The molecular and electronic structure features of silatranes, germatranes, and their carbon analogs

Molecular geometries of fifty-six metallatranes N(CH2CH2Y)3M-X and fifty-six carbon analogs HC(CH2CH2Y)3M-X (M = Si, Ge; X = H, Me, OH, F; Y = CH2, O, NH, NMe, NSiMe3, PH, S) were optimized by the DFT method. Correlations between changes in the bond orbital populations, electron density ρ(r), electron density laplacian ∇2ρ(r), ¦λ1¦/λ3 ratio, electronic energy density E(r), bond lengths, and displacement of the central atom from the plane of three equatorial substituents and the nature of substituents X and Y were studied. As the number of electronegative substituents at the central atom increases, the M←N, M-X, and M-Y bond lengths decrease, while the M←N bond strength and the electron density at critical points of the M←N, M-X, and M-Y bonds increase. An increase in electronegativity of a substituent (X or Y) is accompanied by a decrease in the ionicities of the other bonds (M-X, M-Y, and M←N) formed by the central atom (Si, Ge). A new molecular orbital diagram for bond formation is proposed, which takes into account the interaction of all five substituents at the central atom (M = Si, Ge) in atrane molecules.