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

A series of bimetallic rare-earth complexes {[mu-eta 1:(mu-eta 1:eta 1):eta 1-1-(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 (eta 4:sigma:kappa 1-L)2YbII [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. A series of difunctionalized rare-earth metal alkyl complexes bearing 1-(2-pyridinyl)-3-(2-benzothiazolyl) indol-2-yl ligand were prepared and applied for polymerization of 2VP with high isotactic selectivity and high molecular weight.