کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1324448 | 1499827 | 2016 | 9 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Lanthanide alkoxide complexes stabilized by a novel salen-type Schiff-base ligand: Synthesis, structure, and catalysis for the polymerization of lactide Lanthanide alkoxide complexes stabilized by a novel salen-type Schiff-base ligand: Synthesis, structure, and catalysis for the polymerization of lactide](/preview/png/1324448.png)
• Synthesis of six new lanthanide complexes stabilized by a novel salen-type Schiff-base ligand.
• All lanthanide alkoxide complexes can efficiently initiate the ring-opening polymerization (ROP) of L-LA and rac-LA.
• The first-order kinetic dependence on both l-lactide concentration and initiator concentration was found.
A series of neutral lanthanide alkoxide complexes stabilized by a new salen-type Schiff-base ligand were synthesized, and their catalytic behaviors for the ring-opening polymerization of lactide were explored. Amine elimination reactions of N-methyl-N′,N″-bis(3,5-di-tert-butylsalicylidene)-2,2′-diaminodiethylamine (LH2) with Ln[N(SiMe3)2]3 (Ln = Sm, Nd, La) in a 1:1 M ratio in THF, followed by reactions with 1 equiv of alcohols (tBuOH, EtOH and CH3OCH2CH2OH), produced lanthanide alkoxide complexes LLn(OtBu)(THF) (Ln = Sm (1), Nd (2), La (3)), [LSm(μ-OEt)]2 (4) and [LSm(μ-OCH2CH2OCH3)]2 (5), respectively, whereas the same reaction with Yb[N(SiMe3)2]3 gave an unexpected homoleptic complex L2Yb2(μ-L) (6). X-ray structural determination showed that complexes 1–3 have a THF-solvated monomeric structure, whereas complexes 4–6 have an unsolvated dimeric structure. All lanthanide alkoxide complexes can efficiently initiate the ring-opening polymerization (ROP) of L-LA and rac-LA. The polymerization kinetics of L-LA initiated by complex 1 has been studied in detail and the first-order kinetic dependence on both l-lactide concentration and initiator concentration was found. Furthermore, all complexes showed moderate stereoselectivity for rac-LA polymerization to afford heterotactic-rich polylactides.
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Journal: Journal of Organometallic Chemistry - Volume 819, 15 September 2016, Pages 37–45