Some sterically very bulky salicylaldimine ligands were designed and prepared. In the ligand framework, bulky aryl substituents were installed on the ortho position of the salicylaldimine backbone as well as the ortho position of the aniline moiety. Subsequently, the corresponding zinc complexes were prepared and characterized. The zinc complexes bearing electron-withdrawing and bulky substituents on both positions showed much higher activity and much better controlled behavior in the ring opening polymerization of epsilon-caprolactone than the complexes bearing sterically less bulkier alkyl substituents.