类硅烯[CH(R)N]_2SiLiF(R=H和t-Bu)的构型及异构化反应

Theoretical study on the structures and isomerization of Silylenoid (RNCH=CHNR) SiLiF (R=H and t-Bu)

用密度泛函理论(DFT)在B3LYP/6-31G(d)计算水平上首次研究了N-杂环类硅烯[CH(R)N]_2SiLiF(R=H和t-Bu)的构型及异构化反应。计算得到了[CH(H)N]_2SiLiF的五个平衡构型和[CH(t-Bu)N]_2SiLiF的四个平衡构型。两种类硅烯的各构型中,包含四元环结构的p-络合物构型都是最稳定的,是实验上可能存在的构型。三元环构型、σ-络合物构型和"经典"四面体构型都是不稳定的。t-Bu基团增强了σ-络合物构型的稳定性,但减小了类硅烯的复合能,从而进一步证明了t-Bu取代的硅烯的稳定性。

The structures and isomerization of N-heterocyclic silylenoid （R=H and t-Bu） were studied by density functional theory （DFT） at B3LYP/6-31G（d） level for the first time. For both two silylenoids, the p-complex structure with a four-membered ring is the most stable form and would be the experimentally detectable one. The three-membered ring structure, σ-complex, and the＂classical＂tetrahedron structures are active intermediates when silylene （RNCH=CHNR）Si approach to LiF molecule. The stability, reactivity, existence and tert-butyl substituent effects of various equilibrium structures were discussed.