Basicity of N-Heterocyclic carbene and its Main-Group Analogues

In this study, the N-heterocyclic carbene (NHC) imidazole-2-ylidene and its analogues species of group13-15 are considered to study their basicity. Proton affinity (PA) and gas phase basicity (GPB) of each species are calculated at the B3LYP/def2-TZVP level of theory. It is found that PA and GPB decrease down a group and along a period. The acidity of the conjugate acid (pKa) of the NHC analogues are computed in solution giving comparable result to the gas phase ones. The binding energies (ΔEbind) of the adduct formation of the carbene analogues with BH3, BF3 and BCl3 are computed at the same level of theory and follows the same trend. Further interaction energies (ΔEint) of the borane adduct are calculated using localized molecular orbital energy decomposition analysis (LMO-EDA) showing electrostatic (ΔEel) as the dominant factor. Donor-acceptor interaction has been justified from Charge decomposition and Natural bond orbital (NBO) analysis.—————————————————————————————————————Graphical abstract

Source: Computational and Theoretical Chemistry - August 15, 2019 Category: Chemistry Source Type: research