Rare earth metal alkyl complexes bearing N,O,P multidentate ligands: Synthesis, characterization and catalysis on the ring-opening polymerization of L-lactide
作者：Miao, W; Li, SH; Cui, DM; Huang, BT
關(guān)鍵字：rare earth metal; alkyl complex; multidentate; lactide
論文來源：期刊
具體來源：http://apps.webofknowledge.com/full_record.do?product=UA&search_mode=GeneralSearch&qid=13&SID=V2hxdX
發(fā)表時間：2010年
Alkane
elimination reactions of rare earth metal tris(alkyl)s,
Ln(CH2SiMe3)3(THF)2 (Ln = Y, Lu) with the multidentate ligands HL1-4, afforded
a series of new rare earth metal complexes. Yttrium,
complex I supported by flexible amino-intino phenoxide ligand HL1 was isolated
as homoleptic product. In the reaction of rigid phosphino-imino phenoxide
ligand HL 2 with equintolar Ln(CH2SiMe3)3(THF)2, HL 2 was deprotonated by the metal alkyl and
its imino C=N group was reduced to C-N by intramolecular alkylation, generating
THF-solvated mono-alkyl complexes (2a: Ln = Y; 2b: Ln = Lu). The
di-ligand chelated yttriurn complex 3 without alkyl moiety was
isolated when the molar ratio of HL 2 to Y(CH,SiMe3)3(THF)2 increased to 2: 1.
Reaction of steric phosphino beta-ketoiminato ligand HL 3 with equimolar
Ln(CH2SiMe3)3(THF)2 afforded di-ligated mono-alkyl complexes (4a: Ln
= Y; 4b: Ln = Lu) without occurrence of intramolecular alkylation or formation
of homoleptic product. Treatment of tetradentate methoxy-amino phenol HL 4 with
Y(CH2SiMe3)3(THF)2 afforded a monomeric yttrium bis-alkyl complex of
THF-free. The resultant complexes were characterized by IR, NMR
spectrum and X-ray diffraction analyses. All alkyl complexes exhibited
high activity toward the ring-opening polymerization Of L-lactide to give
isotactic polylactide with controllable molecular weight and narrow to moderate
polydispersity. (c) 2007 Elsevier B.V. All rights reserved.