Stereoelectronic effects and the problem of the choice of model compounds for organic derivatives of a pentacoordinated silicon atom (taking silatranes as an example)

Anomeric effects at the silicon atom in silatranes XSi(OCH2CH2)(3)N and mod el trimethoxysilanes XSi(OMe)(3) (X = H, Me, SiH3, F, Cl) containing a tetr acoordinated silicon atom were studied by the MNDO and AMI methods. Unlike silatranes, the nature of substituent X pronouncedly affects the type and d egree of stereoelectronic effects on the values of X-Si-O-C dihedral angles , X-Si bond lengths, and proton affinities of trimethoxysilanes. The result s obtained indicate the necessity of modifying the set of spectral and stru ctural indications of pentacoordination of the anomeric silicon atom establ ished previously and observing the principle of conformational similarity f or compared compounds. Bicyclic organosilicon ethers XSi(OCH2)(3)CH were pr oposed to be used as models of corresponding silatranes.