Biomimics of [FeFe]-hydrogenases incorporating redox-active ligands: synthesis, redox properties and spectroelectrochemistry of diiron-dithiolate complexes with ferrocenyl-diphosphines as FeS surrogates.

[FeFe]-Ase biomimics containing a redox-active ferrocenyl diphosphine have been prepared and their ability to reduce protons and oxidise H studied, including 1,1'-bis(diphenylphosphino)ferrocene (dppf) complexes Fe(CO)(μ-dppf)(μ-S(CH)S) ( = 2, edt; = 3, pdt) and Fe(CO)(μ-dppf)(μ-SAr) (Ar = Ph, -tolyl, -CHNH), together with the more electron-rich 1,1'-bis(dicyclohexylphosphino)ferrocene (dcpf) complex Fe(CO)(μ-dcpf)(μ-pdt). Crystallographic characterisation of four of these show similar overall structures, the diphosphine spanning an elongated Fe-Fe bond ( 2.6 Å), lying to one sulfur and to the second.