Synthesis,structures, and electrocatalytic properties of phosphine-monodentate, −chelate,and -bridge diiron 2,2-dimethylpropanedithiolate complexes related to [FeFe]-hydrogenases |
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Authors: | Meng-Yuan Hu Pei-Hua Zhao Jian-Rong Li Xiao-Li Gu Xing-Bin Jing Xu-Feng Liu |
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Institution: | 1. School of Materials Science and Engineering, North University of China, Taiyuan, 030051 P. R. China;2. School of Materials and Chemical Engineering, Ningbo University of Technology, Ningbo, 315211 P. R. China |
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Abstract: | To further extend diiron subsite models of FeFe]-hydrogenases, the various substitutions of all-carbonyl diiron complex Fe2(μ-Me2pdt)(CO)6 ( A , Me2pdt = (SCH2)2CMe2) with monophosphines or small bite-angle diphosphines are studied as follows. Firstly, the monodentate complexes Fe2(μ-Me2pdt)(CO)5{κ1-P(C6H4R-p)3} R = Me ( 1a ) and Cl ( 1b )] and Fe2(μ-Me2pdt)(CO)5{κ1-Ph2PX'} X' = NHPh ( 2a ) and CH2PPh2 ( 2b )] are readily afforded through the Me3NO-assisted reactions of A with monophosphines P(C6H4R-p)3 (R = Me, Cl) and diphosphines (Ph2P)2X (X = NPh, CH2 (dppm)) in MeCN at room temperature, respectively. Secondly, the chelate complexes Fe2(μ-Me2pdt)(CO)4(κ2-(Ph2P)2X) X = NPh ( 3a ) and NBun ( 3b )] can be efficiently prepared by the UV-irradiated reactions of A with small bite-angle diphosphines (Ph2P)2X (X = NPh, NBun) in toluene. Thirdly, the bridge complexes Fe2(μ-Me2pdt)(CO)4(μ-(Ph2P)2X) X = NPh ( 4a ) and CH2 ( 4b )] are well obtained from the refluxing solutions of A and diphosphines (Ph2P)2X (X = NPh, CH2) in xylene. Rarely, the diphosphine-bridge complex 4b may be produced in low yield via the UV-irradiated solutions of A and the dppm ligand in toluene emitting at 365 nm. Eight new complexes obtained above have been well characterized by using element analysis, FT-IR, NMR (1H, 31P) spectroscopies, and particularly for 1a , 1b , 2a , 3b , 4a , 4b by X-ray crystallography. Meanwhile, the electrochemical and electrocatalytic properties of three representative complexes 2a , 3a , and 4a with pendant N-phenyl groups are investigated and compared by using cyclic voltammetry (CV) in the absence and presence of trifluoroacetic acid (TFA) as a proton source, indicating that they are all found to be active for electrocatalytic proton reduction to hydrogen (H2). |
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Keywords: | diiron 2 2-dimethylpropanedithiolate complex electrocatalytic property facile synthesis phosphine ligands structural characterization |
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