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

均相催化剂结构表征的新计算和实验方法

• 批准号: 9112988
• 负责人: Clark Landis
• 金额: $ 23.67万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1991
• 资助国家: 美国
• 起止时间: 1991-12-01 至 1994-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9112988&HistoricalAwards=false
• 关键词: New; Computational; Experimental; Methods; Structural

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.

在无机化学、生物无机化学和金属有机化学项目的资助下，威斯康星大学麦迪逊分校的克拉克·兰迪斯教授将负责开发新的计算和实验工具，以阐明有机金属分子的溶液结构。兰迪斯将开发一种方法，将有机金属分子核磁共振谱中的实验核Overhaser效应时间过程与基于可能构象群计算的时间过程进行拟合。可能构象的系综将使用力场最小化方法与系统或蒙特卡罗搜索技术相结合来产生。高粘度的混合溶剂将被用来部分消除NOE的损失，这是由于通常由小分子的快速旋转引起的快速自旋松弛。其次，将开发一种新的经验力场方法(形状)，该方法专门用于描述含过渡金属化合物的复杂几何结构。这两种技术都将应用于均相不对称加氢催化剂和α-烯烃催化剂的结构测定。研究的最终目的是确定这些催化剂高立体选择性背后的原因，并预测用于这些反应和其他类型的反应的新的、更高立体选择性的催化剂。将研究测定溶液中过渡金属有机金属分子结构的新方法。溶液中的复杂分子不断地扭曲和转动，从而导致整体形状的变化。要开发的研究溶液中分子形状的方法之一将利用核磁共振波谱的一种变化(核奥弗豪泽效应)。在解释光谱数据时，将考虑溶解的有机金属化合物的各种构象异构体(具有不同扭曲的分子)的存在，以提供所有参与异构体的结构信息。使用现有方法只能推导出平均结构。将开发的第二种方法将允许使用专门为包括过渡金属参数而定制的分子力学方法来确定结构。这类技术在有机小分子和蛋白质方面已经得到了很好的发展，但才刚刚开始应用于有机金属分子结构的计算。这项工作的最终目标是能够理解有机金属化合物催化反应中立体选择性的起源。这种反应在化学工业中非常重要，应用于商品、精细和特种化学品的制造。对催化立体选择性的理解可能会影响到能源和原材料的利用等问题。