Olefin oligomerization by novel catalysts prepared by oxidative addition of carboxylic acids to nickel(0) precursors and modified by phosphine ancillary ligands and organoaluminum compounds

Novel Ziegler-Natta-type catalysts, prepared in situ by oxidative addition of carboxylic acids to bis(cyclooctadiene)nickel(0) [Ni(cod)(2)]/phosphine adducts and activated by different organoaluminum compounds, are described. These catalysts resulted very active in olefin oligomerization. When 2-nit robenzoic acid (NBA), tricyclohexylphosphine (PCy3) and MAO were employed i n combination with Ni(cod)(2) for propylene oligomerization. a regioselecti vity to 2,3-dimethylbutenes (DMB) within the C-6 cut very close to 90% was achieved with a high productivity (turnover frequency (TOF) values up to 16 ,400 h(-1)). Similar results in terms of regioselectivity to DMB were obtai ned when trifluoroacetic acid (TFA) was adopted. However, although with a l ower productivity, a higher value of overall yield to DMB (62.7%) was achie ved. When these catalysts were used for ethylene oligomerization they resul ted very active (TOF values up to 65,000 h(-1)). the nature of the phosphin e ligand allowing to strongly affect the chemoselectivity of the process, s hifting the oligomeric composition towards specific fractions. (C) 2001 Els evier Science B.V. All rights reserved.