• Journal of the Korean Chemical Society
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• v.26 no.5
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• pp.265-273
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• 1982

The effect of ${\pi}$ bonds on the calculated dipole moments for square planar and tetrahedral [M(II)$O_2S_2$]] 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 ${\sigma}$ and ${\pi}$ bonding molecular orbitals. The other is the more refined calculation based on the semiempirical LCAO-MO method. If ${\sigma}$ 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 ${\pi}$ bonds to the calculated dipole moments are fully considered, the calculated dipole moments for both square planar and tetrahedral [M(II)$O_2S_2$]] type complexes are higher than the experimental values. However if ${\pi}$ bonds are assumed to be delocalzed, the calculated dipole moments for tetrahedral [M(II$O_2S_2$]] 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)$O_2S_2$]] 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)$O_2S_2$]] type complexes indicate that the contribution of ${\pi}$ bonds to the calculated dipole moments may not be neglected.

• Journal of the Korean Chemical Society
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• v.34 no.1
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• pp.37-43
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• 1990

An effect of the spin-orbit coupling interaction of ligand orbitals and the intermixing │3d 〉and│4p > transition metal atomic orbitals on the ground state for a 3$d^9$ system in a strong crystal field of tetragonally distorted tetrahedral symmetry that belongs to the $D_{2d}$ point group has been investigated in this work, applying the degenerate perturbation theory. An LCAO-MO analysis in terms of the known energies of the d-d transitions for the tetragonally distorted $CuCl_4^{2-}$ ion in a single crystal of$Cs_2CuCl_4$shows that the covalent mixing of Cu 3d and ligand Cl 3p orbitals decreases dramatically with increasing Cu 4p contribution. The extent of effect on the energy level splitting for the ground state by the spin-orbit coupling interaction of ligand orbitals decreases significantly in orderTEX>$\Gamma_7(E)\;\to\;\Gamma_6(E)\; >\;\Gamma_7(B_2)\;\to\;\Gamma_6(E)\; >\;\Gamma_7(B_2)\;\to\;\Gamma_7(E)$.