Reductive amination under hydrogen pressure is a valuable process in organic chemistry to access amine derivatives from aldehydes or ketones. Knclkers complex has been shown to be an efficient iron catalyst in this reac- tion. To determine the influence of the substituent on the cyclopentadienone ancillary ligand, a series of modified Knclkers complexes was synthesised and fully characterised. These com- plexes were also transformed into their analogous acetonitrile iron-dicarbonyl complexes. Catalytic activities of these complexes were evaluated and com- pared in a model reaction. The scope of this reaction is also reported. For mechanistic insights, deuterium-label- ling experiments and DFT calculations were undertaken and are also present- ed.