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首页> 外文期刊>Catalysis science & technology >Exploring the versatility of a bis(phosphinimine) pincer ligand: effect of sterics on structure and lactide polymerization activity of cationic zinc complexes
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Exploring the versatility of a bis(phosphinimine) pincer ligand: effect of sterics on structure and lactide polymerization activity of cationic zinc complexes

机译：探索双（磷化亚胺）钳子配体的多功能性：集体对阳离子锌复合物的结构和乳酸聚合活性的影响

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摘要

Cationic zinc complexes of a neutral pincer framework 4,6-(ArN=PPh2)-dibenzofuran (L~1: Ar = 2-~iPrPh; L~2: Ar = o-tolyl; L~3: Ar = Ph), have been prepared and characterized. Crystallographic and NMR studies of the methylzinc complexes [LZnCH_3~+][BAr_4~-] (4a-6a: Ar = m-(CF3)2-C6H3; 4b-6b: Ar = Ph) demonstrated that the steric demands of the ligand dramatically affect the solid-state geometry. The cationic zinc-lactate complexes [LZnOR~+][B(m-(CF3)2-C6H3)_4~-] (7: L = L~2; 8: L = L~3; R = CH(Me)CO2Me) were also studied, and their efficacy as lactide polymerization catalysts was examined. Polymerization using 7 requires heating to 60 °C, while complex 8 displays high activity at ambient temperature. The difference in activity can be attributed to k~2 versus k~3 binding modes of the ligand, providing important insight into structure-activity relationships for this system. Complex 8 gives modestly heteroenriched PLA (P_r = 0.70), which represents the best stereocontrol yet achieved by a cationic metal catalyst.
机译：中性钳子框架的阳离子锌配合物4,6-（arn = pph2）-dibenzofuran（l〜1：ar = 2-〜iprph; l〜2：ar = o-tolyl; l〜3：ar = pH），已经准备好并表征了。甲基津络合物的晶体学和NMR研究[lznch_3〜+] [bar_4〜-]（4a-6a：ar = m-（cf3）2-c6h3; 4b-6b：ar = pH）证明了配体的空间需求极大地影响固态几何形状。阳离子锌乳酸复合物[lznor〜+] [B（m-（cf3）2-C6H3）_4〜-]（7：l = l〜2; 8：l = l〜3; r = ch（me）还研究了CO2ME），并检查了它们作为乳酸聚合催化剂的功效。使用7的聚合需要加热至60°C，而复合物8在环境温度下显示高活性。活性的差异可以归因于K〜2与配体的K〜3结合模式，从而为该系统提供了对结构 - 活性关系的重要见解。复合物8给出了适度的杂烯基PLA（P_R = 0.70），它代表了阳离子金属催化剂迄今为止最佳的立体控制。

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