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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Magnesium complexes containing biphenyl-based tridentate imino-phenolate ligands for ringopening polymerization of rac-lactide and α-methyltrimethylene carbonate?
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Magnesium complexes containing biphenyl-based tridentate imino-phenolate ligands for ringopening polymerization of rac-lactide and α-methyltrimethylene carbonate?

机译：含联苯基三齿亚氨基-酚酸酯配体的镁配合物，用于外消旋丙交酯和α-甲基三亚甲基碳酸酯的开环聚合反应？

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摘要

A series of racemic 2-[(2'-(dimethylamino)biphenyl-2-ylimino)methyl]-4-R2-6-R1-phenols (L~1H-L~4H) were reacted with {Mg[N(SiMe3)2]2}2 to provide four heteroleptic magnesium complexes (L~(1-4))MgN- (SiMe_3)_2·(THF)_n (1, R~1 = ~tBu, R~2 = Me, n = 1; 2, R~1 = R~2 = CMe_2Ph, n = 0; 3, R~1 = CPh_3, R~2 = ~tBu, n = 1; 4, R1 = Br, R~2 = ~tBu, n = 0), which have been fully characterized. X-ray structural determination shows that complex 1 possesses a monomeric structure, but complex 4 is dimeric with C2-symmetry where the two metal centers are bridged by two phenolate oxygen atoms of the ligands. The coordination geometry around the magnesium center in these complexes can be best described as a distorted tetrahedral geometry. The heteroleptic complexes 1-4 efficiently initiate the ring-opening polymerization of rac-lactide and α-methyltrimethylene carbonate (α-MeTMC) and the polymerizations are better controlled in the presence of 2-propanol. In general, the introduction of a bulky ortho-substituent on the phenoxy unit results in increases of both the catalytic activity and the stereo- or regioselectivity of the corresponding magnesium complex. Microstructure analyses of the resulting PLAs revealed that Pr values range from 0.46 to 0.81, depending on the catalyst and the polymerization conditions. For racemic α-MeTMC, detailed analyses using ~1H and ~(13)C NMR spectroscopy indicated the preferential ring-opening of α-MeTMC at the most hindered oxygen-acyl bond (X_(reg) = 0.65-0.86).
机译：一系列外消旋的2-[（（2'-（二甲基氨基）联苯-2-嘧啶）甲基] -4-R2-6-R1-苯酚（L〜1H-L〜4H）与{Mg [N（SiMe3 ）2] 2} 2提供四个杂配镁配合物（L〜（1-4））MgN-（SiMe_3）_2·（THF）_n（1，R〜1 =〜tBu，R〜2 = Me，n = 1; 2，R〜1 = R〜2 = CMe_2Ph，n = 0; 3，R〜1 = CPh_3，R〜2 =〜tBu，n = 1; 4，R1 = Br，R〜2 =〜tBu， n = 0），这已被充分表征。 X射线结构测定表明配合物1具有单体结构，但是配合物4是具有C 2对称性的二聚体，其中两个金属中心被配体的两个酚盐氧原子桥接。这些配合物中镁中心周围的配位几何可以最好地描述为扭曲的四面体几何。杂合配合物1-4有效地引发外消旋丙交酯和α-甲基三亚甲基碳酸酯（α-MeTMC）的开环聚合，并且在2-丙醇的存在下更好地控制了聚合。通常，在苯氧基单元上引入大体积的正取代基导致相应镁配合物的催化活性和立体或区域选择性的增加。所得PLA的微结构分析显示，取决于催化剂和聚合条件，Pr值在0.46至0.81的范围内。对于外消旋α-MeTMC，使用〜1H和〜（13）C NMR光谱进行的详细分析表明，α-MeTMC在最受阻的氧-酰基键处优先开环（X_（reg）= 0.65-0.86）。

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