Thermal decomposition of (NH₄)₂[PtCl₆] – an in situ X-ray absorption spectroscopy study

Abstract

The thermal decomposition of di-ammonium hexachloroplatinate ((NH4)2[PtCI6]) to metallic platinum has been investigated by time-resolved in situ XAS measurements at the CI K-and Pt Lmedge. Spectra at the CI K-edge were recorded utilizing an energy dispersive monochromator (EDM), while the Pt Lm-edge spectra were recorded using a double crystal monochromator. By analysing the energy shift of the CI K-edge a reaction intermediate has been observed at about 310°C. Fingerprinting arguments indicate that this intermediate could be cis-platin or some other platinum amine complex.

Microsecond time-resolved energy-dispersive EXAFS measurement and its application to film the thermolysis of (NH4)2[PtCl6]

“…Previous EDE study at the Cl K-edge and Pt L 3 edge also provided information about the starting point of the reaction and proposed the structure of the intermediate. However, due to the limited time resolution of 10 seconds and only XANES signals were measured and compared with the reference spectrum measured at ambient temperature, no conclusive results could be obtained10.…”

“…The time domain for chemically or thermally driven reactions could vary from hours to ultrafast regime when atomic or electronic motions are the dominant effect. Representatives are catalytic process7, formation of metal nanoparticles89 and thermolysis dynamics1011 and such reactions are well suited for time-resolved EDE studies.…”

“…(NH 4 ) 2 [PtCl 6 ] has been shown to be a good precursor to obtain metallic Pt through thermolysis due to its low decomposition temperature12. The thermolysis mechanism has been investigated extensively13141516 including time-resolved EDE at the Cl K-edge and Pt L 3 edge with a time resolution of 10 seconds10, and several intermediates such as PtCl 4 14, PtCl 6 15 and cis-PtCl 2 (NH 3 ) 2 10, have been proposed. However, despite these numerous studies1013141516, direct structural evidence for the intermediate and the reaction dynamics have been lacking.…”

Equations of state of rhodium, iridium and their alloys up to 70 GPa

“…trans-and/or cis-[Pt(NH3)2Cl2] and polymeric {OsCl4}n were proposed as key intermediates. However, several previous ex situ investigations of (NH4)2[PtCl6] did not give much insight into its thermal decomposition in H2 flow while the most data were obtained in an inert gas atmosphere [34][35][36][37][38].…”

Thermal decomposition of (NH4)2[PdCl6] studied by in situ X-ray absorption spectroscopy

“…First indications of a more complex reaction mechanism, probably including intermediates such as Pd(NH3)2Cl2 (T decomp 290 AE C) and ligand exchange reactions correlated with evolved gases (e. g. HCl) were obtained in more extensive studies (Möller et al 1994). As shown in a previous time-resolved X-ray absorption study (Rumpf et al 1999), XANES is a promising tool to detect new ligand exchange pathways in inorganic solids. A more fundamental understanding of the internal redox-reaction in the ammonium hexachlorometallates seems to be possible and is subject of this investigation.…”