Relation between the Length of the Transannular Bond Si←N in 1-Substituted Silatranes and the Inductive Effect of Substituents at the Silicon Atom

Abstract

A strict linear correlation is found between the length of the coordination bond Si-N in 1-substituted silatranes XCH2Si(OCH2CH2)3N and the inductive constant σ I of substituent XCH2. This equation is also valid for other compounds of the RSi(OCH2CH2)3N type, in which silicon is bound to an sp 2-carbon atom (R = CH = CH2, Ph, 2-furyl, 2-thienyl, etc.). The deduced correlation equation allows determination of earlier unknown and refinement of existing σ 4I constants of substituents R on the basis of X-ray diffraction Si-N bond lengths in silatranes RSi(OCH2CH2)3N. Deviations from the correlation point to noninductive interaction between substituent R and the silantranyl group (R = R'O). The bond length in 1-fluorosilatrane nicely fits the deduced equation.