Planar Tetracoordinate Silicon in Si₃Cu₃⁻ Cluster

Abstract

Photoelectron spectroscopy and theoretical calculations have identified the global minimum structure of the 16‐valence electron Si3Cu3‐ cluster, which features a planar tetracoordinate silicon (ptSi) in a rhombic arrangement. The Si3 and Cu3 triangles are interconnected by an Si2/Cu2 edge, forming an ordered chain‐like structure. Besides the conventional 2c‐2e σ‐bond connecting Si3 and Cu3, the stability of this cluster is reinforced by a delocalized 3c‐2e σ‐bond in Cu3 and a π‐bond in Si3. Our study provides rare experimental confirmation of a planar hypercoordinate heavier Group 14 element, opening possibilities for exploring similar structures in two‐dimensional materials.