title: Modeling the active site of [NiFe] hydrogenases and the [NiFeu] subsite of the C-cluster of carbon monoxide dehydrogenases: low-spin iron(II) versus high-spin iron(II).
abstract: A series of four [S2Ni(μ-S)2FeCp*Cl] compounds with different tetradentate thiolate/thioether ligands bound to the Ni(II) ion is reported (Cp* = C5Me5). The {S2Ni(μ-S)2Fe} core of these compounds resembles structural features of the active site of [NiFe] hydrogenases. Detailed analyses of the electronic structures of these compounds by Mössbauer and electron paramagnetic resonance spectroscopy, magnetic measurements, and density functional theory calculations reveal the oxidation states Ni(II) low spin and Fe(II) high spin for the metal ions. The same electronic configurations have been suggested for the Cred1 state of the C-cluster [NiFeu] subsite in carbon monoxide dehydrogenases (CODH). The Ni-Fe distance of ∼3 Å excludes a metal-metal bond between nickel and iron, which is in agreement with the computational results. Electrochemical experiments show that iron is the redox active site in these complexes, performing a reversible one-electron oxidation. The four complexes are discussed with regard to their similarities and differences both to the [NiFe] hydrogenases and the C-cluster of Ni-containing CODH.
authors.affiliation: Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, D-45470 Mülheim an der Ruhr, Germany.
authors.forename: Katharina
authors.initials: K
authors.lastname: Weber
authors.forename: Özlen F
authors.initials: ÖF
authors.lastname: Erdem
authors.forename: Eckhard
authors.initials: E
authors.lastname: Bill
authors.forename: Thomas
authors.initials: T
authors.lastname: Weyhermüller
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Lubitz
mesh_terms: D000445:Aldehyde Oxidoreductases / Q000737:chemistry*; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D005296:Ferrous Compounds / Q000737:chemistry*; D006864:Hydrogenase / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D008958:Models, Molecular; D009097:Multienzyme Complexes / Q000737:chemistry*; D009532:Nickel / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013440:Sulfides / Q000737:chemistry
chemical_list: D005296:Ferrous Compounds; D009097:Multienzyme Complexes; D013438:Sulfhydryl Compounds; D013440:Sulfides; D009532:Nickel; D007501:Iron; C043296:nickel-iron hydrogenase; D006864:Hydrogenase; D000445:Aldehyde Oxidoreductases; C019823:carbon monoxide dehydrogenase