• Login
• Admin

Perotto, Carlo U. and Sodipo, Charlene L. and Jones, Graham J. and Tidey, Jeremiah P. and Blake, Alexander J. and Lewis, William and Davies, E. Stephen and McMaster, Jonathan and Schröder, Martin (2018) Heterobimetallic [NiFe] complexes containing mixed CO/CN− ligands: analogs of the active site of the [NiFe] hydrogenases. Inorganic Chemistry, 57 (5). pp. 2258-2569. ISSN 1520-510X

Abstract

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 to −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) calculations, are consistent with a NiIIIFeII formulation for [Ni(N2S3)Fe(CO)2(CN)2]+. The SOMO in [Ni(N2S3)Fe(CO)2(CN)2]+ is based on Ni 3dz² and 3p S with the S contributions deriving principally from the apical S-donor. The nature of the SOMO corresponds to that proposed for the Ni-C state of the [NiFe] hydrogenases for which a NiIIIFeII formulation has also been proposed. A comparison of the experimental structures, and the electrochemical and spectroscopic properties of [Ni(N2S3)Fe(CO)2(CN)2] and its [Ni(N2S3)] precursor, together with calculations on the oxidized [Ni(N2S3)Fe(CO)2(CN)2]+ and [Ni(N2S3)]+ forms suggests that the binding of the {Fe(CO)(CN)2} unit to the {Ni(CysS)4} center at the active site of the [NiFe] hydrogenases suppresses thiolate-based oxidative chemistry involving the bridging thiolate S donors. This is in addition to the role of the Fe center in modulating the redox potential and geometry, and supporting a bridging hydride species between the Ni and Fe centers in the Ni-C state..

Actions (Archive Staff Only)

Edit View