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.

二硫醇桥联镍铁配合物[(dppe)NiII(μ-SEt)2FeII(CN)2(CO)2]₆与[(dppe)NiII(μ-pdt)FeII(CN)2(CO)2]（其中dppe为1,2-双(二苯基膦)乙烷（1,2-bis(diphenylphosphino)ethane），pdt为1,3-丙二硫醇盐（1,3-propanedithiolate)）已被合成并完成结构表征，作为镍铁氢化酶活性位点的结构类似物。该合成以关键中间体面式-[Fe(CN)2(CO)3I]⁻为起始原料。[(dppe)NiII(μ-SEt)2FeII(CN)2(CO)2]₆具有近平面型二乙硫醇桥联镍铁菱形结构，且两个CN⁻配体呈顺式排布。与之相反，[(dppe)NiII(μ-pdt)FeII(CN)2(CO)2]的NiS₂Fe菱形结构弯折程度更大，Ni−Fe键长更短，两个CN⁻配体呈反式排布，且在Ni与Fe之间存在一个半桥联CN⁻配体。