Electronic structure of the PdCl 4 2− and PtCl 4 2− ions

The electronic spectra of PdCl 4 2− and PtCl 4 2− 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 MS Xα methods give very similar assignments of the spectra for PdCl 4 2− . The d – d spectrum for PtCl 4 2− , which is very different from the d – d spectrum of PdCl 4 2− , 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 PtCl 4 2− , it appears reasonable to interpret at least one of the lines as a 5 d → 6 p transition.