Catalytic performances of homogeneous systems based on alpha-nitroacetophenonate-nickel(II) complexes and organoaluminium compounds in ethylene oligomerisation

The catalytic behaviour of novel alpha -nitroacetophenonate-nickel(II) comp lexes has been investigated as a function of reaction conditions, type and relative amount of the organoaluminium co-catalyst, as well as nature of th e ancillary phosphine ligand, in order to orientate ethylene oligomerisatio n process towards specific target products. The reported data allowed to in dicate that it is possible to shift the products distribution towards highe r oligomers by increasing the Lewis acidity of the organoaluminium co-catal yst and by using a basic and bulky ancillary ligand such as tricyclohexylph osphine (PCy3). The catalyst productivity may be also readily modulated by choosing the proper organoaluminium co-catalyst and the suitable phosphine ancillary ligand. Under proper reaction conditions, a very high linearity ( more than 80% of n-hexenes) of the C-6 cut was obtained. On the other side, the mixture of the higher oligomeric components was found to have a relati vely high degree of branching. This is likely due to the ability of the cat alytic system to co-oligomerise ethylene with the produced dimeric and trim eric alpha -olefins, thus, affording more branched higher oligomers. (C) 20 01 Elsevier Science B.V. All rights reserved.