Cationic η3-benzyl nickel compounds with diphosphine ligands as catalyst precursors for ethylene oligomerization/polymerization:: influence of the diphosphine bite angle

The oligomerization and/or polymerization of ethylene catalyzed by the cationic eta(3)-benzylcomplexes [Ni(eta(3)-CH2C6H4-p-CF3)(P-P)](+) BPh4- (P-P = (Pr2P)-Pr-i(CH2)(n)(PPr2)-Pr-i, n = 1-3) have been studied. The activity of these single component catalysts depends on the length of the (CH2)(n) bridge of the diphosphine ligand. Thus, the dippm derivative (n = 1) displays higher activity than compounds of the dippe (n = 2) or dippp (n = 3) ligands. The molecular weight of the products is also a function of n, and varies in the order dippin > dippe > dippp, with the former two catalysts giving rise to low molecular weight polyethylenes and the latter to oligomers. (C) 2003 Elsevier B.V. All rights reserved.