title: Insight into the reactivity and electronic structure of dinuclear dinitrosyl iron complexes.
abstract: A combination of N/S/Fe K-edge X-ray absorption spectroscopy (XAS), X-ray diffraction data, and density functional theory (DFT) calculations provides an efficient way to unambiguously delineate the electronic structures and bonding characters of Fe-S, N-O, and Fe-N bonds among the direduced-form Roussin's red ester (RRE) [Fe2(μ-SPh)2(NO)4](2-)(1) with {Fe(NO)2}(10)-{Fe(NO)2}(10) core, the reduced-form RRE [Fe2(μ-SPh)2(NO)4](-)(3) with {Fe(NO)2}(9)-{Fe(NO)2}(10) core, and RRE [Fe2(μ-SPh)2(NO)4] (4) with {Fe(NO)2}(9)-{Fe(NO)2}(9) core. The major contributions of highest occupied molecular orbital (HOMO) 113α/β in complex 1 is related to the antibonding character between Fe(d) and Fe(d), Fe(d), and S atoms, and bonding character between Fe(d) and NO(π*). The effective nuclear charge (Zeff) of Fe site can be increased by removing electrons from HOMO to shorten the distances of Fe···Fe and Fe-S from 1 to 3 to 4 or, in contrast, to increase the Fe-N bond lengths from 1 to 3 to 4. The higher IR νNO stretching frequencies (1761, 1720 cm(-1) (4), 1680, 1665 cm(-1) (3), and 1646, 1611, 1603 cm(-1) (1)) associated with the higher transition energy of N1s →σ*(NO) (412.6 eV (4), 412.3 eV (3), and 412.2 eV (1)) and the higher Zeff of Fe derived from the transition energy of Fe1s → Fe3d (7113.8 eV (4), 7113.5 eV (3), and 7113.3 eV (1)) indicate that the N-O bond distances of these complexes are in the order of 1 > 3 > 4. The N/S/Fe K-edge XAS spectra as well as DFT computations reveal the reduction of complex 4 yielding complex 3 occurs at Fe, S, and NO; in contrast, reduction mainly occurs at Fe site from complex 3 to complex 1.
authors.affiliation: Department of Chemistry, National Tsing Hua University , Hsinchu 30013, Taiwan.
authors.forename: Feng-Chun
authors.initials: FC
authors.lastname: Lo
authors.forename: Ya-Wen
authors.initials: YW
authors.lastname: Li
authors.forename: I-Jui
authors.initials: IJ
authors.lastname: Hsu
authors.forename: Chien-Hong
authors.initials: CH
authors.lastname: Chen
authors.forename: Wen-Feng
authors.initials: WF
authors.lastname: Liaw
mesh_terms: D004583:Electrons; D007501:Iron / Q000737:chemistry*; D015394:Molecular Structure; D009569:Nitric Oxide / Q000737:chemistry; D009589:Nitrogen Oxides / Q000138:chemical synthesis / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D009589:Nitrogen Oxides; D009569:Nitric Oxide; C073661:dinitrosyl iron complex; D007501:Iron