CAS: Collaborative Research: Electronic Structure/Function Relationships Underpinning Atom Transfer Reactivity

在化学系化学结构、动力学和机理-B计划的支持下，哈佛大学化学和化学生物系的西奥多·贝特利教授和康奈尔大学化学和化学生物学系的凯尔·兰开斯特教授正在研究自由基配体过渡金属配合物的电子结构。该合作项目旨在合成和表征新型金属-配体多键(MLMB)系统，该系统可以向碳氢键底物提供不同的功能。选择性地将官能团结合到非活性碳氢键中的能力代表着在将廉价的化学原料(例如碳氢化合物)转化为增值分子(例如药物前体)方面的重大进展。该联合项目将利用兰开斯特集团进行无机光谱分析的专业知识和Betley集团在合成方面的专业知识，探索含氮和氮配体的单核和三核过渡金属络合物的电子结构和反应性的周期性趋势。该项目位于无机和有机金属化学的交界处，因此非常适合各级科学家的教育。这些团体为当地小学和高中的K-12年级学生组织和参与互动示范。在这里，学生们被邀请参加一系列实验，并在他们的实验室观察化学现象。该项目的主要目标是探索金属-配体组成及其变化的氧化水平如何改变这些配位络合物的最终物理性质和反应性。为此，他们试图合成具有类硝基和硝基功能的单核和三核配合物，以检查和利用它们的反应化学。因此，他们致力于解决以下问题：(1)在MLMB缔合中，分子氧化还原过程是如何沿着初级氧化还原对分布的？(2)MLMB的分子氧化还原变化是如何改变氧化基团转移过程的？(3)对于簇结的亚胺/硝基络合物，氧化还原负荷是如何局部化的？(4)对于簇结结合的官能团，配体空穴特征能否在氧化过程中积累？目标开壳单元将被设计成支持广泛的分子氧化态，改变MLMB或协同结合部分的电子结构。他们将利用N K边XAS作为手段来探索配位N供体的亚八位组特征，并量化配位络合物中的M-N共价性。这些数据将被用来对MLMB和基于簇的复合体在第一过渡后期系列的反应性(亲核与亲电)的周期性趋势进行合理化。这一奖项反映了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 the support of the Chemical Structure, Dynamics & Mechanisms-B Program of the Chemistry Division, Professors Theodore Betley of the Department of Chemistry and Chemical Biology at Harvard University and Kyle Lancaster of the Department of Chemistry and Chemical Biology at Cornell are investigating the electronic structure of radicaloid ligand transition metal complexes. This collaborative project seeks to synthesize and characterize novel metal-ligand multiple bond (MLMB) systems that can deliver diverse functionalities into carbon hydrogen bond substrates. The ability to selectively incorporate functionality into unactivated carbon hydrogen bonds represents a significant advance in converting inexpensive chemical feedstocks (e.g. hydrocarbons) to value-added molecules (e.g., pharmaceutical precursors). The joint project will leverage the combined expertise of the Lancaster group to perform inorganic spectroscopy and the Betley group’s expertise in synthesis to explore periodic trends in the electronic structure and reactivity of mono- and trinuclear transition metal complexes bearing nitrenoid and nitrido ligands. The project lies at the interface of inorganic and organometallic chemistry and is therefore well suited to the education of scientists at all levels. These groups organize and participate in interactive demonstrations for students at the K-12 level from local grade schools and high schools. Here the students are invited to participate in a series of experiments and observe chemical phenomena at their laboratories. The overarching goals of the project are to probe how metal-ligand compositions and their changing oxidation levels alter the resultant physical properties and reactivity for these coordination complexes. To this end, they seek to synthesize mono- and trinuclear complexes featuring nitrenoid and nitrido functionalities to examine and harness their reaction chemistry. Thus, they aim to address the following questions: (1) How are molecular redox processes distributed along the primary redox pair in MLMB associations? (2) How do molecular redox changes of MLMBs alter oxidative group transfer processes? (3) For cluster-bound imido/nitrido complexes, how is the redox load localized? (4) For cluster-bound functionalities, can ligand hole character accumulate under oxidative processes? The target open-shell units will be designed to support a breadth of molecular oxidation states, altering the electronic structure of the MLMB or cooperatively bound moiety. They will leverage N K-edge XAS as means to probe the sub-octet character of coordinated N-donors and to quantify M–N covalency in coordination complexes. These data will be used to rationalize periodic trends in the reactivity (nucleophilic vs. electrophilic) of MLMB and cluster-based complexes across the late first transition series.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.