The two optimized stable lithium bonding and hydrogen bonding co-existing complexes, CH₃SLi…CH₃SH, were found on the potential energy surface of CH₃SLi＋CH₃SH. Red shift of the S(5)—Li(6) and blue shift of C(8)—H(10) stretching vibrational frequencies were obtained simultaneously via frequency analysis. The BSSE-corrected interaction energies in complex ? obtained by using B3LYP/6-311＋＋G**, MP2/6-311＋＋G** and MP2/AUG-CC-PVDZ were －58.99, －57.87 and －62.89 kJ•mol^－1, respectively. From the natural bond orbital (NBO) analysis, The charge transfer interactions between the related orbits, electron density redistributions and the essential of the correlative bond length changes in the complexes were detailedly discussed. The topological properties of the hydrogen bond and lithium bond structures were also investigated by the atoms-in-molecules (AIM) theory. In addition, the solvent effects were studied using the polarized continuum model (PCM). The results showed that the interaction energy would increase in the presence of solvents, and the solvents could evidently affect the geometric structure and vibration frequency of the lithium bond in CH₃SLi…CH₃SH, but not obviously the frequency of the hydrogen bond.

Key words: CH₃SLi, co-existing of lithium bond and hydrogen bond, natural bond orbital theory, atoms-in-molecules theory, solvent effect