Chatterjee, Sayanti and Harden, Ingolf and Bistoni, Giovanni and Castillo, Rebeca G and Chabbra, Sonia and van Gastel, Maurice and Schnegg, Alexander and Bill, Eckhard and Birrell, James A and Morandi, Bill and Neese, Frank and DeBeer, Serena (2022) A Combined Spectroscopic and Computational Study on the Mechanism of Iron-Catalyzed Aminofunctionalization of Olefins Using Hydroxylamine Derived N-O Reagent as the "Amino" Source and "Oxidant". Journal of the American Chemical Society, 144 (6). pp. 2637-2656. DOI https://doi.org/10.1021/jacs.1c11083
Chatterjee, Sayanti and Harden, Ingolf and Bistoni, Giovanni and Castillo, Rebeca G and Chabbra, Sonia and van Gastel, Maurice and Schnegg, Alexander and Bill, Eckhard and Birrell, James A and Morandi, Bill and Neese, Frank and DeBeer, Serena (2022) A Combined Spectroscopic and Computational Study on the Mechanism of Iron-Catalyzed Aminofunctionalization of Olefins Using Hydroxylamine Derived N-O Reagent as the "Amino" Source and "Oxidant". Journal of the American Chemical Society, 144 (6). pp. 2637-2656. DOI https://doi.org/10.1021/jacs.1c11083
Chatterjee, Sayanti and Harden, Ingolf and Bistoni, Giovanni and Castillo, Rebeca G and Chabbra, Sonia and van Gastel, Maurice and Schnegg, Alexander and Bill, Eckhard and Birrell, James A and Morandi, Bill and Neese, Frank and DeBeer, Serena (2022) A Combined Spectroscopic and Computational Study on the Mechanism of Iron-Catalyzed Aminofunctionalization of Olefins Using Hydroxylamine Derived N-O Reagent as the "Amino" Source and "Oxidant". Journal of the American Chemical Society, 144 (6). pp. 2637-2656. DOI https://doi.org/10.1021/jacs.1c11083
Abstract
Herein, we study the mechanism of iron-catalyzed direct synthesis of unprotected aminoethers from olefins by a hydroxyl amine derived reagent using a wide range of analytical and spectroscopic techniques (Mössbauer, Electron Paramagnetic Resonance, Ultra-Violet Visible Spectroscopy, X-ray Absorption, Nuclear Resonance Vibrational Spectroscopy, and resonance Raman) along with high-level quantum chemical calculations. The hydroxyl amine derived triflic acid salt acts as the "oxidant" as well as "amino" group donor. It activates the high-spin Fe(II) (<i>S</i><sub>t</sub> = 2) catalyst [Fe(acac)<sub>2</sub>(H<sub>2</sub>O)<sub>2</sub>] (<b>1</b>) to generate a high-spin (<i>S</i><sub>t</sub> = 5/2) intermediate (<b>Int I</b>), which decays to a second intermediate (<b>Int II</b>) with <i>S</i><sub>t</sub> = 2. The analysis of spectroscopic and computational data leads to the formulation of <b>Int I</b> as [Fe(III)(acac)<sub>2</sub>-<i>N</i>-acyloxy] (an alkyl-peroxo-Fe(III) analogue). Furthermore, <b>Int II</b> is formed by N-O bond homolysis. However, it does <i>not</i> generate a high-valent Fe(IV)(NH) species (a Fe(IV)(O) analogue), but instead a high-spin Fe(III) center which is strongly antiferromagnetically coupled (<i>J</i> = -524 cm<sup>-1</sup>) to an iminyl radical, [Fe(III)(acac)<sub>2</sub>-NH·], giving <i>S</i><sub>t</sub> = 2. Though Fe(NH) complexes as isoelectronic surrogates to Fe(O) functionalities are known, detection of a high-spin Fe(III)-<i>N</i>-acyloxy intermediate (<b>Int I</b>), which undergoes N-O bond cleavage to generate the active iron-nitrogen intermediate (<b>Int II</b>), is unprecedented. Relative to Fe(IV)(O) centers, <b>Int II</b> features a weak elongated Fe-N bond which, together with the unpaired electron density along the Fe-N bond vector, helps to rationalize its propensity for <i>N</i>-transfer reactions onto styrenyl olefins, resulting in the overall formation of aminoethers. This study thus demonstrates the potential of utilizing the iron-coordinated nitrogen-centered radicals as powerful reactive intermediates in catalysis.
Item Type: | Article |
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Divisions: | Faculty of Science and Health Faculty of Science and Health > Life Sciences, School of |
SWORD Depositor: | Unnamed user with email elements@essex.ac.uk |
Depositing User: | Unnamed user with email elements@essex.ac.uk |
Date Deposited: | 05 Sep 2022 16:01 |
Last Modified: | 07 Aug 2024 20:16 |
URI: | http://repository.essex.ac.uk/id/eprint/33386 |
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