Li₆ E₅ Li₆ : Tetrel Sandwich Complexes with 10-π-Electrons

Area of Science:

• Inorganic Chemistry
• Theoretical Chemistry
• Materials Science

Background:

• Hückel's rule defines aromaticity based on (4n+2) π-electrons in planar rings.
• Ten π-electrons are typically expected to confer aromaticity.
• Previous studies have not identified stable systems with ten π-electrons in a central ring.

Purpose of the Study:

• To investigate novel sandwich structures with ten π-electrons.
• To explore the electronic properties and stability of E5 rings (E=Si-Pb).
• To understand the nature of aromaticity in these unique systems.

Main Methods:

• Computational modeling and theoretical calculations were employed.
• Analysis of D5h Li6E5Li6 sandwich structures.
• Investigation of electron delocalization and ring current effects.

Main Results:

• First global minima structures for ten π-electron E5 rings (E=Si-Pb) were identified.
• The ten π-electrons were found to localize as five π-lone-pairs, not delocalized orbitals.
• High symmetry structures are stabilized by σ-aromaticity, leading to diatropic ring currents.

Conclusions:

• The discovered systems exhibit σ-aromaticity, a deviation from conventional π-aromaticity.
• Elements from silicon to lead favor this σ-aromatic stabilization.
• These findings expand the understanding of aromaticity and chemical bonding in heavy elements.