Synthesis and characterization of P2N3-: An aromatic ion composed of phosphorus and nitrogen

Aromaticity is predominantly associated with carbon-rich compounds but can also occur in all-inorganic ones. We report the synthesis of the diphosphatriazolate anion, a rare example of a planar aromatic inorganic species. Treatment of azide (N-3(-)) in tetrahydrofuran solution with P(2)A(2) (A = C14H10), a source of P-2, produced P2N3-, which we isolated as its [Na-kryptofix-221](+) salt in 22% yield and characterized by single-crystal x-ray diffraction. Salts [Na-kryptofix-221] [P2N3] and [Na-kryptofix-221] [(P2NN2)-N-15] were analyzed by infrared and Raman spectroscopy, N-15 and P-31 nuclear magnetic resonance spectroscopy, and mass spectrometry. The formation of the P2N3- anion was investigated using density functional theory, and its aromatic character was confirmed by NICS (nucleus-independent chemical shift) and QTAIM (quantum theory of atoms in molecules) methods.