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 addit ion 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-dime thylbutenes (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 promo ters was also checked. The results indicated that the catalysts prepared by this route were more active and selective towards DMB as compared with tho se previously prepared by an exchange reaction method. When basic alkyl pho sphines, 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 s electivity to DMB (similar to 80%) and an extremely high productivity (turn over frequency equal to 74,000 h(-1)), the latter being much higher as comp ared with that previously obtained with the homogeneous counterparts. (C) 2 001 Elsevier Science B.V. All rights reserved.