Peculiarities of multiple Cr-Cr bonding. Insights from the analysis of domain-averaged Fermi holes.

The recently proposed methodology known as the analysis of domain-averaged Fermi holes was applied to reveal the nature and peculiarity of metal-metal bonding interactions in two recently reported complexes with an ultrashort, presumably quintuple Cr-Cr bond. The results of the analysis straightforwardly confirm the considerable reduction of the Cr-Cr bond order resulting from depletion of the electron density from one of the electron pairs involved in the metal-metal bonding. Because of this depletion, the Cr-Cr bond can be best classified as the effective quadruple bond, with the contribution of another weak component corresponding to the antiferromagnetic coupling of electrons in one of the available delta-electron pairs.