Ten planar pentacoordinate boron (ppB) systems are reported, each featuring a pentagonal ring composed of tetrels, pnictogens, or their combination around boron. These structures exhibit double aromaticity (σ and π), consistent with Hückel's 4n+2 rule, as confirmed by magnetically induced current density analysis.

This study introduces systems with planar tetracoordinate group 13–15 atoms (E) in pentagonal C₄H₂E rings bridged by Si or Ge.

A systematic search over cationic clusters N(XE) ₄ ⁺ (X = B–Tl, E = O–Po) uncovers eight new planar-tetracoordinate-nitrogen species: N©(AlPo) ₄ ⁺ , N©(GaE) ₄ ⁺ (E = Se–Po) and N©(InE) ₄ ⁺ (E = S–Po).

The aromaticity of small boron clusters remains under scrutiny due to persistent inconsistencies between magnetic and electronic descriptors. Here, we reexamine B₃⁻, B₃⁺, B₄, B₄²⁺, and B₄²⁻ using a multidimensional approach that integrates Adaptive Natural Density Partitioning, Electron Density of Delocalized Bonds, magnetically induced current density, and the z-component of the induced magnetic field. We introduce a model in which σ-aromaticity arises from two distinct delocalization topologies: a radial 2e⁻ σ-pathway and a tangential multicenter circuit formed by alternating filled and vacant sp² orbitals. This framework accounts for the evolution of aromaticity upon oxidation or reduction, preserving coherence between electronic structure and magnetic response. B₃⁻ features cooperative radial and tangential σ-delocalization, together with a delocalized 2e⁻ π-bond, yielding robust double aromaticity. B₃⁺ retains σ- and π-aromaticity, but only via a tangential 6e⁻ σ-framework, leading to a more compact delocalization and slightly attenuated ring currents. In B₄, the presence of a radial 2e⁻ σ-bond and a 4c–2e π-bond confers partial aromatic character, while the tangential 8e⁻ σ-framework satisfies the 4n rule and induces a paratropic current. In contrast, B₄²⁺ lacks the radial σ-component but retains a tangential 8e⁻ σ-circuit and a 2e⁻ 4c–2e π-bond, leading to a σ-antiaromatic and π-aromatic configuration. Finally, B₄²⁻, exhibits delocalized π- and σ-circuits, yielding consistent diatropic ring currents, which confirms its fully doubly aromatic nature. Altogether, this analysis underscores the importance of resolving σ-framework topology and demonstrates that, when radial and tangential contributions are correctly distinguished, Hückel’s rule remains a powerful tool for interpreting aromaticity in small boron rings.

Unlike benzene, planar boron clusters proposed as benzene analogues are σ-dominant aromatic systems.

A D _4h screening of the 25 H©M ₄ X ₄ ⁻ combinations (M = Li–Cs; X = F–At), followed by unbiased global‐minimum searches on the nine vibrationally stable candidates, reveals eight previously unreported planar tetracoordinate hydrogen (ptH) global minima adopting D _4h symmetry, bringing the total number of known D _4h ptH clusters in the alkali‐metal–halogen family to nine. Born–Oppenheimer molecular dynamics confirms dynamic stability at 300 K across the entire series, with thermal isomerization observed at 600 K in three of the nine clusters. In all cases, the central hydrogen carries a substantial negative charge and is stabilized predominantly by electrostatic H ⁻ ···M ⁺ interactions, while the peripheral M–X framework compensates the intrinsic metal–metal repulsion and preserves the planar arrangement. Although a small non‐Coulombic contribution exists within the M–X framework, multicenter bonding plays no significant role in the stabilization of the central hydrogen. The magnetic response is dominated by localized diatropic vortices at the atomic cores, with no evidence of a global ring current, confirming the nonaromatic character of these assemblies. These results reframe ptH stabilization within a predominantly electrostatic framework and provide a predictive framework for further expansion of this emerging family.