Synthesis, Characterization, and Reactivity Studies of Cerium-Ligand Multiple Bonds and Organometallics and Comparisons with Thorium, Uranium, and Group IV Congeners

在化学系化学合成项目的支持下，宾夕法尼亚大学的Eric Schelter教授和他的研究小组正在研究铈、钍、铀和第四族金属化合物的有机金属化学，特别是那些包含金属配体多重键的元素的配合物。铈是一种稀土金属，但它的性质与其他稀土金属以及元素周期表中围绕它的过渡金属和锕系金属相似。本项目旨在比较铈与这些周围金属的行为，以确定决定铈独特性质的因素。对铈化学的深入了解将有助于铈在催化、材料和化学生物学等领域的应用。这些研究的结果也可能有助于更好地了解稀土金属，稀土金属对可再生能源和国防应用至关重要。该项目将为学生提供稀土处理和操作方面的培训，并有助于在这一重要领域维持训练有素的劳动力。高中学生的动手研究项目也被设想为提供早期接触科学的机会。本课题的总体目标是合成新的金属配体多键结合的铈、铀、钍和IV族金属有机金属化合物。将比较这些金属的光谱性质和反应模式。中心假设是，同结构，四价金属配合物的性质将通知键的差异和4f-/5d共价在这一广泛的元素。将合成铈、铀、钍和IV族元素的金属有机配合物和金属配体多键。用多核核磁共振和x射线吸收光谱对其光谱特性进行了研究。计算方法将应用于模拟光谱性质和了解相对共价贡献成键。经过平衡反应的同位结构配合物也将用于观察铈、钍和铀元素之间键合的动态差异，并延伸到IV族元素。从这项工作中发展出来的基础知识有望为有机金属化合物和相关的光谱信息提供新的和独特的例子，这将扩大对化学键的理解。含稀土元素的材料用于能源和国防工业，目前还没有替代品。发展铈稀土化学，有利于提高稀土选矿分离水平，有利于国家安全。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 support from the Chemical Synthesis program in the Chemistry Division, Professor Eric Schelter and his research group at the University of Pennsylvania are investigating the organometallic chemistry of cerium, thorium, uranium, and Group IV metal compounds, especially complexes of those elements that include metal-ligand multiple bonds. Cerium is a rare-earth metal, but it exhibits properties similar both to other rare-earth metals and to the transition and actinide metals that surround it in the periodic table. This project aims at comparing the behavior of cerium with these surrounding metals in order to determine the factors that determine the unique properties of cerium. A better understanding of cerium chemistry is expected to contribute to the design new applications for cerium in catalytic, materials and chemical biology applications. The results of these studies will also likely contribute to a greater understanding of rare earth metals that are critical for renewable energy and defense applications. The project will provide student training in the handling and manipulation of the rare earths and contribute to the maintenance of a trained work force in this important area. Hands-on research projects for high school students are also envisioned to provide early exposure to science.The overall goal of this project is to synthesize new metal-ligand multiply bonded organometallic compounds of cerium, uranium, thorium, and Group IV metals. The spectroscopic properties and reactivity patterns across these metals will be compared. The central hypothesis is that the properties of isostructural, tetravalent metal complexes will inform on bonding differences and 4f-/5d-covalency across this broad spectrum of elements. Organometallic complexes and metal-ligand multiple bonds of cerium, uranium, thorium, and group IV elements will be synthesized. Their spectroscopic properties will be studied by multi-nuclear NMR and X-ray absorption spectroscopy. Computational methods will be applied to model the spectroscopic properties and to understand the relative covalent contributions to bonding. Isostructural complexes that undergo equilibrium reactions will also be used to observe dynamic differences in bonding across the elements of cerium, thorium and uranium, and extending to the group IV elements. The fundamental knowledge developed from the work is expected to contribute new and unique examples of organometallic compounds and associated spectroscopic information that will broaden understanding of chemical bonding. Rare earth element-containing materials are used in the energy and defense industries and there are currently no substitutes. Advancing cerium/rare earth chemistry will contribute to improving beneficiation and separation of rare earths, and in so doing, contribute to national security.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.