Ring Currents as Probes of the Aromaticity of Inorganic Monocycles : P₅⁻, As₅⁻, S₂N₂, S₃N₃⁻, S₄N₃⁺, S₄N₄²⁺, S₅N₅⁺, S₄²⁺ and Se₄²⁺

Abstract

Abstract Current‐density maps were calculated by the ipsocentric CTOCD‐DZ/6‐311G** (CTOCD‐DZ=continuous transformation of origin of current density‐diamagnetic zero) approach for three sets of inorganic monocycles: S 4 2+ , Se 4 2+ , S 2 N 2 , P 5 − and As 5 − with 6 π electrons; S 3 N 3 − , S 4 N 3 + and S 4 N 4 2+ with 10 π electrons; and S 5 N 5 + with 14 π electrons. Ipsocentric orbital analysis was used to partition the currents into contributions from small groups of active electrons and to interpret the contributions in terms of symmetry‐ and energy‐based selection rules. All nine systems were found to support diatropic π currents, reinforced by σ circulations in P 5 − , As 5 − , S 3 N 3 − , S 4 N 3 + , S 4 N 4 2+ and S 5 N 5 + , but opposed by them in S 4 2+ , Se 4 2+ and S 2 N 2 . The opposition of π and σ effects in the four‐membered rings is compatible with height profiles of calculated NICS (nucleus‐independent chemical shifts).