二氟硅烯与甲醛环加成反应机理的理论研究

硅烯（R2Si：）是某些有机硅反应的重要活性中间体[1],硅烯反应（如插入反应,加成反应,聚合反应等）被认为是合成含硅新键和含硅杂环的有效方法,因而硅烯反应的研究一直是有机硅化学家十分感兴趣的一个前沿研究领域[2]．对于硅烯的环加成反应而言,由于它具有合成含硅张力小环的重要价值,因此受到了许多化学家的高度重视,并对此做了若干的研究工作[3-7]。然而到目前为止,关于硅烯环加成反应的机理还处于一种推测水平,尤其是对卤代硅烯环加成反应机理的研究,至今尚未见文献报导,考虑到卤代卡宾在合成张力小环方面的重要作用[8,9]…     

二氟硅烯与甲醛环加成反应机理的理论研究

The mechanism of the cycloadditohn reaction of singlet difluorosilylene with formaldehyde have been studied by RHF/6-311G* gradient method. The electron correlation energy corrections of energies for all the structures were computed using second-order Moller-Plesset perturbation theory(MP2). The results show that this reaction proceeds via two steps:1)Difluorosilylene and formaldehyde form an intermediate complex, it is an exothermal reaction with no barrier.2) The intermediate complex isomerizes to form the product, after being corrected by zero-point energies, the barrier is 127.28 kJ•mol-1 (MP2/6-311G* 6-311G*).     

Reactions of Difluorosilylene with Amines,Phosphines and Halomethanes The First Evidence of the Insertion of Difluorosilylene into Tetrafluorosilane

The reactions of SiF₂/SiF₄ with amines, phosphines and various halomethanes were studied. The results show that in the presence of strong Lewis base (Et₃N, HNEt₂, PR₃, PR₂Cl), SiF₂ inserts initially into SiF₄ to form Si₂F₆, which was followed by subsequent reactions leading to products containing SiF₃ groups. This is the first report of the insertion of SiF₂ into SiF₄. When the reactants were a weaker base (such as RPCl₂, CX₃Br, X=F, Cl), insertion of SiF₂ into P-Cl and C-Br bonds became predominant.