Quasi-Living trans-1,4-Polymerization of Isoprene by Cationic Rare Earth Metal Alkyl Species Bearing a Chiral (S,S)‑Bis(oxazolinylphenyl)amido Ligand

A series of chiral mononuclear dialkyl complexes [(S,S)-BOPA]­Ln­(CH2SiMe3)2 (1, 2) (BOPA = (S,S)-bis­(oxazolinylphenyl)­amido; Ln = Sc (1); Ln = Lu (2)) and binuclear alkyl complexes [ο-(S)-OPA–C6H4–(CH2SiMe3)­CN–CH­(iPr)­CH2–O]­Ln­(CH2SiMe3)}2 (3, 4) (OPA = (oxazolinylphenyl)­amine; Ln = Y (3); Ln = Tm (4)) have been synthesized in moderate yields via one-pot acid–base reactions by use of the tris­(trimethylsilylmethyl) rare earth metal complexes with the chiral tridentate (S,S)-bis­(oxazolinylphenyl)­amine ligand. In the presence of activator with or without a small amount of AliBu3, the dialkyl complexes 1 and 2 exhibit very high activities (up to 6.8 × 105 g molLn–1 h–1) and trans-1,4-selectivity (up to 100%) in the quasi-living polymerization of isoprene, yielding the trans-1,4-PIPs with moderate molecular weights (Mn = (0.2–1.0) × 105 g/mol) and narrow molecular weight distributions (Mw/Mn = 1.02–2.66).