Star-like Cluster S₆Mg₅^2-: A Binary Dianion Global Minimum Featuring a Planar Pentacoordinate Sulfur

Area of Science:

• Computational Chemistry
• Materials Science
• Inorganic Chemistry

Background:

• Clusters with unconventional bonding exhibit unique electronic properties.
• Planar pentacoordinate structures are rare, especially involving sulfur.

Purpose of the Study:

• To report the first binary dianion cluster with a planar pentacoordinate sulfur (ppS) atom.
• To investigate the electronic structure and stability of this novel cluster.

Main Methods:

• High-level ab initio calculations.
• Born-Oppenheimer molecular dynamics (BOMD) simulations.
• Bonding analyses.

Main Results:

• The global minimum of S₆Mg₅^2- adopts a singlet state with D_5h symmetry.
• Electrostatic forces dominate interactions between the central ppS atom and the Mg₅S₅ framework.
• The cluster exhibits high molecular rigidity and dynamic stability up to 1000 K, with a HOMO-LUMO gap of 4.62 eV and VDE of 2.49 eV.

Conclusions:

• This discovery challenges conventional bonding paradigms for planar hypercoordinate structures.
• The findings deepen the understanding of ppS-containing clusters.
• This work significantly advances the field of planar hypercoordination chemistry.