title: [Fe2(SR)2(mu-CO)(CNMe)6]2+ and analogues: a new class of diiron dithiolates as structural models for the H(ox)Air state of the fe-only hydrogenase.
abstract: Low-temperature oxidation of Fe(2)(S(2)C(n)H(2n)(CNMe)(6-x)(CO)x (n = 2, 3; x = 2, 3) affords a family of mixed carbonyl-isocyanides of the type [Fe(2)(S(2)C(n)H(2n)(CO)x(CNMe)(7-x)](2+). The degree of substitution is controlled by the RNC/Fe ratio, as well as the degree of initial substitution at iron, with tricarbonyl derivatives favoring more highly carbonylated products. The structures of the monocarbonyl derivatives [Fe(2)(S(2)C(n)H(2n))(mu-CO)(CNMe)(6)](PF(6))(2) (n = 2,3) established crystallographically and spectroscopically, are quite similar, with Fe---Fe distances of ca. 2.5 A, although the mu-CO is unsymmetrical in the propanedithiolate derivative. Isomeric forms of [Fe(2)(S(2)C(3)H(6))(CO)(CNMe)(6)](PF(6))(2) were characterized where the CO is bridging or terminal, the greatest structural difference being the 0.1 A elongation of the Fe---Fe distance when MeNC (vs CO) is bridging. In the dicarbonyl species, [Fe(2)(S(2)C(2)H(4))(mu-CO)(CO)(CNMe)(5)](PF(6))(2), the terminal CO ligand is situated at one of the basal sites, not trans to the Fe---Fe vector. Oxidation of Fe(2)(S(2)C(2)H(4))(CNMe)(3)(CO)(3) under 1 atm CO gives the deep pink tricarbonyl [Fe(2)(S(2)C(2)H(4))(CO)(3)(CNMe)(4)](PF(6))(2). DFT calculations show that a bridging CO or MeNC establishes a 3-center, 2-electron bond within the two Fe(II) centers, which would otherwise be nonbonding.
authors.affiliation: Department of Chemistry, University of Illinois, Urbana, Illinois 61801, USA.
authors.forename: Christine A
authors.initials: CA
authors.lastname: Boyke
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Rauchfuss
authors.forename: Scott R
authors.initials: SR
authors.lastname: Wilson
authors.forename: Marie-Madeleine
authors.initials: MM
authors.lastname: Rohmer
authors.forename: Marc
authors.initials: M
authors.lastname: Bénard
mesh_terms: D018360:Crystallography, X-Ray; D003486:Cyanides / Q000138:chemical synthesis / Q000737:chemistry*; D005296:Ferrous Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry* / Q000378:metabolism; D006864:Hydrogenase / Q000737:chemistry* / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D015394:Molecular Structure; D010084:Oxidation-Reduction; D013055:Spectrophotometry, Infrared; D013438:Sulfhydryl Compounds / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D003486:Cyanides; D005296:Ferrous Compounds; D007506:Iron-Sulfur Proteins; D013438:Sulfhydryl Compounds; D006859:Hydrogen; C118830:iron hydrogenase; D006864:Hydrogenase