Activation of Molecular Oxygen by a Cobalt(II) Tetra‐NHC Complex. Issue 4 (10th December 2020)

• Record Type: Journal Article
• Authors: Schlagintweit, Jonas F.; Altmann, Philipp J.; Böth, Alexander D.; Hofmann, Benjamin J.; Jandl, Christian; Kaußler, Clemens; Nguyen, Linda; Reich, Robert M.; Pöthig, Alexander; Kühn, Fritz E.
• Is Part Of: Chemistry. Volume 27:Issue 4(2021)
• Page Start: 1311
• Page End: 1315
• Publication Date: 2020-12-10
• Subjects: cobalt -- dioxygen activation -- dioxygen ligands -- macrocyclic ligands -- N-heterocyclic carbenes; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.202004758
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The first dicobalt(III) μ 2 ‐peroxo N ‐heterocyclic carbene (NHC) complex is reported. It can be quantitatively generated from a cobalt(II) compound bearing a 16‐membered macrocyclic tetra‐NHC ligand via facile activation of dioxygen from air at ambient conditions. The reaction proceeds via an end‐on superoxo intermediate as demonstrated by EPR studies and DFT. The peroxo moiety can be cleaved upon addition of acetic acid, yielding the corresponding Co III acetate complex going along with H2 O2 formation. In contrast, both Co II and Co III complexes are also studied as catalysts to utilize air for olefin and alkane oxidation reactions; however, not resulting in product formation. The observations are rationalized by DFT‐calculations, suggesting a nucleophilic nature of the dicobalt(III) μ 2 ‐peroxo complex. All isolated compounds are characterized by NMR, ESI‐MS, elemental analysis, EPR and SC‐XRD. Abstract : Hydrogen peroxide from air : Upon reaction of O2 from air with a cobalt(II) tetra N ‐heterocyclic carbene (NHC) complex at ambient conditions, the first reported dicobalt(III) μ 2 ‐peroxo NHC is formed (see scheme). The reaction proceeds by an elusive end‐on superoxo species, as demonstrated by EPR and DFT. The μ 2 ‐peroxo complex is applied to obtain hydrogen peroxide from air, when reacted with Brønsted acids.