ISSN 1017-2548(Print)
ISSN 2234-8530(Online)
Volume 26, Number 5
JKCSEZ 26(5)
October 20, 1982 

The effect of π bonds on the calculated dipole moments for square planar and tetrahedral [M(Ⅱ)O2S2] type complexes has been investigated by two different approaches. One is the approximate molecular orbital method based on the assumption that the mixing coefficient CM of the valence basis sets for the central metal ion and the appropriate ligand orbitals is equal for all σ and π bonding molecular orbitals. The other is the more refined calculation based on the semiempirical LCAO-MO method. If σ bonds only are assumed to be formed, the calculated dipole moments for square planar and tetrahedral complexes are lower than those of the experimental values. If the contribution of π bonds to the calculated dipole moments are fully considered, the calculated dipole moments for both square planar and tetrahedral [M(Ⅱ)O2S2] type complexes are higher than the experimental values. However if π bonds are assumed to be delocalzed, the calculated dipole moments for tetrahedral [M(Ⅱ)O2S2] type complexes fall in the range of the experimental values, but those for square planar complexes deviate from the experimental values. These results suggest that [M(Ⅱ)O2S2] type complexes may have the tetrahedral structure in inert solvent solution. This structure is in agreement with the experimental one. The calculated dipole moments for tetrahedral [M(Ⅱ)O2S2] type complexes indicate that the contribution of π bonds to the calculated dipole moments may not be neglected.