Investigation of amino acid containing [FeFe] hydrogenase models concerning pendant base effects

The present investigations deal with the modeling of the peptide surrounding of [FeFe] hydrogenase using amine containing disulphides to simulate possible influences of the amino acid lysine (K237) on the electrochemical and electrocatalytic properties of biomimetic compounds based on [Fe2S2] moieties. Fe3(CO)12 was reacted with Boc-4-amino-1,2-dithiolane, Boc-Adt-OMe (Adt = 4-amino-1,2-dithiolane-4-carboxylic acid, Boc = tert-butoxycarbonyl) and Boc-Adp tert-butyl ester (Adp = (S)-2-amino-3-(1,2-dithiolan-4-yl)propionic acid) to elongate the Fe⋯N distance in comparison to the well known [Fe2{(SCH2)2NR}(CO)6] model complexes. Efforts to deprotect the complexes containing Boc-4-amino-1,2-dithiolane with trifluoroacetic acid result in the formation of [Fe3(μ3-O)(μ-O2C2F3)6(OC4H8)2(H2O)]. The novel [2Fe2S] complexes are characterized using spectroscopic, electrochemical techniques and X-ray diffraction studies.