title: New members of a class of iron-thiolate-nitrosyl compounds: trinuclear iron-thiolate-nitrosyl complexes containing Fe(3)S(6) core.
abstract: The neutral trinuclear iron-thiolate-nitrosyl, [(ON)Fe(mu-S,S-C(6)H(4))](3) (1), and its oxidation product, [(ON)Fe(mu-S,S-C(6)H(4))](3)[PF(6)] (2), were synthesized and characterized by IR, X-ray diffraction, X-ray absorption, electron paramagnetic resonance (EPR), and magnetic measurement. The five-coordinated, square pyramidal geometry around each iron atom in complex 1 remains intact when complex 1 is oxidized to yield complex 2. Magnetic measurements and EPR results show that there is only one unpaired electron in complex 1 (S(total) = 1/2) and no unpaired electron (S(total) = 0) in 2. The detailed geometric comparisons between complexes 1 and 2 provide understanding of the role that the unpaired electron plays in the chemical bonding of this trinuclear complex. Significant shortening of the Fe-Fe, Fe-N, and Fe-S distances around Fe(1) is observed when complex 1 is oxidized to 2. This result implicates that the removal of the unpaired electron does induce the strengthening of the Fe-Fe, Fe-N, and Fe-S bonds in the Fe(1) fragment. A significant shift of the nuNO stretching frequency from 1751 cm(-1) (1) to 1821, 1857 cm(-1) (2) (KBr) also indicates the strengthening of the N-O bonds in complex 2. The EPR, X-ray absorption, magnetic measurements, and molecular orbital calculations lead to the conclusion that the unpaired electron in complex 1 is mainly allocated in the Fe(1) fragment and is best described as {Fe(1)NO}7, so that the unpaired electron is delocalized between Fe and NO via d-pi* orbital interaction; some contributions from [Fe(2)NO] and [Fe(3)NO] as well as the thiolates associated with Fe (1) are also realized. According to MO calculations, the spin density of complex 1 is predominantly located at the Fe atoms with 0.60, -0.15, and 0.25 at Fe(1), Fe(2), and Fe(3), respectively.
authors.affiliation: Department of Chemistry, National Tsing Hua University, Hsinchu 30013, Taiwan.
authors.forename: I-Jui
authors.initials: IJ
authors.lastname: Hsu
authors.forename: Chung-Hung
authors.initials: CH
authors.lastname: Hsieh
authors.forename: Shyue-Chu
authors.initials: SC
authors.lastname: Ke
authors.forename: Kuo-An
authors.initials: KA
authors.lastname: Chiang
authors.forename: Jenn-Min
authors.initials: JM
authors.lastname: Lee
authors.forename: Jin-Ming
authors.initials: JM
authors.lastname: Chen
authors.forename: Ling-Yun
authors.initials: LY
authors.lastname: Jang
authors.forename: Gene-Hsiang
authors.initials: GH
authors.lastname: Lee
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.forename: Wen-Feng
authors.initials: WF
authors.lastname: Liaw
mesh_terms: D001665:Binding Sites; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D005290:Ferric Compounds / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D009584:Nitrogen / Q000737:chemistry; D009589:Nitrogen Oxides / Q000138:chemical synthesis*; D010084:Oxidation-Reduction; D011522:Protons; D013052:Spectrometry, X-Ray Emission; D013055:Spectrophotometry, Infrared; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013440:Sulfides / Q000737:chemistry*; D013455:Sulfur / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D005290:Ferric Compounds; D007506:Iron-Sulfur Proteins; D009589:Nitrogen Oxides; D011522:Protons; D013438:Sulfhydryl Compounds; D013440:Sulfides; C073661:dinitrosyl iron complex; D013455:Sulfur; D007501:Iron; D009584:Nitrogen