A method called “hydro·iminium·ation” makes precursors to these compounds, such as their “cyclic alkyl amino” type. A positive and a negative charge are delocalized around a heterocyclic core in “meso·ionic” examples of these compounds. The properties of these compounds can be tuned by changing their wingtip substituents. By adding two mes·it·yl groups or two adaman·tyl groups to the nitrogens of an im·id·azol·ium derivative, Anthony (*) Arduengo made stable examples of these compounds (10[1])that are called “persistent.” Spin-0 examples of these compounds can act as nucleophiles or electrophiles, while spin-1 examples of them act like diradicals. A carbon atom double bonds to a metal in the Fischer and Schrock examples of, for 10 points, what compounds that have a neutral carbon atom with six valence electrons? ■END■