
%0 Journal Article
%A Kemmitt, T 
%A Milestone, NB 
%T The Ring Size Influence on <sup>29</sup>Si N.M.R. Chemical Shifts of Some Spirocyclic Tetra- and Penta-coordinate Diolato Silicates
%J Australian Journal of Chemistry
%D 1995/01/01
%V 48
%N 1
%P 93-102
%K 
%R https://doi.org/10.1071/CH9950093
%U https://www.publish.csiro.au/paper/CH9950093 
%X A series of tetracoordinate spirocyclic silicates has been prepared from the reaction of a range of diols with tetraethoxysilane, Si ( OEt )4. The silicates can be converted into anionic pentacoordinate silicates by reaction with KOBut/18-crown-6 in toluene. Alternatively, the pentacoordinate  spirocycles can be prepared directly without prior preparation of a tetracoordinate spiro silicate. 29Si n.m.r. studies have demonstrated that the chemical shifts are sensitive to both coordination number and ring size. Ring contributions to the 29Si chemical shifts are apparent for the five- membered ring spiro silicates, those for the pentcoordinate species being less than those for the tetracoordinate species. Acyclic and six- membered ring spiro silicates are virtually indistinguishable by 29Si n.m.r. spectroscopy, which demonstrates that no ring contribution to the chemical shift is apparent for this ring size. 
