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 AliBu3 and either MAO or [CPh3][B(C6F5)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.magnified imagePolymerization 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.