C-N Bond Formation from a Masked High-Valent Copper Complex Stabilized by Redox Non-Innocent Ligands
S¦bastien Blanchard, Marine Desage-El Murr,* and Louis Fensterbank*
Dr. M. Desage-El Murr, Prof. L. Fensterbank
Sorbonne Universit¦s, UPMC, Universit¦ Paris 06, UMR CNRS 8232
Institut Parisien de Chimie Mol¦culaire (France)
German Edition: DOI: 10.1002/ange.201605132
Abstract:
The reactivity of a stable copper(II) complex bearing fully oxidized iminobenzoquinone redox ligands towards nucleophiles is described. In sharp contrast with its genuine low-valent counterpart bearing reduced ligands, this complex performs high-yielding C¢N bond formations. Mechanistic
studies suggest that this behavior could stem fromamechanism akin to reductive elimination occurring at the metal center but facilitated by the ligand: it is proposed that a masked high
oxidation state of the metal can be stabilized as a lower copper(II) oxidation state by the redox ligands without forfeiting its ability to behave as a high-valent copper(III) center. These observations are substantiated by a combination of advanced EPR spectroscopy techniques with DFT studies.
This work sheds light on the potential of redox ligands as promoters of unusual reactivities at metal centers and illustrates the concept of masked high-valent metallic species.
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