Towards a better understanding of the reactivity of nonheme iron-oxido systems

更好地了解非血红素铁氧化系统的反应性

• 批准号: 495395668
• 负责人: Professor Dr. Peter Comba
• 金额: --
• 依托单位: Anorganisch-Chemisches Institut
• 依托单位国家: 德国
• 项目类别: Research Units
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/495395668?language=en
• 关键词: Towards; better; understanding; reactivity; nonheme

The iron-oxido-chlorido complex [(L)FeIV=O(Cl)]+, where L is the tetradentate bispidine 2,4-di(pyridine-2-yl)-3,7-diazabicyclo[3.3.1]nonane-1-one that enforces a cis-disposition of the oxido and chlorido groups has an intermediate spin electronic ground state, leads to selective halogenation with cyclohexane as substrate and is the fastest known nonheme ferryl oxidant. An interesting question is, how much the observed reactivity relates to the FeIV/III=O redox potential, how much to the electrophilicity of the oxido-group and how much it depends on the quintet-triplet energy gap of the ferryl complex. These are fundamental questions for nonheme iron-oxido systems in general, and the proposal aims to find answers to these questions on the basis of experiments and computational work involving the bispidine complexes as well as other systems studied in the research unit. The problem with the redox potential is that it so far is not clear whether any of the published FeIV/III=O redox potentials is accurate and correct, and the various available computational methods have the problem that they need to be validated and calibrated with at least one accurate and reliable experimental data set. Part of the current project aims at solving this problem. The other and most interesting observation is the enormous reactivity of these intermediate-spin systems, and preliminary computational as well as experimental data indicate that this is due to a very small triplet-quintet energy gap. These data need to be confirmed with a set of additional experiments and theoretical studies. This will primarily involve subtle variations of the ligand field, and these are synthetically possible, i.e. up to a dozen examples with the tetradentate bispidine platform and a variation of the donor strengths are available. In terms of data that will be explored experimentally and combined with quantum-chemical analyses, the zero-field splitting (field-Mössbauer and HF-EPR spectroscopy) is the main spectroscopic target. Together with elaborate cryo-stopped-flow kinetics, this might allow us to obtain experimental information on the quintet-triplet energy gap of our ferryl complexes, and this would be an important information for a validation of the computational data.

铁-氧化物-氯络合物[（L）FeIV=O（Cl）]+，其中L是四齿双吡啶2，4-二（吡啶-2-基）-3，7-二氮杂双环[3.3.1]壬烷-1-酮，其强制氧化物和氯基团的顺式排列，具有中间自旋电子基态，导致以环己烷为底物的选择性卤化，并且是已知最快的非血红素铁基氧化剂。一个有趣的问题是，所观察到的反应性有多少与FeIV/III=O的氧化还原电位有关，有多少与氧化基团的亲电性有关，以及有多少取决于铁基络合物的五重态-三重态能隙。这些都是一般的非血红素铁氧化物系统的基本问题，该提案的目的是在涉及bispidine络合物以及研究单位研究的其他系统的实验和计算工作的基础上找到这些问题的答案。氧化还原电位的问题在于，到目前为止还不清楚任何已公布的FeIV/III=O氧化还原电位是否准确和正确，并且各种可用的计算方法存在的问题是，它们需要用至少一个准确和可靠的实验数据集进行验证和校准。目前项目的一部分旨在解决这一问题。另一个也是最有趣的观察是这些中间自旋系统的巨大反应性，初步的计算和实验数据表明，这是由于一个非常小的三重态-五重态能隙。这些数据需要通过一系列额外的实验和理论研究来证实。这将主要涉及配体场的细微变化，并且这些是合成上可能的，即多达十几个具有四齿bispidine平台的实例和供体强度的变化是可用的。根据将通过实验探索并结合量子化学分析的数据，零场分裂（场穆斯堡尔谱和HF-EPR谱）是主要的光谱目标。再加上详细的低温停流动力学，这可能使我们能够获得有关铁基复合物的五重态-三重态能隙的实验信息，这将是验证计算数据的重要信息。