III International Conference

ACTIVATION OF POST-TITANOCENE OLEFIN POLYMERIZATIONCATALYSTS WITH METHYLALUMINOXANE: THE INTERMEDIATESPP-II-17Bryliakov K.P., Talsi E.P., Kravtsov E.A., Semikolenova N.V., Zakharov V.A.,Bochmann M. 1Boreskov Institute of Catalysis SB RAS, Novosibirsk, Russia1 Wolfson Materials and Catalysis Centre, School of Chemical Sciences and Pharmacy,University of East Anglia, NR4 7TJ Norwich, UKE-mail: bryliako@catalysis.ruCationic intermediates formed upon activation of post-titanocene(IV) olefinpolymerization catalysts (bis(salicylaldimine), or bis(phenoxy-imine), (FI) 2 TiCl 2 , bis(pyrroleimine)(PI) 2 TiCl 2 , and mixed-ligand (salicylaldimine)(pyrole-imine) (FI)(PI)TiCl 2 ) with MAOand AlMe 3 /CPh 3 + B(C 6 F 5 ) 4 − with MAO or AlMe 3 /CPh 3 + B(C 6 F 5 ) 4 − have been detected andcharacterized by 1 H, 13 C, 19 F NMR.Metallocene and post-metallocene based single site olefin polymerization is one of themost exciting achievements in the field of catalysis in recent years. For the active catalysts toform, the starting complexes must be activated by Lewis acidic co-catalysts such asmethylaluminoxane (MAO), B(C 6 F 5 ) 3 or [CPh 3 ][B(C 6 F 5 ) 4 ], MAO remaining the most widelyused co-catalyst for metallocene and post-metallocene based catalysts.It was found that the interaction of MAO with post-titanocene complexes (FI) 2 TiCl 2[1], (PI) 2 TiCl 2 , (FI)(PI)TiCl 2 [2] resulted in the formation of outer-sphere ion pairs of thetype [LL’TiMe(S)]+[Me-MAO]− (where S stands for a solvent molecule) which are theprecursors of the real polymerizing species. In the first system (FI) 2 TiCl 2 /MAO (and(FI) 2 TiCl 2 /[CPh 3 ][B(C 6 F 5 ) 4 ]/AlMe 3 ) capable of conducting living olefin polymerization,the true intermediates [(FI) 2 TiP]+[Me-MAO]− (and [(FI) 2 TiP]+[B(C 6 F 5 ) 4 ]−) weredetected (P= growing polymeryl chain) [1]. It was found that the main deactivationpathways for the (FI) 2 TiCl 2 /MAO system are the salicylaldimine ligand transfer toaluminium, as well as reduction to titanium(III). The (PI) 2 TiCl 2 /MAO system deactivatesmainly via ligand transfer, whereas for the mixed-ligand system (FI)(PI)TiCl 2 /MAO,reduction to titanium(III) prevails [2].Correlation between the structures and stabilities of the intermediates and theirreactivities in olefin polymerisation are discussed and compared with those established for193