Modern Criteria of Aromaticity for Organometallic Compounds

Aromaticity as one of the most important fundamental concepts in chemistry is an effect of cyclic electron delocalization, which is very multifaceted and difficult to measure. To define the aromaticity degree as a quantitative characteristic, the aromaticity indices are used that can be divided into energetic, structural, electronic, magnetic, and optical. The aromaticity effect went far beyond the class of π-conjugated hydrocarbons a long time ago; therefore, this review critically examines the most important and modern criteria of aromaticity which are universal in the system choice and have been applied to organometallic compounds.