Ab initio study of lithium-bonded complexes with carbene as an electron donor

The complexes H(2)C-LiX (X = H, OH, F, Cl, Br, CN, NC, CH(3), C(2)H(3), C(2)H, NH(2)) have been studied with quantum chemical calculations at the MP2/6-311++G(d,p) level. A new type of lithium bond was proposed, in which the carbene acts as the electron donor. This new type of lithium bond was characterized in view of the geometrical, spectral and energetic parameters. The Li-X bond elongates in all lithium bonded complexes. The Li-X stretch vibration has a red shift in the complexes H(2)C-LiX (X = H, OH, F); however, it exhibits a blue shift in the complexes H(2)C-LiX (X = Cl, Br, CN, NC, CH(3), C(2)H(3), C(2)H, NH(2)). The binding energies are in a range of 16.88-21.13 kcal/mol, indicating that the carbene is a good electron donor in the interaction. The energy decomposition analyses show that the electrostatic contribution is largest, polarization counterpart is followed, and charge transfer is smallest. The effect of substitution and hybridization on this type of lithium bond has also been investigated.