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

摘要

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 H-1/F-19 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 (k(2)=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