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.