Fast Hydrocarbon Oxidation by a High-Valent Nickel–Fluoride Complex

In the search for highly reactive oxidants we have identified high-valent metal–fluorides as a potential potent oxidant. The high-valent Ni–F complex Ni^III(F)(L)] ( 2 , L=N,N′-(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate) was prepared from Ni^II(F)(L)]⁻ ( 1 ) by oxidation with selectfluor. Complexes 1 and 2 were characterized by using ¹H/¹⁹F NMR, UV-vis, and EPR spectroscopies, mass spectrometry, and X-ray crystallography. Complex 2 was found to be a highly reactive oxidant in the oxidation of hydrocarbons. Kinetic data and products analysis demonstrate a hydrogen atom transfer mechanism of oxidation. The rate constant determined for the oxidation of 9,10-dihydroanthracene (k₂=29 m ⁻¹ s⁻¹) compared favorably with the most reactive high-valent metallo-oxidants. Complex 2 displayed reaction rates 2000–4500-fold enhanced with respect to Ni^III(Cl)(L)] and also displayed high kinetic isotope effect values. Oxidative hydrocarbon and phosphine fluorination was achieved. Our results provide an interesting direction in designing catalysts for hydrocarbon oxidation and fluorination