Polymer-supported palladium and rhodium species as hydrogenation catalysts

Effect of size and oxidation state of size-controlled rhodium nanoparticles on the aqueous-phase hydrodechlorination of 4-chlorophenol

“…This issue has been scarcely analyzed in hydrogenation reactions probably due to the general assumption that zero-valent metal species is the only active in that case. Nevertheless, some authors have reported the active role of Rh n+ species in Rh-based catalysts used in the hydrogenation of olefinic and aromatic hydrocarbons [38][39][40][41][42]. To the best of our knowledge, there are no studies on the influence of the oxidation state of Rh-based catalysts on their activity in liquid phase HDC.…”

Synthesis, Characterisation of Polymer-Supported Palladium-2-Methylimidazole Complex Catalyst for the Hydrogenation of Aromatic Nitro Compounds

“…PSPdMeimz-actv did not show any significant changes in the XPS results (Spectrum B). 21,30 Similar observations are reported by Mathew and Mahadevan 24 and Mani et al 31 The XPS spectrum of the recycled catalyst (Spectrum C) revealed that, palladium continues to be in the +2 oxidation state even after recycling the catalyst for six times although the broadening of the peaks observed in spectrum C could be due to the presence of palladium in zero oxidation state formed during usage.…”

“…39 Based on the results obtained, a probable reaction pathway is proposed for the hydrogenation of nitro compounds (Scheme 3). 21 According to the proposed reaction pathway, after oxidative addition of a hydrogen molecule to the catalyst, a nitro group is hydrogenated to produce a hydroxylamine intermediate in two steps which finally undergoes reductive elimination to yield the corresponding amine. Krathy et al have also proposed a similar plausible reaction mechanism for the hydrogenation of aromatic nitro compounds using a polymer supported palladium catalyst where the reaction route is via formation of a hydroxylamine intermediate.…”

“…21 Hydrogenation procedure: All the reactions were carried out using methanol as a solvent at 596 mm Hg hydrogen pressure in a glass reactor. In a typical experiment, the catalyst was added along with the solvent to the reactor which was flushed with hydrogen and then evacuated.…”

Hydrogenation of nitroarenes using polybenzimidazole-supported rhodium catalyst

“…The renewed interest in the field of polymer metal complexes as catalysts is partly due to the development of nitrogen-containing ligands. Polymer supports associated with nitrogen-containing ligands have been studied because of their stability to oxidation [2]. Though the field of polymer metal complexes as catalysts in organic synthesis has remained active over the last four decades, much of the research work has been mainly concentrated to the hydrogenation of alkenes, alkynes and dienes.…”