The mononuclear, four-coordinate aluminum compounds AlR 2 (BHT)L and AlR(BHT) 2 L [R=Me, Et; BHT=2,6-di-tert-butyl-4-methylphenoxide; L=2-Mepy, 4-Mepy, 2,6-Me 2 py, CH 3 CN, N(C 2 H 4 ) 3 CH, HNEt 2 , HN i Bu 2 , H 2 N t Bu,H 2 N n Bu, NH 3 , py•O] are obtained when AlR 3 is treated with the correct molar equivalent of BHT-H and the appropriate Lewis base. The reaction of AlMe 3 with pentafluorophenol yields [Me 2 Al(μ-OC 6 F 5 )] 2 . Cleavage of the phenoxide-bridged dimer by N(C 2 H 4 ) 3 CH leads to the formation of the Lewis acid-base complex. The molecular structures of several complexes have been determined by X-ray crystallography