Oxygen Atom Stabilization by a Main-Group Lewis Acid: Observation and Characterization of an OBeF 2 Complex with a Triplet Ground State.

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 OF ₂ to form the oxygen beryllium fluorides OBeF and OBeF ₂ . These species are characterized by matrix-isolation infrared spectroscopy with isotopic substitution and quantum-chemical calculations. The linear molecule OBeF has a ² Π ground state with an oxyl radical character. The ³ A ₂ ( C _{2 v} ) ground state of OBeF ₂ represents the unusual case of a triplet oxygen atom stabilized by a relatively weak interaction by the Lewis acidic BeF ₂ . The interaction involves both a donor component from oxygen to empty Be orbitals and a back-bonding contribution from fluorine substituents toward oxygen.