Organolithiums reactivity: geometric and energetic characterization of the lithium bond, substituents effect and cooperativity

Abstract

Lithium bonding has recently attracted increasing attention as a directional noncovalent interaction analogous to hydrogen bonding, with potential implications in organolithium chemistry and lithiumbased energy technologies. In the present study, the nature, strength, and substituent effects of lithium bonds formed by organolithium compounds were investigated using density functional theory calculations at the ωB97XD/6-311++G(d,p) level of theory. A series of CH₂XLi molecules (X = H, F, Cl, Br, CH₃) interacting with water and ammonia were analyzed to characterize the C-Li⋯O and C-Li⋯N lithium bonds and to evaluate possible cooperativity with hydrogen bonding. Geometric, energetic, and electronic analyses reveal that the Li⋯N complexes are generally more stable than the Li⋯O counterparts, with binding energies ranging from 77-91 kJ mol⁻¹ for Li⋯N and 66-83 kJ mol⁻¹ for Li⋯O interactions. In Li⋯O complexes containing halogen substituents, additional O-H⋯X hydrogen bonds lead to cooperative stabilization and cyclic structures. Natural Bond Orbital (NBO) analysis shows that classical donor-acceptor charge transfer from LP(N/O) → σ*(C-Li) contributes modestly to stabilization, whereas a stronger LP(N/O) → LP*(Li) interaction involving the vacant p lithium orbital is observed. Molecular electrostatic potential maps reveal a pronounced σ-hole along the extension of the C-Li bond, supporting the directional nature of lithium bonding. The combined analyses suggest that lithium bonding in organolithium complexes exhibits a hybrid character, dominated by σ-hole electrostatic interactions but supplemented by orbital contributions resembling π-hole interactions. These findings provide new insights into the fundamental nature of lithium bonding and may contribute to a better understanding of lithium-containing systems in organic synthesis, catalysis, and lithium battery chemistry.