The electronic structure calculations have been carried out on two binuclear complexes Mo~2S~2(μ-S)~2(dtp)~2 (1), W~2S~2(μ-S)~2(dtp)~2 (2) and their core fragments Mo~2S~4^2^+ (3), W~2S~4^2^+ (4). The calculations were accomplished by using an ab initio quantum chemical method with relativistic effective core potentials. By the analysis of the calculated canonical molecular orbitals and localized molcular orbitals as well as the Mulliken populations, the bonding and electronic characteristics of these complexes have been studied. By virtue of the Generalized Purtubation theory, there activities and mechanism of M~2S~4^2^+ complexes in forming the Cubane-like clusters via [2+2] fasion and the incomplete Cubane-type clusters via [2+1] fashion have been discussed. It is found that there exist three "Reactive Sites" and three "Reactive Regions" with higher electronic densities.

Key words: ACTIVITY, AB INITIO CALCULATION, ASSEMBLING, MOLECULAR ORBITAL METHOD, LOCALIZATION, ELEMENTS