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.