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

• Published in: Angewandte Chemie International Edition 2015-02, Vol.54 (9), p.2745-2749
• Main Authors: Romine, Andrew M., Nebra, Noel, Konovalov, Andrey I., Martin, Eddy, Benet-Buchholz, Jordi, Grushin, Vladimir V.
• Format: Article
• Language: English
• Subjects: air oxidation; copper; Crystals; Diffraction; fluorine; organometallic synthesis; trifluoromethylation
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201411348

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 as it gets: The CuIII anion [Cu(CF3)4]− is finally easily accessible through the newly developed exceedingly simple and highly efficient one‐step procedure directly from CuCl. The reaction occurs at room temperature in air to furnish quantitatively [Cu(CF3)4]−, which can be used for the synthesis of other, previously unknown CF3CuIII compounds.