Non-additivity of Methyl Group in the Single-electron Lithium Bond of H3C•••Li-H Complex

The non-additivity of the methyl groups in the single-electron lithium bond was investigated using ab initio calculations at the B3LYP/6-311++G** and UMP2/6-311++G** levels. The strength of the interaction in the H3C center dot center dot center dot LiH, H3CH2C center dot center dot center dot LiH, (H3C)(2)HC center dot center dot center dot LiH,and (H3C)(3)C center dot center dot center dot LiH complexes was analyzed in term of the geometries, energies, frequency shifts, stabilization energies, charges, and topological parameters. It is shown that (H3C)(3)C radical with LiH forms the strongest single-electron lithium bond, followed by (H3C)(2)HC radical, then H3CH2C radical, and H3C radical forms the weakest single-electron lithium bond. A positive non-additivity is present among methyl groups. Natural bond orbital and atoms in molecules analyses were used to estimate such conclusions. Furthermore, there are few linear/nonlinear relationships in the system and the interaction mode of single-electron Li-bond is different from the single-electron H-bond and single-electron halogen bond.