Catalytic Effect of Chemically Modified Metal Alkoxides on Hydrolysis and Condensation Reactions of Methyl- and Phenyl-Ethoxysilanes

Abstract

The catalytic effect of chemically modified metal alkoxides on the hydrolysis and condensation reactions of methylethoxysilanes and phenylethoxysilanes was investigated by ²⁹Si nuclear magnetic resonance spectroscopy and gel permeation chromatography. Metal alkoxides such as Al(O-sec-C₄H₉)₃, Ti(O-iso-C₃H₇)₄ and Nb(OC₂H₅)₅ modified with ethyl acetoacetate accelerated not only the condensation reactions but also the hydrolysis reactions of methyl- and phenyl-alkoxysilanes. The catalytic effect of these metal alkoxides was found to be different between methyl- and phenyl-alkoxysilanes. The catalytic activity increases in the order of Nb<Al<Ti alkoxides in the case of methyl-ethoxysilanes, whereas in the case of phenyl-ethoxysilanes it increases in the order of Nb<Ti<Al alkoxides. The difference in catalytic activity was discussed on the basis of the partial charge of M in metal alkoxide, the difference in electronegativity between M and Si and the difference between the coordination number and valence of M.