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铈，钍，铀和第IV族金属化合物的有机金属化学，特别是包括金属配体多重键的这些元素的络合物。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。该项目旨在比较铈与周围金属的行为，以确定决定铈独特性质的因素。更好地了解铈化学有望有助于设计铈在催化，材料和化学生物学应用中的新应用。这些研究的结果也可能有助于更好地了解对可再生能源和国防应用至关重要的稀土金属。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一支训练有素的工作队伍。高中生的动手研究项目也被设想为提供早期接触科学。该项目的总体目标是合成新的金属配体多键合的铈，铀，钍和第四族金属的有机金属化合物。将比较这些金属的光谱特性和反应模式。核心假设是，同构的四价金属络合物的性质将在整个这一广泛的元素中提供键合差异和4f-/5d-共价性的信息。将合成铈、铀、钍和第IV族元素的有机配合物和金属-配体多重键。它们的光谱性质将通过多核NMR和X射线吸收光谱进行研究。计算方法将被应用到模拟的光谱特性，并了解相对共价键的贡献。经历平衡反应的同构复合物也将用于观察铈、钍和铀元素之间的键合动态差异，并扩展到IV族元素。从工作中发展的基础知识预计将有助于有机金属化合物和相关光谱信息的新的和独特的例子，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，目前没有替代品。推进铈/稀土化学将有助于改善稀土的提纯和分离，从而为国家安全做出贡献。该奖项反映了NSF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.