Oxygen Atom Stabilization by a Main-Group Lewis Acid: Observation and Characterization of an OBeF₂ Complex with a...

Terminal oxygen radicals involving p- and d-block atoms are quite common, but s-block compounds with an oxygen radical character remain rare. Here, we report that alkaline-earth metal beryllium atoms react with OF₂ to form the oxygen beryllium fluorides OBeF and OBeF₂. These species are characterized by matrix-isolation infrared spectroscopy with isotopic substitution and quantum-chemical calculations. The linear molecule OBeF has a ²Π ground state with an oxyl radical character. The ³A₂ (C₂) ground state of OBeF₂ represents the unusual case of a triplet oxygen atom stabilized by a relatively weak interaction by the Lewis acidic BeF₂. The interaction involves both a donor component from oxygen to empty Be orbitals and a back-bonding contribution from fluorine substituents toward oxygen.