A theoretical study is reported on the strength and nature of metalligand bond in some dianionic metal-bis(dithiolate) complexes [ML2] 2– (M=Ni(II), Pd(II), Pt(II); L = S2C2H2 2- (edt2‒), S2C2Me2 2- (dmedt2‒), S2C2(CN)2 2- (mnt2‒)). Firstly, the geometries of all complexes were optimized at the BP86 and M06 levels of theory using the def2-TZVP basis set. Then the metal-dithiolate and metal(dithiolate)-dithiolate interaction energies, the deformation energies of metal and dithiolate ions as well as the total interaction and stabilization energies of the complexes were calculated and compared. In continuation, an energy decomposition analysis (EDA) was performed to study the nature of metal-bis(dithiloate) bonds in these complexes. The results showed that among the metal complexes studied here, the Pt complexes have the largest values of interaction and stabilization energies. On the other hand, in the case of all three metal ions, the values of total interaction energies and also stabilization energies of [M(edt)2] 2– and [M(dmedt)2] 2– complexes are similar or close together and both are larger than those for [M(mnt)2] 2– complexes. The analysis of metal-(bis)dithiolate bonds showed that the orbital interactions are mainly Ni←Lσ interactions and have considerably less contribution to the total attractive interactions compared to electrostatic interactions.
