Analysis of the Aromaticity of Five-Membered HeterometallacyclesContaining Os, Ru, Rh, and Ir.

We study the molecular structureand aromaticity in a series ofexperimental and new in silico designed five-membered heterometallacycleswith general formula M(XC3H3)(PH3)2, where M = OsH3, OsCl3, OsCl2, RuCl2, RhCl2or IrCl2andX = NH, O, S, CH–, or CH+. The electrondelocalization of the five-membered rings in these complexes is analyzedusing the induced magnetic field, NICS, and MCI descriptors of aromaticity.Our results indicate that the five-membered rings in all complexeswith X = NH, O, S, and CH–have a low aromatic characterdenoted by nonintense diatropic behavior and low MCI values. Five-memberedrings in complexes with X = CH+are clearly paratropicand antiaromatic according to MCI values with the exception of M =OsCl3. The reason for this exception is discussed. [ABSTRACT FROM AUTHOR]