Early and Late Transition Metal Catalysts for Olefin Polymerization

Recent scientific developments on catalysts used in olefin polymerizations can be regarded as a good sign of successful applications of organometallic chemistry in homogenous polymerization. Early and late transition metal catalysts (LTM) are a new groups of coordination polymerizations catalysts which were discovered in 1998. The LTM catalysts are based on late metals of group IV of transition metal including Fe, Ni, Co, and etc. At the same time, another category of early transition metal catalysts based on phenoxy ligand was discovered by Fujita and his colleagues in Mitsui for olefin polymerization. The major disadvantage of this type of catalytic systems is their higher rate of chain transfer reactions when compared with Ziegler-Natta and metallocene catalysts; therefore these catalysts may produce oligomers. However, due to a special isomerization reaction, called chain walking, these catalysts have some interesting features for application in polymer technology. One of the interesting properties of LTM catalysts is their ability of using polar monomer in olefin polymerization.