New Coordination Modes for Modified Schiff Base Ti(IV) Complexes and Their Control over Lactone Ring-Opening...

Area of Science:

• Coordination Chemistry
• Polymer Chemistry
• Organometallic Catalysis

Background:

• Schiff base ligands are versatile in coordination chemistry.
• Titanium(IV) complexes are explored for polymerization catalysis.
• Controlling catalyst structure is key to optimizing polymerization.

Purpose of the Study:

• To synthesize and characterize novel bis(alkoxy)bis(phenoxy-imine)titanium(IV) catalysts.
• To investigate the influence of ligand coordination modes on catalyst structure.
• To evaluate the catalytic activity and control in ring-opening polymerization.

Main Methods:

• Synthesis of titanium(IV) complexes using Schiff base ligands derived from o-vanillin.
• Characterization using variable temperature NMR spectroscopy and X-ray crystallography.
• Ring-opening polymerization of ε-caprolactone and ω-pentadecalactone.

Main Results:

• Eight new titanium(IV) catalysts were successfully prepared.
• Ligands adopted N-O and/or O-O coordination modes, leading to three complex structures (Type A, B, C).
• Catalytic activity decreased in the order Type C > Type B > Type A for both monomers.

Conclusions:

• The coordination mode of Schiff base ligands significantly impacts titanium(IV) catalyst structure.
• Catalyst structure directly influences polymerization rate, with O-O:O-O coordination showing highest activity.
• This work highlights the potential for tuning catalyst performance through ligand design.