New Tetracobalt Cluster Compounds for Electrocatalytic Proton Reduction: Syntheses, Structures, and Reactivity

Abstract

Reaction of Co2(CO)8 and 1,3-propanedithiol in a 1:1 molar ratio in toluene affords a novel tetracobalt complex, [(μ2-pdt)2(μ3-S)Co4(CO)6] (pdt = -SCH2CH2CH2S-, 1), which possesses some of the structural features of the active site of [FeFe]-hydrogenase. Carbonyl displacement reaction of complex 1 in the presence of mono- or diphosphine ligands leads to the formation of [(μ2-pdt)2(μ3-S)Co4(CO)5(PCy3)] (2) and [(μ2-pdt)2(μ3-S)Co4(CO)4(L)] [L = Ph2PCH=CHPPh2, 3; Ph2PCH2N(Ph)CH2PPh2, 4; Ph2PCH2N(iPr)CH2PPh2, 5]. Complexes 1-5 have been fully characterized by spectroscopy and single-crystal X-ray diffraction studies. Cyclic voltammetry has revealed that complexes 1-5 show a reversible first reduction wave and are active for electrocatalytic proton reduction in the presence of CF3COOH. Protonation reactions have been monitored by (31)P and (1)H NMR and infrared spectroscopies, which revealed the formation of different protonated species. The mono-reduced species of 1-5 have been spectroscopically characterized by EPR and spectro-electro-infrared techniques.

Photo- and Thermal Isomerization of (TP)Fe(CO)Cl2 [TP = Bis(2-diphenylphosphinophenyl)phenylphosphine]

“…In the context of our studies on photochemical proton reduction, , we discovered that the iron complex (TP)­Fe­(CO)­Cl 2 (TP = bis­[2-(diphenylphosphino)­phenyl]­phenylphosphine) undergoes light-induced isomerization from the mer - to fac -coordination mode of the tridentate TP ligand, followed by a slow thermal reisomerization. Here, we report the synthesis and structural characterization of the title complex, photoisomerization, and kinetic studies of the thermal-isomerization reactions.…”