Carbon Monoxide Induced Reductive Elimination of Disulfide in an N-Heterocyclic Carbene (NHC)/ Thiolate Dinitrosyl Iron Complex (DNIC)

doi:10.1021/ja403916v

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Title:	Carbon Monoxide Induced Reductive Elimination of Disulfide in an N-Heterocyclic Carbene (NHC)/ Thiolate Dinitrosyl Iron Complex (DNIC)
Authors:	Pulukkody, Randara;Kyran, Samuel J.;Bethel, Ryan D.;Hsieh, Chung-Hung;Hall, Michael B.;Darensbourg, Donald J.;Darensbourg, Marcetta Y.
Contributors:	淡江大學化學學系
Date:	2013-06-01
Issue Date:	2014-03-26 13:50:15 (UTC+8)
Publisher:	Washington, DC: American Chemical Society
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.
Relation:	Journal of the American Chemical Society 135(22), pp.8423-8430
DOI:	10.1021/ja403916v
Appears in Collections:	[Graduate Institute & Department of Chemistry] Journal Article

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