Synthesis and Structure of Analogues for the Ni-Fe Site in Hydrogenase Enzymes

Dithiolate bridging Ni−Fe complexes [(dppe)NiII(μ-SEt)2FeII(CN)2(CO)2]6 and [(dppe)NiII(μ-pdt)FeII(CN)2(CO)2] [dppe = 1,2-bis(diphenylphosphino)ethane and pdt = 1,3-propanedithiolate] have been synthesized and structurally characterized as structural analogues of the active site of Ni−Fe hydrogenase enzymes. The synthesis starts from key intermediate fac-[Fe(CN)2(CO)3I]−. [(dppe)NiII(μ-SEt)2FeII(CN)2(CO)2]6, which features a near-planar diethanethiolate-bridged Ni−Fe rhomb, and the arrangement of 2CN− ligands is cis to each other. In contrast, [(dppe)NiII(μ-pdt)FeII(CN)2(CO)2] shows a much more folded NiS2Fe rhomb, a short Ni−Fe distance, trans 2CN− ligands, and a semibridging CN− between Ni and Fe.