Stereocontrolled and Aerobic Oxidative Reactions at High-Valent Nickel Centers

在化学部合成计划的资助下，圣路易斯华盛顿大学化学系的Liviu Mirica博士正在研究镍化合物在重要化学转化中的作用。这些反应包括将两个不同的分子对以更高的选择性偶联(“交叉偶联”)的反应，以及与惰性有机底物与氧气活化有关的反应。金属化合物加速的交叉偶联反应在大量重要的化学品、药物和材料的合成中变得不可或缺。虽然以钯为基础的催化剂是最常用的，但Mirica博士正在合成和研究基于镍(Ni)的催化剂，因为它们可能能够与更广泛的目标分子反应，而且更具特异性。此外，米里卡教授还与西南俄克拉荷马州立大学(SWOSU)的蒂姆·胡宾教授建立了合作关系。SWOSU是俄克拉荷马州的一所地区性大学，有相当数量的学生属于代表性不足的群体。胡宾教授和他的学生合作合成了一些目标催化剂，参观了Mirica实验室，并使用他们的化学系统进行了反应性研究。这一经历让本科生接触到了一所R1研究机构，并激励他们攻读化学方面的高级学位。米里卡教授和他的团队继续与来自西班牙和韩国的合作者密切合作。这种协作体验是为他们在真正的国际环境中工作做好准备的极好的培训基础，非常类似于跨国公司。虽然钯(Pd)基催化剂是交叉偶联反应中最常用的，但镍基交叉偶联催化剂是最近开发的。鉴于它们能够使烷基亲电体和亲核体参与立体专一性或立体选择性转化，因此镍基催化剂很有兴趣。与通常使用抗磁性中间体的Pd介导的转化相比，Ni体系更容易发生单电子氧化还原反应，并导致额外的反应途径。顺磁性Ni(I)和Ni(III)物种的存在使反应性表征变得更加困难。Mirica博士的实验室正在合成由柔性多齿配体支撑的分离的有机金属镍(III)和镍(IV)配合物，并详细研究它们参与重要的化学转化，如立体控制的C-C键形成反应和高价镍中间体介导的有氧氧化反应。这项工作与C-H官能化和C-C/C-杂原子键的形成反应有直接关系。Mirica博士还招募了来自不同背景的研究生和本科生，并为他们提供跨越无机、有机和物理化学的跨学科培训。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

With funding from the Synthesis Program of the Chemistry Division, Dr. Liviu Mirica of the Department of Chemistry at Washington University in St. Louis is investigating the role of nickel compounds in important chemical transformations. These include reactions that couple two different molecular partners ("cross-coupling") with improved selectivity, as well as reactions related to the activation of inert organic substrates with oxygen. Cross-coupling reactions sped up by metal-containing compounds have become indispensable in the synthesis of a large number of important chemicals, pharmaceuticals, and materials. While palladium-based catalysts are the most commonly used, Dr. Mirica is synthesizing and studying nickel (Ni)-based catalysts as they may be able to react with a wider variety of target molecules and with more specificity. In addition, Professor Mirica has established a collaboration with Professor Tim Hubin from Southwestern Oklahoma State University (SWOSU), a regional university in Oklahoma that has an appreciable amount of students that belong to underrepresented groups. Professor Hubin and his students collaborate on the synthesis of some of the targeted catalysts, visiting the Mirica lab, and performing reactivity studies using their chemical systems. This experience exposes the undergraduate students to an R1 research institution, and inspires them to pursue advanced degrees in chemistry. Professor Mirica and his group continue to work closely with collaborators from Spain and South Korea. This collaborative experience is an excellent training ground to prepare them to work in a true international environment, very similar to a multinational corporation.While palladium (Pd)-based catalysts are arguably the most commonly used in cross-coupling reactions, Ni-based cross-coupling catalysts have been developed recently. Given their ability to engage alkyl electrophiles and nucleophiles in stereospecific or stereoselective transformations the Ni-based catalysts are of interest. By comparison to the Pd-mediated transformations that generally employ diamagnetic intermediates, the Ni systems can more easily undergo one-electron redox reactions and lead to additional reaction pathways. The presence of paramagnetic Ni(I) and Ni(III) species makes reactivity characterization more difficult. Dr. Mirica's laboratory is synthesizing isolated organometallic Ni(III) and Ni(IV) complexes supported by flexible multidentate ligands and studying in detail their involvement in important chemical transformations such as stereocontrolled C-C bond formation reactions and aerobic oxidative reactions mediated by high-valent Ni intermediates. This work has direct relevance to C-H functionalization and C-C / C-heteroatom bond formation reactions. Dr. Mirica is also recruiting graduate and undergraduate students from different backgrounds and providing them with an interdisciplinary training that spans inorganic, organic, and physical chemistry.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.