Probing the Validity of the −CH2SiMe3 Group as a Model of the Growing Chain in Mechanistic Studies of Olefin Polymerization with Group 4 Catalysts

• Published in: Organometallics 2006-03, Vol.25 (6), p.1431-1433
• Main Authors: Ducéré, Jean-Marie, Cavallo, Luigi
• Format: Article
• Language: English
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om051019j

Using a DFT approach we investigated the geometry and the stability of cationic bisindenyl zirconocenes paired up with a counterion and of general formula [rac-Me2Si(1-Ind)2ZrR]+/[MeB(C6F5)3]- and [rac-Me2Si(1-Ind)2ZrR]+/[B(C6F5)4]-, R = −CH2SiMe3 or −CH2CHMe2 groups. The two R groups are differently agostic-bonded to the metal. The calculations evidence rather good similarity when systems bearing the two different R groups are compared in terms of geometry, relative energies, and the ion-pair separation energies. They validate to a large extent the −CH2SiMe3 group as a model of the growing chain in catalytic olefin polymerizations. However, they also underline some geometric differences that should be considered when mechanistic schemes are developed from experiments.