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 [o-(S)-OPA-C6H4-(CH2SiMe3)C=N-CH(Pr-i)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 (AlBu3)-Bu-i, the dialkyl complexes 1 and 2 exhibit very high activities (up to 6.8 x 10(5) g mol(Ln)(-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 (M-n = (0.2-1.0) x 10(5) g/mol) and narrow molecular weight distributions (M-w/M-n = 1.02-2.66).