[Fe2(SR)2(μ-CO)(CNMe)6]2+ and Analogues:  A New Class of Diiron Dithiolates as Structural Models for the HoxAir State of the Fe-Only Hydrogenase

Boyke, Christine A.; Rauchfuss, Thomas B.; Wilson, Scott R.; Rohmer, Marie‐Madeleine; Bénard, Marc

doi:10.1021/ja049050k

Cited by 91 publications

(90 citation statements)

References 63 publications

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“…Recently, Pickett and co-workers have reported their assembly by linking of an [Fe 4 S 4 ] cluster to a diiron unit, which offers the prospect of understanding the catalytic mechanisms of [Fe]H 2 ases. [26] Rauchfuss et al have developed syntheses of mixed-ligand diferrous dithiolate complexes by the oxidative decarbonylation of diiron dithiolates, [27,28] and Darensbourg and co-workers have described the electrocatalytic production of H 2 by PDT-bridged diiron derivatives [(µ-PDT)Fe 2 (CO) 4 (PR 3 ) 2 ] in the presence of the weak acid HOAc. [29,30] Rauchfuss et al have demonstrated that the mixed-ligand substituted diiron system [(µ-PDT)Fe 2 (CO) 4 PMe 3 (CN)] -is an electrocatalyst for H 2 production with the strong acid p-toluenesulfonic acid (HOTs).…”

Section: Introductionmentioning

confidence: 99%

A Binuclear Isocyanide Azadithiolatoiron Complex Relevant to the Active Site of Fe‐Only Hydrogenases: Synthesis, Structure and Electrochemical Properties

et al. 2006

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An aromatic isocyanide-substituted diiron complex 5 has been synthesized as a mimic for the active site of Fe-only hydrogenases. Its structure has been fully characterized by X-ray crystallography. The 4-iodophenylisocyanide ligands in 5 are in the basal positions and are nearly parallel to each other, with π-π stacking interactions. Four isomeric geometries of complex 5 have been optimized by DFT calculations, and the electrochemical properties of 5 have been investi-

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Section: Introductionmentioning

confidence: 99%

A Binuclear Isocyanide Azadithiolatoiron Complex Relevant to the Active Site of Fe‐Only Hydrogenases: Synthesis, Structure and Electrochemical Properties

et al. 2006

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“…Particular emphasis has been placed on variations of L, especially tertiary phosphines [1][2][3], but also isocyanides [4,5], N-heterocyclic carbenes [6][7][8][9], and cyanide [10][11][12][13]. While much effort has focused on functionalizing the dithiolate ligand [14][15][16][17][18][19][20], relatively little work has examined the possibility of replacing the thiolates with other bridging groups [21].…”

Section: Fe Complexes; Metal Hydride; Hydrogenase; Electrocatalysismentioning

confidence: 99%

“…A stable monocyanide derivative was prepared via the reaction of 1 with KN(SiMe 3 ) 2 [11]. Similarly, treatment of 1 with Me 3 NO gave the MeCN complex Fe 2 (BC)(CO) 5 (MeCN) (ν CO = 2043CO = , 2030CO = , 1976CO = , 1964CO = , 1913 cm −1 ) [29], which was found to react with Et 4 NCN to afford Et 4 N[Fe 2 (BC) (CO) 5 (CN)], as indicated by IR spectroscopy and ESI-MS. 2 It was of interest to determine if the diiron azo system 2 could be protonated at the Fe-Fe bond and, if so, would the resulting hydride electrocatalyze proton reduction, analogous to the reactivity observed in Fe 2 (SR) 2 systems [29][30][31]. Indeed, we found that HCl effected protonation at the Fe-Fe bond of 2, thereby forming a rare example of a (μ-hydrido)diiron azo system, [2H] + .…”

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confidence: 99%

Extending the motif of the [FeFe]-hydrogenase active site models: Protonation of Fe2(NR)2(CO)6−L species

Volkers

Rauchfuss

2007

Journal of Inorganic Biochemistry

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Studies on diiron dithiolato complexes have proven fruitful for modeling the active site of the [FeFe]hydrogenases. Here we present a departure from the classical Fe 2 S 2 motif by examining the viability of Fe 2 N 2 butterfly compounds as functional models for the diiron active site of [FeFe]-hydrogenases. Derivatization of Fe 2 (BC)(CO) 6 (1, BC = benzo-[c]-cinnoline) with PMe 3 affords Fe 2 (BC) (CO) 4 (PMe 3 ) 2 , which subsequently undergoes protonation at the Fe-Fe bond. The hydride [(μ-H) Fe 2 (BC)(CO) 4 (PMe 3 ) 2 ]PF 6 was characterized crystallographically as the C 2v isomer. It represents a rare example of a hydrido diiron complex that exists as observable isomers, depending on the location of the phosphine ligands -diapical and apical-basal. This hydride catalyzes the electrochemical reduction of protons. Keywords Fe complexes; Metal hydride; Hydrogenase; ElectrocatalysisIn recent years, many compounds of the type Fe 2 (S-R) 2 (CO) 4 L 2 have been prepared and examined as structural and functional models for the active site of [FeFe]-hydrogenases. Particular emphasis has been placed on variations of L, especially tertiary phosphines [1][2][3], but also isocyanides [4,5], N-heterocyclic carbenes [6][7][8][9], and cyanide [10][11][12][13]. While much effort has focused on functionalizing the dithiolate ligand [14][15][16][17][18][19][20], relatively little work has examined the possibility of replacing the thiolates with other bridging groups [21]. Best and coworkers demonstrated that the corresponding phosphides Fe 2 (PR 2 ) 2 (CO) 6 and [Fe 2 (PR 2 ) 2 (CO) 6 H] − are effective catalysts for hydrogen evolution [22].Incentives for broadening the range of bridging ligands include changing the steric profile of the catalysts, altering the susceptibility of the bridge toward electrophilic attack (important since these catalysts function in acidic media), incorporating functionality, and manipulating the electronic character (basicity, E 1/2 ) of the metals. Naturally, a fundamental motivation for investigating new bridging ligands is to elucidate the elementary design rules that will lead to greater mechanistic insight and, ultimately, a deeper understanding of hydrogenogenesis.Approximately 15 nitrogenous bridges are known to link pairs of iron centers, giving complexes of the general formula Fe 2 (NR 1,2 ) 2 (CO) 6 (Scheme 1). Many of the complexes were first reported in the 1960s and 1970s in an era where the interactions of nitrene-forming reagents and metal carbonyls were first systematized. We selected one representative of this series, Fe 2 (BC)(CO) 6 [23][24][25][26] properties would test most demandingly the scope of the hydrogenase behavior of the Fe 2 (μ-X) 2 L n systems (L = CO, donor ligands). This report summarizes these results, which indeed demonstrate the prospect that many nitrogenous bridging ligands could be applied to the modeling of hydrogenases.Compound 1 was prepared using the original method, using Fe 3 (CO) 12 in place of Fe(CO) 5 [27]. As for other donor ligands [26,...

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“…Anal. Calcd for C 28 Concentrated HCl (4.0 mL, 12 M) was added dropwise to the solution of 3 (0.5 g, 0.83 mmol) in CH 2 Cl 2 /EtOH (2 mL/15 mL). The solution turned deep red after stirred for 10 min, to which was added a few drops of saturated aqueous NH 4 PF 6 solution.…”

Section: Synthesis Of [{(L-sch 2 ) 2 N(4-no 2 C 6 H 4 )}-Fe 2 (Co) 5 mentioning

confidence: 99%

“…The rare reports on the preparation, protonation and electrochemistry of the adt-bridged diiron complexes are confined to the all-carbonyl complexes [15][16][17][18][19][20][21][22][23]. Although CO-displacement reactions of [(l-pdt)Fe 2 (CO) 6 ] by strong donor ligands, such as CN À [4,11,24,25], PR 3 [3,5,26], CNR [27,28] and N,N 0 -disubstituted-2-imidazolylidene [29,30] have been extensively studied, to the best of our knowledge, there were very few reports on the ligand modified diiron azadithiolate complexes [31][32][33].…”

Section: Introductionmentioning

confidence: 99%

Preparation, structures and electrochemical property of phosphine substituted diiron azadithiolates relevant to the active site of Fe-only hydrogenases

Dong

Wang

Liu

et al. 2007

Journal of Inorganic Biochemistry

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[Fe₂(SR)₂(μ-CO)(CNMe)₆]²⁺ and Analogues: A New Class of Diiron Dithiolates as Structural Models for the H_o_x^A^ir State of the Fe-Only Hydrogenase

Cited by 91 publications

References 63 publications

A Binuclear Isocyanide Azadithiolatoiron Complex Relevant to the Active Site of Fe‐Only Hydrogenases: Synthesis, Structure and Electrochemical Properties

A Binuclear Isocyanide Azadithiolatoiron Complex Relevant to the Active Site of Fe‐Only Hydrogenases: Synthesis, Structure and Electrochemical Properties

Extending the motif of the [FeFe]-hydrogenase active site models: Protonation of Fe2(NR)2(CO)6−L species

Preparation, structures and electrochemical property of phosphine substituted diiron azadithiolates relevant to the active site of Fe-only hydrogenases

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