Nitrosonium complexes of [2.2]paracyclophane

The reaction of 2.2]paracyclophane with nitrosonium tetrachloroaluminate was studied by NMR (¹H, ¹³C) spectroscopy using deuterium isotopic perturbation technique. The resulting cationic complexes containing one and two nitrosonium ions are involved in fast (on the NMR time scale) interconversion. Quantum-chemical calculations performed on the DFT level (using triple zeta basis set) indicate the higher stability of 2η single-charged π-complexes relative to σ complexes corresponding to the addition of NO⁺ ion at the ipso and ortho positions. The formation of the single-charged π-complex is energetically more favorable, compared to the double-charged π-complex. The affinity of NO⁺ for 2.2]paracyclophane is much greater than for p-xylene, presumably due to stacking interaction between the aromatic rings in the π-complex.