title: Diferrous cyanides as models for the Fe-only hydrogenases.
abstract: The first systematic study of diferrous dicyano dithiolates is described. Oxidation of [Fe2(S2C2H4)(CN)2(CO)4](2-) in the presence of cyanide and tertiary phosphines and of Fe2(S2C2H4)(CO)4(PMe3)2 in the presence of cyanide affords a series of diferrous cyanide derivatives that bear a stoichiometric, structural, and electronic relationship to the H(ox)(air) state of the Fe-only hydrogenases. With PPh3 as the trapping ligand, we obtained an unsymmetrical isomer of Fe2(S2C2H4)(mu-CO)(CN)2(PPh3)2(CO)2, as confirmed crystallographically. This diferrous cyanide features the semibridging CO-ligand, with Fe-muC bond lengths of 2.15 and 1.85 A. Four isomers of Fe2(S2C2H4)(mu-CO)(CN)2(PMe3)2(CO)2 were observed, the initial product again being unsymmetrical but more stable isomers being symmetrical. DFT calculations confirm that the most stable isomers of Fe2(S2C2H4)(mu-CO)(CN)2(PMe3)2(CO)2 have cyanide trans to mu-CO. Oxidative decarbonylation also afforded the new tetracyanide [Fe2(S2C2H4)(mu-CO)(CN)4(CO)2]2-. Insights into the oxidative decarbonylation mechanism of these syntheses come from the spectroscopic characterization of the tetracarbonyl [Fe2(S2C2H4)(mu-CO)(CN)3(CO)3](-). This species reacts with PEt3 to produce the stable adduct [Fe2(S2C2H4)(mu-CO)(CN)3(CO)2(PEt3)](-).
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Christine A
authors.initials: CA
authors.lastname: Boyke
authors.forename: Jarl Ivar
authors.initials: JI
authors.lastname: van der Vlugt
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Rauchfuss
authors.forename: Scott R
authors.initials: SR
authors.lastname: Wilson
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Zampella
authors.forename: Luca
authors.initials: L
authors.lastname: De Gioia
mesh_terms: D003486:Cyanides / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry*; D006864:Hydrogenase / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry*; D008956:Models, Chemical; D011487:Protein Conformation
chemical_list: D003486:Cyanides; D005296:Ferrous Compounds; D007506:Iron-Sulfur Proteins; C118830:iron hydrogenase; D006864:Hydrogenase