Rare earth metal alkyl complexes with methyl-substituted triazacyclononane-amide ligands: Ligand variation and ethylene polymerization catalysis

Sergio Bambirra, Daan van Leusen, Cornelis G. J. Tazelaar, Auke Meetsma, Bart Hessen*

*Bijbehorende auteur voor dit werk

OnderzoeksoutputAcademicpeer review

62 Citaten (Scopus)
42 Downloads (Pure)


A series of rare earth metal dialkyl complexes was prepared with the general formula [Me(2)TACN-(B)-NR]M(CH2SiMe3)(2) (TACN = 1,4,7-triazacyclononane, B = (CH2)(2), SiMe2; R = tBu, secBu, nBu; M = Sc, Y, Nd, La). For M = Sc, mixed monoalkyl-monochloro complexes were also accessible. Selected examples of these complexes were structurally characterized and show the metal in a distorted octahedral environment. With Lewis or Bronsted acid activators the dialkyl compounds can be converted to the corresponding monoalkyl cations, which were characterized by NMR spectroscopy. Comparative testing in catalytic ethylene polymerization showed that the catalyst activity is most strongly influenced by the metal ionic radius, but that variations in the ligand backbone and substitution pattern do influence other factors, such as polymer molecular weight and catalyst stability. Catalysts with the intermediately sized rare earth metal yttrium generally showed the highest activity, but some of these catalysts produce polyethylene with broad molecular weight distributions, suggesting multisite behavior. Hypothetically this could be caused by intermolecular ligand scrambling processes. Evidence that these may occur was found in the isolation of the "half-flyover" bimetallic yttrium complex {[eta(3):eta(1)-[Me(2)TACN(CH2)(2)NtBu]Y(CH2SiMe3)}{eta(3):mu-eta(1)-[Me(2)TACN(CH2)(2)NtBu]Y(CH2SiMe3)(3).

Originele taal-2English
Pagina's (van-tot)1014-1023
Aantal pagina's10
Nummer van het tijdschrift4
StatusPublished - 12-feb-2007

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