Cyclocopolymerization:: A mechanistic probe for dual-site alternating copolymerization of ethylene and α-olefins

The copolymerization of ethylene with 1,5-hexadiene or 1-hexene was studied with the series of ansa-metallocenes Me2Si(Cp)(9-Flu)ZrCl2 (1), Me2Si(1-Ind)(9-Flu)ZrCl2 (3), and Me2Si(9-Flu)2ZrCl2 (4). 1,5-Hexadiene, a monomer which requires two insertion events to be cyclopolymerized, when copolymerized with ethylene using 3/MAO, gave a copolymer with a novel architecture. When compared with the copolymerization of 1-hexene with ethylene, the observed striking differences between the two copolymers provided compelling evidence for a dual-site alternating copolymerization mechanism in both cases. The copolymerization results from 1/MAO and 4/MAO further support this. Copyright © 2002 American Chemical Society.