An ab initio study of the effect on the 29Si NMR chemical shift of dihydroxysilane of geometry changes expected on approach to a surface

29Si nuclear magnetic resonance spectroscopy has shown that when dialkoxysilanes are milled with magnesium chloride, a component of the Ziegler-Natta catalyst, the 29Si nucleus becomes more deshielded. Calculations on the change in 29Si NMR shielding when the SiO bond distances and OSiO bond angle vary are reported for the model compound silanediol. The results indicate that changes in geometry do not produce a sufficiently large change in 29Si NMR shielding and the conclusion is drawn that the deshielding is due to interaction of the dialkoxysilanes with the magnesium chloride surface.