Activation of Bis(phenoxyimino)zirconium Polymerization Catalysts with Methylaluminoxane and AlMe3/[CPh3]+[B(C6F5)4]-

The intermediates of olefin polymerization over homogeneous catalysts based on bis[ N -(3- tert -butylsalicylidene)anilinato]zirconium(IV) dichloride {(L t Bu ) 2 ZrCl 2 } ( 1- t Bu ), bis[ N -(3-methylsalicylidene)anilinato]zirconium(IV) dichloride {(L Me ) 2 ZrCl 2 } ( 1-Me ), and bis[ N -(salicylidene)anilinato]zirconium(IV) dichloride {(L H ) 2 ZrCl 2 } ( 1-H ) with different activators {methylaluminoxane (MAO) and AlMe 3 /[CPh 3 ] + [B(C 6 F 5 ) 4 ] - } have been studied by 1 H and 13 C NMR spectroscopy. Heterobinuclear ion pairs [(L t Bu ) 2 Zr(μ-Me) 2 AlMe 2 ] + [Me-MAO] - ( 2- t Bu ) and [(L t Bu ) 2 Zr(μ-Me) 2 AlMe 2 ] + [B(C 6 F 5 ) 4 ] - ( 2 ‘- t Bu ) are formed upon activation of 1- t Bu with MAO and AlMe 3 /[CPh 3 ] + [B(C 6 F 5 ) 4 ] -, respectively. These species are the precursors of the highly active intermediates of polymerization. In contrast, the activation of 1-Me with MAO results mainly in the formation of the tight ion pair [(L Me ) 2 ZrMe + ···Me-MAO - ]. This ion pair is the precursor to a poorly active intermediate of polymerization. In the catalytic systems 1-H /MAO and 1-H /AlMe 3 /[CPh 3 ] + [B(C 6 F 5 ) 4 ] -, the aluminum ion pairs [L H Al(μ-Me)(μ-Cl)AlMe 2 ] + [Me-MAO] - and [L H Al(μ-Me)(μ-Cl)AlMe 2 ] + [B(C 6 F 5 ) 4 ] -, which were inactive in ethylene polymerization, are predominantly formed. The isomeric composition of 2 ‘ - t Bu is close to that of the initial complex 1- t Bu . The main route of the 1- t Bu /MAO catalyst deactivation is the ligand transfer to aluminum with the formation of the complex L t Bu AlMe 2 .