A quantum molecular study on the coordination way in the square-planar complexes of Ni(II), Pd(II) and Pt(II) with a heterocyclic (N, S) ligand

The purpose of this paper is the investigation of the coordination way of a ligand in the dibenzofuran series (namely 3-thio-benzoylamino-dibenzofuran, TBADBF) to Ni(II), Pd(II) and Pt(II) ions based-on spectral analysis. The absorption maxima occurring in the electronic spectra of the free heterocyclic ligand TBADBF and of the [M(TBADBF)Cl-2] square-planar complexes, where M = Ni(II), Pd(II) and Pt(II) have been interpreted using the EHT-MO approach. It has been shown that the electronic transitions in the spectrum of TBADBF are due to an electron transfer involving electron]one pairs of sulfur and oxygen. Some of them are shifted toward higher wavenumbers in the spectra of the complexes as a consequence of the coordination. The band shifts are caused either by the mixing with d-metal orbitals or by the energy lowering of the MO levels caused by the coordination of the donor atoms to the transition metal ions.