Competitive Intramolecular Amination as a Clock for Iron-Catalyzed Nitrene Transfer,Inorganic Chemistry

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Competitive Intramolecular Amination as a Clock for Iron-Catalyzed Nitrene Transfer
Inorganic Chemistry ( IF 4.3 ) Pub Date : 2019-01-10 00:00:00 , DOI: 10.1021/acs.inorgchem.8b02284
Caitlin M. Anderson ₁ , Ahmed M. Aboelenen ₁ , Michael P. Jensen ₁

Affiliation

Reaction of the complex [(Tp^Ph,Me)Fe^II(NCMe)₃]BF₄, where Tp^Ph,Me = hydrotris(3-phenyl,5-methyl-1-pyrazolyl)borate, with the iodonium heteroylide PhI═NTs (1.5 equiv) is proposed to result in the insertion of N-tosylnitrene into one C–H bond at the ortho ring position of a 3-pyrazole phenyl substituent; subsequent deprotonation of the nascent aniline and one-electron oxidation of iron forms TsNH₂ (0.5 equiv) as a coproduct. The covalent ligand modification and oxidation results in an intense purple-brown anilinato–iron(III) LMCT chromophore. This intramolecular reaction is utilized as a consistent clock to determine relative rates of competitive intermolecular nitrene transfer to added substrates, specifically to para-substituted styrenes and thioanisoles. Prior addition of substrate to the reaction of PhI═NTs with the iron(II) complex attenuates the CT absorbance of the equilibrium solution. Fitting of the concentration-dependent absorption data gives the ratio of intra- versus intermolecular nitrene transfer. Because the former is independent of substrate, ratios for various substrates are directly comparable, and this approach enables acquisition of data for a single substrate under nearly stoichiometric, as opposed to competitive catalytic, conditions. Hammett analyses of such data are consistent with an electrophilic intermediate consistent with known or suspected imidoiron(IV) complexes. Because this intermediate was not observed directly, plausible geometric and electronic structures were modeled and assessed using density functional theory.

中文翻译：

竞争性分子内胺化反应作为铁催化的丁二烯转移的时钟

络合物[（Tp ^Ph，Me）Fe ^II（NCMe）₃ ] BF _4的反应，其中Tp ^Ph，Me =氢三（3-苯基，5-甲基-1-吡唑基）硼酸酯与碘鎓杂化物PhI═NTs提出（1.5当量）可导致N-甲苯磺腈在3-吡唑苯基取代基的邻环位置插入一个CH键。随后新生苯胺的去质子化和铁的单电子氧化形成TsNH ₂（0.5当量）作为副产品。共价配体的修饰和氧化导致强烈的棕褐色苯胺基铁（III）LMCT发色团。该分子内反应用作一致的时钟，以确定竞争性分子间氮烯转移至添加的底物（特别是对位底物）的相对速率取代的苯乙烯和硫代苯甲醚。在PhI toNTs与铁（II）配合物的反应中预先添加底物会减弱平衡溶液的CT吸光度。浓度依赖性吸收数据的拟合给出了分子内与分子间腈转移的比率。由于前者独立于底物，因此各种底物的比率是直接可比的，并且该方法能够在接近化学计量的条件下（与竞争性催化条件相比）采集单个底物的数据。此类数据的Hammett分析与与已知或怀疑的亚铁（IV）配合物相符的亲电子中间体相符。由于未直接观察到该中间体，因此使用密度泛函理论对合理的几何和电子结构进行了建模和评估。

更新日期：2019-01-10

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