Styrene Polymerization by Monocyclopentadienyl Titanium(III) Complexes: A DFT Study. The Effect of Counterion on the Kinetics and Mechanism of the Process

Abstract

The effect of counterion on the kinetics and the mechanism of styrene polymerization by monocyclopentadienyl titanium(III) complexes was examined using the DFT approach. A comparative study of three model catalytic species, namely, CpTiIIICH2Ph+ and two ion pairs of composition CpTiIIICH2Ph+A- (A- = CH3B(C6F5)3-, B(C6F5)4-), was carried out. Two possible pathways (I and II) of the interaction were examined and compared. It was shown that the nature of the counterion affects the thermodynamic characteristics of styrene addition to the CpTiCH2Ph+A- ion pairs. The weaker the nucleophilicity of the counterion, the higher the exothermicity of styrene addition to CpTiCH2Ph+A-. Intramolecular formation of the C−C bond in the CpTi(CH2CHPh)CH2Ph+A- adduct is characterized by the highest energy on the reaction pathway. This step is the rate-determining stage of the overall reaction.