Covalent Bonding between Be⁺and CO₂in BeOCO⁺with a Surprisingly High Antisymmetric OCO Stretching Vibration

The cationic complex BeOCO+ is produced in a solid neon matrix. Infrared absorption spectroscopic study shows that it has a very high antisymmetric OCO stretching vibration of 2418.9 cm-1, which is about 71 cm-1 blue-shifted from that of free CO2. The quantum chemical calculations are in very good agreement with the experimental observation. Depending on the theoretical method, a linear or quasi-linear structure is predicted for the cation. The analysis of the electronic structure shows that the bonding of Be+ to one oxygen atom induces very little charge migration between the two moieties, but it causes a significant change in the σ-charge distribution that strengthens the terminal C-O bond, leading to the observed blue shift. The bonding analysis reveals that the Be+ ← OCO donation results in strong binding due to the interference of the wave function and a charge polarization within the CO2 fragment and hybridization to Be+ but only negligible charge donation.