Propylene oligomerization by nickel catalysts in biphasic fluorinated systems

In the present paper, the dimerization of propylene to 2,3-dimethylbutenes (DMB) with fluorinated nickel precursors, such as bis(tetradecafluoro-4,6-nonandionate)nickel(II).2dmf [Ni(tdfnd)(2)(dmf)(2)] and bis(hexafluoro-2,4-pentandionate)nickel(II) [Ni(hfacac)(2)], in combination with phosphine ligands and aluminium alkyl promoters, was investigated in fluorous solvents as reaction medium with the aim of realizing a catalytic process operating in a fluorinated biphasic system (FBS). The role of the nature of the perfluorinated medium was carefully examined and significant productivities (TOF up to similar to25,000 h(-1)) were ascertained. Also fluorinated phosphine ligands were used with the aim of improving catalyst solubility in the fluorinated phase. Finally, with the aim to reach the same goal, tris(pentafluorophenyl)borane [B(C6F5)(3)], was also employed in the place of organoaluminium co-catalysts. However, in all the catalytic experiments a progressive migration of the catalyst towards the hydrocarbon phase, generated by the formation of the oligomeric products, was observed. thus evidencing the difficulty of realizing a FBS olefin oligomerization catalytic process, at least under the adopted conditions. (C) 2002 Elsevier Science B.V. All rights reserved.