Nonclassical Oxidation Reactions

在这个由化学部化学催化项目资助的项目中，圣母大学的Seth Brown教授正在开发新型催化剂，利用氧气制造新化合物，并从现有化合物中去除氢。催化剂是一种化合物，它可以加速和引导反应产生所需的产物而不消耗自身。许多催化剂含有一个金属原子和与之结合的周围有机化合物，称为配体，在大多数催化剂中，化学反应发生在金属原子上。布朗教授正在研究如何让配体和金属原子一起参与催化过程，或者自己完成全部催化过程。人们正在研究催化剂的结构特征以及化学键形成或断裂的机制，这些信息被用于设计具有更好催化性能的新配体。由于催化作用占全球国内生产总值的三分之一和大部分商业化学产品和化学过程的过程，发现新的或改进的有机反应催化剂可以对经济发展和增长产生重大影响。调查这些问题的研究团队包括高中生、本科生和研究生，目的是培养他们的技术和智力技能，为他们在科学或工程领域的进一步培训和职业生涯做好准备。布朗教授正在准备新的多齿氧化还原活性配体，以创造“非经典”氧化还原反应可以发生的环境。一个目标是氧原子转移或双氧活化，其中在金属中心形成与氧的键，但在配体上发生氧化还原事件。一个关键的设计元素是使用高配位数，这可以稳定小咬角中间体，如过氧配合物，并允许在金属周围组装足够的配体，在单个位点上聚集多达四个电子。正在探索的第二类反应是基于协调的、纯配体中心的底物1,2-脱氢反应。这些甚至可以通过配位饱和金属配合物进行，这可能导致更大的催化剂寿命。这种反应的范围，以及轨道对称约束将引导这种反应选择性的可能性，正在探索中。新的催化机制经常开辟新的选择性途径，了解哪些电子和结构特征使反应更有效可能导致改进催化剂，影响化学品和化学燃料的使用或生产。一系列的教育材料正在开发中，以帮助入门学生加快化学动力学的实际方法，使学生在学习的早期阶段就参与到工作中来。

In this project funded by the Chemical Catalysis Program of the Chemistry Division, Professor Seth Brown of the University of Notre Dame is developing new types of catalysts to utilize oxygen to make new compounds and to remove hydrogen from existing compounds. Catalysts are compounds that accelerate and direct reactions toward desirable products without themselves being consumed. Many catalysts contain a metal atom and surrounding organic compounds bound to it, called ligands, and in most catalysts the reaction chemistry occurs on the metal atom. Professor Brown is studying ways in which to make the ligand participate in the catalysis along with the metal atom or to perform all of the catalysis itself. The structural features of the catalysts and the mechanisms through which the chemical bonds are made or broken are being studied, and this information is being used to design new ligands that should perform better catalysis. Because catalysis accounts for processes that total one third of the global gross domestic product and a majority of the commercial chemical products and chemical processes, the discovery of new or improved catalysts for organic reactions can have a great impact on economic development and growth. The research team investigating these issues includes high school students, undergraduate students, and graduate students, with the aim of developing their technical and intellectual skills to prepare them appropriately for further training and careers in science or engineering.Professor Brown is preparing new multidentate redox-active ligands to create environments where "nonclassical" redox reactions can take place. One target is oxygen atom transfer or dioxygen activation in which bonds to oxygen will be formed at the metal center, but redox events will take place at the ligands. A key design element is the use of high coordination numbers, which may stabilize small bite angle intermediates such as peroxo complexes and allow the assembly of enough ligands around the metal to marshal up to four electrons at a single site. A second class of reactions being explored is based on concerted, purely ligand-centered 1,2-dehydrogenations of substrates. These can be carried out even by coordinatively saturated metal complexes, which may lead to greater catalyst lifetimes. The scope of such reactions, and the possibility that orbital symmetry constraints will steer the selectivity of such reactions, are being explored. Novel catalysis mechanisms often open up new selectivity pathways, and understanding what electronic and structural features make the reactions more efficient may lead to improved catalysts with impact in the use or production of chemicals and chemical fuels. A series of educational materials are being developed to help bring introductory students up to speed on practical approaches to chemical kinetics, allowing students to be intellectually engaged with the work at an early stage in their studies.