Turning on ROP activity in a bimetallic Co/Zn complex supported by a [2+2] Schiff-base macrocycle

Abstract

Homo-dinuclear Co and Zn complexes derived from the macrocycle LH₂, {[2-(OH)-5-(R)-C₆H₂-1,3-(CH)₂][CH₂CH₂(2-C₆H4N)₂]}₂ (R = Me, tBu), revealed near inactivity for the ring opening polymerization (ROP) of the cyclic esters δ-valerolactone (δ-VL) and ε-caprolactone (ε-CL). By contrast, the hetero-bimetallic complexes [LCo(NCMe)(μ-Br)ZnBr]·nMeCN (n = 3 or 3.25) were found to be efficient catalysts for the ROP of ε-CL and δ-VL.