Aluminosiloxane compounds. Part III. Polyaluminium-organosiloxanes: synthesis, and investigation of structure

Abstract

The action of dichloro- or dibromo-trimethylsiloxyaluminium on octamethylcyclotetrasiloxane leads to the formation of polyaluminium-organosiloxanes. With dichlorotrimethylsiloxyaluminium in two- or three-fold excess, the polymer produced has empirical formula [C₂H₆AlClO₂Si]_n, and in four-fold exess, [C₆H₁₈Al₄Cl₄O₇Si₃]_n. The polymers obtained using dibromotrimethylsiloxyaluminium have a more complicated structure. The chloro-and bromo-polymers obtained are amorphous solids, stable to heat, infusible below 300°, which are easily hydrolysed by moisture owing to the presence of Al–X bonds (X = Cl or Br). Replacement of X by acetylacetonte groups by the action of sodium acetylacetonate leads to polyorgano-aluminosiloxanes which are more stable to hydrolysis. The interpretation of this substitution reaction provides useful information about the structure of the halogen-containing polymers. The interpretation presented is largely based on the descriptions, given in the two preceding Papers, of the structures of the dihalogenotrimethylsiloxyaluminiums and the compounds of formula C₈H₂₄Al₃X₅O₆Si₄(X = Cl or Br), and of their reactions with sodium acetylacetonate.