1,4-Dialumination of benzene by sodium and potassium aluminyls

Under forcing conditions, the aluminyls [AM{Al(NON)}]₂ ([NON]²⁻ = [O(SiMe₂NDipp)₂]²⁻, Dipp = 2,6-iPr₂C₆H₃, AM = Na, K) react with benzene to give the 1,4-phenylene di(hydrido)aluminate complexes, AM₂[1,4-{Al(NON)(H)}₂(C₆H₄)]. Crystal structure analysis of the products shows that the ’Al(NON)(H)’ groups are in the plane of the para-substituted C₆-ring, with the alkali metals above and below forming an inverse sandwich structure. Density functional theory calculations were performed to analyse the mechanism leading to the di-substituted product. Results identify a viable dimeric pathway and show that each alumination step is preceded by a Meisenheimer-type intermediate leading to the observed trans-dialuminated product.