To develop the biomimetic chemistry of [FeFe]-H 2 ases, three new aminophosphine substituted diiron bis(monothiolate) carbonyls were synthesized by reactions of [Fe 2 (μ-SBn) 2 (CO) 6 ] (Bn=CH 2 C 6 H 5 ) with aryl-substituted aminodiphosphine (PNP) ligand (Ph 2 P) 2 NC 6 H 4 -4-C�CH under two different conditions. Treatment of them in the presence of Me 3 NO • 2H 2 O at room temperature gave PNP-chelated complex [Fe 2 (μ-SBn) 2 (CO) 4 {(k 2 -Ph 2 P) 2 N(C 6 H 4 -4-C�CH)}] (2) together with unexpected aminophosphine monosubstituted complex [Fe 2 (μ-SBn) 2 (CO) 5 {k 1 -Ph 2 PNH(NC 6 H 4 -4-C�CH)}](1), while treatment of them in reflux-ing toluene gave PNP-bridged complex [Fe 2 (μ-SBn) 2 (CO) 4 {(μ-Ph 2 P) 2 N(C 6 H 4 -4-C�CH)}] (3) as the major product. Complex 1 has two isomers (1-anti and 1-syn), and chelate complex 2 is the isomer of bridge complex 3. The more interesting finding is that 1-anti and 2 can be converted into 1-syn and 3, respectively. Complexes 1-3 were well characterized by elemental analysis, FT-IR, NMR spectroscopy, and X-ray diffraction analyses. In addition, electrochemical and electrocatalytic properties of 1-3 were studied by cyclic voltammetry (CV).
To further develop the active site models of [FeFe]-hydrogenases, a new series of diiron model complexes [{(μ-SCH 2 ) 2 CHCH 2 OC(O)C 6 H 4 I)}Fe 2 (CO) 6 ] (I is located at -para for 1, -meta for 2, and -ortho for 3) bearing dithiolato-bridgehead functionality were successfully prepared by treatments of bridghead-hydroxyl-containing parent complex [{(μ-SCH 2 ) 2 CHCH 2 OH)} Fe 2 (CO) 6 ] (A) and three different iodobenzoic acids (IC 6 H 4 CO 2 H) in the presence of 4-dimethylaminopyridine (DMAP) as catalyst and dicyclohexylcarbodiimide (DCC) as dehydrating reagent. All these new complexes 1-3 have been fully characterized through elemental analysis, FT-IR and NMR ( 1 H, 13 C) spectroscopies, and X-ray crystallography. Further electrochemical and electrocatalytic properties of complexes 1-3 are studied and compared in the absence and presence of acetic acid (HOAc) as a proton source by cyclic voltammetry (CV), indicating that they may be considered as the active biomimetic electrocatalysts for proton reduction to hydrogen (H 2 ).[a] S.-F. Bai, X.
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