Metal-size influence in isoselective 2-vinylpyridine polymerization

Eight new organometallic complexes were obtained by the reaction of trialkyl rare earth complexes Ln (CH2SiMe3)(3)(THF)(2) (Ln a Y, Lu, Ho, Dy) with tetradentate phenol ether ligands. Among them the structure of complex 7 with Lu was confirmed by single crystal X-ray diffraction. These complexes exhibited moderate to high activity for 2-VP polymerization at ambient temperature in toluene. Complex 5 showed the highest catalytic activity, with a turnover frequency of 1714 h(-1). Significantly, the 2-VP polymerization is also stereospecific, producing isotactic poly(2-VP) with an isotacticity of mm = 0.44-0.99. The catalytic experimental results indicate that the size of metal atom obviously influences the stereoregularity of the growing polymer chain, and catalysts with Ho atom exhibit better isotactic selectivity than other metal catalysts. (C) 2019 Elsevier Ltd. All rights reserved.