C-H Bond Trifluoromethylation of Arenes Enabled by a Robust, High-Valent Nickel(IV) Complex

The robust, high-valent Ni-IV complex [(Py)(2)(NiF2)-F-IV(CF3)(2)] (Py=pyridine) was synthesized and fully characterized by NMR spectroscopy, X-ray diffraction, and elemental analysis. It reacts with aromatic compounds at 25 degrees C to form the corresponding benzotrifluorides in nearly quantitative yield. The monomeric and dimeric (NiCF3)-C-III complexes 2Py 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-CF3 bond-forming sequence can occur both at (NiCF3)-C-IV and (NiCF3)-C-III centers.