Enhanced Reactivity of Aluminum Complexes Containing P-Bridged Biphenolate Ligands in Ring-Opening Polymerization...

Area of Science:

• Organometallic Chemistry
• Polymer Chemistry
• Catalysis

Background:

• Aluminum complexes are increasingly investigated as catalysts for polymerization reactions.
• Biphenolate ligands offer tunable steric and electronic properties for metal complexes.
• Ring-opening polymerization (ROP) is a key method for synthesizing biodegradable polymers.

Purpose of the Study:

• To synthesize and characterize novel aluminum complexes featuring biphenolate ligands.
• To evaluate the catalytic activity of these complexes in the ring-opening polymerization (ROP) of ε-caprolactone and rac-lactide (rac-LA).
• To investigate the influence of ligand substituents on catalytic performance and polymerization control.

Main Methods:

• Synthesis of aluminum complexes with [RP(O)(2-O-3,5-tBu2C6H2)2]2- and [RP(2-O-3,5-tBu2C6H2)2]2- ligands, where R = tBu or Ph.
• Structural characterization of the synthesized aluminum complexes.
• Catalytic testing of methyl and benzyloxide aluminum complexes in ROP of ε-caprolactone and rac-LA.
• Kinetic studies to determine reaction rates and polymerization mechanisms.

Main Results:

• Novel aluminum complexes [3a-b]AlMe and {[3a-b]Al(μ2-OCH2Ph)}2 were successfully synthesized and characterized.
• Both methyl and benzyloxide aluminum complexes demonstrated activity in the ROP of ε-caprolactone and rac-LA.
• The complex {[3a]Al(μ2-OCH2Ph)}2 exhibited living polymerization behavior.
• Kinetic studies revealed that the P-substituents on the biphenolate ligand significantly impact ROP catalytic rates, with [3a]AlMe showing superior activity.

Conclusions:

• The synthesized aluminum biphenolate complexes are effective catalysts for ROP.
• Tuning the P-substituents on the biphenolate ligand allows for control over catalytic activity and polymerization characteristics.
• These findings highlight the potential of tailored aluminum complexes for controlled polymer synthesis.