Aluminosiloxane compounds. Part I. Dichloro- and dibromotrimethylsiloxyaluminium: structure, and reaction with sodium acetylacetonate

Abstract

The reactions of sodium acetylacetonate with dichloro- and dibromo-trimethylsiloxyaluminium proceed in the same way. In both cases the products are (a) ethoxytrimethylsilane and hexamethyldisiloxane in the volatile fraction, (b) aluminium acetylacetonte in a yield corresponding to half the aluminium present in the starting compound, and (c) alumoxane co-ordination polymers, containing acetylacetone as chelating agent, to which the formula –O_0·5–[graphic omitted]–O–[–Al(acac)–O–]–₃ has been assigned. The molecular weight of these polymers lies between 500 and 1000. Their infrared spectra (in the range 2000–600 cm^–1) show the existence of acetylacetonate groups chelated to aluminium, and the presence of Al–O–Al bonds. A reaction mechanism is proposed to explain these facts.