| A series of tetracoordinate lanthanide(Ⅲ) amides [(Me3Si)2N]3Ln (μ-Cl)Li(THF)3.xC7H8( Ln = Nd(1), Sm(2), Eu(3), x = 0; Ln = Tm(4), x = 1 ) were synthesized under a dry and oxygen-free argon atmosphere by using standard Schlenk techniques. These complexes were active for the MMA polymerization except for complex 4. It was found that the solvents, temperature, ionics radius and the catalyst/momoner ratios have influenes on the molecules weight and stereogularities of PMMA.Reaction of ClCH2CH2CH2NMe2 with 1 equiv of C9H7Li in THF gave C9H7CH2CH2CH2NMe2(5); Interaction of C9H7Li with 1 equiv of ClCH2SiMe2Cl in THF produced C9H7-3-CH2SiMe2Cl(6); Treatment of compound 6 with 1 equiv of C4H8NLi in THF at 50℃ yieded C9H7-1-CH2SiMe2NC4H8(7); The similar reaction of MeC9HLi with 1 equiv of ClCH2SiMe2Cl in THF produced C9H7-1-Me-3-CH2SiMe2Cl(8); Treatment of compound 8 with 1 equiv of C4H8NLi in THF at 50℃ yieded C9H-1-CH2SiMe2NC4H8(9). Reactions of the three substituted indenyl compounds 5, 7, 9 with [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3(Ln = Yb, Eu) were studied. Interactions of [(Me3Si)2N]3Ln(μ-Cl)Li(THF)3(Ln = Yb, Eu) with 2 equiv of compound 5 in toluene gave (η5:η1-C9H6CH2CH2CH2 NMe2)2Yb(10) and (η5:η1-C9H6CH2CH2CH2NMe2)2Eu(11). The similar reactions of [(Me3Si)2N]3Ln (μ-Cl)Li(THF)3(Ln = Yb, Eu) with 2 equiv of compound 5 in refluxed toluene, followed by recrystallization from toluene, yielded the corresponding organolanthanide(Ⅱ) complexes (η5:η1-C9H6 CH2SiMe2NC4H8)2Yb(12) and {[η5:η5:η1-(C9H5CH2SiMe2NC4H8)2]Eu2(μ-Cl)}[μ-η5:η5:η1:η5:η3:η1-(C9H5CH2SiMe2NC4H8)2]·C7H8·(C6H6)0.5(13). The analogous reaction of complexes 3 with 2 equiv of compound 9 in toluene at 60℃, produced the europium(Ⅱ) complex (η5:η1-C9H5-1-Me-3-CH2SiMe2NC4H8)2Eu (14), which were recrystallized from a mixed solvent of toluene and THF (10:1). Treatment of 2 with 1 equiv of (CH2)2(C9H6)(C9H6) in refluxed toluene produced, after recrystallization from hexane, the samarium(Ⅲ) complex (CH2)2(C9H6)(C9H6)SmN(SiMe3)2(15). All the complexes were fully characterized by elemental and spectroscopic analyses. The structures of complexes 2 4, 12 15 were determined by X-ray diffraction.The above experimental results demonstrated the mechanism of heteroatom coordination promoted homolysis of Ln-N bond to afford the lanthanide(Ⅱ) complexes. The formation of complexes 13, a triple-decker structure, was due to coupling of [C9H6CH2SiMe2NC4H8]. which was derived from the capture of hydrogen of C9HCH2SiMe2NC4H8(7) by the radical [(Me3Si)2N]. in the process of reaction. The results indicated that steric hindrance of ligands affected homolytic reaction of the Ln-N bond. The activities of complexes 10, 11, 12, 13 and 14 as single-component catalysts in catalyzing MMA polymerization were examined. It was found that the activities of the catalysts, stereo-regularity of PMMA, and the molecular weight of polymers were dependent on the solvents, temperature and the catalyst/MMA mole ratios.
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