Two new indene compounds, C9H7CH2SiMe2NC4H8 (1) and C9H6-1-Me-3-CH2SiMe2NC4H8 (2), were synthesized by the reaction of C9H6RLi (R) H, Me) with ClCH2SiMe2Cl, followed by treatment with lithium pyrrolidinide C4H8NLi. The interaction of [(Me3Si)2N]3Eu(μ-Cl)-Li(THF)3 with 2 equiv of 1 in refluxing toluene produced, after workup, a novel triple-decker sandwich tetranuclear europium(Ⅱ) compound, [{η:5η:5η1-(C9H5CH2SiMe2NC4H8)2}Eu2(μ-Cl)]2-[μ-η3:η5:η1:η3:η5:η1-(C9H5CH2SiMe2NC4H8)2]âC7H8â(C6H6)0.5 (3), with a coupled indenyl ligand through tandem silylamine elimination, reduction of Eu3+ to Eu2+, and the C-C coupling reactions. To probe the formation pathway of complex 3, the interaction of C9H6-1-Me-3-CH2SiMe2NC4H8 (3) with [(Me3Si)2N]3Eu(μ-Cl)Li(THF)3 was studied. Treatment of [(Me3-Si)2N]3Eu(μ-Cl)Li(THF)3 with 2 equiv of 2 in refluxing toluene temperature or at 60℃ produced, after workup, a monomeric europium(Ⅱ) complex, (η5:η1-C9H5-1-Me-3-CH2SiMe2-NC4H8)2Eu (4), via tandem silylamine elimination/homolysis of the Eu-N bond reactions. The formation pathway for complex 3 was proposed. All the compounds were fully characterized by spectroscopic methods and elemental analyses, and the structures of complexes 3 and 4 were additionally determined by single-crystal X-ray diffraction analyses. It was found that complexes 3 and 4 can function as single-component MMA polymerization initiators, which represent the first examples of europium(Ⅱ) complexes as single-component MMA polymerization catalysts. The solvents and temperature effects' on the activities of the catalysts were also discussed.

Reaction of Me2Si(Me2NCH2CH2C9H6)Cl with 1 equiv of t-BuNHLi yielded Me2Si(Me2-NCH2CH2C9H6)(t-BuNH) (1). Treatment of Me2NCH2CH2C9H7 with 1 equiv of n-BuLi, followed by reaction with an excess of Me3SiCl, produced Me2NCH2CH2C9H6SiMe3 (2) in 9% yield. Interaction of YbCl3 with 3 equiv of (Me3Si)2NLi in THF, after workup, produced the tetracoordinate ytterbium(Ⅲ) amide [(Me3Si)2N]3YbⅢ　(μ-Cl)Li(THF)3 (3) in 85% yield. Treatment of 3 with 2 equiv of 1 gave the ytterbium(Ⅱ) complex [è5:è1-Me2Si(Me2NCH2-CH2C9H5)(t-BuNH)]2YbⅡ (4) in 58% yield via a reductive reaction. To get some insight into the reaction, several reactions were initiated to study the effects of the t-BuNH group, silyl group, and N,N-dimethylaminoethyl group of the indene compounds, effects of coordinate ClLi(THF)3 in 3, and temperature effect on the reductive reaction. Treatment of 3 with-equiv of 2 afforded (η5:η1-Me2NCH2CH2C9H5SiMe3)2YbII (5) in 52% yield. Interaction of 3 with 2 equiv of Me2NCH2CH2C9H7 produced a ytterbium(Ⅱ) complex (η5:η1-Me2NCH2-CH2C9H6)2YbⅡ (6) in 63% yield. Treatment of the ytterbium(Ⅲ) complex [(Me3Si)2N]3YbIII with 2 equiv of Me2NCH2CH2C9H7 also afforded the ytterbium(Ⅱ) complex (η5:η1-Me2NCH2-CH2C9H6)2YbII (6) in 62% yield, which provides an alternate method for the preparation of 6. Treatment of 3 with 2 equiv of indene(C9H8) produced the ytterbium(Ⅲ) complex (η5-C9H7)2YbIIIN(SiMe3)2 (7). Treatment of 3 with 1 equiv of 1,2-bis(indenyl)ethane also produced the ytterbium(Ⅲ) complex meso-[ethylenebis(è5-indenyl)ytterbiumⅢ bis(trimethylsily)amide ((EBI)YbIIIN(SiMe3)2) (8). All the compounds were fully characterized by spectroscopic methods and elemental analyses. Complexes 3, 4, 5, 6, and 8 were additionally characterized by a single-crystal X-ray diffraction study. The formation pathway for the ytterbium(Ⅱ) complexes is proposed. The study showed that ytterbuim(Ⅱ) complexes 4, 5, and 6 can function as single-component MMA polymerization catalysts with good activity.

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.

The interaction of methoxyethyl functionalized indene compounds (C9H6-1-R-3-CH2CH2OMe, R=t-BuNHSiMe(1), Me3Si (2), H (3)) with [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 (Ln=Yb (4), Eu (5)) produced a series of new ytterbium (Ⅱ) and europium (Ⅱ) complexes via tandem silylamine elimination/homolysis of the Ln-N (Ln=Yb, Eu) bond.Treatment of the lanthanide (Ⅱ) amides [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3 (Ln=Yb (4), Eu (5) with 2 equiv. of 1, 2and 3, respectively, produced, after workup, the ytterbium (Ⅱ) complexes [η5:η1-Me2Si(MeOCH2CH2C9H5)(NHBu-t)]2-YbII (6), (η5:η1-MeOCH2CH2C9H5SiMe3)2YbII (7), (η5:η1-MeOCH2CH2C9H6)2YbII (8) and the correspondingeuropium (Ⅱ) complexes [η5:η1-Me2Si(MeOCH2CH2C9H5)(NHBu-t)]2EuII (9), (η5:η1-MeOCH2CH2C9H5SiMe3)2EuII (10) and (η5:η1-MeOCH2CH2C9H6)2EuII (11) in moderate to good yield. In contrast, interaction of the corresponding indene compounds 1, 2 or 3 with the lanthanide amides [(Me3Si)2N]3Ln (Ln = Yb, Eu) was not observed, while addition of 0.5 equiv. of anhydrous LiCl to the corresponding reaction mixture produced, after workup, the corresponding ytterbium (Ⅱ) or europium (Ⅱ) complexes. All the new compounds were fully characterized by spectroscopic and elemental analyses. The structures of complexes 7, 9 and 10 were determined by single-crystal X-ray analyses. The catalytic activity of all the ytterbium (Ⅱ) and europium (Ⅱ) complexes on MMA polymerization was examined. It was found that all the ytterbium (Ⅱ) and europium (Ⅱ) complexes can function as single-component MMA polymerization catalysts. The temperature, solvent and ligand effects on the catalytic activity were studied.