ИСТИНА

The idea on metal-containing nonbenzenoid aromatic systems was born in INEOS RAS by Mark Vol’pin. Namely, a complex Cp2Ti(PhC2Ph) not containing additional ligands was synthesized by his group in 1982.1 The three-membered metallacycle of this complex was considered as aromatic, its -electron delocalizes system involving two -electrons of carbon atoms and the vacant orbital of the Cp2Ti species . In this study, vibrational spectra of three types (I-III) of aromatic compounds, in which a metal atom participates in cyclic -electron delocalization, will be presented and discussed. These are two-electron metallacyclopropenes (I) as well as six-electron metallacyclocumelenes (II)2 and Arduengo type N-heterocyclic unsaturated compounds (III): silylene 3 and germylene4 and stannylenes5 Aromaticity of compounds of these types will be estimated using different modern criteria, both experimental and theoretical (calculations of NICS and ISE).