Formation of dianionic 2,2′-bipyridyl-bridged dinuclear yttrium complexes proceeded upon treatment of (ArNCH2CH2NAr)Y(CH2SiMe3)(THF)2 with 2-arylpyridine, in which mononuclear (2-pyridylphenyl)yttrium complexes were detected as key intermediates.
Alkyl Complexes of Rare-Earth Metal Centers Supported by Chelating 1,1′-Diamidoferrocene Ligands: Synthesis, Structure, and Application in Methacrylate Polymerization
作者:Jörg Eppinger、Katharina R. Nikolaides、Mei Zhang-Presse、Florian A. Riederer、Gerd W. Rabe、Arnold L. Rheingold
DOI:10.1021/om700988n
日期:2008.2.1
Conversion of 1,1'-dianilinoferrocenes of the composition [3,4-R2C5H2(NHPh)](2)Fe (R = H, Ph) with 1 equiv of the rare-earth metal alkyl precursors Ln(THF)(2)(CH2SiMe3)(3) (Ln = Lu, Y) affords [R(4)Fc(NPh)(2)]Ln(THF)(2)CH2SiMe3 (1a-2b) in yields of 73-83%. The steric bulk of the ferrocene moiety induces a pronounced stabilization of the complexes in comparison to alkyl-bridged analogues. Correspondingly, the complexes 1a-2b are stable in solution at room temperature and were characterized by multinuclear NMR spectroscopy and elemental analysis. A single-crystal X-ray diffraction study was performed for complex 2b. The synthesized rare-earth metal alkyls embedded into a 1,1'-diamidoferrocene framework effectively initiate the polymerization of methyl methacrylate (MMA) at room temperature, producing isotactic enriched poly(methyl methacrylate) (PMMA). The properties of the produced PMMAs are mainly governed by the substitution patterns of the ferrocenyl backbone.