CAREER: N-heterocyclic Phosphenium Cation-Containing Pincer Ligands: A Chelating Analogue of the Nitrosyl Ligand and its Non-Innocent Behavior

布兰迪斯大学的克里斯汀·M·托马斯教授将凭借化学催化项目的这一奖项，专注于开发一系列用于催化的新的氧化还原非无害钳形配体。她和她的学生开发了一种新的三齿钳形配体，其中包含一个中心的N-杂环膦(NHP)单元。虽然N-杂环卡宾(NHC)配体的催化应用已经得到了广泛的探索，但它们的磷类似物NHP在过渡金属催化中的应用还没有得到评价，对它们的配位化学也知之甚少。Thomas教授和他的同事设计了一种含有NHP的双膦钳形配体，作为一种方法，可以对NHP配体的过渡金属化学进行更广泛的研究。Thomas小组的初步结果有力地支持了与亚硝酰配体的类比，因此NHP作为氧化还原活性配体支持两电子转换的能力是一条很有前途的途径。Thomas教授和她的团队将研究新的NHP-双膦配体与各种过渡金属的配位化学，并探索由NHP单位促进的两电子转换。计算和电化学方法将被用来评估NHP络合物中氧化还原诱导的转化，并将研究新的含NHP的多齿配体。由于多电子氧化还原反应在催化中的重要性，本研究项目的最终目标是利用这些亚硝基和NHCS的类似物来促进催化转化，如C-C或C-X键的形成或断裂反应、转移氢化、交叉偶联和其他sigma键激活过程。所设计的配体具有在不太容易发生两电子转换的金属上支持双电子氧化还原化学的潜力。这包括第一排过渡金属和早期过渡金属，这两种金属都比用于催化的传统贵金属如铂、钯和铑更便宜、更自然丰富。除了对催化的具体贡献外，PI还将利用这笔资金培养对化学感兴趣的本科生的发展，并通过与当地科学博物馆、学校和课外俱乐部的密切合作，培养K-8学生对科学的兴趣。

With this award from the Chemical Catalysis Program, Professor Christine M. Thomas from Brandeis University will focus on developing a new series of redox non-innocent pincer ligands for use in catalysis. She and her students have developed a new class of tridentate pincer ligand incorporating a central N-heterocyclic phosphenium (NHP) unit. While catalytic applications of N-heterocyclic carbene (NHC) ligands have been explored extensively, their phosphorus analogues NHPs have not been evaluated in transition metal catalysis, and far less is known about their coordination chemistry. Professor Thomas and coworkers have designed an NHP-containing diphosphine pincer ligand as a method to allow more extensive studies into the transition metal chemistry of NHP ligands. Preliminary results from the Thomas' group strongly support an analogy to nitrosyl ligands, and thus the ability of NHPs to function as redox active ligands to support two-electron transformations is a promising avenue. Professor Thomas and her group will be investigating the coordination chemistry of the new NHP-diphosphine ligands with a wide variety of transition metals and exploring two-electron transformations facilitated by the NHP unit. Computational and electrochemical methods will be used to evaluate the redox-induced transformations in NHP complexes and new NHP-containing multidentate ligands will be investigated. Owing to the importance of multi-electron redox transformations in catalysis, the ultimate goal of the proposed research project is to utilize these analogues of both nitrosyls and NHCs to facilitate catalytic transformations such as C-C or C-X bond forming or breaking reactions, transfer hydrogenation, cross-coupling and other sigma-bond activation processes. The designed ligands have the potential to support two-electron redox chemistry at metals that are less prone to undergo two-electron transformations. This includes first row transition metals and early transition metals, both of which are cheaper and more naturally abundant than the traditional noble metals used in catalysis such as platinum, palladium and, rhodium. In addition to specific contributions to catalysis, the PI will use the funds to fostering the development of undergraduates interested in chemistry, and to cultivate and interest in science among K-8 students by working closely with local science museums, schools, and after-school clubs.