Siloxy-substituted alumoxanes

Figure 2.41. Comparison of the core structure of (a) siloxy- substituted alumoxane gels with (b) diaspore, and (c) boehmite minerals. The aluminum and oxygen atoms are shown in blue and red, respectively. Reproduced with permission from Chem. Mater. 1992, 4, 167. Copyright 1992 American Chemical Society.

The siloxides of aluminum can be prepared in the same manner as the alkoxides and exhibit similar structural features. Interest in these compounds arose from a desire for sol-gel or polymeric precursors for aluminosilicates. Unfortunately, these compounds extensively hydrolyze, losing most of the silicon as the silanol. However, the investigation of the hydrolysis of (Et3SiO)3Al has generated considerable insight into the structure and composition of alkoxy- and siloxy-substituted alumoxane polymers, (ROAIO) . These macromolecules are now believed to have a structure related to that of boehmite. 

Kallio, K. Kauhanen, J. Activation of Siloxy-substituted Compounds and Homopolymerization of Ethylene by Different Soluble Alumoxane Gocatalysts. In Organometallic Catalysts and Olefin Polymerization Catalysts for a New Millenium-, Blom, R., Follestad, A., Rytter, E., Tilset, M., Ystenes, M., Eds. Springer Berlin, 2001 p 14. 

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