Highly Isospecific Polymerization of Propylene with Bis(phenoxy-imine) Zr and Hf Complexes Using iBu3Al/Ph3CB(C6F5)4 as a Cocatalyst

Highly isospecific propylene polymerization was achieved by bis(phenoxy-imine) Zr and Hf complexes combined with iBu3Al/Ph3CB(C6F5)4. Microstructural analyses of the isotactic polymers suggested that the polymerization probably proceeds via a site-control mechanism with a 1,2-insertion of propylene. Among the complexes examined, Hf complex 2 produced the highest tacticity polypropylene ([mmmm] 96.8%, Tm 165.1 °C) that is comparable to that made by the best heterogeneous Ziegler–Natta catalysts.