We have synthesized a new series of ytterbium(Ⅱ) and europium(Ⅱ) complexes by tandem silylamine elimination/homolysis of Ln−N (Ln=Yb, Eu) bonds. The interaction of 2 equiv. of C9H7CH2CH2CH2NMe2 (1) with [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 (Ln=Yb, Eu) in toluene under reflux produced lanthanide(Ⅱ) complexes [(η5:η1-C9H6CH2CH2CH2NMe2)2-Ln] [Ln=Yb (2), Eu(3)] in 67 and 74% yields, respectively. Treatment of 2 equiv. of Me2Si(Me2NCH2CH2C9H6)(NHtBu) with [(Me3Si)2N]3Eu(μ-Cl)Li(THF)3 in toluene at 80℃ afforded a europium(Ⅱ) complex [η5:η1-Me2Si(Me2NCH2-CH2C9H5)(NHtBu)]2Eu·(OC4H8)0.5 (4) in 46% yield. The interaction of 2 equiv. of Me2NCH2CH2C9H6SiMe3 with [(Me3-Si)2N]3Eu(μ-Cl)Li(THF)3 produced a europium(Ⅱ) compound [η5:η1-(Me2NCH2CH2C9H5SiMe3)]2Eu (5) in 49% yield. Treatment of 2 equiv. of Me2NCH2CH2C9H7 with [(Me3Si)2N]3Eu(μ-Cl)Li(THF)3 in toluene gave a europium(Ⅱ) complex (η5:η1-Me2NCH2CH2C9H6)2Eu (6) in 57% yield. All the compounds were fully characterized by spectroscopic methods and elemental analyses. The structures of the complexes 4, 5, and 6 were determined by single-crystal X-ray analyses. The catalytic activities of organometallic complexes were examined; we found that all of the complexes can function as single-component MMA polymerization catalysts with good activity. We studied the effects of solvent and temperature on the catalytic activities and the stereochemistries of the polymers.