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New highly active and selective Et oligomerization catalysts based on cationic diamide zirconium complexes
Author(s) -
Horton Andrew D.,
von Hebel Klaas L.,
de With Jan
Publication year - 2001
Publication title -
macromolecular symposia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.257
H-Index - 76
eISSN - 1521-3900
pISSN - 1022-1360
DOI - 10.1002/1521-3900(200108)173:1<123::aid-masy123>3.0.co;2-9
Subject(s) - cationic polymerization , chemistry , catalysis , olefin fiber , ethylene , toluene , electrophile , alkyl , zirconium , medicinal chemistry , reagent , ligand (biochemistry) , solvent , alkane , polymer chemistry , scavenger , organic chemistry , radical , biochemistry , receptor
Group 4 complexes based on the diamide ligand, [Me 3 CN(SiMe 2 ) 2 NCMe 3 ] 2− , have been investigated as possible catalysts for olefin conversions. The dialkyl complexes, (Me 2 SiNCMe 3 ) 2 ZrR 2 (R = CH 2 Ph, Me), were converted into zwitterionic (X‐ray: {Me 2 SiNCMe 3 } 2 Zr(η 1 ‐Bz){η n ‐BzB(C 6 F 5 ) 3 }), or cationic mono‐alkyl compounds by reaction with B(C 6 F 5 ) 3 or borate reagents. These electrophilic species catalyzed ethylene oligomerization , affording highly linear alpha ‐olefins under mild conditions (C 6 fraction > 99.5% 1‐hexene at 50°C, 6 bar). The highest activities (290 Kg/g Zr.h) were obtained in toluene solvent using tri‐ iso ‐butylaluminium (TIBA) as scavenger. The catalyst exhibited activity decay in alkane solvent, which was countered by replacement of TIBA by more crowded trialkylaluminium scavengers or branched alkylaluminoxane scavengers. The product consisted primarily of linear alpha‐olefins (LAO) with low levels of remote‐branched AO's. These are formed by successive insertion of higher olefin and one or more ethylenes in a growing chain, followed by chain transfer.