Viability of aromatic all-pnictogen anions

Abstract

Aromaticity in novel cyclic all-pnictogen heterocyclic anions, P₂N₃⁻ and P₃N₂⁻, and in their heavier analogues is studied using quantum mechanical computations. All geometrical parameters from optimized geometry, bonding, electron density analysis from quantum theory of atoms in molecules, nucleus-independent chemical shift, and ring current density plots support their aromaticity. The aromatic nature of these molecules closely resembles that of the prototypical aromatic anion, C₅H₅⁻. These singlet C_2v symmetric molecules are comprised of five distinct canonical structures and are stable up to at least 1000 fs without any significant distortion. Mechanistic study revealed a plausible synthetic pathway for P₃N₂⁻ – a click reaction between N₂ and P₃⁻, through a C_2v symmetric transition state. Besides this, the possibility of P₃N₂⁻ as a η⁵-ligand in metallocenes is studied and the nature of bonding in metallocenes is discussed through the energy decomposition analysis.