Theoretical Study On The Reactivity Of Germylene Compounds

According to the principle of generalized isoelectronic species, germylene, carbene and silene are isoelectronic species, are important active intermediate. Intuitively, germylene chemical properties are similar to those of carbene and silene. Germylene reactions (involving insertion reaction, additive reaction and polymerization reaction) have been reported as effective methods to synthesize relevant germanium compounds containing new bonds and heterocycles. So the research of germylene reactions is a interested topic, in particular, when we have found that, some organicgermanium compound have biologic activity, many people go in for researching the synthetic mechanism of organicgermanium compound. So, theoretically systematic researches on germylene and substituted germylenes insertions reaction have important significance both in theory and practice.In this thesis, many important reactions involved in the synthesis processes of germylene and substituted germylenes insertions with benzyl chloride, vinyl chloride and dimethyl disulfide have been studied using density function theory. The main contents of this paper are as follows:Chapter 1 is the introduction. In the introduction, the research history on germylene insertion reaction in the research background and the innovation are briefly introduced.In chapter 2, the theoretical investigation on the structure and the reactions is performed. All basic theories we used are transition state theory and density functional theory.In chapter 3, we have researched the synthesis processes of germylene and substituted germylenes insertions with benzyl chloride. The reactants, precursor complexes,products and transition states of the reactions have been optimized using Density Function Theory, and all of the transition states have been verified to connect with the designated reactants and products by performing intrinsic reaction coordinate (IRC) analysis at the B3LYP/6-311+G(d, p) level. All our computational results show that, germylene insertion reaction is a concerted synchronous reaction, has two reaction pathways, and forms transition states involving three-member ring. On the basis of the results of the present study, we draw an intriguing conclusion that for the substituted germylenes, the more electronegative the substituents, the larger theâ–³E_st of GeX₂, and the higher the activation barrier. All our computational results also can be rationalized on the basis of a configuration mixing (CM) model.In chapter 4, we have researched the synthesis processes of germylene and substituted germylenes insertions with vinyl chloride. The reactants, precursor complexes, products and transition states of the reactions have been optimized using Density Function Theory, and all of the transition states have been verified to connect with the designated reactants and products by performing intrinsic reaction coordinate (IRC) analysis at the B3LYP/6-311+G(d, p) level. All our computational results show that, germylene and halogen-substituted germylenes reactions are similar to insertions reactions between germylenes and benzyl chloride, all have two reaction pathways. However, for the reaction pathway II, the first step in the reaction of methyl-substituted germylene or silicomethyl-substituted germylene with vinyl chloride is the formation of germacyclopropane by cycloaddition reaction, which then chloride migrates through a three-center transition structure to yield the eventual insertion product. Alkyl-substituted and silicon alkyl-substituted germylene insertions are much more favorable than those ofÏ€-donor substituted germylenes, furthermore, the more electropositive the substituents, the lower theâ–³E_st of GeX₂, the smaller the activation barrier, and the larger the exothermicity.In chapter 5, we have researched the synthesis processes of germylene and substituted germylenes insertions with vinyl chloride. The reactants, precursor complexes,products and transition states of the reactions have been optimized using Density Function Theory at the B3LYP/6-311+G(3df, 2p) level. All our computational results show that, that reaction has six reaction pathways. The optimized geometries of the transition states are close to the geometries of products, so the six reaction pathways process later potential barrier. We also have found the optimal reaction pathway and the optimal geometries of product.We make great efforts to get the systemic and accurate results during the study. Actuall, many valuable results are obtained. This will guide and promote the development of theoretical and practical study on the germylene insertion reaction.