Diiron Thiadithiolates as Active Site Models for the Iron-Only Hydrogenases: Synthesis, Structures, and Catalytic H₂ Production

The first diiron thiadithiolates as active site models for the Fe-only hydrogenases were prepared.
Treatment of Fe3(CO)12 with excess 1,2,4-trithiolane in THF at reflux afforded parent model Fe2
(μ-SCH2)2S(CO)6 (1) in 42% yield. Further treatment of 1 with Cp(CO)2Fe(BF4) prepared in situ from
Cp(CO)2FeI and AgBF4 in CH2Cl2 gave cationic model [Fe2(μ-SCH2)2S(CO)6][Cp(CO)2Fe](BF4) (2) in
81% yield, while treatment of 1 with 2 equiv of Et4NCN in MeCN or with t-BuNC in CH2Cl2 produced
models (Et4N)2[Fe2(μ-SCH2)2S(CO)4(CN)2] (3) and Fe2(μ-SCH2)2S(CO)4(t-BuNC)2 (4) in 93% and 51%
yields, respectively. All the new models 1−4 were characterized by elemental analysis and spectroscopy,
as well as by X-ray crystallography for 1, 2, and 4. Furthermore, model 1 has been proved to be a
catalyst for proton reduction of a weak acid Et3NHCl to give hydrogen under electrochemical conditions.