Nitrogen atoms nitrenium ions

At least two types of nitrenium ions, the nitrogen analogs of carbocations, can exist as intermediates, though much less work has been done in this area than on carbocations. In one type (46), the nitrogen is bonded to two atoms and in the other... 

A paper has reported that nitrogen-centred radicals (29) have been generated by one-electron reduction (at carbon or metal electrodes) of stable nitrenium ions of the general structure (28). The reactivity of the radicals is influenced by the substituents attached to the two nitrogen atoms that are directly linked to the ion nitrenium centre." ... 

Nitrenium ions are isoelectronic to carbenes [177]. They contain a dicoordinated nitrogen atom formally with two valence electrons. The possible electronic structures of the parent nitrenium ion NHj are shown in Figure 7.9. On the basis of Hiickel MO theory one would expect that the lowest energy configuration, that is, the electronic ground... 

This type of transformation of a cationic center into an anionic center is unlikely to be unique and should be of significant synthetic utility. For example, preliminary calculations predict that the corresponding diphosphino nitrenium ions should exist in the cyclic form, with a negatively charged nitrogen atom. 

The formation of a covalent bond to the nitrenium nitrogen atom by an oxygen-centered nucleophile is not a favorable reaction on the basis of HSAB and would in many cases be a futile reaction in that the arylhydroxylamine (or arylhydroxamic acid) compound or its 0-ester is regenerated. Hydration of a primary arylnitrenium ion at the nitrogen results in an arylhydroxylamine (or arylhydroxamic acid) compound. However, experimental observations suggest that this is a minor reaction in many cases (53, 82). The formation of arylhydroxylamine or arylhydroxamic acid compounds in reactions of analogous O-esters is most often the result of solvolysis of the ester and not the result of hydration of the nitrenium ion at nitrogen. 

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