arenium ions

https://doi.org/10.1351/goldbook.A00436

Cations derived formally by the addition of a hydron or other cationic species to any position of an arene, e.g. C₆H₇⁺, benzenium. The term includes:

Arenium σ-adducts (Wheland intermediates) (which are considered to be intermediates in electrophilic aromatic substitution reactions) and other cyclohexadienyl cations.
A00436-1.png
Arenium π-adducts, such as:
A00436-2.png

[σ-adduct (sigma-adduct), π-adduct (pi-adduct)].

Source:
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1318 (https://doi.org/10.1351/pac199567081307)

See also:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1077 [Terms] [Paper]