【摘要】：本文運用密度泛函理論(Density functional theory,DFT)算法,研究了β-二亞胺氫化堿土金屬復(fù)合物催化碳二亞胺硼氫化反應(yīng)的機理.計算結(jié)果表明,當(dāng)使用鎂復(fù)合物作為催化劑時,該反應(yīng)催化循環(huán)中的活性催化物種為鎂氫復(fù)合物.從鎂氫復(fù)合物的生成開始,該反應(yīng)經(jīng)過碳氮雙鍵插入鎂-氫共價鍵,硼氮偶聯(lián)成鍵,以及從硼到鎂的氫負離子轉(zhuǎn)移等步驟,從而再生鎂氫復(fù)合物并釋放產(chǎn)物.該反應(yīng)的決速步為負氫原子從硼到鎂的轉(zhuǎn)移過程.此外,通過理論計算拓展預(yù)測了鈣、鍶等其他堿土金屬復(fù)合物催化劑的反應(yīng)機理.研究結(jié)果表明,和鎂催化氫化反應(yīng)不同,鈣、鍶參與反應(yīng)的活性催化物種是碳二亞胺插入相應(yīng)氫化金屬復(fù)合物后所生成的對應(yīng)的氨基金屬絡(luò)合物.以此化合物作為催化循環(huán)的開始,反應(yīng)經(jīng)歷硼氮偶聯(lián)成鍵后,可直接與碳二亞胺發(fā)生硼碳之間的氫轉(zhuǎn)移,得到產(chǎn)物并再生活性催化物種.鈣、鍶復(fù)合物作為催化劑時經(jīng)歷不同反應(yīng)機理的原因是,它們的原子半徑遠遠大于鎂,因此可以與額外的碳二亞胺結(jié)合,并發(fā)生協(xié)同氫轉(zhuǎn)移反應(yīng).理論計算表明,當(dāng)使用鈣、鍶復(fù)合物作為催化劑時,反應(yīng)決速步活化能低于鎂催化的反應(yīng)途徑.因此,如果使用鈣、鍶復(fù)合物作為催化劑將會獲得更溫和的反應(yīng)條件.
[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.
【作者單位】： 重慶大學(xué)化學(xué)化工學(xué)院;
【基金】：國家自然科學(xué)基金(No.21372266)資助項目~~
【分類號】：O621.251

【相似文獻】

相關(guān)期刊論文 前10條

1 戴立信;，

本文編號：2291651