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Mono-BHT heteroleptic magnesium complexes: synthesis, molecular structure and catalytic behavior in the ring-opening polymerization of cyclic esters
Dalton Transactions ( IF 3.5 ) Pub Date : 2017-08-29 00:00:00 , DOI: 10.1039/c7dt02469j I. E. Nifant'ev 1, 2, 3, 4, 5 , A. V. Shlyakhtin 1, 2, 3, 4 , V. V. Bagrov 1, 2, 3, 4 , M. E. Minyaev 3, 4, 5, 6 , A. V. Churakov 3, 4, 6, 7 , S. G. Karchevsky 4, 8, 9 , K. P. Birin 3, 4, 6, 10 , P. V. Ivchenko 1, 2, 3, 4, 5
Dalton Transactions ( IF 3.5 ) Pub Date : 2017-08-29 00:00:00 , DOI: 10.1039/c7dt02469j I. E. Nifant'ev 1, 2, 3, 4, 5 , A. V. Shlyakhtin 1, 2, 3, 4 , V. V. Bagrov 1, 2, 3, 4 , M. E. Minyaev 3, 4, 5, 6 , A. V. Churakov 3, 4, 6, 7 , S. G. Karchevsky 4, 8, 9 , K. P. Birin 3, 4, 6, 10 , P. V. Ivchenko 1, 2, 3, 4, 5
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Numerous heteroleptic 2,6-di-tert-butyl-4-methylphenolate (BHT) magnesium complexes have been synthesized by treatment of (BHT)MgBu(THF)2 with various alcohols. Molecular structures of the complexes have been determined by X-ray diffraction. The magnesium coordination number in [(BHT)Mg(μ-OBn)(THF)]2 (3) and [(BHT)Mg(μ-O-tert-BuC6H4)(THF)]2 (4) is equal to 4. Complexes formed from esters of glycolic and lactic acids, [(BHT)Mg(μ-OCH2COOEt)(THF)]2 (5) and [(BHT)Mg(μ-OCH(CH3)COOCH2COOtBu)(THF)]2 (6) contain chelate fragments with pentacoordinated magnesium. Compounds 3–6 contain THF molecules coordinated to magnesium atoms. Complex {(BHT)Mg[μ-O(CH2)3CON(CH3)2]}2 (7) does not demonstrate any tendency to form an adduct with THF. It has been experimentally determined that complexes 3 and 5 are highly active catalysts of lactide polymerization. The activity of 4 is rather low, and complex 7 demonstrates moderate productivity. According to DOSY NMR experiments, compounds 3 and 5 retain their dimeric structures even in THF. The free energies of model dimeric [(DBP)Mg(μ-OMe)(Sub)]2 and monomeric (DBP)Mg(OMe)(Sub)2 products on treatment of [(DBP)Mg(μ-OMe)(THF)]2 with a series of σ-electron donors (Sub) have been estimated by DFT calculations. These results demonstrate that the substitution of THF by Sub in a dimeric molecule is an energetically allowed process, whereas the dissociation of dimers is energetically unfavorable. DFT modeling of ε-CL and (DL)-lactide ROP catalyzed by dimeric and monomeric complexes showed that a cooperative effect of two magnesium atoms occurs within the ROP for binuclear catalytic species. A comparison of the reaction profiles for ROP catalyzed by binuclear and mononuclear species allowed us to conclude that the binuclear mechanism is favorable in early stages of ROP initiated by dimers 3 and 5.
中文翻译：
单BHT杂配镁配合物：环酯开环聚合中的合成，分子结构和催化行为
通过用各种醇处理（BHT）MgBu（THF）2已经合成了许多杂合的2,6-二叔丁基-4-甲基苯酚镁（BHT）镁配合物。配合物的分子结构已经通过X射线衍射确定。[（BHT）Mg（μ-OBn）（THF）] 2（3）和[（BHT）Mg（μ-O-叔-BuC 6 H 4）（THF）] 2（4）中的镁配位数为等于从乙醇酸和乳酸酯形成配合物4，[（BHT）的Mg（μ-OCH 2 COOEt烷基）（THF）] 2（5）和[（BHT）的Mg（μ-OCH（CH 3）COOCH 2COO t Bu）（THF）] 2（6）含有带有五配位镁的螯合物碎片。化合物3–6包含与镁原子配位的THF分子。络合物{（BHT）Mg [μ-O（CH 2）3 CON（CH 3）2 ]} 2（7）没有显示出与THF形成加合物的任何趋势。已经通过实验确定了配合物3和5是丙交酯聚合的高活性催化剂。4的活动相当低，并且复杂7表现出中等生产力。根据DOSY NMR实验，化合物3和5甚至在THF中也保持其二聚体结构。模型二聚体[（DBP）Mg（μ-OMe）（Sub）] 2和单体（DBP）Mg（OMe）（Sub）2产物在处理[（DBP）Mg（μ-OMe）（THF）时的自由能）] 2与一系列σ的电子供体（副）通过DFT计算已估计的。这些结果表明，二聚体分子中的Sub取代THF是从能量上允许的过程，而二聚体的离解在能量上是不利的。ε-CL和（DL的DFT建模二聚体和单体配合物催化的1）-丙交酯ROP表明，对于双核催化物质，ROP内会发生两个镁原子的协同作用。比较双核和单核物种催化的ROP反应谱可以使我们得出结论，双核机制在二聚体3和5引发的ROP早期是有利的。
更新日期：2017-09-20
中文翻译：
单BHT杂配镁配合物：环酯开环聚合中的合成，分子结构和催化行为
通过用各种醇处理（BHT）MgBu（THF）2已经合成了许多杂合的2,6-二叔丁基-4-甲基苯酚镁（BHT）镁配合物。配合物的分子结构已经通过X射线衍射确定。[（BHT）Mg（μ-OBn）（THF）] 2（3）和[（BHT）Mg（μ-O-叔-BuC 6 H 4）（THF）] 2（4）中的镁配位数为等于从乙醇酸和乳酸酯形成配合物4，[（BHT）的Mg（μ-OCH 2 COOEt烷基）（THF）] 2（5）和[（BHT）的Mg（μ-OCH（CH 3）COOCH 2COO t Bu）（THF）] 2（6）含有带有五配位镁的螯合物碎片。化合物3–6包含与镁原子配位的THF分子。络合物{（BHT）Mg [μ-O（CH 2）3 CON（CH 3）2 ]} 2（7）没有显示出与THF形成加合物的任何趋势。已经通过实验确定了配合物3和5是丙交酯聚合的高活性催化剂。4的活动相当低，并且复杂7表现出中等生产力。根据DOSY NMR实验，化合物3和5甚至在THF中也保持其二聚体结构。模型二聚体[（DBP）Mg（μ-OMe）（Sub）] 2和单体（DBP）Mg（OMe）（Sub）2产物在处理[（DBP）Mg（μ-OMe）（THF）时的自由能）] 2与一系列σ的电子供体（副）通过DFT计算已估计的。这些结果表明，二聚体分子中的Sub取代THF是从能量上允许的过程，而二聚体的离解在能量上是不利的。ε-CL和（DL的DFT建模二聚体和单体配合物催化的1）-丙交酯ROP表明，对于双核催化物质，ROP内会发生两个镁原子的协同作用。比较双核和单核物种催化的ROP反应谱可以使我们得出结论，双核机制在二聚体3和5引发的ROP早期是有利的。
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