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Mixed Aluminum‐Magnesium‐Rare Earth Allyl Catalysts for Controlled Isoprene Polymerization: Modulation of Stereocontrol
Author(s) -
Ajellal Noureddine,
Furlan Luciano,
Thomas Christophe M.,
Casagrande Osvaldo L.,
Carpentier JeanFrançois
Publication year - 2006
Publication title -
macromolecular rapid communications
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.348
H-Index - 154
eISSN - 1521-3927
pISSN - 1022-1336
DOI - 10.1002/marc.200500775
Subject(s) - isoprene , yttrium , polymerization , catalysis , magnesium , chemistry , alkyl , rare earth , activator (genetics) , medicinal chemistry , stereochemistry , polymer chemistry , nuclear chemistry , copolymer , organic chemistry , mineralogy , receptor , polymer , oxide , biochemistry
Summary: The performances of readily available Ln(allyl) 2 Cl(MgCl 2 ) 2 · (THF) 4 precursors (Ln = Nd, 1 ; Y, 2 ; La, 3 ), in combination with alkyl aluminum activators [MAO, AlMe 3 , AlEt 3 , Al( i Bu) 3 ], have been studied in isoprene polymerization. The catalyst combination 1 /MAO (1:30) shows a high activity (average TOFs up to ca. 5 × 10 4 mol (Ip) · mol (Nd) −1 · h −1 at 20 °C) and produces polyisoprene in a controlled fashion with up to 98.5% cis content, number‐average molecular weights in reasonable agreement with calculated values, and relatively narrow polydispersities index ( $\overline M _{\rm w} /\overline M _{\rm n}$ = 1.20–1.70). The yttrium precursor 2 affords systems with much lower activity and degree of control, but enables the formation of either 1,4‐ cis ‐enriched (75%) or 1,4‐ trans ‐enriched (91%) polyisoprenes, simply replacing the MAO activator by AlEt 3 or Al( i Bu) 3 , respectively.Formation of 1,4‐ cis ‐ or 1,4‐ trans ‐enriched polyisoprenes upon activation with MAO.