Effect of trimethylaluminum on the formation of active sites of the catalytic system bis[N-(3,5-di-tert-butylsalicylidene)-2,3,5,6-tetrafluoroanilinato]titanium(IV) dichloride—MAO and catalytic isomerization of hex-1-ene

The transformations of bis[ N -(3,5-di- tert -butylsalicylidene)-2,3,5,6-tetrafluoroanilinato]-titanium( iv ) dichloride (L 2 TiCl 2 ) occurring in toluene under the action of methylalumoxane (MAO) were studied by 1 H NMR spectroscopy. The commercially available MAO containing trimethylaluminum (AlMe 3 ) and MAO free of AlMe 3 (the so called “dry” MAO) were used. The catalytic transformations of hex-1-ene involving the systems L 2 TiCl 2 -MAO were studied. We proposed the structures of the cationic titanium complexes formed in the absence and in the presence of hex-1-ene under the action of MAO. In the absence of olefin, neutral and cationic titanium complexes are decomposed under the action of AlMe 3 according to the exchange reaction of the complex ligand with the methyl groups of AlMe 3 to form LAlMe 2 . The neutral complexes react considerably faster than the cationic ones. In the presence of olefin, decomposition of complexes under the action of AlMe 3 is suppressed. The titanium complex activated by “dry” MAO isomerizes hex-1-ene to hex-2-ene. In the presence of large amounts of TMA (commercial MAO), this reaction does not take place.