title: Dinuclear iron(II)-cyanocarbonyl complexes linked by two/three bridging ethylthiolates: relevance to the active site of [Fe] hydrogenases.
abstract: Dinuclear iron(II)-cyanocarbonyl complex [PPN](2)[Fe(CN)(2)(CO)(2)(mu-SEt)](2) (1) was prepared by the reaction of [PPN][FeBr(CN)(2)(CO)(3)] and [Na][SEt] in THF at ambient temperature. Reaction of complex 1 with [PPN][SEt] produced the triply thiolate-bridged dinuclear Fe(II) complex [PPN][(CN)(CO)(2)Fe(mu-SEt)(3)Fe(CO)(2)(CN)] (2) with the torsion angle of two CN(-) groups (C(5)N(2) and C(3)N(1)) being 126.9 degrees. The extrusion of two sigma-donor CN(-) ligands from Fe(II)Fe(II) centers of complex 1 as a result of the reaction of complex 1 and [PPN][SEt] reflects the electron-rich character of the dinuclear iron(II) when ligated by the third bridging ethylthiolate. The Fe-S distances (2.338(2) and 2.320(3) A for complexes 1 and 2, respectively) do not change significantly, but the Fe(II)-Fe(II) distance contracts from 3.505 A in complex 1 to 3.073 A in complex 2. The considerably longer Fe(II)-Fe(II) distance of 3.073 A in complex 2, compared to the reported Fe-Fe distances of 2.6/2.62 A in DdHase and CpHase, was attributed to the presence of the third bridging ethylthiolate, instead of pi-accepting CO-bridged ligand as observed in [Fe] hydrogenases. Additionally, in a compound of unusual composition ([Na.(5)/(2)H(2)O][(CN)(CO)(2)Fe(mu-SEt)(3)Fe(CO)(2)(CN)])(n)((1)/(2)O(Et)(2))(n) (3), the Na(+) cations and H(2)O molecules combining with dinuclear [(CN)(CO)(2)Fe(mu-SEt)(3)Fe(CO)(2)(CN)](-) anions create a polymeric framework wherein two CN(-) ligands are coordinated via CN(-)-Na(+)/CN(-)-(Na(+))(2) linkages, respectively.
authors.affiliation: Department of Chemistry, Naional Tsing Hua University, Hsinchu 30043, Taiwan. wflaiw@mx.nthu.edu.tw
authors.forename: Wen-Feng
authors.initials: WF
authors.lastname: Liaw
authors.forename: Wen-Ting
authors.initials: WT
authors.lastname: Tsai
authors.forename: Hung-Bin
authors.initials: HB
authors.lastname: Gau
authors.forename: Chien-Ming
authors.initials: CM
authors.lastname: Lee
authors.forename: Shin-Yuan
authors.initials: SY
authors.lastname: Chou
authors.forename: Wen-Yuan
authors.initials: WY
authors.lastname: Chen
authors.forename: Gene-Hsiang
authors.initials: GH
authors.lastname: Lee
mesh_terms: D001665:Binding Sites; D002248:Carbon Monoxide / Q000737:chemistry; D018360:Crystallography, X-Ray; D003486:Cyanides / Q000737:chemistry; D005296:Ferrous Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D006864:Hydrogenase / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation
chemical_list: D003486:Cyanides; D005296:Ferrous Compounds; D007506:Iron-Sulfur Proteins; D008024:Ligands; D002248:Carbon Monoxide; D007501:Iron; C118830:iron hydrogenase; D006864:Hydrogenase