In order to gain insighti nto the influence of the H +-accepting terminal ligand in high-valent oxidant mediated protonc oupled electron transfer (PCET) reactions, the reactivity of ah ighv alent nickel-fluoride complex [Ni III (F)(L)] (2,L = N,N'-(2,6-dimethylphenyl)-2,6-pyridinecarboxamidate) with substituted phenols was explored. Analysis of kinetic data from these reactions (Evans-Polanyi, Hammett, and Marcus plots, and KIE measurements) and the formed products show that 2 reacted with electron rich phenols through ah ydrogen atom transfer (HAT, or concerted PCET) mechanism andw ith electron poor phenolst hroughastepwise proton transfer/electron transfer (PT/ET) reaction mechanism. The analogousc omplexes [Ni III (Z)(L)] (Z = Cl, OCO 2 H, O 2 CCH 3 ,O NO 2)r eacted with all phenols through aH AT mechanism. We explore the reasonf or ac hange in mechanism with the highly basic fluoridel igand in 2.C omplex 2 was also found to reacto ne to two orders of magnitude faster than the corresponding analogous [Ni III (Z)(L)] complexes. This was ascribed to ah igh bond dissociation free energy value associated with HÀF(135 kcal mol À1), which is postulated to be the product formed from PCET oxidation by 2 and is believed to be the driving force for the reaction. Our findings show that high-valent metal-fluoride complexes represent ac lass of highly reactiveP CET oxidants.