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

在化学系化学合成计划的支持下，宾夕法尼亚大学的Eric Schelter教授和他的研究小组正在研究Ce、Th、U和第四族金属化合物的有机金属化学，特别是包括金属-配体多键的这些元素的络合物。Ce是一种稀土金属，但它的性质与其他稀土金属相似，也与元素周期表中围绕它的过渡金属和氡系金属相似。该项目旨在比较Ce与这些周围金属的行为，以确定决定Ce独特性质的因素。对Ce化学的更好理解将有助于设计Ce在催化、材料和化学生物学应用中的新应用。这些研究的结果还可能有助于更好地了解稀土金属，这些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处理和操纵稀土的培训，并有助于维持这一重要领域中训练有素的劳动力队伍。高中生的动手研究项目也被设想为提供早期接触科学的机会。该项目的总体目标是合成新的金属-配体多键有机金属化合物，包括Ce、U、Th和第四族金属。我们将比较这些金属的光谱性质和反应模式。中心假设是，等结构的四价金属络合物的性质将影响这种广泛的元素的成键差异和4f-/5d-共价性。将合成有机金属络合物和金属-配体多键，包括Ce、U、Th和IV族元素。它们的光谱性质将通过多核核磁共振和X射线吸收光谱进行研究。计算方法将被用来模拟光谱性质，并理解相对共价对成键的贡献。经过平衡反应的等结构络合物也将被用来观察跨Ce、Th和U元素以及延伸到IV族元素的成键的动态差异。从这项工作中发展出来的基础知识预计将有助于提供新的和独特的有机金属化合物的例子和相关的光谱信息，这些信息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。推动Ce/稀土化学的发展将有助于改善稀土的选矿和分离，并因此有助于国家安全。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 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.