Carbon monoxide induced reductive elimination of disulfide in an N-heterocyclic carbene (NHC)/ thiolate dinitrosyl iron complex (DNIC)

Randara Pulukkody, Samuel J. Kyran, Ryan D. Bethel, Chung Hung Hsieh, Michael B. Hall, Donald J. Darensbourg, Marcetta Y. Darensbourg*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

Dinitrosyliron complexes (DNICs) are organometallic-like compounds of biological significance in that they appear in vivo as products of NO degradation of iron-sulfur clusters; synthetic analogues have potential as NO storage and releasing agents. Their reactivity is expected to depend on ancillary ligands and the redox level of the distinctive Fe(NO)2 unit: paramagnetic {Fe(NO)2}9, diamagnetic dimerized forms of {Fe(NO)2}9 and diamagnetic {Fe(NO)2} 10 DNICs (Enemark-Feltham notation). The typical biological ligands cysteine and glutathione themselves are subject to thiolate-disulfide redox processes, which when coupled to DNICs may lead to intricate redox processes involving iron, NO, and RS-/RS•. Making use of an N-heterocyclic carbene-stabilized DNIC, (NHC)(RS)Fe(NO)2, we have explored the DNIC-promoted RS-/RS• oxidation in the presence of added CO wherein oxidized {Fe(NO)2}9 is reduced to {Fe(NO) 2}10 through carbon monoxide (CO)/RS• ligand substitution. Kinetic studies indicate a bimolecular process, rate = k [Fe(NO)2]1[CO]1, and activation parameters derived from kobs dependence on temperature similarly indicate an associative mechanism. This mechanism is further defined by density functional theory computations. Computational results indicate a unique role for the delocalized frontier molecular orbitals of the Fe(NO)2 unit, permitting ligand exchange of RS• and CO through an initial side-on approach of CO to the electron-rich N-Fe-N site, ultimately resulting in a 5-coordinate, 19-electron intermediate with elongated Fe-SR bond and with the NO ligands accommodating the excess charge.

Original languageEnglish (US)
Pages (from-to)8423-8430
Number of pages8
JournalJournal of the American Chemical Society
Volume135
Issue number22
DOIs
StatePublished - Jun 5 2013

ASJC Scopus subject areas

  • General Chemistry
  • Biochemistry
  • Catalysis
  • Colloid and Surface Chemistry

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