A Comparative Topological Study of Different Metal-Metal and Metal-Ligand Interactions in Polynuclear Organometallic Clusters

The existence and characterization of a bond between the Zn atoms in the recently synthesized complex [Zn-2(eta(5)-C5Me5)(2)] (I), as well as between two of the three Ru atoms in [Ru-3(mu-H)(2)(mu(3)-MeImCH)(CO)(9)] (Me(2)Im=1,3-dimethylimidazolin-2-ylidene) (II), are firmly based on low temperature X-ray synchrotron diffraction experiments. The multipolar refinement of the experimental electron densities and their topological analyses by means of the Atoms in Molecules (AIM) theory reveal the details of the Zn-Zn and Ru-Ru bonds, such as their open-shell intermediate character. The results are consistent with a typical metal-metal single sigma bond for the former, whereas a delocalized kind of bond involving 5c-6c is present in the latter. In addition, experimental results are compared with theoretical ab initio calculations of the DFT (density functional theory) and MP2 (Moller-Plesset perturbation theory) electron densities, giving a coherent view of the bonding in both complexes. Many other topological properties of both compounds are also studied, in particular the different metal-ligand interactions.