Geometry of Pt(IV) in H 2PtCl 6 aqueous solution: An X-ray absorption spectroscopic investigation

Abstract

The noble metal ions play an important role in many chemical reactions, but at the present time they represent also potentially new environmental contaminants. There is relatively little information available to adequately assess the potential health hazards, so that to evaluate the potential hazards and identify the necessary actions to reduce the risks associated with exposure to these metals and their compounds it is important to understand the local structure around noble metal ions. In this contribution, the local coordination around platinum (IV) ions e.g., Pt 4+ in aqueous solution, has been investigated by using X-ray absorption spectroscopy (XAS). X-ray absorption near-edge spectra (XANES) of both [PtCl 6] 2− and [PtCl 4(OH) 2] 2− in an aqueous solution have been calculated using FEFF8.2 and both are characterized by an octahedral geometry. From these calculations, we may also assign a characteristic post-edge feature to a contribution of Cl d-states. From the EXAFS analysis we also determined the corresponding Pt bond distances, e.g., 2.33 Å for the Pt–Cl distance and 2.03 Å for the Pt–O distance in these aqueous solutions. The same analysis provides evidence that the peaks in the Fourier transform at about 4.0 Å are due to multiple scattering collinear Cl–Pt–Cl contributions.