Thermodynamics of Hydrogen Atom Transfer to a High-Valent Iron Imido Complex

Thermodynamic investigations relevant to hydrogen atom transfer by the high-valent iron imido complex [LMesFe⋮NAd]OTf have been undertaken. The complex is found to be weakly oxidizing by cyclic voltammetry (E1/2 = −0.98 V vs Cp2Fe+/Cp2Fe in MeCN). A combination of experimental and computational studies has been used to determine the acidity of LMesFe−N(H)Ad+ (pKa = 37 in MeCN), allowing the N−H BDFE (88(5) kcal/mol) to be calculated from a thermodynamic cycle. Consistent with this value, [LMesFe⋮NAd]OTf reacts with 9,10-dihydroanthracene (C−H BDE = 78(1) kcal/mol) to form anthracene.