Dicationic Thiolate-Bridged Diruthenium Complexes for Catalytic Oxidation of Molecular Dihydrogen

Yuki, Masahiro; Sakata, Ken; Nakajima, Kazunari; Kikuchi, Syoma; Sekine, Shinobu; Kawai, Hiroyuki; Nishibayashi, Yoshiaki

doi:10.1021/acs.organomet.7b00764

Cited by 6 publications

(2 citation statements)

References 103 publications

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“…Recently, Nishibayashi and co-workers reported a diruthenium complex that performs H 2 oxidation in water and demonstrated, via DFT calculations, that water acts as a base in the transformation. In their system, the calculated barrier to H–H bond cleavage was rather low (∼5 kcal/mol).…”

Section: Resultsmentioning

confidence: 99%

Selective Oxidation of H₂ and CO by NiIr Catalyst in Aqueous Solution: A DFT Mechanistic Study

2020

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One of the challenges in utilizing hydrogen gas (H 2 ) as a sustainable fossil fuel alternative is the inhibition of H 2 oxidation by carbon monoxide (CO), which is involved in the industrial production of H 2 sources. To solve this problem, a catalyst that selectively oxidizes either CO or H 2 or one that co-oxidizes H 2 and CO is needed. Recently, a NiIr catalyst [Ni II Cl(X)Ir III Cl(η 5 -C 5 Me 5 )], (X = N,N′dimethyl-3,7-diazanonane-1,9-dithiolate), which efficiently and selectively oxidizes either H 2 or CO depending on the pH, has been developed (Angew. Chem. Int. Ed. 2017, 56, 9723−9726). In the present work, density functional theory (DFT) calculations are employed to elucidate the pH-dependent reaction mechanisms of H 2 and CO oxidation catalyzed by this NiIr catalyst. During H 2 oxidation, our calculations suggest that dihydrogen binds to the Ir center and generates an Ir(III)−dihydrogen complex, followed by subsequent isomerization to an Ir(V)−dihydride species. Then, a proton is abstracted by a buffer base, CH 3 COO − , resulting in the formation of a hydride complex. The catalytic cycle completes with electron transfer from the hydride complex to a protonated 2,6-dichlorobenzeneindophenol (DCIP) and a proton transfer from the oxidized hydride complex to a buffer base. The CO oxidation mechanism involves three distinct steps, i.e., (1) formation of a metal carbonyl complex, (2) formation of a metallocarboxylic acid, and (3) conversion of the metallocarboxylic acid to a hydride complex. The formation of the metallocarboxylic acid involves nucleophilic attack of OH − to the carbonyl-C followed by a large structural change with concomitant cleavage of the Ir−S bond and rotation of the COOH group along the NiIr axis. During the conversion of the metallocarboxylic acid to the hydride complex, intramolecular proton transfer followed by removal of CO 2 leads to the formation of the hydride complexes. In addition, the barrier heights for the binding of small molecules (H 2 , OH − , H 2 O, and CO) to Ir were calculated, and the results indicated that dissociation from Ir is a faster process than the binding of H 2 O and H 2 . These calculations indicate that H 2 oxidation is inhibited by CO and OH − and thus prefers acidic conditions. In contrast, the CO oxidation reactions occur more favorably under basic conditions, as the formation of the metallocarboxylic acid involves OH − attack to a carbonyl-C and the binding of OH − to Ni largely stabilizes the triplet spin state of the complex. Taken together, these calculations provide a rationale for the experimentally observed pH-dependent, selective oxidations of H 2 and CO.

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Section: Resultsmentioning

confidence: 99%

Selective Oxidation of H₂ and CO by NiIr Catalyst in Aqueous Solution: A DFT Mechanistic Study

2020

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“…In other hand, the notable progress also has been made in the developments for hydrogen oxidation catalysts with transition metal complexes. [16][17][18][19][20] However, there have been few complexes reported in the literature that can act efficiently as both hydrogen oxidation catalysts (HOCs) and hydrogen evolution catalysts (HECs). [5,21] To this end, we focus our interests on the design of new complexes that catalyze the reaction in both directions (hydrogen evolution and oxidation).…”

Section: Introductionmentioning

confidence: 99%

A bis(thiosemicarbazonato)‐zinc complex, an electrocatalyst for hydrogen evolution and oxidation via ligand‐assisted metal‐centered reactivity

Yang

Wang

et al. 2022

Applied Organom Chemis

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Based on that hydrogen energy is widely used in fuel cells, the design and research of new catalysts for both hydrogen evolution reactions (HERs) and hydrogen oxidation reactions (HORs) are becoming increasingly important. A new catalyst for both hydrogen evolution and oxidation, based on a zinc complex, [Zn‐ATSE]2, is designed and provided by the reaction of Zn (CH3CO2)2 with diacetyl‐2‐(4‐N‐ethyl‐3‐thiosemicarbazone)‐3‐(4‐N‐amino‐3‐thiosemicarbazone) (H2ATSE) in our group. Electrochemical investigations show that [Zn‐ATSE]2 can electro‐catalyze hydrogen evolution from acetic acid with a turnover frequency (TOF) of 64 mol H2 mol catalyst−1 h−1 under an overpotential of 914.6 mV. Moreover, [Zn‐ATSE]2 also can electro‐catalyze hydrogen oxidation with a TOF of 13.52 s−1. The results can be attributed to the hydrazine group of [Zn‐ATSE]2 that can form a ligand‐based radical species. Possible electrocatalytic cycles for H2 production and oxidation by [Zn‐ATSE]2 are afforded. We hope these findings can afford a new method for the design of electrocatalysts for both H2 evolution and H2 oxidation.

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A new catalyst based on a nickel(II) complex of diiminodiphosphine for hydrogen evolution and oxidation

Wang

Yang

et al. 2021

International Journal of Hydrogen Energy

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Dicationic Thiolate-Bridged Diruthenium Complexes for Catalytic Oxidation of Molecular Dihydrogen

Cited by 6 publications

References 103 publications

Selective Oxidation of H₂ and CO by NiIr Catalyst in Aqueous Solution: A DFT Mechanistic Study

Selective Oxidation of H₂ and CO by NiIr Catalyst in Aqueous Solution: A DFT Mechanistic Study

A bis(thiosemicarbazonato)‐zinc complex, an electrocatalyst for hydrogen evolution and oxidation via ligand‐assisted metal‐centered reactivity

A new catalyst based on a nickel(II) complex of diiminodiphosphine for hydrogen evolution and oxidation

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Dicationic Thiolate-Bridged Diruthenium Complexes for Catalytic Oxidation of Molecular Dihydrogen

Cited by 6 publications

References 103 publications

Selective Oxidation of H2 and CO by NiIr Catalyst in Aqueous Solution: A DFT Mechanistic Study

Selective Oxidation of H2 and CO by NiIr Catalyst in Aqueous Solution: A DFT Mechanistic Study

A bis(thiosemicarbazonato)‐zinc complex, an electrocatalyst for hydrogen evolution and oxidation via ligand‐assisted metal‐centered reactivity

A new catalyst based on a nickel(II) complex of diiminodiphosphine for hydrogen evolution and oxidation

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Selective Oxidation of H₂ and CO by NiIr Catalyst in Aqueous Solution: A DFT Mechanistic Study

Selective Oxidation of H₂ and CO by NiIr Catalyst in Aqueous Solution: A DFT Mechanistic Study