C–H-Bond Activation and Isoprene Polymerization Studies Applying Pentamethylcyclopentadienyl-Supported Rare-Earth-Metal Bis(Tetramethylaluminate) and Dimethyl Complexes oleh Christoph O. Hollfelder, Melanie Meermann-Zimmermann, Georgios Spiridopoulos, Daniel Werner, Karl W. Törnroos, Cäcilia Maichle-Mössmer, Reiner Anwander