Singlet stabilisation of parent nitrenium ion
Abstract
The parent nitrenium ion generated from N-aminopyridinium, S-aminosulphonium, or N-aminobipyridinium salts interacts with both the unshared electron pair of the heteroatom of pyridine, sulphide, or bipyridyl and the gegen anion by hydrogen bonding; the singlet nitrenium ion is stabilised by this interaction, and the stabilised singlet state undergoes fast singlet → triplet conversion in the presence of molecular oxygen or chlorine.