Improved heterogenized catalysts for selective propylene oligomerization to 2,3-dimethylbutenes prepared by oxidative addition of polymer-anchored beta-dithioacetylacetonate ligands to nickel(0) complexes

A novel approach for obtaining heterogenized catalysts, via oxidative addition of polymer-bound beta -dithioacetylacetonate (sacsac) ligands to nickel(0) complexes was reported and their performances were investigated in the propylene oligomerization, in terms of activity and selectivity to 2,3-dimethylbutenes (DMB). In particular, the effect of the nature of the ancillary phosphine ligand as well as of the organoaluminium co-catalyst was studied. The influence of the addition to the reaction medium of chlorinated promoters was also checked. The results indicated that the catalysts prepared by this route were more active and selective towards DMB as compared with those previously prepared by an exchange reaction method. When basic alkyl phosphines, such as tricyclohexylphosphine (PCy3) and triisopropylphosphine ((PPr3)-Pr-i), and organoaluminium co-catalysts with suitable Lewis acidity, such as Et2AlCl, were used, the resulting catalysts displayed a very high selectivity to DMB (similar to 80%) and an extremely high productivity (turnover frequency equal to 74,000 h(-1)), the latter being much higher as compared with that previously obtained with the homogeneous counterparts. (C) 2001 Elsevier Science B.V. All rights reserved.