Dramatic Influence of an Anionic Donor on the Oxygen‐Atom Transfer Reactivity of a MnV–Oxo Complex |
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| Authors: | Heather M Neu Dr Matthew G Quesne Tzuhsiung Yang Dr Katharine A Prokop‐Prigge Prof Kyle M Lancaster James Donohoe Prof Serena DeBeer Dr Sam P de?Visser Prof David P Goldberg |
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| Institution: | 1. Department of Chemistry, The Johns Hopkins University, Baltimore, MD (USA);2. Manchester Institute of Biotechnology and School of Chemical Engineering and Analytical Science, The University of Manchester, 131 Princess Street, Manchester (UK);3. Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York (USA);4. Max‐Planck Institute for Chemical Energy Conversion, Stiftstrasse, Mülheim an der Ruhr (Germany) |
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| Abstract: | Addition of an anionic donor to an MnV(O) porphyrinoid complex causes a dramatic increase in 2‐electron oxygen‐atom‐transfer (OAT) chemistry. The 6‐coordinate MnV(O)(TBP8Cz)(CN)]? was generated from addition of Bu4N+CN? to the 5‐coordinate MnV(O) precursor. The cyanide‐ligated complex was characterized for the first time by Mn K‐edge X‐ray absorption spectroscopy (XAS) and gives Mn?O=1.53 Å, Mn?CN=2.21 Å. In combination with computational studies these distances were shown to correlate with a singlet ground state. Reaction of the CN? complex with thioethers results in OAT to give the corresponding sulfoxide and a 2e?‐reduced MnIII(CN)? complex. Kinetic measurements reveal a dramatic rate enhancement for OAT of approximately 24 000‐fold versus the same reaction for the parent 5‐coordinate complex. An Eyring analysis gives ΔH≠=14 kcal mol?1, ΔS≠=?10 cal mol?1 K?1. Computational studies fully support the structures, spin states, and relative reactivity of the 5‐ and 6‐coordinate MnV(O) complexes. |
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| Keywords: | manganese oxygen‐atom‐transfer porphyrinoids spin state reactivity sulfoxidation |
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