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Abstract Intermediates relevant to cobalt‐catalyzed alkene hydroformylation have been isolated and evaluated in fundamental organometallic transformations relevant to aldehyde formation. The 18‐electron (R,R)‐(iPrDuPhos)Co(CO)2H has been structurally characterized, and it promotes exclusive hydrogenation of styrene in the presence of 50 bar of H2/CO gas (1:1) at 100 °C. Deuterium‐labeling studies established reversible 2,1‐insertion of styrene into the Co−D bond of (R,R)‐(iPrDuPhos)Co(CO)2D. Whereas rapid β‐hydrogen elimination from cobalt alkyls occurred under an N2atmosphere, alkylation of (R,R)‐(iPrDuPhos)Co(CO)2Cl in the presence of CO enabled the interception of (R,R)‐(iPrDuPhos)Co(CO)2C(O)CH2CH2Ph, which upon hydrogenolysis under 4 atm H2produced the corresponding aldehyde and cobalt hydride, demonstrating the feasibility of elementary steps in hydroformylation. Both the hydride and chloride derivatives, (X=H−, Cl−), underwent exchange with free13CO. Under reduced pressure, (R,R)‐(iPrDuPhos)Co(CO)2Cl underwent CO dissociation to form (R,R)‐(iPrDuPhos)Co(CO)Cl.
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Atom-by-atom electrodeposition of single isolated cobalt oxide molecules and clusters for studying the oxygen evolution reaction
We report an electrodeposition protocol for preparing isolated cobalt oxide single molecules (Co1Ox) and clusters (ConOy) on a carbon fiber nanoelectrode. The as-prepared deposits are able to produce well-defined steady-state voltammograms for the oxygen evolution reaction (OER) in alkaline media, where the equivalent radius (rd) is estimated by the limiting current of hydroxide oxidation in accordance with the electrocatalytic amplification model. The size of isolated clusters obtained from the femtomolar Co2+solution through an atom-by-atom technique can reach as small as 0.21 nm (rd) which is approximately the length of Co–O bond in cobalt oxide. Therefore, the deposit was close to that of a Co1Oxsingle molecule with only one cobalt ion, the minimum unit of the cobalt-based oxygen-evolving catalyst. Additionally, the size-dependent catalysis of the OER on ConOydeposits shows a faster relative rate on the smaller cluster in terms of the potential at a given current density, implying the single molecular catalyst shows a superior OER activity.
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- Award ID(s):
- 1707384
- PAR ID:
- 10156459
- Publisher / Repository:
- Proceedings of the National Academy of Sciences
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 117
- Issue:
- 23
- ISSN:
- 0027-8424
- Page Range / eLocation ID:
- p. 12651-12656
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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