A Binaphthyl‐Bridged Salen Zirconium Catalyst Affording Atactic Poly(propylene) and Isotactic Poly( α ‐olefins)

Summary: A binaphthyl‐bridged salen dichlorozirconium ( IV ) complex that displays an octahedral structure with a trans ‐O, cis ‐N, and cis ‐Cl arrangement was synthesized and tested as a precatalyst for ethylene and α ‐olefin polymerization. While use of methylaluminoxane (MAO) cocatalyst afforded poor catalytic activity, activation by mixtures of aluminium alkyls such as Al i Bu 3 and either MAO or [CPh 3 ][B(C 6 F 5 ) 4 ] resulted in reasonable polymerization activities for ethylene, propene, and higher α ‐olefins. Quite unexpectedly, while the polymerization of propene results in the production of a high‐molecular‐weight stereoirregular polymer, highly isotactic polymers are obtained under similar conditions from polymerization of 1‐butene, 1‐pentene, and 1‐hexene.Polymerization employing the binaphthyl‐bridged salen dichlorozirconium ( IV ) complex gave unexpected different stereospecificities for the polymerization of propene and higher α ‐olefins, to yield ultrahigh‐molecular‐weight atactic poly(propylene) and highly isotactic polymers, respectively.