STUDY OF THE HYDROLYSIS OF COMBINED AL-3+ AND GA-3+ AQUEOUS-SOLUTIONS - FORMATION OF AN EXTREMELY STABLE GAO4AL12(OH)24(H2O)127+ POLYOXYCATION

71Ga and 27Al NMR and clay mineral pillaring studies were used to investigate the hydrolysis of Al(H2O) 63+–Ga(H2O) 63+ solutions, mixed in an Al:Ga mole ratio of 12:1, and confirmed the formation of the previously proposed GaO4Al12(OH)24(H2O) 127+ polyoxycation. This species has been found to be formed in marked preference to both AlO4Al12(OH)24(H2O) 127+ and the previously identified GaO4Ga12(OH)24(H2O) 127+ ions, and further to have a much higher thermal stability in solution than either of these. It is suggested that the reason for the increased stability of the ‘GaAl12’ species is that the substitution of a larger metal into the central tetrahedral position has resulted in the formation of a less distorted structure. Copyright © 1990 John Wiley & Sons, Ltd.