Cationic rare-earth metal bis(tetrahydridoborato) complexes: direct synthesis, structure and ring-opening polymerisation activity toward cyclic esters

Abstract

Rare-earth metal tris(borohydrides) [Ln(BH₄)₃(thf)₃] (Ln = Y, La, Nd, Sm) are converted with one equivalent of the Brønsted acid [NEt₃H]⁺[BPh₄]⁻ in thf into the monocationic bis(borohydride) complexes [Ln(BH₄)₂(thf)₅]⁺[BPh₄]⁻. They efficiently initiate the ring-opening polymerisation of ε-caprolactone.