Rare‐Earth Metal Mixed Chloro/Methyl Compounds: Heterogeneous–Homogeneous Borderline Catalysts in 1,3‐Diene Polymerization

On the right path: A chlorination–alkylation sequence involving the reaction of preformed mixed amido/chloro complexes (see structure) with trimethylaluminum causes precipitation of [{LnaAlbMecCld}n], which for Ln=Nd polymerizes isoprene in greater than 99 % cis stereospecificity (Mn/Mw=1.76); the catalyst performance is comparable to that observed following a “detour” alkylation–chlorination sequence employing [Nd(AlMe4)3]/Et2AlCl.