Butadiene oligomerization and telomerization catalyzed by transition metal complexes supported on organic polymers

Abstract

Nickel acetylacetonate, heterogenized on linear poly(vinylpyridines) or 2,2'-dipyridyl-functionalized poly ( styrene/divinylbenzene) and reduced with EtOAlEt 2, effectively catalyzes the cyclotrimerization of butadiene to 1,5,9-cyclododecatriene, but normally leaches strongly from the polymers. On the other hand, Ni-poly(4-vinylpyridine) only loses approximately 10% of its nickel during the reaction and can be recycled five times. This can be explained by the ready back-coordination of the poly(4-vinylpyridine) to the nickel atom in the reductive elimination step. The corresponding polymeric iron catalysts oligomerize butadiene to several open-chain and cyclic dimers and trimers, but lose their activity quite rapidly due to aggregation of the iron atoms on the polymer. Polymer-bound palladium acetylacetonate only exhibits catalytic activity after the addition of triphenylphosphine. 1-Methoxy-2, 7-octadiene and 1,3,7-octatriene are formed as the principal products, but the reactions occur in the homogeneous phase and the palladium is not back-bound to the polymer. The heterogenization of cationic η 3-allylpalladium(II) complexes shows that they coordinate to strongly and weakly acidic ion-exchange resins and lose their selectivity for industrially interesting tetramers. We are presently testing the catalytic activity of cationic η 3-allyl-palladium complexes heterogenized on poly(styrene/divinylbenzene) functionalized with dibenzylideneacetone, which should have a good selectivity for such tetramers.