Engineering the Oxidative Potency of Non-Heme Iron(IV) Oxo Complexes in Water for C-H Oxidation by a cis Donor and Variation of the Second Coordination Sphere

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Abstract

A series of iron(IV) oxo complexes, which differ in the donor (CH2py or CH2COO-) cis to the oxo group, three with hemilabile pendant donor/second coordination sphere base/acid arms (pyH/py or ROH), have been prepared in water at pH 2 and 7. The νFe=O values of 832 ± 2 cm-1 indicate similar FeIV=O bond strengths; however, different reactivities toward C-H substrates in water are observed. HAT occurs at rates that differ by 1 order of magnitude with nonclassical KIEs (kH/kD = 30-66) consistent with hydrogen atom tunneling. Higher KIEs correlate with faster reaction rates as well as a greater thermodynamic stability of the iron(III) resting states. A doubling in rate from pH 7 to pH 2 for substrate C-H oxidation by the most potent complex, that with a cis-carboxylate donor, [FeIVO(Htpena)]2+, is observed. Supramolecular assistance by the first and second coordination spheres in activating the substrate is proposed. The lifetime of this complex in the absence of a C-H substrate is the shortest (at pH 2, 3 h vs up to 1.3 days for the most stable complex), implying that slow water oxidation is a competing background reaction. The iron(IV)=O complex bearing an alcohol moiety in the second coordination sphere displays significantly shorter lifetimes due to a competing selective intramolecular oxidation of the ligand.

Detaljer

Författare
  • Christina Wegeberg
  • Mathias L. Skavenborg
  • Andrea Liberato
  • James N. McPherson
  • Wesley R. Browne
  • Erik D. Hedegård
  • Christine J. McKenzie
Enheter & grupper
Externa organisationer
  • University of Southern Denmark
  • University of New South Wales
  • University of Cádiz
  • University of Groningen
Forskningsområden

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Oorganisk kemi
Originalspråkengelska
Sidor (från-till)1975–1984
TidskriftInorganic Chemistry
Volym60
Utgåva nummer3
StatusPublished - 2021
PublikationskategoriForskning
Peer review utfördJa