Alhashmialameer Dalal, Ikpo Nduka, Collins Julie, Dawe Louise N, Hattenhauer Karen, Kerton Francesca M
Department of Chemistry, Memorial University of Newfoundland, St. John's, Newfoundland, Canada A1B 3X7.
C-CART X-ray Diffraction Laboratory, Memorial University of Newfoundland, St. John's, Newfoundland, Canada.
Dalton Trans. 2015 Dec 14;44(46):20216-31. doi: 10.1039/c5dt03119b.
Lithium and sodium compounds supported by tetradentate amino-bis(phenolato) ligands, [Li2(N2O2(BuBuPip))] (1), [Na2(N2O2(BuBuPip))] (2) (where [N2O2(BuBuPip)] = 2,2'-N,N'-homopiperazinyl-bis(2-methylene-4,6-tert-butylphenol), and [Li2(N2O2(BuMePip))] (3), [Na2(N2O2(BuMePip))] (4) (where [N2O2(BuMePip)] = 2,2'-N,N'-homopiperazinyl-bis(2-methylene-4-methyl-6-tert-butylphenol) were synthesized and characterized by NMR spectroscopy and MALDI-TOF mass spectrometry. Variable temperature NMR experiments were performed to understand solution-phase dynamics. The solid-state structures of 1 and 4 were determined by X-ray diffraction and reveal tetrametallic species. PGSE NMR spectroscopic data suggests that 1 maintains its aggregated structure in CD2Cl2. The complexes exhibit good activity for controlled ring-opening polymerization of rac-lactide (LA) both solvent free and in solution to yield PLA with low dispersities. Stoichiometric reactions suggest that the formation of PLA may proceed by the typical coordination-insertion mechanism. For example, (7)Li NMR experiments show growth of a new resonance when 1 is mixed with 1 equiv. LA and (1)H NMR data suggests formation of a Li-alkoxide species upon reaction of 1 with BnOH.
由四齿氨基双（酚盐）配体支撑的锂和钠化合物，[Li₂(N₂O₂(BuBuPip))] (1)、[Na₂(N₂O₂(BuBuPip))] (2)（其中[N₂O₂(BuBuPip)] = 2,2'-N,N'-高哌嗪基双(2-亚甲基-4,6-叔丁基苯酚)）以及[Li₂(N₂O₂(BuMePip))] (3)、[Na₂(N₂O₂(BuMePip))] (4)（其中[N₂O₂(BuMePip)] = 2,2'-N,N'-高哌嗪基双(2-亚甲基-4-甲基-6-叔丁基苯酚)）通过核磁共振光谱和基质辅助激光解吸电离飞行时间质谱法进行了合成与表征。进行了变温核磁共振实验以了解溶液相动力学。通过X射线衍射确定了1和4的固态结构，揭示出四金属物种。脉冲梯度自旋回波核磁共振光谱数据表明1在CD₂Cl₂中保持其聚集结构。这些配合物在无溶剂和溶液中对消旋丙交酯（LA）的可控开环聚合均表现出良好活性，可得到低分散度的聚乳酸（PLA）。化学计量反应表明PLA的形成可能通过典型的配位插入机理进行。例如，(⁷)Li核磁共振实验表明，当1与1当量的LA混合时会出现一个新共振峰的增长，并且(¹)H核磁共振数据表明1与苄醇反应时会形成锂醇盐物种。
