ZIRCONOCENE-ALUMOXANE-(1 1) - A CATALYST FOR THE SELECTIVE DIMERIZATION OF ALPHA-OLEFINS/

A well known catalytic system for the oligomerization of 1-alkenes is zirconocene dichloride (Cp2ZrCl2,), when activated by a large excess o f methylalumoxane (MAO). Surprisingly, when activated by only 1 equiv. of MAO, Cp2ZrCl2, selectively and catalytically dimerizes alpha-olefi ns without formation of any higher oligomeric species. This reaction i s shown to be general for a number of alpha-olefins. The conversion of o-diallylbenzene gives a seven-membered cyclic product in an intramol ecular dimerization reaction. A possible mechanism for the dimerizatio n process involving a zirconium-hydrido species as the catalyst is for mulated, and evidence for it is given by detection of by-products and a deuteration experiment. (C) 1998 Elsevier Science S.A.