Nonbridged Half-titanocenes Modified with Anionic Ancillary Donor Ligands as Efficient Catalysts for Olefin Polymerization

Nonbridged half-titanocene catalysts containing anionic donor ligands, Cp’TiX2(Y) (Cp’ = cyclopentadienyl; X = halogen, alkyl; Y = anionic ancillary donor such as phenoxide, ketimide etc.), display unique characteristics as catalysts for synthesis of new polyolefins, especially ethylene copolymers with sterically encumbered olefins (branched α-olefins, disubstituted olefins), cyclic olefins, aromatic vinyl monomers, biobased conjugated dienes, and α-olefins containing hydroxy group. This perspective introduces historical background for the catalyst design, basic concept of the present catalysts, efforts for synthesis of new polymers and some mechanistic studies. Various new polymers exhibiting promising properties have been demonstrated by development of these catalysts, synthetic methodologies.