Selective two-phase catalytic ethylene dimerization by Ni-II complexes/AlEtCl(2) dissolved in organoaluminate ionic liquids

Nickel(II) complexes dissolved in methyl-1-butyl-3-imidazolium chloride/AlCl3 molten salt in the presence of AlEtCl(2) and aromatic solvents catalyse the dimerization of ethylene into butenes in a typical two-phase catalytic reaction. The nature of the nickel catalyst precursor has a strong influence on the reaction's activity and selectivity. Thus, ethylene dimers and trimers were obtained in the presence of NiF2 and NiCl2(PCy(3))(2), whereas only butenes were formed using the complex [Ni(MeCN)(6)] [BF4](2) as a catalyst precursor. In this latter case but-1-ene was formed with a selectivity of 83% and turnover frequencies of up to 1731 h(-1). Moreover, the conversion and selectivity to but-1-ene increase with increasing ethylene pressure. The use of aromatic co-solvents is also essential for the ethylene dimerization, since other hydrocarbons induce the formation of higher ethylene oligomers. Copyright (C) 1996 Elsevier Science Ltd