I. Tritto et al., TITANOCENE-METHYLALUMINOXANE CATALYSTS FOR OLEFIN POLYMERIZATION - A C-13 NMR-STUDY OF THE REACTION EQUILIBRIA AND POLYMERIZATION, Macromolecules, 28(15), 1995, pp. 5358-5362
The olefin polymerization catalyst based on Cp(2)Ti(13)CH(3)Cl/MAO has
been studied. Reaction equilibria and polymerization of C-13-enriched
ethylene were followed by C-13 NMR spectroscopy, and the catalytic ac
tivity was determined. Evidence has been obtained that MAO alkylates t
he transition metal and produces stable cationlike species Cp(2)TiMe()Cl .[Al(Me)O](-)(n) (3). Complex 3 has been shown to be active for ol
efin polymerization. Two types of ion pairs have been detected for the
low Al/Mt ratios. We assume that they are more or less tight ion pair
s. It has also been possible to relate polymerization activity to the
composition of the catalyst mixture. Temperature (-78 divided by -20 d
egrees C), Al/Mt mole ratios (10 divided by 40), and catalyst dilution
have been shown to influence the concentration of active species such
as 3 and thus to affect polymerization activity. Dilution decreases t
he formation of nonactive species such as Cp(2)Ti(Me)-OAl(Me)-MAO (4).