Chloroyttrium 2-(1-(Arylimino)alkyl)quinolin-8-olate Complexes: Synthesis, Characterization, and Catalysis of the Ring-Opening Polymerization of 蔚-Caprolactone

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• 作者：Wenjuan Zhang ; Shaofeng Liu ; Wenhong Yang ; Xiang Hao ; Rainer Glaser ; Wen-Hua Sun
• 刊名：Organometallics
• 出版年：2012
• 出版时间：December 10, 2012
• 年：2012
• 卷：31
• 期：23
• 页码：8178-8188
• 全文大小：493K
• 年卷期：v.31,no.23(December 10, 2012)
• ISSN：1520-6041

文摘

Stoichiometric reactions of YCl₃(THF)₃ with potassium 2-((arylimino)methyl)quinolin-8-olates or 2-(1-(arylimino)ethyl)quinolin-8-olates in THF solution gave the mononuclear LYCl₂(DMSO)₂ complexes 1鈥?b>5 in the presence of DMSO and a representative dinuclear complex 6 in the absence of DMSO. All yttrium complexes were fully characterized by NMR measurements and elemental analysis, and the crystal structures of complexes 1 and 4鈥?b>6 were determined by single-crystal X-ray diffraction. The structures indicate coordination number seven around the yttrium center and pentagonal bipyramidal geometries. The complexes all feature diapical YCl₂ moieties and one tridentate organic ligand in the equatorial plane. Upon reaction of the yttrium precatalysts 1鈥?b>6 with LiCH₂Si(CH₃)₃ alone or with LiCH₂Si(CH₃)₃ together with BnOH, the ring-opening polymerization (ROP) of 蔚-caprolactone (蔚-CL) occurred with high efficiency. Depending on conditions, the ROP of 蔚-CL produced polycaprolactone with narrow molecular distribution and in a living manner. Theoretical studies of the chlorine/CH₂SiMe₃ and Me₃SiCH₂/BnO ligand exchange reactions suggest that the replacement of the apical ligands can proceed without significantly affecting the equatorial ligands. These results suggest that one of the apical Y鈥揅H₂SiMe₃ bonds within the LY(CH₂SiMe₃)₂ intermediate catalyzes the polymerization in the BnOH-free process. Most polymers generated by BnOH-assisted catalysis possess M_n values that are similar to M_n,cal values based on Y鈥揙Bn, suggesting that one apical Y鈥揙Bn bond of the diapical LY(OBn)(CH₂SiMe₃) intermediate catalyzes most or all of the ring polymerization of 蔚-CL.