Complexes containing multiple bonds between transition metals and group 14 elements with (NHC) ligand have received much interest in theoretical and experimental studies and also play a critical role in a wide range of significant chemical and biological transformations. The present work seeks to characterize, the structural and nature of C → E and Mtriple bondE bonds in [Cp(CO)2Mtriple bondE ← NHC(R)]+ (E = Si, Ge,Sn, Pb; M = Cr, Mo, W; R = H, F, Cl, Br, CH3, Ph, dipp, Si(CH3)3) complexes in the gas phase at M06-2X level nominated among seven DFT methods examined. The nature of C → E and Mtriple bondE bonds in the complexes is analyzed with NBO, AIM, EDA as well as ETS-NOCV. EDA results showed that the contribution of electrostatic interaction (ΔEelstat) in ΔEint of C → E bond is about 43%–59% and is slightly greater than that of orbital interaction (ΔEorb), which ΔEorb with a percentage is in the range of ~36.3%–48.5%. On the other hand, in Mtriple bondE bond, the contribution of orbital interactions (ΔEorb), 49.3%–63.2%, in the total attractive interactions is larger than that of electrostatic interaction (ΔEelstat) 49.3%–63.2%. Also the EDA-NOCV confirms the existence of one σ-orbital and two π-orbitals between E and M atoms in most of the complexes investigated here.
