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Controlling the Microstructure of Isotactic Polypropene by C 2 ‐Symmetric Zirconocene Polymerization Catalysts: Influence of Alkyl Substituents on Regio‐ and Stereocontrol
Author(s) -
Kuklin Mikhail S.,
Virkkunen Ville,
Castro Pascal M.,
Resconi Luigi,
Linnolahti Mikko
Publication year - 2015
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201500862
Subject(s) - tacticity , chemistry , alkyl , stereospecificity , propene , ligand (biochemistry) , catalysis , polymerization , medicinal chemistry , polymer chemistry , stereochemistry , organic chemistry , polymer , biochemistry , receptor
A combined computational and experimental study was carried out to evaluate control of the microstructure of isotactic polypropene by C 2 ‐symmetric zirconocenes with rac ‐SiMe 2 [Ind] 2 ‐based ligands. Building on the highly regio‐ and stereospecific catalyst combining 2‐Me and 4‐Ph substituents, we made further modifications to the ligand framework by systematic addition of alkyl substituents. Propene insertion barriers are given for a total of 24 catalysts. Calculations and experiments show that the series of catalysts produce highly stereoregular isotactic polypropene. Regiocontrol can be markedly improved by addition of 3‐Me substituents or by replacing 2‐Me with bulkier 2‐alkyl substituents on the indenyl ligand, but the former is accompanied by loss of stereocontrol and the latter by significantly increased overall barriers for propene insertion. The combination of methyl substituents and t Bu groups on the 4‐Ph ligand substituents is shown to provide improved regiocontrol without sacrificing high stereocontrol.