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 [NiIII (F)(L)] (2, L=N,N'-(2,6-dimethylphenyl)-2,6-pyridinedicarboxamidate) was prepared from [NiII (F)(L)]- (1) by oxidation with selectfluor. Complexes 1 and 2 were characterized by using 1 H/19 F 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 [NiIII (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.