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We report a family of cobalt complexes based on bidentate phosphine ligands with two, one, or zero pendent amine groups in the ligand backbone. The pendent amine complexes are active electrocatalysts for the formate oxidation reaction, generating CO2 with near-quantitative faradaic efficiency at moderate overpotentials (0.45 – 0.57 V in acetonitrile). These homogeneous electrocatalysts are the first cobalt example and second first-row transition metal example for formate oxidation. Thermodynamic measurements reveal these complexes are energetically primed for formate oxidation via hydride transfer to the cobalt center, followed by deprotonation of the resulting cobalt-hydride by formate acting as a base. The complex with the strongest cobalt- hydride bond, given by its thermodynamic hydricity, is the fastest electrocatalyst in this series, with an observed rate constant for formate oxidation of 135 ± 8 h−1 at 25 °C. Electrocatalytic turnover is not observed for the complex with no pendent amine groups: decomposition of the complex structure is evident in the presence of high formate concentrations.
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Influence of Metal Identity in Bipyridine-Based Metal-4N Complexes With Formate
We present the vibrational spectra of a series of dicationic, organometallic complexes consisting of a transition metal center (Co, Ni, or Cu) coordinated by 4,4′-di(tert-butyl)- 2,2′-bipyridine (DTBbpy) ligands and a formate adduct. Spectral features are analyzed and assigned through comparison with density functional theory calculations, and structures are reported. Natural population analysis shows that the DTBbpy ligands serve as flexible charge reservoirs in each complex. Shifts in the vibrational signatures of the formate moiety reveal that the nature of the metal center plays a crucial role in the charge distribution and formate−metal binding motif in each complex, illustrating the impact of the metal center on the structural and electronic properties of these complexes.
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- PAR ID:
- 10517651
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- The Journal of Physical Chemistry A
- Volume:
- 127
- Issue:
- 36
- ISSN:
- 1089-5639
- Page Range / eLocation ID:
- 7586 to 7593
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1021/acs.jpca.3c04496
