New Early Transition Metal Metallocene Chemistry

该奖项由无机，生物无机和有机化学计划支持理查德F教授的研究。Jordan等人的研究，开发了立体选择性合成手性柄型烯烃的有效方法，并扩展了对d 0金属烯烃络合物性质的基本理解，d 0金属烯烃络合物是烯烃聚合反应中瞬时中间体的模型。 钛、锆、铪等前过渡金属的茂金属配合物在有机合成中具有重要的应用价值，而与之密切相关的阳离子配合物是烯烃聚合反应的活性物种。 手性柄型双烯是一类重要的立体选择性烯烃聚合催化剂，在其它烯烃反应中也被用作对映选择性催化剂或试剂。 将制备具有可以控制内消旋配体的面选择性的配体的茂金属化合物，其涉及采用扭曲构象的双酰胺络合物中的6元螯合环，其补充2倍对称外消旋茂金属并且强烈地不利于内消旋茂金属结构。 本研究的第一部分将：1）开发基于螯合物控制的盐消除和胺消除反应的流线型柄型-茂金属合成，2）建立该方法对于具有不同结构的第4族和第3族/镧系柄型-茂烯的通用性，3）了解螯合物控制的柄节的立体控制机制，通过研究第4族金属双酰胺配合物的构象和动力学性质，和4）设计手性第4族金属双酰胺前体用于对映选择性合成ansa-本研究的第二部分是使用烷氧基茂金属烯烃络合物作为参与烯烃聚合的类似烷基茂金属烯烃阳离子络合物的模型。 醇盐模型系统表现出增强的热稳定性，不进行烯烃插入，这使得研究的金属-烯烃键合。 模型旨在提供d 0金属物种如何结合和活化烯烃的详细图片。该项目将为研究生和博士后研究员提供严格和广泛的培训，包括具有挑战性的有机金属合成，现代光谱方法和机理研究，并促进目标化合物在经济上重要的催化合成中的应用。将设计对映选择性催化剂的合成路线，催化烯烃聚合的络合物的研究将被用来深入了解这些催化剂是如何工作的。

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.