Theoretical predictions of aromatic Be-O rings

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); C H BeO, C H Be O , and Be O . All species retain a planar geometry. We considered both bare complexes and Be coordinated with L = CO, pyridine, PMe , 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 C H BeO (3), and C H Be(CO), which have negative NICS(1) values and minima in the NICS-scan. Coordination of two ligands to make the Be four-coordinate disrupts ring planarity and reduces aromatic character.