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)₃N and model trimethoxysilanes XSi(OMe)₃ (X=H, Me, SiH₃, F, Cl) containing a tetracoordinated silicon atom were studied by the MNDO and AM1 methods. Unlike silatranes, the nature of substituent X pronouncedly affects the type and degree of stereoelectronic effects on the values of X−Si−O−C dihedral angles, X−Si bond lengths, and proton affinities of trimethoxysilanes. The results obtained indicate the necessity of modifying the set of spectral and structural indications of pentacoordination of the anomeric silicon atom established previously and observing the principle of conformational similarity for compared compounds. Bicyclic organosilicon ethers XSi(OCH₂)₃CH were proposed to be used as models of corresponding silatranes. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1061–1065, June, 1999.