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

Abstract

A series of new organolanthanide(II) complexes with furfuryl- and tetrahydrofurfuryl-functionalized indenyl ligands were synthesized via one-electron reductive elimination reaction. Treatments of [(Me 3Si) 2N] 3Ln III(μ-Cl)Li(THF) 3 (Ln = Yb, Eu) with 2 equiv. of C 4H 7OCH 2C 9H 7 ( 1) or C 4H 3OCH 2C 9H 7 ( 2), respectively in toluene at moderate high temperatures produced, after workup, the corresponding organolanthanide(II) complexes with formula [η 5:η 1-(C 4H 7OCH 2C 9H 6)] 2Ln II (Ln = Yb ( 5), Ln = Eu ( 6)) and [η 5:η 1-(C 4H 3OCH 2C 9H 6)] 2Ln II (Ln = Yb ( 7), Ln = Eu ( 8)) in reasonable to good yields. Treatments of [(Me 3Si) 2N] 3Ln III(μ-Cl)Li(THF) 3 (Ln = Yb, Eu) with 2 equiv. of C 4H 7OCH 2C 9H 6SiMe 3 ( 3) or C 4H 3OCH 2C 9H 6SiMe 3 ( 4), respectively, in toluene at moderate high temperatures afforded, after workup, the corresponding organolanthanide(II) complexes with formula [η 5:η 1-(C 4H 7OCH 2C 9H 5SiMe 3)] 2Ln II (Ln = Yb ( 9), Ln = Eu ( 10)) and[η 5:η 1-(C 4H 3OCH 2C 9H 5SiMe 3)] 2Ln II (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.