Nitrosonium complexes of fluorene and 9,9-dimethylfluorene

The reaction of fluorene and 9,9-dimethylfluorene with nitrosonium tetrachloroaluminate was investigated using ¹H and ¹³C NMR spectroscopy with deuterium perturbation. The arising positively charged complexes with one and two nitrosonium cations are involved into an interconversion fast in the NMR time scale. The data of quantum-chemical calculations performed by DFT method (basic Λ02) indicate the higher stability of single-charged π-complexes of 2η type compared with the π-complexes corresponding to the addition of two NO⁺ cations. In the dication π-complexes the transoid position of the NO groups is more favorable than the cisoid position.