Imidazolin-2-iminato titanium complexes: synthesis, structure and use in ethylene polymerization catalysis

Area of Science:

• Organometallic Chemistry
• Polymer Chemistry
• Catalysis

Background:

• Imidazolin-2-ylidenes are versatile ligands in organometallic chemistry.
• Titanium complexes are widely studied for olefin polymerization.

Purpose of the Study:

• To synthesize novel half-sandwich and bis-ligand titanium complexes with imidazolin-2-iminato ligands.
• To evaluate the catalytic activity of these complexes in ethylene homopolymerization.

Main Methods:

• Staudinger reaction to synthesize N-silylated iminoimidazolines.
• Reaction of iminoimidazolines with titanium precursors (CpTiCl3, Cp*TiCl3, TiCl4).
• Ethylene polymerization using methylaluminoxane (MAO) as activator.

Main Results:

• Synthesis of various half-sandwich [CpTi(L)Cl2] and [Cp*Ti(L)Cl2] complexes, and bis-ligand complexes [L2TiCl2].
• Structural characterization revealing linear coordination and short Ti-N bonds.
• Catalytic evaluation showed moderate to high activities for ethylene homopolymerization, yielding high and ultra-high molecular weight polyethylene (HMWPE/UHMWPE).

Conclusions:

• Imidazolin-2-iminato titanium complexes are effective catalysts for producing high molecular weight polyethylene.
• The ligand structure and titanium complex type influence catalytic performance.