Possible thermal decomposition routes in [MeB(C6F5)(3)](-)[L2TiMe+] as deactivation pathways in olefin polymerization catalysis: A combined density functional theory and molecular mechanics investigation

摘要

Combined quantum mechanical (QM) and molecular mechanical (MM) models (QM/MM) have been used to explore possible decomposition routes for ion pair systems used as catalysts in olefin polymerization. The catalyst systems include [MeB(C6F5)(3)](-)[(NPR3)(2)TiMe+], [MeB(C6F5)(3)](-)[(Cp)(NCR2)TiMe+], and [MeB(C6F5)(3)](-)[(Cp)(SiMe2NR)TiMe+]. The possible thermal decomposition routes for the above catalyst systems include fluorine transfer from [MeB(C6F5)(3)](-) to the metal center, aryl transfer (C6F5) to the growing chain, transfer of B(C6F5)(3) from [MeB(C6F5)(3)](-) to the ancillary ligand, exchange of methyl on butyl from the ancillary ligand with aryl in [MeB(C6F5)(3)](-), transfer of hydrogen from the Cp* ring to the growing chain, and transfer of hydrogen from the methyl group on tertiary butyl to the growing chain. The activation barriers fall in the range 15.5-68.7 kcal/mol. The transfer of fluorine from the counterion to the metal center is the most facile deactivation pathway.