Toward the Synthesis of Heteroleptic Zinc ROP Initiators Based on Pyridine-Containing Monoalcohols by Tuning Ligand Substituents

Synthesis of two types of complexes (heteroleptic vs homoleptic) is accomplished by an elegant variation of the ligand design. Heteroleptic ethyl zinc complexes 1a–3a were cleanly obtained via ethane elimination. Nevertheless, in the reaction of proligands 3 and 4 with Zn­[N­(SiMe3)2]2 performed at room temperature, only homoleptic complexes 3b and 4b can be isolated. Surprisingly, proligand 2 was found to cleanly produce amide heteroleptic zinc complex 2c in the reaction with Zn­[N­(SiMe3)2]2, and 2c seems to be the most promising in ring-opening polymerization (ROP) among tested initiators in terms of activity.