Ligand Effects on Hydrogen Atom Transfer from Hydrocarbons to Three-Coordinate Iron Imides

A new β-diketiminate ligand with 2,4,6-tri­(phenyl)­phenyl N-substituents provides protective bulk around the metal without exposing any weak C–H bonds. This ligand improves the stability of reactive iron­(III) imido complexes with FeNAd and FeNMes functional groups (Ad = 1-adamantyl; Mes = mesityl). The new ligand gives iron­(III) imido complexes that are significantly more reactive toward 1,4-cyclohexadiene than the previously reported 2,6-diisopropylphenyl diketiminate variants. Analysis of X-ray crystal structures implicates FeN–C bending, a longer FeN bond, and greater access to the metal as potential reasons for the increase in C–H bond activation rates.