Prediction of Covalent Metal‐Metal Bonding in Cp−M−M’‐Nacnac Complexes of Group 2 and 12 Metals (Be, Mg, Ca, Zn, Cd, Hg)

Abstract

Bimetallic CpMM'Nacnac molecules with group 2 and 12 metals (M = Be, Mg, Ca, Zn, Cd, Hg) that contain novel metal‐metal bonding have been investigated in a theoretical study of their molecular and electronic structure, thermodynamic stability, and metal‐metal bonding. In all cases the metal‐metal bonds are characterized as electron‐sharing covalent single bonds from natural bond orbital (NBO) and energy‐decomposition analysis with natural orbitals of chemical valence (EDA‐NOCV) analysis. The sum of [MM'] charges is relatively constant, with all complexes exhibiting a [MM']2+ core. Quantum theory of atoms in molecules (QTAIM) analysis indicates the presence of non‐nuclear attractors (NNA) in the metal‐metal bonds of the BeBe, MgMg, and CaCa complexes. There is substantial electron density (0.75‐1.33 e) associated with the NNAs, which indicates that these metal‐metal bonds, while classified as covalent electron‐sharing bonds, retain significant metallic character that can be associated with reducing reactivity of the complex. The predicted stability of these complexes, combined with their novel covalent metal‐metal bonding and potential as reducing agents, make them appealing targets for the synthesis of new metal‐metal bonds.