本文選題：鍵解離焓　切入點：銥氫鍵　出處：《中國科學技術大學》2017年碩士論文　論文類型：學位論文

【摘要】：第一章簡述了半三明治型的過渡金屬絡合物的應用,其中重點詳述了茂基配位的銥絡合物在其中C-H鍵活化、Diels-Alder反應、(不對稱)氫轉移以及還原二氧化碳等方面的應用。同時簡述了論文內容。第二章簡述了計算化學相關的一些基礎知識,從第一性原理出發(fā)的從頭算方法,到密度泛函理論,再到溶劑化效應和計算模型以及計算的基組。而后又介紹了兩種分析方法:NBO電荷布居分析和形變-結合能分析。第三章簡述了研究生階段的主要工作內容。銥氫絡合物是諸多銥催化反應中的催化劑和關鍵中間體,Ir-H鍵的斷裂與生成在這些反應中往往起到至關重要的作用。本文利用密度泛函方法(TPSS)對多種茂基配位的銥氫絡合物的銥氫鍵均裂能(解離氫原子)和異裂能(解離負氫離子)進行了系統(tǒng)研究。計算發(fā)現,銥中心貧電子有利于Ir-H鍵的均裂,同時吸電子基以及強π電子受體有利于減弱Ir中心電子密度。剛性螯環(huán)以及大位阻取代基可以通過Ir-H鍵斷裂后釋放空間位阻進一步減小其鍵能。而如2-苯基吡啶、聯(lián)吡啶配體等配位的銥氫化合物,由于Ir中心d軌道可以和這些配體的芳香體系形成大π鍵,從而降低了這些物種的H-解離焓。烯烴配體有利于均裂過程,卻不利于異裂的氫負離子解離。膦配體對均裂過程影響不大,但是可以大大減小異裂的解離焓。貧電子的B原子配位時,雖然有利于均裂,但因會形成Ir-H-B的氫橋鍵,不利于解離氫負離子。Si原子相對富電子,則對這兩個過程均不利。
[Abstract]:In the first chapter, the application of semi-sandwich transition metal complexes is briefly described. The applications of the iridium complexes with metallocene in the C-H bond activation of Diels-Alder reaction and the reduction of carbon dioxide are described in detail. In the second chapter, the computational chemical phase is briefly described. Some basic knowledge, AB initio method from first principles to density functional theory, Then, the solvation effect, the computational model and the basis set of calculation are introduced. Then, two analytical methods are introduced: the charge population analysis and the deformation-binding energy analysis. In Chapter 3, the main work of the graduate stage is briefly described. The complex is the catalyst and the key intermediate of iridium catalytic reactions. The breakage and formation of the Ir-H bond often play an important role in these reactions. In this paper, the density functional method (DFT) is used to study the iridium complexes of various metallocene coordination sites. The iridium hydrogen bond splitting energies (dissociating hydrogen atoms) and heterolysis energies (dissociating negative hydrogen ions) of the complexes have been systematically studied. Iridium center poor electron is favorable to the homolysis of Ir-H bond. At the same time, the absorption of electron group and the strong 蟺 electron receptor can reduce the electron density of ir center. The rigid chelating ring and the large steric resistance substituent can further reduce the bond energy by releasing the steric hindrance after the Ir-H bond breaks, such as 2-phenylpyridine. For iridium compounds coordinated with bipyridine ligands, the d orbitals of ir center can form a large 蟺 bond with the aromatic system of these ligands, which reduces the H dissociation enthalpy of these species, and the olefin ligands are favorable for the homolysis process. Phosphine ligands have little effect on the homolysis process, but can greatly reduce the dissociation enthalpy of heterolysis. The B atom coordination of the poor electrons is favorable to homolysis, but the hydrogen bridge bond of Ir-H-B can be formed. It is unfavorable to dissociate hydrogen anion. Si atom is relatively rich in electrons, then it is unfavorable to both processes.
【學位授予單位】：中國科學技術大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O641.4

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本文編號：1636096