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The energy and electronic parameters of the nitrogen atom inversion in isoelectronic N-alkylimines and N-sulfenylimines (H2C=NR, where R=Me, Et, SH, SMe) have been calculated using DFT method (B3LYP/6-311+G(d,p)) in terms of NBO. It has been established that substitution of methylene group by sulfur atom does not lead to the decrease in the inversion barriers due to the nN*S–H(С) interactions, since total energies of the nN*S–H(С), nNS–H(С) and nNnS interactions in the N-sulfenylimines and of the nN*С–H(С), nNС–H(С) interactions in the N-alkylimines are almost equal. The interactions of the nitrogen lone pair with the Rydberg orbitals of the sulfur atom (nNRY*S) promote the reduction of the inversion barriers of the N-sulfenylimines (by 28–33 kJ•mol–1) in comparison with the N-alkylimines. However, analysis of the total energies of all donor-acceptor and repulsive interactions between the nitrogen lone pair and the orbitals of neighboring atoms and bonds showed that they promote the increase in the inversion barriers of the N-sulfenylimines by 0.8–14.3 kJ•mol–1. The nS*C=N and nS*C=N interactions are the main factor that determines the decrease in the inversion barriers of the N-sulfenylimines relative to the N-alkylimines. These interactions, taking into account the corresponding interactions in the N-alkylimines, contribute to the barriers decrease of 64.5–71.7 kJ•mol–1.

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The structural, electronic and energy parameters in the ground and transition states of inversion of the amines H2NXHn (XHn=CH3, NH2, OH, F, SiH3, PH2, SH, and Cl) have been calculated by using DFT (PBE96/def2-tzvpp) method. It was established that the increase of electronegativity of the substituents (the X atoms within the same period) leads to stabilization of the ground and transition states of the molecules. The increase in the inversion barriers is due to relative stabilization of the ground states, but not due to relative destabilization of the transition states. The inversion barriers rise with a decrease in conformational energies of the substituents, sums of valence angles at the nitrogen atoms, negative charges on them, energies of the nitrogen lone pairs and with an increase in s-character and population of the nitrogen lone pairs and difference between the energies of the nitrogen lone pairs in the ground and transition states. The main parameters that allow predicting the change of the nitrogen inversion barriers, independently of the type or volume of the XHn substituent, are s-character of the nitrogen lone pairs and difference between the energies of the nitrogen lone pairs. In all other cases, the correlations were found only for the amines containing the elements of the same period at the nitrogen atom. All structural and electronic parameters of amines containing the Х atoms from the second period are more sensitive to the changes of the ХНn substituents than the parameters of amines containing the Х atoms from the third period.