Selective dimerization of propylene to 2,3-dimethylbutenes by homogeneous catalysts prepared from halogeno(beta-dithioacetylacetonato)nickel(II) complexes containing a highly hindered alkyl phosphine ligand and different aluminium co-catalysts

Halogeno(beta-dithioacetylacetonato)nickel(II) complexes with different alk yl phosphine ligands have been studied in the selective propylene dimerizat ion to 2,3-dimethylbutenes (DMB) in the presence of different organoalumini um compounds. When basic and bulky phosphine ligands, such as tricyclohexyl -(PCy3) and triisopropyl-phosphine ((PPr3)-Pr-1) were used in combination w ith suitable co-catalysts, such as Et3Al2Cl3, Et2AlCl and EtAlCl2/methylalu moxane (MAO), the best results in terms of productivity (up to similar to 3 6,000 h(-1)) and yield to DMB (up to 68%) were obtained, A detailed analysi s of the composition of C9 cut in some selected experiments allowed to eval uate the octane characteristics of the reaction mixture offering both inter esting applicative perspectives and mechanistic information. (C) 2000 Elsev ier Science B.V. All rights reserved.