Abstract: | An ab initio calculation has been carried for the carbene tetrel bonded complexes CH3Y???CH2 (Y = F, CN, NC, and NO2), CH3F???CZ2 (Z = Cl and CH3), XH3F???CF2 (X = C, Si, Ge, and Sn), SiF4???CF2, and XH3F???NHC (N-heterocyclic carbene), where carbene is treated as a Lewis base and XH3Y is a Lewis acid. Formation of the tetrel bond is mainly attributed to charge transfer from the lone pair on the C atom in the carbene toward the σ* X–Y orbital and also the σ* X–H one in the strong tetrel bond. The carbene tetrel bond is strengthened/weakened by the electron-withdrawing group in the tetrel donor/acceptor and enhanced by the methyl group in C(CH3)2. NHC forms a stronger carbene tetrel bond in XH3F???NHC (X = Si, Ge, and Sn) where it exceeds that of the majority of H-bonds. Interestingly, the tetrel bond becomes stronger in the order of X = C < Ge < Sn < Si in XH3F???NHC and the largest interaction energy occurs in SiH3F???NHC, amounting to ?103 kJ/mol. The carbene tetrel bond can be strengthened by cooperative effect with the N???M interaction in trimers H2C???CH3CN???M (M = CH3CN, HCN, ICN, SbH2F, LiCN, and BeH2) and has doubled in H2C???CH3CN???BeH2. |