Modelling SN2 nucleophilic substitution at silicon by structural correlation with X-ray crystallography and NMR spectroscopy

The X-ray crystal structures of four 1-(halodimethylsilylmethyl)-2-quinolinones have been measured and used to model the reaction profile for nucleophilic substitution at silicon. Similar structural correlations have been performed in solution, the percentage SiO bond formation being obtained from the 13C chemical shifts of the quinolinone carbons and the extent of pentacoordination from the 29Si chemical shift of the silicon. Excellent agreement is obtained between the two methods confirming the validity of the NMR technique for structural correlation in solution.