Modified Half-Titanocenes as Polymerization Catalysts: Basic Concept, Displayed Promising Characteristics and Some Mechanistic Insights

Development of new polymers that cannot be achieved by using conventional catalysts has been the central research objective, and copolymerization is an effective strategy to modify the materials’ (thermal, physical, mechanical and electronic) properties. Modified half-titanocenes, Cp’TiX2(Y) (Cp’ = cyclopentadienyl, X = Cl, Me, etc, Y = anionic donor such as phenoxide, ketimide, amidinate, etc.), are known to be effective catalysts. This review introduces several selected efforts for efficient synthesis of ethylene copolymers containing cyclic olefins, biobased conjugated dienes, and disubstituted α-olefins, including the effect of cocatalysts. Moreover, here we introduce an analysis using XAS (X-ray absorption spectroscopy), which has been recognized as a powerful method providing direct information on the catalytically active species, such as coordination numbers and the distances of the coordinated atoms as well as oxidation state and the geometry of the metal centre in catalyst solution.