Mechanistic Insights Into the [3+1] Cycloadditions of Me₃SiN₃ on Bis‐Silylene and the Formation of Pseudo‐Silaazatriene

Abstract

The reaction mechanism for the formation of the pseudo‐silaazatriene 1 by the reaction of 1 equivalent of bis‐silylene with 3 equivalents of azide Me3SiN3 has been explored at M06/def2‐TZVPP//BP86‐D3(BJ)/def2‐TZVPP level of theory. The reaction mechanism is guided by the high Lewis basicity of the silicon lone pair and the high Lewis acidic character of Si‐N bonds, as well as by the high tendency to eliminate N2 from Me3SiN3. The first step of the reaction is the formation of [3+1] cycloaddition product (I1) by the synergetic interactions of the lone pair on the silylene silicon with the π* molecular orbital of Me3SiN3 which is majorly localized on the terminal nitrogen atom, and the donation of the σ‐type lone pair on the nitrogen atom connected to the SiMe3 group with the Si‐N σ* orbital on silylene. The elimination of N2 from I1 results in the formation of pseudo‐silaimine intermediate I2 having a dicoordinated, monovalent nitrogen atom. The Si‐Si bond cleavage of I2 results in intermediate I3, which is susceptible to [3+1] cycloaddition reaction with two molecules of Me3SiN3 in a stepwise manner results in I7 having two silaimine and one silaamine moieties. Further 1,3‐silyl migration results in pseudo‐silaazatriene 1.