<i>ansa</i>-Zirconocene Catalysts for Isotactic-Selective Propene Polymerization at High Temperature: A Long Story Finds a Happy Ending
Pavel S. Kulyabin, Georgy P. Goryunov, Mikhail I. Sharikov, Vyatcheslav V. Izmer, Antonio Vittoria, Peter H. M. Budzelaar, Vincenzo Busico, Alexander Z. Voskoboynikov, Christian Ehm, Roberta Cipullo, Dmitry V. Uborsky
Abstract
Absolute rigidity is rare in the “soft” world of organometallics. Here we introduce two cyclopenta[a]triptycyl ansa-zirconocene catalysts for isotactic-selective propene polymerization, designed by means of an integrated high-throughput experimentation/quantitative structure–activity relationship modeling approach. An ultrarigid ligand precisely wrapped around the Zr center enforces an enzyme-like lock and key fit, effectively hampering undesired reactive events, even at high temperature. Stereodefective units are hardly detectable by 13C NMR in the polymer produced at 120 °C; this corresponds to an enantioselectivity exceeding 6–7 kcal/mol: i.e., less than 1 propene misinsertion every 4000 (and at room temperature, one every ∼40000!).