The geometric and electronic structures of quadruply bonded metal dinuclear compounds M₂Cl₄(PMe₃)₄ (M＝Cr, Mo, W) and Mo₂X₄(PMe₃)₄ (X＝F, Cl, Br, I) have been investigated by means of density functional theory method with TZ2P-STO basis sets. It was shown that the title compounds can be accurately predicted by DFT included ZORA relativistic correction. The present calculations show that the ground state configurations of all quadruply bonded dinuclear compounds are σ²π⁴δ², and the energetic ordering of metal-metal orbitals is π_lig＜π_d/σ_d＜δ_d＜δ_d*. Although the orbital energy levels changed with different metal atoms and haloid ligands, the energetic ordering of orbitals is not exchanged. The electronic excitation energies of M₂X₄(PMe₃)₄ have been studied employing the time-dependent density functional theory (TD-DFT). The effects of metal atoms, haloid ligands, and relativistic effect on these compounds were examined. The calculated transition energies are in fairly good agreement with experimental values and the spectral shifts trends predicted by TD-DFT compare well with available experimental data.

Key words: quadruply bonded metal dinuclear compound, density functional theory, electronic structure, electronic spectra