Influence of π-ligand substitutions on the regiospecificity and stereospecificity in isospecific zirconocenes for propene polymerization.: A molecular mechanics analysis

被引：57

作者：

Toto, M

Cavallo, L

Corradini, P

Moscardi, G

Resconi, L

Guerra, G

机构：

[1] Univ Naples, Dipartimento Chim, I-80134 Naples, Italy

[2] G Natta Res Ctr, Montell Polyolefins, I-44100 Ferrara, Italy

[3] Univ Salerno, Dipartimento Chim, I-84081 Baronissi, Salerno, Italy

来源：

MACROMOLECULES | 1998年 / 31卷 / 11期

关键词：

D O I：

10.1021/ma980238w

中图分类号：

O63 [高分子化学（高聚物）];

学科分类号：

070305 ; 080501 ; 081704 ;

摘要：

A possible rationalization of the dependence of regiospecificity of propene polymerization for catalytic systems based on C-2-symmetric ansa-zirconocenes (and hafnocenes) on the pi-ligand alkyl substitutions is presented. With this aim, models of preinsertion intermediates and transition states for primary and secondary monomer insertion reactions are compared through molecular mechanics analyses. The nonbonded energy contributions to the regioselectivity, as well as the enantioselectivities of regioregular and regioirregular insertion steps have been investigated. Nonbonded energy interactions are able to account for the increases of regiospecificity experimentally observed for zirconocene-based catalytic systems when the pi-ligands are alkyl substituted in position 2 or 3 as well as the decrease of regiospecificity observed when the pi-ligands are dimethyl substituted in positions 4 and 7.

引用

页码：3431 / 3438

页数：8

共 82 条

[41] POLYMERIZATION OF PROPENE AND BUTENE WITH A CHIRAL ZIRCONOCENE AND METHYLALUMOXANE AS COCATALYST [J].