Hydrogen-atom transfer (HAT) initiated by intramolecular ligand-metal electron transfer

• Verfasst von: Herrmann, Hendrik Hans [VerfasserIn]
• Verfasst von: Kaifer, Elisabeth [VerfasserIn]
• Verfasst von: Himmel, Hans-Jörg [VerfasserIn]
• Titel: Hydrogen-atom transfer (HAT) initiated by intramolecular ligand-metal electron transfer
• Verf.angabe: Hendrik Herrmann, Elisabeth Kaifer, and Hans-Jörg Himmel
• Umfang: 9 S.
• Fussnoten: First published 20 February 2017 ; Gesehen am 08.06.2018
• Titel Quelle: Enthalten in: Chemistry - a European journal
• Jahr Quelle: 2017
• Band/Heft Quelle: 23(2017), 23, S. 5520-5528
• ISSN Quelle: 1521-3765
• DOI: doi:10.1002/chem.201605971
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 1576192628

Abstract

Hydrogen-atom transfer (HAT) is of key importance for several catalytic and biological processes, and provides an elegant access to C−H activation. In synthetic chemistry, a photoactivated metal complex is often employed to abstract an oxygen- or nitrogen-bound hydrogen, and the as-generated oxygen- or nitrogen-centered radical is the hydrogen-atom acceptor for HAT. Here, we report the first examples for HAT processes initiated by one-electron oxidation of urea azines. A further novelty is that the HAT-initiating oxidation can be realized by intramolecular ligand-metal electron transfer in copper(II)-urea azine complexes. These complexes are first characterized in the solid state, in which they are stable. Electron-transfer-initiated HAT processes are observed upon dissolving the complexes in organic solvents, and the kinetics of these processes varies with the solvent polarity. The carbon-centered radicals formed by HAT can either be trapped with 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) or undergo radical recombination reactions with itself, yielding diamagnetic end-products.