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Dramatic Influence of an Anionic Donor on the Oxygen‐Atom Transfer Reactivity of a Mn V –Oxo Complex
Author(s) -
Neu Heather M.,
Quesne Matthew G.,
Yang Tzuhsiung,
ProkopPrigge Katharine A.,
Lancaster Kyle M.,
Donohoe James,
DeBeer Serena,
de Visser Sam P.,
Goldberg David P.
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201404349
Subject(s) - reactivity (psychology) , chemistry , x ray absorption spectroscopy , singlet state , crystallography , oxygen atom , cyanide , oxidation state , atom (system on chip) , sulfoxide , electron transfer , reaction coordinate , absorption (acoustics) , absorption spectroscopy , photochemistry , excited state , molecule , inorganic chemistry , catalysis , materials science , organic chemistry , alternative medicine , pathology , computer science , composite material , embedded system , quantum mechanics , nuclear physics , medicine , physics
Addition of an anionic donor to an Mn V (O) porphyrinoid complex causes a dramatic increase in 2‐electron oxygen‐atom‐transfer (OAT) chemistry. The 6‐coordinate [Mn V (O)(TBP 8 Cz)(CN)] − was generated from addition of Bu 4 N + CN − to the 5‐coordinate Mn V (O) precursor. The cyanide‐ligated complex was characterized for the first time by Mn K‐edge X‐ray absorption spectroscopy (XAS) and gives MnO=1.53 Å, MnCN=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 Mn III (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 Δ H ≠ =14 kcal mol −1 , Δ S ≠ =−10 cal mol −1 K −1 . Computational studies fully support the structures, spin states, and relative reactivity of the 5‐ and 6‐coordinate Mn V (O) complexes.