Reactivity of silagermenylidene toward nitrous oxide: a preliminary DFT study.

The possible reaction mechanism of silagermenylidene and its NHC (N-heterocyclic carbene) coordinated form with N2O were investigated by DFT methods. Mainly, the potential energy surfaces of the five pathways I-IV were explored. Pathways I, II, III, and III' deal with the oxidation of silagermenylidene, whereas that of NHC coordinated form is associated with pathways I, III, III', and IV. Pathway I is initiated by the interaction between terminal N atom of N2O and Si atom of silagermenylidene in a stepwise manner. Pathway II details concerted direct oxidation of silagermenylidene. Pathways III and III' are related to the concerted 1,3-dipolar cycloaddition steps. Pathway IV is about the interaction of terminal atoms of N2O with carbenic Ge atom of silagermenylidene. All the proposed pathways I-IV portray the isomerization of silagermenylidenes to silagermoxiranylidenes. The subsequent N2O addition to the silagermoxiranylidenes was also investigated in the present study. Somehow with a trend similar to silagermenylidenes, the proposed pathways I-IV exist for the second molecule N2O activation by silagermoxiranylidenes. A comparison of the free energy profiles of the proposed pathways gave the important result that pathways III and III' remain the most facile mechanisms to activate N2O in all cases. We strongly believe that the proposed mechanisms will be effective to better understand the chemistry of heavier vinylidenes and provide further impetus to this field. Graphical Abstract The possible oxidation reaction mechanism of silagermenylidene with nitrous oxide was investigatedthrough density functional calculations. The concerted 1,3-dipolar cycloadditions are determined to beenergetically most facile pathways.