New Computational and Experimental Methods for the Structural Characterization of Homogeneous Catalysts

在无机，生物无机和 有机化学计划，教授克拉克兰迪斯的 威斯康星州麦迪逊大学将承担开发 新的计算和实验工具来阐明 有机金属分子的溶液结构 兰迪斯会 开发适合实验核奥弗豪泽的方法 有机金属分子NMR谱中的效应时程 时间进程是根据 可能的构象。 可能的构象的集合将是 使用力场最小化方法生成， 系统或蒙特卡罗搜索技术。 溶剂 将使用高粘度的混合物来部分消除 NOE的损失由于快速自旋弛豫， 是由小分子的快速旋转引起的。 第二、 一种新的经验力场法（SHAPES）， 专门设计用于描述复杂的几何形状， 将开发含过渡金属的化合物。 两 技术将被应用于确定结构 均相不对称氢化和α-烯烃 催化剂的 研究的最终目的是 确定高立体选择性背后的原因 这些催化剂和预测的新的和更高的 用于这些和其它类型的催化剂的立体选择性催化剂 反应. %%% 确定过渡态结构的新方法 将研究溶液中的金属有机金属分子。 溶液中的复杂分子不断地扭曲， 旋转，随之而来的是整体形状的变化。 之一 研究溶液中分子形状的方法 将利用核磁共振的变化 核奥佛豪泽效应（Nuclear Overhauser Effect） 的存在 各种构象异构体（具有不同构象的分子 溶解的有机金属化合物将被 在解释光谱数据时考虑，以便 提供所有参与异构体的结构信息。 只有一个平均结构可以推导出使用现有的 方法. 第二种方法将允许 用分子力学方法测定结构 专门定制，包括参数， 过渡金属 这些技术已经很好地发展， 小的有机分子和蛋白质， 应用于金属有机化合物结构的计算 分子。 这项工作的最终目标是能够 了解反应中立体选择性的起源 由有机金属化合物催化。 这种反应非常 在化学工业中很重要， 商品、精细和特种化学品的制造。 一个 对催化立体选择性的理解 影响能源和原材料利用等问题。

With funding from the Inorganic, Bioinorganic and Organometallic Chemistry program, Professor Clark Landis of the University of Wisconsin, Madison will undertake the development of new computational and experimental tools for elucidation of solution structures of organometallic molecules. Landis will develop methods for fitting experimental Nuclear Overhauser Effect timecourses in NMR spectra of organometallic molecules with timecourses that are calculated based on a population of possible conformers. Ensembles of possible conformers will be generated using force field minimization methods combined with systematic or Monte Carlo searching techniques. Solvent mixtures of high viscosity will be used to partially eliminate the loss of NOE due to rapid spin relaxation that normally results from the rapid rotation of small molecules. Secondly, a new empirical force field method (SHAPES) that is specifically designed for describing complex geometries of transition metal containing compounds will be developed. Both techniques will be applied to the determination of structures of homogeneous asymmetric hydrogenation and alpha-olefin catalysts. The ultimate aim of the research is the determination of the reasons behind the high stereoselectivity of these catalysts and the prediction of new and more highly stereoselective catalysts for these and other types of reactions. %%% New methods for the determination of structures of transition metal organometallic molecules in solution will be studied. Complex molecules in solutions are constantly twisting and turning, with consequent changes in overall shape. One of the methods to be developed to study molecular shapes in solution will utilize a variation of nuclear magnetic resonance spectroscopy (Nuclear Overhauser Effect). The existence of various conformational isomers (molecules with different twists) of the dissolved organometallic compounds will be considered in the interpretation of the spectral data so as to provide structural information for all participating isomers. Only an average structure can be deduced using existing methods. The second method to be developed will allow for the determination of structures using molecular mechanics methods that are specifically tailored to include parameters for transition metals. Such techniques are well developed for small organic molecules and proteins but have only begun to be applied to the computation of structures of organometallic molecules. The ultimate objective of the work is to be able to understand the origins of stereoselectivity in reactions catalyzed by organometallic compounds. Such reactions are very important in the chemical industry with applications to the manufacture of commodity, fine and specialty chemicals. An understanding of catalytic stereoselectivity potentially influences issues such as energy and raw materials utilization.