Silatranes XSi(OCH2CH2)(3)N exhibit a good linear relationship between their experimental and calculated (IGLO and GIAO) values of the NMR chemical shifts of N-15, delta(N), and the lengths of dative bonds Si <- N, d(SiN), determined in the gas phase (ED, CCSD), solutions (COSMO PBE0, B3PW91), and crystals (X-ray). An aggregate of the obtained data provides strong evidence that the gas-phase value of d(SiN) in MeSi(OCH2CH2)(3)N should be greater by similar to 0.05 angstrom than that determined in the electron diffraction (ED) experiment (2.45 angstrom). Given this condition, a long-standing contradiction between the data of the structural (X-ray, ED) and NMR N-15 experiments for the molecules of 1-methyl- and 1-fluorosilatrane regarding the sensitivity of their coordination contact Si <- N to the medium effect is resolved.