Organosilsesquioxane-titanium oxide hybrids by nonhydrolytic sol-gel processes. Study of the rearrangement of Si-O-Ti bonds

Organosilsesquioxane-titanium oxide hybrids were prepared by nonhydrolytic condensation between CH(3)SiX(3) and 3/4TiY(4) (with X = Cl, Y = O(i)Pr or X = OR, Y = Cl). The two routes led to hybrids in quantitative yield without formation of Si-O-Ti bonds. The lack of Si-O-Ti bonds may be due to greater rates of homocondensation of the mixture of methylchloroalkoxysilanes and titanium chloride alkoxide initially formed by redistribution reactions and/or to the instability of the Si-O-Ti bonds, which underwent redistribution reactions to form Si-O-Si and Ti-O-Ti bonds. The intermediate formation of Si-O-Ti bonds by redistribution was indirectly evidenced in solution. The heterogeneity of the hybrids has been related mainly to this instability.