“Oscillating” Metallocene Catalysts: How Do They Oscillate?

Rather than involving the rac-like (chiral) and meso-like (achiral) conformations, as commonly believed, the “oscillation” of [(2-Ar-indenyl)2ZrCl2] propene polymerization catalysts takes place within the rac-like conformation, between its two enantiomorphous forms with opposite enantioselectivities. The result is the peculiar polypropylene microstructure shown, which degenerates into a (quasi-)atactic form when the “oscillation” is faster than monomer insertion.