The interest to delineate the interactions between aluminum and phosphonate substrates and their relevance to Alzheimers Disease, led to the investigation of the pH-specific synthetic chemistry of the binary Al(III)-[N-(phosphonomethyl) iminodiacetic acid] (Al-NTAP) and Al(III)-[nitrilo-tris(methylene-phosphonic acid)] (Al-NTA3P) systems, in correlation with solution speciation studies. Investigation of the binary Al(III)-NTAP system afforded two new species (CH6N3)4[Al2(C5H6NPO7)2(OH)2].8H2O (1) and (NH4)2[Al2(C5H6NPO7)2(H2O)2].4H2O (2). A third compound emerged from the binary system of Al(III) with NTA3P, K8[Al2(C3H6NP3O9)2(OH)2].20H2O (3). Complexes 1, 2 and 3 were characterized by elemental analysis, FT-IR, 13C-, 31P-, 1H-NMR, and X-ray crystallography. The structures of 1, 2 and 3 reveal the presence of dinuclear complexes of octahedral Al(III). Each Al(III) center is bound to a fully deprotonated phosphonate ligand, water and hydroxo moieties. The species emerging in solution from the dissolution of 1-3 reflect the aqueous speciation of the respective systems and suggest chemical reactivities consistent with the involvement of biotoxic Al(III) in neurodegenerative diseases.