Unraveling the Bonding and Aromaticity of Pentazole, Pentaphosphole, and Cyclopentadiene Anions: A Comprehensive Study

J Am Chem Soc. 2025 Jan 8;147(1):1092-1100. doi: 10.1021/jacs.4c14515. Epub 2024 Dec 19.

Abstract

This study investigates π-delocalization, π-bonding situations, and aromaticity of the pentazolate anion ([cyclo-N5-], (a)), which was detected by Christe et al. in 2002. To gain a broader perspective, we investigated the iso-π-electronic species [cyclo-P5-] (b) and [cyclo-(CH)5-] (c). VB analyses reveal that the three studied molecules display significant resonance stabilization, as indicated by their high resonance energy values. A comprehensive analysis of aromaticity was conducted using electronic and magnetic aromaticity indices, revealing that all three anions exhibit strong π-aromaticity and relatively weak σ-aromaticity.