Homolysis of the Ln–N bond: Synthesis, characterization and catalytic activity of organolanthanide(II) complexes with 2-pyridylmethyl and 3-pyridylmethyl-functionalized indenyl ligands

Two series of new organolanthanide(II) complexes with general formula {η5:η1-[1-R-3-(2-C5H4NCH2)C9H5]}2Ln(II) (R = H–, Ln = Yb (3), Eu (4); R = Me3Si–, Ln = Yb (5), Eu (6)), and {η5:η1-[1-R-3-(3-C5H4NCH2)C9H5]}2Ln(II) (R = H–, Ln = Yb (9), Eu (10); R = Me3Si–, Ln = Yb (11), Eu (12)) were synthesized by silylamine elimination with one-electron reductive reactions of lanthanide(III) amides [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 (Ln = Yb, Eu) with 2 equiv. 1-R-3-(2-C5H4NCH2)C9H6 (R = H (1), Me3Si– (2)) or 1-R-3-(3-C5H4NCH2)C9H6 (R = H (7), Me3Si– (8)) in good yields. All the complexes were fully characterized by elemental analyses and spectroscopic methods. Complexes 3 and 5 were additionally characterized by single-crystal X-ray diffraction study. The catalytic activities of the complexes for MMA polymerization were examined. It was found that complexes with 3-pyridylmethyl substituent on the indenyl ligands could function as single-component MMA polymerization catalysts with good activities, while the complexes with 2-pyridylmethyl substituent on the indenyl ligands cannot catalyze MMA polymerization. The temperatures and solvents effect on the MMA polymerization have also been examined.

Graphical abstractTwo series of new organolanthanide(II) complexes with general formula {η5:η1-[1-R-3-(2-C5H4NCH2)C9H5]}2Ln(II) and {η5:η1-[1-R-3-(3-C5H4NCH2)C9H5]}2Ln(II) (R = H–, Me3Si–; Ln = Yb, Eu) were synthesized by tandem silylamine elimination/homolysis of the Ln–N bond reaction. The catalytic activities of the complexes on MMA polymerization were examined, and the solvents, temperatures, substituted groups effect on the polymerization were discussed.Figure optionsDownload full-size imageDownload as PowerPoint slide