NaX-encaged Pt carbonyls: reversible substitution of CO ligands by oxygen and ammonia. Evidence for a conservation of the polynuclear Pt skeleton

The carbonylation of platinum tetrammine ions in NaX zeolite to platinum an ionic (Chini) carbonyl complexes ([Pt-3(CO)(6)](n)(2-), n=2), oxidation of these complexes and their recarbonylation were studied using in situ FTIR a nd UV/Vis spectroscopy. The near-surface layers as well as the Pt state wer e examined by XPS, and normalized absorbance of white line of the Pt L-3-ed ge, evaluated from EXAFS experiments, was monitored in the course of the fo rmation and decomposition of anionic Pt carbonyl complexes. It follows that the positive charge of platinum of the starting complex [Pt(NH3)(4)](2+) i n NaX is largely maintained during carbonylation as well as oxidation and r ecarbonylation. From the kinetics of recarbonylation of the oxidized comple x, which is faster than the primary carbonylation by more than one order of magnitude, a preservation of the Pt skeleton of the primary carbonyl is de duced. Mass spectrometric analysis of the gases evolved during decompositio n of the complexes formed by carbonylation, oxidation and recarbonylation, enabled two suggestions to be made: (i) the composition of the oxidized com plex; and (ii) stoichiometries for the conversions in agreement with all ex perimental data.