N-HETEROCYCLIC CARBENE ZINC AND MAGNESIUM COMPLEXES FOR THE SYNTHESIS OF RENEWABLE POLYMERS

The shift from petroleum-based plastics to sustainable alternatives poses a significant challenge for modern society, in which catalysis plays a pivotal role enabling efficient and selective synthesis of eco-friendly polymers. Among the most promising candidates, aliphatic polyesters and polycarbonates stand out for their renewability and their closed-loop life cycles. The controlled synthesis of these polymers is best achieved through ring-opening polymerization (ROP) of cyclic monomers, with non-toxic metal complexes serving as efficient and sustainable catalysts. In this work, we explore the use of N-Heterocyclic Carbene (NHC) ligands as coordination environments for zinc and magnesium centers (Figure 1). The resulting metal complexes exhibit good catalytic activity in the controlled ROP of various cyclic monomers, including lactones, like lactide. and ε-caprolactone, as well as cyclic carbonates, like trimethylene carbonate and its alkyl-substituted derivatives, purposely synthesized from renewable feedstocks, such as CO₂ and 1,3-diols. The versatility of these catalytic systems was further demonstrated by their ability to promote both the synthesis of ester/carbonate copolymers and the methanolysis of polylactide (PLA), effectively closing its lifecycle