The influence of phenylsilane on the syndiotactic polymerization of styrene with η5-pentamethylcyclopentadienyl titanium trifluoride

The syndiotactic polystyrene polymerization activity of a fluorinated half‐sandwich complex, η5‐pentamethylcyclopentadienyl titanium trifluoride (Cp*TiF3), in the presence of relatively low amounts of methylalumoxane (MAO; MAO/Cp*TiF3 molar ratio = 200/1) and triisobutylaluminum, is significantly increased by the addition of phenylsilane in molar ratios to Cp*TiF3 ranging from about 300/1 to 600/1, if the phenylsilane is added to the monomer. Lower amounts of phenylsilane, such as a 100/1 molar ratio to Cp*TiF3, lead to a reduced polymerization activity in comparison with styrene without phenylsilane. A prereaction of phenylsilane with the catalyst mixture shows a behavior that is strongly dependent on the storage time of the composition and the temperature. A storage time of about 16 h is sufficient to reduce the polymerization conversion to about half of the original value. The results are discussed on the basis of a chain‐transfer reaction with phenylsilane and several catalyst complexes of different stabilities and activities, including an alkylation product of phenylsilane. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3476–3485, 2000 The syndiotactic polystyrene polymerization activity of a fluorinated half‐sandwich metallocene complex, η5‐pentamethylcyclopentadienyl titanium trifluoride, in the presence of relatively low amounts of methylalumoxane and triisobutylaluminum, is significantly increased by the addition of phenylsilane, if it is added to the monomer. Lower amounts of phenylsilane lead to a reduced polymerization activity in comparison with styrene without phenylsilane. A prereaction of phenylsilane with the catalyst mixture shows a different behavior that is strongly dependent on the storage time of the composition and the temperature. The results are discussed on the basis of a chain‐transfer reaction with phenylsilane and several catalyst complexes of different stabilities and activities, including an alkylation product of phenylsilane.