碱土金属催化碳二亚胺硼氢化反应机理的理论研究
发布时间：2018-10-24 14:20
【摘要】：本文运用密度泛函理论(Density functional theory,DFT)算法,研究了β-二亚胺氢化碱土金属复合物催化碳二亚胺硼氢化反应的机理.计算结果表明,当使用镁复合物作为催化剂时,该反应催化循环中的活性催化物种为镁氢复合物.从镁氢复合物的生成开始,该反应经过碳氮双键插入镁-氢共价键,硼氮偶联成键,以及从硼到镁的氢负离子转移等步骤,从而再生镁氢复合物并释放产物.该反应的决速步为负氢原子从硼到镁的转移过程.此外,通过理论计算拓展预测了钙、锶等其他碱土金属复合物催化剂的反应机理.研究结果表明,和镁催化氢化反应不同,钙、锶参与反应的活性催化物种是碳二亚胺插入相应氢化金属复合物后所生成的对应的氨基金属络合物.以此化合物作为催化循环的开始,反应经历硼氮偶联成键后,可直接与碳二亚胺发生硼碳之间的氢转移,得到产物并再生活性催化物种.钙、锶复合物作为催化剂时经历不同反应机理的原因是,它们的原子半径远远大于镁,因此可以与额外的碳二亚胺结合,并发生协同氢转移反应.理论计算表明,当使用钙、锶复合物作为催化剂时,反应决速步活化能低于镁催化的反应途径.因此,如果使用钙、锶复合物作为催化剂将会获得更温和的反应条件.
[Abstract]:The mechanism of hydrogenation of carbodiimide catalyzed by 尾 -diimide alkali-earth metal complex was studied by using density functional theory (Density functional theory,DFT) algorithm. The results show that when magnesium complex is used as catalyst, the active catalytic species in the reaction cycle is magnesium hydrogen complex. Starting with the formation of the magnesia-hydrogen complex, the reaction can regenerate the magnesia-hydrogen complex and release the product by inserting magnesia-hydrogen covalent bond, boron-nitrogen coupling bond and hydrogen negative ion transfer from boron to magnesium. The final step of the reaction is the transfer of negative hydrogen atoms from boron to magnesium. In addition, the reaction mechanism of other alkali earth metal complex catalysts such as calcium, strontium and so on was predicted by theoretical calculation. The results show that, unlike magnesium catalyzed hydrogenation, the active catalytic species involved in the reaction of calcium and strontium are the corresponding amino metal complexes formed by the insertion of carbodiimide into the corresponding hydrogenated metal complexes. As the beginning of the catalytic cycle, the reaction can directly transfer the hydrogen between boron and carbon with carbon diimide after boron-nitrogen coupling bond, and obtain the product and regenerate the active catalytic species. The reason for the different reaction mechanisms of calcium and strontium complexes as catalysts is that their atomic radius is much larger than that of magnesium, so they can combine with extra carbodiimide and have a synergistic hydrogen transfer reaction. The theoretical calculation shows that the activation energy of reaction speed step is lower than that of magnesium catalyst when calcium and strontium complexes are used as catalysts. Therefore, if calcium and strontium complexes are used as catalysts, more mild reaction conditions will be obtained.
【作者单位】： 重庆大学化学化工学院;
【基金】：国家自然科学基金(No.21372266)资助项目~~
【分类号】：O621.251
[Abstract]:The mechanism of hydrogenation of carbodiimide catalyzed by 尾 -diimide alkali-earth metal complex was studied by using density functional theory (Density functional theory,DFT) algorithm. The results show that when magnesium complex is used as catalyst, the active catalytic species in the reaction cycle is magnesium hydrogen complex. Starting with the formation of the magnesia-hydrogen complex, the reaction can regenerate the magnesia-hydrogen complex and release the product by inserting magnesia-hydrogen covalent bond, boron-nitrogen coupling bond and hydrogen negative ion transfer from boron to magnesium. The final step of the reaction is the transfer of negative hydrogen atoms from boron to magnesium. In addition, the reaction mechanism of other alkali earth metal complex catalysts such as calcium, strontium and so on was predicted by theoretical calculation. The results show that, unlike magnesium catalyzed hydrogenation, the active catalytic species involved in the reaction of calcium and strontium are the corresponding amino metal complexes formed by the insertion of carbodiimide into the corresponding hydrogenated metal complexes. As the beginning of the catalytic cycle, the reaction can directly transfer the hydrogen between boron and carbon with carbon diimide after boron-nitrogen coupling bond, and obtain the product and regenerate the active catalytic species. The reason for the different reaction mechanisms of calcium and strontium complexes as catalysts is that their atomic radius is much larger than that of magnesium, so they can combine with extra carbodiimide and have a synergistic hydrogen transfer reaction. The theoretical calculation shows that the activation energy of reaction speed step is lower than that of magnesium catalyst when calcium and strontium complexes are used as catalysts. Therefore, if calcium and strontium complexes are used as catalysts, more mild reaction conditions will be obtained.
【作者单位】： 重庆大学化学化工学院;
【基金】：国家自然科学基金(No.21372266)资助项目~~
【分类号】：O621.251
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