A methylene bridged dialuminium compound as a chelating Lewis acid -: complexation of azide and acetate anions by R2Al-CH2-AlR2 [R = CH(SiMe3)2]

Suspensions of sodium azide or sodium acetate in diethyl ether were treated with the methylene bridged dialuminium compound R2Al-CH2-AlR2 [R=CH(SiMe3)(2)] 1, which has two coordinatively unsaturated aluminium atoms, and the crown ether [18]crown-6 for the coordination of the sodium ions. In both cases, compound 1 reacted as a chelating Lewis acid, and the salts readily dissolved at room temperature. As shown by crystal structure determinations of the products 7 (azide) and 8 (acetate), six-membered heterocycles were formed by the coordination of both aluminium atoms to the terminal nitrogen atoms of the linear azido group or both oxygen atoms of the acetato group. Each product crystallized with the cation [Na([18]crown-6)(iPr(2)O)](+). (C) 1999 Elsevier Science S.A. All rights reserved.