Halogen-Bonding-Assisted Iodosylbenzene Activation by a Homogenous Iron Catalyst

David P. de Sousa, Christina Wegeberg, Mads Sørensen Vad, Steen Mørup, Cathrine Frandsen, William A. Donald, Christine J. Mckenzie

Research output: Contribution to journalJournal articleResearchpeer-review


The iron(III) complex of hexadentate N,N,N′-tris(2-pyridylmethyl)ethylendiamine-N′-acetate (tpena) is a more effective homogenous catalyst for selective sulfoxidation and epoxidation with insoluble iodosylbenzene, [PhIO]n, compared with soluble methyl-morpholine-N-oxide (NMO). We propose that two molecules of [Fe(tpena)]2+ cooperate to solubilize PhIO, extracting two equivalents to form the halogen-bonded dimeric {[Fe(tpena)OIPh]2}4+. The closest intradimeric I⋅⋅⋅O distance, 2.56 Å, is nearly 1 Å less than the sum of the van de Waals radii of these atoms. A correlation of the rates of the reaction of {[Fe(tpena)OIPh]2}4+ with para-substituted thioanisoles indicate that this species is a direct metal-based oxidant rather than a derived ferryl or perferryl complex. A study of gas-phase reactions indicate that an ion at m/z=231.06100 originates from solution-state {[Fe(tpena)OIPh]2}4+ and is ascribed to [FeIII(tpenaO)]2+, derived from an intramolecular O atom insertion into an Fe–tpena donor bond. Proposed ion pairs, {[Fe(tpena)OIPh]Cl}+ and {[Fe(tpena)OIPh]ClO4}+, are more stable than native [Fe(tpena)OIPh]2+ ions, suggesting that halogen-bonding, as for the solution and solid states, operates also in the gas phase.
Original languageEnglish
JournalChemistry - A European Journal
Issue number11
Pages (from-to)3810–3820
Number of pages12
Publication statusPublished - 2016


  • Halogen Bonding
  • Iodosylbenzene
  • Iron
  • Epoxidation
  • Sulfoxidation
  • Gas Phase Chemistry
  • Chemistry (all)
  • Gas-phase chemistry
  • Halogen-bonding
  • Catalysts
  • Chemical bonds
  • Chemical reactions
  • Chlorine
  • Gases
  • Ions
  • Oxidation
  • Phase interfaces
  • Reaction rates
  • Gas phase chemistry
  • Gas-phase reactions
  • Halogen bonding
  • Hexadentate
  • Homogenous catalyst
  • Iron catalyst
  • Iron compounds


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