Modification of Metal Alkoxide Precursors by Organofunctional Bidentate Ligands:Chemical Problems and Opportunities for Materials Syntheses

摘要

Bidentate ligands are potentially useful to modify metal alkoxides precursors for sol-gel processing.However,anionic bidentate ligands are needed to get a strong coordination,while di-amines as neutral bidentate ligand form coordination polymers [Ti_2(OR)_8(diamine)_2]_(infinity)when reacted with Ti(OR)_4.The Lewis acidity of metal alkoxides may cause organic side reactions.The first is the formation of ester and water in the reaction with carboxylic acids,and therefore carboxylate-substituted metal oxide clusters of the general composition M_nO_x(OH/OR)_y(OOCR)_z are obtained instead of substituted monomeric precursors.The second side reaction discussed is the cleavage of 6-diketones by metal alkoxides.Despite this side reaction,3-acetyl-6-trimethoxy-silyl-hexane-2-one is a useful compound to prepare single-source precursos for silica/metal oxide composites.