A topological analysis of the bonding interaction within the tri-nuclear heterometallic cluster [Mo–Ru–Co(µ3–S)(CO)8(Cp)COOCH3], (Cp = η5-C5H4)

The tri-nuclear heterometallic tetrahedral cluster [Mo–Ru–Co(µ₃–S)(CO)₈(Cp)COOCH₃] (Cp = η⁵-C₅H₄) was studied employing quantum theory of atoms in molecules (QTAIM) to examine bonding interactions, including metal–metal (M–M), metal–sulfur (M–S), metal–carbonyl (M–CO), and metal–cyclopentadienyl (M–Cp) interactions. The electron density of bonding interactions within the cluster has its topological properties calculated based on this theory. Interestingly, the computed local topological characteristics for the Mo–Ru bond show notable distinctions in comparison to the parameters for interactions involving Mo–Co and Ru–Co, since for the latter, critical points and paths were not observed. The distribution of electron density was notably affected by the presence of bridging sulfide ligands in Mo…Co, Ru…Co interactions, much more than in the Mo–Ru bond. The characteristics of the latter bond exhibited attributes typical of interactions between open-shell metals. These features included slightly positive values for ρ_(b) and ∇²ρ_(b), along with small negative values of H_(b)/ρ_(b) approaching zero. Additionally, using the source function (SF) and electron localization function (ELF) methods, more focus has been given to the Mo–Ru bond. The core part, [Mo–Ru–Co(µ₃–S)], was found to have a multicenter 4c–6e interaction. In this core, the three M–S bonds between the metal atoms and the sulfide ligand showed similar topological parameters that were typical of open-shell (covalent) interactions. Substantial π–back donation from CO to M was identified through the execution of δ(M…O_CO) delocalization index calculations.