Ligand redistribution equilibria in aqueous fluoroberyllate solutions

The composition of aqueous fluoroberyllate solutions has been studied by Be -9 and F-19 NMR spectroscopy for various ratios of the beryllium and fluori ne concentrations, and at different pH values. The equilibrium constants ha ve been determined for the ligand exchange processes, which involve the spe cies [Be(OH2)(4)](2+), [BeF(OH2)(3)](+), [BeF2(OH2)(2)], [BeF3(OH2)](-), an d [BeF4](2-). These equilibria are shifted towards [BeF4](2-) at high pH. N o polynuclear fluoroberyllates have been detected. The fluoride exchange be tween the individual species is slow on the NMR time scale at room temperat ure, and separate sharp signals with the expected multiplicity are therefor e recorded. Calculated Be-9 chemical shifts are in good agreement with expe rimental data.