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U.V./visible spectroscopic study of the rac ‐Et(Ind) 2 ZrCl 2 /MAO olefin polymerization catalytic system, 1. Investigation in toluene
Author(s) -
Coevoet Dorothée,
Cramail Henri,
Deffieux Alain
Publication year - 1998
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/(sici)1521-3935(19980701)199:7<1451::aid-macp1451>3.0.co;2-j
Subject(s) - methylaluminoxane , bathochromic shift , chemistry , metallocene , polymerization , toluene , hypsochromic shift , polymer chemistry , catalysis , photochemistry , organic chemistry , fluorescence , polymer , physics , quantum mechanics
The U.V./visible spectrum of the rac ‐Et(Ind) 2 ZrCl 2 /methylaluminoxane (MAO) catalytic system in toluene at 20°C, which is related to the ‘ligand to metal charge transfer’ bands (LMCT), varies greatly with the MAO/Zr ratio (mole ratio Al/Zr). Indeed, for MAO/Zr ratios <30, a hypsochromic shift of the absorption band is observed and is explained by monomethylation of the metallocene dichloride. Conversely, a progressive bathochromic shift of the absorption band is observed for MAO/Zr ratios ranging from 30 to 2000. This behavior is interpreted by the formation of an increasing proportion of dissociated to associated zirconocenium species [L 2 ZrX] + [MAOCl] − . The λ max changes of the U.V./visible spectrum of the rac ‐Et(Ind) 2 ZrCl 2 /MAO system were correlated with its catalytic activity for the hex‐1‐ene polymerization. Moreover, a conductimetric study performed on the rac ‐Et(Ind) 2 ZrCl 2 /MAO system for different MAO/Zr ratios is also in agreement with the formation of ionic species with different nature and ionization degrees.