Structural, bonding and redox properties of 34-electron bimetallic complexes and their oxidized 32- and 33-electron and reduced 35- and 36-electron derivatives containing the indenyl fused π-system: A DFT overview

Abstract

DFT calculations with the BP86, OPBE and hybrid B3LYP* functionals have been performed on a series of homo- and heterobimetallic compounds of the type [(RuCp)2(Ind)]+, [(CoCb)2(Ind)]+ and [(RuCp)(CoCb)(Ind)]+ (Ind = indenyl, Cp = cyclopentadienyl and Cb = cyclobutadiene) of 34-TNE (Total number of electrons), their oxidized 32- and 33-TNEs and their reduced 35- and 36-TNEs species. Depending on the ancillary Cp or Cb ligand to the metal, the electronic and molecular structures and the metal–metal bonding of this family of compounds have been analyzed. The syn and anti-configurations are possible for the studied binuclear complexes, which are related to the metal nature, where mostly steric constraints of the Cp or the Cb ligand appear to control its spatial disposition favouring the anti configuration, despite its electronic deficiency for the 32- and 33-TNEs species. The flexibility of the indenyl ligand, which is related to the metal hapticity, favors the possibility of existence of several syn and anti isomers of close energies. This study showed quite similar behaviours of the (RuCp)+ and (CoCb)+ fragments of 12-electrons regarding their change or their permutation. The current study shows the ease of reduction with regard to oxidation, particularly that by the loss of two electrons. The used three functionals gave comparable tendencies of the stability sequences between isomers, favouring the low-spin structures, and provided comparable findings regarding the low-spin/high-spin energy splittings.