title: Spin-state-dependent oxygen sensitivity of iron dithiolates: sulfur oxygenation or disulfide formation.
abstract: The oxygen sensitivity of two related iron(III) dithiolate complexes of the ligand [4,7-bis-(2'-methyl-2'-mercatopropyl)-1-thia-4,7-diazacyclononane], (bmmp-TASN)FeCN (1) and (bmmp-TASN)FeCl (2), has been examined. Oxygen exposure of the low-spin complex 1 yields the disulfonate complex (bmmp-O6-TASN)FeCN (3) as an olive-green solid with characteristic peaks in the IR spectrum at 1262, 1221, 1111, 1021, 947, 800, and 477 cm(-1). The corresponding nickel dithiolate, (bmmp-TASN)Ni (4), yields the related disulfonato derivative, (bmmp-O6-TASN)Ni (5) upon addition of H2O2 (IR bands at 1258, 1143, 1106, 1012, 800, and 694 cm(-1). Oxygen exposure of the high-spin complex 2 results in disulfide formation and decomplexation of the metal with subsequent iron-oxo cluster formation. Complexes 1 and 2 were examined using density functional theory calculations. A natural bond order/natural localized molecular orbital covalency analysis reveals that the low-spin complex 1 contains Fe-Sthiolate bonds with calculated covalencies of 75 and 86%, while the high-spin complex 2 contains Fe-Sthiolate bonds with calculated covalencies of 11 and 40%. The results indicate the degree of covalency of the Fe-S bonds plays a major role in determining the reaction pathway associated with oxygen exposure of iron thiolates. The X-ray structures of 1, 4, and 5 are reported.
authors.affiliation: Department of Chemistry, University of Louisville, Louisville, KY 40292, USA.
authors.forename: Martin G
authors.initials: MG
authors.lastname: O'Toole
authors.forename: Majda
authors.initials: M
authors.lastname: Kreso
authors.forename: Pawel M
authors.initials: PM
authors.lastname: Kozlowski
authors.forename: Mark S
authors.initials: MS
authors.lastname: Mashuta
authors.forename: Craig A
authors.initials: CA
authors.lastname: Grapperhaus
mesh_terms: D000465:Algorithms; D001665:Binding Sites; D018360:Crystallography, X-Ray; D004220:Disulfides / Q000737:chemistry*; D006836:Hydro-Lyases / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D008956:Models, Chemical; D009532:Nickel / Q000737:chemistry; D009942:Organometallic Compounds / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry*; D011789:Quantum Theory; D013055:Spectrophotometry, Infrared; D019097:Spin Trapping; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013455:Sulfur / Q000737:chemistry*
chemical_list: D004220:Disulfides; D009942:Organometallic Compounds; D013438:Sulfhydryl Compounds; D013455:Sulfur; D009532:Nickel; D007501:Iron; D006836:Hydro-Lyases; C048831:nitrile hydratase; D010100:Oxygen