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Heterobimetallic [NiFe] complexes containing mixedCO/CN− ligands: analogs of the active site of the [NiFe]hydrogenases

Perotto, Carlo U.; Sodipo, Charlene L.; Jones, Graham J.; Tidey, Jeremiah P.; Blake, Alexander J.; Lewis, William; Davies, E. Stephen; McMaster, Jonathan; Schröder, Martin

Authors

Carlo U. Perotto

Charlene L. Sodipo

Graham J. Jones

Jeremiah P. Tidey

Alexander J. Blake

William Lewis

Martin Schröder M.Schroder@man.ac.uk



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..

Citation

Perotto, C. U., Sodipo, C. L., Jones, G. J., Tidey, J. P., Blake, A. J., Lewis, W., …Schröder, M. (in press). Heterobimetallic [NiFe] complexes containing mixedCO/CN− ligands: analogs of the active site of the [NiFe]hydrogenases. Inorganic Chemistry, 57(5), https://doi.org/10.1021/acs.inorgchem.7b02905

Journal Article Type Article
Acceptance Date Oct 12, 2017
Online Publication Date Feb 21, 2018
Deposit Date Feb 26, 2018
Publicly Available Date Feb 22, 2019
Journal Inorganic Chemistry
Print ISSN 0020-1669
Electronic ISSN 1520-510X
Publisher American Chemical Society
Peer Reviewed Peer Reviewed
Volume 57
Issue 5
DOI https://doi.org/10.1021/acs.inorgchem.7b02905
Public URL http://eprints.nottingham.ac.uk/id/eprint/50008
Publisher URL https://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.7b02905
Copyright Statement Copyright information regarding this work can be found at the following address: http://eprints.nottingham.ac.uk/end_user_agreement.pdf
Additional Information This document is the Accepted Manuscript version of a Published Work that appeared in final form in Inorganic Chemistry, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://pubs.acs.org/doi/abs/10.1021/acs.inorgchem.7b02905

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Copyright Statement
Copyright information regarding this work can be found at the following address: http://eprints.nottingham.ac.uk/end_user_agreement.pdf





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