Homolysis of the Ln–N bond: Synthesis, characterization and catalytic activity of organolanthanide(II) complexes with furfuryl- and tetrahydrofurfuryl-functionalized indenyl ligands

A series of new organolanthanide(II) complexes with furfuryl- and tetrahydrofurfuryl-functionalized indenyl ligands were synthesized via one-electron reductive elimination reaction. Treatments of [(Me3Si)2N]3LnIII(μ-Cl)Li(THF)3 (Ln = Yb, Eu) with 2 equiv. of C4H7OCH2C9H7 (1) or C4H3OCH2C9H7 (2), respectively in toluene at moderate high temperatures produced, after workup, the corresponding organolanthanide(II) complexes with formula [η5:η1-(C4H7OCH2C9H6)]2LnII (Ln = Yb (5), Ln = Eu (6)) and [η5:η1-(C4H3OCH2C9H6)]2LnII (Ln = Yb (7), Ln = Eu (8)) in reasonable to good yields. Treatments of [(Me3Si)2N]3LnIII(μ-Cl)Li(THF)3 (Ln = Yb, Eu) with 2 equiv. of C4H7OCH2C9H6SiMe3 (3) or C4H3OCH2C9H6SiMe3 (4), respectively, in toluene at moderate high temperatures afforded, after workup, the corresponding organolanthanide(II) complexes with formula [η5:η1-(C4H7OCH2C9H5SiMe3)]2LnII (Ln = Yb (9), Ln = Eu (10)) and[η5:η1-(C4H3OCH2C9H5SiMe3)]2LnII (Ln = Yb (11), Ln = Eu (12)) in good to high yields. All the compounds were fully characterized by spectroscopic methods and elemental analyses. The structure of complex 9 was additionally determined by single-crystal X-ray analyses. Studies on the catalytic activities of complexes showed that the complexes having silyl group functionalized indenyl ligands have high catalytic activities on ε-caprolactone polymerization. The temperatures, substituted groups on the indenyl ligands of the complexes, and solvents effects on the catalytic activities of the complexes were examined.