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

• Published in: Journal of organometallic chemistry Vol. 948; p. 121906
• Main Author: Grabowski, Sławomir J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2021
• Subjects: Beryllocenes and magnesocenes crystal structures; Coordination of Be and Mg; Half-sandwich and sandwich compounds; The cyclopentadienyl anion; Beryllocenes and magnesocenes crystal structures; Half-sandwich and sandwich compounds; The cyclopentadienyl anion; Coordination of Be and Mg
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/j.jorganchem.2021.121906

•The searches performed through the Cambridge Structural Database show that the majority of Mg sandwich and half-sandwich structures possesses coordination six, the Be counterparts are characterised mainly by coordination four.•The energy decomposition analysis show that for the Be sandwich and half-sandwich species interactions are more covalent than for magnesium counterparts.•For the magnesium half-sandwich and sandwich systems the Mg cation does not form bond orbitals with neighbours while for some beryllium structures the Be cation forms bond orbitals.•The QTAIM approach shows that the Be and Mg cations do not form covalent bonds with neighbours, only partly covalent interactions occur.•For all structures considered the electrostatic term is the most important attractive interaction. 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.