Platform-Supported Pairs of Lewis Acidic Metal Cations to Control and Catalyze Dinitrogen Functionalization

在化学系化学合成（SYN）项目的支持下，加州大学伯克利分校的Polly Arnold教授正在研究f-block分子的结构、键合和反应性，其长期、雄心勃勃的目标是将大气中的氮转化为氨和胺。氮气（N2）是大气的主要成分，也是一种廉价的、化学上无害的原料，可用于工业制备各种重要的化学产品。目前，它是一个单一的商业化反应的原料，Haber-Bosch工艺，将氮转化为氨。这一过程被大规模使用，并提供了世界范围内氮肥的主要来源。然而，它在高温高压下运行，既消耗大量能源，又产生大约1%的全球年二氧化碳排放量。因此，发现更有效的方法将氮转化为有用的项目是极其重要的。该项目旨在开发稀土化合物，这种化合物将在低温和低压下介导氮转化为氨和相关化合物，而不会产生二氧化碳。本文提出的基础研究有望对元素周期表中一些最重原子组成的化合物的化学键的重要而未解的问题作出根本性的贡献。它还将在技术关键的稀土元素化学和可持续催化方面培训未来的劳动力成员，这两个领域都是国家的高度优先科学领域。根据该奖项，阿诺德团队将开发由刚性四酚酸配体支持的双金属稀土和相关的刘易斯酸性金属配合物，其重要且具有挑战性的目标是通过非放射性配合物将二氮N2催化转化为仲硅胺。该计划将根据特定镧系元素和共还原剂的大小、氧化还原电位和刘易斯酸度，确定d轨道和f轨道在稳定还原中间体中的作用，并使新的功能化胺的合成成为可能。由于电子可以通过配体框架存储和传输，因此该计划还旨在梳理金属/配体的贡献，并开发新的低能量方法来将还原等价物传递给N2。该项目将训练学生对敏感稀土化合物的处理和操作，并将这些化合物开发成试剂，用于还原小分子。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With the support of the Chemical Synthesis (SYN) Program of the Chemistry Division, Professor Polly Arnold of the University of California–Berkeley, is studying the structure, bonding, and reactivity of f-block molecules with the long-term, ambitious goal of converting atmospheric nitrogen to ammonia and amines. Nitrogen gas (N2) is the major component of the atmosphere and potentially an inexpensive, chemically benign starting material for the industrial preparation of a vast variety of important chemical products. Currently, it is the feedstock for a single commercialized reaction, the Haber-Bosch process, which converts nitrogen to ammonia. This process is used on an enormous scale and provides the major source of nitrogen fertilizer worldwide. However, it functions at high temperatures and pressures, both consuming much energy and generating roughly 1% of global annual carbon dioxide emissions. Consequently, the discovery of more efficient processes to convert nitrogen to useful projects is extremely important. This project seeks to develop rare earth compounds that will mediate the conversion of nitrogen into ammonia and related compounds at low temperatures and pressures without generating carbon dioxide. The fundamental research proposed herein is expected to make fundamental contributions to important, unanswered questions about the chemical bonding in compounds composed of some of the heaviest atoms in the periodic table. It will also train members of the future workforce in the chemistry of the technology-critical rare earth elements, and in sustainable catalysis, both of which are high priority science areas for the nation.Under this award, the Arnold team will develop bimetallic rare earth and related Lewis acidic metal complexes supported by rigid tetraphenolate ligands with important and challenging goal of arriving at entries into the first catalytic conversion of dinitrogen N2 to secondary silylamines by a non-radioactive complex. The proposed program will work with specific lanthanides and co-reductants, according to their size, redox potentials, and Lewis acidity, to define the role of d- and f-orbitals in the stabilization of reduced intermediates and to enable the synthesis of new functionalized amines. Because electrons can be stored and transported through the ligand framework, the proposed program is also designed to tease apart metal/ligand contributions and develop new, lower-energy ways to deliver the reducing equivalents to the N2. The project will train students is the handling and manipulation of sensitive rare earth compounds and in the development of these into reagents for the reduction of small molecules.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.