Stereoselectivity and Chemoselectivity in Ziegler−Natta Polymerizations of Conjugated Dienes. 1. Monomers with Low-Energy s-Cis η4 Coordination§
Stereoselectivity and Chemoselectivity in Ziegler−Natta Polymerizations of Conjugated Dienes. 1. Monomers with Low-Energy s-Cis η4 Coordination§
复制标题
DOI：
10.1021/ma010673h
复制
发表时间：
2001-10
期刊：
影响因子：
5.5
通讯作者：
C. Costabile;G. Milano;L. Cavallo;G. Guerra
中科院分区：
文献类型：
--
作者：
C. Costabile;G. Milano;L. Cavallo;G. Guerra
The mechanisms of stereoselectivity and chemoselectivity in the Ziegler−Natta polymerizations of conjugated dienes have been investigated by density functional methods, in the framework of the widely accepted polymerization scheme involving anti-allyl coordination of the growing chain. Most insertions would occur through intermediates with the diene monomer s-cis η4 coordinated to the metal and with the monomer concavity oriented toward the terminal allyl group of the growing chain. Monomer coordinated intermediates presenting a backbiting of the anti-allyl coordinated growing chain (η3η2) would essentially lead to 1,4-unlike insertions only, while monomer coordinated intermediates simply presenting an anti-allyl coordination of the growing chain would lead to 1,4-like and/or 1,2-unlike insertions. These models are able to rationalize several experimental data relative to stereoselectivity and chemoselectivity in Ziegler−Natta polymerizations of conjugated dienes.
