Easy Access to the Copper(III) Anion Cu(CF3)4−

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.