Cationic eta-3 -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 ?3-benzylcomplexes [Ni(?3-CH2C6H4-p-CF3)(P-P)]+ BPh4- (P-P=iPr2P(CH2)nPiPr2, 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 dippm > dippe > dippp, with the former two catalysts giving rise to low molecular weight polyethylenes and the latter to oligomers.