Recent research progress in influence of the ansa-zirconcene catalytic system on the polypropylene microstructure

Abstract

Abstract-In this paper, the recent development of ansa-zirconcene catalysts and their co-catalysts, the relationship between the structure of ansa-zirconcene catalytic system and the microstructure of the resultant polypropylene are reviewed. The forming mechanisms of resultant polypropylene microstructure are discussed in view of ansa-zirconcene catalyst structure and their co-catalyst structure.

Catalytic Properties of Zirconocene-Based Systems in 1-Hexene Oligomerization and Structure of Metal Hydride Reaction Centers

“…Probably, the stereocontrol may be carried out not only by the ligand on the transition metal atom (site control) or the growing chain (chain control), but also by the activator residing in the active centre and determining its structure and dynamics along with other factors. As stated earlier [12], the complete separation of cationanion pair can increase the activity of the system, but lead to the loss of stereoselectivity. Strong cationanion interactions could minimize the epimerization of the last inserted molecule, thereby increasing stereoselectivity, but at the same time cause a decrease in activity as a result of monomer coordination hinderance.…”

“…They most efficiently ensure the stability of electronic and steric environment of transition metal atom due to the high energy of metal-ligand bond and vary the electrophilicity and geometry of catalytically active centers due to the large structural modification possibilities of π-ligand. Thus, it has been shown that the electronic and steric factor of the ligand, the nature of the activator, and the reaction conditions [8][9][10][11][12][13][14][15] determine the productivity and selectivity of catalytic systems.…”

Catalytic Properties of Zirconocene-Based Systems in 1-Hexene Oligomerization and Structure of Metal Hydride Reaction Centers

“…Probably, the stereocontrol may be provided by not only the ligand on the transition metal atom (site control) or the growing chain (chain control) but also the activator occurring as a part of the active site and determining its structure and dynamics on an equal basis with other factors. As stated earlier [ 12 ], the complete separation of the cation–anion pair may increase the activity of the system but may lead to the loss of stereoselectivity. Strong cation–anion interactions could minimize the epimerization of the last inserted unit and thus increase the stereoselectivity, but at the same time, they cause a decrease in the activity by hampering the monomer insertion.…”

“…They provide the most efficient stabilization of the electronic and steric environment of transition metal atoms owing to the high energy of metal–ligand bonds and allow variation of the electrophilicity and geometry of catalytically active sites due to broad possibilities of π-ligand modification. It has been shown that the electronic and steric features of the ligand, the nature of the activator, and the reaction conditions [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ] determine the productivity and selectivity of catalytic systems.…”