The coordination of beryllium and magnesium centres in half-sandwich and sandwich compounds

Abstract

BP86-D3/TZ2P calculations were performed on half-sandwich and sandwich beryllium and magnesium moieties. The Cp−-Be2+-X− and Cp−-Mg2+-X−, half-sandwich species are considered, where X = Cl or Br while Cp marks the cyclopentadienyl, C5H5−, or pentamethylcyclopentadienyl, C5Me5−, anion; the C5H5−-Be2+-C5H5− and C5H5−-Mg2+- C5H5− sandwich species are analysed. The Quantum Theory of Atoms in Molecules (QTAIM), the Natural Bond Orbitals (NBO) and the Energy Decomposition Analysis (EDA) approaches were also applied to analyse these systems. The results of calculations show that beryllium and magnesium species are governed mainly by electrostatic interactions but a covalent character of interactions is also pronounced, more for beryllium systems than for magnesium ones. The EDA calculations show that the Cp-Be and Cp-Mg interactions are stronger and “more covalent” than the corresponding Be-X and Mg-X interactions. The Cambridge Structural Database (CSD) searches were carried out to find half-sandwich and sandwich beryllium and magnesium species that correspond to systems analysed theoretically here.