Modelling nucleophilic substitution at silicon using solution 19F-NMR chemical shift, 1JSiF and 2JCF coupling constant data of pentacoordinate silicon compounds. Correlation with other magnetic nuclei and X-ray structures

Abstract

Solution 1 J SiF and 2 J CF NMR coupling constant and 19F-NMR chemical shift data have been analysed in a series of pentacoordinate silyl monofluoride complexes used to model nucleophilic substitution at silicon. Patterns in the data reveal strong correlations between both coupling constants and 19F-NMR chemical shifts and the degree of substitution displayed by each. Excellent correlation is obtained between the new data and our previous 13C- and 29Si-NMR studies to further confirm the validity of the NMR technique for structural correlation in solution. By pooling the X-ray crystal structures of a large number of compounds of this class from both our own results and the literature we are able to provide a possible explanation for some of the trends in the NMR data we observe in solution.