Lithium complexes supported by amine bis-phenolate ligands as efficient catalysts for ring-opening polymerization of l-lactide†‡
Abstract
Lithium complexes bearing dianionic amine bis(phenolate) ligands are described. Reactions of ligand precursors H2O2NNMe, H2O2NNPy or H2O2NOMe [H2O2NNMe = Me2NCH2CH2N-(CH2-2-HO-3,5-C6H2(tBu)2)2; H2O2NNPy = (2-C5H4N)CH2N-(CH2-2-HO-3,5-C6H2(tBu)2)2; H2O2NOMe = MeOCH2CH2N-(CH2-2-HO-3,5-C6H2(tBu)2)2] with 2.2 molar equivalents of nBuLi in diethylether afford (Li2O2NNMe)2 (1), (Li2O2NNPy)2 (2) and (Li2O2NOMe)2 (3) as tetra-nuclear lithium complexes. The crystalline solids of partially hydrolyzed product, (LiO(HO)NNPy) (4), were obtained from recrystallization of 2 in diethylether solution for three months. The synthesis of (LiO(HO)NOMe)2 (5) was carried out at ambient temperature by carefully layering a solution of
- This article is part of the themed collection: Emerging strategies in catalysis