The Atoms in Molecules (AIM) analysis for triosmium cluster, which contains trihydridede, carbon, carbonyl and 2-methylbenzothiazolide ligands, [Os 3 (µ-H) 3 (µ 3 -ɳ 2 -CC 7 H 3 (2-CH 3 )NS)(CO) 8 ] is reported. Bonding features in this cluster has been analyzed based on QTAIM ("Quantum Theory of Atoms in Molecules") in this work. The topological indices derived from electron density of relevant interactions in triosmium compound have been studied. The major interesting point of the AIM analyses is that the core of part (Os 3 H 3 ) reveals the absence of any critical points and bond paths connecting any pairs of Os metal atoms. However, bond critical points with their bond paths occurring between all Os-H interactions were observed. For the bridged core part (Os 3 H 3 ) , a 6c-6e multicenter interaction is proposed. The topological parameters computed for the bridging 2-methylbenzothiazolide ligand interactions indicate that all of these interactions are typical related to the covalent bonds with a contribution of some double-bond character.

The topological features of the Triosmium cluster [Os3(CO)9(µ-ɳ 2 -C7H3(2-CH3)NS)(µ-CH2)CH3], containing carbonyl and 2methylbenzothiazol ide ligands, has been examined using density functional theory (DFT) and QTAIM-based "Quantum Theory Atoms in Molecules". The topological parameters of the electron density in the cluster have been calculated. The QTAIM analysis of the topological features demonstrated that the core part Os3C1 in the cluster is significantly absence a bond critical point and its bond path between Os1-Os3. Whereas, the analysis Os1-Os2 and Os2-Os3 interactions revealed the occurrence of bond paths and bond critical points between these atoms. A multicentre 4c-5e interaction for the Os3C1 core has been proposed. The topological parameters calculation show that the interactions in the bridging 2-methylbenzothiazolide Ligand are a typical for shared shell with the existence of some double-bond character.