Amine‐containing tertiary phosphine‐substituted diiron ethanedithioate (edt) complexes Fe2(μ‐edt)(CO)6‐nLn (n= 1, 2): Synthesis, protonation, and electrochemical properties

• Published in: Applied organometallic chemistry 2020-11, Vol.34 (11), p.n/a
• Main Authors: Li, Jian‐Rong, Hu, Meng‐Yuan, Lü, Shuang, Gu, Xiao‐Li, Jing, Xing‐Bin, Zhao, Pei‐Hua
• Format: Article
• Language: English
• Subjects: [FeFe]‐hydrogenase models; Acetic acid; Carbon monoxide; Chemical analysis; Chemistry; Coordination compounds; Crystallography; electrocatalytic property; Electrochemical analysis; Infrared analysis; Infrared spectroscopy; Ligands; NMR spectroscopy; Phosphines; Protonation; Protons; Reduction; Refluxing; Substitution reactions; synthesis; Toluene; variable substitutions; Xylene
• ISSN: 0268-2605; 1099-0739
• DOI: 10.1002/aoc.5929

As diiron subsite models of [FeFe]‐hydrogenases for catalytic proton reduction to hydrogen (H2), a new series of the phosphine‐substituted diiron ethanedithiolate complexes Fe2(μ‐edt)(CO)6‐nLn (n = 1, 2) were prepared from the variable substitutions of all‐CO precursor Fe2(μ‐edt)(CO)6 (A) and tertiary phosphines (L1‐L4) under different reaction conditions. While the Me3NO‐assisted substitutions of A and one equiv. ligands L1‐L4 [L = Ph2P(CH2NHBut), Ph2P(CH2CH2NH2), Ph2P(NHBut), and Ph2P(C6H4Me‐p)] produced the monosubstituted complexes Fe2(μ‐edt)(CO)5L (1–4) in good yields, the refluxing xylene solution of A and two equiv. ligand L1 prepared complex Fe2(μ‐edt)(CO)5{κ1‐Ph2P(CH2NHBut)} (1) in low yield. Meanwhile, the UV‐irradiated toluene solution of A and two equiv. ligand L3 resulted in the rare formation of the disubstituted complex Fe2(μ‐edt)(CO)4{κ1, κ1‐(Ph2PNHBut)2} (5) in low yield, whereas the Me3NO‐assisted substitution of A and two equiv. ligand L4 afforded the disubstituted complex Fe2(μ‐edt)(CO)4{κ1, κ1‐(Ph2PC6H4Me‐p)2} (6) in good yield. All the model complexes 1–6 have been characterized by elemental analysis, FT‐IR, NMR spectroscopy, and particularly for 1, 3, 5 by X‐ray crystallography. Further, the protonations of complexes 1–4 are studied and compared with excess acetic acid (HOAc) and trifluoroacetic acid (TFA) by using FT‐IR and NMR techniques. Additionally, the electrochemical and electrocatalytic properties of model complexes 1–6 are investigated and compared by cyclic voltammetry (CV), suggesting that they are electrocatalytically active for proton reduction to H2 in the presence of HOAc. A new series of the mono‐ and disubstituted diiron edt complexes 1–6 with tertiary phosphines are prepared and structurally characterized, aiming to explore the impact of coordination modes of tertiary phosphines on the molecular structures and electrocatalytic properties of diiron model complexes related to [FeFe]‐hydrogenases for proton reduction to H2.