Quantum chemical analysis of pentacoordination of the silicon atom

In the MNDO approximation with full or partial optimization of geometry, we have calculated the energy characteristics and charge redistribution in the model systems X_ax(H₃)eqSi...Y with variation in the length of the coordination bond Si Y and rehybridization of the AOs of the valence shell of the silicon atom. We have considered the formation of the complex anions X=H, F, Cl; Y=H^– (I) and the complex X=F, Y=O=CH-OH (II). Upon formation of the intramolecular coordination bond Si Y, transfer of electron density occurs to the axial and equatorial atoms surrounding the silicon. We have calculated the complexation energy (kJ/ mole): –253.9 (X=H, Y=H^–), –273.2 (X=F, Y=H^–), –298.7 (X=Cl, Y=H^–) and 72.4 for X=F, Y=O=CH-OH.Translated from Teoreticheskaya i Éksperimental'naya KhimLya, Vol. 22, No. 1, pp. 70–75, January–February, 1986.The authors thank N. M. Vitkovskii, V. G. Zakzhevkskii, and F. S. Dubnikov for cooperation in carrying out the calculations.