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

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

doi:10.1021/acs.inorgchem.7b02905

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

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

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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 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) calculations, are consistent with a Ni^IIIFe^II formulation for [Ni(N₂S₃)Fe(CO)₂(CN)₂]⁺. The singly occupied molecular orbital (SOMO) in [Ni(N₂S₃)Fe(CO)₂(CN)₂]⁺ is based on Ni 3d_z² 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 Ni^IIIFe^II 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.

Original language	English
Pages (from-to)	2558-2569
Number of pages	12
Journal	Inorganic Chemistry
Volume	57
Issue number	5
Early online date	21 Feb 2018
DOIs	https://doi.org/10.1021/acs.inorgchem.7b02905
Publication status	Published - 2018

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@article{1f6a7ada17e94578a68a08132d89b7f1,

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

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 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) calculations, are consistent with a NiIIIFeII formulation for [Ni(N2S3)Fe(CO)2(CN)2]+. The singly occupied molecular orbital (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.",

author = "Perotto, {Carlo U.} and Sodipo, {Charlene L.} and Jones, {Graham J.} and Tidey, {Jeremiah P.} and Blake, {Alexander J.} and William Lewis and Davies, {E. Stephen} and Jonathan McMaster and Martin Schroder",

year = "2018",

doi = "10.1021/acs.inorgchem.7b02905",

language = "English",

volume = "57",

pages = "2558--2569",

journal = "Inorganic Chemistry",

issn = "0020-1669",

publisher = "American Chemical Society",

number = "5",

}

TY - JOUR

T1 - Heterobimetallic [NiFe] Complexes Containing Mixed CO/CN- Ligands: Analogs of the Active Site of the [NiFe] Hydrogenases

AU - Perotto, Carlo U.

AU - Sodipo, Charlene L.

AU - Jones, Graham J.

AU - Tidey, Jeremiah P.

AU - Blake, Alexander J.

AU - Lewis, William

AU - Davies, E. Stephen

AU - McMaster, Jonathan

AU - Schroder, Martin

PY - 2018

Y1 - 2018

N2 - 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) calculations, are consistent with a NiIIIFeII formulation for [Ni(N2S3)Fe(CO)2(CN)2]+. The singly occupied molecular orbital (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.

AB - 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) calculations, are consistent with a NiIIIFeII formulation for [Ni(N2S3)Fe(CO)2(CN)2]+. The singly occupied molecular orbital (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.

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U2 - 10.1021/acs.inorgchem.7b02905

DO - 10.1021/acs.inorgchem.7b02905

M3 - Article

C2 - 29465237

AN - SCOPUS:85042927160

VL - 57

SP - 2558

EP - 2569

JO - Inorganic Chemistry

JF - Inorganic Chemistry

SN - 0020-1669

IS - 5

ER -

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

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CCDC 1584100: Experimental Crystal Structure Determination

CCDC 1584099: Experimental Crystal Structure Determination

CCDC 1584101: Experimental Crystal Structure Determination

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

Abstract

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CCDC 1584100: Experimental Crystal Structure Determination

CCDC 1584099: Experimental Crystal Structure Determination

CCDC 1584101: Experimental Crystal Structure Determination

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