Dinucleating Amino-Phenolate Platform for Zinc Catalysts: Impact on Lactide Polymerization

Area of Science:

• Coordination Chemistry
• Polymerization Catalysis
• Organometallic Chemistry

Background:

• Dinucleating ligands are crucial for developing cooperative bimetallic catalysts.
• Zinc complexes are versatile catalysts for various organic transformations.
• Lactide polymerization is a key process for producing biodegradable polymers.

Purpose of the Study:

• To synthesize and characterize novel imine- and amine-based dinucleating ligands with a bisphenol backbone.
• To explore the coordination chemistry of these ligands with zinc, forming various zinc complexes.
• To evaluate the catalytic activity of these zinc complexes in lactide ring-opening polymerization.

Main Methods:

• Synthesis of imine- and amine-based dinucleating ligands.
• Coordination of ligands with zinc precursors to form metal complexes.
• Full characterization of resulting dinuclear and trinuclear zinc complexes using spectroscopic and analytical techniques.
• Catalytic testing of zinc complexes in lactide ring-opening polymerization.

Main Results:

• Successfully synthesized and characterized imine- and amine-based dinucleating ligands and their corresponding zinc complexes (alkyl, alkoxide, acetate, amide).
• Demonstrated the ability of the ligand framework to support both dinuclear and trinuclear zinc complexes.
• Amine-based complexes exhibited higher reactivity than imine-based analogues in lactide polymerization.
• Trinuclear zinc alkyl species displayed remarkable control and reproducibility in lactide polymerization.
• Observed that the formation of trinuclear clusters can influence the extent of bimetallic cooperation.

Conclusions:

• The developed bisphenol-based dinucleating ligands effectively support diverse zinc complexes, including multinuclear species.
• Zinc complexes derived from these ligands are active catalysts for lactide ring-opening polymerization.
• Trinuclear zinc alkyl complexes offer superior control and reproducibility, highlighting the potential of multinuclear catalysis.
• Ligand design plays a critical role in modulating catalytic activity and the extent of cooperative effects in zinc-catalyzed polymerization.