Syntheses of title compounds, viz. N(CH2CH2NR)(3)E (1, E = Sb, R Me; 4, E = Bi, R = Me; 6, E Sb, R = SiMe3; 8, E = Bi, R = SiMe3), by the reaction of E(NAlk(2))(3) (3, E = Sb, Alk = Et; 5, E = Bi, Alk = Me) with N(CH2CH2NMeH)(3) (2) or N(CH2CH2NSiMe3H)(3) (7) are reported. The reactions of SbCl3 with N[CH2CH2N(Me)Li](3) or N[CH2CH2N(SiMe3)Li](3) and BiCl3 with N[CH2CH2N(SiMe3)Li](3) resulted in compounds 1, 6, and 8, respectively. Composition and structures of all novel compounds were established by H-1 and C-13 NMR spectroscopy and mass spectrometry. The X-ray structural study of 8 clearly indicated the presence of transannular interaction Bi<--N-dat in this compound, while 6 possesses a long Sb...N-dat distance. The structural data obtained from geometry optimizations on 6 and 8 reproduce experimental trends, i.e., a decrease in the E-N-dat distance from Sb to Bi. The values of electron density in E-Ndat critical point and the Laplacian of charge density for 8 indicate that a closed-shell interaction exists between the metal atom and N-dat atom.