(Ethyl‐, Ethenyl‐ and Ethynylsilyloxy)aluminum Compounds Generated by Heterolytic Cleavage of 1,3‐Disubstituted Disiloxanes

Abstract sym ‐Diorganodisiloxanes RH 2 SiOSiH 2 R (R = C 2 H 5 , 7 ; C 2 H 3 , 8 ; C 2 H, 9 ) are prepared by hydrolysis of organo(bromo)silanes which are available in high yields by the reaction of organo‐(phenyl)silanes with liquid HBr. Asymmetrical cleavage of these disiloxanes with AlCl 3 leads to the formation of organo‐(chloro)silanes and aluminosiloxane dimers [RH 2 SiOAlCl 2 ] 2 (R = C 2 H 5 , 10 ; C 2 H 3 , 11 ; C 2 H, 12 ). Crystal structure determinations of 11 and 12 reveal a planar centrosymmetrical SiOAl 2 OSi skeleton with three‐coordinate oxygen atoms and tetrahedral four‐coordinate aluminum atoms. Treatment of 7–9 with Me 2 AlCl yields volatile dimethylaluminumorganosilyl oxides [RH 2 SiOAlMe 2 ] x (R = C 2 H 5 , 13 ; C 2 H 3 , 14 ; C 2 H, 15 ; x = 2, 3, 4). NMR studies confirm the presence of more than one oligomer in solutions of these compounds. The asymmetrical compound (HC‐CSiH 2 O) 2 Me 3 Al 2 Cl ( 16 ), resulting from small amounts of MeAlCl 2 in the Me 2 AlCl used, is isolated as a byproduct in the synthesis of 15 . The crystal structure of 16 shows a disorder of the molecules leading to pseudosymmetry with a center of inversion.