【作者】 闫盆吉；

【导师】 耿志远；

【作者基本信息】 西北师范大学 ， 无机化学， 2008， 硕士

【摘要】 过渡金属催化分解重氮化合物得到相应的有机金属体在有机合成中具有广泛的应用。比如在生成金属卡宾或者金属类卡宾后,可以与双键发生环丙烷化反应,也可以与X-H(X=O,N,S,Si, P,C)键发生插入反应,特别是将卡宾插入到O-H键中被认为是一种得到新C-O键而成相应醚类化合物的方法。与它们在实验方面的广泛研究相比,环丙烷化反应的理论研究报道很多,而插入反应的并不多见,特别是对O-H键插入反应尚没有报道。本文以量子化学中的分子轨道理论为基础,利用密度泛函理论(DFT),微扰理论(MPn)和极化连续介质(PCM)模型,对所研究的体系(铂类化合物催化)选择合适的基组,通过计算找出反应中各物种(包括过渡态)的优化构型,进而得到体系的势能面,动力学数据和热力学数据。我们用这些数据综合分析反应机理问题,为进一步的实验研究提供了理论依据。全文共分四章。第一章,综述了金属卡宾和金属类卡宾促进烯烃环丙烷化反应的研究进展及本文主要工作。第二章,概述了本文工作的理论背景和计算方法。前两章主要概括了本文工作的理论背景和理论依据,为我们的研究提供了可靠的量子化学方法。第三章,我们计算研究了铂化合物催化卡宾与乙烯的环丙烷化反应。研究的模型体系是乙烯和催化剂活性体,它是有CH2和催化剂Cl2Pt(PH3)2作用形成的。计算结果显示我们的催化剂活性体不是我们的金属卡宾(PH3)2Cl2Pt=CH2而是类卡宾,这个类卡宾存在(PH3)2Pt(CH2Cl)Cl(A)和(PH3)Pt(CH2PH3)Cl2 (B)两种结构形式。反应分为三个通道,亚甲基转移,类卡宾A的碳金属化和两个类卡宾的单磷形态的环丙烷化反应。最有利的反应通道是类卡宾B的亚甲基转移通道,它在气相中只需要克服31.32 kcal/mol的能垒。我们也用连续介质模型研究了在二氯甲烷,THF和苯溶剂中的溶剂化效应,结果显示,对类卡宾A,随着溶剂极性的增加亚甲基转移和碳金属化反应通道决速步骤的能垒有显著的降低,在二氯甲烷中能垒分别从43.25和52.50kcal/mol降低到25.36和38.53kcal/mol,而同样的过程对类卡宾B却在亚甲基转移通道中升高了6.30kcal/mol,但同时我们也发现溶剂化效应对单磷配体形态中的反应没有显著的影响。第四章,我们在密度泛函理论下对PtCl2催化分解重氮甲烷并与烯丙醇反应生成新的碳氧键的机理进行了研究。结果发现,与实验推理认识不同,我们的催化剂活性体不是金属卡宾也不是类卡宾,而是我们发现的多类卡宾形态,他们可能生成的顺序应该是F-类卡宾>T-类卡宾>D-类卡宾>类卡宾>铂卡宾,另外O-H键的插入反应也不是一步的插入反应机理,而是通过化合,氢转移和还原消除这样的步骤,其中将氢原子先转移到铂原子上也是以前没有发现的机理而且它是整个反应通道的决速步骤,而还原消除反应发生相对比较容易。更多还原

【Abstract】 The decomposition of diazo compounds in the presence of transition metal complexes as catalysts has allowed the controlled transfer of carbene units into organic substrates.Usually these reactions formally consist of (i) cyclopropanation or (ii) its insertion into an X-H bond(X = C, Si, N, P, O, S, Se, and halides).Particularly interesting is the case of the insertion into hydroxylic bonds,since it provides a new carbon-oxygen bond, and the subsequent conversion of the alcohol into an ether. However, compared with the comprehensive studies of experiment about cyclopropanation and oxygen–hydrogen insertion reaction, the cyclopropanation reaction which catalyzed by many transition metal complexes have been studied in theoretical investigation at the DFT level, but there is little theoretical report about the mechanism of O-H bond insertion reaction.In this paper, we chose several typical reactions that have been carefully studied using quantum methods, obtained some interesting results. On the basis of the molecular orbital theory, the tradition transition state theory as well as quantum chemistry theory, the systems (platinum complexes catalyzed) chose have been investigated using Density Functional Theory (DFT), the Moller-Plesset correlation energy correction MPn and the polarized continuum model (PCM). The structures of the reagents, the reaction products and transition states along the reaction paths have been obtained, then obtained the reaction surfaces, the spectrum datum, thermodynamic datum as well as the information of orbitals. The reaction mechanism has been argued deeply using these data.The whole paper consists of four chapters. Chapter 1 mainly reviews the evolution of cyclopropanation reaction of ethylene with metal carbenoid. The second chapter summarizes the theory of quantum chemistry and calculation methods of this paper. The contents of two chapters were the basis and background of our studies and offer us with userful and reliable quantum methods.In chapter 3, a computational study of the platinum-catalyzed cyclopropanation reaction with olefin is presented. The model system is formed by an ethylene molecule and the active catalytic species, which forms from a CH2 fragment and the Cl2Pt(PH3)2 complex. The results shows the active catalytic species is not a metal-carbene of the type (PH3)2Cl2Pt=CH2 but two carbenoid complexes which can exist in almost two degenerate forms, namely (PH3)2Pt(CH2Cl)Cl (carbenoid A) and (PH3)Pt(CH2PH3)Cl2 (carbenoid B). The reaction proceeds through three pathways: methylene transfer, carbometalation for carbenoid A and the reaction of a monophosphinic species for carbenoid (A and B). The most favored reaction channel is methylene transfer pathway for (PH3)Pt(CH2PH3)Cl2 (carbenoid B) species with a barrier of 31.32kcal/mol in gas phase. The effect of dichloromethane,THF and benzene solvent are investigated by PCM method. For carbenoid A, both methylene transfer and carbometalation pathway barriers to reaction become remarkable lower with the increasing polarity of solvent (from 43.25 and 52.50kcal/mol for no solvent to 25.36 and 38.53kcal/mol in the presence of the dichloromethane). In contrast, the reaction barriers for carbenoid B via the methylene transfer path hoist 6.30kcal/mol while the barriers do not change significantly for the reaction path of a monophosphinic species for carbenoid (A and B).Chapter 4, In this paper we have carried out a theoretical investigation at the DFT (B3LYP) level of the mechanism of the O-H insertion reaction catalyzed by PtCl2 complex. The model system is formed be one allyl alcohol molecule and several diazomethane molecules and the catalyst PtCl2 complex. The resultes indicate that , in breach of traditional view, the starting active catalytic species is not the platinum-carbene Cl2Pt=CH2 or carbenoid ClPtCH2Cl, they should be determined according to the following orders: F-carbenoid > T-carbenoid > D-carbenoid > carbenoid > platinum-carbene. On the other hand, the one-step O-H bond insertion reaction has been broved to be a unlikely process, which should consists of three steps: coordination, hydrogen shift, reductive elimination, and the results indicate that the hydrogen shift process is rate-determining step for every paths, the reduction elimination is very easy to occur.更多还原