Cationic Rare‐Earth Polyhydrido Complexes: Synthesis, Structure, and Catalytic Activity for the cis‐1,4‐Selective Polymerization of 1,3‐Cyclohexadiene

Rare activity from rare earths: Cationic rare-earth hydrides show regio- and stereoselectivity for the polymerization of 1,3-cyclohexadiene (CHD) to afford soluble crystalline cis-1,4-linked poly(CHD) that was previously unavailable. These cationic clusters are made by treating the corresponding neutral complexes with a borate activator (see scheme; Cp′: C5Me4SiMe3).