Ultra-Rigid Metallocenes for Highly Iso- and Regio-Specific Polymerization of Propene: The Search for the Perfect Polypropylene Helix

Perfect polypropylene: A versatile synthesis route leading to 2-, 4-, and 7- substituted bisindenyl metallocenes (Zr, Hf) affording rigid and thus highly stereo- and regioselective polymerization catalysts, even at elevated temperatures, is presented. In particular, the hafnocene is able to produce isotactic polypropylene with extremely high melting transitions, exceeding 170°C with molecular weights above 5 000 000 g mol⁻¹.