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…… LiH, H₃CH₂C……LiH, (H₃C)₂HC…… LiH, and (H₃C)₃C…… LiH complexes was analyzed in term of the geometries, energies, frequency shifts,stabilization energies, charges, and topological parameters. It is shown that (H₃C)₃C radical with LiH forms the strongest single-electron lithium bond, followed by (H₃C)₂HC 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.