Ethylene oligomerization reactions catalyzed by homogeneous and silica immobilized NˆO Fe(II) and Co(II) complexes

Abstract

Treatment of 2-phenyl-2-((3(triethoxysilyl)propyl)imino)ethanol (L1) and 4-nitro-2-((3(triethoxysilyl)propyl)imino)methyl)phenol (L2) with MCM-41 support afforded the respective immobilized ligands (L1im) and (L2im). Reactions of synthons L1, L2, L1im and L2im with either FeCl2·4H2O or CoCl2 led to the formation of their respective homogeneous and immobilized metal complexes [Fe(L1)2] (Fe1), [Co(L1)2] (Co1), [Fe(L2)2] (Fe2), [Co(L2)2] (Co2), [Fe(L1im)2] (Fe1im), [Co(L1im)2] (Co1im), [Fe(L2im)2] (Fe2im), and [Co(L2im)2] (Co2im). The compounds were characterized by FT-IR, NMR, ESI-MS, SEM-EDX and elemental analysis. Activation of the Fe(II) and Co(II) complexes with EtAlCl2, resulted in active catalysts for the tandem ethylene dimerization and Friedel-Crafts alkylation of the toluene solvent to produce mainly alkyltoluenes. On the other hand, the use of chlorobenzene solvent and MAO co-catalyst led to the formation of mainly butenes. Generally, the immobilized catalysts exhibited lower catalytic activities, but with comparable selectivity to the homogeneous catalysts. Recycling studies established that the immobilized catalysts were active for three runs without loss of selectivity.