Dinitrosyl iron complexes (DNICs) bearing O-bound nitrito ligand: reversible transformation between the six-coordinate {Fe(NO)2}9 [(1-MeIm)2(eta(2)-ONO)Fe(NO)2] (g = 2.013) and four-coordinate {Fe(NO)2}9 [(1-MeIm)(ONO)Fe(NO)2] (g = 2.03)

J Am Chem Soc. 2009 Mar 18;131(10):3426-7. doi: 10.1021/ja808743g.

Abstract

In contrast to the four-coordinate tetrahedral {Fe(NO)2}9 DNICs with an EPR g value of 2.03, the newly synthesized nonclassical six-coordinate {Fe(NO)2}9 DNIC [(1-MeIm)2(eta(2)-ONO)Fe(NO)2] (1-MeIm = 1-methylimidazole) (1) displays an EPR signal g = 2.013. The temperature-dependent reversible transformation occurs between the six-coordinate chelating nitrito {Fe(NO)2}9 DNIC 1 and the four-coordinate monodentate nitrito {Fe(NO)2}9 DNIC [(1-MeIm)(ONO)Fe(NO)2] (2-MeIm). The chelating nitrito of DNIC 1, triggered by PPh3, undergoes O-atom transfer to yield O=PPh3, accompanied by reductive elimination of NO and the generation of {Fe(NO)2}10 DNIC [(1-MeIm)(PPh3)Fe(NO)2] (3), in contrast to the inertness of the nitrite-containing {Fe(NO)2}9 DNIC [(HIm)(ONO)Fe(NO)2] (HIm = imidazole) (2-HIm) toward PPh3. The findings, EPR signals of g = 2.013 for complex 1 and g = 2.03 for complexes 2-MeIm/2-HIm, imply that characterization of DNICs may be possible via their distinctive EPR signal g = 2.03 for the tetrahedral DNICs and EPR signal g = 2.01 for the six-coordinate DNICs. This study also implicates that the six-coordinate nitrite-containing {Fe(NO)2}9 DNICs may act as a transient intermediate (or an active center) to trigger the transformation of nitrite into nitric oxide.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Crystallography, X-Ray
  • Electron Spin Resonance Spectroscopy
  • Iron / chemistry*
  • Ligands
  • Models, Molecular
  • Nitrogen Oxides / chemistry*

Substances

  • Ligands
  • Nitrogen Oxides
  • dinitrosyl iron complex
  • Iron