Neutral Three Membered 2π Aromatic Beryllacycle having σ hole

Abstract

AbstractThe electronic structure, bonding, and reactivity of three‐membered cyclic beryllium compounds BeR (R=C2H2 (1), C2(CH3)2 (2)) were studied at the M06/def2‐TZVPP//BP86/def2‐TZVPP level of theory. The molecular orbital analysis shows that BeR is a 2π electron aromatic system with a σ‐hole on the beryllium atom. EDA‐NOCV analysis has been carried out with Be and R in their different electronic state as fragments at the BP86/TZ2P level of theory. The results reveal the preference for three bonding situations, (a) charge‐separated interaction where anionic acetylenic fragment R− forms one electron sharing and one donor‐acceptor σ‐interaction and one donor‐acceptor π interaction with Be+ having 2s02px02py12pz0 electronic configuration (A), (b) charge separated interaction where anionic acetylenic fragment R− forms one electron sharing and one donor‐acceptor σ‐interaction and one donor‐acceptor π interaction with Be+ having 2s12px02py02pz0 electronic configuration (B), and (c) neutral acetylenic fragment forms two electron sharing σ bonds and one donor‐acceptor π bond with beryllium having 2s12px02py12pz0 electronic configuration (C). BeR compounds show high proton affinity and hydride affinity. The reactivity was studied in detail with different ligands CO, NHC, cAAC, and PMe3. The reaction energy for the formation of adducts is exothermic and follows the order of cAAC>NHC>PMe3>CO.