Theoretical predictions of aromatic Be–O rings

Abstract

We have carried out a theoretical investigation of benzene substituted with BeO to assess stability and aromatic properties (with 1–3 BeO units in a six-membered ring); C₄H₄BeO, C₂H₂Be₂O₂, and Be₃O₃. All species retain a planar geometry. We considered both bare complexes and Be coordinated with L = CO, pyridine, PMe₃, and NHC. Coordination of a ligand to Be atoms causes increased Be–O bond distances. Aromatic character has been investigated with NICS and NICS-scan calculations, EDA analysis, as well as considering the energetics of hydrogenation. The complexes with the greatest aromatic character are C₄H₄BeO (3), and C₄H₄Be(CO), which have negative NICS(1)_zz values and minima in the NICS-scan. Coordination of two ligands to make the Be four-coordinate disrupts ring planarity and reduces aromatic character.