Nickel metallodendrimers as catalyst precursors in the tandem oligomerization of ethylene and Friedel–Crafts alkylation of its olefinic products

• In this paper we report on the preparation of a new salicylaldimine and iminopyridyl nickel metallodendrimers.
• These metallodendrimers are active ethylene oligomerization catalysts when using EtAlCl2 as a co-catalyst.
• The oligomerization products undergo EtAlCl2 mediated Friedel/Crafts alkylation with the solvent, toluene.

The synthesis and catalytic activity of nickel metallodendrimers (C1–C6) are reported. The metallodendrimers were synthesized by the coordination of the metal precursors, Ni(OAc)2 and Ni(DME)Br2, to the periphery of salicylaldimine and iminopyridyl modified dendritic ligands, DL1–DL6, based on the generation 1 to generation 3 diaminobutane polypropylene imine (DAB-PPI) dendrimers. The metallodendrimers were tested in the oligomerization of ethylene and were found to be active catalysts. When using this catalyst system, it was found that a tandem process occurred in which ethylene oligomerization was followed by Friedel–Crafts alkylation of the reaction solvent, toluene. The latter process is mediated by the aluminium co-catalyst, EtAlCl2.

The synthesis of a range of polypropyleneimine based iminopyridyl and salicylaldimine nickel metallodendrimers and their evaluation as ethylene oligomerization catalyst precursors are reported. All the metallodendrimers were found to be active in the oligomerization of ethylene employing EtAlCl2 as a co-catalyst. In addition it was also found that the EtAlCl2 mediates a subsequent Friedel–Crafts alkylation reaction between the formed oligomeric products and the aromatic solvent, toluene leading to the formation of a range of alkyl benzenes.Figure optionsDownload as PowerPoint slide