ABSTRACT 

The oligomerization of alkenes has been performed with Ni(MeCN₆)(BF₄)₂ associated with AlEt₂Cl or AlEt₃ as cocatalysts under different catalytic conditions: in homogeneous phase, under biphasic conditions (immobilized in ionic liquids) or heterogeneized in zeolite. Ni(MeCN₆)(BF₄)₂ in homogeneous phase shows high activity (TOF = 2451 h^-1) and selectivity to C₄ products (97%) with 30% of 1-butene under mild reaction conditions (10 bar, 50°C). Ni(MeCN₆)(BF₄)₂ dissolved in 1-methyl-3-butyl-imidazolium chloride/AlCl₃/AlEtCl₂ ionic liquids catalyses ethylene dimerization with a selectivity that can attain 83% in 1-butene and Ni(MeCN₆)(BF₄)₂ immobilized in zeolite (NaX) exhibit selectivities in 1-butene of 78 %. The behavior of the same complex [Ni(MeCN₆)(BF₄)₂] acting under these different catalytic reaction conditions (homogeneous, biphasic and heterogeneous) is compared and discussed. The active species and the mechanism for ethylene dimerization are proposed and discussed based on concerned characterization studies.