On the Iron(V) Reactivity of an Aggressive Tail-Fluorinated Tetraamido Macrocyclic Ligand (TAML) Activator

The electronic properties of iron tetraamido macrocyclic ligand (TAML) activators of peroxides can be finely and coarsely tuned by varying the substituents on the head and tail macrocyclic components, respectively. By examining the reactivity of the TAML oxidoiron(V) complex with head-NO2 and tail-F substituents, one is able to compare the impact of significantly reduced macrocyclic tetraamide donor capacity on fundamental processes such as hydrogen-atom abstraction, oxygen-atom transfer, and electron transfer by using prior studies with more electron-rich TAML systems. Herein, we demonstrate that the oxidoiron(V) form 3c can be generated by treatment of [Fe{4-NO2C6H3-1,2-((NCOCMe2NCO)-C-2-C-3)(2)CF2(Fe-N-2)(Fe-N-3)}(OH2)](-) (1c) with m-chloroperoxybenzoic acid (mCPBA) in MeCN at -40 degrees C. The oxidation proceeds through the intermediacy of the -oxo[iron(IV)](2) dimer. The overall rate of the (FeFeV)-Fe-III conversion by mCPBA is slightly faster for 1c than that of its less electron-rich precursor [Fe{C6H4-1,2-((NCOCMe2NCO)-C-1-C-2)(2)CMe2(Fe-N-1)(Fe-N-2)}(OH2)](-) (1a). Nevertheless, the oxidative reactivity of 3c toward thioanisole and the hydrocarbons ethylbenzene and cyclohexane exceeds that of 3a by 4.3, 2.1, and 2.6 times, respectively. The reactivity of 3c is significantly greater towards ethylbenzene than that of the oxidoiron(V) species 3b derived from [Fe{C6H4-1,2-((NCOCMe2NCO)-C-1-C-2)(2)NMe(Fe-N-1)(Fe-N-2)}(OH2)](-) (1b).