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Reduction of bis(η 5 ‐cyclopentadienyl)zirconium dichloride in the presence of methylalumoxane
Author(s) -
Cam Darinn,
Sartori Franco,
Maldotti Andrea
Publication year - 1994
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/macp.1994.021950813
Subject(s) - zirconium , cyclopentadienyl complex , electron paramagnetic resonance , metallocene , ethylene , chemistry , toluene , alkyl , inorganic chemistry , catalysis , polymer chemistry , organic chemistry , nuclear magnetic resonance , polymerization , polymer , physics
The reaction occurring between bis(η 5 ‐C 5 H 5 )ZrCl 2 (C 5 H 5 = cyclopentadienyl) and methylalumoxane (MAO) has been studied by means of electron paramagnetic resonance (EPR) spectroscopy at different zirconium concentrations and Al/Zr mole ratios. The toluene solution of bis(η 5 ‐C 5 H 5 )ZrCl 2 /methylalumoxane, in the absence of ethylene, was verified to be more stable than the catalytic system based on bis(η 5 ‐C 5 H 5 )TiCl 2 /AIR 3 (R = alkyl). Zr(IV) was reduced to Zr(III) in small amounts with a Landé factor g = 1,998 and a hyperfine interaction splitting constant α ( 91 Zr) = 7 G. The presence of ethylene strongly increased the efficiency of the Zr(IV) to Zr(III) reduction. Simultaneously it modified the chemical electronic surrounding of the Zr nucleus as revealed by the sharp increase of α( 91 Zr) = 12 G.