Investigation of Palladium-Dioxygen Chemistry

该奖项授予威斯康星大学麦迪逊分校的Shannon S. Stahl教授，他将继续研究使用均相钯催化剂，用分子氧选择性氧化有机化学品。这些反应通过两阶段机制进行，包括(1)Pd（II）介导的有机底物氧化和(2)分子氧对还原催化剂的再氧化。为了促进以O2作为化学计量氧化剂的钯催化氧化，PI将研究二氧与定义明确的钯配合物之间反应的基本机制。通过制备合适的Pd(0)或Pd（II）前驱体并研究其在有氧条件下的反应性，将评估在催化条件下还原钯的三种不同机制的可行性。计算研究将阐明电子结构对这些反应的贡献。由于二氧在二亚配位钯中心与缺电子烯烃（如苯醌）进行可逆交换，为了更好地理解二氧和烯烃与钯的反应之间的关系，将对这些反应的动力学和热力学方面进行研究。这些研究，连同使用苯醌作为氧化剂的催化反应的机理表征，应该提供有助于在催化中用二氧取代苯醌的见解。最后，我们将研究苯醌和双氧诱导Pd(II)-C键氧化功能化的能力。反应途径的机理表征将有助于钯氧化催化中二氧偶联转换方法的改进，这对未来好氧C-H氧化方法的发展具有重要意义。将与威斯康辛大学化学教育研究所所长约翰·摩尔教授合作，为初中和高中的科学学生开发一个互联网资源，以易于理解和教育的形式展示现代学术研究。来自传统上代表性不足的群体的本科生将通过P.I.参与拟议的研究活动他参加了威斯康星大学麦迪逊分校的本科生研究学者项目。

This award to Professor Shannon S. Stahl at the University of Wisconsin at Madison will continue work on the selective oxidation of organic chemicals with molecular oxygen using homogeneous palladium catalysts. These reactions proceed by a two-stage mechanism consisting of (1) Pd(II)-mediated oxidation of the organic substrate and (2) reoxidation of the reduced catalyst by molecular oxygen. In order to facilitate palladium-catalyzed oxidation with O2 as the stoichiometric oxidant, the PI will investigate fundamental mechanisms of reactions between dioxygen and well-defined palladium complexes. The viability of three different mechanisms proposed for reoxidation of reduced palladium under catalytic conditions will be assessed, by preparing suitable Pd(0) or Pd(II) precursors and investigating their reactivity under aerobic conditions. Computational studies will elucidate the electronic structural contributions to these reactions. As dioxygen undergoes reversible exchange with electron-deficient alkenes, such as benzoquinone, at diiminecoordinated Pd centers, the kinetic and thermodynamic aspects of these reactions will be investigated in order to gain a better understanding of the relationship between dioxygen and alkene reactions with palladium. These studies, together with the mechanistic characterization of catalytic reactions that employ benzoquinone as the oxidant, should provide insights that will facilitate the replacement of benzoquinone with dioxygen in catalysis. Finally, the ability of benzoquinone and dioxygen to induce oxidative functionalization of Pd(II)-C bonds will be studied. The mechanistic characterization of reaction pathways will assist the development of improved methods for dioxygen-coupled turnover in palladium oxidation catalysis, which has implications for the future development of aerobic C-H oxidation methods. A collaboration with Prof. John Moore, director of the Institute for Chemical Education at the University of Wisconsin, will be undertaken to develop an Internet resource for junior high and high school science students that presents modern academic research in an accessible and educational format. Undergraduate students from traditionally underrepresented groups will be involved in the proposed research activities through the P.I.'s participation in the Undergraduate Research Scholars Program at UW-Madison.