Silatranes molecular structure

At present the molecular structures of about condensed rings with a common Si<-N bond have been determined (Table 8). The Si... N distance in these molecules varies within wide range (from 200 to 290 pm) but always remains less than the sum of van der Waals radii of silicon and nitrogen. The length of the Si<-N bond in Si-substituted silatranes XS OCH CH ljN is related linearly to the Taft inductive constant o of the substituent lsi N = 220 — 6.3 a (r = 0.947) and has a more complicated relationship with its electronegativity Ijj = 302.1... 

The principles of silatrane geometry have been discussed in a recent review article20 which considered 40 molecular structures of silatranes and silatrane-like derivatives. As these features also allow more general conclusions to be drawn for neutral pentacoordi-nate silicon complexes as a whole they will be summarized here. Derivatives... 

The energetic preference of the endo form was demonstrated by the first quantum chemical calculations of silatranes performed on 1-hydro- and 1-fluorosilatranes12,181. These calculations employed the CNDO/2 semiempirical method with spd basis set and geometries of the endo and exo forms corresponding to those obtained for 1-methylsilatrane by modified molecular mechanics method. The energy of the Si-e- N coordinative bonding was found to be about 20-25 kcalmol-1 and to be the main contributor to stabilization of the endo structure of silatranes. 

Owing to the silicon hypervalency and the cage structure, silatranes are of considerable interest from the standpoint of molecular electrochemistry. However, little work has been devoted to electrochemistry of silatranes279-281. 

Molecular and Electronic Structure of Penta- and Hexacoordinate Silicon Compounds Table 13. C Chemical Shifts (ppm) for Si-Substituent of Silatranes in CDCI3 93-69s,774-778)... 

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