Tandem ethylene dimerization and Friedel-Crafts alkylation of toluene catalyzed by homo- and heterogeneous nickel(II) and palladium(II) pre-catalysts

• Ethylene oligomerization using homo- and heterogeneous Ni(II) and Pd(II) complexes.
• Complexes were activated with EtAlCl2 (co-catalyst) in toluene.
• Ethylene dimerization and subsequent Friedel-Crafts alkylation of toluene.
• Regioisomers of mono-, di- and tri-butyltoluene are formed in the reactions.

Palladium(II) and nickel(II) complexes (1–4) of the Schiff base ligands, N-(2-pyridinylmethylene)-3-(triethoxysilyl)-1-propanamine (L1) and N-(1-(pyridin-2-yl)ethylidene)-3-(triethoxysilyl)-1-propanamine (L2), have been synthesized and characterized by FT-IR and elemental analysis. The palladium complexes were also characterized by multinuclear NMR studies and the molecular structure of one of palladium complex, 1, was authenticated by X-ray crystallography. Complex 1 and the two nickel complexes, 3 and 4, were evaluated as pre-catalysts for ethylene oligomerization reactions using EtAlCl2 as co-catalyst. On activation with EtAlCl2, the complexes form active catalysts which dimerize ethylene to mainly butenes and subsequently, and these butenes undergo Friedel-Crafts alkylation of toluene (the solvent used for the ethylene reactions); leading to the formation of regioisomers of mono-, di- and tri-butyltoluenes. The nickel complexes, 3 and 4, were also immobilized on silica support to give the nickel pre-catalysts m1 and m2, which are also active for ethylene dimerization and subsequent Friedel-Crafts alkylation of toluene.

Nickel (II) and palladium (II) complexes as well as nickel (II) complexes immobilized on silica have been investigated as pre-catalysts for ethylene oligomerization reactions in presence of EtAlCl2 co-catalyst. These nickel and palladium complexes catalyze the tandem ethylene dimerization and subsequent alkylation of toluene via a Friedel-Crafts alkylation process.Figure optionsDownload as PowerPoint slide