F. Benvenuti et al., Selective propylene dimerization to 2,3-dimethylbutenes by heterogenized polymer-supported beta-dithioacetylacetonate nickel(II) precursors activatedby organoaluminium co-catalysts, APP CATAL A, 204(1), 2000, pp. 7-18
Heterogenized nickel catalysts, prepared in situ by anchoring nickel(II) ph
osphino complexes to polymer-bound beta -dithioacetylacetonate (sacsac) che
late ligands and activated by organoaluminium co-catalysts, have been emplo
yed for the selective propylene oligomerization to 2,3-dimethylbutenes (DMB
). In particular, the effect of reaction conditions as well as of nature of
phosphine ligand and organoaluminium activator was studied. The obtained d
ata have shown that the above catalysts, at temperatures below 0 degreesC a
nd in the presence of chlorobenzene as reaction medium, display a very high
activity and selectivity to DMB, when basic and bulky alkyl phosphine liga
nds and organoaluminium co-catalysts of medium Lewis acidity are used. The
performances given above are very similar to those obtained with the corres
ponding homogeneous catalysts. Flow experiments have allowed to check that
the heterogenized catalysts given above are substantially stable, maintaini
ng their performances during the time. No significant metal leaching was de
tected in the course of the reaction, at least under the adopted conditions
, thus suggesting that these polymer-supported nickel catalysts behave as r
eally heterogeneous catalysts, due to the presence of the bidentate sacsac
ligand able to permanently fix the metal to the resin. (C) 2000 Elsevier Sc
ience B.V. All rights reserved.