Zirconium Complexes Bearing Methyl/tButyl Salicylate and Their Catalytic Activity on ε-Caprolactone

In this study, methyl/tbutyl salicylate bearing zirconium complexes (C1-C8) were prepared by reaction of zirconium (IV) propoxide/butoxide with salicylic acid, 3-methylsalicylic acid, 4-methylsalicylic acid, and 3,5-di-tert-butylsalicylic acid in alcohols, respectively. All these complexes (C1-C8) were characterized by 1H-NMR, 13C-NMR, FTIR, mass spectroscopy (MS), elemental, and thermogravimetric analyses (TGA). These complexes were utilized as catalysts in ring opening polymerization (ROP) of ε-caprolactone and were very effective. Polycaprolactone (PCL) was characterized by 1H-NMR, 13C-NMR, and gel permeation chromatography (GPC). In this study, perhaps for the first time, the effects of electron donating substituents (Me and tBu) on ε-caprolactone polymerization reactions on salicylate ligands linked to zirconium atoms were investigated.