Derivatives of silicic acids as model compounds for silicates

Silicon-29 chemical shifts of methyl, ethyl, chloro and trimethylsilyl derivatives of silicic acids are compared to those of silicic acid anions found in aqueous solutions. Although the chemical shifts of the silicate anions vary with pH and concentration, a good correlation is obtained for the chloro and alkoxi derivatives. The chemical shifts of the trimethylsilyl esters are of limited comparability to the data of the silicates only.