Acid‐Triggered O−O Bond Heterolysis of a Nonheme FeIII(OOH) Species for the Stereospecific Hydroxylation of Strong C−H Bonds

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Abstract
A novel hydroperoxoiron(III) species [FeIII(OOH)(MeCN)(PyNMe3)]2+ (3) has been generated by reaction of its ferrous precursor [FeII(CF3SO3)2(PyNMe3)] (1) with hydrogen peroxide at low temperatures. This species has been characterized by several spectroscopic techniques and cryospray mass spectrometry. Similar to most of the previously described low‐spin hydroperoxoiron(III) compounds, 3 behaves as a sluggish oxidant and it is not kinetically competent for breaking weak C−H bonds. However, triflic acid addition to 3 causes its transformation into a much more reactive compound towards organic substrates that is capable of oxidizing unactivated C−H bonds with high stereospecificity. Stopped‐flow kinetic analyses and theoretical studies provide a rationale for the observed chemistry, a triflic‐acid‐assisted heterolytic cleavage of the O−O bond to form a putative strongly oxidizing oxoiron(V) species. This mechanism is reminiscent to that observed in heme systems, where protonation of the hydroperoxo intermediate leads to the formation of the high‐valent [(Porph.)FeIV(O)] (Compound I).
Funding Information
  • FP7 People: Marie-Curie Actions (2011-CIG-303522)
  • FP7 Ideas: European Research Council (ERC-2009-StG-239910)
  • Secretaría de Estado de Investigación, Desarrollo e Innovación (CTQ2012-37420-C02-01/BQU, CTQ2016-77989-P, CTQ2014-52525-P, CTQ2015-65707-C2-2-P, CSD2010-00065)
  • Generalitat de Catalunya (ICREA Academia Award)
  • Ministerio de Ciencia e Innovación (RYC-2011-08683)
  • National Science Foundation (CHE1665391)

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