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.

最近报道的八羰基金属配合物 M(CO) ₈ (M = Ca, Sr, Ba) 具有有趣的键合结构。在这些化合物中，键级为7，同时容纳8个孤对配体形成八配位络合物或离子。在这里，通过类比地比较 [Ba(CO) ₈ ] ²⁻和 [BaBe ₈ ] ²⁻的金属团簇，我们证明 Jellium 模型不仅可以应用于金属团簇，而且还是理解电子团簇的有用工具[M(CO) ₈ ] ^q的结构（M，q = Ca，2−；Sc，1−；Ti，0；V，1+；Cr，2+；Ba，2−）。通过应用 Jellium 模型，我们发现配置为 |1S ² |1P的 20-e 模型⁶ |1D ¹⁰ |1F ² | _{是对 M(CO) 8}种的价键结构的适当描述，其中每个配位键包含 7/8 的键合轨道和 1/8 的非键合轨道。