Easy Access to the Copper(III) Anion [Cu(CF3)4]-

CuCl or pre-generated CuCF3 reacts with CF3SiMe3/KF in DMF in air to give [Cu(CF3)(4)](-) quantitatively. [PPN](+), [Me4N](+), [Bu4N](+), [PhCH2NEt3](+), and [Ph4P](+) salts of [Cu(CF3)(4)](-) were prepared and isolated spectroscopically and analytically pure in 82-99% yield. X-ray structures of the [PPN](+), [Me4N](+), [Bu4N](+), and [Ph4P](+) 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 2.3kcalmol(-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.