Key Elements in the Structure and Function Relationship of the MgCl2/TiCl4/Lewis Base Ziegler-Natta Catalytic System

详细信息    查看全文

• 作者：Andrea Correa ; Fabrizio Piemontesi ; Giampiero Morini ; Luigi Cavallo
• 刊名：Macromolecules
• 出版年：2007
• 出版时间：December 11, 2007
• 年：2007
• 卷：40
• 期：25
• 页码：9181 - 9189
• 全文大小：511K
• 年卷期：v.40,no.25(December 11, 2007)
• ISSN：1520-5835

文摘

We present a theoretical study of the basic interactions occurring at supported hetereogenousZiegler-Natta catalytic systems. We first investigated the interaction between prototypes of each class of industriallyrelevant internal donors (1,3-diethers, alkoxysilanes, phthalates, succinates) and the MgCl₂ support. Our analysisindicates that donors can be separated into two classes. 1,3-Diethers and alkoxysilanes belong to the formerbecause they have a short spacer between the coordinating O atoms and coordinate preferentially to the same Mgatom of the (110) lateral cut. Conversely, phthalates and succinates belong to the latter class because they havea longer spacer between the coordinating O atoms and thus can adopt a variety of coordination modes. Indeed,they can coordinate to both the (100) and (110) lateral cuts. In the last part of this manuscript we report on thestereo- and regioselective behavior of possible active Ti species with and without two succinate moleculescoordinated in the proximity of the Ti atom. We show that the two succinate molecules confer a remarkablestereoselectivity in both primary and secondary propene insertions. This model very simply rationalizes the effectof the donors, and it is consistent with the models so far developed to rationalize the stereoselectivity of metalloceneand octahedral nonmetallocene catalysts.