Synthesis, characterization and catalytic activity of organolanthanide(II) complexes with heterocyclic-functionalized fluorenyl ligands

Two series of new organolanthanide(II) complexes with tetrahydro-2H-pyranyl- or N-piperidineethyl-functionalized fluorenyl ligands were synthesized via one-electron reductive elimination reaction. Treatments of [(Me3Si)2N]3LnIII(μ-Cl)Li(THF)3 with 2 equiv. of C5H9OCH2C13H9 (1) or C5H10NCH2CH2C13H9 (2), respectively, in toluene at about 80 °C produced, after workup, the corresponding organolanthanide(II) complexes with formula [η5:η1-C5H9OCH2C13H8]2LnII (Ln = Yb (3), Ln = Eu (4)) and [η5:η1-C5H10NCH2CH2C13H8]2LnII (Ln = Yb (5), Ln = Eu (6)) in good yields. All the compounds were fully characterized by spectroscopic methods and elemental analyses. The structures of complexes 3, 4, and 6 were additionally determined by single-crystal X-ray analyses. It represents the first example of solvent-free organolanthanide(II) complexes with fluorenyl ligands. The catalytic properties of the organolanthanide(II) complexes on the polymerization of ε-caprolactone and methyl methacrylate have been studied. The temperatures, solvents and coordination effects on the catalytic activities of the complexes were examined.