反应，建立流线型的环茂金属合成方法；2)建立该方法在不同结构的4族和3族镧系环茂金属合成中的普遍性；3)通过研究4族金属双酰胺配合物的构象和动力学性质，了解螯合物控制的环茂金属合成中的立体控制机制。4)设计手性基团-4金属双酰胺前体，用于对映选择性合成双金属茂烯。本研究的第二部分是用烷氧基茂金属烯烃配合物作为模型，模拟类似的烷基茂金属烯烃阳离子配合物参与烯烃聚合。醇氧化合物模型系统表现出增强的热稳定性，并且不经历烯烃插入，这使得研究金属-烯烃键成为可能。模型的目的是提供一个详细的图片，如何10种金属结合和激活烯烃。该项目将为具有挑战性的有机金属合成、现代光谱方法和机理研究方面的研究生和博士后提供严格和广泛的培训，并促进目标化合物在经济上重要的催化合成中的应用。对映选择性催化剂的合成路线将被设计出来，催化烯烃聚合的络合物模型将被用来深入了解这些催化剂是如何运作的。

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.