Biphasic ethylene oligomerization using bis(imino)pyridine cobalt complexes in methyl-butylimidazolium organochloroaluminate ionic liquids

Several bis(imino)pyridine cobalt (II) complexes have been synthesized and used in ethylene oligomerization in 1-methyl-3-butylimidazolium tetrachloroaluminate (BMI·AlCl4) ionic liquid activated by methylaluminoxane (MAO). The ligand substitution pattern, with halogen, methyl or trifluoromethyl units in the ortho- and para-positions of the aromatic group, has a marked effect on activity and selectivity. The cobalt catalysts evaluated in this work exhibited activities in the range 4000–15,300 h−1 and selectivities towards ethylene dimerization to butenes above 90%. These catalysts also exhibited high selectivity to 1-butene formation, up to 87%.

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► Bis(imino)pyridine cobalt (II) complexes were investigated for ethylene oligomerization immobilized in BMI·AlCl4.
► Cobalt catalyst showed moderate activity for ethylene oligomerization.
► Cobalt catalyst showed high selectivities for ethylene dimerization.
► Cobalt catalyst showed selectivities for 1-butene formation up to 87%.