来源：类硅烯结构及反应的理论研究 发布时间：2010年7月19日
类硅烯(R1R2SiMX)是类卡宾的硅类似物，其性质与硅烯相似。在R1R2SiMX中，离去基团X(通常是卤素)与金属M(通常是碱金属)同时与Si原子发生作用。类硅烯是有机硅反应的一类重要的活性中间体，它的存在已被近年来最新的实验所证实。理论和实验研究都表明：类硅烯具有亲电和亲核的双重反应性，能进行许多化学反应，如插入反应、加成反应、重排反应、聚合反应等等。类硅烯的反应是合成含硅新键和含硅杂环的有效方法。因此，研究类硅烯具有重要的理论和实践意义。 与已在理论和实验上研究的很充分的类卡宾相比，类硅烯的研究还是很有限的。人们对类硅烯的结构和反应性的认识还很不够。基于类硅烯的研究现状，本论文的内容主要包括以下几个方面： 第一章绪论对类硅烯化学的发展史和研究现状进行了概括，同时介绍了本论文工作用的主要研究方法(从头算法和密度泛函理论方法)。 第二章研究了类硅烯H2SiLiF的结构及反应。类硅烯H2SiLiF有四种平衡构型，三元环构型1、p-络合物构型2、σ-络合物构型3、“经典”四面体构型4。它们的热稳定性顺序为：2＞1＞4＞＞3。本章研究了类硅烯H2SiLiF的以下反应： 1) 构型1和2都能与XHn(X=C，Si，N，P，O，S，F，Cl；n=4，4，3，3，2，2，1，1)发生插入反应。在G3MP2水平上，1有两种反应路径，2有三种反应路径。所有反应均是协同机理，经过一个三元环型过渡态，生成取代硅烷H3SiXHn-1和LiF。构型1的插入反应性要高于2。 2) 首次在MP2(full)／6-31G(d，p)水平上研究了构型1与XHn的H2消除反应：H2SiLiF+XHn→HnXSiLiF+H2。先形成一个前期复合物，经过四元环型过渡态，生成取代的三元环类硅烯HnXSiLiF，同时消除H2分子。与构型1的插入反应相比，H2消除反应不占优势。 3) 首次在B3LYP／6-31G(d，p)水平上研究了构型1与XHn的取代反应：H2SiLiF+XHn→H3SiF+LiXHn-1。先形成一个前期复合物，经过一个五元环型过渡态，形成反应中间体，最后中间体解离为氟代硅烷H3SiF和化合物LiXHn-1。 4) 在B3LYP／6-311+G(d，p)水平上研究了类硅烯H2SiLiF的构型及异构化反应的溶剂效应。溶剂效应用自恰反应场(SCRF)理论的Tomasi的极化连续介质【Abstract】 Silylenoid (R1R2SiMX), silicon analogues of carbenoids, can be species with some silylene-like character. A leaving group X (usually halogens) and a metal atom M (usually alkali metals) are bound to the same silicon atom in a silylenoid. Silylenoids have been confirmed to be existent and to be active intermediates in some organosilicon reactions. Both experimental and theoretical results show that silylenoids have ambiphilic character, nucleophilicity and electrophilicity, and can take part in many reactions. Such reactions as insertion, addition, rearrangement, and polymerization were recognized as important and effective methods for preparation of the new silicon-bonded and heterocyclic silicon compounds. Therefore, further thorough investigations on silylenoids will be of important theoretical and practical values.In contrast to extensive experimental and theoretical studies on carbenoids, there are only a few reports on silylenoids, and knowledge of the structures and reactions of silylenoids is still quite limited. This dissertation is mainly composed of the following parts based on the above research background.In introduction (chapter 1), the research history and current state on silylenoid chemistry have been briefly illustrated. The research methods about ab initio and density functional theory have been introduced.In chapter 2, the theoretical investigation on the structures and reactions of silylenoid H2SiLiF is performed. Silylenoid H2SiLiF has four isomers, three-membered ring structure (1), p-complex (2), σ-complex (3), and "classical" tetrahedral structure (4). The thermal stability of these isomers is in order of 2 > 1 > 4 >> 3.1) The insertion reactions of 1 and 2 into XHn (X = C, Si, N, P, O, S, F, Cl; n = 4, 4, 3, 3, 2, 2, 1, 1) molecules have been studied at G3MP2 level. Two reaction paths for 1 and three paths for 2 are obtained. The reaction mechanism is a concerted manner via a three-center type transition state to obtain the substituted silane H3SiXHn-1 and LiF. The insertion reactivity of structure 1 is higher than that of 2.2) The H2 elimination reactions of 1 with XHn, H2SiLiF + XHn → HnXSiLiF