Bridged Bis(amidinate) Ytterbium Alkoxide and Phenoxide: Syntheses, Structures, and Their High Activity for Controlled Polymerization of l -Lactide and ε-Caprolactone
2008; American Chemical Society; Volume: 48; Issue: 2 Linguagem: Inglês
10.1021/ic801189j
ISSN1520-510X
AutoresJunfeng Wang, Yingming Yao, Yong Zhang, Qi Shen,
Tópico(s)Organometallic Complex Synthesis and Catalysis
ResumoBridged bis(amidinate) ytterbium alkoxide and phenoxide with diverse molecular structures were synthesized in high yields and confirmed by X-ray crystal structural analysis. The reaction of LYbCl(THF)2 (L = Me3SiNC(Ph)N(CH2)3NC(Ph)NSiMe3) with 1 equiv of NaOAr (ArO = 2,6-diisopropylphenoxo) afforded the mononuclear complex LYb(OAr)DME 1 with a seven-coordinated ytterbium atom surrrounded by one chelating bis(amidinate) ligand, one phenoxo group, and one DME (dimethoxyethane) molecule. The same reaction with 1 equiv of NaOiPr yielded the binuclear complex Yb(μ2-L)2(μ2-OiPr)2Yb, 2, with two equivalent six-coordinate metal centers connected by two linked bis(amidinate)s and two OiPr bridges formed via a ligand redistribution reaction that occurred during the metathesis reaction. Both 1 and 2 initiated the ring-opening polymerization of l-lactide, as well as ε-caprolactone (ε-CL), in a controlled manner with high reactivity, as indicated by a linear relationship between Mn and conversion and by narrow molecular weight distributions (PDI = 1.15−1.25) up to 100% conversion. The differences in catalytic performance between complexes 1 and 2 are discussed.
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