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 (L2TiCl2) occurring in toluene under the action of methylalumoxane (MAO) were studied by 1H NMR spectroscopy. The commercially available MAO containing trimethylaluminum (AlMe3) and MAO free of AlMe3 (the so called “dry” MAO) were used. The catalytic transformations of hex-1-ene involving the systems L2TiCl2-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 AlMe3 according to the exchange reaction of the complex ligand with the methyl groups of AlMe3 to form LAlMe2. The neutral complexes react considerably faster than the cationic ones. In the presence of olefin, decomposition of complexes under the action of AlMe3 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.