Theoretical studies including structural investigations, interaction energy, NBO and AIM analysis in some [Bis-NHC(R) → EBr2H2] (E = Si, Sn, (R = H, F, Cl, Br, CH3, CF3) complexes with bis-NHC(R) ligand(bitriazolebase NHC ligand) with five-membered chelate rings at both B3LYP and BP86 level using def2-TZVPP basis set have been reported. Initially, the interaction energy of the complexes was calculated at mentioned levels of theory. Among these compounds, those having electron donating substitutions (H and CH3) have greater interaction energy than those having electron-withdrawing substituents (F, Cl, Br, CF3). In continuation, the amount of charges of C and E atoms in the complexes, hybrid orbital types, Wiberg bond indices and HOMO molecular orbitals were calculated through NBO analysis. Also the AIM analyses were used to detect the presence of bond critical points (BCPs) of C → E bonds in the complexes with the AIM 2000 package. The data show that the C → E bonding interaction in complexes is partly covalent.
