An approach to water-soluble hydrogenase active site models: Synthesis and electrochemistry of diiron dithiolate complexes with 3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane ligand(s)

[FeFe]-Hydrogenase active site models with relatively low reduction potentials: Diiron dithiolate complexes containing rigid bridges

“…12.018 to molecular hydrogen at ca. À1.0 to À1.2 V vs. NHE in the presence of strong acids [14][15][16]29,[33][34][35], which contrasts sharply with the incredibly low potential and the mild condition (À0.4 V vs. NHE at neutral pH) for the enzymatic proton reduction catalysed by the native [FeFe]Hases [36].…”

“…A large number of diiron dithiolate complexes, either with the alkylene bridges, e.g. pdt (propane-1,3-dithiolato) [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23], edt (ethane-1,2-dithiolato) [24][25][26], and an adt (2-azopropane-1, 3-dithiolato) bridge [27][28][29][30][31][32], were prepared and characterized. Some diiron dithiolate complexes were reported catalytically active for electrochemical proton reduction 0162-0134/$ -see front matter Ó 2008 Elsevier Inc. All rights reserved.…”

“…Displacement of one or two CO ligands of diiron dithiolate complexes by other ligands makes the iron centers more protophilic and the reduction potentials of the complexes much more negative (À1.9 to À2.7 V vs. Fc/Fc + ) [7,[13][14][15][16][17][18][19][20][33][34][35]. Although much effort has focused on adjusting the redox potential, the protophilicity, and the water solubility of diiron dithiolate model complexes by CO-displacement with various ligands, such as cyanide [6][7][8]28], tertiary phosphines and phosphites [9][10][11][12][13][14][15], N-heterocyclic carbenes [16][17][18][19][20], isocyanides [21,22], and 1,10-phenanthroline [23], little work has been reported on tuning the reactivity and the electrochemical property of the diiron center by varying the S-to-S linker [38][39][40][41][42][43]. It was reported that the bdtbridged (bdt = benzene-1,2-dithiolato) diiron dithiolate complex (l-bdt)Fe 2 (CO) 6 showed the first reduction event at À1.44 V vs. Fc/Fc + with a 220 mV positive shift in comparison to the pdt-bridged complex (l-pdt)Fe 2 (CO) 6 [35], indicating that the reduction potential of the iron center in the diiron dithiolate complexes can be effectively tuned less negative b...…”

A Binuclear Iron–Thiolate Catalyst for Electrochemical Hydrogen Production in Aqueous Micellar Solution

“…Only few compounds that incorporate hydrophilic ligands have been prepared. [34][35][36] Addition of water-miscible organic solvent was often required to achieve concentrations relevant to catalysis. Other strategies to address the water-solubility issue have included preparation of chemically modified electrodes, [37][38][39] incorporation into cyclodextrin, [40,41] and dispersion in aqueous micellar solutions.…”

Functionalized Sugars as Ligands towards Water‐Soluble [Fe‐only] Hydrogenase Models

“…The use of sugar residues should strongly increase the hydrophilicity and should allow hydrogen gas formation in aqueous systems, which is sparsely known in the literature. [5] Water would provide the advantage to serve as both the solvent and the proton source, as is the case under physiological conditions. The advantages for the use of sugars, therefore, are self evident.…”