Abstract: Metal carbene cations, found in recent ten years, is a class of unstable intermediates with a high activity. In this paper, with CH₂Li⁺as a model compound, we first investigted the relative stabilization energies and molecular orbitals of substituted lithium carbene cations by ab initio method. The studies show that the substituents with π donation have the biggest stabilization because they can form a two electron-multicentre conjugated orbital with carbene carbon and lithium in their planar configurations. In contrast, their stabilization energies are less in perpendicular one. The π donation plays a leading role in the substituents with both π donation and σ induction. Then the substituents with only σ inductive effets have destabilization. The most of LUMO of lithium carbene cations are conjugated molecular orbitals formed by empty p^zof carbene carbon, lithium and substltuents, and the carbene carbon is the major consistent. Their energy levels all are negative values, so they can be considered with a high electrophilic activity and the acting centre should be on the carbene carbon.

Key words: Ab initio, Lithium carbene cation, Stabilization energy