Theoretical study of the dimerization of aqueous beryllium cations.

The dimerization of monomeric beryllium species was studied via density functional theory (DFT) calculations, and the influences of deprotonation and substitution with various halide anions on the polymerization were explored. The results indicate that the dimerization was accomplished by aggregation followed by a nucleophilic attack reaction, and the hydrolysis that provides the nucleophilic hydroxyl group is a prerequisite for polymerization. An activation energy of 49.7 kJ mol(-1) and an aggregation energy of -52.2 kJ mol(-1) were found for the formation of Be2(OH)(H2O)6 (3+), indicating a exothermic reaction. Deprotonation promotes aggregation and increases the energy barrier to activation. Replacing a bound water with an F(-) anion makes aggregation more thermodynamically favorable, but it does not significantly change the energy barrier. It was concluded that the charge and electronegativity of the anion are crucial influences on the energy of the activation barrier, whereas the aggregation energy is influenced not only by the charge but also by the symmetry of the bridging structure in the aggregate.