Tetrahydrosalen backboned gadolinium complex as initiator for the ring-opening polymerization of ɛ-caprolactone

Tetrahydrosalen ligand was employed in the synthesis of gadolinium complex. The ligand was deprotoned by LiBu, and the afforded lithium salt was reacted with anhydrous GdCl3 to produce the gadolinium complex through salt metathesis. This complex was successfully used to initiate the ring-opening polymerization of ɛ-caprolactone. The initiation conditions in different temperature, monomer-to-initiator ratio and time were investigated. Under the condition: [ɛ-caprolactone]:[catalyst] = 600, 56 °C, toluene: 2 ml, poly(ɛ-caprolactone) (PCL) with Mw = 11,2782 and PDI = 1.96 was achieved.