Nitrosonium complexes

Bicumene readily forms a highly colored charge-transfer complex with nitro-sonium (NO+) cation that can be isolated as a crystalline salt.194 Thus, a solution of bicumene and NO+SbClcharge-transfer bands with A = 338 and 420 nm that are indistinguishable from those of the nitrosonium complexes with other methylbenzenes (equation 62). 

Among complexes of organic compounds with N-centered electrophiles, a special position is occupied by the nitrosonium complexes. Interest in these complexes has not diminished over the years as they are intermediates in several important organic reactions, such as nitrosation of aromatic compounds (35),... 

Nitrosonium complexes 20a-d of l-R-2-methylacenaphthylenes 21a-d (Scheme 15) can be considered as complexes with two-electron ligands, as unlike complexes of other polycyclic aromatic compounds (8, 52), nitrosonium... 

Figure 1. Schematic representation of the nitrosonium complexes of 2,3-dimethyl-2-butene. Distances are in angstroms and angles are in degrees, the values correspond to the HF/6-31G optimized structures.

It is known that the nitrosonium cation is a strong oxidant (54). In (55) it was found by multinuclear NMR ( H, 13C, 19F and 14N) that the interaction of nitrosonium tetrafluoroborate with 2,2,6,6-tetramethyl-4-R-piperidine-1 -oxyl radicals 22a-e resulted in formation of 4-R-2,2,6,6-tetramethylpiperidine-l-oxoammonium tetrafluoroborates (Scheme 16). Cations 23a-e could be classified as nitrosonium complexes of biradicals 24a-e. 

To date the structure and reactivity of numerous complexes derived from aromatic compounds and nitrosonium cation have been studied (5, 56-63). However, relatively few studies are available on the nitrosonium complexes of cyclophanes (5, 57, 59, 61, 62), cf ref. (63). The interaction of [2.2]paracyclophane with nitrosonium tetrachloroaluminate was studied by H and 13C NMR spectroscopy using deuterium isotope perturbation technique (64). It was found that the resulting nitrosonium complexes containing one (25) or two NO groups (26) are involved in fast interconversion (on the NMR time scale) (Scheme 17). 

Figure 2. Optimized structures of the nitrosonium complexes of [2.2]paracyclophane at DFT/3Z. Distances are in angstroms.

Analogous rearrangement is also observed for the nitrosonium complex of 1,10-phenanthroline (53) (Scheme 22) (52-55). 

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