Topological analysis of the bonding in [Ru5(μ4-C2)L(CO)13] and [Ru4(μ4-C2)L(CO)10] complexes (L = (μ-SMe)(μ-PPh2)2)

The nature of metal-metal and metal-carbon bonding interactions within the penta- and tetra-ruthenium acetylide complexes [Ru5(μ4-C2)L(CO)13] (1) and [Ru4(μ4-C2)L(CO)10] (2) respectively are investigated using the present topological theories of the chemical bond: AIM and ELF. The electron density analysis within the framework of Atoms in Molecules (AIM) indicates that, in the first complex, only one bond path exists between the Ru4 and Ru5 metal atoms, whereas there is no direct bonding between ruthenium atoms in the second complex. On the other hand, the ELF analysis reveals that in both complexes, all Ru-C bonds belong to closed-shell type interactions and leads to the conclusion that the Ru-Ru bond is predominantly covalent. Moreover, the presence of trisynaptic basins in the first complex points out a three-center bond connecting ruthenium atoms.