The triptycene-motif in ETM olefin polymerization catalysis

We have recently disclosed three cyclopenta[a]triptycyl ansa-zirconocene catalysts for isotactic-selective propene polymerization,1-2 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!). These catalysts feature the two thirds of the triptycene paddle-wheel in formal 4,5-position of the indenyl fragment of the backbone. The effect on olefin polymerization performance is dramatic. In this poster the effect of installing the triptycene unit in formal 5,6-position both in propene polymerization and ethene/1-hexene copolymerization will be presented.