Abstract:

Divalent silicon species (silylenes) corresponding to carbenes in organic chemistry are key intermediates in numerous thermal and photochemical reactions of organosilicon compounds. Considering the electronic characteristics of this class of compounds, the higher homologues of the nitro-heterocyclic silylenes are also of interest and have been studied experimentally and theoretically. This prompted us to take a closer look at the chemical behavior of nitro-heterocyclic silylenes on a theoretical basis. The insertion reactions of nitro-heterocyclic unsaturated stable silylenes (1, 3, 4) and nitro-heterocyclic saturated silylenes (2, 5) into HF, H2O, and NH3molecules were performed using density functional theory (DFT) at the B3LYP/6-311++G(d,p) level. The insertion mechanisms were investigated and results from various reactions were compared. The results indicated that the insertion reaction mechanisms of heterocyclic silylenes and HX were similar to those of simple silylene. From the reaction energy barrier and the reaction enthalpy, the insertion reaction could occur easily according to the following order: HF>H2O>NH3. The reaction activities of saturated silylenes were stronger than those of unsaturated silylenes. Therefore, it is difficult to synthesize heterocyclic saturated silylenes.

Key words: Heterocyclic stable silylene, Insertion reaction, Transition state, Energy barrier