Difunctionalized indol-2-yl-ligated bimetallic rare-earth metal complexes: synthesis, characterization and high activity towards polymerization of 2-vinylpyridine

Abstract

A series of bimetallic rare-earth complexes {[μ-η¹:(μ-η¹:η¹):η¹-1-(2-C₅H₄N)-3-(2-C₇H₄NS)C₈H₄N]RE(CH₂SiMe₃)₂}₂ (RE = Y(7a), Er(7b), Yb(7c), Lu(7d)) were synthesized by treatment of rare-earth metal trialkyl complexes RE(CH₂SiMe₃)₃(THF)₂ with one equiv. of the proligand 1-(2-C₅H₄N)-3-(2-C₇H₄NS)C₈H₅N (6) in good isolated yields. Complex 7c can be converted to the divalent rare-earth metal complexes (η⁴:σ:κ¹-L)₂Yb^II [L = 1-(2-C₅H₄N)-3-(2-C₇H₄NS)C₈H₄N(CHSiMe₃)] (8) at elevated temperature in toluene solution. Complexes 7a, 7d and 8 were characterized by NMR spectroscopy. Additionally, the yttrium (7a), erbium (7b) and lutetium (7d) complexes exhibited high activity in the polymerization of 2-vinylpyridine with isotactic selectivity and high molecular weight.