PLANAR TETRACOORDINATED SILICON

Although much has been learned about the chemical behavior of organosilicon compounds, the field is still in its infancy and many territories remain almost untouched and much remains to be learned and discovered. 

The relatively short experience in this field has taught us that the future lies in close collaboration and joint research of theoreticians and experimentalists. The models that can be generated by calculations have become indispensible in understanding and evaluating experimental results and interpretations, and in suggesting synthetic targets 

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Protonation of 4b leads to the symmetrically substituted 3b (Scheme 3.2-3) and methylation of 4b at temperatures higher than —60 °C gives 3c (Scheme 3.2-5) [19]. In the latter reaction, 6a can be identified as an intermediate at —80 °C by 13C NMR spectroscopy [19]. Its planar-tetracoordinate carbon atom is strongly de-shielded 3 13 C = 144 ppm) as compared with tetrahedrally-coordinated carbon atoms connected to three boron and one silicon center (d 13C = 70-100 ppm). Computations for the model compounds 6A and 6B give 144 and 104 ppm, re-... 

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