Metal versus Ligand-Centered Oxidizing Equivalents in Hydrocarbon Oxidations

无机，生物无机和有机化学计划的这一奖项支持了密苏里州大学的Pericles Stavropoulos教授的研究，以开发和机械研究铁基烃氧化系统，该系统可以将氧化能力储存在高价金属氧合位点上，但也有可能将氧化当量作为配体中心的自由基。 为了实现这一点，将合成合适的配体和铁试剂，其在氧代供体的存在下，应同时支持高价Fe（IV）=O单元和以配体为中心的p自由基。 这些将用于脂肪族和不饱和烃的催化氧化，并收集表明选择性氧化途径的初始机理数据。从金属和配体为中心的氧化等价物的存在下产生的机制的影响，在其各自的作用，在介导烃活化过程将被确定。 建议的研究工作集中在三脚架三氨基胺配体，其富电子的字符应有助于稳定高价金属网站。 这些配体具有邻苯二胺部分，其可以在氧化配体重排后保留一个或多个氧化当量。 为了获得对生成真实[LoFe（IV）=O]部分所需的立体电子参数的控制，将进行涉及含[LFe（II）]和[LFe（III）]的化合物和氧代供体分子的反应性研究，以评价每种配体。 将在烷烃和烯烃的催化氧化中测试最合适的候选物，以通过与涉及无差别氧化化学的不期望的途径进行比较来评估该过程的选择性。 金属为中心的事件将通过表征金属/氧代供体相互作用中产生的关键中间体来检查。 所提出的工作旨在更好地定义实现难以捉摸的Fe（V）=O单元所需的要求及其与制备用于烃选择性氧化为商品羰基合成产物的有用试剂的关系。 更广泛的影响超出了博士后，研究生和本科生研究人员的培训，包括通过一个移动的实验室，使动手实验和讨论的双氧化学和生产书面材料，这些群体参与农村K-12学生。

This award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports research by Professor Pericles Stavropoulos at the University of Missouri at Rolla to develop, and mechanistically investigate, iron-based, hydrocarbon-oxidizing systems that can store oxidizing power onto a high-valent metal-oxo site, but also have the potential to delocalize oxidizing equivalents as ligand-centered radicals. To accomplish this, suitable ligands and iron reagents, which, in the presence of oxo donors, should simultaneously support a high-valent Fe(IV)=O unit and a ligand-centered p radical will be synthesized. These will be employed in the catalytic oxygenation of aliphatic and unsaturated hydrocarbons, and initial mechanistic data that indicate selective oxidation pathways will be collected. Mechanistic implications arising from the presence of both metal- and ligand-centered oxidizing equivalents, in relation to their individual roles in mediating hydrocarbon-activation processes will be determined. The proposed research work concentrates on tripodal trisamidoamine ligands, whose electron-rich character should help stabilize high-valent metal sites. These ligands possess o-phenyldiamine moieties, which, can retain one or more oxidizing equivalents following oxidative ligand rearrangement. In an effort to gain control over those stereo-electronic parameters necessary for the generation of an authentic [LoFe(IV)=O] moiety reactivity studies are will be undertaken involving [LFe(II)] and [LFe(III)] containing compounds and oxo-donor molecules to evaluate each ligand. The most suitable candidates will be tested in catalytic oxygenations of alkanes and olefins, to assess the selectivity of the process by comparison to undesirable pathways involving indiscriminate oxygenation chemistry. Metal-centered events will be examined by characterizing key intermediates generated in metal/oxo-donor interactions. The proposed work aims at a better definition of the requirements needed to attain the elusive Fe(V)=O unit and its relation to preparing useful reagents for the selective oxygenation of hydrocarbons to commodity oxo products. Broader impacts extend beyond the training of post-doctoral, graduate, and undergraduate researchers to include involving rural K-12 students through a mobile laboratory that enables hands-on experimentation and discussion of dioxygen chemistry and producing written materials for these groups.