CuCl or pre-generated CuCF3 reacts with CF3 SiMe3 /KF in DMF in air to give [Cu(CF3 )4 ](-) quantitatively. [PPN](+) , [Me4 N](+) , [Bu4 N](+) , [PhCH2 NEt3 ](+) , and [Ph4 P](+) salts of [Cu(CF3 )4 ](-) were prepared and isolated spectroscopically and analytically pure in 82-99% yield. X-ray structures of the [PPN](+) , [Me4 N](+) , [Bu4 N](+) , and [Ph4 P](+) salts were determined. A new synthetic strategy with [Cu(CF3 )4 ](-) was demonstrated, involving the removal of one CF3 (-) from the Cu atom in the presence of an incoming ligand. A novel Cu(III) complex [(bpy)Cu(CF3 )3 ] was thus prepared and fully characterized, including by single-crystal X-ray diffraction. The bpy complex is highly fluxional in solution, the barrier to degenerate isomerization being only 2.3 kcal mol(-1) . An NPA study reveals a huge difference in the charge on the Cu atom in [Cu(CR3 )4 ](-) for R=F (+0.19) and R=H (+0.46), suggesting a higher electron density on Cu in the fluorinated complex.

The robust, high-valent Ni complex [(Py) Ni F (CF ) ] (Py=pyridine) was synthesized and fully characterized by NMR spectroscopy, X-ray diffraction, and elemental analysis. It reacts with aromatic compounds at 25 °C to form the corresponding benzotrifluorides in nearly quantitative yield. The monomeric and dimeric Ni CF complexes 2⋅Py and 2 were identified as key intermediates, and their structures were unambiguously determined by EPR spectroscopy and X-ray diffraction. Preliminary kinetic studies in combination with the isolation of reaction intermediates confirmed that the C-H bond-breaking/C-CF bond-forming sequence can occur both at Ni CF and Ni CF centers.

This mini-review presents a general overview of the progress achieved during the last decade on the amalgamation of CuAAC processes (copper-catalyzed azide-alkyne cycloaddition) with the employment of sustainable solvents as reaction media. In most of the presented examples, the use of water, glycerol (Gly), or deep eutectic solvents (DESs) as non-conventional reaction media allowed not only to recycle the catalytic system (thus reducing the amount of the copper catalyst needed per mole of substrate), but also to achieve higher conversions and selectivities when compared with the reaction promoted in hazardous and volatile organic solvents (VOCs). Moreover, the use of the aforementioned green solvents also permits the improvement of the overall sustainability of the Cu-catalyzed 1,3-dipolar cycloaddition process, thus fulfilling several important principles of green chemistry.