Electronic structure of the PdCl₄²⁻ and PtCl₄²⁻ions

The electronic spectra of PdCl₄²⁻ and PtCl₄²⁻ are studied by quantum-chemical methods with the ultimate object being to understand the differences in reactivity for Pt(II) and Pd(II) complexes. Nonrelativistic ab initio UHF, DV - Xα, and MSXα methods give very similar assignments of the spectra for PdCl₄²⁻. The d–d spectrum for PtCl₄²⁻, which is very different from the d–d spectrum of PdCl₄²⁻, agrees qualitatively with the spectra obtained using the relativistic extended-Hückel (REX) and Dirac–Slater (DS) methods. Although the latter two methods disagree somewhat in the interpretation of the high intensity bands in PtCl₄²⁻, it appears reasonable to interpret at least one of the lines as a 5d → 6p transition.