【作者】 戚玉华；

【导师】 冯大诚；

【作者基本信息】 山东大学 ， 物理化学， 2009， 博士

【摘要】 类硅烯和硅烯是有机硅反应的一类重要的活性中间体,其反应是合成含硅新键和含硅杂环的有效方法。理论和实验研究表明:类硅烯具有亲电和亲核的双重反应性,能进行多种化学反应,如插入反应、取代反应、加成反应等。基于类硅烯和硅烯的研究现状,本论文主要进行了以下几个方面的工作:第一章绪论对类硅烯和硅烯性质和研究现状进行了概括。第二章研究方法简介对本论文用的主要研究方法（从头算法和密度泛函理论方法）进行了简单的介绍。第三章用密度泛函的方法研究了类硅烯H₂SiLiF和CH₃XH_n-1（X=F,Cl,Br,O,N;n=1,1,1,2,3）取代和插入反应。1) H₂SiLiF和CH₃XH_n-1取代反应是亲核取代的放热反应。反应有背面进攻和正面进攻两条反应路径,两条路径得到相同的最终产物H₂SiFCH₃和LiX。两条路径的反应势垒对于同一族和同一周期的X的体系,随着X原子序数的增加而降低,背面进攻的路径的势垒较低,在反应中占优势。2)类硅烯H₂SiLiF插入CH₃XH_n-1中C-X的反应是协同反应,反应最终可得到H₂SiCH₃X和LiF。反应的势垒,对于同一族X的体系,插入反应的势垒变化不大,对于同一周期X的体系,随着原子序数X的增加,插入反应的势垒逐渐增大。3)插入反应过渡态的总能量比相应的取代反应过渡态的能量高。因此对于H₂SiLiF和CH₃XH_n-1反应体系来说,取代反应比插入反应容易进行。所以在该反应体系的产物中,取代产物量会大于插入产物的量。第四章研究了类硅烯（TSi）BrSiLi₂与Me₃SiCl的反应。1) CH₃BrSiLi₂、C（SiH₃）₃BrSiLi₂以及（TSi）BrSiLi₂的构型计算表明,这一类型的类硅烯主要有p络合物、平面和折状三种构型。一般情况下,p络合物构型的能量最高,平面构型和折状构型的能量相近。平面构型和折状构型是这类类硅烯存在的可能构型。2) H₂SiLiBr、CH₃BrSiLi₂、C（SiH₃）₃BrSiLi₂与Me₃SiCl的插入反应是一协同的反应过程,反应的实质是类硅烯硅原子的空P轨道和3S电子分别与Me₃SiCl中的正电部分Me₃Si和负电部分Cl发生作用。插入反应的势垒以H₂SiLiBr＞C（SiH₃）₃BrSiLi₂＞CH₃BrSiLi₂的顺序逐渐降低。对于CH₃BrSiLi₂类型类硅烯的插入反应,大的推电子取代基团C（SiH₃）₃使插入反应的势垒升高。3) H₂SiLiBr、CH₃BrSiLi₂、C（SiH₃）₃BrSiLi₂中的带负电的硅原子可以与Me₃SiCl发生亲核取代反应。反应的势垒以C（SiH₃）₃BrSiLi₂＞H₂SiLiBr＞CH₃BrSiLi₂的顺序变化。4)从反应过程的能量变化来看,插入反应的势垒均高于取代反应的势垒。对于CH₃BrSiLi₂、C（SiH₃）₃BrSiLi₂类型的类硅烯与Me₃SiCl的反应,推电子基团C（SiH₃）₃使取代反应相对于插入反应的优势更大。5)类硅烯与Me₃SiCl插入和取代反应生成不同的产物。由于取代反应比插入反应有优势,所以在反应所生成的产物混合物中,取代产物的量大于插入产物。第五章用从头算分子轨道和密度泛函的方法研究了类硅烯H₂SiLiX（X=F,Cl）对甲醛的加成反应。1)类硅烯H₂SiLiX采用三元环和p络合物两种构型,从加成过程的势垒上看,三元环构型的类硅烯H₂SiLiX更容易进行与甲醛加成反应,并且卤素元素为氟的类硅烯比氯的类硅烯易与H₂CO加成。2)H₂SiLiX（X=F,Cl）和H₂CO的不对称加成反应与H₂SiLiX（X=F,Cl）与乙烯、乙炔的对称性的加成反应相比,形成的前期复合物的结构不同。3)在THF和在乙醚中,在B3LYP/6-31G（D）水平下的计算表明,在极性溶剂中更易发生H₂SiLiX（X=F,Cl）和甲醛的加成反应,溶液的极性越大反应越易进行;并且在极性较大的溶剂中,产物复合物更易分解而得到硅杂环氧甲烷。第六章研究了五配位类硅烯PhCH₂（NH₂）CH₃SiLiF的结构和反应。1)类硅烯PhCH₂（NH₂）CH₃SiLiF有三种平衡构型,三元环构型1、p-络合物构型2和σ-络合物构型3。在溶剂THF中,类硅烯的三种构型的结构和在真空条件下类似。它们的能量顺序在THF溶剂和真空条件下相同,均为2＞1＞3。2) PhCH₂（NH₂）CH₃SiLiF插入C-F的反应机理与PhCH₂（NH₂）CH₃Si相似。前者的势垒比后者高62.9kJ/mol。类硅烯PhCH₂（NH₂）CH₃SiLiF比相应硅烯PhCH₂（NH₂）CH₃Si稳定。3) PhCH₂（NH₂）CH₃SiLiF插入C-F的反应势垒比PhCH₃CH₃SiLiF的要高。表明N原子对类硅烯PhCH₂（NH₂）CH₃SiLiF的稳定性起了很重要的作用。第七章研究了硅烯与H₂B-X（X=F,Cl,Br）化合物的插入反应。硅烯插入B-X键的反应是一个协同反应过程,反应势垒分从F到Br逐渐增大。本论文的创新性成果主要表现在如下几个方面:1)类硅烯和硅烯可发生类似的化学反应。在第三章和第四章中,本文系统地研究了类硅烯和CH₃XH_n-1（X=F,Cl,Br,O,N;n=1,1,1,2,3）与Me₃SiCl取代和插入反应。发现类硅烯和CH₃XH_n-1与Me₃SiCl的取代反应比插入反应容易进行,反应以取代反应为主。而硅烯和CH₃XH_n-1与Me₃SiCl易发生插入反应,在这一点上,硅烯和类硅烯不同。本章的研究不仅和实验结果相吻合,并可为这一类型的实验反应设计提供理论指导。2)相对于四配位的类硅烯来说,对五配位的类硅烯的研究较少。本文首次在理论上对五配位类硅烯的结构进行了研究,并讨论了配位原子N对类硅烯性质的影响。这一研究结果对于进一步开展五配位的类硅烯的实验研究有重要的理论指导意义。3)类硅烯的加成反应是类硅烯的一种重要的反应,文献中对类硅烯加成反应的理论研究均是对称性加成反应。在第四章中,本文首次在理论上研究了类硅烯的不对称加成反应,并与对称性的加成反应进行了比较。4)硅硼类化合物是一类非常重要的化合物,但合成方法有限。本文研究了硅烯插入硼卤键的插入反应本质和规律,为实验上利用这一方法进行硅硼类化合物的合成提供理论支持。更多还原

【Abstract】 Silylenoids and silylenes are important intermediates in some organosilicon reactions and their reactions were recognized as important and effective methods for the preparation of new silicon-bonded and heterocyclic silicon compounds.Both experimental and theoretical results show that silylenoids and silylenes have ambiphilic character,nucleophilicity and electrophilicity,and can take part in many reactions,such as insertion,addition,rearrangement,and polymerization.Based on the present research, this dissertation is mainly composed of the:following parts.Chapter 1 introduces the characters and the previous researches of silylenoids and silylenes.Chapter 2 mainly illustrates the ab initio and density functional theory.In chapter 3,the DFT investigation on the insertion and substitution reactions of H₂SiLiF and CH₃XH_n-1（X=F,Cl,Br,O,N;n=1,1,1,2,3） is performed.1) The theoretical results indicate that the substitution reactions of H₂SiLiF with CH₃XH_n-1 occur in a concerted manner via two reaction paths,ⅠandⅡ,forming same products,H₂SiFCH₃ and LiXH_n-1.For both pathways,the substitution barriers decrease with the increase of the atomic number of the element X for the same family systems or for the same row systems.PathⅠis more favorable than pathⅡ.2) H₂SiLiF inserts into a C-X bond via a concerted manner,forming H₂SiXH_n-1CH₃ and LiF.For C-X bonds,the order of reactivity by A insertion indicates the reaction barriers increase for the same-row element X from right to left in the periodic table,whereas change very little for the insertion into X-C bonds of the same-family element X.3) The total energies of the insertion transition states are higher than those of the corresponding substitution states.Thus,the substitution reactions are more favorable than the insertion reactions for the H₂SiLiF and CH₃XH_n-1 systems.It is reasonable to expect that the amount of substitute product H₂SiFCH₃ is more than that of insertion product H₂SiXH_n-1CH₃ among the final products.The research in chapter 3 is about the reaction of（TSi）BrSiLi₂ and Me₃SiCl. 1) The calculations indicate that CH₃BrSiLi₂,C（SiH₃）₃BrSiLi₂ and（TSi）BrSiLi₂ have three probably structures,p complex structure,the plain structures and the folded structures.The energy of the p complex is highest and the energy of the plain structure nearly equals to that of the folded structure.2) The insertion of CH₃BrSiLi₂,C（SiH₃）₃BrSiLi₂ and（TSi）BrSiLi₂ into Si-Cl bond is a concerted reaction.The insertion barriers is in the order of H₂SiLiBr＞C（SiH₃）₃BrSiLi₂＞CH₃BrSiLi₂.The big group C（SiH₃）₃ make the insertion more difficult.3) The negative silicon in silylenoids can nucleophilicly substitute with Me3SiCl. The energy barriers are in the order C（SiH₃）₃BrSiLi₂＞H₂SiLiBr＞CH₃BrSiLi₂.4) On the view of energy,substitution barriers are lower that those of insertion. The electron-donating group,C（SiH₃）₃,makes the barrier difference（between the substitution and the insertion） for the case of C（SiH₃）₃BrSiLi₂ relative to the case CH₃BrSiLi₂.5) Due to the lower barriers of the substitutions,the substitution products are dominant in the reaction system.In chapter 5,the addition reactions of H₂SiLiX（X=F,Cl） and H₂CO are discussed.1) The three-member ring and the p complex structures of H₂SiLiX（X=F,Cl） are adopted in this study.The addition of the three member ring structure to H₂CO is easy to occur,and the barrier of H₂SiLiF is lower that of H₂SiLiCl.2) The structures of the precursor complexes in the asymmetric additions of H₂SiLiX（X=F,Cl） to H₂CO are different from those in the symmetric additions of H₂SiLiX（X=F,Cl） to C₂H₄ and C₂H₂.3) The calculations at the B3LYP/6-31G（d） level indicate that the addition reactions of H₂SiLiX（X=F,Cl） to H₂CO easily occur in the polar solvent.The higher the solvent polarity is,the lower the barriers of the addition reactions are.The final complexes also easily dissociate into oxasilacyclopropane and LiX in the polar solvent.In chapter 6,the theoretical investigation on the structures and reactions of silylenoid PhCH₂（NH₂）CH₃SiLiF is performed. 1) Silylenoid PhCH₂（NH₂）CH₃SiLiF has three isomers,1（three member ring structure）,2（p complex structure） and 3（σcomplex structure）.The structures of silylenoid PhCH₂（NH₂）CH₃SiLiF in THF are similar to those in vacuum.Their energies are in the order of 2 > 1 > 3 both in vacuum and in THF.2) The insertion of Silylenoid PhCH₂（NH₂）CH₃SiLiF into the C-F bond is similar to that of silylene into the C-F bond.The activation barrier for the former is 62.9 kJ/mol higher than that for the latter.Silylenoid PhCH2（NH2）CH3SiLiF is more stable than silylene PhCH₂（NH₂）CH₃Si.3)The energy barrier of PhCH₂（NH₂）CH₃SiLiF insertion into C-F is higher than that of PhCH₃CH₃SiLiF,showing that the N atom plays an important role on the stability of silylenoid PhCH₂（NH₂）CH₃SiLiF.In chapter 7,the insertion reaction of silylene into H₂B-X（X=F,Cl,Br） is considered.The reaction is in a concert manner and barriers increase from F to Br.The valuable results in this dissertation can be summarized as follows:1)Silylenes and silylenoids have similar characters in reactions.In chapter 3 and chapter,this dissertation investigates the reactions of silylenoids with CH₃XH_n-1（X=F, Cl,Br,O,N;n=1,1,1,2,3） and Me₃SiCl.It is found that the barriers of substitutions are lower than those of corresponding insertions,and that the substitutions are dominant. But insertions usually occur in the silylene with CH₃XH_n-1（X=F,Cl,Br,O,N;n=1,1,1, 2,3） and Me₃SiCl systems.So silylenes and silylenoids are different in this point.This calculated results are in agreement with experiments and can provide theoretical guide for the design of silylenoid experiments.2) Relative to the tetracoordinate silylenoids,the researches on the pentcoordinate silylenoids are rare.The chapter 5 theoretically studies the structures for the first time, and the effect of the coordinate atom,N,on the character of silylenoid are also discussed.This may support guides for the further study of pentcoordinate silylenoids.3)The addition reactions are very.important ones for silylenoids.Previous researches are all concerned about the symmetric additions.This paper investigate the asymmetric additions of silylenoids and a contrast is made between the asymmetric and symmetric additions.4) Borosilicate compounds are important in chemical reactions,but syntheses are rather difficult.The chapter 7 discusses the character and laws for the insertion of silylene into C-X（X=F,Cl and Br）.This will be useful to the syntheses of borosilicate compounds.更多还原