Understanding the Reactions of Carbon Dioxide with Late Transition Metal Complexes

将二氧化碳（CO2）转化为更有价值的化合物是一个重要的目标，因为这种废物有可能成为一种现成的、可持续的、无毒的、廉价的化学原料。基于过渡金属的催化剂，如镍或钯，有望加速二氧化碳的反应，因此它们是实用的，但进一步实施需要提高效率。在这个项目中，耶鲁大学的哈扎里博士正在通过实验和计算技术来了解二氧化碳如何与各种过渡金属配合物相互作用。这些知识对于设计改进的二氧化碳利用系统至关重要，因为它将提供如何修改催化剂以及如何改善反应进行条件（温度，压力等）的信息。这项研究有可能增加选择性，以便只形成所需的产物。哈扎里博士参与了与二氧化碳利用有关的一系列外联活动，补充了这项研究。这些活动的重点是来自科学、技术、工程和数学（STEM）学科中代表性不足的少数民族的学生。这些活动包括为纽黑文地区的高中生提供为期一周的能源暑期项目，并为本科生提供在哈扎里博士的实验室进行研究的机会。来自耶鲁大学的哈扎里博士在化学部化学结构、动力学和机理B （CSDM-B）项目的资助下，正在对二氧化碳插入到后过渡金属键的基本理解进行研究。该研究为二氧化碳利用过程中催化剂的设计和反应条件的优化提供了指导。具体地说，二氧化碳插入到基团10钳支撑的过渡金属氢化物、氢氧化物、烷基和芳基的速率正在被测量。正在探索的因素包括金属中心、辅助配体、溶剂和添加剂（如路易斯酸）对二氧化碳插入动力学的影响。一个主要的焦点是发展尺度关系，将二氧化碳插入金属氢化物的速率（动力学性质）与过渡金属氢化物的水合性（热力学性质）联系起来。这样就可以评估与次级配位球效应（如氢键或静电效应）是否稳定二氧化碳插入的过渡态有关的假设。密度泛函理论计算与实验工作并行进行，探测过渡态的结构，确定不稳定中间体的几何形状，并测量水性。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。

The conversion of carbon dioxide (CO2) into more valuable compounds is an important goal due to the potential of this waste product as a readily available, sustainable, non-toxic, and inexpensive chemical feedstock. Catalysts based on transition metals, such as nickel or palladium, show promise speeding up the reactions of carbon dioxide so that they are practical, but improvements in efficiency are required for further implementation. In this project, Dr. Hazari of Yale University is developing an understanding of how carbon dioxide interacts with a variety of transition metal complexes using both experimental and computational techniques. This knowledge is crucial for the design of improved systems for carbon dioxide utilization as it will provide information on how to modify the catalyst as well as how to improve the conditions under which reactions are performed (temperature, pressure, etc.). This research has potential to increased selectivity so that only desired products are formed. The research is complemented by Dr. Hazari’s involvement in a series of outreach activities related to carbon dioxide utilization. These activities focus on students from underrepresented minorities in science, technology, engineering and mathematics (STEM) disciplines. The activities include a one week summer program on energy for high school students in the New Haven area and opportunities for undergraduates to perform research in Dr. Hazari’s laboratory. With funding from the Chemical Structure, Dynamics, and Mechanisms B (CSDM-B) Program of the Chemistry Division, Dr. Hazari from Yale University is developing a fundamental understanding of the insertion of carbon dioxide into late-transition metal bonds. This research provides guidance about the design of catalysts and optimization of reaction conditions for processes involving carbon dioxide utilization. Specifically, the rates of carbon dioxide insertion into Group 10 pincer-supported transition metal hydrides, hydroxides, alkyls, and aryls are being measured. Factors that are being probed include the effects of the metal center, ancillary ligand, solvent, and additives, such as Lewis acids, on the kinetics of carbon dioxide insertion. A major focus is the development of scaling relationships that correlate the rate of carbon dioxide insertion into a metal hydride (a kinetic property), with the hydricity of transition metal hydrides, a thermodynamic property. This enables the evaluation of hypotheses relating to whether secondary coordination sphere effects such as hydrogen bonding or electrostatic effects that stabilize the transition state for carbon dioxide insertion. Density Functional Theory calculations are carried out in parallel with the experimental work and probe the structure of the transition states, determine the geometries of unstable intermediates, and measure hydricity.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.