Global Planar Tetra‐, Penta‐ and Hexa‐coordinate Silicon Clusters Constructed by Decorating SiO3 with Alkali Metals

The achievement of the rule-breaking planar hypercoordinate motifs (carbon and other elements) is mainly attributed to a practical electronic stabilization mechanism, where the bonding of the central atom pz π electrons is a crucial issue. We have demonstrated that strong multiple bonds between the central atom and partial ligands can be an effective approach to explore stable planar hypercoordinate species. A set of planar tetra-, penta- and hexa-coordinate silicon clusters were herein found to be the lowest-energy structure, which can be viewed as decorating SiO3 by alkali metals in the MSiO3- , M2 SiO3 and M3 SiO3+ (M=Li, Na) clusters. The strong charge transfer from M atoms to SiO3 effectively results in [M]+ SiO32- , [M2 ]2+ SiO32- and [M3 ]3+ SiO32- salt complexes, where the Si-O multiple bonding and structural integrity of the Benz-like SiO3 framework is maintained better than the corresponding SiO32- motifs. The bonding between M atoms and SiO3 motif is best described as M+ forming a few dative interactions by employing its vacant s, p, and high-lying d orbitals. These considerable M←SiO3 interactions and Si-O multiple bonding give rise to the highly stable planar hypercoordinate silicon clusters.