Analysis of the aromaticity of five-membered heterometallacycles containing Os, Ru, Rh, and Ir

We study the molecular structure and aromaticity in a series of experimental and new in silico designed five-membered heterometallacycles with general formula M(XC3H3)(PH3)2, where M = OsH3, OsCl3, OsCl2, RuCl2, RhCl2 or IrCl2 and X = NH, O, S, CH-, or CH+. The electron delocalization of the five-membered rings in these complexes is analyzed using the induced magnetic field, NICS, and MCI descriptors of aromaticity. Our results indicate that the five-membered rings in all complexes with X = NH, O, S, and CH- have a low aromatic character denoted by nonintense diatropic behavior and low MCI values. Five-membered rings in complexes with X = CH+ are clearly paratropic and antiaromatic according to MCI values with the exception of M = OsCl 3. The reason for this exception is discussedThe authors are grateful to the Research Executive Agency of the European Research Council for financial support through the PIRSES-GA-2009-247671 project of the FP7-PEOPLE-2009-IRSES program. R.I. thanks the same organization for the postdoctoral fellowship received from the same project. M.S. and J.P. are grateful to the Ministerio de Ciencia e Innovacion (MICINN, project numbers CTQ2011-23156/BQU and CTQ2011-25086), the Generalitat de Catalunya (project numbers 2009SGR637 and 2009SGR528, Xarxa de Referencia en Quimica Teorica i Computacional, and ICREA Academia 2009 prize for M.S.), and the FEDER fund (European Fund for Regional Development) for the grant UNGI08-4E-003. The Centre de Serveis Cientifics i Academics de Catalunya (CESCA) is acknowledged for a generous allocation of computer tim