Ternary complexes of Al3+ and F- with a third ligand

Al3+ binds fluoride more strongly than sixty other metal ions. Binary stability constants are recommended for four ionic strengths from 0.0 to 0.5 M. Ternary complexes with hydroxide become important in neutral solutions. Competition between fluoride and hydroxide occurs for scarce sites on a metal ion highly chelated by a ligand such as EDTA. Under the conditions of experiments with G-proteins, the main solution species are hexacoordinate (H2O)(2)(HO)AlF3- at pH 7.5 and hexacoordinate (H2O)(2)AlF4- at pH 6.0. Crystal structure determinations show that on a G-protein a beta-phosphate oxygen substitutes for a water molecule on the species in solution.