RUI: Large Kinetic Isotope Effects as Mechanistic Indicators in Organometallic Chemistry

在化学系化学结构、动力学和机制B项目的支持下，里德学院化学系的米里亚姆·A·鲍林正在与本科生研究人员合作，研究化学反应的基本机制，并将其应用于更绿色的替代燃料。研究反应速率是研究反应如何进行的一个主要工具。已经观察到，一些涉及氢的反应比相应的与氢的反应要快得多。研究人员的目标是确定导致这种不寻常观察的机制，这可能有助于更好地理解化学反应。此外，该小组正在与高中化学教师合作，研究回收道路泥土中的钯作为催化剂，这可能会吸引更多的学生对STEM(科学、技术、工程和数学)感兴趣。在对具有应用前景的有机金属催化剂进行机理研究时，偶尔会观察到异常大的动力学同位素效应。大Kies的机制起源还不是很清楚，通常被归因于质子隧道效应。这项研究包括两个体系的机理研究：质子化反应从铂的甲基络合物中释放出甲烷，以及Ir-Ru双金属催化剂上的甲酸脱氢反应。为了确定这些系统中大Kie的来源，将进行动力学研究，同时系统地调整变量，如反应浓度、化学计量和温度、有机金属碎片的性质和酸。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 support from the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Miriam A. Bowring of the Department of Chemistry at Reed College is working with undergraduate researchers to study the fundamental mechanisms of chemical reactions with potential applications to greener alternative fuels. One main tool for finding out how reactions work is the study of reaction rates. It has been observed that some reactions involving hydrogen are much faster than expected compared to the corresponding reactions with deuterium. The researchers aim to determine the mechanisms that cause such unusual observation, which could lead to improved understanding of chemical reactivity. Furthermore, the group is collaborating with high school chemistry teachers on research in reclaiming palladium in road dirt as a catalyst, which may attract broader student interests in STEM (science, technology, engineering and mathematics). Anomalously large kinetic isotope effects (KIEs) are occasionally observed during mechanistic investigations of promising organometallic catalysts. The mechanistic origins of large KIEs are not well understood, and are often ascribed to proton tunneling. The proposed research encompasses mechanistic study of two systems with large observed KIEs: protonolysis to release methane from platinum methyl complexes, and formic acid dehydrogenation with an iridium-ruthenium bimetallic catalyst. To determine the origins of the large KIEs in these systems, kinetic studies will be performed while systematically adjusting variables such as reaction concentration, stoichiometry, and temperature, properties of the organometallic fragments, and the acid.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.