Macrocyclic Dizinc(II) Alkyl and Alkoxide Complexes: Reversible CO2 Uptake and Polymerization Catalysis Testing

Area of Science:

• Coordination Chemistry
• Organometallic Chemistry
• Polymerization Catalysis

Background:

• Schiff base macrocycles are versatile ligands in coordination chemistry.
• Dizinc complexes are of interest for catalytic applications.
• Ring-opening polymerization (ROP) is a key method for polymer synthesis.

Purpose of the Study:

• To synthesize and characterize novel dizinc(II) complexes with a macrocyclic Schiff base ligand.
• To investigate the catalytic activity of these complexes in lactide ring-opening polymerization.
• To explore the reactivity of the dizinc complexes with carbon dioxide.

Main Methods:

• Synthesis of dizinc(II) complexes via reaction of a macrocyclic Schiff base ligand with diethylzinc and isopropyl alcohol.
• Characterization using NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction.
• Investigation of catalytic activity in lactide ROP and reaction with CO2.

Main Results:

• Three new dizinc(II) complexes ([L(Et)Zn2Et2], [L(Et)Zn2((i)PrO)2], and dizinc carbonate species) were successfully synthesized and characterized.
• Complex 1 initiated racemic lactide polymerization with moderate activity and good control.
• The initiating system was inactive for CO2/cyclohexene oxide copolymerization, but complex 2 reacted reversibly with CO2 to form dizinc carbonates.

Conclusions:

• The synthesized dizinc(II) complexes exhibit distinct reactivity profiles.
• The complexes show potential as initiators for controlled lactide polymerization.
• The reversible reaction with CO2 highlights the potential for carbon capture or functionalization applications.