N2 Reduction on Fe‐Based Complexes with Different Supporting Main‐Group Elements: Critical Roles of Anchor and Peripheral Ligands

Abstract Due to the enigmatic existence of the carbon atom in the MoFeS cluster of iron‐molybdenum cofactor (FeMoco), the design of biomimetic model catalysts featuring a dative bond between a transition metal and a main group atom is an important topic for efficient reduction of N 2 to NH 3 at ambient conditions. Different anchor atoms (X) for the trigonal bipyramidal (XP iPr 3 )Fe (X = B, C, N) catalyst scaffold are investigated by theory. The calculations show that from Lewis acidic B anchor to Lewis basic N or P anchor, the molecular orbital energy levels consisting mainly of Fe 3d orbitals are pushed higher, thus causing stronger backdonation bonding with the π* orbitals of N 2 , which promotes activation of N 2 but impedes reduction of N 2 . The redox‐flexible bonding can act as an electron reservoir and buffer the oxidation state variation of Fe. However, when the FeX bond is less flexible, the peripheral ligands can serve as an extra electron reservoir in the model with Lewis basic anchor. Thus, engineering the peripheral ligand with proper electron‐withdrawing substituent groups can promote reduction of N 2 . The ability to balance well the electron‐donating ability of anchor and electrophilicity of the peripheral ligand is a promising direction toward novel efficient catalysts for N 2 fixation.