As part of our investigation of high a-olefin oligomerization initiated by the complexation of a transition metal (Ti and Zr) compound with an organoaluminium derivative, the oligomerization of 1-hexene initiated by Zr(OnPr),AlEt,Cl was studied in detail at 20°C. It was found that a high mole ratio of [Al]/[Zr] (> 5) was necessary in order to observe activity for 1 -hexene oligomerization. The highest activity was obtained for ratios ranging from 12 to 15. The products formed were mainly dimers, addition products of the ethyl group to 1-hexene, and isomers of 1 -hexene. The corresponding saturated alkanes were also formed in large amount. Their relative percentage is proportional to the mole ratio of [Al]/[l-hexene].
The mechanistic aspects of 1-hexene oligomerization, initiated by Zr (OnPr)4-AlEt2C1 at 20 "C, are discussed on the basis of the product structures and distributions, the stability and reactivity of Mt-alkyls (Mt = metal) formed during I-hexene oligomerization, the reaction behaviour of an internal olefin (cis-2-hexene) and the investigation of interactions between Zr (OnPr),-A1Et2C1.After comparing the different possible initiation routes for 1-hexene oligomerization, a mechanism via insertion of 1-hexene into Al-alkyl bonds activated by zirconium is proposed. It was found that the olefin addition is not regiospecific. Primary addition into a linear alkyl-metal bond leads to an olefin insertion, whereas secondary addition only leads to elimination; when a-or Bbranched alkyl-metal bonds are involved, only transfer to monomer takes place. a) Part 1: cf. 12). b, Present address:
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.