Global Planar Tetra-, Penta- and Hexa-coordinate Silicon Clusters Constructed by Decorating SiO 3 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 p z 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 SiO 3 by alkali metals in the MSiO 3 - , M 2 SiO 3 and M 3 SiO 3 + (M=Li, Na) clusters. The strong charge transfer from M atoms to SiO 3 effectively results in [M] + SiO 3 2- , [M 2 ] 2+ SiO 3 2- and [M 3 ] 3+ SiO 3 2- salt complexes, where the Si-O multiple bonding and structural integrity of the Benz-like SiO 3 framework is maintained better than the corresponding SiO 3 2- motifs. The bonding between M atoms and SiO 3 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←SiO 3 interactions and Si-O multiple bonding give rise to the highly stable planar hypercoordinate silicon clusters.