Ligand Redistribution Equilibria in Aqueous Fluoroberyllate Solutions

Abstract

Fluoroberyllates, Beryllium Fluoride, Ligand Redistribution, NMR Data The composition of aqueous fluoroberyllate solutions has been studied by 9Be and l9F NMR spectroscopy for various ratios of the beryllium and fluorine concentrations, and at different pH values. The equilibrium constants have been determined for the ligand exchange processes, which involve the species [Be(OH2)4]2+, [BeF(OH2)3]+, [BeF2(OH2)2], [BeF3(OH2)]_ , and [BeFzi]2 -. These equilibria are shifted towards [BeF4]2_ at high pH. No polynuclear fluo roberyllates have been detected. The fluoride exchange between the individual species is slow on the NMR time scale at room temperature, and separate sharp signals with the expected multiplicity are therefore recorded. Calculated 9Be chemical shifts are in good agreement with experimental data.

Recent Contributions to the Coordination Chemistry of Beryllium

“…The equivalent reaction of BeF 2 with liquid ammonia, however, only gives the neutral diammine adduct [BeF 2 (NH 3 ) 2 ] which is evidence for the strong Be−F bond . This is in line with the fact that even in aqueous solutions BeF 2 does not dissociate completely . Like H 2 O and NH 3 , also other strong donor ligands like tetramethylurea, pyridine, diisopropylcarbodiimide, or dimethyl sulfoxide (DMSO) can displace chloride to give dicationic complexes 114 , 115 , 116 , and 117 , respectively (Figure ).…”

Reactions of Beryllium Halides in Liquid Ammonia: The Tetraammineberyllium Cation [Be(NH3)4]2+, its Hydrolysis Products, and the Action of Be2+ as a Fluoride‐Ion Acceptor

“…This Be À F coupling constant agrees well with literature values. [15] We therefore conclude that, independent of concentration, the species in liquid ammonia solution is the molecular species [BeF 2 4 ], which would require two 9 Be resonances and different Be À F coupling patterns. Quantum chemical calculations of the chemical shift of 9 Be yielded 1.4 and 1.6 ppm at the PBE0/TZVP and CCSD(T)/cc-pVTZ levels of theory, respectively.…”

Speciation of Be2+ in acidic liquid ammonia and formation of tetra- and octanuclear beryllium amido clusters

“…Even an excess of H 2 O or NH 3 is just enough to recrystallize BeF 2 or form simple solvent adducts. 15,16 This is less pronounced in the other halides, but still present. There are plenty of adducts of BeCl 2 and even an excess of ligand does not always lead to displacement of the halides.…”

“…To obtain more information on these intermediates, four of the NMR experiments were repeated in 15 Fig. 3 (for 9 Be NMR spectra in 15 NH 3 see ESI Fig. S9 †).…”