Electrocatalytic Proton Reduction by a Cobalt Complex Containing a Proton‐Responsive Bis(alkylimdazole)methane Ligand: Involvement of a C−H Bond in H2Formation
Open Access
- 30 April 2020
- journal article
- research article
- Published by Wiley in Chemistry – A European Journal
- Vol. 26 (55), 12560-12569
- https://doi.org/10.1002/chem.201905746
Abstract
Homogeneous electrocatalytic proton reduction is reported using cobalt complex [ 1 ](BF 4 ) 2 . This complex comprises two bis(1‐methyl‐4,5‐diphenyl‐1H‐imidazol‐2‐yl)methane (HBMIM Ph2 ) ligands that contain an acidic methylene moiety in their backbone. Upon reduction of [ 1 ](BF 4 ) 2 by either electrochemical or chemical means, one of its HBMIM Ph2 ligands undergoes deprotonation under the formation of dihydrogen. Addition of a mild proton source (acetic acid) to deprotonated complex [ 2 ](BF 4 ) regenerates protonated complex [ 1 ](BF 4 ) 2 . In presence of acetic acid in acetonitrile solvent [ 1 ](BF 4 ) 2 shows electrocatalytic proton reduction with a k obs of ~200 s ‐1 at an overpotential of 590 mV. Mechanistic investigations supported by Density Functional Theory (BP86) reveal that dihydrogen formation takes place in an intramolecular fashion through the participation of a methylene C–H bond of the HBMIM Ph2 ligand and a Co II –H bond through formal heterolytic splitting of the latter. These results represent the joint involvement of a base metal‐hydride and a C–H bond in electrocatalytic proton reduction and are of interest to the development of responsive ligands for molecular (base)metal (electro)catalysis.Funding Information
- Universiteit Utrecht
This publication has 41 references indexed in Scilit:
- Cobalt-dithiolene complexes for the photocatalytic and electrocatalytic reduction of protons in aqueous solutionsProceedings of the National Academy of Sciences of the United States of America, 2012
- [Ni(PMe2NPh2)2](BF4)2 as an Electrocatalyst for H2 ProductionACS Catalysis, 2012
- Catalytic mechanisms of hydrogen evolution with homogeneous and heterogeneous catalystsEnergy & Environmental Science, 2011
- H2 Evolution and Molecular Electrocatalysts: Determination of Overpotentials and Effect of HomoconjugationInorganic Chemistry, 2010
- Thermochemistry of Proton-Coupled Electron Transfer Reagents and its ImplicationsChemical Reviews, 2010
- Concerted Proton−Electron Transfers: Electrochemical and Related ApproachesAccounts of Chemical Research, 2010
- Proton-Coupled Electron TransferChemical Reviews, 2007
- Single-Ion Solvation Free Energies and the Normal Hydrogen Electrode Potential in Methanol, Acetonitrile, and Dimethyl SulfoxideThe Journal of Physical Chemistry B, 2006
- Powering the planet: Chemical challenges in solar energy utilizationProceedings of the National Academy of Sciences of the United States of America, 2006
- Electrocatalytic hydrogen evolution by cobalt difluoroboryl-diglyoximate complexesChemical Communications, 2005