Synthesis and characterization of new bis(2-R-indenyl) zirconium dichloride complexes for the olefin polymerization
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文摘
A series of 2-alkylindene(2-RInd; R = Me, i-Pr, n-Bu, Bzl, Cy, t-Bu) were prepared by nucleophilic addition of the corresponding alkyl anions to 2-indanone in the presence (or absence) of LaCl3. With these 2-alkylindenes, bis(2-alkylindenyl)zirconium dichloride complexes were synthesized to investigate the effects of alkyl substituents at 2-position of indene on the rotational conversion rate between rotamers (racemic and meso) and the catalytic activities toward olefin polymerization. Analysis of NMR spectra could line up the electron donating abilities and steric bulkiness of alkyl substituents in order and variable temperature NMR analysis (from 298 to 193 K) proved that these alkyls could not freeze free rotation of indenyl ligands. These complexes showed catalytic activities toward ethylene and propylene polymerization and the variation of catalytic activities(PE, Me > Cy > i-Pr > Bzl > n-Bu; PP, Me > n-Bu > i-Pr > Cy > Bzl), molecular weights(PE, n-Bu > Cy > i-Pr > Me > Bzl; PP, n-Bu > Me > Cy > i-Pr > Bzl), and polydispersities(PE, 2.80-5.05; PP, 2.23-3.30) were rationalized with steric, electronic, and structural factors. Steric bulkiness of substituents played an important role in the propylene polymerization but relative importance of these factors were different in the ethylene polymerization.