Ethylene oligomerization reactions catalyzed by recyclable Fe(II), Ni(II) and Co(II) complexes immobilized on Fe3O4 magnetic nanoparticles

Abstract

• Fe 3 O 4 MNPs immobilized metal complexes synthesized and characterized • Activation with EtAlCl 2 afford active ethylene oligomerization catalysts • Butene and hexene oligomers major products in heptane • Immobilized complexes effectively recycled via magnetic separation • Recycled catalysts maintained both catalytic activity and selectivity. Reactions of Fe 3 O 4 magnetic nanoparticles supported ligands, phenol((triethoxysilyl)propylimino)ethyl ( L1@Fe 3 O 4 ) and phenol((triethoxysilyl)propylimino)methyl ( L2@Fe 3 O 4 ) with appropriate metal salts afforded the respective immobilized complexes Ni1@Fe 3 O 4 , Ni2@Fe 3 O 4 , Co1@Fe 3 O 4 , Co2@Fe 3 O 4 , Fe1@Fe 3 O 4 and Fe2@Fe 3 O 4 . The complexes were characterized using FT-IR spectroscopy, thermogravimetric analyses (TGA), transmission electron microscopy (TEM), scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), energy dispersive X-ray (EDX), inductively coupled plasma optical emission spectroscopy (ICP-OES) and vibrational sample magnetometry (VSM). Activation of the complexes with EtAlCl 2 afforded active catalysts for ethylene oligomerization to a tune of 97 600 g mol −1 h −1 under optimized conditions. Both ethylene oligomers and alkylated products were obtained depending on the solvent medium. The identity of the ligand and metal atom influenced the catalytic performance of the complexes. The immobilized complexes were recycled via magnetic separation in five successive runs without significant loss of catalytic activity and selectivity.