茂基铱络合物中Ir-H键解离能的理论预测

发布时间：2018-03-19 21:34

本文选题：键解离焓　切入点：铱氢键　出处：《中国科学技术大学》2017年硕士论文　论文类型：学位论文

【摘要】：第一章简述了半三明治型的过渡金属络合物的应用,其中重点详述了茂基配位的铱络合物在其中C-H键活化、Diels-Alder反应、(不对称)氢转移以及还原二氧化碳等方面的应用。同时简述了论文内容。第二章简述了计算化学相关的一些基础知识,从第一性原理出发的从头算方法,到密度泛函理论,再到溶剂化效应和计算模型以及计算的基组。而后又介绍了两种分析方法:NBO电荷布居分析和形变-结合能分析。第三章简述了研究生阶段的主要工作内容。铱氢络合物是诸多铱催化反应中的催化剂和关键中间体,Ir-H键的断裂与生成在这些反应中往往起到至关重要的作用。本文利用密度泛函方法(TPSS)对多种茂基配位的铱氢络合物的铱氢键均裂能(解离氢原子)和异裂能(解离负氢离子)进行了系统研究。计算发现,铱中心贫电子有利于Ir-H键的均裂,同时吸电子基以及强π电子受体有利于减弱Ir中心电子密度。刚性螯环以及大位阻取代基可以通过Ir-H键断裂后释放空间位阻进一步减小其键能。而如2-苯基吡啶、联吡啶配体等配位的铱氢化合物,由于Ir中心d轨道可以和这些配体的芳香体系形成大π键,从而降低了这些物种的H-解离焓。烯烃配体有利于均裂过程,却不利于异裂的氢负离子解离。膦配体对均裂过程影响不大,但是可以大大减小异裂的解离焓。贫电子的B原子配位时,虽然有利于均裂,但因会形成Ir-H-B的氢桥键,不利于解离氢负离子。Si原子相对富电子,则对这两个过程均不利。
[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.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O641.4

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