All‐Metallic Zn=Zn Double‐π Bonded Octahedral Zn2M4 (M=Li, Na) Clusters with Negative Oxidation State of Zinc

Zn=Zn double bonded‐especially double‐π bonded‐systems are scarce due to strong Coulomb repulsion caused by the Zn atom's internally crowded d electrons and very high energy of the virtual π orbitals in Zn2 fragments. It is also rare for Zn atoms to exhibit negative oxidation states within reported Zn−Zn bonded complexes. Herein, we report Zn=Zn double‐π bonded octahedral clusters Zn2M4 (M=Li, Na) bridged by four alkali metal ligands, in which the central Zn atom is in a negative oxidation state. Especially in D4h−Zn2Na4, the natural population analysis shows that the charge of the Zn atom reaches up to −0.89 |e| (−1.11 |e| for AIM charge). Although this cooperation inevitably increases the repulsion between two Zn atoms, the introduction of the s1‐type ligands results in occupation of degenerated π orbitals and the electrons being delocalized over the whole octahedral framework as well, in turn stabilizing the octahedral molecular structure. This study demonstrates that maintaining the degeneracy of the π orbitals and introducing electrons from equatorial plane are effective means to construct double‐π bonds between transitional metals. Alkali metal supported Zn=Zn double‐π bond with negative oxidation state of Zinc. Zn=Zn double‐π bonded octahedral clusters Zn2M4 (M=Li, Na) bridged by four alkali metal ligands, in which the central Zn atom is in a negative oxidation state, are studied theoretically.