N-lithio-2,2,6,6-tetramethylpiperidine [Li(tmp)] reacts with AlX3 (X = Cl, Br) in Et2O/n-hexane soln. to generate of substitution and ether cleavage products, [(tmp)Al(X)(m-OEt)]2 (X = Cl, Br). However, when the reaction is allowed to proceed in n-hexane alone, an almost quant. yield of (tmp)2AlX (X = Cl, Br, I) is obtained. According to 27Al NMR, mass spectroscopy, cryoscopy, and x-ray crystal structure detns., these compds. are monomeric in the solid state, in soln., and in gas phase. (Tmp)2AlBr reacts with AgBF4 yielding the fluoride-bridged dimer [(tmp)2AlF]2 as shown by x-ray crystal structure detn. [on SciFinder (R)]