Lanthanum tribenzyl complexes as convenient starting materials for organolanthanum chemistry

Sergio Bambirra, Auke Meetsma, Bart Hessen*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

86 Citations (Scopus)
474 Downloads (Pure)

Abstract

Simple tribenzyl complexes of lanthanum, [La(CH2C6H4-4-R)(3)(THF)(3)] (R = H (1a), Me (1b)), were prepared in a remarkably straightforward fashion from LaBr3(THF)(4) and potassium benzyl reagents. Single-crystal X-ray diffraction revealed a fac arrangement of the three THF ligands and eta(2) binding of the benzyl groups. These compounds are convenient precursors to other organolanthanum complexes. Reaction of 1a with the amidine ArN=CPhNHAr (Ar = 2,6-Pr-i 2C6H3) affords the corresponding mono(amidinate) dibenzyl derivative 2. Complex 1b reacts with LiCH2C6H4-4-Me to give the THF-free anion [La(CH(2)C(6)H(4-)4- Me)(4)](-) (3). Reactions of 1 with 1 or 2 equiv of [PhNMe2H][B(C6X5)(4)] (X = H, F) generate the corresponding mono- and dicationic benzyl species [La(CH2C6H4-4-R)(2)(THF)(4)](+) ( 4) and [La(CH2C6H4-4- R)(THF)(6)](2+) ( 5), which were structurally characterized. Scouting ethylene polymerization experiments indicate that these species are only modestly active catalysts but suggest that the monocationic dibenzyl species is more efficient. Both neutral and cationic lanthanum benzyl complexes effect the catalytic intramolecular hydroamination/cyclization of 2,2-dimethyl-4-pentenylamine. It was also observed that polycationic La species without ancillary ligands effectively catalyze the isomerization of the substrate to (E)-2,2-dimethyl-3-pentenylamine.

Original languageEnglish
Pages (from-to)3454-3462
Number of pages9
JournalOrganometallics
Volume25
Issue number14
DOIs
Publication statusPublished - 3-Jul-2006

Keywords

  • X-RAY CRYSTAL
  • UNPROTECTED AMINO OLEFINS
  • RARE-EARTH-METALS
  • C-H ACTIVATION
  • INTRAMOLECULAR HYDROAMINATION
  • YTTRIUM COMPLEXES
  • ALKYL COMPLEXES
  • POLYMERIZATION CATALYSTS
  • ORGANOSCANDIUM COMPLEXES
  • CYCLOPENTADIENYL LIGAND

Cite this