The Fe2 (NO)2 Diamond Core: A Unique Structural Motif In Non-Heme Iron-NO Chemistry

Angew Chem Int Ed Engl. 2019 Dec 2;58(49):17695-17699. doi: 10.1002/anie.201911968. Epub 2019 Oct 23.

Abstract

Non-heme high-spin (hs) {FeNO}8 complexes have been proposed as important intermediates towards N2 O formation in flavodiiron NO reductases (FNORs). Many hs-{FeNO}8 complexes disproportionate by forming dinitrosyl iron complexes (DNICs), but the mechanism of this reaction is not understood. While investigating this process, we isolated a new type of non-heme iron nitrosyl complex that is stabilized by an unexpected spin-state change. Upon reduction of the hs-{FeNO}7 complex, [Fe(TPA)(NO)(OTf)](OTf) (1), the N-O stretching band vanishes, but no sign of DNIC or N2 O formation is observed. Instead, the dimer, [Fe2 (TPA)2 (NO)2 ](OTf)2 (2) could be isolated and structurally characterized. We propose that 2 is formed from dimerization of the hs-{FeNO}8 intermediate, followed by a spin state change of the iron centers to low-spin (ls), and speculate that 2 models intermediates in hs-{FeNO}8 complexes that precede the disproportionation reaction.

Keywords: dinitrosyl iron complexes (DNICs); model complexes; nitric oxide; non-heme iron complexes.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Dimerization
  • Iron / chemistry*
  • Ligands
  • Molecular Conformation
  • Nitric Oxide / chemistry*
  • Nitrogen Oxides / chemistry*
  • Oxidoreductases / metabolism
  • Structure-Activity Relationship
  • Thermodynamics

Substances

  • Ligands
  • Nitrogen Oxides
  • Nitric Oxide
  • dinitrosyl iron complex
  • Iron
  • Oxidoreductases