A well-defined copper complex bearing iminosemiquinone ligands performs single electron reduction of an electrophilic CF₃ ⁺ source into CF^˙ ₃ radicals. This redox behavior is enabled by the ligand which shuttles through two different redox states (iminosemiquinone and iminobenzoquinone) while the copper center is preserved as a Cu(II). This system was used in the trifluoromethylation of silyl enol ethers, heteroaromatics and in the hydrotrifluoromethylation of alkynes. This is the first example of cooperative redox catalysis for the controlled generation of CF^˙ ₃ radicals.

This review provides insights on how enzymatic reactivity tricks such as redox-active ligands, entatic state reactivity, electron bifurcation, and quantum tunneling can benefit chemists in the design of bioinspired catalytic systems.

A simple and straightforward synthesis of N-heterocyclic carbene (NHC)-protected gold nanoparticles is derived from (benz)imidazolium-AuX₄ complexes and NaBH₄ only. The proposed method allows size tuning, from 3 to 6 nm, by adding (benz)imidazolium bromide. Changing the reducing agent to tBuNH₂BH₃ shifts the size range to ca. 6–12 nm. A one pot protocol is also reported from AuCl, (benz)imidazolium bromides and NaBH₄, thereby providing an even more straightforward way of producing NHC-capped gold nanoparticles. In addition, X-ray photoelectron spectroscopy (XPS) is used to unambiguously evidence, on the nanoparticles, the covalent bond formed between the NHC and the surface gold atoms.

Copper catalysis finds applications in various synthetic fields by utilizing the ability of copper to sustain mono- and bielectronic elementary steps. Further to the development of well-defined copper complexes with classical ligands such as phosphines and N-heterocyclic carbenes, a new and fast-expanding area of research is exploring the possibility of a complementing metal-centered reactivity with electronic participation by the coordination sphere. To achieve this electronic flexibility, redox-active ligands can be used to engage in a fruitful “electronic dialogue” with the metal center, and provide additional venues for electron transfer. This review aims to present the latest results in the area of copper-based cooperative catalysis with redox-active ligands.

The reaction of a copper complex bearing iminosemiquinone ligands with a CF₃⁺ source provides an unprecedented Cu^II–CF₃ complex through ligand-based oxidation.