Rare-Earth Ziegler−Natta Catalysts:  Carboxylate−Alkyl Interchange

Alkylated rare-earth-metal centers are definitely formed in “Mischkatalysatoren”: the homoleptic, tailor-made rare-earth carboxylate complexes {Ln(O2CC6H2iPr3-2,4,6)3}n (Ln = Y, La, Nd, Lu) react with trimethylaluminum to yield hexane-soluble monolanthanide complexes of the larger elements featuring a η2-coordinating tetraalkylaluminate ligand and a novel ancillary AlMe2-bridged bis(carboxylate) ligand. In the presence of AlMe2Cl, such alkylated derivatives transform isoprene to a high-cis polymer (>99%).