Selenium-bridged diiron hexacarbonyl complexes as biomimetic models for the active site of Fe-Fe hydrogenases

Three N-substituted selenium-bridged diiron complexes [{(mu-SeCH2)2NC6H4R}Fe2(CO)6] (R = 4-NO2, 7; R = H, 8; R = 4-CH3, 9) were firstly prepared as biomimetic models for the Fe-Fe hydrogenases active site. Models could be generated by the convergent reaction of [(mu-HSe)2Fe2(CO)6] (6) with N,N-bis(hydroxymethyl)-4-nitroaniline (1), N,N-bis(hydroxymethyl)aniline (2), and N,N-bis(hydroxymethyl)-4-methylaniline (3) in 46-52% yields. All the new complexes were characterized by IR, 1H and 13C NMR and HRMS spectra and their molecular structures were determined by single-crystal X-ray analysis. The redox properties of and their dithiolate analogues [{(mu-SCH2)2NC6H4R}Fe2(CO)6] (R = 4-NO2, 7s; R = H, 8s; R = 4-CH3, 9s ) were evaluated by cyclic voltammograms. The electrochemical proton reduction by and were investigated in the presence of p-toluenesulfonic acid (HOTs) to evaluate the influence of changing the coordinating S atoms of the bridging ligands to Se atoms on the electrocatalytic activity for proton reduction.