Applying the Jellium model to octacarbonyl metal complexes

Kun Wang,Longjiu Cheng,Chang Xu,Dan Li

doi:10.1038/s42004-020-0285-2

Abstract

The recently reported octacarbonyl metal complexes M(CO)8 (M = Ca, Sr, Ba) feature interesting bonding structures. In these compounds, the bond order is 7, while accommodating 8 lone pairs of ligands in forming octa-coordinated complexes or ions. Here, by comparing [Ba(CO)8]2− and metal clusters of [BaBe8]2− analogically, we demonstrate that the Jellium model can not only be applied on metal clusters, but is also a useful tool to understand the electronic structures of [M(CO)8]q (M, q = Ca, 2−; Sc, 1−; Ti, 0; V, 1+; Cr, 2+; Ba, 2−). By applying the Jellium model, we find that a 20-e model with the configuration |1S2|1P6|1D10|1F2| is an appropriate description of the valence bonding structures of M(CO)8 species, where each coordinative bond contains 7/8ths of the bonding orbitals and 1/8th non-bonding orbitals.

Highlights

The recently reported octacarbonyl metal complexes M(CO)[8] (M = Ca, Sr, Ba) feature interesting bonding structures
The octacarbonyl metal complex or ion is with Oh symmetry, where the octa-coordinative field contributed by the positive center metal and eight ligands can be approximately viewed as a homogeneous spherical field or a Jellium model[12,13]
The metal cluster can be viewed as a superatom, which is comprised from positive charge of atomic nuclei and the innermost electrons, where the valence electrons are subjected to an external potential in the delocalized motion as |1S2|1P6|1D102S2|1F142P6|..., where the resulting magic numbers are 2, 8, 20, 40, .... (To distinguish the electronic shells of atoms, the super shells are depicted as capital letters.)

Summary

Introduction

On the basis of valence bond (VB) theory[9], there are eight degenerate coordination bonds and two π-backdonation bonds between metal and ligands in M(CO)[8] complexes or ions, where eight carbonyl groups provide eight lone pairs (LPs) of electrons to the center metal.

Results

Conclusion