Nitrenium Ion Analogues of Nonclassical Carbocations: Cyclopropylnitrenium, Allylnitrenium, and Azetidenium Ions and Mechanisms for Their Interconversion

Cyclopropylnitrenium <b>3S</b>, allylnitreium <b>6S</b>, and azetidenium (i.e., the nitrogen analogue of cyclobutylcarbenium) ions were examined using density functional theory and a complete basis set method. Similarly to the carbon analogues, the singlet states of these species have several local minima with nonclassical bonding. Structures characterized include <b>3S</b>, an N analogue of the bisected cyclopropylcarbinyl cation, <b>11S</b>, an N analogue of the bicyclobutonium ion, and <b>6S</b>, an unsymmetric 2-azidinylcarbinyl cation.