Homogeneous Ethylene‐Polymerization Catalysts Based on Alkyl Cations of the Rare‐Earth Metals: Are Dicationic Mono(alkyl) Complexes the Active Species?

Easily accessible, the tris(alkyl) complexes of rare-earth elements [Ln(CH2SiMe3)3(thf)2] are activated by [NMe2HPh][B(C6F5)4] in the presence of AliBu3 to catalyze homogeneous ethylene polymerization. Model reactions show that the bis(alkyl) yttrium monocation is converted into the mono(alkyl) dication (see picture), which appears to be the active species in ethylene polymerization.