Metallaphosphirenes with σ‐Aromaticity: Capture of Phosphorus Atom by Metalla‐Aromatics

Abstract

Abstract Unsaturated phosphorus heterocycles typically exhibit diminished π‐aromaticity. A unique entry into metallaphosphirenes featuring σ‐aromaticity within an unsaturated framework is reported. Reaction of sodium phosphaethynolate (NaOCP) with cyclic metal carbyne 1 affords phosphorus atom transfer through a formal [1 + 2] cycloaddition pathway. The formation of metallaphosphirene ring was computationally modelled using density functional theory, revealing that [1 + 2] cycloaddition involves direct nucleophilic attack step and, thus, depends on the amphiphilicity of carbyne atom. Comprehensive DFT calculations, including NICS, ACID, GIMIC, EDDB, and NOBD analysis, confirm the predominantly σ‐aromatic nature of the metal‐based phosphirene system. The reactivity of the metallaphosphirene in cycloaddition reactions is in accord with its σ‐aromaticity, which tends to retain the three‐membered heterocycle with λ 3 ‐P atom.