Al and Zn phenoxy-amidine complexes for lactide ROP catalysis

Area of Science:

• Organometallic Chemistry
• Polymer Chemistry
• Ligand Design

Background:

• Phenoxy-amidine ligands offer versatile coordination possibilities.
• Aluminum and zinc complexes are widely explored for catalysis.
• Ring-opening polymerization (ROP) is crucial for biodegradable polymer synthesis.

Purpose of the Study:

• To synthesize and characterize a new generation of phenoxy-amidine ligands.
• To investigate the coordination chemistry of these ligands with aluminum and zinc.
• To evaluate the catalytic activity of the resulting complexes in the ROP of rac-lactide.

Main Methods:

• Synthesis of phenol-amidine proligands and their metal complexes.
• X-ray diffraction analysis for solid-state structure determination.
• DOSY NMR spectroscopy to study solution behavior.
• Catalytic testing for ROP of rac-lactide under various conditions.

Main Results:

• Mono- and bis-ligated Al and Zn complexes were successfully synthesized.
• Solid-state structures revealed dimeric arrangements for mono-ligated complexes.
• Solution studies indicated differences in structural retention between Al and Zn complexes.
• Fluxional behavior was observed in bis(ligated) complexes.
• Zinc complexes with pendant dimethylamino arms exhibited superior catalytic activity in ROP.

Conclusions:

• The developed phenoxy-amidine ligands form stable complexes with Al and Zn.
• Structural dynamics in solution influence catalytic performance.
• Zn-based phenoxy-amidine complexes are highly effective catalysts for rac-lactide ROP, particularly those with appended amino groups.