title: Controlled synthesis of mononuclear or binuclear aryloxo ytterbium complexes supported by beta-diketiminate ligand and their activity for polymerization of epsilon-caprolactone and L-lactide.
abstract: The reaction of monomeric [(DIPPh)(2)nacnac]YbCl(2)(THF)(2) ((DIPPh)(2)nacnac = N,N-diisopropylphenyl-2,4-pentanediimineanion) with NaOAr (OAr = 2,6-diisopropylphenoxide) in THF afforded the mononuclear complexes [(DIPPh)(2)nacnac]Yb(OAr)Cl(THF) 1 and [(DIPPh)(2)nacnac]Yb(OAr)(2) 2 depending on the molar ratio of dichloride to sodium salt, while the same reaction with NaOAr' (OAr' = 2,6-dimethylphenoxide) in toluene yielded the binuclear complex [{(DIPPh)(2)nacnac}Yb(OAr')](2)(mu-Cl)(2) 3. Treatment of [(DIPPh)(2)nacnac]Yb(THF)(mu-Cl)(3)Yb(Cl)[(DIPPh)(2)nacnac] with NaOAr and NaOAr', respectively, in toluene yielded selectively the corresponding binuclear complexes {[(DIPPh)(2)nacnac]Yb(OAr)(mu-Cl)(3)Yb[(DIPPh)(2)nacnac](THF)} 4 and {[(DIPPh)(2)nacnac]Yb(OAr')(mu-Cl)(3)Yb[(DIPPh)(2)nacnac](THF)} 5 in high yields. All complexes were structurally characterized. Complex 2 was found to be a highly active initiator for both polymerizations of epsilon-caprolactone (epsilon-CL) and L-lactide. All monoaryloxide complexes can initiate the polymerization of epsilon-CL in a controlled manner giving polymers with narrow molecular weight distributions (M(w)/M(n) around 1.06) with relatively low activity relative to complex 2.
authors.affiliation: Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou, 215123, People's Republic of China.
authors.forename: Hongxia
authors.initials: H
authors.lastname: Chen
authors.forename: Peng
authors.initials: P
authors.lastname: Liu
authors.forename: Haisheng
authors.initials: H
authors.lastname: Yao
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yingming
authors.initials: Y
authors.lastname: Yao
authors.forename: Qi
authors.initials: Q
authors.lastname: Shen