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 CuIII 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.
Easy Access to the Copper(III) Anion [Cu(CF3)4]-
Angew. Chem. Int. Ed. 2015, 54, 2745-2749.