Cationic Rare‐Earth‐Metal Half‐Sandwich Complexes for the Living trans‐1,4‐Isoprene Polymerization

Rare, but well done! Fluorinated borates [Ph3C][B(C6F5)4] and [PhNMe2H][B(C6F5)4] and the borane reagent B(C6F5)3 activate rare-earth-metal bis(tetramethylaluminate) complexes in a distinct and efficient manner (an activated catalyst is shown in the picture) for the fabrication of synthetic gutta-percha (99.5 % trans-1,4-polyisoprene, Mn=0.8–4.4×105 g mol−1, Mn/Mw=1.18).