Abstract

The catalytic system Ni(COD)2/ BF3·OEt2 was studied in the ethylene oligomerization. It was shown that in the absence of tertiary phosphines the system converted ethylene into dimers with a high selectivity to butene-1 (55%). It opens a way toward atom-economical ligand-free catalytic systems for oligomerization of low molecular weight olefins. The addition of tertiary phosphines made the system active even under the atmospheric pressure of ethylene increasing the selectivity to butene-1 up to 74%. On the basis of the ethylene product distribution and ESR data on the nickel species formed in the system a complete mechanism has been first proposed for the oligomerization of low molecular weight olefins in the catalytic nickel complex systems containing paramagnetic cationic nickel species. The proposed mechanism is based on the conventional key stages of catalytic reactions: metallocyclic ethylene oligomerization and cationic isomerisation of activated olefins which occur with the participation of Ni (I) and Ni (III) species.

Keywords: Monovalent nickel, Trivalent nickel, Polymerization, Oligomerization, Boron trifluoride, propylene dimerization, catalytic processes, phosphine, organophosphorus ligand, Tolman Cone angle, butene-1, olefins, Ni(III) organometallic complex, ESR signal, oligomer