Infrared Spectroscopic and Electronic Structure Investigations of Beryllium Halide Molecules, Cations, and Anions in Noble Gas Matrices

Laser-ablated Be atoms, cations, and electrons were reacted with F₂, ClF, Cl₂, NF₃, CCl₄, CF₂Cl₂, HCl, DCl, and SiCl₄ diluted in noble gases. The major products were the dihalides BeF₂, BeClF, BeCl₂, and the hydride chloride HBeCl, whose identities were confirmed by comparison with previous evaporative work, deuterium substitution, and vibrational frequency calculations. The matrix-isolated fundamental frequency of the BeF molecule is higher, and the frequency of BeCl is lower, than that determined for the gas-phase molecules. The BeF⁺ and BeCl⁺ cations formed strong dipole-induced dipole complexes in solid Ne, Ar, Kr, and Xe with stepwise increase in computed noble gas dissociation energies. Going down the family NgBeF⁺ and NgBeCl⁺ series (Ng = Ne, Ar, Kr, Xe) the Mulliken charges q­(Be) decrease, while q­(Ng) increases, and the dipole moments decrease, which suggests covalent bonding in the xenon species. We find that the largest intramatrix shift is Ne to Ar which follows the largest factor increase for the Ng atomic polarizabilities. Extra electrons produce Cl^–, which reacts with HCl to form the stable HCl₂^– anion and possibly with BeCl₂ to give BeCl₃^–. A weak band observed in neon experiments with F₂ is probably due to BeF₃<sup>–