Heterobimetallic [NiFe] Complexes Containing Mixed CO/CN- Ligands: Analogs of the Active Site of the [NiFe] Hydrogenases

The development of synthetic analogs of the active sites of [NiFe] hydrogenases remains challenging, and, in spite of the number of complexes featuring a [NiFe] center, those featuring CO and CN– ligands at the Fe center are under-represented. We report herein the synthesis of three bimetallic [NiFe] complexes [Ni(N2S2)Fe(CO)2(CN)2], [Ni(S4)Fe(CO)2(CN)2], and [Ni(N2S3)Fe(CO)2(CN)2] that each contain a Ni center that bridges through two thiolato S donors to a {Fe(CO)2(CN)2} unit. X-ray crystallographic studies on [Ni(N2S3)Fe(CO)2(CN)2], supported by DFT calculations, are consistent with a solid-state structure containing distinct molecules in the singlet (S = 0) and triplet (S = 1) states. Each cluster exhibits irreversible reduction processes between −1.45 and −1.67 V vs Fc+/Fc and [Ni(N2S3)Fe(CO)2(CN)2] possesses a reversible oxidation process at 0.17 V vs Fc+/Fc. Spectroelectrochemical infrared (IR) and electron paramagnetic resonance (EPR) studies, supported by density functional theory (DFT) calculati...