title: Precursors to [FeFe]-hydrogenase models: syntheses of Fe2(SR)2(CO)6 from CO-free iron sources.
abstract: This report describes routes to iron dithiolato carbonyls that do not require preformed iron carbonyls. The reaction of FeCl 2, Zn, and Q 2S 2C n H 2 n (Q (+) = Na (+), Et 3NH (+)) under an atmosphere of CO affords Fe 2(S 2C n H 2 n )(CO) 6 ( n = 2, 3) in yields >70%. The method was employed to prepare Fe 2(S 2C 2H 4)( (13)CO) 6. Treatment of these carbonylated mixtures with tertiary phosphines, instead of Zn, gave the ferrous species Fe 3(S 2C 3H 6) 3(CO) 4(PR 3) 2, for R = Et, Bu, and Ph. Like the related complex Fe 3(SPh) 6(CO) 6, these compounds consist of a linear arrangement of three conjoined face-shared octahedral centers. Omitting the phosphine but with an excess of dithiolate, we obtained the related mixed-valence triiron species [Fe 3(S 2C n H 2 n ) 4(CO) 4] (-). The highly reducing all-ferrous species [Fe 3(S 2C n H 2 n ) 4(CO) 4] (2-) is implicated as an intermediate in this transformation. Reactive forms of iron, prepared by the method of Rieke, also combined with dithiols under a CO atmosphere to give Fe 2(S 2C n H 2 n )(CO) 6 in modest yields under mild conditions. Studies on the order of addition indicate that ferrous thiolates are formed prior to the onset of carbonylation. Crystallographic characterization demonstrated that the complexes Fe 3(S 2C 3H 6) 3(CO) 4(PEt 3) 2 and PBnPh 3[Fe 3(S 2C 3H 6) 4(CO) 4] feature high-spin ferrous and low-spin ferric as the central metal, respectively.
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Phillip I
authors.initials: PI
authors.lastname: Volkers
authors.forename: Christine A
authors.initials: CA
authors.lastname: Boyke
authors.forename: Jinzhu
authors.initials: J
authors.lastname: Chen
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Rauchfuss
authors.forename: C Matthew
authors.initials: CM
authors.lastname: Whaley
authors.forename: Scott R
authors.initials: SR
authors.lastname: Wilson
authors.forename: Haijun
authors.initials: H
authors.lastname: Yao
mesh_terms: D001665:Binding Sites; D002244:Carbon / Q000737:chemistry*; D018360:Crystallography, X-Ray; D005290:Ferric Compounds / Q000737:chemistry*; D005296:Ferrous Compounds / Q000737:chemistry; D006864:Hydrogenase / Q000737:chemistry / Q000378:metabolism*; D007501:Iron / Q000737:chemistry*; D007506:Iron-Sulfur Proteins / Q000737:chemistry / Q000378:metabolism*; D010100:Oxygen / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; D005296:Ferrous Compounds; D007506:Iron-Sulfur Proteins; D002244:Carbon; D007501:Iron; C118830:iron hydrogenase; D006864:Hydrogenase; C029451:ferrous chloride; D010100:Oxygen